| Pre-stress technology is widely used in bridge engineering,and the inspection and evaluation of Pre-stress tensioning quality is fundamental in guaranteeing the safety of the entire life cycle of the bridge.In recent years,with the rise of prefabricated assembly technology and the optimization of construction methods,a large number of newly built bridges and prefabricated beams require the inspection and evaluation of pre-stress tensioning quality in a short period of time.The retraction method has become the most widely used technology in the practical application of quality inspection of Pre-stress tensioning in newly built bridges due to its low cost,strong applicability,and high reliability.However,the traditional retraction method suffers from low detection efficiency and long cycle due to its one-by-one inspection approach.Additionally,the evaluation standards for Pre-stress tensioning quality vary across different provinces and cities and lack a reliable theoretical basis.Therefore,the primary task of Pre-stress tensioning quality inspection and evaluation is to improve detection efficiency and propose applicable evaluation standards.In light of this,based on the basic principles of traditional retraction method,this study proposes a whole-hole retraction method through theoretical analysis,experimental research and other means,and refines the detection value formula for this method by combining it with the research results on anchorage gripping force.This method aims to obtain the anchorage tensioning force detection values of each strand in a hole by collectively retracting multiple steel strands,significantly improving the efficiency of Pre-stress testing.On the other hand,relying on a large amount of engineering measurement data and using mathematical statistics techniques for processing and analysis,a reliable and widely applicable evaluation standard of Pre-stress tensioning quality is proposed based on the reliability theory.The main contents of this study are as follows:(1)Firstly,a literature review was conducted on Pre-stress inspection technology and Pre-stress tensioning quality evaluation indicators.The detection mechanisms and advantages and disadvantages of various types of Pre-stress detection technologies were analyzed,and a research plan for the whole-hole retraction method testing technology was proposed based on traditional retraction technology testing to address the issue of low detection efficiency in current engineering projects.To address the lack of theoretical basis and applicability in Pre-stress tensioning quality evaluation standards,optimization recommendations for Pre-stress tensioning quality evaluation standards based on reliability theory and analysis of measured data were proposed.(2)Through theoretical analysis of the whole-hole retraction method,the theoretical test curve and theoretical value formula for the detection value were initially proposed.The regularity of the whole-hole retraction method test curve was studied through experiments on the anchoring system of one,three,and five-strand steel cables under different anchoring lengths and post-tensioning forces.Combined with the detection mechanism of the whole-hole retraction method,the regularity of the test curve was analyzed,and typical test curves and detection value methods were further proposed.(3)Combining the study of anchorage gripping force(the force that needs to be overcome when the wedge is pulled out),the formula for the detection value of the wholehole retraction method was improved,increasing the accuracy of the detection values.Through indoor experiments and finite element analysis,the influencing factors and changing trends of anchorage gripping force were explored.Through an in-depth study of anchorage gripping force,the formula for detection values of the whole-hole retraction method was further optimized,improving the accuracy of detection values.(4)Based on actual engineering data,this study proposes suggestions for standard values of sectionalized anchorage tensioning force and optimized Pre-stress tensioning quality evaluation standards.Relying on a large amount of post-tensioning force detection data from actual projects,the measured data were divided into four sections according to the length of the tensioning length of steel strands: within 20 m,20m-40 m,40m-70 m,and above 70 m.The data were processed using mathematical statistics,and it was found that the measured values of anchor tension in each section are basically in accordance with a normal distribution.The corresponding normal distribution curve formula was fitted.Based on the relevant parameters of the normal distribution fitting curve,suggestions for standard values of sectionalized anchorage tensioning force and optimized Pre-stress tensioning quality evaluation standards were proposed based on the reliability theory.In conclusion,this study successfully applied the whole-core retraction method detection technology in a laboratory environment and provided a preliminary feasibility judgment of this technology through the analysis of experimental data.The study provides theoretical and technical support for the practical application of the whole-core retraction method,contributing to the improvement of efficiency in Pre-stress detection.Additionally,the study proposes suggestions for the optimization of Pre-stress tensioning quality evaluation based on the theoretical support of the anchorage gripping force evaluation standard,which greatly improves the applicability and reliability of the evaluation standard. |
