Abstract:Cold casting header anchor cable is the main structural form of the domestic bridge cable, the cable body consists of a number of steel wires with the same diameter twisted concentrically, covered with polyethylene sheath made of anchor cup filled with epoxy resin, zinc powder and cast steel pill composition of epoxy mortar. The FRP-OFBG bar with the same diameter as the steel wire is implanted into the cable body when the cable is being made, and the two ends of the bar are fixed by the epoxy mortar in the anchor cup to maintain a coordinated deformation with the cable body to form a fiber-optic grating cold-cast header anchor smart cable. In the paper, the strain and temperature sensing performance of FRP-OFBG tendons, the sensing performance of the smart cable and the engineering applications are studied. The results show that the fiber optic grating cold-cast header anchor zip line has excellent sensing performance and can be used for construction monitoring and operation monitoring of the zip line.

Abstract:This paper firstly discusses the advantages of single tower cable-stayed bridges in terms of economy, force analysis and construction, and then discusses various types of single tower cable-stayed bridges in China, including concrete, steel, combined girder and hybrid girder cable-stayed bridges. Finally, the article analyzes several problems of cable-stayed bridges, including span, structural system, and arrangement of beams, towers, cables and other components. The article also lists the parameters and characteristics of single-tower cable-stayed bridges in China, and the parameters of single-tower cable-stayed bridges in foreign countries are attached.

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Abstract:According to the structural characteristics of tension-type and pressure-type prestressing anchors, this paper abstracts the tension-type prestressing anchors to be subjected to a centralized force at the imaginary sliding surface P, and the pressure-type prestressing anchors to be subjected to a centralized force at the bottom of the anchorage holes P. Generally speaking, the hypothetical sliding surface or the bottom of the anchorage holes in the project are far away from the surface of the geotechnical body. Based on the above assumptions and engineering conditions, the prestressing anchor cable is reduced to a Kelvin problem with a concentrated force at one point within the space. The Kelvin stress solution is used to find the axial distribution of shear stress t in the side wall of strand and hole wall of tension-type prestressing anchor cable, and to find the shear stress t and positive stress in the hole wall of pressure-type prestressing anchor cable. The axial distribution of pressure type prestressing anchors is found. According to the results of this paper, it is suggested that the design of tension-type prestressing anchors in rock should be based on the bond strength between the strand and the grouting body. It is suggested that the pressure-type prestressing anchors in the rock body should be improved into pressure-dispersed prestressing anchors by adding a section of steel pipe at the stressed end. It is recommended that the pressure-type prestressing anchor cable in soil body should be improved to expand the head type pressure-type prestressing anchor cable by expanding the hole at the bottom of the hole.

Abstract:This paper first discusses the concept of geohazard prevention and control engineering. Then, it puts forward opinions and suggestions on some issues related to the formulation of prevention and control programs, design principles, survey specifications and technical requirements. Finally, it questions the "single-price contracting" method which is very popular in the current market operation, and advocates the lump-sum contracting according to the overall objectives and actual results.

Abstract:In order to solve the problems of many anchorage devices, complicated structure, expensive cost and easy to damage beams in the upgrading and strengthening of prestressed concrete simple-variable-continuous girder bridges with deep strand joints, Xing Xianjun, a senior engineer of Hebei Provincial Institute of Transportation Planning and Design, put forward the idea of "equal-stress beam technology". This paper introduces the design and implementation method of prestressing equal stress beams in the reinforcement project of Dongyang River Bridge, pointing out that the equal stress beam reinforcement method can effectively save prestressing steel, reduce the amount of anchorage, and is very favorable to the overall structural stress of the bridge.

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