| As a common bearing form in reinforced concrete structures,local compression(here-inafter referred to as LC),mostly found in the beam supported on the wall,the bridge sup-ported on the pier,the post-tensioned prestressed anchorage zone,etc.However,at present,calculation of the LC bearing capacity is still mostly based on empirical formulae,which is rooted in the fact that researches on the bearing behavior of LC is still insufficient.Based on this,this paper used Strut-and-Tie Model(hereinafter referred to as STM)to study LC bear-ing behavior under axial load in three working conditions,including plain concrete without and with a duct,lightweight concrete without the duct and reactive powder concrete with the duct,and each of the three ones includes three reinforcements:plain concrete,mesh rein-forcement and spiral reinforcement,respectively.The bearing behavior includes the bearing mechanism,namely the transfer mechanism and the failure mechanism,which is qualitative.Additionally,it also includes the calculation of the bearing capacity,which is quantitative.The specific work is as follows:(1)Study on bearing mechanism(1)Study on the bearing mechanism of LC of normal concrete without a ductThrough theoretical analyses and numerical simulations by ABAQUS software,the transfer mechanism of a spatial STM was revealed.The STM consists of four concrete bottle struts and four reinforcement ties,which are connected by the nodes in the intersection zones of the struts and ties.The damage starts from the cracking of LC splitting zone,extends to the central splitting of the bottle struts,then to the shear failure at the ends of the strut,and terminates in the collapse of the bearing plate sinking in this work condition.(2)Study on the bearing mechanism of LC of normal concrete with a ductSame as above,the transfer mechanism in this working condition is largely same as without a duct,but the angle of the strut with a duct is larger than that without the duct.The failure mechanism is also largely same as without the duct,and the differences are:A LC splitting zone with a duct tends to develop along the direction of a duct and occurs earlier;the splitting degree of the strut with duct is larger than that without the duct.(3)Study on the bearing mechanism of LC of lightweight concrete without a duct and reactive powder concrete with a ductBecause only the material properties are changed,the bearing mechanism of LC is sim-ilar to normal concrete without or with the duct,respectively.(2)Study on calculation of the bearing capacity(1)Study on calculation of LC bearing capacity of normal concrete without a ductThrough obtaining the cross-sectional area and the inclination angle of the strut,the formulae for calculating LC bearing capacity of normal concrete in this working condition was derived.Based on this,combined with numerical simulations,the formulae for calcu-lating LC bearing capacity of normal concrete with mesh reinforcement and spiral reinforce-ment in this working condition are derived.By the existing experimental data,the accuracy,variability and applicability of the formulae were validated.(2)Study on calculation of LC bearing capacity of normal concrete with a ductSame as above,the formulae for calculating LC bearing capacity with plain concrete,mesh reinforcement and spiral reinforcement in this working condition were derived.The formulae were validated to be reasonable and feasible by the experiments.(3)Study on calculation of LC bearing capacity of lightweight concrete without a ductBased on the formulae for calculating LC bearing capacity of normal concrete without the duct,the modification factorλ_L of lightweight concrete is introduced to derive the for-mulae for calculating LC bearing capacity in this working condition,and the rationality of the formulae were proved by comparisons with many test data.(4)Study on calculation of LC bearing capacity of reactive powder concrete with a ductBased on the formulae for calculating LC bearing capacity of normal concrete with the duct,the formulae for calculating LC bearing capacity in this working condition were achieved by assuming that the strength enhancement factor of reactive powder concrete is1.1.By experimental validations,the formulae are rational. |
