Steel Buildings in Europe

Part 2: Concept Design 2 - 52 Table 5.5 Minimum widths for bearing of PC units Minimum beam width Internal beam 180 mm 75 mm or 100 mm deep solid precast unit Edge beam 210 mm Internal beam 180 mm Hollow core precast unit Edge beam 210 mm Non-composite edge beam 120 mm Edge beams are often designed as non-composite, with nom inal shear connection provided to meet robustness and stability requirements. These shear connectors are usually site-welded thr ough openings cast in the precast units. Composite edge beam s require careful de tailing of U-bar reinf orcement in to slots in the precast concrete units, and a greater minimum flange width. Temporary bracing providing lateral rest raint is often required to reduce the effective le ngth f or latera l tors ional bucklin g of the beam during the construction stage, when only one side is loaded . Full tors ional restraint in the temporary condition may be difficult to achieve, unless deep restraint members with rigid connections are used, or by developing ‘U-fram e action’ involving the beams, the restraint members and rigid connections. 5.5.2 Beam span and design criteria Long span secondary beam s should pr ovide sufficient m inimum width to support the P.C. units as given in Table 5.5, so an IPE 400 mm is the minimum practical beam depth. Beams that are pl aced parallel to th e span of the precas t units cannot usually be designed compositely. Edge beams are generally designed as non-composite, but are tied into the floor to meet robustness requirements. Transverse reinforcement must be provided in all com posite design cases, as shown in Figure 5.11 and Figure 5.12. The critica l check is of ten torsional resis tance and twist, or com bined torsion and lateral torsional buck ling resistance in the cons truction condition (with loads on one side only).