what is the importance of expansion joints on concrete bridge decks?
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For the construction of Structures, rebars are used to resist tensile stress.
But rebars have ductile property, which allows it to expand and contract as the temperature increases and decreases, respectively. This is due to seasonal changes.
Thus, to resist cracks in concrete structures, expansion joints are provided.
Generally, Steel reinforcement is used for the construction of bridges and bridge decks, where reinforcement is acting as a tensile load carrying material and used to resist the tensile stress. Generally due to thermal stresses expansion may occur in structures which leads to crack if expansion joint is not provided. in this way expansion joint is designed as a safe way to observe the heat-induced expansion and contraction of structures. In traditional systems, the expansion is of rubber-based and nowadays it is highly used in cement concrete road because it can expand when heat increase. Following are the two types of expansion joints used nowadays
The expansion joints allow for easy movement of concrete slab edges when the concrete of the deck expands or contracts. As a result, the expansion joints prevent the he deck slabs from colliding and cracking, tension cracking and bending out of shape.
The expansion can be thermal expansion due to seasonal and weather changes and also, expansion due to traffic load on the slabs. The vehicle axles usually impose asymmetrical moments which cause differential bending at different slab edges. To keep the deck in original shape, expansion joints play an additional role.
Also, generally in concrete pavements, regular shaped cracks or cuts are deliberately introduced just after construction, so that the location of future cracks is fixed since the concrete is far more liable to crack where it’s already cracked. This cracked area is in turn additionally reinforced by the expansion joint steel and the future cracks are by restricted from spreading. This is the reason why the cracks are made at the edges only.
Expansion joints are given in decks to prevent it from cracking as RCC expands and contract due to weather, steel expands when hot and contract when cold, this action develop cracks in the concrete, so to avoid such cracks joints are given
Expansion joint is provided for free to expand of bridge deck for the bridge span
Basically, 20mm to 25mm keep space between one span to another span. This space is allowed to expansion of span.
Expansion of span is due to
Figure of expansion joint is
The importance of expansion joints on concrete bridge deck is that they are designed to allow for continuous traffic between structures while accommodating movement, shrinkage and temperature variations on reinforced and prestressed concrete, composite and steel structures.