Study On Seismic Fragility Analysis Of RC Frame Structures Based On The IDA Method

RC frame structure, as a basic structure system for urban or industrial high-risebuilding, is found broad applications throughout the world. However, during theearthquakes which happened in recent years, RC buildings have suffered more or lessdamages even collapses, bringing severe dangers to people and their properties.Considering that the earthquake mechanism is a process that uncertainty (structure andearthquake) is coupled with non-linear variables, this paper employs IDA method toanalyze the earthquake uncertainties. After a discussion of seismic vulnerability onplane frame construction with13roof trusses, this paper intends to clarify the influenceof4parameters, i.e., axial compression ratio, aspect ratio, concrete strength andlongitudinal reinforcement strength on the seismic resistance levels that RC frameconstruction is possible to reach.First and foremost, the author discusses the kernel problems that are involved inIDA-based seismic fragility analysis. Then,16earthquake records are desired in thispaper with Sa (T1,5%) as the indicator for seismic strength and θmaxas the indicator forstructural damages. When determining the threshold, this paper not only resorts to thesimple and convenient DM rules but also IDA method which is eligible for collapsecritical point judgment, by which a reasonable set of critical points of various levels canbe achieved. Secondly, it analyzes the finite element modeling theory onOpenSEES-based RC plane frame construction and takes the6-floor RC plane frameconstruction as the example to elaborate on IDA-based seismic fragility analysisprocedure. Finally, it conducts IDA-based seismic fragility analysis on plane frameconstruction with13roof trusses.As a result, RC frame constructions which are designed in strict accordance with current specification can all hit the target "no collapses in big earthquake". With theincrease of axial compression ratio, decrease of seismic resistance, variousconstructions are more liable to reach different limits, and combined with axialcompression limits in the domestic and international norms, it is recommended thatChina be appropriate to reduce the axial compression ratio; aspect ratio influence onseismic resistance is ambiguous; on the premise of a similar axial compression ratio,elevation of concrete strength levels is tantamount to that of seismic resistance. With thebeam-column longitudinal reinforcement strength increases, the structure with HRB500steel has a higher possibility to reach IO and LS state than HRB335and HRB400underthe same seismic intensity, however, when close to collapse, the structure with HRB500steel shows better resistance ability than the latter two. The outcome of this researchprovides theoretical reference to evaluate axial compression ratio, aspect ration,concrete strength and the influence of steel strength on construction seismic resistanceon a quantitive basis, as well as a quantitive reference to performance-based design ofRC frame structures.