However, this is not the only means of reinforcing slabs. All Rights Reserved. concrete: 2500 psi min. Words: 2,469; Pages: 4; Preview; Full text; CRSI REINFORCING STEEL IN SLABS-ON-GRADE ENGINEERING DATA REPORT NUMBER 37 A SERVICE OF THE CONCRETE REINFORCING STEEL INSTITUTE 933 N. Plum Grove Rd., Schaumburg, Illinois 60173-4758 WELDED WIRE FADRIC REINFORCING BARS INTRODUCTION The phrase slab-on-grade… At 40 pounds per cubic yard or more, a good midrange or high-range water reducer (the latter at a low dosage) can be very helpful and is necessary as fiber dosages increase. Concrete is very strong when it is squeezed in compression but very weak when it is being pulled apart in tension. Main cranked bars: These are also main bars but the bar is cranked at 45 degrees. The grade of steel should be evidently mentioned in the drawing. The closer the steel is to the top of the slab and the more steel used, the more curling will be reduced. As indicated above, spacings for laps shall be followed and the gap between the lapping bars shall not be less than 50mm or 4∅ whichever lesser. 6.4K views; Total. Until that point, it is mostly inactive inside your slab. However, if the cracks become wide enough to spall, this can be major problem. 0. Simplified Rule for Slab Reinforcement Details; The simplified rules can be applied when slab reinforcement detail drawings are prepared when the following condition is met. 0. This is due to being able to drive the concrete trucks and laser screed over them as they lay on the base and then chairing them up just ahead of the concrete placement, as the workers stand between the bars. The fibers decrease the slump of the concrete, but this can be compensated for by proper mix materials and proportioning. For 0.10% reinforcing, the slab joint spacing should be the same as for an un-reinforced slab. slab: 4” minimum thickness with w or d9 wire 10” o.c. Thus, the reinforcing is supposed to enhance aggregate interlock, which normally cannot be depended upon for long-term load transfer of repetitive loads if the crack is 0.025 to 0.035 inches or wider, per Portland Cement Association's research. Slab On Grade Reinforcement Details. A rectangular reinforced concrete slab is simply- supported on two masonry walls 250 mm thick and 3.75 m apart. have discussed in addition to other aspects. A frost protected shallow foundation jlc online anchor reinforcement for concrete podium slabs simpson strong tie structural engineering blog structure magazine recommended details reinforced construction building guidelines drawings section b: slab on grade versus framed journal of architectural vol 16 no 4 The design procedure includes determini ng slab thickness based In some situations, it is desirable to eliminate contraction joints in large placements and use enough reinforcing to have many, very tight cracks that do not spall under wheel traffic and are not an aesthetic issue; a common example is a true “superflat” slab strip placement. both ways. Slab on Grade: Slabs which are directly laid on the earth, to support walls and other structural elements are called as Slab on grade or Grade Slabs. The most common reinforcement associated with slabs-on-grade is welded wire fabric. Otherwise, as an average, we could continue the top reinforcement 0.25 x span (from the face of support). placed before the main slab reinforcement. The design of a slab-on-grade includes all decisionsanddetailsmadebeforethejobisbidand constructed. Building guidelines drawings section b: concrete construction anchor reinforcement for podium slabs simpson strong tie structural engineering blog structure magazine recommended details reinforced slab on grade stud wall thickened edge walls. In simply supported beams the main bars placed at bottom and in case of cantilever beam these bars are placed at top. 24.Kas.2016 - Waffle Slab End Support Reinforcement Detail. Furthermore, the great majority of reinforced concrete designs that have been reviewed for slabs on ground do not have enough reinforcing to actually increase the slab's load-carrying capacity above that of an unreinforced slab. If there is a sufficient quantity for a particular situation—based on slab usage, joint spacing, concrete shrinkage potential, etc.—the post-crack load-carrying ability of steel fibers can be very beneficial. Many opinions have been voiced regarding the best vertical location for a single layer of reinforcing for slabs on ground. In construction, a grade slab is a relatively flat concrete structure built on top of the soil at ground level. k. Reinforced slab. Element designs with notes and discussions have added to get comprehensive knowledge. This insulation aligns with rigid foam sheathing that covers the framed walls above grade. Slab supported on two sides and bending takes place predominantly in … The detailing rules could also be applied as per Eurocode 2. Slab may be supported on walls or beams or columns. The rigid insulation is placed vertically on the exterior face of the grade beam. If reinforcing is utilized, the amount that should be used depends on what is to be accomplished. Thus, the higher the reinforcement, the tighter it will hold any cracks running perpendicular to the direction of the reinforcement. k. Reinforced slab. Let’s discussed the design code requirement specified for slab reinforcement details. Reinforcement detailing of a slab is done based on its support conditions. Steel fibers have been available in the U.S. since the mid-1970s. As with steel bar and wire reinforcement, steel fibers will not prevent cracks but can keep cracks, if they occur, reasonably tight if a sufficient amount of fiber and an appropriate joint spacing are used. Reinforcement amounts much less than 0.10% have not provided dependable load transfer; and much more than this has caused excessive out-of-joint cracking. One thought on “ Concrete Slab-on-grade Reinforcement ” Dan Lindberg January 15, 2021 at 10:42 am. There are many opinions floating around as to the benefits, or lack thereof, of reinforcement in slabs on ground. To be able to understand the potential benefits and negatives of any particular reinforcement system, one has to understand how that system theoretically works and also what happens in the real world. When above a, b, and c conditions do not apply, bar spacing shall be limited as following Table (Table 28 of BS 8110 Part ) where the reinforcement percentage exceeds 1% or the values given in Table 28 divided by the reinforcement percentage for lesser amounts. Provide reinforcement area of 0.13%. Slab reinforcement details are the same as the wall reinforcements as specified in the Cl 3.9.4.19 in the BS 8110. In some cases deformed bars are used in order to assure that the reinforcement is placed at the correct depth within the slab and not damaged during placement. See n otes below. Grade slab itself acts as a foundation for the building which does not require further footings. Not all reinforcement works the same way. But that was the old days when fiber 1st came out. A frost protected shallow foundation jlc online anchor reinforcement for concrete podium slabs simpson strong tie structural engineering blog structure magazine recommended details reinforced construction building guidelines drawings section b: slab on grade versus framed journal of architectural vol 16 no 4 Here, ∅ is the bar diameter. However, 100% area of steel needs to be continued up to 0.15 x span. In either case when using deformed bars or welded wire fabric, it is essential As indicated above, spacings for laps shall be followed and the gap between the lapping bars shall not be less than 50mm or 4∅ whichever lesser. 0. Structural Guide © 2021. 0. Slab curling produces a significant tension stress in the top of all normal concrete slabs; if cracks do occur they are V-shaped with the widest portion at the top of the slab. However, if the reinforcing is too high it can cause plastic settlement cracks, which run directly over the top and parallel to each bar or wire. THE SLAB DESIGN 10 BEAM SPACING AND LOCATION 12 SLAB REINFORCING 13 BEAM REINFORCING 13 SITE PREPARATION 14 SLAB FORMING 15 STEEL PLACEMENT 16 SPECIAL CONDITIONS 19 CONCRETE PLACING 20 ... grade before construction. We just went through some of this with a new concrete pad in front of the garage. Fire test of concrete slab reinforced with epoxy-coated bars. Basic considerations. Wearing surface – the exposed surface of the floor, which typically receives some sort of surface treatment, be it a paint, sealant or a screed. Any particular added details for this (I'm used to option 2 typical detail)? The availability and use of early-entry saws has made this method even more dependable because the sawcuts must be made as soon as feasible. Figure 4-9 illustrates a slab-on-grade foundation with an integral grade beam. This type of slab is casted directly on ground level. 1-4. analysis indicate a slab of lighter or heavier design is suitable. Areas of reinforcement for slab design Table A-9, text Standard bar details (cut-off locations) for slabs & beams Figure A-5, text Background Many types of reinforced concrete slabs exist including: slabs on grade, one-way slabs, two-way slabs, and composite floors (see figure on next page) slab-on-grade: slab cast against the ground. Concrete Slab on Grade Stair Concrete Slab on Grade Stair RFreund (Structural) (OP) 27 Jun 14 13:53. Steel Fiber Reinforcement for Slab-on-Grade Applications CFS 100-2 steel fibers help control random cracks in ground-supported concrete floors. 0. The design procedure includes determining slab thickness based maximum clear panel between beams is 15 feet.beams: 10” wide by 30” deep. read more: Curing of Concrete | Curing time & Duration | Curing methods. Type 1 fiber is made of drawn wire of various geometries and Type 2 utilizes slit sheet steel. Crack Control – when crack widths are not checked by calculations No Further Checked Required, Simplified Rule for Slab Reinforcement Details, Slab Reinforcement Details at Restrain Edges, Column Reinforcement Details [Must Check], Expansion Joints in Concrete [ why when how ], Typical Waterproofing Details in Buildings, The slab is designing for uniformly distributed loads, In continuous slabs, design loads are approximate equal. Concrete slab resting on grade containing steel reinforcement which consists of either a welded wire fabric or deformed reinforcing steel bars. The simplified rules can be applied when slab reinforcement detail drawings are prepared when the following condition is met. The slab is designing for uniformly distributed loads; In continuous slabs, design loads are approximate equal Fig: Detailing of medium slab openings. In ordinary jointed floors, steel fibers provide a safety net by limiting the width of any cracks that occur between the joints. laps or splices: minimum 30 diameters. According to ACI Code 7.12.2.1, for the shrinkage and temperature reinforcement, Slabs with grade 40 or 50 deformed bars = 0.0020 psi. 1-4. Anchorage of Bars at a Simply Supported End. Slab reinforcement details should be done by following the relevant code of practices and standards method of detailing of reinforcements. This deformed reinforcement is an alternative to smooth steel dowels, and slab expert Eldon Tipping has coined the term “long dowels” for this concept. Reinforcement detail for a waffle slab support on a reinforced concrete main frame end slab beam. Demonstrate enlarged details at corners, junctions of walls, beams and column joint and at same situations. 3.9K Shares . The design procedure includes determini ng slab thickness based Main straight bars: These bars are placed in tension zone. Subslab insulation is placed horizontally, and extends down the sloped sides of the grade … So, if the bars are spaced at 12 inches on center and relatively straight cracks are observed every 12 inches, this type of cracking has occurred. 4.1 Recommended Design and Construction Details . Reinforcement ratio can be defined as the ratio of reinforcement area to gross concrete area based on the total depth of the slab. Concrete slab resting on grade containing steel reinforcement which consists of either a welded wire fabric or deformed reinforcing steel bars. Min. than its tensile strength. Notes for excavating a Slab on Grade foundation: 1) When beginning with a rubble trench for the load bearing part of a foundation (as per instructions from an engineer), pit run gravel can be a more affordable option than crushed stone. Guidance for joint spacing to minimize out-of-joint cracking for such slabs is given in ACI 360 and typically should be in the 10- to 15-foot range noted earlier. The materials to be used are grade C25 concrete and grade … SLABS ON GRADE – IDENTIFYING THE PROBLEM Slab-on-ground is a well-used building solution in North America and other parts of the world, and they are very well known to not provide healthy interior environments. These cracks will be visible, thus the aesthetics of these cracks should be discussed with the owner. 2) Ask your contractor to protect topsoil for future use. Thus, unless the reinforcing is being used for other purposes (such as the “long dowel/enhanced aggregate interlock” concept noted later in this article), it is typically somewhat expensive insurance for a cracking problem that may never occur if other appropriate procedures are followed, such as proper joint spacing, dowels at joints, consistent slab thickness tolerance control, good base control, and low shrinkage mix design. Slab may be supported on walls or beams or columns. = 0.10%. Publication: Concrete International Date: 8/1/2020 SP-339-06: Analysis and Design of Reinforced Cast-in-Place Concrete Diaphragms Locating the reinforcement in the upper part of the slab is best when trying to control the visible crack widths due to the loading, curling, and base friction. 0. k. Reinforced slab. Also, construction materials, shoring system design, water retaining structures, crack width calculations, etc. The perimeter of the slab will have an expansion joint installed to separate the exterior walls, or foundation wall from the actual slab. More details. The chances for plastic settlement cracks increase as one or more of the following occurs: reinforcing diameter increases, concrete cover decreases, reinforcing temperature increases typically from sunlight, concrete bleed rate increases, reinforcing movement while the concrete is still plastic, or anything that increases moisture evaporation rate from the slab surface, such as higher concrete or ambient temperatures, higher wind speed, or lower humidity. slab on grade reinforcement slab on grade reinforcement details slab on grade reinforcement calculator slab on grade … Three of the more obvious items included in the design process are slab thickness, reinforcementrequirementsandjointspacings.After determiningthecontrollingloadings,theappropriate safetyfactor,andthesubgrademodulusappropriate 3. Steel reinforcing bars and welded wire reinforcement are very strong in tension, have similar thermal expansion and contraction properties to those of the concrete, and thus can handle high-tension stresses while the concrete can take substantial compressive stresses. Basic considerations. Locating the reinforcement in the upper part of the slab is best when trying to control the visible crack widths due to the loading, curling, and base friction. The article slab design could be referred for slab reinforcement design aspects. Properly sized and located reinforcing will keep cracks reasonably tight and serviceable, if they occur, but will not prevent them. a) Slab depth does not exceed 250mm when the steel grade is 250, b) Slab depth does not exceed 200 mm when the steel grade is 460, c) Slab reinforcement percentage less than 0.3% (100As/bd < 0.3%. Up next . … Concrete slab rest ing on grade cont aining steel reinforcement which consists of either a welded wire fabric or deformed reinforcing steel bars. #3 reinforcing bars at 16 or 18 inches on center are the most common reinforcing schemes used on slabs constructed with a laser screed. Publication: Structural Journal Date: 9/1/2019 Punching Shear Tests of Slabs … JOURNAL Articles ON SLAB ON GRADE An Approximate Model to Predict Stress and Displacement of Cross-Tensioned Prestressed Concrete Pavement under Temperature Loading. Reinforcement details of beam and Slab. SP-066(04): ACI Detailing Manual-2004. Rebar – Guide for Design and Construction. )(100)/(6 in.) Slab curling produces a significant tension stress in the top of all normal concrete slabs; if cracks do occur they are V-shaped with the widest portion at the top of the slab. In this research, optimum design of reinforced cement concrete (RCC) ribbed slab, also known as waffle slab according to the Indian RCC code (IS 456:2000) is presented. ACI PRC-439.6-19: Guide for the Use of ASTM A1035/A1035M Type CS Grade 100 (690) Steel Bars for Structural Concrete. The following slab reinforcement arrangements are specified in the BS 8110 Part 01. In general, there are similar requirements for one-way, and two ways slab when slab reinforcement detail drawings are prepared. Other considerations that play a role in the successful construction of a slab on grade include; proper proportioning of the concrete According to the above detail in the BS 8110, slab to reinforcements need to extend 0.3 x span(from the face of the support) for continuous support. Publication: Journal Proceedings Date: 12/1/1978 Grade 80 Reinforcing Bars and ACI 318-71 Generally, if one side is more than double of the other one, the slab will be one way. Numbering shall start at D1 The location of reinforcing bars in relation to each other, particularly in connection details such as column to headstock, pile to pilecap and footing to column, should be closely examined to ensure that bars may be easily placed and that concrete compaction in that area can be achieved. The main reason for the extra care is that curling increases significantly with every 1-foot increase in joint spacing, thereby significantly increasing the chances for out-of-joint cracking of unacceptable widths and joint problems. 0. As with steel bar or wire reinforcing, care must be taken if the joint spacing is extended beyond this specification. Method of splicing shall always be defined For example, if a 6-inch-thick slab is used with #3 rebar at 18 inches on center, the percentage of steel for a 12-inch width would be: (0.11 in.2)(12 in./18 in. Slab On Grade Reinforcement Details. 0. Slab supported directly by columns are called flat slab. Advantages and disadvantages of each of these slab designs are provided, including the ability of some slab designs to minimize cracking and curling more than others. These joints usually will open more than those with joints at typical spacings of 10 to 15 feet. Generally, the reinforcing is located a third to a half of the slab depth from the top so that the sawcut will not cut the reinforcement. Provide 0.25% of the concrete crossectional area for Grade 460 steel. The normal slab on grade is reinforced with WWF or fiber strands to reduce cracking due to shrinkage and or expansion. Concrete floor slabs on grade are subjected to a variety of loads and loading conditions. Basic considerations. This can reduce the required depth of the slab in colder climates. Building guidelines drawings section b: concrete construction anchor reinforcement for podium slabs simpson strong tie structural engineering blog structure magazine recommended details reinforced slab on grade stud wall thickened edge walls. reinforced concrete slabs-on-ground, and slabs-on-ground in refrigerated buildings, followed by information on shrinkage and curling problems. The following figure is taken from BS 8110 for reference. Concrete floor slabs on grade are subjected to a variety of loads and loading conditions. The… Many people believe that slabs on ground typically should have some reinforcing, but most slabs in North America are unreinforced concrete and perform well.
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