Simpson Gumpertz & Heger Inc.

About: Simpson Gumpertz & Heger Inc. is a based out in . It is known for research contribution in the topics: Finite element method & Beam (structure). The organization has 251 authors who have published 298 publications receiving 3243 citations.

Displacement-Based Design of Slender Reinforced Concrete Structural Walls—Experimental Verification

Abstract: Application of displacement-based design for slender structural walls results in predictions for the wall normal strain gradient derived from estimating the wall neutral axis depth and maximum compressive strain at the wall boundary, for a given top displacement. Based on this strain distribution, requirements for special boundary element transverse reinforcement are assessed. A simplified applica- tion of displacement-based design was incorporated into ACI 318-99 to evaluate detailing requirements at wall boundaries. The results of experimental studies of moderate-scale, slender wall specimens with rectangular-shaped and T-shaped cross sections are used to verify results predicted using displacement-based design. Detailing at the boundaries of the wall specimens, which were subjected to monotoni- cally increasing reversed cyclic lateral loads and constant axial load of approximately 0.10 Ag f c , were varied to assess behavior for a variety of conditions. Findings indicate good agreement between predicted and measured strain ~curvature! distributions for a range of drift levels, verifying that displacement-based design is both a powerful and flexible tool for assessing wall detailing requirements.

Building Design for Abnormal Loads and Progressive Collapse

Abstract: : A progressive collapse is a structural failure that is initiated by localized structural damage and subsequently develops, as a chain reaction, into a failure that involves a major portion of the structural system. The collapse of the Ronan Point Tower in Canning Town, London, United Kingdom in May, 1968 prompted numerous efforts to develop structural design criteria for progressive collapse resistance. A series of papers and reports appeared in the decade following the Ronan Point collapse, and attempts were made to implement provisions addressing progressive collapse and enhancing general structural integrity in codes and standards. Improved building practices and design procedures to control the likelihood of progressive collapse now are receiving heightened interest by engineers, architects, and standards organizations in the aftermath of the tragedy of September 11, 2001. Advances in the science underlying structural design and the development of structural reliability and risk analysis tools now permit design strategies that would have been considered infeasible 30 years ago. This article provides a critical appraisal of key research products that provide a basis for designing a structural system to withstand local damage without the development of a general structural collapse, and identifies strategies that currently are feasible to implement in the General Design Requirements in ASCE Standard 7, minimum design loads for buildings, and other structures. The article concludes with a discussion of research challenges to further enhancement of design practices, with particular emphasis on needed support for structural engineering analysis and design from advanced computation and information technologies.

Continued fraction absorbing boundary conditions for convex polygonal domains

Abstract: Continued fraction absorbing boundary conditions (CFABCs) are highly effective boundary conditions for modelling wave absorption into unbounded domains. They are based on rational approximation of the exact dispersion relationship and were originally developed for straight computational boundaries. In this paper, CFABCs are extended to the more general case of polygonal computational domains. The key to the current development is the surprising link found between the CFABCs and the complex co-ordinate stretching of perfectly matched layers (PMLs). This link facilitates the extension of CFABCs to oblique corners and, thus, to polygonal domains. It is shown that the proposed CFABCs are easy to implement, expected to perform better than PMLs, and are effective for general polygonal computational domains. In addition to the derivation of CFABCs, a novel explicit time-stepping scheme is developed for efficient numerical implementation. Numerical examples presented in the paper illustrate that effective absorption is attained with a negligible increase in the computational cost for the interior domain. Although this paper focuses on wave propagation, its theoretical development can be easily extended to the more general class of problems where the governing differential equation is second order in space with constant coefficients. Copyright © 2005 John Wiley & Sons, Ltd.