| The steel-concrete structures with advanced seismic behavior have been widely used to deal with the frequent occurrence of earthquake disasters recently. However, its complicated structure form and strict design requirements are also criticized. While concrete material is in service, its performance poses time-dependent characteristics to some extent, which often leads to changes in seismic performance, making the structural design exits a deviation somehow. Such deviation could not be ignored especially in the structure with a higher precision for complex high steel and concrete structures.The change of seismic properties may lead to the internal structure destruction, as one of the consequences is that the structure suffered structural damage during the earthquake, therefore, the change of structure’s damage could be used to quantitative the variation of seismic performances. When we can change the material properties of the structure to simulate the structure of the service status of each service during the period under structural response obtained under the service of the structure when the earthquake hit by elastoplastic analysis, using reasonable methods to establish with damage assessment structural design standards corresponding to the damage model, and studying the service period of structural damage with varying characteristics and corresponding design requirements contrast.Therefore, it is important to estimate the service period of structural change in the seismic performance accurately and explore the effect of time-dependent on structural seismic performance of complex high steel-concrete structures. These have great significance for seismic performance evaluation of structures and earthquake preparedness and disaster reduction.Time-dependent characteristics are simulated by changing the material parameters for the complex high steel-concrete structure.The ’quasi variable’ is put forward to comebine the time-dependent characteristics of the materials and elastoplastictime history analysis based on the impact of time-dependent characteristics of structure stiffness and damping and used to build a new elastolastic time history analysis method which in view of the time-dependent characteristics of materials.The global damage time-dependentmodeland weighted damagetime-dependentmodelare built based on structure dynamic response. Rasonable structural damage evaluation criteriaare selected to research the time-dependent characteristics of structure.The evaluation criteria are selected in accordance with the laws of structural damage in the earthquake. Then multistage global damage time-dependentmodel is established according to the requirements of code for seismic design of buildings. The damage time-dependent models of members are present according to their damage characteristics under seismic action and based on the correspondence between the performance standards and the dynamic response of member. Thereafter, the weighted damage time-dependentmodel is established. At last, this contrapositive model could be used to research the time-dependent characteristics of complex high steel-concrete structure.A tipical complex high steel-concrete structure example is analyzed to researched time-dependent characteristics of structural damage. Material constitutive model of fiber beam element of reinforced concrete member and steel reinforced concrete structures is defined by elastic-plastic fiber element model. Time-histories of seismic wave is imported in control of loads and boundary conditions. Structural response during the service period is achieved using the dynamic elastic-plastic time history analysis method considering material time-dependent characteristics. Time- dependent characteristic of complex high steel and concrete structure is presented quantitatively combined with the structure damage time-dependent model. Then the following conclusions are presented. The first conclusion is that this structure has a significant time-dependent characteristics during service period. The phenomenon always occurs is that structural damage beyond the performance requirementunder frequently and rare occurred earthquake due to the time-dependentcharacteristics. In addition, the time-dependent damage presents some volatility because of the collective effect between seismic capacity and conductivity which changing with structural stiffness. Further, Seismic capacity plays a major rolein this phenomenon, but the impact of seismic conductivity is growing wih the improvement of earthquake intensity. Finally, the proposals to adjust the structural seismic design are put forword in view of the conclusions above. |
