Construction loads and load effects in concrete building construction
Abstract
The most critical stage of a structure's lifetime is that of construction. Many, perhaps most, construction disasters occur as a result of the failure of temporary structures, and far more disasters occur during construction than after completion of projects. The most serious deficiency in formwork design is in the consideration of lateral loads. Also, a great deal of damage and loss of property during construction are caused by wind. Consequently, determination of load distribution during construction is one of the critical factors in assessing the structural safety during the construction of reinforced concrete structures. Herein, realistic models of the structure in the construction phase are developed. A practical method to check the slab adequacy during construction is presented. Extensive numerical studies of the distribution of construction loads between multistory framed structures and the shoring and reshoring systems are made, using the computer models developed. A simplified procedure to include the construction live load in the analysis of construction loads is proposed. Furthermore, a simple modification of the popular simplified method for calculating the load distribution during construction is presented. Also, a precise method for assessing wind loads to be used in the design of temporary lateral bracing for open frame buildings is given. Furthermore, a three-dimensional computer model capable of simulating the concrete construction process is developed. The effect of construction process in the analysis of multistory concrete buildings is investigated. It has been found that the simplified method is adequate for predicting the construction location of the maximum slab and shore loads. However, it generally overestimates the actual load ratios. Furthermore, it is concluded that ACI-347 minimum requirement for horizontal loads can underestimate design wind loads by as much as 50%. It is also found that the effect of lateral loads on the construction load distribution is very small and can be neglected for practical purposes. In addition, it is found that neglecting the construction process in an elastic analysis of multistory buildings leads to a significant error in stresses due to dead loads.
Degree
Ph.D.
Advisors
Chen, Purdue University.
Subject Area
Civil engineering
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