Basically, piers constructed monolithically with the bridge deck are advantageous in the following ways:
(i) Movement of the bridge deck is achieved by the bending deformation of long and slender piers. In this way, it saves the construction cost of bearings by using
monolithic construction between bridge deck and piers. Moreover, it is not
necessary to spend extra effort to design for drainage details and access for bearing replacement. On the other hand, in maintenance aspect substantial cost and time savings could be obtained by using monolithic construction instead of using bearings as bridge articulation.
(ii) Monolithic construction possesses the shortest effective Euler buckling length for piers because they are fixed supports at the interface between bridge deck and piers.
Basically, piers constructed monolithically with the bridge deck are advantageous in the following ways:
(i) Movement of the bridge deck is achieved by the bending deformation of long and slender piers. In this way, it saves the construction cost of bearings by using
monolithic construction between bridge deck and piers. Moreover, it is not
necessary to spend extra effort to design for drainage details and access for bearing replacement. On the other hand, in maintenance aspect substantial cost and time savings could be obtained by using monolithic construction instead of using bearings as bridge articulation.
(ii) Monolithic construction possesses the shortest effective Euler buckling length for piers because they are fixed supports at the interface between bridge deck and piers.
Don't forget. With monolithic pier/superstructure construction, seismic loading places more demand on the superstructure compared to girder and bearing systems. So, there are always trade-offs. But each type of construction can work, even in high seismic areas.
I agree with Dr Amjad answer. There are some other factors that may be added:
In two span integral bridges, temperature, creep and shrinkage, and other loads that contributes to longitudinal forces like seismic forces are major design challenges. These forces induces additional moments on the central pier increasing the demand. This necessitates innovative solutions in the design, like adoption arch systems which allows the bridge to breath up and down due to thermal actions. Uncertain soil conditions and seismic zones add up the design challenges. Integral Bridge design is an expert area in the design of bridges.
Note: Monolithic construction means that piers are connected to bridge decks without any joints and bearings.
Another advantage of monolithic pier and deck:
Robustness of construction. Bearings are by far the most fragile elements of a bridge. In one case a small exploding device placed near the bearing on top of pier cap has seriously damaged part of the bridge . Took more than a year to reinstate.
Temperature shrinkage creep strains in the deck which adversely affect the pier design can be reduced significantly by adopting leaf piers. Make two piers instead of one at the same location, each pier having only half the area. The effective stiffness of the system will be reduced to 1/4 th, thereby reducing restraints to strains in the deck.
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