ISSN: 2241-7443
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Issue 2: May-Aug. 2014

Issue 2: May-Aug. 2014

Published online on September 2014.

Contents

Footing fixity effect on pier deflection

J. Kent Hsiao , A. Y. Jiang

Abstract: The rotational restraint coefficient at the top of a pier and the rotational restraint coefficient at the bottom of the pier (that is, the degree of fixity in the foundation of the pier) are used to determine the effective length factor of the pier. Moreover, the effective length factor of a pier is used to determine the slenderness ratio of the pier, while the degree of fixity in the foundation of a pier is used to perform the first-order elastic analysis in order to compute the pier deflection. Finally, the slenderness ratio of the pier is used to determine if the effect of slenderness shall be considered in the design of the pier, while the magnitude of the pier deflection resulting from the first-order analysis is used to determine if the second-order force effect (the p-Δ effect) shall be considered in the design of the pier. The computations of the slenderness ratio and the deflection of a pier, however, have conventionally been carried out by assuming that the base of the pier is rigidly fixed to the footing, and the footing in turn, is rigidly fixed to the ground. Other degrees of footing fixity have been neglected by the conventional approach. In this paper, two examples are demonstrated for the slenderness ratio computation and the first-order deflection analysis for bridge piers with various degrees of footing fixity (including footings anchored on rock, footings not anchored on rock, footings on soil, and footings on multiple rows of end-bearing piles) recommended by the AASHTO LRFD Bridge Design Specifications. The results from the examples indicate that the degree of footing fixity should not be neglected since it significantly affects the magnitude of the slenderness ratio and the deflection of the pier.

International Journal of Bridge Engineering, Vol. 2, No. 2, 2014: pp. 1-20

Response of box girder bridge spans - Influence based moving load analysis

G. V. S. Reddy , P. Ch. Kumar

Abstract: Recent developments in the field of Bridge engineering, Box Girder Bridges have heightened the need for improving the ability to carry the live load and undertaken as a result of code provisions. This paper deals with the response of Reinforced concrete and Prestressed concrete bridges when subjected to standard moving vehicular loads. Currently length of the span and width of the carriage way are kept constant for the models and analysis is carried out using MIDAS CIVIL software. Influence based moving load analysis: Influence lines and Influence surfaces are generated to analyze the response of bridge structure subjected to live loading within designated lanes. BM, SF and Displacements are obtained by placing moving tracer at different positions of the designed lanes throughout the span length. This study makes an attempt to develop efficient geometric models for new constructions, and to provide necessary structural configuration against live load bending moments, shear force and displacements. The determination of absolute maximum live shear and bending moment due to moving concentrated loads on the box girders is discussed.

International Journal of Bridge Engineering, Vol. 2, No. 2, 2014: pp. 21-30

Stability of curved-in-plane C-S bridges

I. G. Raftoyiannis, G. T. Michaltsos

Abstract: In this work, the stability of curved-in-plane cable-stayed bridges is thoroughly studied. Expressing the tensile forces of the cables with respect to the deck and pylon deformations, the cable-stayed bridge problem is reduced to the solution of a curved-in-plane beam representing the deck. A three-dimensional formulation is considered for the analysis of the c-s bridge model. The theoretical formulation is based on a continuum approach, which has been widely employed in the literature to analyze long span bridges. Two case studies are carried out in the present work. The first is concerned with the determination of the critical sectorial angle of an unloaded bridge and the second one with the determination of the critical horizontal load related to the sectorial angle of the bridge.

International Journal of Bridge Engineering, Vol. 2, No. 2, 2014: pp. 31-47

Segmental bridge design of prestressed box superstructure for cantilever construction

H. R. Trivedi

Abstract: Bridge “aesthetics” with “economy” is a challenging task for engineers. Superstructure plays a leading role in bridge aesthetics and economy. By using “segmental box type superstructure” aesthetic with economy can be achieved as curtailing of pre-stressing cables became possible. Many times, it is the only option left for “Construction of Bridge in Difficult Climate Region” and “Construction of flyover without disturbing traffic”. Analysis and design of cantilever segmental bridges are more complicated and is always a challenging task. Hence here attempt is made to accommodate procedure for three dimensional analysis and design of the same followed by illustrated example. The objective is to spread knowledge of the design of Pre-stressed Segmental Box type superstructure and to show how to automize the same. Efforts made in this study may enhance understanding of how to make the design process somewhat easy by providing automization with the use of the programming languages and by interlinking the same manually; without having particular bridge software package.

International Journal of Bridge Engineering, Vol. 2, No. 2, 2014: pp. 49-82

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