An Analysis On Quantification Of Robustness Of Reinforced Concrete Frame-shear Wall Structure

Sturcture robustness which is a concept that reflects the ability of structure against the continuity collapsed caused by accidents,is a hotspot in the field of structural engineering.At present,many countries have the requirement of structural robustness in engineering design codes,but these requirements are of the qualitative level.Though there have been many structural robustness indexes,no quantitative measure of structural robustness is generally accepted,which derives from the different usage of robustness by different scholars.Concepts relevant to structural robustness are differentiated and analysed in the present thesis,component importance coefficient(CIC)and component vulnerability coefficient(CVC)are put forward on behalf of the two aspects of structural performance,and structure robustness coefficient(SRC),as a quantitative index of structural robustness,is a combination of CICs and CVCs.For different structures and different material properties,the calculation method of CICs and CVCs is different:for truss structure,when component failures,whether the structural fails or not can be judged by geometric composition analysis,so CICs can be calculated by the incremental load method.On the other hand,all components are two-force bar,therefore each component’s CVC can be ’defined directly;For RC frame-shear wall structure,CICs can be get only by calculating the change of the ultimate load capacity of structure via pushover analysis.On the other hand,because components are in a complex stress state,so the calculate of CVC must consider the interaction of tension,compression,bending moment and shear force.From the above we can see that the calculation method of SRC is only applicable to the frame structure,the robustness of shear-wall structure can not simply calculate as the same way.Therefor,this thesis aims to make the SRC can be applied to the frame-shear wall structure.The analysis and comparison of the model of shear-wall structure show that,compare to all calculation models,the improved frame-brace model which belong to bar element model has the advantages of less unit node,faster calculating speed and accurate calculation result.And by setting the plastic hinge on the bar in the improved frame-brace model,the plastic properties of shear wall can be well simulated.On the other hand,the improved frame-brace model can transform shear-wall structure to frame structure,that makes CVC which is based on frame structure,can be applied to the shear-wall structure.Therefor,this thesis chooses the improved frame-brace model as the calculation model of shear-wall structure.Numerical examples of five RC frame-shear wall structures were performed to demonstrate the use of the proposed robustness index.Distribution of CICs and CVCs among each structure are compared and analysed,and robustness assessment of each structure is made.Analysis results show that the robustness index can reflect well the structure robustness of different structures.In addition,increasing the local resistance and redundancy of the structure are two effective methods to upgrade structural robustness.In conclusion,the calculation results of five examples show that the robustness index can be extended to reinforced concrete frame-shear wall structure.