Geometry

Concrete Construction

Concrete Construction Channels The channel is the water conveying structure and hence besides the strength of the structure , ability to retain water with any percolation loss is also of paramount importance. The construction process starts with the preparation of the soil sub layer, above which the plain cement concrete layer of required thickness is to be placed. Based on the on site requirements like soil conditions the floor of the channel could also be made using reinforced cement concrete. Also , in addition to the channel floor, the side slopes of the channel also need to be constructed on the similar lines. The joint if any, shall be carefully handled as the poor joining in the concrete process would result in weak spots which would become the locations of future problems in the channel. In order to ensure the flow of water with very low energy loss it is necessary to maintain the channel geometry in the construction. The machinery choice is also a very important component in the construction process. With a proper attachment for levelling and material lining activities the channel construction could be undertaken on a continuous mode (US patent,, 1984). This would help to maintain the required slope and the roughness condition the important criteria that influences the velocity of flow. The concrete mix design shall be prepared as per the design specification and if the construction need to be carried out in adverse condition addition of admixtures is necessary to facilitate the retention of properties of prepared concrete . Finally, proper curing of the concrete works is also required to have the better durability of the construction process.
Footbridge
The foot bridge construction requires more care as it is indented to carry moving loads with supports given only at the locations as specified in the design document. The major components of the foot bridge , constructed over the diversion channel , are support piers at the ends and the bridge slab. The ends piers are the structures that transfer the load from the bridge to a hard ground capable of supporting the entire structure. The foundation of piers is constructed in plain cement concrete and the pier wall in rubble masonry. The slab of the bridge is to be constructed in reinforced cement concrete. The prior to the concreting of the slabs proper formwork need to be in place as the design specification given by the structural engineer. After the completion of the formwork , the next task is to place the reinforcement. This size of the bars, the spacing between them and providing the proper placement are the important factors to be considered in the reinforcement placing operation. Following this is the concreting . The concrete mix preparation need to be prepared as per the specification and shall start the process from one end of the bridge. The concrete being placed on the reinforcement need to be vibrated to achieve the maximum density without giving any chance for the formation of pores. And, the concrete prepared shall also confirm to the quality specified in terms of w/c ratio, workability etc. The machinery used would be the concrete mixings plants and conveyers that are a necessary concrete to the concreting location on the bridge. Curing is the next important operation that need to be undertaken after the concreting work. After the specified period of curing , the form work shall be removed and finishing works shall be carried out to make the bridge fit to use.
References
Neville, A.M. (1996), Properties of concrete, 4th Edition, John Wiley &amp. Sons,
US Patent (1984), Patent No 4472089 , Channel construction machinery having a levelling and material lining application attachment , [Online] Available at &lt. http://www.freepatentsonline.com/4472089.html &gt. [Accessed on 14 May 2009].

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