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In May of 1993, approximately twenty researchers and five representatives from construction firms met in Kyoto, Japan, for the First Multilateral Meeting on Structural Performance of High-Strength Concrete in Seismic Regions. Four countries (United States, Japan, New Zealand, and Australia) were representated at the meeting. The 3-day meeting divided into eight sessions covering current research programs and applications of high-strength concrete in the respective countries. The objectives of the meeting were to exchange information and to develop a coordinated program for further information exchange, evaluation of information, and development of design guidelines for the use of high-strength concrete in seismic regions. The follow-up meeting was held in November 1994 in Honolulu, Hawaii, and was attended by twenty seven participants from the US, Japan, Canada, New Zealand and Hong Kong. The Second Multilateral Meeting on Structural Performance of High-Strength Concrete in Seismic Regions consisted of thirteen sessions. Six of the sessions concentrated on the following behavioral topics: bond and anchorage, confinement, flexural members, axially-loaded members (columns and walls), beam-column joints, and shear and torsion. An additional session was devoted to presentation and discussion of design concepts and applications of high-strength concrete (HSC) in seismic regions. The remaining six sessions consisted of large and small working group sessions. During the small group sessions, participants were divided into groups of five to ten members to discuss the results of the previous sessions. Summaries of the small working group were then presented to the entire group fro additional comments and conclusion during the large working group sessions. This ACI Symposium Publication comprises selected papers which were the outcome of the Second Multilateral Meeting on Structural Performance of High-Strength Concrete in Seismic Regions. The working group discussion summaries are also included in this special publication. The editors are appreciative of the eforts of the authors and reviewers of these papers. The cooperation of the authors in the careful revision of their papers in accordance with the reviewers' comments is greatly appreciated. Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP176

This paper presents an overview of the provisions for anchorage and development of reinforcement in concrete for New Zealand concrete design code : NZS 3101: 1995 (1). These provisions take into account the nature of high strength concrete (compressive strength f’c > 55 MPa (8000 psi)) and the expected performance under seismic loading. The criteria for development lengths for straight reinforcement (with specific surface deformations) and those for bars terminated with hooks are largely based on recent studies of Sozen and Moehle and ACI 318: 1989. Simple, conservative equations are presented along with less conservative equations of more complexity.

This article points out the requirements of ACI 318 (1) and the Uniform Building Code (2) concerning the confinement of concrete in beams, columns and shearwalls that are part of the lateral force resisting system of a structure in a region of high seismicity. It reviews available research to assess the adequacy of these requirements when high-strength concrete is used in the structural members. ACI 318 notation is used throughout this article.

The first purpose of this report is to introduce experiments on 91 square confined concrete specimens and 59 circular ones with high strength materials subjected to monotonic and concentric axial loading conducted in Japan recently. The concrete strength of specimens ranged from-27 MPa to 132 MPa and the strength of transverse reinforcement ranged from 173 Mpa to 1360 MPa. Small size specimens with section dimension of about 200 mm have been conducted mainly but it is notable that four quasi-real size specimens with 470 mm square section were tested through the New RC Projects. The second purpose of this report is to introduce the recent research works on models, examining their feasi-bility. Conclusions included the following: (1)Regarding the maximum strength of the square confined specimens, the predictions with the models proposed by Sakino et al. and Watanabe et al. were accurate enough especially for quasi-real size specimens. However, the accuracy of the prediction for the axial strain became much worse compared with that for maximum strength in each model. (2)Regarding the stress-strain curves, the relations of the model by Sakino were quite similar to the observed curves until the end of the loading of quasi-real size specimens. (3)Regarding the effects of the material strengths, assuming that the model by Sakino was true, it was concluded that the stress increase was indc-pendent of the concrete strength and proportional to the strength of transverse reinforcement as far as it reached 6X7 MPa. On the other hand, the strain increase depended on the concrete strength: it decreased with the increasing value of the concrete strength.

Synopsis: Recent research on confinement of high-strength concrete (HSC) is reviewed. The emphasis is placed on the effects of confinement parameters and related experimental research. A review of analytical models proposed for HSC is also presented. The results indicate that for similar strength and deformability, HSC requires higher confinement pressure than normal-strength concrete. The level of lateral pressure required can be provided by increasing the volumetric ratio and grade of continement reinforcement. The effkiency of pressure can be improved by reducing the spacing of lateral reinforcement in both the longitudinal and cross-sectional planes. When properly confined, HSC exhibits ductile stress-strain characteristics. The analytical models developed for normal-strength concrete cannot be used to describe stress-strain characteristics of HSC. A number of models have been proposed for HSC that produce good correlations with experimental data.