Selection of the Type and Geometry of Deck–Arch Steel Bridge Based on Structural Performance and Cost

Abstract

To construct a deck–arch steel bridge over a valley at Manali, Himachal Pradesh, India, five different arch configurations are proposed. The deck span of the arch was fixed (100 m) and the arch span (75, 80, 85, 90, and 95 m) is varied, which in turn changes the angle of inclination and rise of the arch. The five bridge configurations are modeled, analyzed, and designed per provisions of Indian standards using MIDAS Civil. Elastic and inelastic structural behavior (including damage mechanism), quantity of materials, and cost are used to identify the best configuration suited to this region. From the analysis, it was observed that the 75- and 95-m spans have higher material consumption and cost. Additionally, the serviceability criteria per the Indian standard are not satisfied by the 95-m span. Parametric studies were conducted for critical load combinations using the maximum bending moments and shear forces in critical structural elements. Based on the observed results, changing the arch span from 80 to 90 m is recommended. Also, based on the quantity of materials and cost, the 85-m arch span was found economical. Additionally, the deck–arch steel bridge configurations are checked for their adequacy using nonlinear static analysis. All the bridge configurations remain elastic under maximum considered earthquake and have almost the same lateral stiffness and strength in x-directions, declining with an increase in arch span in y-directions. The 75-m span is too stiff and brittle in the y-direction, whereas the 95-m span is too flexible. The 80- and 90-m spans caused sudden failure after arch rib failure in x-directions with 85-m sustaining higher deformations. Thus, the 85-m bridge is considered as the best configuration based on safety and economy.