Experimental Investigation of the Seismic Performance of Retrofitted Masonry Flat Arch Diaphragms

Abstract

Masonry flat arch diaphragm that developed in Britain is still in use in parts of Europe, North America, the Middle East, and Indian subcontinent. The damage of a large number of these diaphragms during past earthquakes all around the world highlighted the need for developing an appropriate retrofitting method. In this study, the in-plane seismic behavior of ordinary and the retrofitted brick flat arch diaphragms are experimentally investigated. Eight full-scale experiments were conducted under cyclic loading. Perpendicular and parallel loads were applied to the steel I-cross beams of the masonry flat arch diaphragms. The experimental models consisted of two frames of masonry flat arch diaphragms in the absence of brick flat arch, two ordinary masonry flat arch diaphragms with steel tension ties in end arch spans as prototype, two masonry flat arch diaphragms without and with steel tension ties in diaphragm span, and two retrofitted masonry flat arch diaphragms with simultaneous use of steel diagonal bracing and steel tension ties in end arch spans. The results of the experiments demonstrate that the ordinary masonry flat arch diaphragms have insufficient shear capacity and integrity. However, among the retrofitted models, the simultaneous use of diagonal bracing and steel tension ties in end arch spans improved the overall seismic performance, integrity, and ductility of the masonry flat arch diaphragm. Moreover, the stiffness and shear capacity of this diaphragm increased up to 108 and 88%, respectively. The findings of this study recommend the use of simultaneous diagonal bracing and steel tension ties in end arch spans for retrofitting the ordinary masonry flat arch diaphragms.