Cite as: A. Camara, E. Efthymiou (2016). Deck-tower interaction in the transverse seismic response of cable-stayed bridges and optimum configurations. Engineering Structures, 124:494-506.
Motivated from the quadratic dependence of peak structural displacements to the pulse period, Tp$T_p$, of pulse‐like ground motions, this paper revisits the pulse‐period – moment‐magnitude (Tp$T_p$–Mnormalw$M_{\text{w}}$) relations of ground motions generated from recorded near‐source ground motions with epicentral distances, D≤$D\le$ 20 km. A total of 1260 ground motions are interrogated with wavelet analysis to identify energetic acceleration pulses (not velocity pulses) and extract their optimal period, Tp$T_p$, amplitude, ap$a_p$, phase, ϕ$\phi$ and number of half‐cycles, γ$\gamma$. The interrogation of acceleration records with wavelet analysis is capable of extracting shorter‐duration distinguishable pulses with engineering significance, which override the longer near‐source pulses and they are not necessarily of random character. Our wavelet analysis identified 109 pulse‐like records from normal faults, 188 pulse‐like records from reverse faults and 125 pulse‐like records from strike‐slip faults, all with epicentral distances D≤$D\le$ 20 km. Regression analysis on the extracted data concluded that the same Tp$T_p$–Mnormalw$M_{\text{w}}$ relation can be used for pulse‐like ground motions generated either from strike‐slip faults or from dip‐slip normal faults; whereas, a different Tp$T_p$–Mnormalw$M_{\text{w}}$ relation is proposed for dip‐slip reverse faults. The study concludes that for the same moment magnitude, Mnormalw$M_{\text{w}}$, the pulse periods of ground motions generated from strike‐slip faults are on average larger than these from reverse faults — a result that is in agreement with findings from past investigations. Most importantly, our wavelet analysis on acceleration records produces Tp$T_p$–Mnormalw$M_{\text{w}}$ relations with a slope that is lower than the slopes of the Tp$T_p$–Mnormalw$M_{\text{w}}$ relations presented by past investigators after merely fitting velocity pulses. As a result, our proposed Tp$T_p$–Mnormalw$M_{\text{w}}$ relations yield lower Tp$T_p$ values for larger‐magnitude earthquakes (say Mw>$M_{\text{w}}>$ 6), allowing for the estimation of dependable peak structural displacements that scale invariably with apTp2${a}_{p}{T}_{p}^{2}$.
Abstract. The spatial variability of the ground motion can be a key factor to the design of cable-stayed bridges to resist seismic actions due to the critical effect of the asynchronous movement that it introduces between the towers. Cable-stayed bridges are landmark structures consisting key parts of transportation networks and their integrity must be ensured even under extreme seismic events. This work examines the effect that spatially variable ground motions have on the towers of a cable-stayed bridge with 200 m main span. Two different orientations of the structure are examined in an attempt to shed light into the orientation-dependent seismic response of the towers. Additionally, three different propagation velocities of the seismic waves are adopted and the results are compared to those obtained under synchronous ground motions.
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