Structural Walls: New Modeling Parameters for Seismic Retrofit

Abstract

The nonlinear backbone modeling parameters and acceptance criteria in ASCE/SEI 41-17 and 369-17 for structural concrete walls were developed based on limited experimental data and knowledge available in the late 1990s (FEMA 273/274-1997), with only minor revisions since. As a result, the wall provisions tend to be, in many cases, inaccurate and conservative, and thus can produce uneconomical retrofit schemes. This study utilizes available experimental data and new information on performance of structural walls to develop updated modeling parameters and acceptance criteria for flexure-, diagonal shear-, and shear-friction-controlled walls. To accomplish these objectives, a recently developed comprehensive wall database was utilized, which currently contains detailed information and test results from more than 1100 wall tests. The proposed updates include a new approach to identify expected wall dominant behavior (failure mode), cracked and uncracked flexural and shear stiffness values, and updated backbone modeling parameters and acceptance criteria. The updates, which either have been approved or are currently being balloted for adoption in ACI 369 (and for eventual inclusion into ASCE 41-23), are expected to significantly contribute to the practice of seismic evaluation and retrofit of wall buildings.