Distribution of construction loads in columns and shores during construction of reinforced concrete structures

Abstract

Many studies have been performed to apply research results for the time-dependent behaviour of reinforced concrete (RC) framed structures to the design and construction of high-rise buildings. However, shoring, removal of forms, and backshoring at early ages have not been adequately reflected in most studies. Removal of forms and backshoring activities have been dealt with as one construction sequence and the deformation of columns that occurs at an early age before removal of shores was not considered. In this study, a two-dimensional frame analysis program was developed to predict time-dependent behaviour of RC structures. In the program, the actual construction sequence of installation of forms and shores, concrete placement, removal of forms and shores, backshoring, removal of backshores, and application of additional loads are considered to predict axial force variations in RC columns and shores due to the change of concrete member stiffness. In order to evaluate the validity of the developed program, a model RC-framed specimen was tested under the same construction sequence. It was noted that with increasing time the axial forces in columns and shores were increased and decreased, respectively. In addition, column deformations occurred before removal of shores and axial forces in shores were redistributed to columns. Finally, it was also observed that the program predicted experimental results well.