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SELECTION OF PROPER SYSTEM AND CONFIGURATION FOR THE SUPERSTRUCTURE |
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One of the most critical decisions influencing the ability of a superstructure to withstand earthquake ground shaking is the choice of its basic plan shape and configuration. The importance of a proper selection of the superstructure configuration will be discussed and illustrated for the case of building structures. Building structures may be of many types and configurations and there is, of course, no universal ideal configuration for any particular type of building. However, there are certain basic or guiding principles of seismic-resistant design that can be used as guidelines in selecting an adequate building configuration structural layout, structural system, structural material and the non-structural components. These basic guidelines are as follows: |
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Building (superstructure and non-structural components) should be light and avoid unnecessary masses. |
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Building and its superstructure should be simple, symmetric, and regular in plan and elevation to prevent significant torsional forces, avoiding large height-width ratio and large plan area. |
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Building and its superstructure should have a uniform and continuous distribution of mass, stiffness, strength and ductility, avoiding formation of soft stories. |
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Superstructure should have relatively shorter spans than non-seismic-resistant structure and avoid use of long cantilevers. |
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The non-structural components should either be well separated so that they will not interact with the rest of the structure, or they should be integrated with the structure. On the latter case, it is desirable that the structure should have sufficient lateral stiffness to avoid significant damage under minor and moderate earthquake shaking, and toughness with stable hysteric behavior (that is, stability of strength, stiffness and deformability) under the repeated reversal of deformations which could be induced by severe earthquake ground motion. The stiffer the structure, the less sensitive it will be to the effects of the interacting non-structural components, and the tougher it is, the less sensitive it will be to effect of sudden failure of the interacting non-structural elements. |
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Superstructure should be detailed so that the inelastic deformations can be constrained (controlled) to develop in desired regions and according to a desirable hierarchy. |
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Superstructure should have the largest possible number of defense lines, that is, it should be composed of different tough structural subsystems which interact or are interconnected by very tough structural elements (structural fuses) whose inelastic behavior would permit the whole structure to find its way out from a critical stage of dynamic response. |
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Superstructure should be provided with balanced stiffness and strength between its members, connections and supports. |
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The stiffness and strength of the entire building should be compatible with the stiffness and strength of the soil foundation. |
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Detailed discussion of the above guidelines are offered in Reference 12, 13, 18, 21 and 22. A brief discussion and illustration by Slides J59-J110 of some of the above guidelines follows. |
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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 |
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Site Design: Vivian Isaradharm, Oct. 97.
Mail to: eerclibrary@berkeley.edu |
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