Theoretical And Experimental Research On The Seismic Redundancy Design Of Reinforced Concrete Frame Structure Building

Redundancy theory has been extensively studied and applied in many disciplines.In 2001,the 9.11 incident made people realize the importance of redundancy for resisting progressive collapse of building structures.After that,America and Japan began to study the application of redundancy in civil engineering.Based on the theory of redundancy,taking reinforced concrete frame buildings as research object,application of redundancy in practical engineering seismic design is studied and the design method of multilevel seismic system for reinforced concrete frame buildings is put forward in this paper by the methods of theoretical analysis,numerical simulation and experimental research.The main research work and results are as follows:(1)Based on the theory of building seismic redundancy and the present situation of seismic fortification in China,the ideas and control strategies for seismic redundancy design of reinforced concrete frame structure buildings are constructed from two aspects: redundant layout of building structures and redundant design of component sections.1)For the layout of building structure,a hierarchical aseismic system building concept is proposed.Non structural components(such as enclosure walls,infilled walls etc.)are used as architectural fortification line and expected to be damaged before the structural members,so that can dissipate seismic energy as much as possible to reduce damage or destruction of the structure.As for structural members,they can be divided into anti lateral force members and ordinary load-bearing members according to their importance(relative stiffness and load bearing),and different design countermeasures are used to ensure the structural system progressive failure under the action of strong earthquake.2)For the component design,different design countermeasures are taken according to the different members in the seismic system of buildings,that is in accordance with the sequence of "architectural fortification line-structural anti lateral force system-ordinary load-bearing members" and according to the principle of mutual matching between stiffness,strength and ductility,the control principle of sectional design for each level members is put forward,and a seismic redundancy design method for reinforced concrete frame structure house with perfect engineering operability is given.(2)According to the research results,a reinforced concrete frame teaching building collapsed in the 5.12 Wenchuan earthquake is selected as the seismic redundancy design object.Keep building function unchanged but use 100 mm reinforced concrete walls as architectural fortification line,replacing masonry filled walls.For structural members,frames bearing smaller are lateral force resisting members,which are expected to bear all the earthquake;the remaining columns and related components which bear heavy burden are ordinary load-bearing members.The ordinary load-bearing members’ lateral strength is not included in the overall seismic capacity but has the ability to adapt to the requirements of the lateral force resisting members limit deformation,that is when the anti lateral force members are in the limit deformation condition,the ordinary bearing members still have enough bearing capacity.The comparison with original design shows that the overall stiffness is increased and more uniform,the natural vibration period decreases slightly,the dynamic characteristics of the two spindle directions are similar,and the torsional effect is reduced obviously after the redundancy design.(3)The results of redundancy design are analyzed by MSC.Marc for elastoplastic simulation.The analysis shows that reinforced concrete walls damage first but have better ductility under earthquake,it can achieve the desired goal that walls not fall after damaged and protect the structure.Under strong earthquake,the lateral force resisting system has obvious damage but still has sufficient bearing capacity,achieved the design goal.When the earthquake intensity increase,the stiffness degradation of the architectural fortification line and anti lateral force system is intensified,then the ordinary load-bearing members are destroyed,finally the structure is invalid.The results show that buildings designed by this method have reasonable layout and ability of resisting earthquakes at multiple levels.(4)In order to further verify the effectiveness and reliability of seismic redundancy design,a shaking table test of reinforced concrete frame building with infilled walls is carried out with ratio of 1:5.Elcentro wave,Taft wave and an artificial wave are selected as input excitation,the peak of mesa acceleration starts from 0.05 g,increases until the structure failures.In the test,the infilled walls with good ductility and low strength destroyed first but not quit immediately so that could consume the seismic energy and protect the frame structure.The test results show that the failure modes and order of building structural members are reasonable,and the level of degradation of overall mechanical properties of the building is clear,which achieves the desired purpose of redundancy design.The seismic redundancy design method presented in this paper is reasonable and effective.