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Sometimes the side of concrete bridges is observed to turn black in colour. What is the reason for this phenomenon?

In some cases, it may be due to the accumulation of dust and dirt. However, for the majority of such phenomenon, it is due to fungus or algae growth on concrete bridges. After rainfall, the bridge surface absorbs water and retains it for a certain period of time.

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Should raking piles of a bridge abutment be placed under an embankment?

For a bridge abutment to be supported on raking piles with different orientations, the movement between the ground and the pile group is difficult to predict.

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What is shock transmission unit in bridges?

Shock transmission unit is basically a device connecting separate structural units. It is characterized by its ability to transmit short-term impact forces between connecting structures while permitting long-term movements between the structures.

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Why are coatings sometimes provided at the back faces of abutments?

There are different views on the necessity of the application of protective coatings (may be in the form of two coats of paint) to the back faces of bridge abutment. The main purpose of this coating serves to provide waterproofing effect to the back faces of abutments. By reducing the seepage of water through the concrete, the amount of dirty materials accumulating on the surface of concrete would be significantly decreased.

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Why are precast concrete piers seldom used in seismic region?

The use of precast concrete elements enhances faster construction when compared with cast-in-situ method. Moreover, it enhances high quality of piers because of stringent control at fabrication yards. The environmental impact is reduced especially for bridges constructed near waterways. In particular, for emergency repair of bridges owing to bridge collapse by earthquake and vehicular collision, fast construction of damaged bridge is of utmost importance to reduce the economic cost of bridge users.

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