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Hybrid masonry connector plate and headed stud small-scale wall testing

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Item Summary

Title: Hybrid masonry connector plate and headed stud small-scale wall testing
Authors: Aoki, James Mitsunori Katsuki
Keywords: wall testing
hybrid masonry connector plate
Issue Date: Dec 2012
Publisher: [Honolulu] : [University of Hawaii at Manoa], [December 2012]
Abstract: Hybrid masonry is a new seismic structural system which involves structural steel frames with concrete masonry unit (CMU) walls. The CMU walls serve as shear walls to replace traditional steel bracing. They have different functions depending on the type of hybrid masonry. The CMU walls are either used to transfer only lateral loads through the height of the structure or lateral and gravity loads. Type I Hybrid Masonry uses the CMU walls to resist only in-plane lateral loads. In Type II Hybrid Masonry the CMU walls are also used to support vertical loads. Using the CMU walls as a gravity member, the steel beams in the frames can be reduced resulting in a lower construction cost. In Type III Hybrid Masonry the CMU walls act as the web of a composite shear wall with the steel columns as boundary elements for columns.
Drs. Ian Robertson and Gaur Johnson, along with graduate student researchers Seth Goodnight, Reef Ozaki-Train, and Steven Mitsuyuki have designed and tested prospective connector plates to develop connectors that can transfer lateral loads. The first type tested was the ductile fuse connector, which was designed to transfer many cycles of lateral load for Type I Hybrid Masonry. During cycling, the fuse connector plates dissipated energy caused by the simulated seismic activity. The fuse connector possessed the capability to dissipate large amounts of energy and allowed relatively large deflections without damaging the CMU wall. This ductility is an advantage because only the fuse connector plates must be replaced after a seismic event. The second type of connector that was tested was a link plate, which was designed as a uniform plate with no fuse section. These link plates were designed to transfer higher lateral loads than the fuse connector. Rather than allowing large displacements by yielding, this connector plate provided a rigid system that transferred the lateral loads to the CMU infill wall which must be designed for ductile response.
In Type I Hybrid Masonry the transfer of in-plane shear from the fuse or link plates to the CMU panel utilizes bolts which pass through the CMU wall and vertical slotted holes in the connector plates on either side of the wall. These through bolts must not be the weak link in the Hybrid Masonry system since failure of the bolts in shear or masonry break-out could represent a non-ductile response that is not suitable for seismic design.
This report presents the results of eleven bolt push-out tests were performed on six 8" thick grouted CMU walls to evaluate the performance of the through bolts. Based on these tests a number of conclusions were drawn and recommendations are provided for design of through bolted connections.
Type II Hybrid Masonry utilizes headed studs to transfer shear from the steel floor beam to the CMU shear panel below. Type III Hybrid Masonry utilizes headed studs to transfer shear from both the steel floor beam and the columns to the CMU shear panel. Three fully grouted 8" thick CMU walls were tested to evaluate the performance of headed studs at different spacings in these connections. In all cases, the headed studs were ¾" diameter by 6" long, welded to the bottom of the floor beam bottom flange. They were embedded in a 9" high by 7-5/8" thick grout beam on top of the 8" CMU wall. The top course of the CMU wall was a bond beam with one #4 bar and the wall vertical reinforcement consisted of #4 bars at 24" on center. Conclusions and + recommendations are presented based on the results of these tests.
Description: M.S. University of Hawaii at Manoa 2012.
Includes bibliographical references.
Appears in Collections:M.S. - Civil and Environmental Engineering

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