Long span beams | Link to download: https://dimpstrail.gumroad.com/l/ydbbq
Long span eams, its types and a case study. What are Long Span Beams ? • Beams greater than 30 metres in span are said to be Long Span Beams. • Uses of Long Span Beams includes : 1. Flexible, column free internal spaces. 2. Reduced steel erection times. 3. To facilitate the integration of services without increasing the overall depth. Types of Long Span Beams ? 1. Parallel Beam Approach: • Effective for spans upto 14m. • Floor grids comprise of two layers of fully continuous beams running in orthogonal direction. • Services can be integrated with these two layers, so that services is accommodated within the structural floor depth. • Depth of the beams is reduced. 2. Composite Beams with web openings: • Effective for spans upto 10m – 16m. • It allows services to pass through the section thereby reducing overall depth of the beam. • The alternative way of forming the web openings is simply to cut them into the plate used form the web of a plate girder, or the web of a rolled section. • The openings introduce a number of potential failure modes not found in solid web beams. Large openings may require stiffening to avoid instability (buckling) of the web posts. 3. Tapered Girders: • Effective for spans upto 10m – 20m. • They are another solution that allows services to be accommodated within the structural floor zone. • The depth of the girder increases towards mid-span, where applied moments are greatest, thereby facilitating hanging services under the shallower regions near the beam supports. • It is also possible to form web openings in tapered girders in regions of low shear, towards mid-span. These provide more options for service integration. 4. Stub Girder: • Effective for spans more than 20m. • Stub girders Stub girders are a Vierendeel form of truss. The bottom chord is typically formed from a shallow open section (H- beam), on which sit short lengths (stubs) of deeper I- sections. • Services and/or secondary beams can pass through the gaps between the beam stubs, reducing overall construction. 5. Haunched Composite Beams: • Spans more than 20m can be easily achieved. • Haunches may be added at the ends of a composite beam to provide moment continuity. 6. Composite Trusses: • Composite trusses, which use the concrete slab as the upper chord in the final state, can achieve spans in excess of 20 m. • This means they have been used when very long spanning capability was needed. • Clearly one of the prices to pay for the spanning ability is that fabrication cost is higher than for a plain beam.
