Brick veneer walls are expected to perform satisfactorily under various serviceability and ultimate conditions including wind driven rain, high wind loads, earthquakes, and in some cases, blast. Conventional brick veneer with steel stud backup is a popular type of construction for most non-residential buildings because of the advantages that the light weight steel stud construction offers. However, high wind loads and wind driven rain can potentially cause cracking of the veneer and corrosion of metal ties. Innovative solutions can address these and other concerns and expectations including design against blast loads and appropriateness of the design for performance based design methodology. A novel panelized brick veneer on steel stud backup (PBVSS) wall system has been under development at Penn State University to address multi-hazard load resistant design. While the preliminary design of the PBVSS concept has resulted in a promising panelized brick veneer wall system, refinements are needed to satisfy objectives such as rain screen design with pressure moderation, prevention of air leakage through panel-to-panel joints, water-tight interface of flashing and shelf angle shear keys, optimization of the structural frame part of the panelized system, and development of blast resistant design methods. The research will consists of a major experimental component and an analytical task, which involves development of a three-dimensional finite element modeling capable of capturing composite behavior and to be calibrated using test results. Full-scale experiments on PBVSS wall specimens under out-of-plane simulated high wind loading and also wind driven rain loading, in-plane earthquake simulated racking and out-of- plane ultimate capacity static loading will be conducted.
The project will have a positive impact on prefabrication of building components with better quality and minimizing on-the-site construction, which will bring overall savings for the projects. It will also reduce scaffolding related accidents. Opportunities will be provided for undergraduate students (including female students) to work on the proposed project. An extra effort will also be made to recruit a qualified minority student. The PI will work with International Masonry Institute instructors toward training masonry contractor for construction of PBVSS wall system. Finally, the results of the study including video clips of tests will be made available to the public through PI's webpage.
Project CMMI-0653985, Ali M. Memari, Principal Investigator A novel panelized brick veneer on steel stud backup (PBVSS) wall system has been under development to address multi-hazard load resistant design. The basic concept of the PBVSS consists of a rolled steel backup frame, light gage steel studs, plywood or oriented strand board (OSB) sheathing, rigid foam insulation, air and vapor barriers, shear ties, brick veneer and interior grade gypsum wall board. The wall panel also eliminates the costly, conventional, lay-on-the-job construction process of brick veneer on steel stud walls. The proposed PBVSS provides the flexibility needed to design for various desirable performance levels, such as minimum potential for brick veneer crack under high wind loads, seismic isolation from the structural frame for in-plane movements to prevent wall damage, and enhanced resistance against blast loads with debris retention potential. The primary objective in this project was to develop ways to construct brick veneer wall systems with greater strength to provide safety under extreme loading conditions. This project has introduced several enhancement techniques, including three techniques to enhance steel stud backup resistance and three methods to increase the brick veneer resistance. With respect to steel stud strengthening, the three methods include 1) strengthening stud connections to horizontal members, 2) using light gage sheet metal in addition to the OSB sheathing and drywall to integrate the steel studs, and 3) using gypsum wallboard that has a sheet metal attached to the gypsum wallboard and use it instead of drywall and OSB sheathing. With respect to brick veneer strengthening, three methods were explored: 1) using steel rebars vertically in the cores of the brick veneer and horizontally at bed joints, 2) using fiber reinforced polymers (FRP) on the interior face of the brick veneer, and 3) using polyurea on the interior face of the brick veneer. Current design and construction of steel stud backup system consists of connecting studs to the light gage tracks using screws, which yield weak connections. Because of the use of rolled steel framing members at top and bottom of the panel in the proposed system, the studs are attached to the rolled steel channels using steel plates welded to the channels and bolted to the stud webs. The second method of steel stud strengthening considered attaching sheet metal on both interior and exterior sides of the studs in order to create membrane action under lateral loading conditions. The third approach of enhancing the steel stud backup system consisted of using commercially available gypsum wallboard with sheet metal laminate (Sure Board) to replace the conventional drywall on the interior side of the studs (using interior grade Sure Board) and to replace the conventional OSB sheathing on the exterior side of the studs (using exterior grade Sure Board). The reinforcing bars were added to the brick veneer in the form of horizontal bed joint pencil rods that would clip into seismic veneer anchor pintles. For vertical reinforcement, # 3 rebars were added at the midpoint between brick veneer ties that were attached to the studs. In this project, an air bladder testing facility was constructed to carry out the out-of-plane loading tests. The test results show that using sheet metal enhancement techniques in general increased the strength of the wall due to tension membrane by about 25%. For a given pressure level, the deflection was reduced. In application of composites, (FRP and polyurea), the test results showed that the out-of-plane load capacity of specimens enhanced with vertical FRP strips or polyurea can be increased by about 20%, while that for a grid pattern of FRP can increase the capacity by about 25%. The cap on strength enhancement was partly due to the weakness of masonry shear ties that anchor the brick veneer to the steel studs. While this inherent weakness of ties shown when they collapse limits the strength of the wall to some degree, it is beneficial in the sense of dissipating and absorbing the energy imparted to the wall by the applied pressures, and this provides a better overall performance. The other important effect of adding the composites is to retain the debris and turn the brittle brick veneer wall into a more flexible and ductile system. The project will have a positive impact on prefabrication of building components with better quality and minimizing on-the-site construction, which will bring overall savings for the projects. It will also reduce scaffolding related accidents. Some photos taken during the project are shown below.
