Study On Elastic-Plastic Response Spectra Of SDOF And Application In Bridge Engineering

The response spectrum of design is an important method for seismic design of structures, the response spectrum method is simple in calculation, and the advantages of the response spectrum design are the standard spectrum is computed only once and strong applicability. However, the current guidelines for seismic design commonly used the elastic response spectrum theory, and reducd through the seismic force modification coefficient, thus calculation of the elastoplastic response of the structure. This process doesn’t take into account the seismic force modification factor is influenced by the seismic wave spectrum characteristics and the characteristics period, that would rise the possibility of the results’ error up.This paper use the response spectrum calculation software Bispec, the dynamic elastic-plastic analysis of SODF system of ideal elastic-plastic model, bilinear elastic-plastic model with the hardening coefficient 0.1 and clough bilinear stiffness degrading model was conducted, with the effections of ductility, stiffness, damping, stiffness, second order and site. The Rμ-spectra were constructed based on the transverse coordinate standardization with characteristic period, and the ductility change range 2 to 8, through these Rμ-spectra some regularities could be find out which have relation to ductility, stiffness, damping, stiffness, second order. The results show that:(1)Under A, B two types of sites, the Rμ-spectra appear peak value in characteristics period, with the different site, the Rμ-spectra have some difference. where the T/Tg=2 could as a critical point, after that, the spectra is being a straight line, and with the increase of ductility, the value of spectra increases. All different ductilities have the same regularity.(2) The Rμ-spectra were reduced with the increase of damping ratio, specially to the peak. The peaks were gradually dissipated when the damping ratio getting to 0.15. The Rμ-spectra had the same direction by effect of the damping under the condition of different ductility, in the same ductility conditions, the Rμ-spectra were affected by the damping reduced, that indicating there was a certain range of damping effect.(3) In the same ductility conditions, the Rμ-spectra were incresed with the increase of post-yield stiffness, finally, the Rμ-spectra tended to a stable level.(4)In the same ductility conditions, the Rμ-spectra were reduced with the increase of P-Δ effect, and the trend of reduction also was in increase, that said high P-Δ was not conducive to the stability of the structure. When the ? ?0.08, the influence degree of the different ductility spectrum of P-Δ effect is not great, while ? ?0.08, the difference reflected, In the same value of ? conditions, the effect of Rμ-spectra finally in a constant level.(5) For single column structure elastoplastic response, through the mode of Vindic, the model of this paper and time history analysis, using the Chopra improved capacity spectrum method obtained more accurate results, reflect the Chopra improved capacity spectrum method is a feasible method for the calculation of bridge structure elastic-plastic response, also demonstrates this line the model of this paper it is also feasible.