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.

The shear capacity of stirrup-reinforced concrete elements consists generally of a portion modeled by a truss Vtruss and an exceeding concrete contribution Vc. Recent research results assign a portion of the concrete contribution to the effect of aggregate interlock. After shear cracking, a relative displacement of the crack edges occurs activating friction forces upon the rough crack edges with increasing load. In such a model the concrete contribution is considered solely by a more flat strut inclination , and accordingly a truss model can describe the whole shear-capacity. In addition, the shear behavior of high strength concrete is different than ordinary concrete, presumable due to the different shear transfer mechanisms across the shear cracks. However, the experimental and theoretical investigations conducted show that the truss model only describes a part of the whole shear capacity. There is an exceeding remaining load-bearing system. Based on the research results a design model for shear is developed which is applicable for high performance as well as ordinary concrete.

Experimental investigation was conducted to study the pure torsional behavior of sixteen high- (HSC) and normal-strength concrete (NSC) full-size beams with relatively low amounts of torsional reinforcement. The test specimens had variable levels of transverse and longitudinal reinforcements, compressive strength of concrete and aspect ratio of the cross section. The overall behavior, with emphasis on the post-cracking reserve strength, is reported. It was found that the adequacy of post-cracking reserve strength for specimens with the minimum amount of torsional reinforcement specified in the ACI 318-02 is primarily related to the ratio of ?t /?l . Nevertheless, the lower limit of ?total = 1 % should not be ignored. A simple approach to determine the minimum amount of torsional reinforcement is discussed and confirmed by the test results to facilitate the design of torsion for HSC and NSC beams.

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.