Static and fatigue flexural performance of ultra-high performance fiber reinforced concrete slabs

摘要

This paper investigates the static and fatigue flexural performance of ultra-high performance fiber reinforced concrete (UHPFRC) decks on the basis of a 500 m cable-stayed bridge, namely, the Malukou Bridge. A series of numerical studies was conducted on the bridge to reveal the stress level in the deck under service loads, and then two kinds of steel bar reinforced UHPFRC decks with different steel fibers (i.e., hooked-end and straight steel fibers) were fabricated and tested to verify the design safety. Compared with traditional 280 mm-thick ordinary concrete decks, due to the high tensile strength (over 10 MPa) of the UHPFRC in this study, the deck thickness could be reduced to 170 mm with a maximum calculated tensile stress in the deck of 8.82 MPa induced by local wheel loads. Subsequently, the weight of the deck could be reduced by 35% due to the significant reduction in the deck thickness, leading to a smaller compressive stress (13.3 MPa) in the deck under service loads. In addition, in contrast to straight steel fibers, the use of hooked-end steel fibers could had a better advantage to increase in the crack resistance and post-cracking stiffness of the deck specimens. Due to the use of steel fibers and steel bars, cracks in the UHPFRC deck specimens propagated rather slowly under both static and fatigue loads. The deck specimens with hooked-end and straight steel fibers showed superior allowable tensile stresses of 23.2 MPa and 16.1 MPa, respectively, both satisfying the design requirement (8.82 MPa) of the bridge under service loads. The fatigue life of the former deck specimen was revealed as 9 million cycles under the stress range of 1.3-7.0 MPa only with a small reduction in the load carrying capacity, which greatly met the fatigue criteria of Chinese bridge design standards in terms of the crack width in UHPFRC. Based on the numerical and experimental investigations, the design safety of applying the UHPFRC deck was verified for the Malukou Bridge.