International Concrete Abstracts Portal

This paper provides discussion and suggestions on the very difficult question of how to best teach the design and construction of concrete structures at the undergraduate level and beyond. The end goal remains unchanged-to provide the best possible constructed facilities for the public and private sectors. After presenting the background and scope of coverage, important issues in structural design are discussed, including a defmition of the three types of knowledge bases needed in performing any design. Expectations of new graduates as they enter the work force are covered, and implications for professional registration are discussed. The paper continues with extended discussion on a host of important issues that need coverage to varying degrees in the curriculum. The critical importance of proper integration of materials selection into the overall design process is explored. Given that learning must be a life-long process, professional post-B.S. education approaches (both "conventional" and internet-based) are presented, along with comments on the ASCE position that the professional Master’s degrees should become the degree of entry into the profession. The paper concludes with suggestions and recommendations.

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.

In most design codes (1,2,3) provisions for the design of confinement reinforcement contain empirical constants that were based on the experimental data available in the literature. Most of the data used was from tests in which normal strength concrete columns with square cross sections were used. Only recently, a limited amount of experimental data on high strength concrete (HSC) columns bas become available. Experimental data on rectangular HSC column behavior, on the other hand, is rarely found in literature, especially on large size HSC specimens tested under moderate to high axial load levels and subjected to large inelastic displacement excursions. This paper presents results from a continuing research program which aims to study confinement of concrete by lateral reinforcement. The current work deals with the experimental behavior of HSC (52 MPa < fc’< 112 MPa) columns having rectangular cross sections. Large-size columns (250 x 350 x 1473 mm) with heavy stubs (508 x 762 x 813 mm) were tested under moderate to high axial load levels and reversed cyclic displacement excursions. Effects of several variables such as section geometry, axial load level, and amount of lateral reinforcement on the behavior of these specimens are studied, and the responses of the rectangular specimens are compared to those of specimens with square cross sections. It is concluded that HSC columns having square and rectangular cross sections can be designed to behave in a ductile manner, provided that sufficient amount of confinement reinforcement is used in an efficient configuration.

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.

This paper presents the research work, experimental and analytical, on precast hybrid concrete beam-to-column connections at the National Institute of Standards and Technology and its contribution to the development of seismic design provisions for precast concrete frame structures.