Test piece end reinforcing method in test for FRP rib/anchor rod tensile property

Abstract

The invention provides a method used for reinforcing the end of a specimen during the tensile performance test of FRP reinforcement / anchor, comprising the steps as follows: the end reinforced section of the specimen is provided with a gradient transition section, thus avoiding the stress concentration which is caused by obvious section change at the starting position of the reinforced section; the gradient transition section is achieved by enwinding fiber cloth at the end of the FRP reinforcement / anchor specimen to be processed; according to the nominal external diameter of the reinforcement / anchor and the internal diameter of an external steel sleeve, the length of the transition section and the dimension of the fiber cloth are determined; substrate material with low curing shrinkage rate can be adopted for the substrate to enwind the fiber cloth; the external diameter and the wall thickness of the external steel sleeve can be determined according to the external diameter of the FRP reinforcement / anchor, type and performance of filler, shape and dimension of the clamp of a testing machine and the like; and resin or expansion cement is poured between the fiber cloth reinforced layer and the external steel sleeve so as to form a whole end reinforced section. The method leads the damaged position of the specimen to be distributed at a free section and is beneficial for measuring exact material strength performance.

Description

technical field [0001] The invention belongs to the field of composite materials and mechanical performance testing. 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 chemical composition of the formation, which seriously affects the service life of the anchor; in addition,...

AI Technical Summary

Problems solved by technology

It is now considered to be more effective method: the two ends of a certain length of FRP bars are respectively reinforced with steel sleeves filled with expansion cement or low shrinkage resin binder. However, we have tested the specimens processed by this method. It was found that the failure initiation point of most of the specimens occurred in the steel sleeve near the free section. Through numerical analysis, it was found that this failure mode is inevitable, because the numerical analysis shows that there is an obvious stress concentration phenomenon at this position. , so it is actually difficult to measure the accurate material strength properties of the specimens processed by this method, which needs to be improved

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