Reliant Stadium in Houston, Texas will he the first retractable roof football stadium in the United States. Like the Astrodome before it, this new stadium will represent the state-of-the art in stadium design, hosting not only a new NFL football team, but also the renowned Houston Livestock Show and Rodeo. The structure for Reliant Stadium incorporates several unique structural concepts to make it economical and yet still support the architectural design. The giant supertrusses that span the sidelines at each side of the stadium support the retractable roof structure. The gentle arch-shaped bottom chord was dictated by architectural sightlines and required a rigid frame action with its supporting supercolumns. In addition, the supertruss was designed to be a composite steel/concrete element for economy. The concrete top chord serves as support for the rails of the retractable roof. The composite supertrusses are believed to be the largest ever constructed in a building structure. Structural analyses that provided envelope solutions to account for the variation in soil and concrete stiffnesses were undertaken to properly design the supertrusses, supercolumns and the mat foundations that support them. A wind tunnel study was undertaken to accurately predict the design wind forces from Gulf Coast hurricanes. Special precautions were taken to control mass concrete temperature effects in the placement of the mat foundations for the supercolumns. The complete structural system and the details of its design are described in the paper.

With traffic volumes continuing to increase on a rapidly deteriorating infrastructure, new methods are needed for expediting construction of durable, high performance concrete pavements with minimal disruption to traffic. One method, which has received significant attention in recent years, involves the use of precast concrete panels. Precast concrete panels can be cast and cured in a controlled environment, stockpiled, and set in place in a short amount of time, allowing for construction to take place during overnight or weekend operations. In March 2000, the Center for Transportation Research at The University of Texas at Austin completed a feasibility study which investigated the use ofprecast prestressed concrete panels for pavement construction. Following the feasibility study, a pilot project was initiated by the Texas Department of Transportation to test and refine these concepts on an actual project. Recently, consbuction of this pilot project was completed on a section of frontage road along northbound Interstate 35 near Georgetown, Texas. Although it was constructed without the time constraints and complexities that will eventually need to be considered for precast pavement construction, the viability of the concept for precast prestressed concrete pavement was clearly demonstrated and will ultimately lead to development of future precast prestressed concrete pavements.

Design requirements for composite construction in steel and concrete as practiced in the United States are reviewed. Included are buildings and highway bridges. After a brief account of the origins of composite construction in America, an emphasis is placed on the early rules issued by ACI and AISC for composite columns in buildings, by AASHO - the predecessor of AASHTO-for composite beams in highway bridges and by AISC for composite beams in buildings. All four sections include outlines of subsequent changes that have taken place over the years. The paper is concluded with a discussion of a potential decrease in the strength of a stud shear connector located in the trough of a steel deck.

Synopsis: Components of most concrete structural systems, such as slabs, long span thin shells, containment vessels and protective structures are stressed in multiaxial states of stress. This study explores the behavior of high strength high performance concrete under hiaxial loading in comparison to uniaxial loading conditions, and to propose a modified Elastic Modulus expression for concretes under biaxial loading for cylinder compressive strengths above 12,000 psi (82 MPa). In excess of 100 high-strength cube specimens in several series were tested to failure under uniaxial and biaxial compression. Ratios of the minor to major principal stresses (o2/o1) were selected as a major test variable. From the test results, it is shown that confinement stress in the minor principal direction has a pronounced effect on the strength and deformational behavior in the principal direction. Both the stiffness and ultimate strength of the concretc increased to a value of approximately 30 percent. Crack development in the tested specimens under biaxial compression progressed into asymptotic tensile splitting cracks along the o2 direction. A mathematical model and an empirical equation were developed for the elastic modulus ofconcrete under biaxial loading as a result of these tests.

Composite reinforced concrete column-steel beam (RCS) frame systems initiated in high-rise construction in the United States as perimeter moment framing (tnbular construction) due to the speed of erection, material cost savings, and enhanced lateral load resistance and performance. An overview of traditional RCS frame construction, advantages, previous research, and beam-column joint issues are presented. Then, the idea of using this form of construction for three-dimensional space frames is discussed and previous research on the performance of these systems for zones of high seismic risk is summarized. In a collaborative effort with structural engineers, an expenmental and analytical investigation of composite RCS fiame systems is proposed for low- to mid-rise construction in areas prone to high-level wind storms and/or moderate seismic risk. New beam-column joint connection details that are economically feasible and constructable are presented. The preliminary results from the analytical investigation on the proposed experimental specimen tests during lateral loading are also presented.