Research On Bond Anchorage Performance Of Light-Weight Ultra-High Performance Concrete With HRB600 High Strength Steel Bar

Light-weight ultra-high performance concrete(LUHPC)is an important development direction of UHPC with broad application prospects in the field of civil engineering.In the context of advocating for new architectural greenization,industrialization,and technological integration,the synergistic use of HRB600 high-strength steel bars with LUHPC becomes a noteworthy issue.To investigate the synergistic behavior between HRB600 high-strength steel bars and LUHPC,this paper conducts beam tests and center pull-out tests to study their bond anchorage performance,analyze and summarize the variation patterns of bond anchorage of HRB600 high-strength steel bars in LUHPC components,and provide a basis for solving corresponding anchorage design issues and contributing to the formulation of relevant specifications.The main work and conclusions of the paper include the following aspects.(1)Three sets of center pull-out tests were conducted with anchorage length as the variable parameter.The failure modes,characteristic strength values of bond anchorage,and average bond-slip curves of the specimens in each set were studied.The critical anchorage length of HRB600 high-strength steel bars in LUHPC components was preliminarily determined,providing a reference for the design and grouping of subsequent beam tests.(2)Eight sets of beam bonding tests were conducted,varying factors such as the volume fraction and type of steel fibers in LUHPC,the presence of transverse reinforcement in the anchorage zone,and the anchorage length.The effects of these factors on the failure mode of specimens,average bond-slip curves,and characteristic values of bond anchorage were analyzed.The experimental results were statistically regressed,and empirical formulas for calculating the characteristic values of bond anchorage were obtained.Additionally,a comparative analysis was performed between the results of the pull-out tests and the beam tests.Under the same conditions,the measured bond strength using the center pull-out test method was approximately 1.1 to 1.2 times that of the beam test method.(3)The internal strain gauged beam test was utilized to analyze the variation pattern of bond stress along the anchorage depth and derive an anchorage position function that reflects this variation pattern.Using the characteristic values calculated by the empirical formula for bond anchorage,the average bond-slip curve was segmented,and in combination with the anchorage position function,a bond-slip constitutive model was established for different anchorage positions.(4)Based on the beam test data,the anchorage length of HRB600 high-strength steel bars in LUHPC was determined using reliability analysis methods.The quantitative relationship between the anchorage length and the cover thickness was derived using theoretical formulas.According to the requirements of Chinese regulations,the anchorage length design values were considered under adverse conditions and compared with the values specified in various international regulations.Finally,it was determined that when the diameter of the steel bars,d,is no more than 20 mm,the anchorage length of HRB600 high-strength steel bars in LUHPC is13 d for reinforced components and 18 d for non-reinforced components.