Owing to its light self-weight, low heat capacity and large thermal expansion coefficient, the application of the curved steel box girder bridge with small and medium spans has gained popularity for the construction of urban infrastructure. However, sun exposure could easily increase the maximum temperature difference at the bottom of steel box beam by 25°C. With the effect of nonuniform temperature field and overloaded vehicles, the edge inside the curved steel box girder bridge may be separated from the remaining structure, resulting in overturning. Thus, more attention needs to be paid in order to prevent the separation. In this paper, an overturning resistance analysis of a three-span curved steel box girder bridge located in Hangzhou, China was performed. A model was proposed based on the measurement of temperature field to the steel box girder. The separating displacement due to temperature variations was predicted and verified by the measurement results. As a result, changes in supporting r...

A critical problem in evaluating the structural behavior of simply supported girder bridges is the performance of the transverse connectivity of girders. Traditional structural calibration factors, which are based on loading test results, are only capable of evaluating the load-bearing capacity of girders. To resolve the difficulty in evaluating the transverse connectivity performance of existing simply supported girder bridges, two parameters $P_n$ and $P_m$ were proposed based on the loading tests results of 65 simply supported concrete girder bridges. Moreover, threshold values for these two parameters were specified according to statistical analysis of loading tests results: when $P_n\le 0.3$ or $P_m\le 1.0$ , the bridges perform well as a complete structure in the transverse direction, and only minor repairs are needed; when $P_n>0.3$ or $P_m>1.0$ , the bridges perform poorly in the transverse direction and necessary repairing measures should be taken. Based on the data of the two evaluation parameters of surveyed bridges, a detailed strengthening strategy was established and successfully implemented in 13 field projects. According to the strengthening strategy, the following steps are to be conducted: (1) remove the damage zones in bridges, (2) rebar embedding in hinge joints, (3) install reinforcing steel grids, and (4) concrete repair. Comparative tests were made on bridges before and after the strengthening process. The results confirmed the feasibility and efficiency of the proposed strategy.

Cement asphalt mortar (CAM) in high‐speed lines is subjected to varying environmental conditions, which lead to the deterioration of CAM. The nanoparticles of nano‐SiO₂ and nano‐TiO₂ are added to improve the performance of CAM, and the temperature sensitivity of CAM with nanoparticles is primarily studied in this paper. The flexural strength and compressive strength of CAM with and without nano‐SiO₂ and nano‐TiO₂ were measured and compared to study the effect of nanoparticles on the performance of CAM subjected to different temperatures. Temperature sensitivity factors of flexural and compressive strength based on Arrhenius model were proposed to evaluate the temperature dependence of CAM by nanoparticles. Furthermore, the microstructure of hardened CAM was studied using scan electronic microscope (SEM) to investigate the mechanism of temperature sensitivity of CAM with and without nanoparticles. The results indicated that the flexural and compressive strength of CAM with and without nanoparticles decreased with the increasing temperature; however, the decreasing rate of strength with temperature was different in CAM with and without nanoparticles. The reduction in the decreasing rate of strength was obtained by using nano‐SiO₂ rather than nano‐TiO₂ in CAM. Based on the SEM results, the free asphalt was seen to be greatly reduced in the CAM with nano‐SiO₂, suggesting a positive effect of nano‐SiO₂ on the mitigation of temperature sensitivity of CAM.

The bond strength of plain bars plays an important role in assessing the anchorage capacity of historical buildings. For plain bars, the bond strength greatly depends on the frictional effect, and can easily be affected by the lateral stress around the bars. For bars located in the beam–column joint, the lateral compressive–tensile stresses from gravity and earthquakes might be applied simultaneously. To date, the effect of such biaxial stresses on the bond strength of plain bars has not been evaluated in an analytical manner. Consequently, an analytical approach combining both theoretical and numerical solutions to the bond strength of plain round bars under biaxial tensile compressive stresses is developed. Comparison between test data and the results calculated by the proposed analytical model shows that the model is well capable of predicting the bond strength for different concrete and bars. Moreover, the comparative studies between the proposed analytical model and closed-form solutions show that the partial separation of the bond interface due to the biaxial stresses cannot be ignored in predicting the bond strength of plain bars. Finally, a simplified model with acceptable precision is suggested to substitute for the numerical procedure in the proposed analytical model.

The viscosity of Retard-Hardening Adhesive (RHA) varies with the hardening of resin-based materials and greatly affects the workability and prestress loss of retard-bonded prestressed systems. So far, the effect of aging time on the viscosity of the RHA has not been revealed, which hampers the further application of Retard-Bonded Prestressed Reinforcements. In the current article, therefore, an experimental study is developed to evaluate the effect of aging time on the viscosity of RHA. Different exposure temperatures and hardening periods of RHA are considered in the rheological test. Test results show that when the aging time and exposure temperature remain the same, and as the shear rate increases, the viscosity of the RHA firstly decreases rapidly and then remains basically constant. The peak viscosity increases with the aging time, exposure temperature, or both. The effects of temperature on the peak viscosity are different at different stages of aging. The effect of the hardening period on the peak viscosity can be eliminated by introducing the relative aging time. Finally, an empirical model is suggested to predict the peak viscosity of the RHA at different aging times, and the results show that the proposed model agrees well with the experimental results.