Research On Eccentric Compression Performance Of Assembled Integral Internal Steel Tube-layered Concrete Composite Component

In order to solve the difficulties in construction of SRC structures and the cumbersome node connections,and promote the development of precast steel reinforced concrete structures,a new type of partially precast SRC column——PSCCST column was proposed in this thesis.PSCCST column includes precast part with reinforcement cage,square steel tube and post-cast concrete part.The precast part with reinforcement cage and hollow hole can be completed in factory and then transported to the construction site.Subsequently,square steel tube will pass through the vertical hole and then the concrete will be poured to fill the gap between steel tube and inner wall of precast part to complete the connection of the upper and lower columns.The precast part with hollow hole can be applied as the formwork for casting post-cast concrete on site,which can reduce the labor and workload markedly.Therefore,PSCCST columns have advantages such as high bearing capacity,simple on-site construction,and good component connection performance,and have broad application prospects.As the existing literature on the bearing capacity of SRC columns under eccentric load cannot be directly applied to PSCCST columns due to the differences in section form and steel type,it is crucial to conduct research on the eccentric compression performance of PSCCST columns.Firstly,one of the application scenarios of PSCCST columns named Fault tolerant Prefabricated Concrete Structure(FTPC structure)was introduced.A systematic study was conducted on the eccentric compression performance of PSCCST columns through a combination of tests,theoretical analysis,and finite element simulations.Furthermore,a prediction model for the eccentric compression bearing capacity of PSCCST columns was established using GA-BP neural network.The main contents and conclusions are as follows:(1)One of the typical application scenarios of PSCCST columns named Fault tolerant Prefabricated Concrete Structure(FTPC structure)was introduced about the basic composition,component connection methods,and design methods of FTPC.Then,a trial design of FTPC structure was carried out using a two-story structure as an example,and the internal force,lateral displacement,and deflection was analyzed.(2)Six PSCCST column specimens were tested to investigate the behavior under eccentric load,and the failure process and final failure morphology of each specimen were described in detail.The failure state,ultimate bearing capacities,load-strain relationship as well as the load-deflection curves were emphatically investigated.The failure modes of PSCCST column under eccentric compression based on test and theoretical analysis.The results indicated that there were three main failure modes,which were named compression failure mode,total yield failure mode,and tensile failure mode.The eccentric compression bearing capacity of PSCCST column was found to decrease obviously with the increase of eccentricity.The strain of cross-sectional basically conformed to the plane section assumption during loading process,indicating that there was no significant relative slip between each part of PSCCST column.The deformation capacity denoted by the horizontal lateral deflection corresponding to N_uincreased with the increase of e.(3)A detailed discussion was conducted on the characteristics of calculation methods for eccentric compression bearing capacity of SRC column in domestic and foreign standards,and the calculation methods for eccentric compression bearing capacity based on the limit equilibrium principle was proposed.The proposed calculation methods for determining the bearing capacity of PSCCST columns under eccentric load were proven to be reasonable and effective through comparison with test results.(4)Six specimen columns were modeled using the finite element software ABAQUS.The rationality of the PSCCST column model was verified by comparing the simulated failure modes and load lateral deflection curves with the experimental results.(5)Based on the established finite element model,an N-M curve was established and a comprehensive analysis was conducted on the influencing factors of eccentric compression bearing capacity.The analysis revealed that the eccentricity had a significant impact on the bearing capacity of PSCCST columns,causing a notable decrease in bearing capacity as eccentricity increases.Increasing the strength grade of both precast and post-cast concrete can enhance the bearing capacity,with the strength grade of precast concrete having a more prominent effect.In addition,increasing the steel content can also improve bearing capacity,especially for columns with larger eccentricity.However,the strength of the steel tube has a relatively minor effect on bearing capacity.(6)The application of the grey correlation theory enabled the determination of correlation between eccentric compression bearing capacity of PSCCST columns and various influencing factors.The results suggest that the eccentricity has the most significant effect on the bearing capacity,followed by the strength grade of precast concrete,the strength grade of post-cast concrete,and finally the steel ratio and steel tube strength.(7)A prediction model for the bearing capacity of PSCCST columns was developed using GA-BP neural network.Through comparison with actual values,the model demonstrated high prediction accuracy.