Check that deflection (excessive deflections will … The shear force that is resisted by shear reinforcements is Vs = (Vu - fVc). In this case, ring or circular raft is the best suitable foundation to the natural geometry of such structures. The dimensions of columns, reinforcement and column loads are shown in the same Figure (87). Live load: 800 lb/ft. 6 Version 2.3 May 2008 comparatively larger than the “elastic” one prior to failure. The following text gives a description of the design properties and parameters. Normally, stirrup is spaced vertically at a spacing, s, for shear reinforcement. Concrete is assumed to resist compression only, tension shall be resisted by reinforcements. In the first one, the footings are designed as isolated footings without connection among them, while in the second, the footings are designed as connected footings with tie beams to reduce the differential settlements among them and footing rotations. A square raft has dimensions of 10 [m] × 10 [m] is chosen. The choice of this reduced wall height because the wall above the first floor has many openings. Due to the site conditions, the projections of the footing beyond the centers of columns C1 and C2 are limited to 0.90 [m] and 1.30 [m], respectively. Column C1 is 0.50 [m] × 0.50 [m], reinforced by 8Φ16 [mm] and carries a load of 1200 [kN]. Design of Reinforced Concrete, 10th Edition by Jack McCormac and Russell Brown, introduces the fundamentals of reinforced concrete design in a clear and comprehensive manner and grounded in the basic principles of mechanics of solids. The use of the ribbed raft relates to its simplicity in analysis by traditional manners or hand calculations. The girders on the raft may be either down or up the slab. When a reinforced concrete beam fails in yielding of steel, the failure is ductile because the steel can stretch for a long period of time before it actually breaks. The resultant of compressive stress, C is located at a distance, a/2, from the top surface. Correspondingly, the distribution of contact pressure will be uniform. Concrete reaches its maximum strength at 0.85f c ' first. In this example two types of rafts, flat and ribbed rafts, are considered as shown in Figure (49). Column sides are 0.50 [m] × 0.50 [m], while column reinforcement is 8Φ19. When fvc < vs £ 4Öfc, max s = d/2 £ 24 in. For slabs spanning in both directions published tables and charts should be used to find bending moment and shear per unit width of slab. The footing rests on Winkler springs have modulus of subgrade reaction of, This example is carried out to show the differences in the design results when the raft is analyzed by different soil models. Such ability is In addition, a slab on the fill material is required to be constructed for the first floor. GEOTEC Software is providing universities and consulting companies by the right tools for the last 20 years. Within an effective depth d, the shear strength provided by Avfyd/s, where Av is area of stirrup, fy is yield strength of reinforcing steel. Civil Engineering Design (1) 10 Dr. C. Caprani 2. The simply-supported beam has a span ‘ = 18 ft and excessive deflections will cause damage. The shear strength multiply by a reduction factor, f, needs to be larger than Vs. Part III: Design of Reinforced Concrete Slabs 9. There is a nominal strength that is reduced by a factor which must exceed the factored design … A thin plain concrete of thickness 0.15 [m] is chosen under the footing and is not considered in any calculation. By equilibrium, the tensile force is equal to the compression resultant. Therefore, Vs = f(Avfyd/s). The design must be carried out twice. A square raft has dimensions of 10 [m] × 10 [m] is chosen. Stirrup for shear reinforcement is normally placed vertically to intercept the crack. The length of each raft is L = 14.3 [m] while the width is B = 28.3 [m]. A simply supported reinforced concrete beam is supporting uniform dead and live loads, Compressive strength of concrete: 4000 psi, Requirement:  Design flexural reinforcement for bending, Weight of beam: WB = 150 lb/ft x 1.33 ft x 2 ft = 400 lb/ft, Factored load: Wu = 1.4(400+1500)+1.7(800) = 4020 lb/ft, Factored moment: Mu = (4020)(202)/8 = 201000 ft-lb, Assume the main reinforcement bar is 1" in diameter (#8 bar), Effective depth: d:24-1.5-0.5-0.5 = 21.5 in. The core lies in the center of the building and it does not subject to any significant lateral applied loading. In the primary design of footings or rafts, it is generally assumed that the contact pressure distribution is planar, whatever the type of model used in the analysis of the footing. Students build on their understanding of basic mechanics to learn new concepts such as compressive stress and strain in concrete… The diameter of the core wall is 8.0 [m], while the width of the wall is, Case 2: A height of only one storey is taken into account, where the perimeter wall is modeled by beams having the flexural properties of, A ribbed raft may be used where the distance between columns is so great that a flat raft requires excessive depth, with resulting high bending moments.