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PROCEEDINGS OF THE EIGHTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY
Edited by: B.H.V. Topping, G. Montero and R. Montenegro
The Behaviour of Bridges with Jointless Decks Subjected to Time-Dependent Effects
Department of Civil Engineering, University of North Florida, Jacksonville FL, United States of America
A. El-Safty, "The Behaviour of Bridges with Jointless Decks Subjected to Time-Dependent Effects", in B.H.V. Topping, G. Montero, R. Montenegro, (Editors), "Proceedings of the Eighth International Conference on Computational Structures Technology", Civil-Comp Press, Stirlingshire, UK, Paper 140, 2006. doi:10.4203/ccp.83.140
Keywords: jointless, bridge, deck, time-dependent effects, temperature, strength.
The use of jointless bridge decks is useful in both the construction of new bridges and the elimination of joints in existing bridges, as it reduces direct and indirect costs [1,2,3]. This paper presents an analytical study on the behavior of jointless concrete bridge deck systems subjected to instantaneous, temperature and time-dependent effects. Two approaches are used to investigate those effects; one using nonlinear finite element analysis [4,5] and another utilizing a parametric study . Some parameters involved in the study pertaining to the link slab are the link slab stiffness, the dimension, the optimum debonded length, and the amount of reinforcement. Other factors included in the analytical model pertaining to the girders are the relative flexural stiffness of the girder, link slab and types of supports (hinge and roller). Analytical results are compared with experimental and field test results of a reinforced concrete link slab. The mode of deformation is discussed with particular emphasis on the strains and development of crack widths, which is important for durability against steel reinforcement corrosion. The study provides a better understanding of the behavior jointless bridge system and suggests that the use of a debonded link slab can be effective in extending the service life of new or repaired bridge deck systems.
Beams are analyzed successively for girder dead load, deck dead load, prestressing, and live load. The creep effect is included in each of the first three loadings. Results indicate an increase in the load-carrying capacity for the debonded beams than that for the beams without debonds. The highest load carrying capacity is achieved by the beam with a debonded length of 0.05 L.
Deck-continuous beams with or without debonded lengths, are analyzed for their response under time-effects. The beams are left unloaded for a period of one year under the effects of aging, shrinkage and creep of concrete and relaxation of the prestressing steel. Afterwards, the beams are loaded to failure. The long-term strengths compared to the instantaneous strength of the beams. No perceptible difference in strength is found as a result of time effects. However, debonded beams show a higher ultimate load and a more ductile response than the beams without debond.
Beams with and without debond are analyzed for their response under temperature effects. It is seen that camber increases when temperature varies across the depth of the beams. However, under a constant temperature gradient, very slight, rather negligible, changes in deflection are observed.
The boundary conditions and the loading arrangement greatly affect the responses and stiffness of the jointless deck and beam system with partially debonded connections. Increasing the steel reinforcement content in the connection element will enhance the beam response and its ultimate load to approach the response of a continuous beam. Yet, increasing the reinforcement amount in the connection element beyond a certain limit may result in failure of the deck due to crushing of the concrete.
Under creep effects associated with both dead loads and prestressing, an increase in the load carrying capacity is observed for debonded beams in comparison with beams without debond. A more ductile behavior is also noticed for debonded beams. Camber increases when temperature varies across the depth of the beams. However, under a constant temperature gradient, very slight, rather negligible, changes in deflection are observed. Under the effects of aging, shrinkage, and creep of concrete and steel relaxation, no perceptible difference in strength was noted.
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