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The Newmark Structural Engineering Laboratory (NSEL) of the Department of Civil and Environmental Engineering at the University of Illinois at Urbana-Champaign has a long history of excellence in research and education that has contributed greatly to the state-of-the-art in civil engineering. Completed in 1967 and extended in 1971, the structural testing area of the laboratory has a versatile strong-floor/wall and a three-story clear height that can be used to carry out a wide range of tests of building materials, models, and structural systems. The laboratory is named for Dr. Nathan M. Newmark, an internationally known educator and engineer, who was the Head of the Department of Civil Engineering at the University of Illinois and the Chair of the Digital Computing Laboratory . He developed simple, yet powerful and widely used, methods for analyzing complex structures and assemblages subjected to a variety of static, dynamic, blast, and earthquake loadings. Dr. Newmark received numerous honors and awards for his achievements, including the prestigious National Medal of Science awarded in 1968 by President Lyndon B. Johnson. He was also one of the founding members of the National Academy of Engineering. Contact ABSTRACTThe current AISC Specification for Structural Steel Buildings (AISC, 2005a) is the lead specification for composite construction in the U.S. However, these provisions do not provide a recommendation for computing the strength of headed steel stud anchors (traditionally used as shear connectors) under tension or combined tension and shear. Headed stud anchors are subjected to these types of forces in composite structures such as infill walls, composite coupling beams, the connection region of composite columns, or composite column bases. While ACI 318-08 Appendix D (ACI, 2008) and PCI 6th Ed. (PCI, 2004) includes provisions for such conditions, those provisions are geared for more general anchorage conditions than are typically seen in composite construction. It would thus be beneficial to have design guidance specifically for the case of headed steel stud anchors subjected to tension or combined tension and shear in composite construction, evaluated within the context of the AISC Specification. In this work, different strength equations to compute the nominal tensile strength of a headed stud are reviewed and compared to experimental results. The resulting recommendations seek to ensure a ductile failure in the steel shank instead of a brittle failure within the concrete. Several criteria are proposed to ensure that a ductile failure controls in composite construction, and, different headed stud configurations and detailing reinforcement recommendations are proposed to improve the ductile behavior of headed stud anchors subjected to tension and combined tension and shear.

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There has been widespread interest in the development and use of self-centering (SC) lateral resisting systems that eliminate residual drifts after large earthquakes. SC systems often include a restoring force component and a component that dissipates seismic energy. Typically, it is assumed that the criterion for self-centering is satisfied if the restoring force is proportioned to be greater than the force required to yield the energy dissipating component. A parametric SDOF study was conducted using time-history analyses on several prototype buildings to quantify the effect of varying system parameters on structural response including residual drifts. The ambient resistance of the rest of the building was considered, as well as proportioning the system with less restoring force than the yield capacity of the dissipative component. In addition, the probabilistic mechanism that creates a propensity for reducing residual drifts in systems with little or no restoring force is explored and quantified. It was found that a restoring force that is at least one-half of the force required to yield the dissipative component will still reliably eliminate residual drifts in a non-softening system.