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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

Considerations regarding bond and development of reinforcement in high strength concrete (HSC) are presented from a North American perspective. The information contained in this paper is a compilation of information from various sources and represents a survey of the basis for North American approaches to bond of normal and high strength concrete under monotonic and cyclic loading. The paper was presented in part at the Second US-Japan-New Zealand-Canada Multilateral Meeting on the performance of HSC held in Honolulu November 29-December 1,1994.

In this paper, research on bond and anchorage of reinforcement in high strength concrete were reviewed. They were classified to three groups: research on bond capacity with splitting of surrounding concrete, bond deterioration of bars passing through beam-column joints and anchorage capacity of hooked bars in beam-column joints. A characteristic property of low tensile strength relative to the high compressive strength results in a small increase of bond and anchorage capacity if the failure mode is governed by concrete splitting. Transverse reinforcement is more important for high strength concrete. The effect of concrete strength is more for the bond which failed in concrete crushing or direct shearing at the interface, such as the bar passing through the joint. High compressive strength and high rigidity of stress-strain curve makes the local bond-slip curve stiffer. Low sedimentation and low bleeding effects make the top bar effect small. bBfyy By analyzing available research, bond and anchorage capacities were evaluated quantitatively for practical design use.

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.