| Reactive powder concrete(RPC)attracted the attention of the civil engineering circle once it was published and was widely used in practical engineering,due to its outstanding advantages such as high compressive strength,high tensile strength,good toughness,excellent durability,and no shrinkage and the creep decrease significantly after thermal curing.HRB500 grade steel bars with the characteristics of high strength and good ductility has been widely employed as the dominant steel bars of non-prestressed concrete structures in developed countries.The material properties of the reinforcement and RPC were expected to be more effectively utilized,when the RPC column internally reinforced with HRB500 grade steel bar.The cross-sectional dimension will be gradually reduced and the slenderness ratio will be gradually increased for the concrete columns as the application of high-strength materials.The short and medium-long concrete columns will be transformed into the long and slender columns.Correspondingly,the mechanical behavior of the concrete column will be changed greatly,especially the effect of second-order effect is more obivious.At present,the research on RPC mainly focuses on the performances of flexural and shear resistance.There were few studies on RPC compression members,and the research on the performance of RPC medium long columns on HRB500 steel reinforcement was rarely reported.Therefore,this paper is in the national key research and development plan "Key technology integration and demonstration of new structural application of fiber reinforced composite materials"(No.:2017YFC0703008)and the National Natural Science Foundation "Research on seismic performance and design method of reactive powder concrete compression members" project approval No.: 51878262)Under the auspices,the mechanical performance of the medium-long RPC colum internally reinforced with HRB500 grade steel bar under the eccentric compression was experimentally investigated and theoretically analyzed,The main contents are obtained as follows:(1)Based on the mechanical properties of RPC,four medium-long RPC colums internally reinforced with HRB500 grade steel bar under the eccentric compression were designed and fabricated with considering the eccentric distance as the test parameter.Then,the corresponding experiment was conducted to investigate the effect of eccentric distance on the lateral deflection,the compressive edge concretestrain and the longitudinal steel strain of the medium-long RPC colums.The compressive bearing capacity and crack width of the tested RPC columns determined by the formulas in the relevant standard were compared with the test results.The results indicated that the crack width of RPC columns under bearing capacity state can be accurately determined by the formulas in the current standard.(2)Based on the test results of the RPC columns under eccentric compression,a nonlinear analysis program for the whole loading process was complied with the software MATLAB.The results determined by the nonlinear analysis program were basically consistent with the experimental results.The parametric analyses were conducted on 30 RPC columns under eccentric compression with the nonlinear analysis program,from which the The effects of eccentricity,slenderness ratio,RPC strength and longitudinal reinforcement ratio on the second-order effect of RPC column internally reinforced with HRB500 steel and HRB400 steel bars under eccentric compression were uncoved.The recommended formula for the amplify factor of eccentric distance applicable to RPC column was provided based on the results obtained from the parametric analyses.(3)Taking The integrated treatment measures,using thin-layer of reinforced reactive powder concrete(RPC),temporary loading at cantilever ends in main span of the bridge before the closure of the main span and reducing the pavement thickness,were proposed to solve the excessive problem of compressive stress in prestressed concrete continuous box girder bridge,when an actual prestressed concrete continuous box girder bridge was selected as project background.The contribution of RPC to the the reinforcement effect of the reinforced section by 58.7% was determined with finite element analysis.The stress state of the reinforced bridge after the application of the integrated treatment measures can meet the requeirement of the stress limit in the current standard.The results obtained from the site test demonstrated that the overall working performance of the reinforced RPC thin-layer and the original structure was very good.The measures developed in the present study can provide a valuable reference for solving the similar problem. |
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