| The column edges of specially shaped column structure are not prominent,beautiful and applicable in the room,which can obtain better building function and reduce the weight of the structure.Prefabricated building is one of the important directions of the development in China’s construction industry.Taking concrete structure as an example,it can greatly reduce wet operation on site through factory prefabrication.It has the characteristics of energy saving and environmental protection,on-site assembly and high efficiency in construction.The construction of new dwellings is conducive to improving the basic living environment in rural areas,enhancing the quality of farmers’ lives,and has important strategic significance for speeding up the construction of new socialist countryside.Precast concrete frame structures with specially shaped column is conducive to the design of new residential construction standardization,factory production,and construction and assembly development.However,the code of "Technical specification for concrete structures with specially shaped columns"(JGJ149-2017)do not have any related regulations about the seismic design of precast concrete frame structure with specially shaped column,especially for the particularity of specially shaped column section.Based on the development and demonstration construction of a new precast residential buildings,this article studied the seismic performance of precast concrete frame structure with specially shaped column through pseudo static test and numerical analysis.It can provide a reference for the engineering application.The main work and conclusions of this paper are as follows:(1)The reliability of seismic performance of precast concrete frame structure with specially shaped column based on the "equivalent cast-in-place" design is verified,and the quasi-static tests are carried out on two full-scale monolithic and prefabricated concrete frame structures with specially shaped column under vertical load.The results show that the failure mode of both monolithic and precast specimens is beam hinge failure mechanism,which accords with the design principle of "strong column and weak beam".The ultimate bearing capacity of monolithic and precast specimens is similar and both of them show good bearing stability,and the average difference of peak load is 7.3%,and the degradation coefficient of bearing capacity of the two specimens is between 0.89 and 1.00.Compared with the traditional monolithic specimen,the precast specimen performs slightly better stiffness degradation capacity,energy dissipation capacity and ductility,etc.It is feasible and safe to adopt the precast concrete specially shaped column frame structure with the connection of grouting anchorwhich conforms to the current design concept of "equivalent cast-in-place".(2)The influence of axial compression ratio on the seismic performance of precast concrete frame structure with specially shaped column is proved,and the quasi-static tests are carried out on two precast concrete specially shaped column frame structures with axial compression ratios of 0.14 and 0.28.The results show that the joint scheme of "grouting anchor connection + post-casting joint" is safe and reliable.With the increase of axial compression ratio,the corresponding lateral bearing capacity of prefabricated concrete specially shaped column frame structure increases under the same lateral displacement,and the average yield load and peak load increase by about 16.8% and 14.5% respectively.At the same time,the ultimate deformation,energy dissipation capacity and ductility of specimen are reduced,but the average ductility coefficients are above 3.20.The calculated displacement angles between each elastic layer of the two specimens are all less than the limit of 1/550 specified in Technical Specification for Concrete Structures with Specially Shaped Column(JGJ 149-2017),which indicates that precast concrete frame structure with specialy shaped column has premature cracking phenomenon.The reason is that the contribution of floor slab,inner and outer wall slab to lateral stiffness are not considered in the plane frame test of one piece.In terms of the displacement angles between the elastoplastic layers,they all meet the requirement of the 1/50 limit of the code,and meet the seismic fortification requirement of "no collapse under strong earthquake".(3)The seismic performance of the two-story and two-span precast concrete frame structure with specially shaped column is proved,and the quasi-static test is carried out on a full-scale design of the two-story and two-span precast concrete frame structure with specially shaped column.The results indicate that the ultimate failure of the model is characterized by "strong column and weak beam" failure.The elastic interlamellar displacement angles of each layer of the model are less than the requirement of the standard limit of 1/550,which is caused by the premature cracking of the assembled specially shaped column frame structure at the joint of the members.It is suggested to moderately relax the elastic interlamellar displacement angle limit.The displacement angles of the first and second floors are respectively 1/25 and 1/48,both greater than the standard limit of 1/50,which meets the seismic fortification requirements of "no collapse under strong earthquake".The specimen model has good capacity of bearing deformation and energy dissipation and meets the requirements of ductile frame.The middle cross node of the model is an "X" type shear crack with heavy damage,so necessary measures should be taken to strengthen it.(4)The static elastoplastic analysis of precast concrete frame structure with specially shaped column based on the design of "equivalent cast-in-place" is realized,and the pushover analysis of the concrete specially shaped column space frame and one frame of its opening and depth direction in SAP2000 are completed.The results show that the static elastoplastic simulation results on the SAP2000 platform are in good agreement with the experimental results by equipping the specially shaped concrete columns into rectangular columns in situ,which provides a convenient and reliable means for the pushover analysis of similar structures.Expansion analysis shows that for the two-story and two-span prefabricated concrete specially shaped column frame structure,the ultimate load is slightly increased and the ultimate deformation capacity is shortened after considering the influence of axial compression,but the ultimate displacement angles still meet the limit of the code.Furthermore,the pushover analysis is carried out on the background of new residential building engineering,and the results indicate that the failure of spatial frame model presents the failure mode of "beam-column hinged mixed yield mechanism".The displacement angles between floors meet the requirements of the code and the seismic fortifying goal of "no damage under weak earthquake,no collapse under strong earthquake".The innovation of this paper is discussed as follows:(1)The seismic performance and reliability of full-scale precast concrete frame structure with specially shaped column connected by slurry anchor are verified,and the failure mechanism is revealed.(2)A static elastoplastic analysis method for precast concrete frame structure with specially shaped column based on in-situ equivalent substitution and modified section characteristics is established. |
PDF Full Text Request