| 3D printed concrete technology has the advantages of intelligence,automation,digitization and low labor investment.At present,it has a certain engineering application.However,the characteristic of 3D printed concrete components is its superposition printing mode,which makes its reinforcement mode and seismic performance different from traditional reinforced concrete components.A feasible structural form of 3D printed concrete structure and its construction methods are as follows: Prefabricating 3D printed concrete wall components first,and then connect the3 D printed concrete wall into an integral structure by using cast-in-situ reinforced concrete columns and beams after on-site installation.This kind of structure is not only different from the infilled frame structure but also from the shear wall structure,which is called 3D printed concrete wall-frame integral structure in this paper.In order to study the seismic performance of this structure,the 3D printed concrete wall-frame integral structure specimens are designed and the low cycle reciprocating load experiment is carried out.It is hoped that the performancebased structural design concept can be applied to its structural design in the future.The main work and achievements of this paper are as follows:(1)Nine 3D printed concrete wall-frame integral structure specimens are designed and manufactured,and their basic form and manufacturing process are introduced in detail.The low cycle reciprocating load experiment is carried out,and the failure mode and law of the specimens are analyzed and summarized according to the experiment phenomenon.In addition,the structural behavior of the specimens is analyzed and studied,including column longitudinal reinforcement strain,hysteretic curve,skeleton curve,displacement ductility,strength degradation,stiffness degradation,energy dissipation capacity and residual deformation.Moreover,the effects of axial compression ratio,the size and reinforcement of frame,the section form and facade printing paths of wall on seismic performance are compared and analyzed.(2)According to the experiment results,the following conclusions are summarized: The seismic performance of 3D printed concrete wall-frame integral structure specimens is different from the traditional infilled frame structure or shear wall structure,and the failure mode of specimens is shear failure.The defect layers between strips of 3D printed concrete wall can induce the development of cracks,but they do not affect the overall development trend of cracks.And strengthening the frame size and reinforcement of the 3D printed wall-frame integral structure can improve its bearing capacity,ultimate displacement angle and repairability.Although the final cumulative energy consumption can be improved,the equivalent viscous damping coefficient under the same displacement angle is smaller and develops more slowly.Among them,the final cumulative energy consumption of the specimen with 3D printed concrete hollow wall is only inferior to that of the solid wall with the same printing paths,but the shear deformation is relatively large.The asymmetry of printing paths will lead to the asymmetry of crack development and stiffness degradation.In terms of action mechanism,oblique 3D printed concrete strips can be regarded as diagonal compression bars and tie bars can be regarded as tension bars.When the axial compression ratio increases from 0 to 0.1,the peak load,ultimate displacement angle and ductility of the specimens can be effectively improved.But if the axial compression ratio continues to increase to 0.2,it will bring adverse effects.(3)In this paper,the 3D printed concrete wall is modeled as a whole and then divided.The3 D printed concrete strip and interlayer defect layer are combined for modeling,and the wall is divided into multiple strips with thickness of 19 mm and inter-strip defect layers with thickness of 1mm,and their strength is reduced to 90% and 75% of the cube compressive strength of the3 D printed concrete test block formed by integral pouring.The numerical simulation results can well reflect the peak load and failure load,but the load in the early stage of loading is higher than the experimental value.Due to the lack of reinforcement synergy in the wall,there is an obvious decline of bearing capacity caused by concrete cracking in the skeleton curve.The mass distribution,less reinforcement and asymmetric initial damage of 3D printed concrete wall lead to the asymmetry of positive and negative bearing capacity.(4)In the finite element simulation analysis of 3D printed concrete components modeling,the PEEQ nephogram can effectively reflect the concrete plastic damage at the bottom of the column and the corner of the wall,which also reveal the causes of cracking of multiple specimens along the junction of the wall and the column.In addition,the simulated stress nephogram of reinforcement conforms to the test results of large stress on the longitudinal reinforcement at the bottom of the column and the tie bars at the side of the column.This modeling method can reflect the inducing effect of 3D printed concrete paths on the damage development of concrete,but the accuracy is not high under low cycle reciprocating load,which still needs further research.(5)Combined with the numerical simulation results and experimental results,this paper puts forward some optimization suggestions for the overall structural design scheme of 3D printed wall-frame integral structure: For example,avoiding the design of printing paths with diagonal lines that have a strong inducing effect on crack development,strengthening the connection of wall and column,carrying out reasonable reinforcement design according to the3 D printing construction methods of the wall to avoid enlarging the asymmetry of the structural damage and save manpower.In addition,this paper proposes to use hollow wall with horizontal printing paths in the design of 3D printed concrete wall-frame integral structure,so as to save materials and obtain relatively good energy consumption capacity under the same displacement angle.However,it is also necessary to enhance the final cumulative energy consumption by reinforcing the 3D printed concrete wall. |
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