Cyclic In-Plane Lateral Load Testing of Masonry Infill Walls with Structural Fuse Elements

Open Access
Author:
Kauffman, Andrew Lynn
Graduate Program:
Architectural Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
November 13, 2009
Committee Members:
  • Ali M Memari, Thesis Advisor
Keywords:
  • structural fuse
  • masonry infill walls
  • cyclic
Abstract:
Masonry infill walls are a common building element found in many areas of the world. Masonry infill panels have beneficial thermal and acoustic insulating properties and are often used for interior partitions as well as exterior walls. The structural properties of masonry infill walls, however, are often overlooked. In common practice, infill walls are treated as architectural elements and their influence on the behavior of the structural frame is not considered during design. Ignoring the contribution of masonry infill walls to the stiffness and response of building structures can lead to uneconomical design as well as unexpected behavior and even catastrophic collapse. Masonry infill walls increase the stiffness of structural frames and help to limit building deflections under normal lateral loads such as wind and small seismic events. Not accounting for the stiffness of infill walls in the design of infilled frames, however, can result in damage to the infill material and non-ductile frame behavior during large seismic events. A new concept in the performance and design of masonry infill walls is the idea of a structural fuse system. This seismic isolation system allows for composite interaction between infill walls and the structural frame under normal lateral loads. Brittle failure of the infill walls or frame elements is prevented by the introduction of a fuse mechanism, which isolates the infill material from the frame under higher loads. The primary objectives of this research program were to study the behavior of the structural fuse system under cyclic loads and to evaluate the performance of the system for use with various masonry materials. Additional objectives were to evaluate the performance of lumber disk fuse elements as a viable option for use in a fuse mechanism seismic isolation system, and to determine the shear and compressive strengths of the masonry materials used in the parametric study. A new experimental program was developed and executed to accomplish these goals. Cyclic tests were performed by applying simultaneous, displacement controlled loads at the first, second, and third stories of a two-bay, three-story steel test frame with brick infill walls; using a quasi-static loading protocol to create a first mode response in the structural system. A parametric study was also completed by replacing the brick walls with infill panels constructed of other masonry materials including concrete masonry units (CMU) and autoclaved aerated concrete (AAC) blocks, and applying monotonically increasing, displacement controlled loads to the test frame. During these tests, in-plane damage was not observed in the brick, CMU, or AAC infill walls. The results of this study showed that the lumber disk structural fuse elements worked well as seismic isolation devices. Based on the provisions of the Masonry Standards Joint Committee, MSJC (2008), equations were developed for determining the nominal in-plane strength of infill walls constructed of various masonry materials. The in-plane wall capacities predicted by these equations were compared to the results of destructive wall panel shear tests that were performed as part of this testing program. A simplified macro model was developed using SAP2000, and compared to the results of the monotonic tests. This approach was evaluated for use in the design office. It was determined that a more rigorous analytical technique is required to successfully capture the in-plane behavior of the structural fuse system.