Concrete Fooring & Roofing System CONCRETE FLOORING & ROOFING SYSTEM Concrete Fooring & Roofing System
Concrete Fooring & Roofing System Reinforced concrete floor is called “SLAB”. Slab is generally constructed in two major types : slab on grade and slab on beam. SLAB ON GRADE or SLAB ON GROUND can construct only on ground floor that touch the earth. It distributes load directly on the soil or compacted sand. The ground beam is only tied the columns and to be building perimeter. The initial construction cost is cheaper than the other type because formwork can be omitted at the slab underside. The disadvantage of slab on grade is the differential settlement due to soil settlement. Cracking usually occurs at the joint of slab and beam and at the slab surface. Then major maintenance is often needed at high cost. SLAB ON BEAM can construct at all levels. It transfers load to beam and then on to the columns. This can ensure differential settlement up to one point. The initial construction cost is higher than slab on grade because formwork at the slab underside and the reinforcement to join beam and slab is needed. Slab can be classified by load transfer system and construction methods. The two classifications are mainly concern on slab on beam. Concrete Fooring & Roofing System
Concrete Fooring & Roofing System Concrete slab classified by load transfer system 1. One-way slab A pair of beam or bearing wall is designed to transfer load from slab. One-way slab is used with short span range from 1.80-3.60 m. Rectangular shaped slab (w : L = 1: 3) also appropriate to use one way slab system. Bottom reinforced bars resist tensile stress. Top bars are used as temperature steel to prevent cracking Concrete Fooring & Roofing System
Concrete Fooring & Roofing System
Concrete Fooring & Roofing System 2. Two-way slab with beam Two pairs of beam are designed to transfer load from slab to the four columns. Bay should be as nearly square as possible. Two-way slab is used with long span and heavy loads, or when high lateral force resistance is required. Concrete Fooring & Roofing System
Concrete Fooring & Roofing System
Concrete Fooring & Roofing System 3. One-way concrete joist system (ribbed slab) Ribbed slab is used for long spans and heavier load than one-way slab. Broader joists at beam (joist band) can resist greater shear. Concrete Fooring & Roofing System
Concrete Fooring & Roofing System
Concrete Fooring & Roofing System 4. Two-way concrete joist system (waffle slab) Waffle slab is used for long spans heavy loads. Bays should be as square as possible. Concrete Fooring & Roofing System
Concrete Fooring & Roofing System
Concrete Fooring & Roofing System ANALYSIS MODEL OF A WAFFLE SLAB WITH MODERATE SIZE SOLID SLAB BANDS ALONG SELECTED LINES OF SUPPORT Concrete Fooring & Roofing System
Concrete Fooring & Roofing System ANALYSIS OF A LONG-SPAN WAFFLE SLAB WITH STOUT SOLID SLAB BANDS ALONG THE LINES OF SUPPORTS Concrete Fooring & Roofing System
Concrete Fooring & Roofing System 5. Two-way flat slab Flat slab is supported by columns without beams. Drop panel, which min. width of 0.45 span and min. 6. Two-way flat plate Two-way flat slab and two-way flat plate can be constructed by post tension system. Post tension is the technology that stretch reinforcement steel with hydraulic jack and securely anchored after concrete is cured. Concrete Fooring & Roofing System
Concrete Fooring & Roofing System
Concrete Fooring & Roofing System Precast reinforced concrete hollow core deck slab Due to a special coating system the hollow cores can be used as ventilation ducts. Therefore, no suspended ceilings or enhanced floors will shorten the room height or increase the price. Other advances are lower air speeds, minor loss of pressure, reduced streaming noises and less energy consumption. Concrete Fooring & Roofing System
Concrete Fooring & Roofing System Concrete slab classified by construction methods 1. Cast-in-place (sitecast) can be either slab on grade or slab on beam 2. Pre-cast (prestressed, prefabricate) Four major types of precast concrete slab Disadvantage of precast slab is water leakage through joint between slab. Water can leak through concrete topping if it has crack line. Therefore, precast slab is not appropriate to use at roof deck, balcony and toilet. Precast components assembly Concrete Fooring & Roofing System
Concrete Fooring & Roofing System