| As one of the industrial wastes with the largest annual discharge and accumulated stock in our country,coal gangue not only brings huge economic losses to mining areas,but also poses a great threat to people’s normal life,therefore,its comprehensive utilization is of great significance.Combining coal gangue concrete and FRP material to form composite components can not only improve the ductility,but also effectively improve the problems of low strength of coal gangue concrete,when it is applied to the infrastructure construction of mining areas,local materials can also be well achieved.Based on the above background,this thesis studies the axial compression performance,creep performance and axial compression performance after creep of BFRP-constrained coal gangue concrete columns,in order to provide a reference for its application in engineering practice.The main research and conclusions are as follows:Firstly,the axial compression test of 24 BFRP-constrained coal gangue concrete specimens was carried out,the influencing factors are coal gangue concrete strength and BFRP layers.The research shows that: under the action of peripheral BFRP constraint,its strength and ductility have been improved to a certain extent;the stressstrain relationship curve of the confined specimen shows two forms of strong constraint and weak constraint due to the difference of BFRP constraint strength,strong constraint shows that the second curve rises straight or continues to rise straight after a short decline,while weak constraint shows that the second curve drops and tends to be flat;the greater the BFRP constraint strength on the periphery of the specimen,the more the expansion behavior of the inner core concrete can be suppressed;the current discriminant model for strong and weak constraint of cylindrical members may not be suitable for BFRP-confined coal gangue concrete members;based on the existing stress-strain relationship model of strong and weak constraint types,the modified stress-strain relationship model of BFRP-confined coal gangue concrete members with strong and weak constraint types is obtained.Secondly,the creep test of 24 BFRP-confined coal gangue concrete specimens was carried out,the influencing factors are coal gangue concrete strength,stress ratio and BFRP layers.The experimental study shows that: creep of each group of specimens develops faster in the early stage,gradually slows down and tends to be flat in the later stage,and the creep coefficient of the confined specimen is smaller than that of the plain concrete specimen;the strength of coal gangue concrete has the greatest influence on the creep characteristics among the influencing factors;combining the test results with the existing creep theory,the creep prediction model of coal gangue concrete in this thesis is obtained,and the calculation method of longterm deformation of BFRP-confined coal gangue concrete members is proposed based on the stress-strain relationship model obtained from the axial compression test,the calculation method of long-term deformation provides a reference for engineering practice,and then uses this method to analyze other factors and parameters.Finally,the axial compression test after creep was carried out on 32 BFRPconfined coal gangue concrete specimens,and the influencing factors are coal gangue concrete strength,stress ratio and BFRP layers.The research results show that the ultimate bearing capacity and ultimate deformation of the plain concrete specimens are reduced to different degrees after long-term loading,while the ultimate deformation of the BFRP-confined specimens is reduced to different degrees,but the ultimate bearing capacity is almost not affected.Influence.Then,the influence coefficients of strength and ductility are introduced to quantitatively analyze the influence of long-term load on it,and based on the test results,the calculation expressions of the two considering different influencing factors are obtained.The thesis has a total of 64 figures,21 tables,and 97 references. |
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