Anti-washout underwater concrete (AWC) is widely used in nondrainage strengthening; however, there still exist some problems with it, such as high strength loss and poor interfacial bond in practical engineering application. Based on the study of self-stressed concrete (SSC), a research on the mix ratio for the C30 self-stressed anti-washout underwater concrete (SSAWC) was carried out in this paper in hope of solving the above problems, specifically, by adding an expansive agent to the AWC. The parameters, such as strength, fluidity, anti-dispersity, and expansibility, were picked as target indices in determination of the mix ratio. The orthogonal test design and range analysis were used to determine the reasonable mix ratio and study the influence of various parameters on the performance of SSAWC. The experimental program conducted includes a series of strength, fluidity, anti-dispersity, and expansibility tests on 18 groups of specimens. The results show that C30 SSAWC has an excellent performance using the optimal mix ratio. Compared with AWC, the expansibility and self-stress of the SSAWC can be easily observed, and the compressive strength ratio of the SSAWC casted in water to that casted in air is much bigger. This implies that SSAWC is applicable to the nondrainage strengthening.

Five square reinforced concrete (RC) stub columns were fabricated and experimental tested under an axial compression load in order to study the effectiveness of strengthening by using prestressed carbon fiber reinforced polymer (CFRP) strips. The specimens tested included one un-strengthened and four strengthened. Three specimens were strengthened by using prestressed strips, and the other one strengthened by using non-prestressed was used to compare. The prestress of the strip was achieved by tensed using a special device before it was pasted to the column. The experimental data such as the failure modes, load-displacement curves and strain distribution of CFRP strips were obtained. The effects of prestress magnitude of CFRP strips on the ultimate bearing capacity and deformation capacity of the specimens were analyzed. The results show that the prestress of CFRP strips can effectively increase the ultimate capacity and delay the crack occurrence of the specimens. And ultimate strain, plastic deformation of the specimens were also improved with increase of prestress magnitude of strip.

Offshore working environment is complex and variable, and sometimes the grouting pipe is blocked and cannot be continued in the offshore wind power jacket foundation. In this paper, the effect of grouting interruption on the mechanical performance of jacket foundation connection was analyzed by numerical simulation. Firstly, a finite element analysis model for the axial force behavior of grouting connection was established, and the validity was verified by existing experiments. Then three different simulation methods of grouting interruption were compared and analyzed. Moreover, the parameters of grouting break position, shear key height, shear key spacing, the thickness of grouting body and the number of shear key were analyzed. Based on the analysis results, a calculation method of bearing capacity for rapid assessment of the grouting interruption was established.

Steel narrowbase tower has been widely used in distribution network in recent years because that it covers an area smaller than the conventional tower, and has stronger wind resistance than concrete pole. In order to fully understand the wind resistance performance of narrow base tower, a vulnerability performance of narrow base tower under different wind speeds was analyzed based on probabilistic reliability theory. According to the damage characteristics of narrow base tower and the corresponding tall structure specification, wind performance level indexes of narrow base tower were established. When calculating the effect of wind load on narrow base tower, the randomness of wind load, material properties and dimensions were considered. The probability of the narrow base tower appearing different degrees of damage under different wind speeds was calculated, and subsequently a wind vulnerability curve of the narrow base tower was drawn. It is found that the severe damage probability of narrow base tower is about 5% when the wind speed is 23.6m/s. And in the case of severe damage probability is 95%, the wind speed reaches 80m/s. Narrow base tower has good resistance to wind disaster.