Maintenance,Repair,and Reinforcement Measures for Dilapidated Small and Medium-Sized Bridges

The paper initiates by exploring the importance of maintaining,repairing,and reinforcing bridges.Subsequently,it delves into routine and preventative maintenance measures tailored for small to medium-sized bridges.Additionally,the paper examines repair and reinforcement techniques specifically designed for deteriorated small and medium-sized bridges,encompassing methods for fortifying both the bridge foundation and upper and lower structures.Lastly,the paper proposes suggestions aimed at fostering discussions and exchanges on the development of maintenance and repair processes for deteriorated small and medium-sized bridges.

Research progresses on equipment technologies used in safety inspection,repair,and reinforcement for deepwater dams

China’s many dams are increasingly facing safety problems resulting from the natural aging of the dam hydraulic structure and geological disasters such as earthquakes under the operating condition of holding a vast amount of water.Problems such as dam leakage and concrete cracking and erosion seriously affect the normal operation and effectiveness of a reservior.It is impossible to empty a large reservoir with a high dam for many reasons,such as serious environmental consequences,and it is thus difficult to detect the working conditions of the underwater part of the facility.There is an increasingly urgent demand for detection and repair technologies that can be used in the deepwater environment.Indeed,there are cutting-edge deepwater detection and processing technologies for hidden dangers in dam engineering.The core technologies include underwater detection equipment,diving technologies,and underwater operation technologies.This paper analyzes safety-oriented detection equipment recently used in unmanned detection,manned detection,and deepwater diver detection from the viewpoint of practical application.The paper further reviews 100-m-depth-class technologies and applications of safety inspection,repair,and reinforcement equiment in the deepwater environment of reservoir dams.An outlook is provided on technology trends of deepwater detection,repair,and reinforcement and critical problems.

Effect of Shrinkage Reducing Agent and Steel Fiber on the Fluidity and Cracking Performance of Ultra-High Performance Concrete

Due to the low water-cement ratio of ultra-high-performance concrete(UHPC),fluidity and shrinkage cracking are key aspects determining the performance and durability of this type of concrete.In this study,the effects of different types of cementitious materials,chemical shrinkage-reducing agents(SRA)and steel fiber(SF)were assessed.Compared with M2-UHPC and M3-UHPC,M1-UHPC was found to have better fluidity and shrinkage cracking performance.Moreover,different SRA incorporation methods,dosage and different SF types and aspect ratios were implemented.The incorporation of SRA and SF led to a decrease in the fluidity of UHPC.SRA internal content of 1%(NSRA-1%),SRA external content of 1%(WSRA-1%),STS-0.22 and STE-0.7 decreased the fluidity of UHPC by 3.3%,8.3%,9.2%and 25%,respectively.However,SRA and SF improved the UHPC shrinkage cracking performance.NSRA-1%and STE-0.7 reduced the shrinkage value of UHPC by 40%and 60%,respectively,and increased the crack resistance by 338%and 175%,respectively.In addition,the addition of SF was observed to make the microstructure of UHPC more compact,and the compressive strength and flexural strength of 28 d were increased by 26.9%and 19.9%,respectively.