Hybrid Concrete Elements with Splitting Fiber Reinforcement Under Two-Dimensional Partial-Area Loading

Abstract

In practice, concrete structures are often subjected to concentrated loads. Under such high stress concentrations, large splitting stresses are generated due to the resulting stress diffusion. In order to resist these splitting stresses, the state of the art is to place transverse steel reinforcement in zones where the most critical splitting stresses occur. An alternative approach gaining increasingly importance, is to add steel fibers to the concrete mixture. Regarding economic concerns, however, it is recommended not to reinforce the entire concrete element with steel fibers, rather in zones where high splitting stresses are expected. Based on this fact, a new design concept to manufacture hybrid concrete elements has been developed.

In this paper, an experimental study on the load-bearing capacity and failure mode of steel fiber reinforced concrete elements under centric strip-loading has been conducted. For this purpose, hybrid concrete specimens (50 × 25 × 50 cm³) containing both plain and fiber concretes were produced. The reference samples were produced only with plain concrete (PC), while the hybrid specimens were additionally strengthened with a layer of high performance steel fiber reinforced concrete (HPSFRC). The thickness and position of this HPSFRC layer has been varied in order to determine the most efficient and economic configuration of the splitting fiber reinforcement.

The test results have shown that the load-bearing capacity could be enhanced up to 200% depending on the thickness and position of the incorporated layer of HPSFRC. As a fundamental finding of this experimental study it is shown that the ratio of fiber reinforcement (e.g. the thickness of the HPFSRC layer) was not solely decisive for the load bearing capacity, rather the position of the reinforcement layer according to the location of the crucial splitting stresses.