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SP-174 Innovative design applications and advanced research has led to widespread use of steel and concrete composite and hybrid systems in the construction of buildings, bridges, and many other types of civil structures. The state of the art in this field continues to move forward today. Extensive research programs and field testing have yielded efficient, reliable, and safe procedures, incorporating these two dissimilar materials for overall improved construction. This publication presents an overview of the latest developments in behavior and design of composite and hybrid structures. In 1995 ACI Committee 335 sponsored two technical sessions in Montreal, Quebec on the current practice of the composite and hybrid construction and the state of the art in the field. Researchers and practicing engineers from the United States, Europe and Japan gave presentations encompassing topics related to design and construction of composite and hybrid systems and the advancement of research in three continents. The twelve papers appearing in this volume include topics presented in Montreal, along with additional manuscripts. The breadth and depth of the material covered make this publication a useful resource to practicing engineers, educators and researchers.

A five-year research program on Composite and Hybrid Structures as Phase 5 of the U.S.-Japan cooperative Earthquake Research Program was recommended to be initiated in 1993 in both countries. Presented in this paper is a summary of the research program which is based on a number of technical meetings of the U.S. and Japan Planning Groups and a Joint Planning Workshop. Because of diverse and broad scope of the subject area, the research program is organized into the following four groups: New Materials, Elements and Systems; Concrete Filled Tube Column Systems; Reinforced Concrete (RC) and Steel Reinforced Concrete (SRC) Column Systems; and RC/SRC Wall Systems. A theme structure with well selected layout, geometry and design loads for the research is also presented, which provides a common focus for various systems to be studied, and also a common prototype structure from which the components and sub-assemblages are drawn.

Strengthening existing concrete members using externally bonded steel plates (BSP) is an effective method of enhancing both serviceability and ultimate strength of concrete members. In recent years, several BSP field applications, for both building and bridges, have been reported in many countries. In addition, extensive experimental and theoretical investigations of the factors nfluencing the structural performance of epoxy bonded plated concrete beams have been reported by many researchers. This paper presents a review of the previous research on the structural behavior of composite steel plated concrete beams. An overview of the effectiveness of the bonded plate on the serviceability, strength and mode of failure of strengthened reinforced concrete beams is presented.

Following the symposium on Hybrid and Composite Construction and after receiving the papers for the proceeding volume, the committee decided that in addition to the presented papers, it will add considerably to the value of the volume, if there was an opening paper to present an overview as well as the future predictions of the whole system. Mr. Viest, known in this field for a long time, was invited to do this difficult task. In his presentation, Mr. Viest reviews the past and the present, and concludes with some future directions, which hybrid and composite construction might take.

This paper describes research associated with the seismic behavior of moment connections for concrete filled tube (CFT) column-to-wide flange (WF) steel beam framing systems. The objective of this multiphase research program is to assess the force transfer mechanism in these connections, examining the effect various structural details have on this mechanism, as well as on the connection’s strength, stiffness, and ductility. The first phase of the program was devoted to assessing the shear capacity of the panel zone in a CFT column-to-beam connection under simulated seismic lateral load conditions. The results from tests show that a CFT panel zone possesses exceptional ductility, including connections without interior diaphragms. In addition, a capacity equation based on the superposition of the shear strength contribution of the steel tube and concrete core within the panel zone provides a prediction that agrees reasonably well with specimen strength. The second phase of the research program involves full-scale structural connection subassemblage tests. Results from tests show that specimens in which the beams are designed to dissipate energy can have exceptional cyclic ductility. However, connections’ must be properly detailed to avoid strain concentrations which could lead to fracture. Measured deformations in the column show that a CFT column’s initial stiffness is well estimated by transformed section theory. However, interstory drift deformations beyond 0.5% of the story height tend to reduce the stiffness after concrete cracking and debonding of the concrete from the steel tube.