Behaviour of high - rise steel buildings under lateral loads effects

Abstract

Design of high rise buildings is generally predicated on lateral forces like wind loads and earthquake loads. However high rise buildings are mostly reactive to dynamic oscillations due to wind loads because of having materials which are low in damping and lighter in weight. In this thesis, wind effects on high rise steel buildings designed with various outriggers and belt truss systems are examined and comparisons of results are presented. The buildings are analyzed according to the load specifications of American Society of Civil Engineers, Minimum Design Loads for Buildings and Other Structures 2010 and Turkish Earthquake Code 2007. The results and responses of buildings in both wind and earthquake loads are compared by taking account of these specification provisions. It is seen that lateral stiffness demand for the wind is more severe than earthquake along the long direction of buildings. Design wind speed is obtained from the results of a study including region-specific statistical analysis of wind data in Turkey. Wind load calculations and application procedures are given. Another important part of this study is to explain behavior of outrigger and belt truss systems on high rise buildings under wind loads. The location of the outrigger and belt truss systems has an immense influence on the efficiency of the structure. A three dimensional finite element analysis is performed with one, two and three outrigger levels. By changing the number and locations of outriggers on two buildings having different heights, structural analyses are carried out with SAP2000. The results are compared to demonstrate positive effects of outrigger and belt truss systems on lateral stiffness of buildings. Moreover, for giving a better understanding of the efficiency of outrigger when different structural outriggers are used in the buildings, three different structural outrigger systems are analyzed by using SAP2000 program and results are compared. All results, comparisons and calculations are given in this paper.