Due to the sharp and corrosion-prone features of steel fibers, there is a demand for ultra-high-performance concrete (UHPC) reinforced with nonmetallic fibers. In this paper, glass fiber (GF) and the high-performance polypropylene (HPP) fiber were selected to prepare UHPC, and the effects of different fibers on the compressive, tensile and bending properties of UHPC were investigated, experimentally and numerically. Then, the damage evolution of UHPC was further studied numerically, adopting the concrete damaged plasticity (CDP) model. The difference between the simulation values and experimental values was within 5.0%, verifying the reliability of the numerical model. The results indicate that 2.0% fiber content in UHPC provides better mechanical properties. In addition, the glass fiber was more significant in strengthening the effect. Compared with HPP-UHPC, the compressive, tensile and flexural strength of GF-UHPC increased by about 20%, 30% and 40%, respectively. However, the flexural toughness indexes I₅, I₁₀ and I₂₀ of HPP-UHPC were about 1.2, 2.0 and 3.8 times those of GF-UHPC, respectively, showing that the toughening effect of the HPP fiber is better.

This paper introduces a new type of bridge structure: the prefabricated composite box girder with corrugated steel webs, which features use of a composite upper flange and a prestressed tubular bottom flange filled with concrete. To understand the flexural behavior of this new structure, a static experiment was conducted on a 32-m-span tested girder with simply supported boundaries to investigate the deflection, strains, and bending capacity of it. Meanwhile, the tested girder and two hypothetical reference girders were theoretically analyzed according to elementary beam theory to obtain further insight into the flexural failure mechanism and the effectiveness of the different components. The experimental and theoretical results fit well, revealing that the bottom flange dominated the flexural capacity and the tested girder had sufficient bending resistances to meet the requirements specified in bridge design codes. A simplified equation for bending capacity was also proposed. The findings from this research may provide a reference for the application of this type of bridge structure.

Cable-stayed bridges, of which there are up to 500 around the world, are often the first choice for long-span bridges. As stay cables increase in service life, rust becomes the most common challenge. At present, more than 20 cases of replacing corroded cables are underway worldwide. Inspections of replaced cables prove that corrosion is a leading cause of degradation in the mechanical behavior of cables. However, there is no accurate method of describing the law of degradation of the mechanical behavior of corroded cables and it remains impossible to evaluate the safety of stay cables in a timely fashion. Therefore, this paper reports a study on distribution model of steel wire corrosion, corrosion rate, and mechanical model of corroded cables, establishing governing equations for static configuration and in-plane free vibration of corroded cables. The paper also derives some analytical solutions for both the static and dynamic characteristics of corroded cables. The finite element method is adopted for the simulation and computation of the static and dynamic characteristics of corroded cables to reach, through comparison and analysis of the results of the two methods, the following conclusions. As corrosion time increases, the horizontal cable force of the corroded cable decreases nonlinearly, cable sag increases nonlinearly, and natural frequencies in-plane of the corroded cable present nonlinear reduction. In early corrosion stage, relative change of static and dynamic characteristics of cables is extremely small. For a corrosion time of 12 years, the average cross section area loss rate in cable corrosion region is 30%, but horizontal cable force is only reduced by 1%, cable sag rises only by 1%, and the decrease of each natural frequency in the plane is only 0.54%.

This paper investigates the bond failure performance between precast normal concrete (NC) and cast-in situ ultra-high performance concrete (UHPC), emphasizing the influence of interfacial roughness. The interfacial bonding behavior under tension and under shear was investigated based on 72 groups of pull-off tests and 36 groups of bi-shear tests, considering six different interface treatment methods and two different NC strength levels. The results demonstrate that certain interfacial roughness is essential to gain a reliable bond connection between NC and UHPC. Its enhancement on the tensile bond performance could be described by the positive linear relationship between the mean roughness and the pull-off strength. However, further research is required to determine the characterization method of its influence on the shear bond performance. The higher strength of the base concrete is beneficial to the bond performance. Though this effect is evident in the pull-off tests under tension, the influence on the shear interfacial performance could be offset by that of the interface morphology in the case with high interfacial roughness.

Many in-service bridges with steel–concrete composite beams are currently aging and experiencing performance deterioration. Under long-term cyclic loads from traffic on bridges, headed shear studs in steel–concrete composite beams are vulnerable to fatigue damage. The comprehensive understanding of fatigue behaviors and the feasible detection of fatigue damage of headed shear studs is, thus, crucial for the accurate numerical simulation of the fatigue crack propagation process. The paper, thus, experimentally investigates the fatigue behaviors of headed shear studs through push-out tests of three specimens. The fatigue failure modes and cyclic strain evolution of specimens are analyzed. The fatigue lives of headed shear studs are compared with the S–N curves of the AASHTO, Eurocode 4 and BS5400 codes. The fatigue crack details of shear studs in push-out tests are then detected using the ultrasonic non-destructive testing. The results show that the root fracture is the main fatigue failure mode of shear studs under fatigue loading. The fatigue life estimations based on the three current codes (i.e., AASHTO, Eurocode 4 and BS5400) can be safely guaranteed only with different safety redundancies. The strain at the shear stud with fatigue damage shows a consistent increasing trend followed by decreasing behavior after reaching the peak value with the loading cycles. Moreover, the feasibility of the ultrasonic non-destructive testing with the combination of a strain measurement for fatigue crack details detection of headed shear studs in composite beams is proved.