the most significant aspect of the structural system utilised for the apa building was the speed at which the steel and concrete composite system allowed the work to proceed. the use of bolted structural steel not only reduced the noise level of the process, considered a major problem at the time when riveting was still common, but allowed for the steel frame to be erected in a period of fifteen weeks. equally impressive was the curing of the concrete which was poured at the rate of two floors in five working days.