Earthquake Spectra

A procedure for earthquake-resistant design is developed to limit the potential damage of buildings to a tolerable level. The procedure is based on the damage model developed earlier (Park and Ang, 1984) in which structural damage is expressed as a function of the maximum deformation and dissipated hysteretic energy. The tolerable degree of damage is defined on the basis of calibration with observed damages from past major earthquakes. The design method is examined in the context of reliability.

This paper presents a methodology for the assessment of cumulative damage in structural steel components subjected to cyclic inelastic loading histories of the type experienced in earthquakes. The methodology is based on low-cycle fatigue concepts and the hypothesis of linear damage accumulation. It will be shown that seismic performance of a component depends on two structural performance parameters and on the number and amplitudes of all inelastic excursions and not only on the maximum excursion. Experimental and analytical procedures for obtaining the parameters needed for a performance assessment are suggested in the paper.

Eccentrically Braced Frames (EBFs) have attained recognized status as a viable structural steel system for resisting lateral seismic forces. Sustained research at the University of California, Berkeley, since 1977 and numerous field applications provide a good database for their proper design. In this paper the different types of EBF are critically evaluated, and the kinematics of their inelastic deformation are examined with particular reference to the behavior of isolated short beam segments or links. Desirable link length and web stiffening are recommended. A preliminary design procedure for hand-calculation of EBFs is described and some suggestions for brace connection details are advanced.

This paper presents the results obtained from tests of a new friction damping system, which has been proposed in order to improve the response of steel Moment Resisting Frames (MRF) and Braced Moment Resisting Frames (BMRF) during severe earthquakes. The system consists of a mechanism containing brake lining pads introduced at the intersection of frame cross-braces. Seismic tests of a three storey Friction Damped Braced Frame (FDBF) model were performed on an earthquake simulator table. The experimental results are compared with the findings of an inelastic time-history dynamic analysis. The results clearly indicate the superior performance of the FDBF compared to conventional building systems.

The U.S.-U.S.S.R. Agreement on Housing and Other Construction was signed in Moscow, June 28, 1974, and includes a working group on “Construction in Seismic Areas”. As part of this protocol, exchange visits have occurred of working groups from the U.S. and the U.S.S.R. This report describes the most recent exchange which took place when the U.S. delegation visited the Soviet Union during October 12-22, 1986. The delegation visited construction sites and research institutes in Moscow, Tbilisi (Georgia), and Yerevan (Armenia). The technical focus of the visit was on building structure analysis and design, ground motion and geotechnical engineering issues, and experimental studies in design, repair, and retrofit.

The Charleston, South Carolina, area offers a unique opportunity to study the implementation of policy for long-term earthquake preparedness at the local level. Our interviews of public officials and others documented the low state of preparedness in 1981 and an improved situation in 1986. Since 1981, increased national attention has been used by citizens of the Charleston area to overcome political, informational, social, organizational, and economic barriers that retard the implementation of policies to mitigate the damage caused by earthquakes.

This paper identifies some of the early decisions made after the devastating 1963 earthquake in Skopje, Yugoslavia and illustrates how those decisions shaped the city's reconstruction. The formation of a guiding committee, and a massive influx of outside aid contributed to a careful, thoughtful process for reconstruction. Also, postponement of city center redevelopment for two years and the early incorporation of seismic concerns meant that reconstruction would not just be rebuilding in the old pattern. The current development and construction process continues to take seismic concerns into account, particularly through an early required review of building location and size. Two significant problems have emerged from the long-term reconstruction—the explosive growth and boomtown atmosphere accompanying the post-earthquake rebuilding, and the dwindling resources available for rebuilding projects as more years pass from the earthquake.

The last phase of the recent U.S.-Japan Cooperative Research Program's full scale steel structure tests concerns the seismic performance of so called “nonstructural” or “extrinsic” elements. Both Japanese and U.S. elements were installed onto the full scale, moment resistant frame; static tests of the frame with cladding and internal elements took place during three weeks of July, 1984 at the Building Research Institute in Tsukuba, Japan. The U.S. side test focused on cladding, and the Japanese side oversaw testing of cladding common to Japanese practice, and internal partitions and ceilings common to both U.S. and Japanese practice. This paper describes findings of U.S. cladding performance tests with regard to values of seismic story drift designated in the Uniform Building Code, and observations of the behavior of Japanese elements.