Incorporation of steel frames in masonry buildings for reduction of earthquake-induced life loss

Abstract

This paper describes the seismic retrofit of masonry structures by introducing some steel moment resisting frames within the buildings. The intent is not to improve the seismic performance of masonry structures but to present protective steel shells within the structures that provide protection from loss of life. The main idea is that occupants can seek refuge within the steel frames as soon as the earthquake ground motions are felt. The steel frames do not carry any service loads before an earthquake. However, if a near field seismic event happens and the load bearing walls of the buildings are destroyed, some parts of their floors, which are in the retrofitted areas, will fall on the roof of the installed frames; consequently, the occupants who have sheltered in these areas will survive. This paper expresses the experimental work to assess the seismic performance of moment resisting steel frames in masonry buildings, and also it compares the test results with those obtained from linear time history and nonlinear pushover analyses. For time history analysis, the 1940 El Centro, 2003 Bam, and 1990 Manjil earthquake records scaled at the maximum peak ground acceleration assumed by the Iranian Technical Standards, equal to 0.35 g, were utilized as inputs. The results of experimental work, time history and pushover analyses show that the strength and displacement capacity of the steel frames are adequate to accommodate the distortions generated by seismic loads and aftershocks.