High-rise reinforced concrete buildings are in great demand in developing countries with rapid urbanization.Construction engineers are facing more and more safety control challenges.One major issue is the understanding of the load distributions,especially the maximum slab load,of structures under construction,which is time dependent.Previous methods were mainly targeted to specific examples,providing specific solutions without addressing the fundamental issues of finding general solutions for load distributions in reinforced concrete buildings with different geometrical and material characteristics during construction.The concept of a structural characteristic parameter is used here to parameterize the main geometrical and material characteristics of concrete structures for generalized assessments of load distributions during construction.The maximum slab load for 20 different construction shoring/reshoring schemes is presented.The results indicate that the traditional simplified method may underestimate or overestimate the maximum slab load,depending mainly on the shoring/reshoring schemes.The structural characteristic parameter approach was specifically developed to assist construction engineers to estimate load distributions to assure safe construction procedures.
Site measurements have shown that slab loads re-distribute,between the slabs during the concrete curing,while the external loadings and structural geometry remain the same.Some have assumed that this is caused by concrete shrinkage and creep,but there have been no studies on how these factors exactly influence the load distributions and to what degree these influences exist.This paper analyzes the influences of concrete shrinkage,creep,and temperature on the load re-distributions among slabs.Although these factors may all lead to load re-distribution,the results show that the influence of concrete shrinkage can be neglected.Simulations indicate that shrinkage only reduces slab loads by a maximum of 1.1%.Creep,however,may reduce the maximum slab load by from 3% to 16% for common construction schemes.More importantly,temperature variations between day and night can cause load fluctuation as large as 31.6%.This analysis can,therefore,assist site engineers to more accurately estimate slab loads for construction planning.
