Recent Developments in Seismic Design and Construction

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	*National Information Service for Earthquake Engineering* *University of California, Berkeley*

RECENT DEVELOPMENTS IN SEISMIC
DESIGN AND CONSTRUCTION


	Some of the results obtained in the integrated analytical and experimental research conducted in the area of seismic-resistant building design and construction in various research institutions of the work have already been applied in improving building design and construction in regions of high seismic risk. Examples of these applications are illustrated in Slides J114-J119.


	J114. Pacific Park Plaza Building, Emeryville, California. View of the reinforcement used in the columns of the reinforced concrete ductile moment-resistant space frame used in this modern 30-story building completed in 1984. A number of modern approaches and techniques were used in the design and construction of this tall building, with three slender wings, to attain the required seismic safety and providing architectural planning freedom with compatible economy.


	Note in Slide J114 the close spacing of the lateral reinforcement that has been provided in the columns to obtain adequate confinement. Note also the spacing left to insert the prefabricated steel cage for the beams. Prefabrication of stirrup reinforcement assemblies using 5.2 ton per square centimeters yield welded wire fabric facilitated the fabrication of the reinforcement for these beams. The column ties were machine bent fabric wire and were rebent at the shop. The column reinforcement was mechanically spliced and a high concrete strength (460 kilograms per square centimeter) was used in the lower portion of the building [35].


	J115. Composite structural steel-reinforced concrete earthquake-resistant building under construction in Japan. Selection of proper (suitable) material is one of the most important steps in seismic-resistant construction.


	Field inspection of performance of structures during earthquakes and laboratory research have shown that while structural steel is a very ductile material, when it is used in framed structures requiring significant amount of energy dissipation through inelastic deformation at the critical regions of the members, local buckling limits the ductility (energy dissipation capacity) of the whole structure. On the other hand, the problems with the use of properly confined reinforced concrete as a structural material for earthquake resistance are in the shear resistance of the members and in the anchorage of the main reinforcement at the critical regions which usually occur at or near the joints. To avoid the particular weaknesses of these two materials, the Japanese have been developing the use of composite structural steel-confined reinforced concrete construction. As illustrated in Slide J115, a light structural steel frame with castellated beams is built first using solid continuous shapes at the joints which will provide the required continuity (anchorage) of the members connected at the joints. To avoid the buckling of these slender steel members, they are then covered with confined reinforced concrete as can be seen at the back of the right side of the slide. By the use of this type of composite material, the weaknesses of the individual materials have been overcome. This is the structural material that is commonly used in Japan for mid- and high-rise buildings.


	J116. Use of structural steel column-tree assemblies prefabricated (welded) in the shop to avoid welding at the critical regions of frame structures. This slide illustrates the use of such a construction technique which has become very common in Japan and which offers the advantages of better control of the welded connections. Laboratory tests have shown that these connections constitute a problem when welding is done in the field.


	J117. Overall view of the erection of a structural steel- framed structure using prefabricated tree-column assemblies.


	J118. Tall structural steel building, San Diego, California. The lateral resistant structural system of this building is based on the use of eccentric braces. Research conducted over the past ten years has clearly shown the advantages of using eccentric braces rather than the standard concentric braces which have normally been used in the past [36].


	J119. Close-up of the structure of Slide J118 showing the eccentrically braced bays of this tall structural steel building under construction.


	J120. Building using concrete cores with steel framing constructed at grade, raised into position and then attached to the cores and/or hung from the top of the cores. This technique, which was developed two decades ago, offered significant economic advantages and started to be used in regions of high seismic risk such as California where several of these buildings were built in the decade 1960-1970. However, problems related to achieving good connections and doubts regarding the seismic response of these buildings under severe earthquake ground motions have resulted in abandoning this form of construction in California.


	The University of California, Berkeley Copyright 1997, The Regents of the University of California. Structural Engineering Slide Library, W. G. Godden, Editor Set J: Earthquake Engineering, V. V. Bertero


	Site Design: Vivian Isaradharm, Oct. 97. Mail to: eerclibrary@berkeley.edu