It is necessary to pay attention to the bonding strength of the interface between precast normal strength concrete (NSC) and cast‐in‐place epoxy resin concrete (EMR) when using EMR as a repair or filling material or an overlay in bridges’ rehabilitation. However, the performances of epoxy concrete are different due to differential mix ratios; thus, the bonding properties between various epoxy resin concrete and cement concrete are not completely the same. This article investigated the interfacial bond properties between NSC and ERC by direct tensile, push‐out, and slant shear test with specimens of special size and structure and observed the interfacial bond strength and corresponding failure modes. The minimum bond strength under direct tension was 0.72 MPa, while the minimum bond strength was 1.71 MPa and 3.19 MPa for the push‐out test and slant shear test, respectively. Results indicated that the slant shear test specimens with an inclination angle of 45° are not suitable for the slant shear test due to higher compressive stress. Furthermore, the cohesion and friction coefficient of interface bond strength were calculated inversely in accordance with the results obtained from the corresponding direct tensile and slant shear tests. The minimum cohesion value was 1.71 MPa, and the minimum friction coefficient value was 0.46.

Modern cable‐stayed bridges are spatial, multicable systems. The cable force needs to be adjusted during the construction phase and maintenance phase. The existing calculation methods of cable force adjustment mainly considered the rationality of structural force, but only few research studies have been conducted on how to reduce the number of stay cables which need to be adjusted. This study aims to propose an optimization calculation method including the optimization module with the sensitivity analysis and updating design variable module (UDVM), which are used for cable force adjustment in cable‐stayed bridges. Based on the finite difference method, the sensitivity analysis is adopted in the optimization module, which can capture the response of structures as design variables vary; the particle swarm optimization method is adopted for structural optimization. The proposed method can dramatically reduce the number of stay cables which need to be adjusted and ensure the main girder stresses remain in a reasonable state during stay cable adjustment progress by UDVM. Moreover, the proposed method can continuously update the objective function, constraint conditions, and design variables. Finally, this proposed optimization calculation method is applied to two different cable‐stayed bridges to validate the reliability and feasibility of the method.

At present, there are few studies on the thermal effect of solar radiation on a separated double‐sided box steel‐concrete composite girder cable‐stayed bridge. In this paper, the beam element and mixed element models are combined with the theory of transient heat transfer analysis and meteorology; this approach is adopted to carry out a thermodynamic analysis of a related bridge project. The calculation results of the thermal field and structural thermodynamic analysis of bridge sections show that, in terms of a separated double‐sided box steel‐concrete composite girder cable‐stayed bridge, the thermal field distributions of the main girder and the pylons are extremely complex under conditions of solar radiation. Therefore, the real thermal field cannot be accurately described as a one‐dimensional temperature gradient. The traditional beam element model cannot accurately simulate the temperature effect, and it will underestimate its thermal effect. The calculated temperature stress values of the mixed element model are quite different from those of the of beam element model. The mixed element model can precisely reflect the local thermal effect of each component in this system under solar radiation. Compared with the calculation results of the beam element model, the maximum temperature stress of the bridge deck in each section of the main girder is generally 20% larger; the maximum temperature stress levels of the steel‐beam top and bottom plates are 14.7 MPa and 15.9 MPa larger, respectively. The maximum shear stress of the steel‐concrete interface is 0.2 MPa larger. The research results of the temperature effect calculated by the mixed element have an important guiding significance for the design and maintenance of bridges.

Recently, epoxy resin concrete (ERC) has shown significant potential in rapid repair applications, such as bridge expansion joints, owing to its early strength gain, rapid hardening, excellent adhesion, and durability. Based on the background of rapid repair scenarios for small- and medium-span bridges, this study designed a mix proportion of ERC. A systematic investigation was conducted on its mechanical properties and constitutive model under various curing temperatures (5 °C, 20 °C, and 35 °C) and ages. Experimental results indicate that the designed ERC cures within 2 to 6 h and achieves a compressive strength of 15 MPa at 1 day, meeting the requirement for early traffic reopening. Both material strength and elastic modulus increase significantly with age, reaching a compressive elastic modulus of 16 GPa at 90 days. Based on the measured uniaxial compressive and tensile stress–strain data, a temperature-dependent constitutive model was established. The fitting parameters exhibit a quadratic functional relationship with curing temperature. The model demonstrates high fitting accuracy under all tested conditions (R² ≥ 0.9293). This study provides a theoretical basis and data support for the application and numerical simulation of ERC in bridge engineering.

To study the size effect in lightweight aggregate concrete (LWC), a two‐dimensional (2D) random aggregate numerical model was established based on the parameters of LC30 and applied to LWC specimens with different sizes. The size effect of LWC under static compression was studied based on the macro‐ and micromechanical failure mode of the material and nominal stress–strain relationship. The results show that the distribution of crack zones along the aggregate boundary in LWC is different from that in ordinary concrete. Cracks in LWC specimens eventually develop into an oblique shear crack band with an angle of 45° from the specimen boundary and pass through the aggregate, showing a stronger size effect. Under identical loading strain conditions, increasing specimen size leads to the formation of multiple, more complex oblique cross‐crack zones in LWC specimens. As specimen size increases, the peak strength and the nominal strain at peak strength decrease gradually, while the damage dissipation energy associated with crack propagation increases. In addition, based on the size effect degrees obtained from different specimens, the size‐effect law for LWC was derived, which provides a promising approach for calculating the strength grade parameters of different‐sized LWC specimens.