For cable-stayed bridges, cables are very important components to maintain the safety of the whole bridge structure. It is well-known that change in cable force reflects the health of the cable-stayed bridge. Therefore, it is necessary to detect and quantify local damage in cables prior to the occurrence of a failure. To this end, an improved residual force algorithm independent of static load vector was proposed in this study. The proposed method mainly makes use of the particularity that only a few coefficients in the residual force and static load vectors are nonzero. By combining two different static loading modes, a new damage indicator vector was defined in the method for damage localization and quantification. Compared with existing static residual force methods, the significant advantage of the proposed algorithm is that the specific value and loading position of the static load are not required in the damage identification process. This special advantage causes this method to not require special static loading, but instead uses any load vehicle. This advantage can make the operation process of structural damage identification based on static tests easier and faster. A single tower cable-stayed bridge structure was used to verify the feasibility of the proposed method in cable damage identification. It was shown that the proposed method successfully identified cable damage, even if the value and loading point of the static load were uncertain.

The recycling and reuse of construction waste have not only effectively protected natural resources but also promoted the sustainable development of the environment. Therefore, in this article, waterborne polyurethane (WPU) as a promising new polymer reinforcement material was proposed to reinforce the road demolition waste (RDW), and the mechanical performance of WPU-reinforced RDW (named PURD) was investigated using triaxial unconsolidated and undrained shear (UU) and Scanning Electron Microscope (SEM) tests. The results showed that under the same curing time and confining pressure, the shear strength of PURD increased with the increase in WPU content. When the WPU content was 6%, the WPU presented the best reinforcement effect on RA. The failure strain of PURD increased with the increase in confining pressure, but increased first and then reduced with the increase in WPU content. The specimens with 5% WPU content showed the best ductility. At the curing time of 7 and 28 days, the internal friction angle and cohesion of PURD increased with the increase in WPU content, and they reached a maximum when the WPU content was 6%. The internal friction angle barely budged, but the cohesion increased obviously. The enhancement effect of WPU was attributed to the spatial reticular membrane structure produced by wrapping and bonding particles with the WPU film. Microscopic analysis showed that with the increase in WPU content, the internal pore and crack size of PURD gradually decreased. As the WPU content increased, the WPU film became increasingly thicker, which increased the adhesion between WPU and RA particles and made the structure of PURD become increasingly denser.

In order to study the effects of recycled aggregate with different particle gradations and different contents on the mechanical properties of cement soil modified by nano-MgO, unconfined compressive strength and scanning electron microscope (SEM) tests were carried out. The cement content was fixed at 15% and the nano-MgO content was 1.5%. The effects of two ages, three recycled aggregate contents, and three recycled aggregate particle gradations were considered. The test results show that the unconfined compressive strength of natural graded (RA), recycled coarse aggregate (SRA), and recycled fine aggregate (TRA) reached the maximum when the content of recycled aggregate was 20%, and the unconfined compressive strength of SRA was higher than that of TRA and RA. The residual strength of RA and SRA samples first increased and then decreased with the increase in recycled aggregate content, and the residual strength of TRA samples increased gradually with the increase in recycled aggregate content. The variation law of peak strain and peak strength of the three particle graded samples was consistent, and the variation law of brittle failure degree was highly consistent with that of residual strength. When the recycled aggregate content of RA, SRA, and TRA samples was 20%, the deformation resistance and stiffness of the samples were the best. In addition, SRA samples showed the best deformation resistance, followed by TRA samples and, finally, RA samples. The smaller the porosity of the sample, the tighter the sample structure and the stronger the bearing capacity of SRA. The unconfined compressive strength of the WPRA sample was represented by an exponentially negative power function of the porosity.