Optimum strength distribution for seismic design of tall buildings

This paper examines the effects of strength distribution pattern on seismic response of tall buildings. It is shown that in general for an MDOF structure there exists a specific pattern for height-wise distribution of strength and stiffness that results in a better seismic performance in comparison with all other feasible patterns. This paper presents a new optimization technique for optimum seismic design of structures. In this approach, the structural properties are modified so that inefficient material is gradually shifted from strong to weak areas of a structure. This process is continued until a state of uniform deformation is achieved. It is shown that the seismic performance of such a structure is optimal, and behaves generally better than those designed by conventional methods. The optimization algorithm is then conducted on shear building models with various dynamic characteristics subjected to a group of severe earthquakes. Based on the results, a new load pattern is proposed for seismic design of tall buildings that is a function of fundamental period of the structure and the target ductility demand. The optimization method presented in this paper could be useful in the conceptual design phase and in improving basic understanding of seismic behavior of tall buildings

Experimental study on seismic performance of strap-braced cold-formed steel shear walls

This paper presents a detailed investigation of the lateral performance of X-strap braced cold-formed steel shear walls and their response modification factor, R. Four full-scale 2.4 × 2.4 m specimens with different configurations were tested, and their responses recorded under a standard cyclic loading regime. Of particular interest were the specimens' maximum lateral load capacity and deformation behaviour as well as a rational estimation of the seismic response modification factor. The study also looks at the failure modes of the system and investigates the main factors contributing to the ductile response of the cold formed steel (CFS) shear walls in order to suggest improvements so that the shear steel walls respond plastically with a significant drift and without any risk of brittle failure, such as connection failure or stud buckling. The walls tested have different number of strap elements with different angles, and brackets. The study shows that the performance of this kind of CFS lateral resistant system under cyclic loads is satisfactory; and can be considered reliable. A discussion on the calculated response factors in comparison to those suggested in the relevant codes of practice is also presented