Issue 1: Jan.-Apr. 2016

Sabaa Shoaib, liaqat. A. Qureshi, Muhammad Fahad

Abstract:The most dynamic of all the loads for a bridge structure are the live loads that play a vital role in determination of strength of the structure. Bridge is a structure that has to bear the combined effect of all the axle loads traversing it and therefore it is very necessary for the structure to be carefully designed for the heavy live loads, it is expected to be traversed in its life time. Bridge unlike pavements (designed to withstand millions of application of such axle loads) may not withstand even a single such heavier load for which it is not designed. Overloading of vehicles on state highway has been monitored and properly analyzed in this research study. The effects of vehicular live load models as dictated by “West Pakistan Code of Practice for Highway Bridges (WPCPHB)”and “American Association of State Highway and Transportation Officials (AASHTO)” have been compared with the traffic data collected and statistically analyzed from weigh-in-motion (WIM) station. The WIM station located at N-5, the largest and the most overly crowded highway of Pakistan is selected. This research has been conducted to propose the methodologies and protocols necessary for addressing the current traffic characteristics of Pakistan. Calibration factors have been proposed with both WPCPHB and AASHTO live load models to be used for the designing of highway bridges in Pakistan.

International Journal of Bridge Engineering, Vol. 4, No. 1, 2016: pp. 1-16

Theodore G. Konstantakopoulos

Abstract:Bridges on floats are usually temporary structural systems carrying moving loads while consisting from at least two or more floating piers (pontoons). In this work, an analytical model suitable for the dynamic analysis of bridges on floats is presented. When a moving load is passing the bridge with constant velocity both the beams as well as the piers become in motion. The theoretical formulation is based on a continuum approach employing the modal superposition technique. Various cases of geometrical and loading parameters are studied and the analytical results obtained in this work are tabulated in the form of dynamic response diagrams.

International Journal of Bridge Engineering, Vol. 4, No. 1, 2016: pp. 17-25

J. Kent Hsiao, Alexander Y. Jiang

Abstract:Continuous-span, cast-in-place box girders have been popular in modern bridge construction. Secondary moments due to prestressing in continuous-span, post-tensioned girders, however, have significantly complicated the structural analysis and design of the girders. The equivalent load method is a commonly used method in the analysis of continuous-span, post-tensioned concrete girders since the method reduces the analysis of a prestressed structure to that of a nonprestressed structure in which the consideration of secondary moments is not required. The basic concept of the equivalent load method is that the effects of prestressing are replaced by equivalent loads produced by the prestressed tendon along the span of the structure. The approximate equivalent load method significantly simplifies the procedure for the computation of equivalent loads for post-tensioned concrete girders with parabolic tendons and therefore has commonly been used by structural engineers. In this paper, three examples of simply-supported, post-tensioned concrete girders with various combinations of locations of the centroid of tendons (c.g.s.) and the centroid of concrete (c.g.c.) are demonstrated to verify the accuracy of the approximate equivalent load method. Finally, an example of the analysis of a bridge composed of a continuous-span, post-tensioned concrete box girder superstructure and a concrete pier is also demonstrated using the approximate equivalent load method. Inconstant cross sections (inconstant c.g.c, lines) near the pier of the bridge are considered in this example.

International Journal of Bridge Engineering, Vol. 4, No. 1, 2016: pp. 27-55

Panos Tsopelas, Spyridoula M. Papathanasiou, Alper Ucak, Evgenia Prapa

Abstract:The impact of the Soil-Structure Interaction (SSI) on seismic isolated bridges is investigated. Two stick models for the two seismic isolated bridges of interest are considered and equivalent models of the frequency-dependent impedance functions of the soil and foundation are introduced, with the new elements known as "gyromasses" being involved. Their importance is discussed.

International Journal of Bridge Engineering, Vol. 4, No. 1, 2016: pp. 57-64