Static Non-linear Analysis (Pushover) Of Composite Special Moment Frames (C-SMF)

Abstract

In the present research work, a non-linear model of concentrated plasticity of multi-story prototype buildings is presented, the cross sections of the beams and columns are illustrated with the respective amount of fibers to be used per element, as well as the corresponding effective curves stress-strain models used for both steel and concrete along with the hysteretic degradation model for each material. A non-simulated collapse criterion of maximum plastic rotation of 0,05 [rad] is defined for both the beams and columns, a minimum monitored displacement of 0,05 H is defined, as well as the lateral load pattern and the combination of gravitational loads. From this, the pushover analysis is carried out in the SAP2000 software to determine the capacity curve, the overstrength factor and the ductility of the structures.

 The static nonlinear analysis (Pushover) carried out show that all the prototypes have an adequate ductility (ductility less than 8 and greater than 3); Furthermore, the overstrength factor remains constant for heights between 6, 8 and 12 stories. For heights equal to 3 stories, the overstrength factor increases and for 16-story buildings a notable reduction of this factor can be seen. The fact that there is a high overstrength is due to the drift control established by NCh 433, to the width-thickness relationships and to the capacity design of AISC 341 (strong column-weak beam), which leads to large oversizing.