Influence Of Humidity On Stress And Deformation Of Concrete Structure

The performance of concrete materials is affected by humidity and there is swelling property,so the internal humidity changes will affect the performance of concrete structures in the water environment.At present,there are few studies on the influence of humidity on the mechanical behavior of concrete structures,and mainly focus on the research of the basic properties of concrete materials.Based on physical experiments,theoretical derivation and numerical simulation methods,this paper systematically studies the variation of mechanical properties of concrete member to structures,and provides references for the design of concrete structures in water environment.The main work and conclusions of the paper include the following aspects:(1)The water saturation diffusion coefficient of C30 concrete is reversed by the capillary water absorption theory in the one-dimensional water absorption test of the test block,and the moisture field characterization model of the concrete test block is established based on Fick’s second law.The simulated water absorption and water absorption height curves with time are in good agreement with the experiment,which verifies the rationality of the inversion parameters and model.(2)Based on the flat section assumption,the analytical expression of the stress and displacement of the simply supported beam is derived.The theoretical results are in agreement with the experimental results,which verifies the reliability of the theoretical derivation.The humidity in the simply supported beam of the concrete varies non-uniformly along the height of the beam.the deflection of simply supported beam increases with the increase of the ratio of water diffusion height to beam height.The rate of change of the deflection is related to the water absorption rate.According to the derivation formula,the change of elastic modulus and swelling effect of concrete caused by humidity and the effect of the combined effect on the stress and strain of the beam are studied.The results show that the elastic modulus caused by humidity causes the beam stiffness to increase,which is favorable to the structure and has little influence on the stress of the simply supported beam.It can be neglected;the swelling effect causes the self-generated stress in the beam and dominate the combined effect of the two.The effect is unfavorable to the structure.In the structural design of direct contact with water,it is necessary to consider the effect of swelling on the mechanical properties of the structure.The higher the concrete grade strength,the smaller the water diffusion effect and the smaller the humidity effect.Increasing the concrete grade or adopting waterproof measures is an important measure to reduce the influence of humidity.(3)Based on the Comsol Multiphysics software,the finite element model of the influence of humidity on the deformation of the statically indeterminate beam is established,and compared with the simply supported beam with humidity effect,the deformation law of humidity under different constraints is studied.The statically indeterminate beam produces vertical and reverse arch deformation.This deformation law is inconsistent with the downward deformation of the simply supported beam,but the deformation law is consistent with the flat section assumption.The influence of humidity on the statically indeterminate beam is more obvious than that of the simply supported beam.The law of humidity distribution affects the change of the stress curve inside the beam.When the humidity is applied,the statically indeterminate beam is in a purely pressurized state,and the compressive stress includes the self-generated stress generated by the humidity and the additional stress generated by the constraint.Humidity will aggravate the compression of the pressurized statically indeterminate structure.Therefore,it is necessary to consider the influence of humidity on the mechanical properties of the compressed statically indeterminate structure.(4)Based on the water transport model,considering the variation of concrete elastic modulus with humidity and the effect of swelling,the aqueduct wall humidity field and stress field analysis model are established in order to analyze the influence of different diffusion depth along aqueduct wall thickness on its deformation and internal force performance.The research results show that with the increase of water transfer time,the diffusion depth is non-uniformly distributed along wall thickness of aqueduct,and the diffusion depth of the humidity affects the deformation and stress distribution of the aqueduct.As the diffusion depth increases,the longitudinal deflection of the aqueduct increases,while the transverse deformation decreases.The transverse influence is greater than that of the longitudinal.The compressive stress on the inner side of the aqueduct wall increases and the outer tensile stress increases because of the increase of humidity.The humidity is favorable to the aqueduct structure safety,but it is unfavorable to the outer crack resistance.