Performance Analysis of MIMO-NOMA Systems Based on Dynamic User Pairing Scheme

Multiple input multiple output (MIMO) structure can enhance the total capacity of the modern communication systems without using consuming excess power or bandwidth. Non-orthogonal multiple access (NOMA) configuration is a good nominee to accommodate with MIMO structure to fulfil the demands to extra user data rates and enriched spectral efficiencies. The dynamic uniform channel gain difference (DUCGD) user pairing technique plays an important role to maximize the capacity of all the paired and served users. The DUCGD is implemented by calculating the channel gain of every prospected user and sorting it in descending order to pair ones with the highest difference in channel gains to be functioned together. In this paper, the performance analysis of MIMO-NOMA systems by means of DUCGD is presented. The numerical analysis showed that, the increase of the number of users leads to an increase in the systems’ gain and the total achieved sum rates. This improvement is shown to be due to using DUCGD and an increased number of transmitting and receiving antennas, jointly.

Introduction
User pairing in non-orthogonal multiple access (NOMA) enables more than one user to share their resources using superposition coding (SC) in the power domain. Where each user can take a proportion of the transmitted power according to a sharing factor called power coefficient [1], it plays a promising procedure in the next mobile generation due to its higher spectral capacities [2] [3]. The uniform channel gain difference (UCGD) pairing technique depends on fixed power coefficient and neglects channel gain differences between users. This UCGD maximizes the capacity of the selected paired users [4], consequently channel gain calculated at every frame to decide which users can be paired to obtain maximize the capacity of all paired and served users.
In 5G wireless communication system, its' main target is getting the largest number of users and the fastest data speeds with good bit-error-rates (BER). The multiple-input multiple-output (MIMO)-NOMA has been a hopeful technique to fulfil this targets due to its superior spectral efficiency (SE) and higher capacities without consuming excess power or bandwidth [5] [6]. To utilize the user pairing (UP) manner in MIMO-NOMA procedure, the base station (BS) supposed to pick which users thought to be paired to share the similar band in advance, since the clustered users should have a major variance between there channel gains to raise the systems' whole rate [2].
In [7], The influence of the pairing techniques on the feasible sum rates of NOMA has been practiced with stationary power allocation but not a dynamic one. A new algorithm advances to acquire extraordinary properties of the interference signal cancellation at NOMA method studied in [8]. In [9], traditional NOMA apportions more power to the served users with low channel gains to escalate their throughput. The closed-form globally-optimal solution in [10] acquired to fix user pairing and power allocation problem with least rate compel for each user in NOMA scheme. In [11], an extra consideration about UP in the cognitive radio applications inspired from NOMA scheme is presented, where the achievable sum rate could be amplified with a costumed matched distributed algorithm. In [12], a user pairing and pair scheduling for massive MIMO-NOMA schemes expanded the throughput by alleviating the inter-pair interference. The issue of ergodic capacity expansion MIMO-NOMA systems with the Rayleigh fading channel is illustrated in [13], and submit both optimal and suboptimal power allocation schedule to settle this optimization problem. Finally, in [14] the new algorithm for power allocation can improve the achieved overall rate of NOMA method.
In this paper, the performance of different types of MIMO-NOMA pairing schemes were compared by calculating their total sum rate at various cases. The study considered a constant users' number and utilizing 2, 4 and 8 transmitting (Tx) and receiving (Rx) antennas. When DUCGD pairing scheme is utilized, the system resulted highest sum rates with increasing of the number of utilized antennas. As well as, the cumulative distribution function (CDF) investigation proved that the probability of higher total sum rate is greater than the probability of lower ones at various user's number in the same mentioned case. When the number of utilized MIMO antennas is fixed, the gain due to NOMA pairing schemes is increased with the increase of number of users. Due to the benefits of DUCGD over conventional schemes, it suggested to utilize it in MIMO-NOMA systems with increased numbers of users and massive numbers of antennas.
This paper is structured as follows. Second section portrayed user pairing in MIMO-NOMA. Third section explains the considered MIMO-NOMA system model. Furthermore, the results of the simulation and considerations are executed in the fourth Section. Finally, the conclusion is presented in fifth section.

User pairing in NOMA
SC used in the NOMA systems to make numerous users sharing the mutual bandwidth with their information by giving each user a part of transmitting power. This process makes these users in a pair. The channel gains are a way to treat M users selected randomly in a cell 1 where m h implying the Rayleigh fading channel gain between the BS and the coordinated th m user and their allocated powers are in the arrangement 1 , respectively. where  represents the transmit signal to noise ratio (SNR). The total achievable data rate of NOMA is calculated by (3) The th m user can achieve m R permanently. The sum data rate of an orthogonal MA technique is calculated by (4) To anatomize DCU pairing in NOMA, the discussion is restricted to use two users per pair for simplification. Combining users from the cell centre (high CQI) and cell edge (low CQI) into pairs can achieve ultimate channel gain difference between them. The difference in the channel gain of the cell mid users (CMU) is very less if there are paired with each other. The likelihood that superior capacity of these pairs are lower than MA systems is studied in [7]. The nearness in the channel gains and the power coefficients lead to the increasing of noise at lower channel gain users and the deficiencies of SIC at higher channel gain users which are the main reasons of decreasing the capacity in these CMU pairs [15]. Therefore, if the CMU are paired, their sum rates could be lower than MA and the small mobility made the difference in gain neglected. For those reasons, dynamic uniform channel gain difference (DUCGD) pairing is used to accommodate the CMU by preserving comparatively DUCGD between paired users of all pairs as shown in figure 1. b. The user's channel gains which existing in the cell are splitted into two combinations by median h , pursued by inter-group paring in such a way that CMU are well adapted.
Consider the channel gains of L users in a cell as    L h  as in (5). The DUCGD can find the users of CMU which can be paired with either the higher channel gain or the lower channel gain users. This implies each time the minimum gain users of each gathering are matched with others, trailed by blending next least clients of the two clusters, etc. The power allocation factor in this method depends on the channel gain as in (6) In this technique, the submitted procedure solved the main reasons of decreasing the capacity in these CMU pairs which discussed previously, that way allowing them to take advantage of MIMO-NOMA pairing techniques by getting higher capacity gain and minimizing the SIC performance issue.

System model
A solitary circular cell MIMO-NOMA broadcast is Imposed scheme with radius R, the BS at the centre serving a total M user [12]. In which every user of the cell has K receiving antennas and BS is supplied with N antennas. Here, M > 2N is expected to confirm that 2N users are chosen from all the users and everyone should have the same frequency band with its paired client. The user terminal (UT) should have a number of antennas greater than that of BS as the required system. The accurate channel state information's (CSIs) of all the users are known for both UTs and BS [12].
The Tx signal for the paired users have with SC at the BS can be shown as (7)  Following the essential rule of NOMA [2], the power allocation coefficients Can be customized as Within a pair, fragmentary transmit power was utilized to characterize 1,i a and 2,i a , so that, the principal user can recognize the subsequent user's signal effectively, and afterward subtracts it from the superposition coded signal by means of the SIC procedure [2]. the sum rate of MIMO-NOMA schemes can be indicated as (9) As a correlation, the sum rate of traditional MIMO-OMA frameworks can be expressed as (10)

Conclusion
In this paper a new proposed method for improving the gain of MIMO-NOMA pairing techniques has been used. The simulation results of this new method has been showed that the gain duo to the DUCGD pairing scheme is improved with the increase of Tx and Rx antennas. It is noticed that higher SNR leads to decrease the gain of DUCGD pairing system. The probability of achieving higher total sum rates in accordance with employing the DUCGD is superior by increasing number of transmitted and received antennas, also the spectral efficiency enhancing proportional to number of users especially for lower values of the SNR. The previous analysis proved that DUCGD suggested to utilize in MIMO-NOMA schemes with increased numbers of users or antennas. Through this paper, it was found that it is possible to use the DUCGD pairing techniques to take the advantage of the features which provided in 5G techniques.


Spirituality as a Predictor of Psychological Well-Being: An Explanatory Mechanism of Religiosity and Sustainable Consumption

: This paper aims to investigate the impact of spirituality on the psychological well-being of the consumers involved in reusing as sustainable consumption behavior (SCB). In addition to this, the study also investigates the mediating e ﬀ ect of reusing as SCB between spirituality and psychological well-being. The moderating e ﬀ ect of religiosity has also been taken into account while studying the relationship between spirituality and reusing. A survey was conducted to collect the data from clothing industry consumers using a structured questionnaire and employing a convenience sampling approach. PLS-SEM was used to analyze the useable data of 286 respondents. Results validate that spirituality has a positive and signiﬁcant e ﬀ ect on psychological well-being. Further, reusing (SCB) was found to be a signiﬁcant mediator, also the moderating e ﬀ ect of religiosity on the relationship between spirituality and reusing was signiﬁcant and high. This study contributes to the existing literature by concentrating on predictors that undermine psychological well-being. To the best of the authors’ knowledge, this is one of the early studies to contribute to the literature by investigating the impact of spirituality on consumer psychological well-being speciﬁcally reusing (SCB) as a mediator between the two constructs. Further, it also investigated the moderating impact of religiosity on the relationship between spirituality and reusing. Research ﬁndings have implications for researchers, policymakers, marketers, ecologists, social activists, and practitioners. For research students, such contribution will bring a new avenue to consider further research. Managers will ﬁnd help to control such factors which induce reusing and increase psychological well-being.

Introduction
Sustainable consumption behavior (SCB) has gained its popularity in the field of business, policy-making, and in academic research (Romani et al. 2016;Garvey and Bolton 2017;Wang et al. 2017a). SCB is a very broad area and diverse definitions have emerged over the past few decades. Generally, it is used to explain the activities that lead to enhance life quality, fulfill unmet needs, waste reduction, and refining resource efficiency (Bridges and Wilhelm 2008). The scarcity of studies identifying and explaining the relationships involved in SCB has compelled the researchers to focus on this area.
Individual usage behavior in life cycle of the products specific to sustainable consumption was conceptualized by Geng et al. (2017). Before this conceptualization of SCB, as a multifaceted construct, it was narrowly defined as a unidimensional concept. The conceptualization of SCB (Geng et al. 2017) involved green purchasing, reusing, and recycling. This conceptualization focused on individuals' Religions 2020, 11, 634 3 of 17 notable influence over the sustainable attitudes and behaviors of institutions, societies, and particularly that of consumers (Muñoz-García and Villena-Martínez 2020; Wahid and Mustamil 2017;Oman and Morello-Frosch 2018;Eckhardt et al. 2010;Hira 2012;Papaoikonomou 2013;Pepper et al. 2009). Increased interest of marketing researchers in this area is evident through many studies (e.g., (Arvidsson 2014;Bamossy et al. 2011;Belk et al. 1989;Bonsu and Belk 2010;Gould 2006;Izberk-Bilgin 2012;Mathras et al. 2016;McAlexander et al. 2014;Mick 2017;Mittelstaedt 2002;Muñiz and Schau 2005;Redden 2016;Rinallo et al. 2013aRinallo et al. , 2013bRinallo et al. , 2016Sandikci and Ger 2009;Schouten and McAlexander 1995;Veer and Shankar 2011). The community of marketing scholars' needs to urgently comprehend and research the role of spirituality in current consumption. The next standard in consumer behavior may likely be about considering a spiritual approach in understanding consumer behavior (Mehta et al. 2020). Vitell (2009) linked the ethicality of consumers with their spirituality. Through his research findings, it was established that spirituality will instill strong moral values in the consumers and they will indulge in ethical practices, sustainability is based on consumer ethics and moral values (Vitell et al. 2005).
Hypothesis 1 (H1). Spirituality has a significant positive impact on reusing.

SCB-Reusing and Psychological Well-Being
Well-being, referred to as mental health, has three forms: Social, emotional, and psychological (Petrillo et al. 2015). Well-being is addressed in two categories of hedonic and eudaimonic. Perspective towards well-being is not limited to self-pleasure, rather it extends to the benefit of the society. Eudiamonic perspective explains the psychological well-being by associating it with individual goals directed towards society, resource deployment, increased self-sufficiency and efficacy, and social relationships (Petrillo et al. 2015). Hedonic perspective measures well-being objectively, whereas eudiamonic measures it subjectively (McMahan and Estes 2011).
Consumer decisions are responsible for their state of psychological well-being (Griffin 2017). Large scale survey data suggest that those who engage in reusing are more likely to report greater subjective well-being (Ginkel 2020) If individuals want to maximize their happiness (and psychological well-being more broadly), it will be useful to know the types of behaviors that tend to increase it. An investigation into the relationship between SCB and psychological well-being may reveal that this behavior directed towards sustainability convenes benefits to those who engage in it (Kasser and Sheldon 2002).
Sustainable consumption's positive influence on consumers' subjective well-being is broadly supported by research on prosocial behavior and subjective well-being, as well as intrinsic motivation. First, research shows that strong social relations are pivotal for people's subjective well-being (Diener and Seligman 2002) and that prosocial activities influence subjective well-being (Dunn et al. 2011). For example, research demonstrates that prosocial spending, such as spending money on others or donating money to charity, makes people happier (Dunn et al. 2008). As such, participation in pro-social activities should enhance a consumer's subjective well-being.
Hypothesis 2 (H2). SCB-Reusing will have a significant positive impact on psychological well-being.

Mediating Role of SCB-Reusing
Personal factors determine individual behaviors. Spirituality is an individual's attitude towards the world. Spirituality is aimed at peace, purpose, and meaning of life while establishing a connection with others (Reachout Australia 2020). Sustainable consumption is directed towards conserving the resources, benefits of other individuals, society, and the environment. Spirituality and sustainability are interlinked. Spirituality develops a close sense of self-awareness in individuals and they become Religions 2020, 11, 634 4 of 17 mindful of their behavior towards nature and its resources. Spirituality directs human behavior towards minimalizing and conserving the resources. This sense of connectedness and altruism directed towards social, economic, and environmental benefit encompasses a sense of contentment in individuals. It is vastly accepted through past literature that well-being is the foremost benefit that people derive from engaging in sustainable behaviors (Seyfang and Smith 2007;Seyfang 2009).
In light of the above discussion, we can establish the rationale that sustainable consumption mediates the relationship between spirituality and psychological well-being. Therefore, we hypothesize our third hypothesis as: Hypothesis 3 (H3). Sustainable consumption will mediate the relationship between spirituality and psychological well-being.

Moderating Role of Religiosity
Religion, in terms of moral values, beliefs, judgments, attitudes, and actions, significantly affects the lives of individuals. Individual behavior is also governed by religion (Goldberg 2006). Spirituality and religiosity are certainly correlated. Spirituality is referred to as "quest for common truth", while religiosity tends to be associated with more accepted beliefs. Religion varies with culture, whereas spirituality has a standard collective understanding across the world. Religiosity is strongly associated with spirituality and encourages morality (Emmons 1999). It is suggested in the literature (Orellano et al. 2020) that the moderating role of religion is needed to understand the more accurate and comprehensive relationship between the constructs. In this study, religiosity is taken as a moderator to understand its effect on the relationship between spirituality and sustainable consumption behavior.

Hypothesis 4 (H4).
Religiosity moderates the relationship between spirituality and sustainable consumption behavior.
*Graphical representation of all the relationships is given in Figure 1.
Religions 2020, 11, x FOR PEER REVIEW 4 of 17 in individuals. It is vastly accepted through past literature that well-being is the foremost benefit that people derive from engaging in sustainable behaviors (Seyfang and Smith 2007;Seyfang 2009). In light of the above discussion, we can establish the rationale that sustainable consumption mediates the relationship between spirituality and psychological well-being. Therefore, we hypothesize our third hypothesis as: Hypothesis 3 (H3). Sustainable consumption will mediate the relationship between spirituality and psychological well-being.

Moderating Role of Religiosity
Religion, in terms of moral values, beliefs, judgments, attitudes, and actions, significantly affects the lives of individuals. Individual behavior is also governed by religion (Goldberg 2006). Spirituality and religiosity are certainly correlated. Spirituality is referred to as ''quest for common truth'', while religiosity tends to be associated with more accepted beliefs. Religion varies with culture, whereas spirituality has a standard collective understanding across the world. Religiosity is strongly associated with spirituality and encourages morality (Emmons 1999). It is suggested in the literature (Orellano et al. 2020) that the moderating role of religion is needed to understand the more accurate and comprehensive relationship between the constructs. In this study, religiosity is taken as a moderator to understand its effect on the relationship between spirituality and sustainable consumption behavior.

Hypothesis 4 (H4). Religiosity moderates the relationship between spirituality and sustainable consumption behavior.
*Graphical representation of all the relationships is given in Figure 1.

Methodology
The research is quantitative in nature. Linkages between the constructs have been proposed and then tested statistically using SMART PLAS 3. Four hundred questionnaires were distributed and 286 were usable for data analysis. Sample size adequacy is supported by Comfrey and Lee (1992) Reusing Spirituality

Religiosity Psychological
Well-Being

Methodology
The research is quantitative in nature. Linkages between the constructs have been proposed and then tested statistically using SMART PLAS 3. Four hundred questionnaires were distributed Religions 2020, 11, 634 5 of 17 and 286 were usable for data analysis. Sample size adequacy is supported by Comfrey and Lee (1992) where a sample size of 300 is considered to be fair. Our sample size is close to this desired sample size. Data collection was done using a cross-sectional approach. To gather data using a cross-sectional approach, researchers selected the survey research method. Survey was conducted using a questionnaire that was designed specifically for this research by adapting previously developed tools for the specific constructs. Questionnaire gathered information divided into two sections. First section gathered information regarding the demographical characteristics of the sample and the second section contained the scale of the constructs.

Participants
The present study consisted of a purposive sample of 286 (42%) men and (58%) women. Respondents were recruited from few cities of Punjab and the capital city of Pakistan, Islamabad. Participants' ages ranged from 21 to 51 years, income ranged from Pakistani Rupees (PKR) 30,000 to more than (PKR) 70,000. Demographic characteristics are given in Table 1.

Measures
All the constructs were measured using a six-point Likert scale (1 = Strongly Disagree, 6 = Strongly Agree).
Spirituality was measured using a five-item scale developed by Iwata (2006). Reusing as Sustainable Consumption Behavior was measured using a three-item scale developed by Lee et al. (2015). Fourteen-item scale developed by Tennant et al. (2007) was used to measure Psychological well-being. Religiosity as a moderator was studied using a 10-item inventory scale developed by Worthington et al. (2003).

Method of Analysis
PLS-SEM was used to analyze the data. PLS-SEM was used because of the following reasons: Religions 2020, 11, 634 6 of 17 1.
Exploratory Study: This study is exploratory as it has proposed and tested new linkages among the constructs. PLS-SEM is the most suitable for the exploratory research framework Muhammad et al. 2017).

2.
Robustness: A particularly prominent research stream in PLS-SEM has provided complementary methods for assessing the results' robustness Latan 2018)

3.
Sample Size and Data Normality: PLS are commonly extended to both large and small samples without concern for the normality of data. Previous studies have proven that PLS does not impose sample size restrictions on the underlying data (Marcoulides and Saunders 2006).

Results
As suggested by (Anderson and Gerbing 1992), a two-stage analytical procedure was adopted. The first stage involved testing the measurement model (which are internal consistency reliability, convergent and discriminant validity [DV]), and the second stage involved examining the structural model (which is hypotheses testing). Data analysis was done by first estimating the measurement model followed by the structural ).

Measurement Model
Reliability and validity are considered in the measurement model ). SmartPLS has been used to evaluate the measurement model of the study, items loading, rho_A, AVE, and discriminant validity were measured. The results show that all factor loadings are greater than 0.60, which satisfies the condition of reliability, as reported in Table 2. For the evaluation of the measurement model, assessment of reliability and validity are important measures (Henseler et al. 2009).  (Muhammad and Gul-E-Rana 2020;). The minimum threshold value for AVE is 0.50. The value was greater than the minimum threshold. The assessment of construct reliability is done by using Dijkstra-Henseler's rho indicators (Dijkstra and Henseler 2015). The minimum 0.70 reliability value is achieved of all composite indicators as benchmark suggested by Henseler (2017). The latent variables also meet the standard requirement of convergent validity. The values of VIF are below the threshold (<5), which confirms the absence of multicollinearity.
The Fornell-Larcker criterion is a common approach to assess the discriminant validity, as shown in Table 3 diagonal elements (bold). The values of all indicators, which are shown in Heterotrait-Monotrait (HTMT) are below the criteria <0.85 (Figure 2). Therefore, we can say that results are showing discriminant validity among all variables of the study. HTMT value <0.90 is acceptable .
The diagonal value (in bold) is the square root of AVE, while other values are the correlations between the respective latent construct. The discriminant validity is achieved when a diagonal value (in bold) is higher than the values in its row and column. Referring to the above table, it can be concluded that discriminant validity for all constructs is achieved.
Table 3 results indicate that the discriminant validity of the measurement model was satisfactory. The discriminant validity of the model was established based on results. The measurement model was satisfactory as the results were as per the standardized values. The discriminant model was tested and found acceptable based on values, then the structural model was evaluated.
All loadings are significant at 0.001 level (2-tailed); rho_A, Dijkstra-Henseler's rho indictors; VIF, Variance Inflation Factor. The Fornell-Larcker criterion is a common approach to assess the discriminant validity, as shown in Table 3 diagonal elements (bold). The values of all indicators, which are shown in Heterotrait-Monotrait (HTMT) are below the criteria <0.85 (Figure 2). Therefore, we can say that results are showing discriminant validity among all variables of the study. HTMT value <0.90 is acceptable . The diagonal value (in bold) is the square root of AVE, while other values are the correlations between the respective latent construct. The discriminant validity is achieved when a diagonal value (in bold) is higher than the values in its row and column. Referring to the above table, it can be concluded that discriminant validity for all constructs is achieved.
Table 3 results indicate that the discriminant validity of the measurement model was satisfactory. The discriminant validity of the model was established based on results. The measurement model was satisfactory as the results were as per the standardized values. The discriminant model was tested and found acceptable based on values, then the structural model was evaluated.

Structural Model
In order to estimate the research model of the present work, we employ a bootstrapping procedure through 500 randomly drawn subsamples with replacement at a 0.05% level of significance. The execution of bootstrapping provides a confidence interval and standard errors to assess the statistical significance of the variables of interest (Henseler et al. 2009;. Table 4 presents the estimated values of path coefficients. Factors loadings and path results are given in Figure 3. The results in Table 4 show that spirituality has significant and positive (p = 0.000, β = 0.337) impact on psychological well-being. It has also significant and positive (p = 0.010, β = 0.200) impact on reusing (SCB). The results also show that reusing (SCB) has positive and significant (β = 0.168, p = 0.012) impact on psychological well-being and religiosity also has positive and significant (β = 0.314, p = 0.000) impact on reusing (SCB). Table 5 shows that the indirect relation between spirituality and psychological well-being through mediation of reusing (SCB) has also been found significant and positive (p = 0.000, β = 0.434). It implies that our finding supports mediation of reusing (SCB) between spirituality and psychological well-being.

Discussion
This research article manifests the results of an exploratory study about the relationships between spirituality, reusing as a sustainable consumer behavior (SCB) (in the clothing fashion industry), moderating effect of religiosity, and subjective well-being as an outcome of SCB-reusing. The diversity of spirituality, religiosity, reusing and well-being characteristics of the sample studied, and the fundamentally theoretical approach of previous studies to the understanding of the prosustainable character of spirituality and religiosity, make this study worthwhile.
Developing sustainable consumption behavior in consumers is highly desirable by the marketers and the policymakers. To incorporate certain behavioral patterns, it is important to understand the factors leading those behaviors (Peattie 2010). Factors can be both personal and environmental. This study has taken into account spirituality as a personal level factor leading consumers towards sustainable consumption behavior. This study has explained that spirituality and religiosity together have a positive significant impact on sustainable consumption behavior.   Table 6 shows that the interaction term (spirituality × religiosity) has a significant moderating effect (p = 0.282) on reusing (SCB). When the interaction term does impact significantly then the moderation is existing. It implies that the results show support of the moderating variable between spirituality and reusing (SCB).  Table 7 presents a model fit summary. SRMR is an index of the average of standardized residuals between the observed and the hypothesized covariance matrices (Chen 2007). The SRMR is a measure of the estimated model fit. The model achieves good fit with SRMR = <0.08 (Hu and Bentler 1999). Table 7 shows that this study model's SRMR was 0.046 (saturated model) and 0.063 (estimated model), which revealed that this study model had a good fit, whereas the chi-square was equal to 1980.511 and NFI equal to 0.929 was also measured.

Discussion
This research article manifests the results of an exploratory study about the relationships between spirituality, reusing as a sustainable consumer behavior (SCB) (in the clothing fashion industry), moderating effect of religiosity, and subjective well-being as an outcome of SCB-reusing. The diversity of spirituality, religiosity, reusing and well-being characteristics of the sample studied, and the fundamentally theoretical approach of previous studies to the understanding of the pro-sustainable character of spirituality and religiosity, make this study worthwhile.
Developing sustainable consumption behavior in consumers is highly desirable by the marketers and the policymakers. To incorporate certain behavioral patterns, it is important to understand the factors leading those behaviors (Peattie 2010). Factors can be both personal and environmental. This study has taken into account spirituality as a personal level factor leading consumers towards sustainable consumption behavior. This study has explained that spirituality and religiosity together have a positive significant impact on sustainable consumption behavior.
Spirituality, which is directed towards one's inner self, would lead to the development of strong consciousness toward the society and the environment (Tloczynski et al. 1997). Spirituality has an impact on how we consider our actions will influence the society and environment (Coates 2004). Spirituality leads people to find the meaning of life (Fry 2000). This guides individuals to connect with the ethical and moral values toward life, society, and economy (Vitell et al. 2016). As spiritualty grows, a person is more inclined toward simplicity, less accumulation of goods, and low materialism (Shaw and Moraes 2009;Rudd 2006). Engaging in sustainable consumption involving reusing will address the spiritual beliefs of the individual (Phipps et al. 2013). This study has empirically tested the relationship between spirituality and reusing and has found a significant positive relationship between the two constructs. This means that an increase in spirituality among the consumers will lead them toward reusing (SCB) and they will engage in practices that will conserve the natural, economic, and social resources. This result is in line with the study conducted by (Subrahmanyan and Gould 2012).
Reusing will lead to elongated use of a product, thus increasing the life cycle of the product. The larger life cycles will have a twofold effect, one in terms of consumer resources, that they will spend less on buying new things and spending the saved resources on other activities (Castellani et al. 2015). Secondly, the companies would have to engage less in raw material procurement and fewer production cycles. This would conserve the natural resources and would also help companies to conserve the resources (energy) involved in production cycles (Cooper 2005).
This research aims to answer whether sustainable consumption can provide benefits to individuals, as it does to environments and societies. Psychological well-being has been considered as one of the main, ultimate goals of life (Haidt 2006). As such, an achievement of psychological well-being is an outcome of participation in sustainable consumption (Helne and Hirvilammi 2015). The psychological well-being of an individual is considered to be linked with their belief systems and their behaviors. The results of this study have shown that spirituality has a strong positive relationship with the psychological well-being of individuals (Ivtzan et al. 2013). This important relationship has also been studied through the mediation effect of sustainable consumption behavior in this study. Results have shown that sustainable consumption behavior mediated the relationship between spirituality and psychological well-being (Sharma and Jha 2017).
The above discussion supports the view that the individuals involved in resource conservation, sustainability, social and economics benefits of the society will have a positive impact on their personal well-being. The actions that are directed toward the benefit of the society and economy have an impact on the better self of the individuals. Human actions are naturally directed toward well-being and happiness (Schmitt et al. 2018). Therefore, when personal characteristics would lead individuals toward the sustainability of the environment, they will have a positive impact on their well-being and they would derive happiness and satisfaction from their lives. However, living a happy life with psychological well-being has become a challenge for the individuals as they have to limit their behaviors within the conservation limits. Spirituality, in this case, would significantly support the intrinsic motivation of the individuals to direct their behaviors toward the benefit of the society (Nash and Stewart 2002). Spirituality leading to sustainable consumption behavior is not only rewarding outwardly but also it is an internally rewarding behavior leading toward the psychological well-being of the consumers.
This research has taken religiosity as a moderator between spirituality and sustainable consumption behavior. Though religiosity and spirituality are often considered to be overlapping concepts, originally, they both relate to different domains of consumer beliefs and values, respectively. Spirituality is directed inwards and is universal, whereas religiosity varies from culture to culture, so it is contextual. In a country like Pakistan, where religiosity derives the major decisions and behaviors of individual (Bukhari et al. 2019) consumers and society on the whole (Bakar et al. 2013), its interaction with the element of spirituality to understand the SCB has revealed a significant impact on the reusing behavior of consumers.

Implications
These relations have addressed gaps in the literature and aided the mounting need for understanding sustainable consumer behavior and its outcome in terms of psychological well-being. Understanding these relations will build on the prior literature in sustainability and consumer well-being to contribute more broadly to identifying ways to enhance consumer well-being rooted in sustainability.
This study will contribute insight toward marketing practices to the increasing market of sustainable products and services. Consumer segmentation is a basic tool for developing products and strategies. Developing consumer segments or identifying segments based on spirituality would help marketers to develop strategies that would relate to their inner self and moral identities in terms of SCB. Developing strategies around sustainability and investing in sustainability has marked a reason for success for the companies. It is evident from the studies that companies who invest and support the issues related to sustainability have higher goodwill among their consumers. Therefore, when companies invest in sustainability, they will be able to attract consumers who have higher spirituality as well as religiosity. Companies can direct their promotional campaigns to communicate the product and service-related reusing benefits for achieving psychological well-being.
Companies can have a two-fold application of their market strategies while rooting their marketing-based decisions in sustainability, they can promote both the company social responsibility in terms of conserving the natural resources and also being consumer-focused by promoting psychological well-being as an outcome of engaging in SCB.
Thinking and evaluating sensibly, it can be easily rationalized that businesses have no incentive to elongate the life cycle of their products. The elongated product life cycles diminish the revenue that the companies would get from selling new goods. However, more and more companies are developing ideas in order to decrease consumer waste. Another reason for companies to strategize around stretched life cycles is the rising price of raw materials and metals, and partly due to both consumers and companies becoming more aware of the need to protect our environment. Post-purchase decisions are usually governed by the consumers but putting the whole responsibility on consumers to think and come up with the ways to reuse their products will burden their repurchasing. Therefore, companies should develop programs and strategies focusing on ways for reusing their products.
This study has its limitations. First, the sample size is small. Increasing the sample size would improve the generalizability of the results. Data have been collected using the cross-sectional method. If the time lag method would be implied in future studies, it would help in reducing the element and chances of common method bias. This study has taken into account spirituality as the only presdictor of reusing. However, in future studies, other variables, like income, gender, and personality, can alos be taken into account to have an indepth understanding of the concept. This study can also be conducted in another culture. Results of both the studies can be compared to comprehend the cultural differences specific to reusing. Cultural dimensions can also be taken as a moderator in future studies between the predictor and reusing.
Author Contributions: S.I. is the principal and corresponding author of this paper. S.I. and M.I.K. conceived the proposed idea. S.I. collected the data and perfomed the data analysis using the analysis tools. Paper is written by S.I. under the support and guidance of M.I.K. M.I.K. supervised the findings of this work. Both the authors discussed the results and contributed to the final manuscript. All authors have read and agreed to the published version of the manuscript.
Funding: This research received no external funding.

Conflicts of Interest:
The authors declare no conflict of interest.


Analysis of the Implementation of the Standard Performance ABNT NBR 15.575/2013: A Case Study with Brazilian Constructors

The development of studies about the housing constructions developments came from the need to ratify the effectiveness of the construction systems to the detriment of the low quality of the final product related to civil construction, which was unfolded in the creation of ABNT NBR 15,575 / 2013 Housing Constructions Performance. However, its implementation is still a point of discussion among several companies in this field, besides there is a gap between the requirements and established criteria and the adequacy of the constructive practices. Thus, the present work aims to analyse, through a multiple case study, the process of implementation of the Standard Performance in Brazilian construction companies, focusing on the main difficulties of implementation. For that, semi-structured interviews were carried out in 5 constructors, being possible to identify the implementation process adopted by each company and its main difficulties of adequacy to the norm. Thus, it was possible to verify that although the standard performance is required, the increase in costs resulting from this requirement has delayed its implementation, being the main difficulty of adequacy. In addition, it was observed that although the implementation process of the regulations is incipient, any effort in its direction represents an improvement in the quality of the civil construction and, consequently, in the durability and useful life of the buildings.

Introduction
The Brazilian Civil Construction Industry (CCI), despite integrating a large portion of the Gross Domestic Product (GDP) of the country, is still marked by the low quality of the final product [9], failures to comply with technical norms and of processes and operations [11].
In this context, NBR 15.575 [1] represents an important milestone for improvement in the CCI, since it establishes requirements and criteria, based on user requirements, that the building must achieve during use, acting as a parameter for a construction with higher quality from the project phase to the use phase [1].
However, despite the importance of norm and effort the different industry agent ( [3,6,7,13]) there are still difficulties of application and, especially, in your understanding ([8, 11)]. A survey conducted by CBIC [7] pointed out that only 69% of respondent recognize the importance of the Standard Performance, evidencing the need to deepen the discussions, as well as better disseminate this norm. Thus, it is questioned: how has Standard Performance impacted the builders of Brazil?
Thus, the present study aims to analyze how Brazilian companies are developing the process of implementing the Standard Performance. For this, a multiple case study was developed with 5 constructors, which made it possible to identify the importance of the normative, the main difficulties and the changes in the constructive processes influenced by the norm.
Thus, the present study was divided into 5 sections, the first being this introduction.
In the second section the debate on the Standard Performance is deepened, presenting theoretical basis on the main difficulties to comply with the normative. In topic three, is exposed the adopted research method, indicating the strategy used for the data collection and the characterization of the subjects of the research. Then, in section four, the results are presented and discussed, followed by the final considerations and, finally, the references.

Literature Review
According to ABNT NBR 15575 (2013), performance can be understood as the behavior in use of a building and its systems and may vary depending on the exposure conditions and the perception of each user.
As performance is variable, the norm reunites a set of requirements and criteria established exclusively for residential buildings and their systems, based on user requirements, regardless of their shape or constituent materials [1], serving as reference for a construction with higher quality. The performance requirements of the standard are conditions that qualitatively express the attributes that the building housing and its systems must possess in order to meet the requirements of the user, while the criteria are quantitative specifications of performance requirements [4]. DOI  ABNT NBR 15.575 (2013) comprises six major areas and involves all the productive complexes of the construction chain [12]. Based on the Safety, Habitability and Sustainability guidelines, the norm is organized in six parts, according to the building systems, and subdivided into thirteen disciplines that refer to the requirements to measure the performance of building [10], as summarized in Figure 1. The disciplines of the norm allow a systemic evaluation of the construction and confer benefits of quality, value aggregation and constructive highlight, strongly influencing the economic scenario of the companies [5].
It should be noted that the standard under study does not include systems of electrical, logic and communication installations, claiming that existing norm already meet the requirements for these subsystems [1].
It is worth mentioning that the Standard Performance does not replace the pertinent norms, that is, ABNT NBR 15575 (2013) cites more than 150 standards which are broken down into more than one thousand other norms.
Perhaps for that, among other reasons, the normative still encounters difficulties of application, mainly in its understanding and in the instruction as to the use of its system [10].

Methodology
As a research method, a multiple case study [16] was carried out with a qualitative approach, with exploratory and descriptive objectives [8], with 5 Brazilian companies whose delimitation is presented in Figure 2.
The study was classified as qualitative because it was based on different realities in order to extract multiple meanings of the phenomenon analyzed [11]. As for the objectives, it was classified as exploratory and descriptive because it was sought to expose the characteristics of the studied group, while it explored exhaustively the object of study [14]. The data collection was developed through a semi-structured interview script [12], with 21 questions divided into three sections: (i) company characterization, (ii) Standard Performance and its implementation, and (iii) compliance with requirements acoustic performance. It is emphasized that a pretest was carried out and that the script remained the same. The results explored in this article correspond to 2 part of the interview. Table 1

Results and Discussion
This section refers to the data collected in the second part of the interview script and was divided into two main parts: (i) the process of implementing the Standard Performance in each company studied, focusing on the methodology used; and (ii) the main difficulties faced by each construction company. Figure 4 shows the process adopted by each company for the implementation of the Standard Performance. The following is describe the processes of each of the companies. The acoustic performance discipline was not tested, considering that the minimum performance would be met, according to the tests performed by SiNAT [3].

Company A
In addition, the company uses the results obtained with this consultancy for other works of the same size, provided they have the same architectural design, according to the guidance of the consulting firm that acted in this study of implementation of the Standard Performance.

Company B
The

Company C
Although Company C works in vertical and SH residential works, the process of implementing the normative under study was the same for the two construction systems, differentiating only the measures adopted to suit the standard in function of the different systems used.
The practice of benchmarking was adopted as a means to adjust the internal structure of the company to the requirements of the standard.

Company D
The implementation of the Standard Performance began in 2012, when there was a public consultation on the normative.
Thus, the adaptation to its conditions occurred in a gradual manner, seeking a balance of cost/benefit, performing tests in works that do not have the obligation to follow the standard, aiming to build a prior knowledge about the practices adopted by the company in relation to the guidelines of the standard.
This process involved all the links in the construction chain, creating study groups to discuss some parts of the normative and conducting specific training for some points of the standard, such as DL.
In addition, involvement with Inovacon and Sinduscon during the preparation of the manuals was fundamental to consolidate the understanding of the standard, as the stakeholders pointed out.

Company E
The process of implementing the Standard Performance in Company E is still in the initial stage, since the company does not have any work within the parameters of the standard, since of the projects in execution, two are residential buildings, homologated prior to the promulgation of the norm, and another is a commercial building. DOI  However, one of his works has Leed certification and in it will be carried out some tests related to Standard Performance. It is observed that the approach adopted is similar to that used by Company D. Figure 5 summarizes the main difficulties faced by the companies studied. Each of these difficulties is detailed next.

Adequacy of costs
It is observed that the adequacy of the costs to the guidelines of the Standard Performance is a common concern to the interviewees, due to the cost/benefit imbalance, as shown in Figure 6. As illustrated in Figure 6, the difficulty arises because the period of economic recession faced by the construction industry requires that companies reduced their production costs to become more competitive.
However, the financial resources needed to meet the conditioning the standard makes this balance difficult. This problem was described by CBIC [7], which showed that the increase in production costs would be passed on to the customer, being the same position adopted by Company B, Company C and Company E and commented by Company A (although not translate into a difficulty for the company).
In Company E, according to the interviewee, the tests will be an item that will integrate the budget of future projects, trying to avoid that the budget is exceeded and looking at a way to balance this relation.
In Company D, the cost arising from the requirements of the standard should not reflect in the final customer, as the construction company has a legal obligation to comply with all applicable standards and the client should not pay more for this obligation.

Project Detailing
The increased level of detail of the project was pointed out by most of the interviewees as a difficulty in meeting the Standard Performance.
In this context, the Company D interviewees pointed out that the architectural design was the one that presented the greatest difficulty of adaptation, because, when compared to complementary projects, such as electrical installations, the architecture falls short to comply with and cite technical norms.
Furthermore, the Company C interviewee pointed out that this increase in the level of detail directly impacts the amount invested in the design of the projects, thus justifying the resistance of the designers to adhere to this requirement, since there was a fear in presenting this increase to the finaly customer. DOI

Change in Constructive Practices
It is observed that changes in constructive methodologies to meet the requirements of the standard tend to burden the constructive process because they are practices that the company has not yet mastered. In addition, it is noted that the difficulty in meeting the requirements of some disciplines is related to cost and constructive practices, as detailed in the subsequent topic.  (1) Cost of insulation products;

Disciplines with higher difficulties of attendance
(2) Necessity of change in constructive methods; (3) Need to ensure performance "in the bone"; (4) Performance is related to the building environment. (2) Customer-sensitive.
A D It should be noted that the definition of performance presented by NBR 15.575 [1] becomes an aggravating factor to meet the disciplines whose performance depends on the interaction of the building with the environment, as presented by the interviewees of Company A, Company B and Company C.
In addition, Company D highlights the need to meet the standard of norm with the apartment without the final finishes, such as ceramic, as the customer can choose to receive it without.

Final Considerations
This study aimed to analyze the main difficulties for the implementation of the guidelines of the Standard Performance. For that, a multiple case study was carried out with 5 Brazilian constructors.
Thus, it was possible to verify that the greatest difficulty in meeting the constraints of the performance standard is the costs involved, since the requirements of the regulations tend to burden the construction process.
In this context, it is noted that there is a difficulty in finding suitable professionals to meet the demands of the performance standard, both in relation to the designers, the fear of increasing project costs, and in relation to the laboratories that perform the tests of the standard, since there are few companies that do them, thus raising the amount necessary to carry them out, depending on the law of supply and demand.
It was also concluded that in works of HS, because they are supervised by the CEF, the companies that work in this segment tend to be more careful in meeting the conditioners of the Standard Performance, not being observed the same concern in the constructors who do not act in this norm. Therefore, the end user has an important role to demand from such companies to prove compliance with the regulations. Finally, it can be inferred that the implementation of the Standard Performance, despite being incipient, DOI  deserves to be highlighted, given that any movement towards it is the beginning of an improvement in the quality of civil construction. Further research should include a higher number of companies.


Parametric Modelling of Steel Connectors in a Glulam Based Post and Beam Building System-Towards a Flexible Product Platform Approach

House building projects are distinctive, and the degree of customisation creates bottlenecks in the design process and challenges for production, which results in longer lead time and higher costs. Aligned with a product platform approach, previous studies have introduced cost-effective approaches such as standardisation, modularization, configurators, etc. Still, components that cannot be completely modularized and configured due to high complexity level, may require a lot of engineering efforts during development. A platform approach that can be used to support engineer-to-order products that change over time still needs to be explored. The application of parametric modelling to automate the design process in the construction industry has the potential to further increase both the design and production efficiency. Thus, the objective of this research is to apply parametric modelling in the design of steel connectors used in a glulam based post and beam building system as part of a flexible product platform for increased design and production efficiency. A single case study has been carried out with a Swedish multi-storey house building company. Empirical data were gathered from a workshop with the design team followed by interviews, and document analysis. A computer-supported method for the steel bracket connectors has been developed, that connects post and beam components with pre-defined rules and constraints as part of the platform development. The result contributes to expanding knowledge about the development of a flexible product platform for improved design process and downstream production of customised components with parametric modelling support in the industrial post and beam buildng system.

Introduction
The housing market in Sweden has been undergoing a substantial price increase. The general price level in Sweden is relatively high compared to many other European countries [1]. The growing production costs of house building have been highlighted as a major barrier for the housing market [2]. In fact, companies are constantly looking for approaches to increase productivity and manage the frequently increasing cost [3]. Several initiatives have been performed to increase the efficiency of production and to solve on-site issues as part of continuous improvement. However, the design phase of industrialised house building (IHB) is generally perceived as being inefficient and timeconsuming [4] and found as the bottleneck of productivity in building construction [3,5]. The role of product descriptions have changed over time and more and more tailormade products lead to generate concepts such as engineer-to-order (ETO), modify-toorder (MTO), configure-to-order (CTO) and select variant [6,7]. Customization or unique needs from the customer has been identified as a common challenge facing by the IHB industry [8], where projects differ with unique requirements over time. Product platform strategies and standardisation efforts have had a significant impact on the development time and cost reduction [9,10]. Together with a product platform approach, many previous studies have introduced approaches such as modularization, configurators, etc. that supported to a great extent to become cost-effective. However, some components that cannot be completely modularised and configured due to its high level of complexities required a lot of engineering activities during its development. Transdisciplinary engineering can be supported by a disciplinary ability to respond to different stakeholder's needs and demands. Engineering methods for improved ability to design and manufacture customized solutions could potentially support engineers and construction companies to contribute in transdisciplinary development projects. Platform approach for the component-based product where reusing of design assets has already been a research topic and this is more accountable for the standard products. In other words, a platform strategy that can be used to support the customised product that changes over time still needs to be explored [11,12]. Thus, there should be some dedicated support that could be used to deal with products having ETO nature and to design it more efficiently and ensure producibility.
Companies start to see the benefits of digitalization in construction design and today's CAD systems can be applied for much more than 3D modelling and the generation of drawings [13]. It is possible to automate the design process if the construct of any complex artefact is suitably restricted by adhering to a library of predefined components and assembly details [14]. In the building industry, the implementation of design automation has increased productivity [15] by using parametric modelling to automate Building Information Modelling (BIM) [16]. Thus, the objective of this research is to apply parametric modelling in the design of steel connectors used in a glulam based post and beam building system as part of a flexible product platform for increased design and production efficiency.

Theoretical background
A product platform is a collection of assets, which are shared by a set of products sorted into components, processes, knowledge and relationships [9,10]. They pointed out the benefit of the platform that, "by sharing components and production processes across a platform of products, companies can develop differentiated products efficiently, increase the flexibility and responsiveness of their manufacturing processes, and competitive in the market with competitors that develop only one product at a time." The concept of design assets offers a new way for efficient customisation, reuse and standardisation by introducing and structuring platform elements that are traditionally not used in a platform setting [12]. The concept of flexible product platform is first proposed by Suh, De Weck [17]. Flexibility is defined as ''the property of a system that is capable of undergoing specified classes of changes with relative ease" (ibid). The flexibility of a product platform is its capability achieved by modifying parameters of flexible elements [18].
BIM is not only a computer application supporting the 3D object modelling of buildings, but also allows both automatic parametric generation of designs that respond to various criteria and the prospect of computer-interpretable models and automated checking of designs after they are generated [19]. The knowledge representation during the design phase is certainly becoming an important issue in the area of design automation [14]. Eastman, Lee [20] emphasises that the rule-based systems apply rules, constraints or conditions to a proposed design. Parametric Design is "the process based on algorithmic thinking that enables the expression of parameters and rules that, together, define, encode and clarify the relationship between design intent and design response" [21]. Parametric modelling feature permits regeneration of geometry based on geometrical constraints [22] and allows to integrate domain-specific knowledge using explicit mathematical expressions [16]. According to Singh, Gu [23] the modelling and technical flaws can be reduced as the set of rules for building modelling are predefined using parameters in BIM. Implementing Parametric and Generative Design techniques in Glued laminated timber (GLT) could improve the overall efficiency and can be considered an effective tool for improving the capabilities of design and manufacturing processes in the building industry [24]. Parametric constraint-based design within BIM platforms offers an automatic design validation, where the model is automatically updated to adapt changes [25].

Research Methodology
The research framework used for this study was Design Research Methodology (DRM), proposed by Blessing and Chakrabarti [26]. This DRM framework comprises four iterative stages used for conducting research in the engineering design field. DRM is used as a framework for the entire research project and this article presents the outcome of the two final stages of DRM with an emphasis on the Prescriptive stage. The support was proposed to improve the current state of the design process in the case company in the prescriptive study stage and an initial evaluation was done with the designers as part of the descriptive study II phase.
The study was qualitative in nature with a combination of a literature survey and a single case study by linking a Swedish multi-storey house building company. Empirical data was collected from a workshop, semi-structured & unstructured interviews and document analysis. A workshop session was conducted by including both design engineers and the management team. This section initially helps to brainstorm the needs, current challenges facing and to understand the vision to achieve from the company point of view. A project team has been formed as an outcome from the workshop with the aim of different development and improvement activities where the case of steel connectors was in the priority list. The team includes a CAD programmer, two structural engineers and the researcher. In addition, four semi-structured interviews were conducted with key persons who have extensive experience from the design department. The respondents were: the design manager, senior structural engineer, CAD programmer, and structural engineer. Additionally, unstructured interviews were conducted with the key designer on a frequent basis in order to understand the current knowledge, challenges and opportunities during the design of connectors. The interviews were audio-recorded and transcribed before the materials were analysed. Document analysis was initiated parallel with the interviews to get in-depth knowledge about the previous projects. Documents related to the design of the connectors from previously finished projects were reviewed. The reviewed documents include building models, part drawings, design templates, bill of materials, component library etc. The bracket connection was chosen as the experimental object where the parametric modelling was applied. At first, the standard parameters and dimension for the bracket connection were formulated from the weekly meeting with the project team. The algorithm was developed as a Plug-in application connected to the BIM tool (Tekla Structures) using Visual Basic (C#) and the open API in Tekla Structures with the support of CAD Engineer. The input parameters for the connection are defined with user interface (UI) support of Plug-in used in Tekla. Finally, an initial evaluation was carried out with the designers to verify the results generated.

Case company description
The case company is one of the leading manufacturers of glued wood in Europe. They developed a unique building system on the multi-stored house building market and launched it in 2007. The system was developed based on the prefabrication technique and named as Trä 8 building system and can be used for up to 8-meter span. This building system can be categorized in the timber based post and beam type of industrial building. The fundamental part of the system is the idea of "Big Size Pre-Cut", where a high level of prefabrication of large building elements and sets of material is developed through efficient production. The main components of the building system include of post, beams, trusses for stabilization which is made of glued wood, floor elements and roof elements made of Kerto material and glulam, and steel connectors. GLT is a widely used structural engineered building material composed by at least two parallel laminations of wood which may include one or two boards next to each other (BS EN 14080:2013).

Case findings -Design of steel connectors used in the buiding system
Steel connectors are precisely engineered components used to transfer loads from one component to another component. They are used, for instance, to transfer loads from different floors to the foundation through the vertical columns. Each connector is designed to function in different ways and to transfer different magnitude of loads from the building to the foundation. There are four main types of connectors commonly utilized in the building system by the case company as shown in Figure 1.
(1) Column footing: This is the most common type of column footing connection for the building system. On top of a cast-in reinforced steel plate, a second plate with 4 threaded rods are welded on site. The column is delivered with a third plate mounted in the factory using glued-in threaded rods. The third plate uses nuts and washers and the lower washer could be levelled using a plane laser before erecting the column.
(2) Column footing with trusses: When trusses are used in the building, this type of connection is ideal for footing. Trusses are connected to the column footing with the use of dowels. First, the welded plate is mounted with the column in the factory and then, the whole assembly is connected to the reinforced concrete with foundation bolts at site.
(3) Bracket: This type is used to connect the column with the beam in the building system. The main purpose of these connectors is to transfer the loads from the floors to the vertical columns. Additionally, they function in transferring the horizontal and vertical loads to the wooden trusses.
(4) Truss connection: To stabilize the building structure from the horizontal loads, wooden trusses are used. The element consists of two columns with beams and diagonals connected with slotted in steel plates fastened with dowels. The connector design process generally involves structural design and modelling of connectors as shown in Figure 2. The structural design normally begins by understanding the scope of the project and the different requirements of the customer, i.e., type of building, number and height of floors, apartment details etc. Identifying the different loads acting in the building is the first step of the structural design. This includes ordinary forces from all loads such as dynamic loads, static loads and special loads. Loads imposed on the building should be transferred to the foundation to keep the building stable. Therefore, connectors can be considered as the most critical component of the building system, to transfer both vertical and horizontal forces. The subsequent step is to find out the dimension of glulam post and beam where STATCON or TRUSSCON is used as the tool for performing it. The calculation starts with the beam as the dimension of the beam is necessary to calculate the dimension of the post. The design of connectors can be made when the required loads and dimension of members are calculated. Math CAD is used to design different types of connectors. For example, the vertical load, horizontal load, the dimension of beam and size of screws that goes into the post are the main input data for calculating the brackets. The bracket design is governed by the load calculation. First, the dimension of beams is calculated for the entire structure. For simplicity, the value of different dimensions is kept as low as possible. Once the dimensions of beams are decided, the structural engineer can determine the amount and length of screws needed for each beam cross-section. The modelling of brackets is initiated when the modelling of beam and column members has been completed. This is because the information about the number of screws can only determine from the beam profile. The longest beam with a higher force is often used as a reference for all other beams with a similar height to avoid the calculation of individual beam separately. Likewise, different variants of brackets can be reused in different parts of the building. Connectors for balcony is not included in the building system as it differs depending on the customer requirements. The next step is the modelling phase and all these values are forwarded to CAD designer as AutoCAD drawings, who take care of the modelling of building and detailing of different components. Tekla Structures is used as a tool for modelling the whole building and creating a fully detailed production model of the building components. The program generates 2D drawings and machine files using the information in the building model. Finally, all the drawings and values in digital format are forwarded to the suppliers who produce the connectors. For some connectors, pre-assembly is required before the final assembly on site. The collision between different elements in the connector has been recognized as the major challenge in the design. So adequate control is required while defining different parameters and its dimensions. Moreover, any change in the size of members or the height of the floor would generate a new variant of bracket which is the main challenge for designers.

Application of parametric modelling in the bracket connection
The prescriptive research activity has been conducted through two main stages: coding the method and testing the algorithm for modelling. The bracket connection was selected as the modelling object as this is one of the commonly used and challenging components of the existing platform and manual modelling is time-consuming and prone to errors. The first phase refers to programming the parametric algorithm for brackets in a Visual studio, where the parameters were defined with rules, constraints, dependencies and boundary conditions. To perform its calculations, the algorithm requires specific inputs that must be manually created. For designing the brackets, the most significant inputs are the value of the horizontal and vertical load, the dimension of primary (post/column) and secondary members (beam) and number of screws on the members. A logic has been followed while programming to create the rules for the parametric features of the brackets. In this stage, all the standard parameters and their respective dimensions of the bracket connections have been defined. The rules and constraints that govern the different design have been set with many alternative conditions. Coding begins with defining the values as in the table shown in Figure 3. The next step was to specify different coordinates of brackets. Then, add plates to different coordinates in order to merge with the plates. The thickness of the steel plates is always 5mm and it never changes. Subsequently, postion of different holes and details of screws that should be generated in the plate are specified. Finally, the cutting of the beam is also defined to ensure that the beam is properly seated in the bracket.
The second stage was the testing phase and the use of the algorithm in the BIM environment (Tekla structures). Here, the algorithm performs a geometry analysis to identify the key inputs for further process. The bracket is then inserted to the BIM-model using the Plug-In application where the CAD-engineer can specify the information about the needed screws in the UI of the Plug-In. The size of the beam and column is fetched into the Plug-in from the model. Using this approach, the connection is geometrically dependent and placing of the beam and column and will adapt to any changes of location or dimension. When using parametric modelling in BIM, there are four steps to follow, 1. Select the primary member, 2. Select the secondary member, 3. Add the number of screws in the primary and secondary members, 4. Select the type of screws. These parameters are the input values provided in a dialogue box, as shown in Figure 4. The procedure for generating other types of brackets is generic, and the variants would depend on the beam size used in different parts of the building structure. When designing the brackets, the algorithm automatically checks the rules that are based on the configuration of the objects, their relations or attributes. Here the width of the beam basically decides the number of screws that should generate in the bracket, which in turn governs the height of the bracket. How many screws that can fit in one row would decide the height of the bracket. The algorithm will detect the number of screws and adjust the real height to avoid the collision. It is important that the height of the bracket should be less than the height of the beams. The distance to the first row of the screw is specified from this top of the beam. The primary screws from both sides should be short enough to avoid the collision. Therefore, it is important to define the code with a correct offset in order to avoid the collision. However, designers run a verification check to confirm any collision between screws. The same variant of the connector can be generated in different parts of the building if the beam size is identical. The rules are defined for adapting by itself. Thus, the designer can save time and effort by avoiding the repetaed design of the same connectors. If the size of the beam is different, the parameters should change, and the bracket will follow the predefined set of beam sizes and generate a new solution. Thus, there should be different codes for different types of connections.

Discussion
The analysis of building components shows that the modelling and detailing of steel connectors accounts most of the design time, which was acknowledged by the respondents. The case company produces glulam components and all associated designs are relatively standard. However, steel connectors were identified as the most challenging part of the building system. About 20-30% of the time would be sufficient to design all other components of the building system such as glulam post, beam and, floor elements and remaining is dedicated for the connectors. CAD engineer states that "the technical detailing of connectors remains as a challenge as new connectors have been designed in every project". Currently, limited support is available to streamline the design process and challenging to reuse variants within and across projects. The main reason is changing requirement of the building structure over time and the connectors projects an engineer-to-order characteristics [7]. Therefore, the company was in need of a distinct strategy to improve productivity in the design process. One type of code has been created for the bracket connection, from which several variants of connectors can be generated. So, this can be considered as a design asset in a platform for the bracket connection from which different sets of solutions can be derived [12].
The main objective of this study was to improve the current way of connector design and increase the ability to respond more quickly to customer-specific requirements to enhance producibility. An initiative was taken by the project improvement team by applying the parametric modelling approach in bracket design. The analysis reveals that this modelling approach can be related to a product platform explained by Meyer [9], from which a stream of different variants of connectors can be efficiently developed and produced with an emphasis on the knowledge assets defined by Robertson and Ulrich [10]. In other words, different bracket variants can be derived from the same platform, by predefining the knowledge assets [14] and specify the standard process to execute it. Here, reuse is achieved not by sharing the components rather by sharing the knowledge asset [12] which is pre-defined by various set of rules and constraints using the algorithm [16,22]. The flexibility of the proposed product platform is the ability to rapidly generate a design solution to accommodate both predicted and unforeseen changes through the reuse of design knowledge and computational methods [18]. On this developed platform, knowledge assets are predefined in such a way that the connector can be created that can adapt to dynamic customer requirements by adjusting its structural parameters [17]. The algorithm would take care of advanced geometry that goes into the different bracket connections that the company currently possesses. Thus, flexibility is achieved with the support from parametric modelling. Manual design can be avoided as complete solution is generated with different configurations. Moreover, platform architecture and how it is communicated is important when defining the rule of different configurations [9]. The execution is the same, and faster than selecting different components from a component library where set of solutions are pre-defined. Thus, a robust platform offering a rulebased approach can be developed with the help of parametric modelling. It has the ability to pre-check a model, such as geometry overlaps, rules for attribute and name, object existence and others, more detailed check [20]. To achieve this flexibility in connector design, the designer must identify the components to be modified and then determine how such changes propagate through different attributes.
Developing a rule-based product platform leverages the parametric modeling capabilities of BIM tools to automate the modelling process. The result shows that easy and quick modelling of connectors is possible, and the connections can be made automatically with options for adapting to the alternative design settings that enable design automation [13]. With parametric modelling approach, the rules and constraints are defined to control all possible collisions between these elements. The elements of the bracket are automatically modified, which shortens the modelling time and improves the quality. When members sizes are changed, the connections are automatically alternated according to designer's settings, which allows the accurate design [25]. Moreover, individual drawings can be generated from the model by using the filter option in Tekla that helps to avoid detailing of each bracket from scratch. The algorithm has been programmed in order to handle fluctuating customer requirements and to maintain the capabilities of a building component having ETO characteristics. Furthermore, this new method could support the existing platform to evolve as the algorithm can be updated and add more functionalities to become more agile. Thus, the study presents a novel approach in creating flexibility for the bracket platform with boundary conditions from a post and beam based construction. The case company can be able to make an impact on their design lead time with this approach by generating algorithms for all different types of connectors used for the building system. The result show that the integration of parametric support to BIM would assist designers in decision making and significantly reduces the possibility of inconsistencies. Therefore, the critical factors addresed are the time, cost, customisation and flexibility aspects when implementing parametric modelling approach in the design process [8]. The main limitation of parametric modelling is that skilled workers are required for coding the rules in computer language. A logical approach should be followed and high-level of expertise is needed to define, maintain, managing the algorithm over time, and verify the result to get a accurate outcome. It would consume a considerable amount of time and effort in the beginning while creating the algorithm. The result generated from this research is limited to a type of steel connector (bracket) used in the building system. As a future study, the case company can generate algorithms for other types of connectors for a significant impact on design improvement and validate the results. Moreover, the applicablity of the methodology can be tested and scaled to other type of building systems with components having ETO nature and be considered for future studies.

Conclusion
This article presents the development of a flexible product platform to support the design process of industrialised house building. A case study illustrates how a flexible product platform with parametric modelling approach can be developed and used to design building components having an engineer-to-order characteristics. The result shows that the parametric modelling based product development in the building industry offers flexibility in the design process and supports customization. The findings also provide an overview of the magnitude of the challenge associated to the design of connectors for glulam post and beam buildings. Thus, parametric modelling is a promising design automation tool to generate customised building components and facilitate and build a flexible platform. The approach provides a path forward to improve the design process of connectors and offer a flexible building system that can respond to future uncertainties. The results reveal that the way in which the flexibility is incorporated in the component such as the beam profile, number of screws in primary and secondary member, should consider when designing a flexible product platform for bracket connection.