Arch205 building construction floor & Roof systems Prepared By: joshima v.m.

Floor system Floor systems are the horizontal planes that must support both: live loads—people, furnishings, and movable equipment dead loads—the weight of the floor construction itself. Floor systems must transfer their loads horizontally across space to either beams and columns or to loadbearing walls.

Concrete beam Effective Beam Depth 38mm minimum cover required to protect steel reinforcement from fire and corrosion. Beam Depth Concrete beam depth = span/16 Bevel or Chamfer Beam width

Concrete floor slab types One-Way Slab A one-way slab is uniformly thick, reinforced in one direction, and cast integrally with parallel supporting beams. Suitable for light to moderate loads over relatively short spans of (1.8 to 5.5 m)

Concrete floor slab types One-Way Joist Slab A joist or ribbed slab is cast integrally with a series of closely spaced joists, which in turn are supported by a parallel set of beams. Designed as a series of T-beams, joist slabs are more suitable for longer spans and heavier loads than one-way slabs. Suitable for light to medium live loads over spans of (4 to 10 m)

Concrete floor slab types Two-Way Slab and Beam A two-way slab of uniform thickness may be reinforced in two directions and cast integrally with supporting beams and columns on all four sides of square or nearly square bays. 100 minimum slab depth. suitable for carrying intermediate to heavy loads over (4.6 to 12 m) spans.

Concrete floor slab types Two-Way Waffle Slab A waffle slab is a two-way concrete slab reinforced by ribs in two directions. Waffle slabs are able to carry heavier loads and span longer distances than flat slabs. Suitable for spans of (7 to 16 m) (75 to 115) slab depth (125 or 150) rib width

Concrete floor slab types Two-Way Flat Plate A flat plate is a concrete slab of uniform thickness reinforced in two or more directions and supported directly by columns without beams or girders. Simplicity of forming, lower floor-to-floor heights, and some flexibility in column placement make flat plates practical for apartment and hotel construction. Suitable for light live to moderate loads over relatively short spans of (3.6 to 7 m)

Concrete floor slab types Two-Way Flat Slab A flat slab is a flat plate thickened at its column supports to increase its shear strength and moment-resisting capacity. Suitable for relatively heavy loads and spans from (6 to 12 m).

Concrete slab formwork and Shoring Knee brace Plywood/metal sheathing Blocking Kickers Metal/wood joists Stringers Support for Beam Formwork Adjustable Wood/Metal shores Wood shores Bracing on shores

Flying forms Flying forms are large sections of formwork, including supporting trusses, beams, or scaffolding, that can be moved by a crane in constructing the concrete floors and roofs of multistory buildings.

Lift-slab construction Lift-slab construction is a technique of constructing multistory buildings in which all horizontal slabs are cast at ground level and, when cured, are raised into position by hydraulic jacks.

Structural steel floor One way beam system Typical span range for beams is (6 to 10 m). Beams Girders Columns

Structural steel floor Two-Way Beam System Secondary Beams Primary Beams Columns

Open-web joists Open-web joists are lightweight, shop-fabricated steel members having a trussed web. Ceiling can be either attached to the bottom of the joist or suspended or left without ceiling. Passage of mechanical services through the open web

Roof system The roof system functions as the primary sheltering element for the interior spaces of a building. The construction of a roof should also control the passage of moisture vapor, the infiltration of air, and the flow of heat and solar radiation. The roof structure and assembly may have to resist the spread of fire. The form of a roof structure—whether flat or pitched, gabled or hipped, broad and sheltering, or rhythmically articulated—has a major impact on the image of a building.

Roof types Flat roofs require a continuous membrane roofing material. Minimum recommended slope: 1:50. Reinforced Concrete Slab Flat Timber or Steel Truss Timber or Steel Beams and Decking Wood or Steel Joists and Sheathing

Sloping roofs may be categorized into • Low-slope roofs—up to 3:12 • Medium- to high-slope roofs—4:12 to 12:12 Sloping roofs shed rainwater easily to eave gutters. Wood or steel rafters and sheathing. Timber or steel beams, purlins, and decking. Timber or steel trusses.

Concrete roof slab Details of concrete roof slabs are similar to that of concrete floor slabs. Section showing layers of concrete roof slab:

Edge treatment of roof slab An upturned edge beam can form a parapet wall. The slab can be cantilevered beyond its perimeter supports to form an overhang. An edge or spandrel beam can support a nonbearing curtain wall. Metal anchors may be cast into the spandrel beams to secure the curtain wall panels.

Reinforced concrete may be designed and cast into a variety of other roof forms, such as folded plates, domes, and shell structures.

Steel trusses Flat trusses have parallel top and bottom chords. Flat trusses are generally not as efficient as pitched or bowstring trusses. Pratt trusses have vertical web members in compression and diagonal web members in tension.

Howe trusses have vertical web members in tension and diagonal web members in compression. Belgian trusses have only inclined web members. Fink trusses are Belgian trusses having subdiagonals to reduce the length of compression web members toward the centerline of the span.

Warren trusses have inclined web members forming a series of equilateral triangles. Bowstring trusses have a curved top chord meeting a straight bottom chord at each end. Raised-chord trusses have a bottom chord raised substantially above the level of the supports. Scissors trusses have tension members extending from the foot of each top chord to an intermediate point on the opposite top chord.

Steel trusses Members are bolted or welded with gusset roof decking plate connectors. roof decking Channel or W-shape purlins Steel bearing plate lateral bracing in a direction perpendicular to their planes Structural steel or reinforced concrete column support Mechanical services