Date on Master's Thesis/Doctoral Dissertation

8-2011

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Civil and Environmental Engineering

Committee Chair

McGinley, William Mark

Author's Keywords

Seismic; Behavior; Brick veneer; Wall; Medium rise buildings; Systems

Subject

Walls--Testing; Masonry--Testing; Materials--Fatigue

Abstract

This dissertation presents an analytical investigation that examined the seismic performance of steel stud backed and Concrete Masonry Units (CMU) backed masonry veneer wall systems, under in and out - of - plane loads, in medium rise building frames. The investigation was prompted by recently observed damage to brick veneer wall systems due to strong earthquake and wind events. Prior research on these systems had focused on veneer walls built using older construction practices, or on residential wood stud backed veneer wall systems, or wall systems in low rise building frames. In this investigation, analytical models of the wall systems were attached to models of medium rise building frames, and the combined models were dynamically analyzed under the action of carefully selected ground motions, using the state of the art OpenSees framework. The preliminary designs of the building frames were performed on the STAAD.Pro software, according to American Building Code provisions. The member sizes were selected by the software using its inbuilt design algorithms, so as to be representative of those commonly used in earthquake resistant design in the United States, in regions falling under seismic category D. These members were then transferred into the OpenSees framework, on which the dynamic analysis was performed. The Sylmar and Tarzana ground motion histories were appropriately scaled and used in the dynamic analysis. A parametric study was conducted in order to understand the effect of different parameters on the response of the combined system comprising the veneer walls and the main building frame. The parameters were selected so as to create systems that represented the masses and stiffnesses of a vast majority of systems used in construction practice. For the mainframe systems, these included the steel moment resisting and braced frames, and the reinforced concrete moment resisting and shear wall systems. For the veneer wall systems, the parameters varied included the type of backing wall, namely, the steel stud backing wall and the eMU backing wall, and the type of tie system, namely, a stiff tie system and a flexible tie system. All the models developed in this investigation were calibrated against experimental results. During the calibration process, models were developed on OpenSees that replicated experimental observations and the model parameters were adjusted till the results predicted by the models closely matched observations. To begin with, the results of this investigation describe the effect of modeling the wall systems, under in and out - of - plane loads, as their representative masses, and as analytical models, on the frame systems, at the Design Based Earthquake (DBE) and Maximum Considered Earthquake (MCE) levels of the Sylmar and Tarzana ground motions. Subsequently, they describe the effect of the mainframes on the veneer wall systems, under out-of-plane loads, at the MCE level of the same ground motions. Finally, the results of a collapse analysis of the wall systems under out - of - plane loads is presented, showing the intensity of the ground shaking which caused failure of the wall system, and the reason for the observed failure.

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