Study On Mechanical Properties Of Concrete Filled Steel Tubular Members With Built-in GFRP Pipe And Seawater Sand Recycled Block

As an important raw material of concrete,with the development of society,the demand for river sand is increasing,and its usable quantity is increasingly short.Therefore,seeking a material to replace river sand as a raw material of concrete has become a must to solve the problem.Sea Sand is gradually applied to engineering,but the chloride in sea sand will cause steel corrosion.In this thesis,the built-in GFRP pipe is placed in the steel pipe seawater sea sand concrete structure,and the seawater sea sand concrete is wrapped with GFRP pipe,and the GFRP pipe and the steel pipe are separated by ordinary concrete,which avoids the erosion and damage of the steel pipe,At the same time,waste concrete blocks can be added to fresh concrete to reduce the amount of material.At present,there are many composite structures mainly formed by a variety of materials,usually with good axial compression performance,but the bias and pure bending properties need to be further verified,t This article conducts eccentric compression and pure bending tests on the steel pipe components of the new composite structure to study the failure mode and changes in mechanical properties of the new composite structure.The specific work carried out is as follows:(1)The effects of different variables on the partial pressure performance of the specimen were mainly studied by taking concrete substitution rate,GFRP pipe size,core concrete strength,segment number and eccentricity as the main parameters.The test process and failure patterns of 13 bias specimens were described,and the test data was processed to obtain the bias performance of the specimens,such as bias bearing capacity-displacement curve,load-strain curve and ductility coefficient.The test results show that the replacement rate of recycled block concrete is increased within a certain range,and the change of the number of segments has little effect on the peak bearing capacity,and the ductility of the specimen is improved.However,with the increase of the eccentricity of the specimen,The peak load-bearing capacity of the specimen is significantly reduced.The improvement of the strength of the core concrete has little effect on the peak bearing capacity,and the thickening of the inner pipe thickness will strengthen the constraint on the core concrete,when the size of the inner tube decreases,the peak displacement decreases,and the ductility of the specimen becomes worse.(2)The effects of different variables on the pure bending mechanical properties of the specimen were mainly studied by taking the concrete substitution rate,GFRP pipe size,core concrete strength and number of segments as the main parameters.The test process and failure morphology of eight pure bending specimens were described,and the pure bending properties such as deflection curve,pure bending bearing capacity and mid-span bending moment were also comparatively analyzed.The test results show that the built-in GFRP pipe seawater sea sand recycled block concrete steel pipe beam can be basically equivalent to the sea sand concrete beam,and it shows good pure bending performance.(3)Using Abaqus finite element software to carry on the numerical simulation calculation and comparing the experimental data with the simulation data.Numerical simulations were carried out using Abaqus finite element software,and the experimental results were compared and analyzed with the simulation results.The simulation results show that: the calculated results were basically consistent with the experimental results,and the reliability of the model were verified This study provided a theoretical basis for the analysis of eccentric compression and pure bending mechanical properties of marine sand reclaimed concrete filled steel tubular members with GFRP tubes.(4)Through the relevant formula of concrete steel pipe components of built-in GFRP pipe seawater sea sand regeneration,and the calculated value of the formula in this thesis is compared with the experimental value,the reliability of the formula is verified.This thesis has 42 pictures,15 tables and 101 references.