5. Pushover

5.1 Scia Engineer

ECtools uses the analysis model of Scia Engineer and the proposrtioning (reinforcement) results from ECtools to prepare a nonlinear analysis model for the execution of pushover analysis based on ATC 41-13 and FEMA 356.

The nonlinear analysis is performed using a dedicated Seismostruct engine which is included in the nonlinear version of ECtools.

More information on seismostruct is available here while the verification is here

The nonlinear model is prepared using 1d nonlinear finite elements and rigid links to create the cores.

The material properties are:

  • Steel with uniaxial bilinear stress-­‐strain model with kinematic strain hardening, whereby the elastic range remains constant throughout the various loading stages, and the kinematic hardening rule for the yield surface is assumed as a linear function of the increment of plastic strain.

       seismo-steel

  • Concrete Uniaxial nonlinear constant confinement model, initially programmed by Madas [1993], that follows the constitutive relationship proposed by Mander et al. [1988] and the cylic rules proposed by Martinez-­‐Rueda and Elnashai [1997].

       seismo-concl

The analysis is based on a fibber element apporach whereas:

  • each element is divided into sections

    seismo-sections

  • each section is divided into fibbers (subsections)

     seismo-fibber

  • each fibre is associated with a uniaxial stress-strain relationship

The sectional stress-strain state of beam-column elements is then obtained through the integration of the nonlinear uniaxial stress-strain response of the individual fibres