Developments in seismic structural analysis and design The theory of performance-base seismic design (PBSD) was suggested firstly by the American scientists and engineers in the beginning of 1990s. The Japanese and European scholars in earthquake engineering field took great interest in it and devoted to it at all of the standpoints. In recent years, many researchers in China discussed the theory. Mr. Ya-yong wang suggested that the Chinese seismic design code would follow the trend of world and that the study of the theory would be integrated with the national condition of China. The background of the occurrence, the development, the basic idea, the main properties of the theory and the present research are summarized in this paper. Its importance to improve the seismic design theory is pointed out, too, finally.
EngineeringStructures,Vol t7, No 3, pp 187-197, 1995 Copyright © 1995 Elsevier Science Ltd Printed in Great Britain All rights reserved 0141~0296/95 $10.00 + 0.00 r~UTTERWORTH I"I~E , N E M A N N 0141-0296(94)00006-9 Developments in seismic structural analysis and design Egor P Popov, Carl E Grigorian and Tzong-Shuoh Yang Department of Civil Engineering, University of California, Berkeley, CA 94720, USA (Received December 1993; revised version accepted March 1994) After a brief overview of the world-wide state-of-practice in seismic design, nonlinear structural response spectra for strength, ductility and number of yield reversals as a function of building period and structure strength for several strong motion earthquakes are presented Illustrations of three-dimensional mesh surfaces for the absolute seismic energy input and the dissipated hysteresis energy for selected earthquakes are given These results are compared with conventionally evaluated elastic response spectra and code criteria The issues of overstrength factors in the Mexico City code are then examined The remainder of the paper is devoted to the description of a simple frictional energy dissipating connection Its behaviour in cyclic tests and in shake table tests of a three-storey braced steel structure is illustrated Keywords: energy dissipation, friction, Mexico City seismic code, seismic design, over-strength factors State-of-practice in design The world-wide state of seismic design practice based on current codes and some developments in nonlinear seismic spectra are highlighted first These include displacement ductility and a number of yield reversals spectra for the 1986 San Salvador, the 1985 Chile and the 1985 Mexico City earthquakes Three-dimensional mesh surfaces of absolute input energy and hysteretic energy for the 1985 Mexico City earthquake are displayed These surfaces show graphically the seismic energy demands on the structural systems subjected to the Mexico City earthquake The Mexico City code force spectra, supplemented with spectra considering structural overstrengths above the code minima, are then examined for the effect of overstrength Spectra for the number of load reversals at different levels of overstrength are also shown The second part of the paper concerns itself with a recently developed frictional energy dissipator This inexpensive and nonproprietary device dissipates energy through friction during rectilinear tension and compression cycles It can be conveniently used as a connection between a brace and a gusset plate In addition to the gusset plate having long slotted holes, the splice plates and two thin brass shims make-up the assembly fastened together with high-strength bolts tensioned to the required tension force An extensive experimental programme was conducted on the reliability of this connection The final verification of these connections was obtained by doing a shake table test on a three-storey model having 12 such connections and the same number of chevron braces There are two pending projects in California where it is intended that frictional energy dissipating connections will be used The state-of-practice in design is based on response spectra determined by studying the behaviour of elastic systems For a fixed natural period of a system and damping coefficient, a step-by-step integration is performed for the duration of an eathquake determined from an accelerogram The largest value of the selected response, commonly acceleration, is the spectral value of the response of the system corresponding to the fixed period By repeating the process for numerous periods, a spectral curve is obtained This procedure was repeated for six different earthquakes to generate the curves shown in Figure ACCELERATION (g's) 2.5 I m ME~OCO 11rTe M I Y A G ~ ,~ " C H 2.0 - /:t l" 1.5 ei 'r~"" LP" , t ~, ~ ~ CHILE I m COMAP~'TA I040 ELCENTRO r,~ 1"7-4 ~ I, o., 0.0 0.0 * I * I * o.s 1.0 1.s 2.0 2.s 3.0 PERIOD ( s e e ) Figure C o m p a r i s o n o f l i n e a r elastic r e s p o n s e spectra w i t h 5% d a m p i n g f o r selected e a r t h q u a k e s ( c o m p i l e d b y E M i r a n d a ) 187 Seismic structural analysis and design: E P Popov e t al 188 After numerous studies of spectra, idealized elastic ultimate state spectra were adopted by different authorities Two such idealized curves proposed by the Applied Technology CounciP are shown in Figure One of these curves is for Soil 1, corresponding to stiff soil conditions; the other, for Soil is for soft clays and sand Similar curves in the form of an equation are promulgated by the UBC (Uniform Building Code) z, giving the total design base shear, Vs, for the allowable stress design ZIG V8 = n - Wwhere C 1% 1.25S T2,3