Static Analysis of Tall Buildings Using Member-Groups

An approximate displacement method for three-dimensional analysis of tall reinforced concrete buildings is described in Ref. 2. Floors, subsequently called nodal floors, are selected between which only minor changes in the formwork are to occur. Only nodal floors are described in the computer input. However, at every floor level constraints are imposed that permit columns and walls to be treated in the same general manner. A building stiffness matrix with a fraction of the natural degrees-of-freedom is assembled using one component matrix for each member-group of vertically adjacent similar members. For preliminary analysis, sufficient nodal floors are selected to model the major irregularities in stiffness; average member properties are used within each member-group. For final analysis, more detail and accuracy are obtained by adding nodal floors in the preliminary mathematical model. In the previous paper, natural modes and periods for approximate models are compared to those of the detailed model for which the building is idealized as a system of individual members. Herein, the results of approximate and detailed static analyses will be compared.