International Concrete Abstracts Portal

A finite element analysis of strength determined from 150 physical tests of rectangular composite steel-concrete columns taken from the published literature was undertaken. The columns used for this study were braced and pin-ended and were constructed using normal strength concrete with a specified compressive strength between approximately 2500 and 8100 psi (17.2 and 55.8 MPa). The columns were subjected to short-term loads producing pure axial force, combined axial force and symmetrical single curvature bending, or pure bending. Major variables included the concrete strength, the end eccentricity ratio, the slenderness ratio, the structural steel index, and the tie/hoop volumetric ratio. The study provides a critical review of the reliability of the finite element modeling method examined.

The amount of tension reinforcing steel bars plays a major role in determining the flexural ductility of reinforced concrete beams. The addition of Carbon Fiber Reinforced Polymer (CFRP) composites, which is another form of tension reinforcement, affects the ductility of concrete beams strengthened with CFRP sheets. Several researches have'investigated the use of CFRP for increasing the flexural strength of concrete beams. However, the flexural ductility of beams with respect to the amount and yield strength of existing ordinary steel bars has not been investigated in depth. In addition, delamination of CFRP sheets dominates the ultimate mode of failure of flexural members strengthened with CFRP sheets, which limits the ductility of strengthened members. There is a need to investigate the effect of CFRP anchorage system on the overall ductility of strengthened girders. This paper presents the results of an experimental investigation of nine large-scale reinforced concrete beams strengthened with CFRP composite sheets. The main variables are the amount of the existing reinforcing steel bars, yield strength of steel bars, and the type of CFRP anchorage. The amount (size and type) of the longitudinal CFRP sheets was maintained constant. Test results showed that the lower the amount of existing ordinary steel bars the lower the flexural ductility of the CFRP strengthened beams. Test results have also shown that CFRP anchorage could significantly increase the flexural ductility of CFRP strengthened beams. Such important findings should be reflected on the design equations of CFRP sheets required for strengthening existing reinforced concrete beams to ensure an acceptable level of flexural ductility.

The education and professional contributions of Richard W. Furlong are given in this paper as a part of the Richard W. Furlong Symposium on April 22,2002 at the ACI Convention in Detroit, Michigan. Highlights of Dr. Furlong’s career of teaching and research at The University of Texas at Austin are noted. The emphasis is on how, as an experienced designer, he was effective in transferring research results to practical design guidelines and building code provisions. The paper is meant to give personal recognition and express our appreciation for all the many contributions he has made to the American Concrete Institute for more than 40 years.

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.

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.