Stephen A. Mahin

Bio: Stephen A. Mahin is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: Earthquake engineering & Braced frame. The author has an hindex of 34, co-authored 150 publications receiving 5162 citations. Previous affiliations of Stephen A. Mahin include Johns Hopkins University & Exponent.

Seismic demands on steel braced frame buildings with buckling-restrained braces

Abstract: Some results are highlighted in this paper from a research effort being undertaken to identify ground motion and structural characteristics that control the earthquake response of concentrically braced steel frames and to identify improved design procedures and code provisions. The focus of this paper is on the seismic response of three and six story concentrically braced frames utilizing buckling-restrained braces. A brief discussion is provided regarding the mechanical properties of such braces and the benefits of their use. Results of detailed nonlinear dynamic analyses are then examined for specific cases as well as statistically for several suites of ground motions in order to characterize the effect on key response parameters of various structural configurations and proportions.

NGA-West2 Research Project:

Abstract: The NGA-West2 project is a large multidisciplinary, multi-year research program on the Next Generation Attenuation (NGA) models for shallow crustal earthquakes in active tectonic regions. The resea...

A Simple Pendulum Technique for Achieving Seismic Isolation

Abstract: An innovative seismic isolation system, the Friction Pendulum System (FPS), offers improvements in strength, versatility and ease of installation as compared to previous systems. Moreover, the approach offers several inherent performance benefits not available before. The FPS uses geometry and gravity to achieve the desired seismic isolation results. It is based on well known engineering principles of pendulum motion, and is constructed of materials with demonstrated longevity and resistance to environmental deterioration. The desirable isolation characteristics exhibited by FPS components hold the promise of an effective and practical system for significantly increasing the seismic resistance of new and existing buildings. This paper summarizes results of a comprehensive research and testing program to assess the technical performance of the FPS. In addition, an example building design using the FPS is given.

Seismic Evaluation of Existing Reinforced Concrete Building Columns

Abstract: Past earthquakes have emphasized the vulnerability of reinforced concrete columns having details typical of those built before the mid‐1970's. These columns are susceptible to axial‐flexural, shear, and bond failures, which subsequently may lead to severe damage or collapse of the building. Research was undertaken to investigate the lateral and vertical load‐resisting behavior of reinforced concrete columns typical of pre‐1970's construction. Eight full‐scale specimens were constructed and were loaded with constant axial load and increasing cyclic lateral displacement increments until failure. Test data are presented and compared with behavior estimated by using various evaluation methods.

Hysteretic models that incorporate strength and stiffness deterioration

Abstract: This paper presents the description, calibration and application of relatively simple hysteretic models that include strength and stiffness deterioration properties, features that are critical for demand predictions as a structural system approaches collapse. Three of the basic hysteretic models used in seismic demand evaluation are modified to include deterioration properties: bilinear, peak-oriented, and pinching. The modified models include most of the sources of deterioration: i.e. various modes of cyclic deterioration and softening of the post-yielding stiffness, and also account for a residual strength after deterioration. The models incorporate an energy-based deterioration parameter that controls four cyclic deterioration modes: basic strength, post-capping strength, unloading stiffness, and accelerated reloading stiffness deterioration. Calibration of the hysteretic models on steel, plywood, and reinforced-concrete components demonstrates that the proposed models are capable of simulating the main characteristics that influence deterioration. An application of a peak-oriented deterioration model in the seismic evaluation of single-degree-of-freedom (SDOF) systems is illustrated. The advantages of using deteriorating hysteretic models for obtaining the response of highly inelastic systems are discussed. Copyright © 2005 John Wiley & Sons, Ltd.

NGA-West2 Equations for Predicting PGA, PGV, and 5% Damped PSA for Shallow Crustal Earthquakes:

Abstract: We provide ground motion prediction equations for computing medians and standard deviations of average horizontal component intensity measures (IMs) for shallow crustal earthquakes in active tecton...

Minimum Design Loads for Buildings and Other Structures

Abstract: Minimum Design Loads for Buildings and Other Structures provides requirements for general structural design and includes means for determining dead, live, soil, flood, wind, snow, rain, atmospheric ice, and earthquake loads, as well as their combinations, which are suitable for inclusion in building codes and other documents. This Standard, a revision of ASCE/SEI 7-05, offers a complete update and reorganization of the wind load provisions, expanding them from one chapter into six. The Standard contains new ultimate event wind maps with corresponding reductions in load factors, so that the loads are not affected, and updates the seismic loads with new risk-targeted seismic maps. The snow, live, and atmospheric icing provisions are updated as well. In addition, the Standard includes a detailed Commentary with explanatory and supplementary information designed to assist building code committees and regulatory authorities. Standard ASCE/SEI 7 is an integral part of building codes in the United States. Many of the load provisions are substantially adopted by reference in the International Building Code and the NFPA 5000 Building Construction and Safety Code. Structural engineers, architects, and those engaged in preparing and administering local building codes will find this Standard an essential reference in their practice. Note: New orders are fulfilled from the second printing, which incorporates the errata to the first printing.

Recent advances in nonlinear passive vibration isolators

Abstract: The theory of nonlinear vibration isolation has witnessed significant developments due to pressing demands for the protection of structural installations, nuclear reactors, mechanical components, and sensitive instruments from earthquake ground motion, shocks, and impact loads. In view of these demands, engineers and physicists have developed different types of nonlinear vibration isolators. This article presents a comprehensive assessment of recent developments of nonlinear isolators in the absence of active control means. It does not deal with other means of linear or nonlinear vibration absorbers. It begins with the basic concept and features of nonlinear isolators and inherent nonlinear phenomena. Specific types of nonlinear isolators are then discussed, including ultra-low-frequency isolators. For vertical vibration isolation, the treatment of the Euler spring isolator is based on the post-buckling dynamic characteristics of the column elastica and axial stiffness. Exact and approximate analyses of axial stiffness of the post-buckled Euler beam are outlined. Different techniques of reducing the resonant frequency of the isolator are described. Another group is based on the Gospodnetic–Frisch-Fay beam, which is free to slide on two supports. The restoring force of this beam resembles to a great extent the restoring roll moment of biased ships. The base isolation of buildings, bridges, and liquid storage tanks subjected to earthquake ground motion is then described. Base isolation utilizes friction elements, laminated-rubber bearings, and the friction pendulum. Nonlinear viscoelastic and composite material springs, and smart material elements are described in terms of material mechanical characteristics and the dependence of their transmissibility on temperature and excitation amplitude. The article is closed by conclusions, which highlight resolved and unresolved problems and recommendations for future research directions.