Prefabrication provides many benefits over conventional building for bridges. they've got resulted from the economic strategy and beneficial operating surroundings, shielded from hostile climatic conditions. for a few years, the occupation has been conversant in the rules and techniques aiming at studying the standard of the precast items. every one plant has a strength of mind procedure, defining the operating systems and modules for inner inspection and keep watch over. one of the merits, the subsequent are of specific curiosity to bridge construction:
Quality and regularity of the concrete strength.
Elements with elaborated shapes designed to get a greatest enjoy the fabrics and the prefabrication. They require using really complicated moulds, yet even as allow prime quality surfaces with admire to form, texture, dimensional tolerances, etc., to be achieved.
Absence of arduous and hindering scaffolding.
Shorter building time because precast parts are made on the plant self sufficient from the principles and different preparatory works on site.
Precast bridges aren't with no criticism:
The perceived opinion from a few cases, that precast bridges are monotonous and ugly.
The greater variety of transversal joints in older realisations, in particular in viaducts, inflicting pain and upkeep problems.
Certain particular technical concerns, equivalent to previous doubts in regards to the move size of prestressing strands, fairly for big diameters subjected to fatigue stresses in railroad bridges. one other query involved the effectiveness of the shear move on the interface among cast-in-situ concrete and prefabricated components, specifically on the subject of fatigue stresses.
The objective of this cutting-edge document is to offer an in depth evaluation of the present options and functions world-wide and up to date advancements within the area of precast bridges. they need to permit the experts and architects to shape a practical opinion in regards to the probabilities and benefits of this system, and escape from a few nonetheless current prejudices.
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Extra info for FIB 29: Precast concrete bridges
Sample text
1 shows a solution with orthogonal beam-ends and an enlarged transversal diaphragm beam. However, it is also possible to produce the beams with skew endings. Embankment wall Diaphragm beam Threaded couplers Supporting pad Bridge beam Void Supporting pad Bridge beam Moulding Fig. 2 Banking There are two solutions to realise the transversal inclination: - The top surface of the crosshead is parallel to the inclination and the supports are identical. The crosshead is horizontal and the supporting embossments have a variable height.
Structural systems Several types of integral and semi-integral abutments can be used. K. – maximum overall length = 60m, maximum skew = 30°). In the USA, integral bridges have been designed and constructed successfully with overall lengths in excess of 200m. Fig. 16: Types of integral abutments fib Bulletin 29: Precast concrete bridges 39 6 Aesthetics The aesthetic appearance of a bridge is an essential factor, which has to be taken into account from the beginning of a project. As for construction works in general, the general silhouette of a bridge is conditioned by its overall aspect, in other words, by the first image perceived by an observer situated at a distance.
4: Partial continuity - detail type 1: variant solution In the second solution, the bridge decks are designed and constructed in the conventional manner for simply supported multi-span bridges, with slab trimmer diaphragms at the beamends. As with type 1, the beam-ends are supported on two parallel rows of bearings on the piers. Longitudinal reinforcement bars are incorporated at the slab mid-depth to tie the slabs together over the pier, eliminating expansion movement at deck level and permitting the use of an incorporated deck rotation joint.