Method for coaxially connecting FRP reinforcements by FRP connecting pipe and expansive cement

Abstract

The invention provides a method for coaxially connecting two FRP reinforcements by an FRP connecting pipe and an expansive cement, comprising the following steps of respectively perforating two reinforcements to be connected with coaxial holes, coaxially connecting and positioning the two reinforcements by an FRP extruding / pulling rod or a wire rope, sheathing a section of FRP connecting pipe at the joint of the reinforcements; carrying out coaxial positioning by a positioning ring at two ends of the connecting pipe; arranging a pouring opening / air outlet on the positioning ring during horizontal pouring process and injecting expansive cement solution between the reinforcements and the connecting pipe by the pouring opening; needing not to arrange the pouring opening / air outlet on the positioning ring during vertical pouring process, firstly installing and then sealing the lower positioning ring; putting the upper sealing ring in place after completing pouring the cement solution to be expanded from the upper opening along the wall of the FRP connecting pipe, thus ensuring the coaxiality of the reinforcements and the sheathed pipes. The hardening time of the expansive cement is 6-12 hours generally. The FRP pipe can be prefabricated, the quality thereof is easy to be controlled, the cost of the expansive cement is low, the connection construction is simple and convenient, and the connecting part prepared by the expansive cement has light weight, high strength and corrosion resistance and can be used for structures with demagnetization requirements.

Description

technical field [0001] The invention belongs to the field of composite material structures, and relates to a connection technology of composite materials, in particular to a method for coaxially connecting FRP tendons. Background technique [0002] Cracks or micro-cracks will appear in the traditional reinforced concrete structure during use. When encountering sea water or salty snow water (sprinkling salt to form salty snow water for melting snow) or corrosive gas liquid, the steel bar will be corroded. , resulting in the decline or complete loss of the structural bearing capacity; when there is a high-frequency electromagnetic field around, the steel bars will generate heat due to the dual current effect, resulting in thermal stress and cracking of the concrete; widely used in water conservancy and hydropower projects, deep foundations, underground structures , slope stability, mine roadway support, etc. may be corroded due to the interaction with groundwater and the chemi...

AI Technical Summary

Problems solved by technology

[0005] There are several ways to connect steel bars: lap joint, welding and mechanical connection, but because thermosetting FRP bars do not have weldability and cold bendability; although thermoplastic FRP bars can be welded, the essence is the welding of the matrix, which plays a major role. The load-bearing fibers cannot be welded, and the strength and stiffness of FRP tendons are anisotropic, and the extrusion strength and interlayer properties are weak. It is a brittle material, and there is no substantial yield deformation during failure, and the ability to redistribute loads Therefore, the connection methods suitable for steel bar connection such as welding, ribbed steel sleeve extrusion connection, steel bar taper thread connection, steel bar upsetting and rolling straight thread connection, molten metal filling sleeve connection, etc. are not suitable for FRP bars.

Lap-bonding connections can also be used in FRP-reinforced concrete structures, but it is clearly stipulated in the reinforced concrete specifications that no lap-bonding joints should be used for longitudinally stressed steel bars under axial tension and small eccentric tension; When the diameter of the steel bar is greater than 28mm and the diameter of the compression steel bar is greater than 32mm, it is not suitable to use lap joints; for components that need to be checked for fatigue, the longitudinal tensile steel bars must not use lap joints, etc. It is necessary to research and develop effective coaxial connection methods to meet the needs of practical engineering

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