Second-Order Effects on Wind-Induced Structural Behavior of High-Rise Steel Buildings

Abstract

This paper investigates second-order effects on wind-induced structural dynamic behavior of a 6-story high-rise steel structure known as the Commonwealth Advisory Aeronautical Research Council (CAARC) building model. These effects are considered in the structural analysis by using a geometric stiffness method allowing the dynamic analysis to be performed without iterations. Data sets of the aerodynamic pressure on the CAARC building model for suburban exposure are used in the database-assisted design (DAD) procedure to calculate, in addition to overturning moments and shear forces at the base, members’ demand-to-capacity indexes (DCIs), interstory drift ratios, and resultant accelerations. Dynamic analyses are performed using four reference mean hourly wind speeds at the rooftop for suburban terrain exposure (Uref=2 and 4 m/s for serviceability analysis, and 6 and 8 m/s for strength analysis). The second-order effects decrease natural frequencies of vibration of the building by up to 12%. In the strength analysis with Uref=8 m/s, second-order effects increase nondirectional peak global responses by up to 15% for overturning moments, 9% for base shears, and 1% for torsional moments. The responses of 21 members selected in this study are increased by up to 19% for columns, 41% for beams, and 31% for diagonal bracings in the case of the DCIs for the interaction of axial forces and bending moments (BijPM) and by up to 67% for columns, 26% for beams, and 13% for diagonal bracings in the case of the DCIs for the shear forces (BijV). In the serviceability analysis with Uref=4 m/s, second-order effects increase the interstory drift ratios by up to 17% and the resultant accelerations at the top floor by up to 2%. This case study shows that the second-order effects can considerably affect not only drift control but also the design of members for strength.