Study On Mechanical Properties Of Self Compacting Concrete With CFRP-PVC Spiral Reinforcement

With the development of science and technology and humanities,the society puts forward higher requirements for the bearing capacity and durability of buildings.Especially in coastal cities,the corrosion ions in air,groundwater and foundation have a great impact on the durability of buildings.For a long time,the durability of reinforced concrete structure has been the focus of engineering circles.CFRP and PVC have good corrosion resistance.Wrapping them outside the structure can not only be used as casting formwork,but also can improve the restraint effect and corrosion resistance.They have natural advantages in economic and structural performance.At present,the research on this kind of structure is focused on plain concrete structure at home and abroad,while the research on the internal spiral reinforcement is less.As a kind of reinforcement form which is easy to bind and has good restraint effect,the mechanical properties of spiral reinforcement and CFRP-PVC clad pipe composite restraint concrete are rarely studied.Based on this,in order to study the mechanical properties(axial compression,low cycle repetition)of self compacting concrete columns with CFRP-PVC-spiral reinforcement composite confinement,the whole process and failure mode of specimens were observed by taking the spacing of spiral reinforcement,diameter of spiral reinforcement and height diameter ratio as variable parameters,and the key curves such as the whole process curve of axial stress-strain,hysteretic curve and skeleton curve were obtained The influence of various parameters on the mechanical properties was studied.On this basis,the finite element software ABAQUS is used to analyze the restraint mechanism and the expansion parameters.The numerical simulation results are in good agreement with the experimental results,and the influence of the expansion parameters on the ultimate bearing capacity is analyzed.Finally,according to Richart’s constraint model,the calculation method of ultimate bearing capacity of self compacting concrete columns with CFRP-PVC-spiral bars is proposed,and the calculation results of test specimens and finite element specimens are calculated respectively.The main research results are as follows:(1)The axial compression tests of 9 self compacting concrete columns with CFRP-PVC-spiral bars were completed.The results show that the larger the spacing of spiral reinforcement is,and the worse the ductility is;the diameter of spiral reinforcement has little effect on the bearing capacity;when the height diameter ratio is between 7.5 and 9,the mechanical properties of the specimens are better.Through the test and finite element analysis,the restraint mechanism of self compacting concrete confined by cfrp-frp pipe and spiral reinforcement is obtained,and the composite restraint model and the corresponding calculation method of axial compression ultimate bearing capacity are established,which has a certain guiding significance for the engineering application of self compacting concrete columns confined by CFRP-PVC spiral reinforcement.(2)The results show that the hysteresis curve of these structures is full bow,with good ability to absorb seismic energy,and the seismic performance is good,while the positive and negative hysteresis curves are asymmetric,and the positive peak bearing capacity is about twice the negative direction;with the increase of the diameter of the spiral bars and the decrease of the spacing between the spiral bars,the results show that the hysteresis curve of this kind of structure is full bow shape,and the positive peak bearing capacity is about twice the negative direction;with the increase of the diameter of the spiral bars and the decrease of the spacing between the spiral bars,the results show that the hysteresis curve of this The smaller the shear span ratio,the higher the peak bearing capacity of the specimens,the more the pitch between the spiral bars and the larger the shear span ratio,the more obvious the lateral stiffness degradation of the specimens,the decrease of the equivalent viscous damping coefficient of each specimen,the gradual enhancement of the energy consumption capacity,and the initial equivalent viscosity damping coefficient of the test piece The coefficient of hysteresis damping decreases gradually;with the increase of the diameter of spiral bars,the ductility coefficient of the specimens decreases first and then increases.When the diameter of spiral bars is10 mm,the seismic performance of CFRP PVC spiral bars to restrain the self compacting concrete columns is the best,which meets the requirements of the specification;with the increase of the spacing of spiral bars,the ductility of the specimens decreases with the increase of the spacing of the spiral bars,and the ductility of the specimens with the height of 800 mm is more than 3,which has better seismic resistance The shear span ratio of the specimen increases first and then decreases with the increase of shear span ratio,and the ductility of the specimen with shear span ratio of 4.62 is the best.(3)ABAQUS finite element software is used to analyze the test specimen,and the calculation results are in good agreement with the test results.Through in-depth analysis of the restraint mechanism,it is found that the failure order of the specimen is: CFRP-PVC,longitudinal reinforcement and spiral reinforcement.The results show that the bearing capacity of the specimens decreases with the increase of the spacing of spiral reinforcement,the decrease of the diameter of longitudinal reinforcement and the decrease of the number of CFRP layers.However,with the fluctuation of the core concrete area,the proportion of the optimal core concrete area is 80%.In general,the existence of CFRP-PVC pipe makes the specimen have obvious premonition before reaching the peak value,and the existence of spiral reinforcement makes the specimen have larger plastic deformation after failure,which meets the requirements of better energy dissipation capacity.