Experimental Study On Lapping Performance Of Spiral Stirrup-Corrugated Pipe Grouting Connection Under Cyclic Load

In recent years,with the development of social economy,assembled concrete structure has become an important means to realize green building,sustainable economic development and promote ecological civilization,and has been widely used in the construction industry.At the same time,China as a large grain country,grain reserve safety is the fundamental of national economic development and continuity,granary construction also needs to follow the green development strategy,and the assembled structure provides a new development direction for granary construction.Under grain load,the granary wall is out-of-plane stressed,and the wall is in repeated tension during the grain loading and unloading process.Therefore,this paper proposes a spiral hoop-bellows slurry anchor connection technology for assembled granary and studies the lap connection performance of this connection technology under cyclic loading.In this paper,a combination of experimental study and finite element analysis was used to investigate the performance of spiral stirrup-corrugated pipe grouting connection under cyclic loading,analyzing the damage mode,crack development and the effect of different influencing factors on the lap connection performance of the specimens,and predicting the bond strength between the reinforcement and grout using the random forest algorithm,with the following main studies and conclusions:(1)Tensile tests of spiral stirrup-corrugated pipe grouting connection specimens(72specimens)under cyclic loading were carried out,and the influence of different influencing factors on the lap performance was analyzed.The results showed that: the damage of the specimens were mainly divided into three types,the damage of anchorage at the loading end,the damage of concrete cracking at the loading end and the damage of reinforcement pullout;the ultimate load capacity and plastic displacement of the specimens increased with the increase of reinforcement diameter and lap length under cyclic loading;the ultimate load capacity of the specimens increased with the increase of bellows diameter;the ultimate load of the specimens under unidirectional tensile loading was higher than that of the specimens under repeated loading.The ultimate load of the specimens under one-way tensile loading was higher than that under repeated loading;the ductility of the specimens under one-way loading was better than that of repeated loading,but the overall ductility of the specimens was bad.(2)The finite element analysis software ABAQUS was used to model and analyze the spiral stirrup-corrugated pipe grouting connection specimens and carry out the parametric analysis.The results show that the simulation results are in good agreement with the test results,when the lap reinforcement yields,the strain values of the spiral hoop at 1/4 at 1/2 and 3/4decrease with the increase of the volume reinforcement rate,and the cohesive is defined between the lap reinforcement and the grout,which can make a more accurate simulation analysis of the bond slip between the lap reinforcement and the grout.(3)Based on the mechanical model of the concrete interface of the spiral stirrupcorrugated pipe grouting connection specimen,the equation of the ultimate lap length for the crack development to the outer diameter of the spiral hoop was derived.The theoretical calculated values of the lap length of the reinforcement under repeated tensile loading have small errors with the experimental values;the lap length is not less than 10 d when the reinforcement diameters are taken as 14 mm and 16 mm and the hole diameter ratio is 3.57～4.28.(4)Based on the random forest algorithm,the bond strength prediction model between the interface of lap reinforcement and grout was established with different influencing factors as output variables and bond strength as output quantity.The results show that the random forest prediction model established in this paper is more accurate in predicting the bond strength at the interface between reinforcement and grout,and the error between the predicted value and the experimental value is small,which can be used to predict the bond strength at the interface between reinforcement and grout.