Precast Concrete Structures
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Precast Concrete Structures introduces the subject in detail, looking at the design process, manufacture and construction using precast concrete for multi-storey buildings. Detailed structural analysis of the material and its use is provided. The theory is supported by practical case studies, worked examples and explanatory illustrations throughout.
Endorsed by the British Precast Concrete Federation and written by an acknowledged authority, this is the first book to explain and educate the student in the uses and advantages of precast concrete.
both floors and beams continuous, for as shown in Figure 4.8b the tops of the beams may be provided with interface shear loops to make a composite beam. Lightweight infill blocks (e.g. dense polystyrene) are sometimes placed on to the tops of the planks to reduce weight by about 25 per cent, but the weight saving Reinforced (rc) precast plank In situ topping screed shown thus 75 to 100 mm Up to 2400 mm Prestressed (psc) precast plank (a) rc or psc precast unit. Min. width 300 mm Figure
raise the position of the circular voids by this distance by making the top cover to the cores 28:0 À 15:7 12:3 mm. It would therefore be necessary to change the shape of the voids to non-circular ± this may not be welcomed by the manufacturer. 4.3.3 Ultimate limit state of flexure In calculating the ultimate resistance, material partial safety factors should be applied as per usual, viz. 1.05 for steel and 1.5 for concrete in flexure. The ultimate flexural resistance Mur when using bonded
the two stage design they both achieve the full 0.95 fy . 100 4.4.3 Precast Concrete Structures Propping Propping is a technique which is used to increase the service moment capacity by reversing the Stage 1 stresses particularly at mid-span. This is achieved by placing a rigidly founded support, `Acrow prop' or similar, in the desired place whilst the in situ concrete topping is hardening (see Figure 4.26). To ensure that the props are always effective, many contractors prefer to use two
fcu b 0:9X in the concrete 5:37 Fs Æfpb Aps for each row of strands below the top of the boot 5:38 Hence X is found and resubstituted into Eq. 5.35 for iteration. The analysis is clearly long and tedious and involves having to calculate fpb at each level. An approximate method is to consider that the average strain exists at the centroid of the strands in the tension zone, i.e. g dT where dT is the effective depth to these strands. Equations 5.35±5.38 are still valid. The ultimate moment
the type of connection, corbel or haunch. The distance x from the face of the column to the centre of the beam-end reaction should include tolerances Á to allow for manufacturing and erection errors. 15 mm is recommended, although most erectors would say this was very generous. The maximum eccentricity is given as: h e xÁ 2 x h 6:6 x Dimensional and construction tolerance Δ Δ Centre of bearing c c Steel insert (RHS, solid) Concrete corbel (or nib) Figure 6.12: Column bending moments