Experimental Study On Connection Performance Of Fully-grouted Sleeve Under Freeze-thaw Cycles

In recent years,an increasing number of buildings and Bridges have been built along coasts and estuaries,most of them prefabricated.Due to the impact of freeze-thaw cycles on the mechanical properties of building structures in offshore environment,the durability of structures is reduced.Therefore,it is particularly important to study freeze-thaw damage.Among them,the key to ensure the safety and stability of the structure lies in the performance of the connection nodes between the precast assembled members.For this reason,the sleeve grouting connection technology has become a key research direction of the academic circle as one of the reinforcing bar connection methods.In this paper,an experimental study was conducted on the connection performance of fully grouted sleeve connection members under the action of freeze-thaw cycles,and the frost resistance durability of fully grouted sleeve connection members in prefabricated structures was explored.The main research contents and achievements are as follows:(1)The 40mm×40mm×160mm prism grouting material test block and standard full grouting sleeve joint specimens were made according to the specifications,and the fluidity test,quality test,flexural strength test,compressive strength test and unidirectional tensile test of the grouting sleeve joint specimens were carried out on the grouting material.(2)The failure pattern of the specimen was observed.After the freeze-thaw cycle,the grouting material at the port changed from cone-shaped failure to broken grouting material.The sleeve connectors may have three kinds of failure modes: reinforcement pulling out,reinforcement scraping plough pulling out and sleeve sliding wire.In this test,within 75 freeze-thaw cycles,all specimens of the full grouting sleeve joint suffered tensile failure of the steel bar,while when it reached 100 freeze-thaw cycles,part of the specimens suffered scrape-plough pull-out failure of the steel bar.(3)The freeze-thaw cycle can affect the failure displacement,ultimate bearing capacity and ultimate bond strength of the specimen of full grouting sleeve joint to some extent.Compared with the sleeve joint specimens under normal temperature curing,the average failure displacement of the specimens subjected to freeze-thaw cycles increases by about 6% ～ 35%.The more the number of freeze-thaw cycles,the more the ultimate bearing capacity decreases.After 75 freeze-thaw cycles,the ultimate bond strength of the specimens decreased by 3.7% to 10.3% on average.(4)In this paper,ABAQUS finite element software is used to simulate and analyze the sleeve specimen.By establishing the finite element model of the full grouting sleeve under the action of freeze-thaw cycle,the ultimate bearing capacity,failure mode and damage depth of the grouting material of the sleeve joint specimen after the action of freeze-thaw cycle are analyzed to verify the experimental results.