Effects of Fast Construction Rate on Deflections of R.C. Buildings

In high‐rise concrete buildings, contractors can increase their construction rate by using high‐strength concrete with a two‐day cycle. The fast construction rate will reduce the cost of formwork, as well as the number of working days. However, the effect of the fast construction rate on short‐ and long‐term deflections is not clearly understood. Herein, a 3‐D three‐story R.C. flat plate‐column system model was analyzed for two construction rates: one floor/two days, the fast rate, and one floor/seven days, the usual rate in practice. The analysis has been made by the finite element method, including the effects of concrete creep and cracking. It is found that the fast rate of construction in high‐rise R.C. flat plate‐type buildings will not increase short‐ or long‐term deflections, provided that high‐strength concrete $(f_c^{\prime }⩾7\text{,}000\mathrm{psi})$ and high early strength cement (Type III) are used. On the contrary, the fast construction rate when using normal‐strength concrete $(f_c^{\prime }=5\text{,}000\mathrm{psi})$ increases deflections by as much as 50%. It is also found that both the creep and the rate of construction have an insignificant effect on bending moments.