Chapter Six QUANTITY ESTIMATES In addition to preparing clear and concise estimates on the computation sheets. Unless construction plans, as described in Chapter Five, stated otherwise, do not round the the designer must compile an accurate estimate calculations until the value is incorporated of the project construction quantities. This onto the Q-sheet. information leads directly to the Engineer's Estimate, which combines the computed Significant Digits. Perform quantity quantities of work and the estimated unit bid calculations with careful regard to the prices. An accurate estimate of quantities is implied correspondence between the critical to prospective contractors interested in accuracy of the data and the given number submitting a bid on the project. Chapter Six of digits. In all calculations, the number of presents detailed information on estimating significant digits retained should be such quantities for structural projects. that the accuracy is neither sacrificed nor exaggerated. Use the following rules to determine the appropriate number of 6.1 GENERAL significant digits: 6.1.1 Guidelines for Preparing Quantity Number of Digits. Any digit that is Estimates necessary to define the specific value or quantity is considered significant. When preparing quantity estimates, the designer When a measurement is taken, this should consider the following guidelines: measurement may be recorded as 157, this number has three significant digits. Specifications. Cross check all items If the measurement had been made to against the Standard Specifications and the the nearest 0.1, the measurement may Supplemental Specifications to ensure that have been 157.4; this number has four the appropriate pay items, methods of significant digits. measurement and basis of payment are used. Zero may be used to indicate either a Computations. Prepare a separate specific value, like any other digit, or a computation sheet for each item used on the order of magnitude. A number’s project. Include all computation sheets in measurement rounded to thousands, may the project file. be 120 000. The three left-hand digits of this number are significant; each Rounding. Round the quantity of any item measures a value. The three right-hand provided in the Estimated Bridge Plan digits are zeros which merely indicate Quantities Table on the Q-sheet according to the order of magnitude of the number the criteria in Figure 6.1A. The computation rounded to the nearest thousand. The sheet should be calculated to one more identification of significant digits is only decimal place than that noted in Figure possible through 6.1A. Note any required rounding of raw
Chapter Six QUANTITY ESTIMATES In addition to preparing clear and concise construction plans, as described in Chapter Five, the designer must compile an accurate estimate of the project construction quantities. This information leads directly to the Engineer's Estimate, which combines the computed quantities of work and the estimated unit bid prices. An accurate estimate of quantities is critical to prospective contractors interested in submitting a bid on the project. Chapter Six presents detailed information on estimating quantities for structural projects. 6.1 GENERAL 6.1.1 Guidelines for Preparing Quantity Estimates When preparing quantity estimates, the designer should consider the following guidelines: Specifications. Cross check all items against the Standard Specifications and the Supplemental Specifications to ensure that the appropriate pay items, methods of measurement and basis of payment are used. Computations. Prepare a separate computation sheet for each item used on the project. Include all computation sheets in the project file. Rounding. Round the quantity of any item provided in the Estimated Bridge Plan Quantities Table on the Q-sheet according to the criteria in Figure 6.1A. The computation sheet should be calculated to one more decimal place than that noted in Figure 6.1A. Note any required rounding of raw estimates on the computation sheets. Unless stated otherwise, do not round the calculations until the value is incorporated onto the Q-sheet. Significant Digits. Perform quantity calculations with careful regard to the implied correspondence between the accuracy of the data and the given number of digits. In all calculations, the number of significant digits retained should be such that the accuracy is neither sacrificed nor exaggerated. Use the following rules to determine the appropriate number of significant digits: Number of Digits. Any digit that is necessary to define the specific value or quantity is considered significant. When a measurement is taken, this measurement may be recorded as 157, this number has three significant digits. If the measurement had been made to the nearest 0.1, the measurement may have been 157.4; this number has four significant digits. Zero may be used to indicate either a specific value, like any other digit, or a number’s order of magnitude. A measurement rounded to thousands, may be 120 000. The three left-hand digits of this number are significant; each measures a value. The three right-hand digits are zeros which merely indicate the order of magnitude of the number rounded to the nearest thousand. The identification of significant digits is only possible through
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