Assessment of Lateral and Torsional Stiffness Characteristics of Medium Rise Concrete Buildings

摘要

Design assumptions for five concrete buildings, each representing a different structural system, were evaluated by comparing theoretical results with experimental data on dynamic characteristics. Initial estimates of the natural frequencies and mode shapes were made by using the TABS-77 program. Model improvements were made by incorporating the effects of 'non-structural' partitions and cladding and by considering the efficiency of elevator cores. Improvements were made until theory and experimental results matched for both natural frequencies and mode shapes. Implications of incorrect modelling were investigated for both static and dynamic lateral loadings. This study showed that it is necessary to match both frequencies and mode shapes if an accurate model is desired. Non-structural elements not only add stiffness to the structure but also change the mode shape. Shear lag exists in elevator cores and this should not be neglected. Significant joint rotation can occur in large panel buildings. Considerable inaccuracies are shown to exist in present design practice and this study provides guidance for significantly improving present analytical modelling.