EQUIVALENT MASS-SPRING MODELING METHOD FOR SUPER-TALL BUILDINGS OF INCREASING HEIGHT (PART 1)： OVERVIEW OF PAST AND PROPOSED METHODS FOR BENDING-SHEAR MODEL

Abstract

 When a super tall building is designed, a member-to-member model is constructed to represent the assembly of columns and beams. The response history analysis using member-to-member model, however, is computationally expensive and produces excessive amount of data that are not necessary at the preliminary design stage. Therefore, an equivalent mass-spring model with a small number of elements and short analysis time is useful at the initial design stage. It promotes accurate and quick decision on the overall performance and economy of the super tall building at the critical stage where many different design options are explored. In addition to the shear deformation typically considered, bending deformation becomes large as building becomes taller, which must be simulated by the equivalent mass-spring model. In this paper, we propose a new modeling method for an equivalent mass-spring model, the so-called “bending-shear model” that can accurately reproduce the dynamic characteristics of the building by using the information obtained from the member-to-member model. The bending stiffness and shear stiffness are calculated so that the 1st mode frequency and vector as well as the 2nd mode frequency of the bending-shear model match with those of the member-to-member model. Instead of typical static lateral load, pure bending moment is applied to the member-to-member model, and bending stiffness is estimated and calibrated for the bending-shear-model. The displacement and acceleration responses of the bending-shear model agree well with those of the member-to-member model.