Effects of construction process on R/C buildings
Abstract
Construction of R/C structures involves a considerable risk. Recent surveys by the National Bureau of Standards, now called the National Institute of Standards and Technology, indicate that a significant portion of concrete construction disasters is due to excessive construction loads applied to the formwork or to the supporting floors. To assess the safety margin during construction, the load distribution between the supporting floors and shores must be accurately estimated. Also, in the age of fast construction and with the increasing use of high strength concrete and steel in the construction of concrete buildings, limits for short and long-term deflections determined by serviceability requirements may be violated. Herein, a probabilistic study of the maximum shore load considering all the key parameters as random variables has been made. The complete load-deflection behavior of the telescopic steel shores has been traced numerically by the finite segment method. Furthermore, a simplified method to trace the load-deflection behavior of the telescopic shores and to predict their load carrying capacity is proposed. Comparison between construction load distributions from different methods is given. The effect of various construction parameters on the load distribution between the supporting floors and shores is extensively investigated. The effect of the fast construction rate on short and long-term deflections has been studied by numerically analyzing a 3-D 3-story reinforced concrete flat plate structural model using the finite element method. In addition, a simplified method to predict short and long-term deflections in two-way floor systems based on the ACI Code design procedure is presented. The simplified method is implemented in a computer program. Concrete cracking and creep are accounted for in the deflection analysis. It has been found that the influence of the variation of construction live load on the maximum shore load is very significant and may cause shore overloading. Furthermore, it is concluded that the maximum shore load follows a normal distribution, within the range of typical values in the present study. It is also found that the fast construction will not increase short or long-term deflections provided that high strength concrete and high early strength cement are used.
Degree
Ph.D.
Advisors
Chen, Purdue University.
Subject Area
Civil engineering
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