Showing papers on "Earthquake resistant structures published in 1983"

Effect of Tuned-Mass Dampers on Seismic Response

Abstract: A realistic prototype high-rise building was designed and modeled using linear elastic (and also nonlinear) degrading stiffness idealizations. Using an effective damper mass ratio of 0.026, three different techniques were used to design an optimum tuned-mass damper (TMD) for the prototype. All were found to give essentially the same design. The response of the idealized prototype building to a strong ground motion was computed with and without a TMD. The TMD did not reduce the prototype's maximum response. Based on these results, vibration absorbers do not seem effective in reducing the maximum seismic response of tall buildings.

Handbook of structural concrete

Abstract: Contents: Part I: Introduction; Looking into the Future; Lessons from the Past Achievements and Failures; Design Philosophy and Structural Decisions; Part II: Materials; Selection of Materials to Improve Performance of Concrete in Service; High Strength Concrete; Fiber Reinforced Concrete; Structural Lightweight Concrete; Polymers in Concrete; Admixtures for Concrete; Failure Criteria for Concrete; Elasticity; Shrinkage, Creep and Thermal Movement of Concrete; Part III: Design and Analysis; Structural Elements Strength Serviceability and Ductility; Structural Performance as Influenced by Detailing; Fire Resistance Design and Detailing; Earthquake Resistant Structures; Design for Fatigue; Composite Construction in Steel and Concrete; Precast Concrete: Its Production, Transport and Erection; Prestressed Concrete and Partially Prestressed Concrete; Plastic Design Methods of Analysis and Design; Computer Applications 1: Use of Large Computers; Computer Applications 2: Use of Small Computers; Models for Structural Concrete Design and Environmental Design.

Design considerations for shear links in eccentrically braced frames

Abstract: Eccentrically braced framing has been gaining acceptance in seismic applications because this system can provide both high elastic stiffness and large energy dissipation capacity. The performance cf an eccentrically braced frame depends to a great extent on the behavior of short beam segments called active links. Through bending and shear. active links transfer the axial forces in the diagonal braces to other braces or to columns. These short beam members provide the primary energy dissipation mechanism for properly designed eccentrically braced frames. The results of previous experimental and analytical research has provided a good deal of information on the cyclic behavior of active links. This work has demonstrated that short active links which yield in shear (shear links) can dissipate more energy than longer active links which yield primarily in bending (bending links). However. some aspects critical to the economical design of an eccentrically braced frame which employs shear links have yet to be addressed. includina the sensitivity of link behavior to the imposed loading history. ttte linkcolumn connection detail. and the web stiffener desip and details. These three important considerations of shear link behavior are discussed in this report. The results of twelve full size shear link specimens are presented. Fach of the specimens was designed 10 investigate specific shear link response characteristics. Four specimens were tested with stiffener details which differed sisnificantly from those of previous experiments and early design applications. Another set of four specimens were designed and te~led wilh wid~ly varyina loadins histories. A set of four specimens which employed conventional moment resis~­ iog connection details were also tested. The qualitative and quantitative results of these experiments were compared and analyzed usina enel'lY dissipation capacity as a mlijor parameter. Test conclusions and desian recommendations lenerated by the lest results are then presented.

Seismic Design of Embankments and Caverns

Abstract: The papers included in this publication were presented at three symposia on seismicity and seismic design for embankment dams and underground openings. Primary topics for discussion include: (1) Seismicity and the design earthquake; (2) the design of embankment dams including seismic forces as well as methods to improve the stability of existing structures; and (3) static and dynamic design considerations for underground openings in various rock conditions and underground structures subjected to explosive loads. In each case state-of-the-art technology was sought to provide practicing engineers with techniques that can be used for design of these types of structures.

Building Critical-Mode Control: Nonstationary Earthquake

Abstract: A method of optimal open-loop critical-mode control has been applied to building structures excited by earthquake that is modeled as a nonstationary random process. The time dependent statistics of building response quantities and required active control forces have been presented. Monte Carlo simulations for building response quantities with or without active control systems have been performed to demonstrate the behavior of buildings subject to earthquake excitations. It is shown that a significant reduction for the building response can be achieved by use of active control systems. Furthermore, the required active control forces computed based on stationary earthquake model are too conservative. A sensitivity study has been carried out to determine the effect of uncertainties involved in estimating structural properties on the results of optimal control. The active tendon control system is not sensitive to the estimation uncertainties for the damping and stiffness of the building. Although the active mass damper system is not sensitive to errors in damping estimation, it is moderately sensitive to the stiffness uncertainty of the building.

Seismic tests on a model shear wall with friction joints

Abstract: The behaviour of energy-absorbing friction joints in vertical connections was studied using a model on a shaking table. By varying the slip force in the joints it was shown that there is an optimum value that maximizes the energy dissipation and minimizes the stress for a given seismic intensity.Results given by nonlinear time history dynamic analysis are compared with values from the tests. A proposed approximate method for the calculation of the optimum slip force is given that agrees well with the other values obtained. Keywords: seismic response, tall buildings, friction joints, energy dissipation, earthquake resistant structures, model tests, dynamic analysis.

Damage Analyses of Imperial County Services Building

Abstract: The failure of the Imperial County Services Building in El Centro, California, during the Imperial Valley Earthquake on October 15, 1979 is examined. The event was exceptional insofar as a modern reinforced concrete building, designed to comply with a recent code, extensively instrumentated and previously subjected to dynamic testing, was severely damaged. Available records of measured dynamic characteristics and traces of the motions induced by the earthquake in both the adjacent ground and the structure, enable critical analyses to be made of the failure modes. Building configuration and composition are summarized, together with the strong motion records obtained during the earthquake. A three-dimensional mathematical model of the building is developed and the results of computer analyses are presented. Elastic analyses are used as a basis of justifying the model and both elastic and non-linear three-dimensional time history analyses are described. Good correlation between analytical results and field observations is established. In particular the combined effect of biaxial moment and axial load in causing ground floor column failure is demonstrated.

Experimental investigations of solid state steel energy absorbers for earthquake resistant structures

Abstract: This thesis suggests the use of curved plates and bars of hot rolled mild steel as energy dissipating devices for the design of earthquake-resistant structures. The proposed devices would be used in parallel with isolating systems in buildings or other structures. They are designed to deflect ela s t i c a l l y under minor loads such as wind and to deform plastically when subjected to major earthquake loadings. The devices have a large energy absorbing capacity at a high number of cycles; they are economical and, once installed, can be easily inspected and replaced. An engineering method i s presented for predicting the number of cycles to failure of the devices. The practical application and f e a s i b i l i t y of a base-isolated steel structure with discrete yield rings is demonstrated in a model test on a shaking table. A design method for the yield rings i s proposed.

Seismic Safety: 10‐Story UBC Designed Steel Building

Abstract: In evaluating the seismic safety of a 10‐story Uniform Building Code‐designed steel moment‐resisting building, three major sources of uncertainty have been extensively examined: (1) The representation of earthquake environment; (2) the structural dynamic properties; and (3) the method of structural analysis. By combining these uncertainties, the reliability of local inelastic response conditional on the peak ground acceleration is assessed for the frame. The overall seismic safety is investigated by introducing the site‐specific seismic risk. Based on the annual local ductility exceedance probability for each story, approximate bounds are established on the “system reliability” of the example building. Using empirical relationship between structural and nonstructural damage and local ductility ratio, the annual risk of damages due to future earthquakes is investigated for the steel frame.