Selected Research Projects
NSF PFI:AIR-TT "Innovative High-Performance Cold-Formed Steel Wall System for Light Framed Construction"
PI: Dr. Cheng Yu, UNT; Co-PI: Jeff Martin, Verco Decking Inc.
Sponsor: National Science Foundation.
Period: August 2014 - January 2016
Award Number: 1445065
This PFI: Accelerating Innovation Research (AIR) Technology Translation (TT) project focuses on translating a research discovery on the use of perforated corrugated steel decks as sheathing to fill the need for non-combustible high-performance shear walls for mid-rise light-framed buildings. Mid- and low-rise buildings comprise the majority of buildings in the United States. The mid-rise multi-family homes (4-9 stories) are becoming the housing trend to meet the increasing demands of population growth and urbanization. The use of cold-formed steel (CFS) would be highly cost-effective for mid-rise light-framed buildings. However the existing shear wall technologies impede the use of CFS in mid-rises due to the requirements of non-combustibility and high structural performance (shear strength, stiffness, ductility). The project will result in a prototype of the proposed non-combustible high-performance steel shear wall technology. This new technology has the following unique features: a) it uses the perforation in the sheathing as energy dissipating fuses to achieve high ductility; b) it uses the corrugation in the sheathing to achieve high strength and stiffness; c) it uses only CFS members; d) the sheathing to framing connection method is optimized for high efficiency; e) it has the same thickness as the non-shear walls; and f) it enables the engineers to control the damage locations to be away from critical building components. These features provide the following advantages over the current state-of-the-art technologies: higher structural performance, lower overall cost, non-combustibility, and controllable failure mechanism when compared to the leading competing technologies, namely the wood based panel shear wall, the steel sheet shear wall, the steel-gypsum composite panel shear wall, and the diagonal steel strap bracing shear wall in the mid-rise construction market.
This project addresses the following technology gaps as it translates from research discovery toward commercial application. It will investigate the feasibility of positioning the corrugated deck within the CFS frame in order to form standard wall thicknesses while maintaining high structural performances. A major research effort will be made to maximize the shear wall performance by developing optimal parameters in perforation, corrugation, and CFS framing details via numerical simulations and full-scale experiments. In addition, personnel involved in this project, undergraduate and graduate students, will receive innovation and technology translation experiences through modeling, building, and testing CFS shear walls. The potential economic impact is expected to be significant for the mid-rise construction industry, which will contribute to the U.S. competitiveness in building industries.
The project involves research collaboration between the University of North Texas and two industrial partners, Verco Decking Inc. and Nucor Building Systems. The industrial partners will provide deck manufacturing capacities, assist in developing an efficient connection method, and guide commercialization aspects in this technology translation effort.
NSF CAREER Award "CAREER: Comprehensive Research on Cold-Formed Steel Sheathed Shear Walls: Special Detailing, Design, and Innovation"
PI: Dr. Cheng Yu
Sponsor: National Science Foundation. NSF Program: CMMI - HAZARD MIT & STRUCTURAL ENG
Period: September 2010 - August 2015
Award Number: 0955189
The research objective of this Faculty Early Career Development (CAREER) project is to close the knowledge gaps about the behavior of cold-formed steel lateral force resisting systems that use shear walls sheathed with steel or wood panels. The study includes three major tasks: 1) Configuring a unique testing method designed to investigate the performance of cold-formed steel shear walls under realistic loading conditions to provide reliable experimental data to evaluate the current code prescribed shear wall strengths. 2) Based on the experimental data, establish accurate analytical models to predict the shear strength of cold-formed steel shear walls made with different sheathing materials and to provide design equations based on the principles of mechanics and mathematical models. 3) Develop advanced designs of high-performance shear wall systems with enhanced ductility and strength for low cost building constructions in seismic and strong wind zones.
The results of this research will provide simplified and improved methodologies for safe and more economical design of building structures using the cold-formed steel shear walls which are known to be recyclable and provide better fire resistance compared to wood construction. This research will also make it feasible to use the cold-formed steel walls in taller buildings than what has been possible now in seismic and high wind regions. The educational activities of the project with the developments of hands-on experiments and teaching aids and a comprehensive text book will lead to improvements in teaching about the cold-formed steel structures to both graduate and undergraduate students. This will also promote professional interest in the use of this economical and sustainable method of building construction. Graduate students will receive advanced training in research methods through their direct involvement in the project research. The research results will be disseminated through publications in professional journals and conference proceeding as well as through a project website.
Research details and progress reports are provided in the NSF-CAREER site. Link to the NSF-CAREER project website.
Performance and Detailing of Cold-Formed Steel Framed Shear Walls using Corrugated Steel Sheathing
PI: Dr. Cheng Yu
Sponsor: American Iron and Steel Institute, National Science Foundation (through CAREER award)
Period: 2008 - Present
This is an ongoing project aimed at investigating the appropriate framing and sheathing details for cold-formed steel framed shear wall using corrugated steel sheathing. Initial study shows that the corrugated steel sheathing offers significantly improved stiffness and strength compared to flat sheet steel sheathing. The research continues to focus on ductility issues and seismic performance of those unconventional cold-formed steel shear walls.
CUREE Cyclic Test on a 4'x8' CFS Shear Wall using Corrugated Steel Sheathing
Steel Sheet Sheathing Options for Cold-formed Steel Framed Shear Walls Assemblies Providing Shear Resistance - Phase I and II
PI: Dr. Cheng Yu
Sponsor: American Iron and Steel Institute, Steel Stud Manufacturers Association
Period: 2007 - 2009
Phase I - In cold-formed steel construction, stud walls covered with steel sheet sheathing is an available option to resist lateral loads such as those caused by wind and earthquakes. The current American Iron and Steel Institute (AISI) Standard for Cold-Formed Steel Framing - Lateral Design 2004 Edition provides nominal shear strength for a limited range of steel sheet sheathed shear wall configurations. This research project was developed to add values for 0.030-in. and 0.033-in. steel sheet sheathed shear walls with 2:1 and 4:1 aspect ratios and 0.027-in. sheet steel shear walls with 2:1 aspect ratio and 6-in., 4-in., 3-in., and 2-in. fastener spacing at panel edges. For all specimen configurations, the steel sheet sheathing was installed on one face of the wall. The test program consisted of two series of shear wall tests. The first series focused on determining the nominal shear strength for wind loads for which monotonic tests in accordance with ASTM E564 standard were performed. The second series of tests addressed the nominal shear strength for seismic loads for which the reversed cyclic tests using CUREE protocol were conducted. The research was sponsored by AISI and SSMA, and was performed at University of North Texas.
Phase II - Monotonic and cyclic tests on cold-formed steel shear walls sheathed with steel sheets on one side were conducted to (1) verify the published nominal shear strength for 18-mil and 27-mil steel sheets; and (2) investigate the behavior of 6-ft. wide shear walls with multiple steel sheets. This project is the continuation of a completed project titled Steel Sheet Sheathing Options for Cold-Formed Steel Framed Shear Wall Assemblies Providing Shear Resistance by Yu (2007). This Phase 2 project confirms the discrepancy in the published nominal strength of 27-mil sheets discovered by the Phase 1 project, and proposes new values. The project also finds disagreement on the nominal strength of 18-mil sheets for seismic design, which requires further research. For the 6-ft. wide shear walls, this project indentifies special seismic detailing to prevent potential damage on studs while improving the strength and ductility of the shear walls. This report provides detailed information on the test setup, test results, and analyses.
Phase 1 report available on AISI website. link to phase 1 report.
Phase 2 report available on AISI website. link to phase 2 report.
CUREE Cyclic Test on a 6'x8' CFS Shear Wall using Steel Sheet Sheathing
Cold-formed Steel Bolted Connections using Oversized Holes without Washers - Phases I and II
PI: Dr. Cheng Yu
Sponsor: American Iron and Steel Institute, Metal Building Manufacturers Association
Period: 2007 - 2009
In cold-formed steel (CFS) construction, bolted connections without washers for either oversized or slotted holes may significantly expedite the installation process and lower the cost. The North American Specification for the Design of Cold-Formed Steel Structural Members requires washers to be installed in bolted connections with oversized or slotted holes. A two phase research project sponsored by American Iron and Steel Institute was recently completed at the University of North Texas (UNT) that investigated the performance and strength of bolted CFS connections with oversized and slotted holes without using washers. The bolted CFS connections were studied in a broader respect in terms of the failure mechanism, the material thickness, and the hole configurations. Combined with Phase 1 results, the Phase 2 report gives a comprehensive evaluation of the behavior and strength of bolted CFS connections with oversized and slotted holes without using washers. Revisions to the existing AISI North American Specification requirements for bolted connections are proposed to account for the reduction in the connection strength caused by the oversized and slotted hole configurations without washers.
Phase 1 report available on AISI website. link to Phase 1 report.
Phase 2 report available on AISI website. link to Phase 2 report.
Evaluation of Stiffback System for Monolithic Placement of Ecospan Joist on Insulated Concrete Form (ICF) Walls
PI: Dr. Cheng Yu
Sponsor: Nucor R & D
Period: 2008 - 2009
The objective of this project is to experimentally investigate the axial load bearing capacity and deflection of the cold-formed stiffback under a dead load on scaffold, a wind load, and a combination of two loads. Two stiffback thicknesses were investigated: 16 gauge and 14 gauge. The test program was focused on the stiffback with full height. However smaller height of stiffbck was also studied in this test program.
Behavior and Performance of Steel Moment Frame under Cyclic Loading
PI: Dr. Cheng Yu
Sponsor: BORM Associates.
Period: 2007 - 2008
The research objective of this project is to investigate the structural performance of BORM standard moment frame under cyclic loadings (CUREE loading protocol) by the finite element method. The research results support the development of a full scale cyclic test program on those specially designed steel moment frame.
See complete list of funded research projects in Dr. Yu's CV.