No abstract

A tension/compression device is developed for applications as bracing elements in buildings. The device is designed to allow Nitinol forms, such as helical springs or Belleville washers, to be used in compression. The device allows both overall extension (tension) and compression while subjecting the Nitinol to an optimum deformation mode. It is possible, due to the versatility of the design, to adjust the force and stroke of the device without changing the overall configuration. This new device is subjected to a cyclic loading protocol that tests the Nitinol elementÕs ability to recover large deformations. The effect of different Nitinol configurations and a cyclic loading history are evaluated in the study. The results show that Nitinol helical springs produce good recentering and damping behavior while Nitinol Belleville washers show good potential to form the basis for a Nitinol damping device.

No abstract

ASCE 41 is the industry standard for seismic evaluation and retrofit of existing buildings. It allows for alternative component modeling and acceptance criteria based on a backbone curve constructed from envelopes of component hysteresis loops derived via experimental cyclic tests. ASCE 41-13 requires use of loading protocols having fully reversed cyclic loadings with increasing displacement levels. However, recent research summarized herein indicates the need for inclusion of different protocols that pay specific attention to behavior incipient to collapse. This view is supported by example building computer earthquake response simulations described herein. A generalized loading pattern derived from the simulations found relatively few drift excursions having one-direction bias, suggesting one-sided cyclic and/or monotonic tests may be better for describing building inelastic seismic demands.

No abstract

No abstract

No abstract

PrefaceIn June 2008, the National Earthquake Hazards Reduction Program (NEHRP) sponsored a PerformanceBased Seismic Design (PBSD) workshop for leading practitioners and researchers from around the United States to develop a comprehensive list of research needs to foster full development and implementation of PBSD. From this workshop, the Building Seismic Safety Council (BSSC) reported a prioritized list of key PBSD research and implementation needs in NIST GCR 09-917-2: Research Required to Support Full Implementation of Performance-Based Seismic Design (NIST 2009a). The highest priority need identified in this report was to "benchmark" current PBSD methodologies (e.g., ASCE/SEI 41-06: Seismic Rehabilitation of Existing Buildings (ASCE 2006)-hereafter referred to as ASCE 41) with code procedures for design of new buildings. Two observations from the report were that among workshop participants (1) ASCE 41 procedures are perceived to be overly conservative and (2) existing PBSD methods are not accepted by practitioners as providing a uniform level of confidence. A supporting reason for these two observations was that no systematic effort had been undertaken to benchmark structural performance as determined using ASCE 41 procedures, together with widely accepted procedures for designing new buildings using ASCE/SEI 7-10: Minimum Design Loads for Buildings and Other Structures (ASCE 2010)-hereafter referred to as ASCE 7.Work was initiated at the National Institute of Standards and Technology (NIST) to support this priority study under the Assessment of Design Methods in Existing PBSD Standards Project. This task was conducted by the Earthquake Risk Reduction in Buildings and Infrastructure group, the research division of the NEHRP Office at NIST. This research involves problem-focused studies in PBSD assessing the applicability and accuracy of implementing first-generation PBSD analysis methods now used for evaluating existing buildings in the performance-based design of new buildings. The current study focuses on buildings with lateral systems utilizing structural steel frames. This project evaluates the results of the studies and identifies changes to current model building codes and standards provisions that will encourage more universal use of PBSD. The volume of data required to illustrate the results and conclusions necessitated three separate reports, as follows: A peer review panel (PRP) was engaged under a contract with the NEHRP Consultants Joint Venture (NCJV)-www.nehrp-consultants.org. The PRP was tasked to complement the NIST project by providing, where needed, individual subject matter expert guidance to improve the technical detail and outcome of the project; provide technical support on specific topics on seismic hazard analysis, ground motion scaling for iii varying return periods, nonlinear dynamic analysis, structural behavior and design of building structures; and provide peer review services. The review panel for this project was structured as follows: NCJV List of Tabl...