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International Concrete Abstracts Portal

Showing 1-5 of 23 Abstracts search results

Document: 

SP157-15

Date: 

October 1, 1995

Author(s):

W. G. Corley

Publication:

Symposium Papers

Volume:

157

Abstract:

Two hypothetical reinforced concrete buildings (one with special moment resisting frames and the other with structural walls) were designed. Using a time-history inelastic behavior approach, both buildings were analyzed. Drifts were determined for these structures when subjected to severe earthquakes similar to those expected in North America. In addition, drifts associated with an analysis based on ground motions measured for the 1985 Mexico City earthquake were also determined. Measured drifts from components detailed under 1990's North American code requirements are compared with calculated building drifts. These comparisons indicate that the 1990 code requirements provide significantly more capacity than calculated to be needed for the structures and components considered. Finally, minimum drift requirements for components to be used in ductile frame buildings and in shearwall buildings are suggested.

DOI:

10.14359/984


Document: 

SP157-12

Date: 

October 1, 1995

Author(s):

V. V. Bertero and R. D. Bertero

Publication:

Symposium Papers

Volume:

157

Abstract:

A new conceptual code format has been developed for earthquake- resistant design (EQ-RD) of buildings. It consists of guidelines for conceptual overall design of entire building systems and a conceptual methodology for numerical EQ-RD of building systems in compliance with the worldwide accepted EQ-RD philosophy and based on energy concepts, fundamental principles of structural dynamics, mechanical behavior of entire building facilities, and comprehensive design. The numerical EQ-RD methodology considers the desired seismic performance of the entire building system explicitly from the beginning of the EQ-RD process and concludes by evaluating whether such performance would be achieved. A discussion of the main aspects and problems involved in the preliminary numerical EQ-RD procedure is presented in this paper. Main results from its application to at 30-story reinforced concrete space-frame building are discussed and compared to results from analysis of the performance of the same building designed according to 1991 UBC, showing the weakness of present UBC seismic regulations when applied to tall buildings, particularly regarding performance under service level EQ ground motions. The main advantage of the proposed conceptual methodology is that uncertain quantifications of its concepts can evolve without changing the format of the codified methodology as new and more reliable data are acquired.

DOI:

10.14359/1006


Document: 

SP157-07

Date: 

October 1, 1995

Author(s):

R. C. Fenwick and B. J. Davidson

Publication:

Symposium Papers

Volume:

157

Abstract:

To survive a major earthquake, current practice requires seismic resistant frames to be designed to be ductile. To achieve the required level of ductility in multistory frames, the majority of the potential plastic hinge zones are located in the beams. The inelastic rotation, which may develop in these zones, arises predominately from the tensile yielding of the reinforcement. The associated compressive strains are small and, as a consequence, elongation occurs. Test results show that elongation on the order of two to four percent of the member depth develop in plastic hinge zones of beams subjected to cyclic loading before strength degradation occurs. The factors influencing elongation are reviewed in this paper. The results of a time history analysis, in which elongation effects are modeled, shows that this action, which is neglected in current design practice, has important implications for the detailing of columns and the design of supports for precast components and external cladding.

DOI:

10.14359/982


Document: 

SP157-08

Date: 

October 1, 1995

Author(s):

A. J. Carr and M. Tabuchi

Publication:

Symposium Papers

Volume:

157

Abstract:

The New Zealand Standard for design loadings for buildings (NZS4203) was revised in 1992 superseding the earlier standard NZS4203 (1984). Some of the most significant changes in the new code are a considerable increase in the allowable interstory drifts and a marked reduction in the seismic lateral forces for structures with longer natural periods. Designers may now be encouraged to design buildings to the maximum allowable drifts as the resulting buildings will attract smaller lateral loads. Reinforced concrete buildings designed with the new loadings code may be constrained by the minimum reinforcement requirements rather than strength requirement of the loadings code; as a result, they may have a different distribution of strength capacity from that assumed in the code design. Because of this, buildings designed using the capacity design principles may not have the strength distribution that the designer intended. The reasons for this problem are discussed in this paper and the effects of the irregular distribution of strength capacity are investigated using inelastic response analysis. It was found that the large reduction of the design lateral forces resulting from the large allowable interstory drifts may lead to the problem. The design lateral forces or the deflection limits defined in the new code, NZS4203 (1992), may need to be reconsidered.

DOI:

10.14359/1004


Document: 

SP157-20

Date: 

October 1, 1995

Author(s):

M. Rodriguez and R. Meli

Publication:

Symposium Papers

Volume:

157

Abstract:

Waffle-flat plate buildings are very popular in different countries. Their seismic performance has been very poor. Several research projects on the seismic response of these buildings have been performed at the Instituto de Ingenieria, UNAM; their results and findings are summarized in this paper. First, the main features of the structural system and of its resistance to lateral loads are presented. The most common mechanisms of collapse are described and the observed performance during the 1985 Mexico earthquake is discussed. A case study of building performance during the earthquake is briefly presented. Results of an experimental research on a two-story model of a waffle-slab building are described. The specimen was first tested in a haking table and later subjected to cycles of static lateral loads. The specimen showed a rather poor behavior with very small lateral stiffness and limited energy dissipation capacity. The failure mechanism was mainly governed by the shear and flexural strengths of the columns and by flexural cracking in waffle slabs. Recommendations for the proper use of the system are given, emphasizing the need to combine it with structural walls, bracings, or stiff frames to achieve the necessary lateral stiffness and strength in a building.

DOI:

10.14359/987


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