International Concrete Abstracts Portal

SP-228CD This CD-ROM of Special Publication 228 contains the papers presented at the Seventh International Symposium on the Utilization of High-Strength/High- Performance Concrete that was held in Washington, D.C., USA, June 20-24, 2005. The symposium continued the success of previous symposia held in Stavanger, Norway, (1987); Berkeley, California (1990); Lillehammer, Norway, (1993); Paris, France, (1996); Sandefjord, Norway, (1999); and Leipzig, Germany, (2002). The symposium brought together engineers and material scientists from around the world to discuss topics ranging from the latest applications to the most recent research on high-strength and high-performance concrete. In the years since the first symposium was held in Stavanger, there has been worldwide growth in the use of both high-strength and high-performance concrete. In addition to more research and applications of traditional types of high-performance concrete, the use of self-consolidating concrete and ultra-high-performance concrete has moved from the laboratory to practical applications. This publication offers the opportunity to learn the latest about these developments.

Composite structures made of structural steel and concrete maximize the advantages of the two components, especially, when using high strength materials. The interaction of the two materials is guaranteed by shear connectors. Experimental and numerical investigations at the Institute of Structural Concrete, RWTH Aachen University indicate that headed studs in high strength concrete (HSC) show a different behavior compared to those in normal strength concrete (NSC). Headed studs in HSC feature a high load carrying capacity coming along with a high initial stiffness but a reduced ductility. In order to improve the ductility various modifications have been applied to the studs (for example headed studs embedded in ultra-high performance concrete). Three-dimensional finite element simulations have been conducted to obtain an insight into the complex load carrying behavior. Based on a parametric study the influence of the concrete strength on the load carrying behavior has been investigated. This paper presents the experimental and numerical results. The different modifications applied to the shear connectors are judged from both design and economical points of view.

Two-point loading tests were conducted to examine the shear and flexural behavior of High Strength Steel Fiber Reinforced Concrete (HSFRC) elements with a minimum amount of reinforcement. In shear, considerations of the ratio between the capacity that is required of the minimum shear reinforcement and the concrete shear capacity Vc show that the requirement for minimum reinforcement may depend on the definition of Vc, i.e., whether it is that of the plain concrete or that of a concrete mix, which includes the fibers. In flexure, the addition of fibers to flexural members with a minimum longitudinal reinforcement caused in the current study a more brittle behavior compared to the same specimens, which did not include fibers. This result suggests that the minimum longitudinal reinforcement ratio in flexural HSFRC members should be higher than in conventionally reinforced members (i.e., without fibers) in order to achieve sufficient ductility.

To improve the toughness and shear resistance of high strength concrete, steel fiber was induced into the reinforced high strength concrete beams. 39 steel fiber reinforced high strength concrete (fcu=52.4~84.7MPa) beams with stirrups and 5 control beams were tested. The test program was divided into two series. One series was tested under two symmetrical point loads, and the other was tested under an equivalent uniformly distributed load simulated by eight symmetrical point loads. The main variables were steel fiber volume fraction, steel fiber type, stirrup content and concrete strength. The test results showed that deformation properties, diagonal cracking strength and shear strength of the beams were improved significantly by the addition of steel fibers. Based on the test results, some empirical formulas are given to predict the diagonal cracking strength and shear strength of steel fiber reinforced high strength concrete beams. Results are also coordinated with those for reinforced concrete beams.

Three 96-ft (29.3-m) long, 72-in. (1.83-m) deep, pretensioned bulb-tee girders were tested to evaluate behavior under static shear loadings. The three girders had a design concrete compressive strength of 10,000 psi (69.0 MPa) and incorporated 0.6-in. (15.2mm) diameter, Grade 270, low relaxation prestressing strands. One of the girders was designed based on the AASHTO Standard Specifications for Highway Bridges and the other two were designed based on the AASHTO LRFD Bridge Design Specifications. The shear designs incorporated the use of either welded wire fabric or conventional bars for reinforcement. Prior to testing, a 10-ft (3.05m) wide reinforced concrete deck slab was added to each girder and a fatigue test was performed. After the fatigue test, each girder was cut in half and both ends were tested to evaluate static shear strength performance. Measured strengths consistently exceeded the design strengths calculated by both AASHTO design approaches using both design and measured material properties.