Overview of the Test Results

Innovative Precast Girders of Fiber and High-Performance Concretes

Fig. 1 Precast pretensioned concrete girders of self-compacted concrete (left) and development of the compressive concrete strength, depending on the water-cement ratio (right).

Fig. 2 Cost structure of industrial buildings constructed of reinforced concrete parts [1].

Fig. 3 Design principle of a conventional pretensioned concrete girder (top) and a pretensioned steelfiber concrete girder (bottom).

Fig. 4 Strutted frame action induced by the end anchorage of the pretensioning force; structural model (left) and crack pattern during testing (right).

Fig. 5 Post-cracking tensile strength of the steelfiber concrete (top) and the contributions to the shear resistance of a steelfiber concrete girder (bottom).

Fig. 6 Pretensioned steelfiber concrete girder; load-deformation behavior (top left), experimental photo (top right) and crack pattern (bottom) [5].

Fig. 7 Comparison between a conventionally reinforced double-T slab (top) and a steelfiber-reinforced double-T slab (bottom).

Fig. 8 Pretensioned double-T slab of steelfiber concrete; load-deformation behavior (top left), dimensions (top right) and crack pattern at q_k = 17.5kN/m² (bottom).

Fig. 9 System solution for stepped supports with double-T slabs [10].

Fig. 10 Experimental UHPC
cylinders without fibers following a compression test (left) and stress-strain behavior of UHPC (with and without fibers) under compression (right).

Fig. 11 Load-deformation behavior of pretensioned UHPC steelfiber girders and results of the numeric investigations.

Fig. 12 Pretensioned concrete girder made of normal concrete without and with UHPC bars.

Fig. 13 Comparison between a girder reinforced according to Neff [14] and a girder with perforated sheet reinforcement; load-deformation behavior (top left), design principle of a hybrid girder (top right) and principal compressive stress plot (bottom).

 The paper reports on the use of steelfiber-reinforced concrete in combination with pretensioned reinforcement for girders and beams. The result, it was found, is an innovative, economical construction product of high technical quality. Based on these findings and the structural models, the use of pretensioned double T-slabs and UHPC girders is demonstrated on pretensioned double-T slabs and UHPC girders. In conclusion, the investigations into innovative hybrid girders with UHPC bars that greatly facilitate the use of UHPC in concrete practice as well as hybrid girders with perforated sheet reinforcement that enable girder systems with very large web openings, are presented.

The stationary production processes offer precast construction optimal possibilities for applying high-performance concretes, for which remarkable developments have taken place (Fig. 1). Self-compacting concretes (SCC), high-performance concretes (HPC) and ultra-high performance concretes (UHPC) are representative for these. As of late, the term “performance-based concrete” is coming into use to describe a concrete made for special applications and utilizations. The result is a multifarious spectrum of optimization possibilities. In this context, the use of fibers also plays an important role....

Innovative Precast Girders of Fiber and High-Performance Concretes

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BFT 09/2010