To establish the tensile constitutive model of ultra-high performance concrete containing coarse aggregate (CA-UHPC), monotonic and cyclic uniaxial tensile tests for CA-UHPC with fiber volume fractions of 2.5% and 2.0% were conducted. Test results showed that CA-UHPC exhibits approximately linear stress-strain relation up to the tensile strength, and tensile softening response composed of the smeared- and localized-cracking stages, regardless of the tested fiber contents. Based on the monotonic test data, the tensile stress-crack opening model of CA-UHPC was established, and the model was further simplified into tri-linear relation. Based on the cyclic test results, tensile damage evolution laws according to the strain equivalence principle and the energy equivalence principle were developed, respectively. Finally, the proposed tensile constitutive model and the calibrated tensile damage evolution laws were demonstrated to effectively predict the mechanical response of CA-UHPC members under both monotonic tension and cyclic tension through numerical simulations.@en

To investigate the fatigue performance and fatigue damage process of the Orthotropic Steel Deck (OSD) - Ultra-High Performance Concrete (UHPC) composite bridge deck, a two-span continuous full-scale specimen was designed and tested under cyclic loading. Test results showed that the fatigue cracks firstly initiated near the lower part of the weld toe of the rib-to-cross beam welded joint, and then cracks along the weld length of the U-rib butt-welded joint developed. These observations followed by the OSD-UHPC interface debonding. The U-rib bolted joint exhibited better fatigue resistance than the U-rib butt-welded joint. The S-N curves of the rib-to-cross beam welded joint, the U-rib butt-welded joint and the U-rib bolted joint were established based on existing fatigue test data, and were compared with provisions in design codes. The S-N curves from the beam test for the short-headed stud connectors were compared with that from the push-out test. And the established S-N curves with 95% survival probability from the push-out test could be used to assess the global fatigue performance of the composite deck. Considering the durability-based critical crack width of UHPC, the established tensile S-N curve regarding critical UHPC crack width of 0.05 mm could be used to evaluate the anti-fatigue cracking ability of the UHPC layer in the composite deck system.@en

In recent years, ultra-high performance concrete (UHPC) has been introduced in the design of orthotropic steel decks (OSD) to reduce the risk of fatigue cracking. To investigate the fatigue behaviour and fatigue damage process of the orthotropic steel-UHPC composite bridge deck, a fullscale specimen was designed and tested under cyclic loading. Test results show that the fatigue resistance of orthotropic steel-UHPC composite bridge deck satisfies the requirements of the designed vehicle load up to 2 million cycles with no cracks occurred in this phase. Rib-to-crossbeam weld and U-rib butt-welded connection are the two most vulnerable details to crack in OSD under cyclic loading. The fatigue resistance of U-rib bolted connection was investigated, and it is concluded that it performs better than that of U-rib butt-welded connection. The short-headed studs fractured under excessive cyclic loading and 5 types of the fatigue failure modes are identified. And the UHPC layer above the crossbeam exhibited limited number of cracks with the maximum crack width less than 0.05mm at the end of the cyclic, much beyond the requirements.@en

In order to investigate load-carrying capacity, ductility and plastic development of orthotropic steel-concrete composite deck used in composite girder cable-stayed bridge, six single-point-loaded simply-supported orthotropic steel-concrete composite decks with varying axial compressive forces and different concrete grades were designed and tested. The test results show that the failure modes of all specimens are similar and exhibit cracks of the lower concrete section combined with crushing of the upper concrete section at midspan. The axial compressive force imposed in this test has a neglected effect on elastic stiffness and vertical load-carrying capacity of tested specimens. While the axial compressive force considerably lowers the ductility and plastic development of the orthotropic steel-concrete composite deck under vertical load. Besides, improving concrete grade from C60 to C80 could not help to enhance elastic stiffness, vertical load-carrying capacity, ductility and plastic development of the composite deck.

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The short-headed stud connectors play a critical role on the interaction of the orthotropic steel deck (OSD) and the ultra-high performance concrete (UHPC) layer in orthotropic steel-UHPC composite bridge deck. In this paper, the fatigue behavior of these short-headed stud connectors was experimentally investigated in a beam test. The failure modes of the short-headed stud connectors were identified and classified into 5 types. The fatigue test results were analyzed by linear regression analysis neglecting run-outs and treating run-outs as failure respectively. On the other hand, the maximum likelihood estimation (MLE) approach was used to shape the S-N curve by considering the influence of run-outs. Additionally, the push-out and beam fatigue test data were compared, and the push-out test presented a relatively conservative result. Last, the applicability of existing specifications on design guidelines regarding the short-headed stud connectors design in orthotropic steel–UHPC composite bridge deck is discussed, and a design S-N curve with 95% survival probability is proposed.

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