Research On Mechanical Performance Of Primary-secondary Mega Truss Structures

Primary-secondary structure, consist of primary structure(load-bearing and lateral resisting system),with sub-structure(bear and pass their own load),is a new and high-efficiency kind of structure style that applied widely in super high-rise building. Primary and secondary structure receives much concern in practical engineering structures because of superior building adaptability and high structural efficiency. However, stress state of each component, the route of structure seismic fortification, reasonable parameter of structure about primary and secondary structure was not clear. In this paper, internal force distribution of primary and secondary structural system, failure modes under earthquake, reasonable yield mechanisms of primary-secondary mega truss, as an important structure type of primary-secondary structures, were studied:Static structure features about primary-secondary mage truss structure. Structure internal force distribution, deformation characteristics and collaborative work performance of primary and sub-structure were analyzed and contrasted by models of primary-secondary mage truss structure with modular axial force and continuous axial force, and the results indicated that sub-structure contributed to lateral stiffness of integral structure in some extent. Based on a modular giant truss structure stiffness formula, various structural parameter s’ influence on the lateral stiffness of primary and secondary structures and the work performance of primary and secondary structure was studied. Improving the strength of support within a certain range can significantly improve primarysecondary mega truss structure’s lateral stiffness. By orthogonal test various structural parameters will have different effect on the lateral stiffness, and floors of the structure within the module are most sensitive to lateral stiffness.Study of primary-secondary mega truss structures’ earthquake failure base. Basing on working performance of outer tube of primary-secondary mega truss structure and core tube, a simplified calculation model of the structure were gained, and differential equation of transformation and internal force were calculated. Static elastic-plastic pushover analysis were conducted specified to mega truss tube-core tube, yielding order of each component of mega truss tube-core tube in the process of plastic developing and failure mode of mega outer truss tube were concluded. Basing on analysis and comparison of inner force variation characteristics and failure order, redistribution of inner force of mega truss tube-core tube was explicated. By contrasting stiffness variations of core tube –outer tube and integral structure, reasons of stiffness degradation in each period were obtained. Basing on characteristics and advantages of primary-secondary mega truss structure, static elastic analysis and dynamic elastic-plastic analysis, reasonable yield sequence of structure system when primary-secondary mega truss structure were gained. Yielding sequence of mega truss structure based on primary and secondary structure is coupling beam, support, secondary framed beam, tie beam, secondary column, main framed beam, shear wall and main frame column in sequence. Changing intensity of component may alter yielding sequence, but mega truss structure based on primary and secondary structure –core tube has 3 seismic fortification lines. The first line are coupling beam; the second line are and support, secondary framed beam, tie beam, secondary column; the third line are main framed beam, shear wall and main frame column.Advices for OCT building. Structural style of OCT building is mega truss structure based on primary and secondary structure with c ore tube. Under the action of static loads, outer tube of OCT building demonstrate that secondary differentiation of internal force in both prim ary structure and sub-structure, but the plastic development sequence of mage truss structure based on primary-secondary shows that support is the second line of structure seismic fortification based on the result of static elastic-plastic analysis. Supports would better not to be a main component which carries the vertical load to realize the best performance of anti-seismic, so, supports should have less rigid connection with the surrounding small column.