I'm doing my M.Tech project on Pushover Analysis of a 10 storeyed RCC building resting on a sloped ground using ETABS v.20 software. The structure is found to be safe and all the concrete members have passed the concrete frame design check. Prior to analyzing the pushover analysis, pushover load case has been defined under Load Case as non-linear static type, set to a control displacement of 500mm; next auto hinge property was assigned to frame members (i.e., M3 hinge property for beams and P-M2-M3 hinge property for columns) at a relative distance of 0.1m and 0.9m from a joint. After running the analysis, the following warning message has appeared:
MAXIMUM NUMBER OF NULL STEPS REACHED FOR CASE: PUSH SUBSEQUENT RESULTS WILL NOT BE AVAILABLE
and hence, the total no. of steps for pushover curve appears to be very less and performance point under FEMA 440 Equivalent is not to be found as capacity and demand curves doesn't intersect
Does anyone had faced similar problem and can share the solution for the same??
If the demand curve and the capacity curve do not intersect, it typically indicates that the structure, as currently modeled, would not be able to withstand the represented seismic forces. This can occur due to several reasons:
A) The structure may not have been designed to resist the level of seismic force represented by the demand curve. This might require a review of the structural design, increasing the strength or ductility of the structure, or both.
B) The seismic forces represented by the demand curve may be overestimated. This could be due to overly conservative estimates of seismic hazards or structural response.
C) Pushover analysis is a nonlinear static procedure. If the structure exhibits complex nonlinear or dynamic behavior (like higher modes of vibration) that aren't well-represented by this type of analysis, it might be necessary to use a more sophisticated analysis method, such as nonlinear dynamic analysis.
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