Effect of Skew Angle on Bridge Superstructures

In this paper, the effect of skew angle on reinforced concrete skew bridge decks is presented by using the grillage analogy. The actual deck system of the bridge is represented by an equivalent grillage of longitudinal and transverse beams. A span 26m of simply supported bridge deck is taken as the case study to obtain the values of the bending moment' s distribution versus span length for the one type of skewness and the results are compared against the moments of the right deck span of the bridge. The analysis results were based (BS5400) dead and live loads using Structural Analysis program (SAP2000). The analysis provided useful information about the variation of moments and shear forces with respect to change in skewness. It is concluded that in skew bridge deck, the bending moment is decreased, but torsional moments and shear forces are increased by increasing the skew angle. It is noticed that the maximum bending moment at skew angle 55o, by 76% in comparison with zero skew angle. On the other hand the maximum torsional moment increases for the same skew angle (55o) more than five times than with zero skew angles.

Seismic Study of Skew Bridge Supported on Laminated-Rubber Bearings

Skew bridges consisting of simply supported girders, continuous decks, and laminated-rubber bearings are widely used in western China; however, they are highly vulnerable to strong earthquakes. To investigate the seismic performance of skew bridges considering the sliding behavior of laminated-rubber bearings, the Duxiufeng Bridge located in Sichuan, China, was used as a prototype bridge. This bridge is a skew bridge that suffered seismic damage during the 2008 Wenchuan earthquake. The possible seismic response of this skew bridge under the Wenchuan earthquake was simulated, and the postearthquake repair methods were analyzed considering the effects of bearing types and cable restrainers. Parametric studies, using the finite element method, were also performed to investigate the effects of the skew angle and friction coefficient of the bearings on the seismic response of the skew bridge. The results indicate that pin-free bearings could effectively control the seismic displacement of the bridge, and the cable restrainers with an appropriate stiffness could significantly reduce the longitudinal residual displacements. The effect of skew angles is less significant on skew bridges with laminated-rubber bearings than on rigid-frame skew bridges because of the sliding between the girders and bearings. The residual displacements of the bearings were more sensitive to the variation in the friction coefficient between the laminated-rubber bearings and the girders compared to the maximum seismic displacements.

ANALISIS DINAMIK RIWAYAT WAKTU NONLINIER SKEW BRIDGE

<p><em>Skew bridge</em> adalah jembatan yang memiliki sudut miring yang terbentuk antara garis tengah jembatan dan garis tengah penumpu abutment atau pier. Potensi munculnya gempa bumi yang besar di Indonesia menyebabkan <em>skew bridge</em> juga harus memiliki ketahanan yang baik terhadap gempa.<em> </em>Saat terjadi gempa besar, sebagian material struktur telah mengalami plastifikasi yang menyebabkan struktur berperilaku nonlinier, dengan begitu analisis dinamik nonlinier dilakukan pada penelitian ini. <em>Skew bridge</em> yang digunakan pada penelitian ini mengacu pada 2 bentang utama jembatan jalan tol Solo Kertosono sta 108+666 di kota Madiun. Pada penelitian ini 3 rekaman gempa digunakan dalam analisis, dengan keseluruhan rekaman gempa disesuaikan dengan spektrum gempa daerah jembatan. Analisis nonlinier dilakukan dengan menganalisis nilai kekakuan dan kondisi struktur pilar jembatan pada setiap siklus pembebanan berdasarkan hasil kurva respon histeretik. Hasil analisis respon struktur menunjukkan semua rekaman gempa menghasilkan nilai <em>drift ratio</em> kurang dari 0,5%. Hasil analisis nonlinier menunjukkan terjadinya nonlinieritas semua rekaman gempa pada siklus ke-2 dan penyebabnya adalah <em>cracking </em>pada beton.</p>