Proposed Update to Masonry Provisions of ASCE/SEI 41: Seismic Evaluation and Retrofit of Existing Buildings

Abstract

This paper summarizes significant updates to the Masonry Provisions now undergoing public balloting for the 2013 revision of the standard ASCE/SEI 41: Seismic Evaluation and Retrofit of Existing Buildings. These updates are informed by performance observations of unreinforced masonry (URM) buildings in the recent Christchurch (New Zealand) earthquakes and recent research, including component testing. New evaluation provisions include the classification of bed joint sliding and stair-stepped bed joint sliding as deformationcontrolled modes of behavior. Provisions to evaluate diagonal tension strength are reintroduced from precursors to the standard. The provisions for rocking walls and piers are also substantially revised, to explicitly consider strength and stiffness degradation, and deformation capacities based on testing and other rational limit states. Guidance is also provided via commentary for the effects that flanges and spandrels have on in-plane wall or pier response. The wall anchorage provisions are proposed to be expanded to address chemical adhesive anchors in conjunction with installation quality assurance requirements. The performance criteria for out-of-plane wall actions are updated based on a review of currently available research. Improved modelling guidance is also provided via commentary to address the unique modeling and evaluation limitations that apply to URM buildings, including their resilience relative to other types of construction, as supported by performance observations from recent major earthquakes.