INSTRUCTIONS: Choose units and enter the following: (r) Radius of Circular Slab (e. Concrete foundations are the cheapest type of home foundation and are the easiest to install and maintain. According to this method, you will need two rebars for a footing width of 16 inches, four rebars for a footing width of 24 inches, and so on. By special permission of the publishers, Co n c re t eproject has two structures, both of them have removal of concrete, class B concrete, and new strip seal expansion devices. INSTRUCTIONS: Choose units and enter the following: ( L) Length of the slab. The Calculation. Chapter 19 relies primarily on the reference to American Concrete Institute (ACI) 318, Building Code Requirements for Structural Concrete. . Cut your frame to size and use nails or screws to secure your frame together. 2, see D. The resulting one-way structural system has a T-section. 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: For enough reinforcing to accomplish. As the slab length increases, the contact area with the base material increases, which increases the total resisting frictional force, resulting in higher tensile stresses as the slab contracts and/or loses moisture. A rebar slab calculator is a tool used to determine the quantity and spacing of reinforcing bars (rebars) needed in a concrete slab. 10m= 3m3. The average cost of a concrete slab is $8. 3 cubic feet of concrete for this slab. Inches. This gives you the weight required. In other words, post-tensioning pre-compresses the concrete to help prevent cracking from occurring rather thanA minimum area of shear reinforcement should be provided in all regions of a beam where applied shear is greater than half the designed shear strength of concrete. Next, divide the total square footage by the size of the rebar. A slab layout plan is a drawing that you’ll get in the structural drawing book. Generally, the minimum amount of rebar recommended by the American Concrete Institute (ACI) is at least one vertical bar per cubic yard of concrete and two horizontal bars, either laid flat or tied together with wire. d = 150 mm _ 26 mm. Common rebar sizes range from #3 to #6 for slab footings, with #4 being the most commonly used. Concrete. Shop Concrete Mix. . It’s a time-saving solution that eliminates the need. 25 per linear foot, and prices increase up to $9. Use a tamper or plate compactor to flatten the gravel base. 19 c rc c c ' c '. 1R-04. To calculate the total rebar needed, multiply the linear footage of your foundation (340) by the number of rebar sticks required across the. The current design codes discuss the effective compressive strengths of columns, which reflect a decrease in load transfer performance that can occur when columns and slabs have different concrete compressive strengths. Add 5%-10% additional material for some waste or spills. The term units refers to the same units as the slab length. It requires careful attention to detail and an understanding of the various. 35* (bw*s/fyt) Equation 5. The weight of a concrete slab can be estimated by computing the volume of the slab and multiplying the volume (V) by the density of the concrete. The size and type of rebar used in concrete slab footings will depend on the specific requirements of your project, including the size of the slab, the load it will support, and local building codes. If you want to combine rods of two diameters, there would. h – Distance between the reinforcement. The national average cost of a concrete slab for a garage is $6. EXAMPLE: Suppose we have a one-way slab, which has a length of 5 m or a width of 2 m (clear span). Calculate the Moment Capacity. · Enter the Thickness of the slab in mm only. The Clear cover will be 25 mm (Top or Bottom) and the thickness of the slab will be 150 mm. in contact lapping case, one side of the rebar is covered by the other rebar. This study presents structural performance of large scale two-way concrete slabs reinforced with FRP rebars, and their performances were compared against conventional steel reinforced. Reduction or elimination of random cracks. or ACI 318-11 Section 12. To figure out how much concrete you need to buy, you simply need to multiply the volume required by the density of the concrete mixture. of Main bars = 20 + 1 = 21 Nos. Concrete Slabs Calculator. The formula for the weight of a slab used in this calculator is: Wt = L•W•D•mD. 2) Development of the bar does NOT ensure that a concrete breakout failure will not occur. 3 of ACI 318. 56% and Equation b) for λ= 1 and ρ w > 1. Relative strength of wire mesh vs rebar for reinforcing a concrete slab. Commonly called “rebar,” these 1/2-inch-diameter steel rods are embedded in the center of the slab to create a grid that extends lengthwise and crosswise to help the concrete better resist pulling and bending forces. 28084 feet Rebar calculator for slab helps you find the total weight of steel rod required to construct the. " There is also a Settings button so. Any suggestions/comments are. The maximum weight of fly ash, other pozzolans, silica fume, slag or blended cements that is included in concrete mixtures for garage floor slabs and for exterior porches, carport slabs and steps that will be exposed to deicing chemicals shall not exceed the percentages of the total weight of cementitious materials specified in Section 19. Slabs, Square Footings & Walls. Slabs, Square Footings & Walls. We typically ask our structural engineer for the weight of rebar is per sf (slabs) or volume of concrete for each mix/use. There are also specific provisions addressing concrete slabs and shotcrete. 395 kg/m. (Rebar Calculation Formula) No. 3. This is usually taken to be 75% of the steel yield stress. For example, if the length is 10 feet and the width is 8 feet, the area would be 10 x 8 = 80 square feet. The compression development length is calculated using Section 25. Calculate how much rebar you need to reinforce a concrete slab. 4 Shear strength of two-way slabs Loads applied to a relatively small area of slabs create shear stress perpendicular to the edge(s) of the area of load application. The type of and intended use of concrete impacts the need for rebar reinforcement. com ©. , or 4 in. Table 5. Assume your longitude is 15 feet and there will be 14 inches between latitude rebar. "Guide for Concrete Floor and Slab Construction" ACI 360R-06. Specify the spacings: rebar-rebar spacing = 40 cm, edge-grid spacing = 8 cm. Running Bar Points (Length - Left to Right): Running Bar Points (Width - Top to Bottom): Calculate Rebar Quantity and Mesh From Total Slab Area and Perimeter. 2655 = 0. The research is focused on punching shear failure of reinforced ground supported slab. To truly reinforce concrete, the percentage. 2. All of these. Our chairs provide a 3″ ground clearance and 5. 33_6_0. Slab footing Rebar may be easily determined with the help of the footing Rebar calculator. There is two spacing between 3 reinforcement and 50 mm length both side of 1st and 3rd reinforcement used in footing. 4. Therefore, #2 rebar is ⅛” + ⅛” = ¼” in diameter. Phone: 800-347-7141 | Fax: 510-490-7179. Input all the dimensions in the input section of the above calculator. The user must enter the strengths of the concrete and the reinforcement, the unit weight of concrete, strength reduction factor for lightweight concrete, beam dimensions and slab. The pavement slab directldesign method consists of determining thy e opposite the mismatched joint should be reinforced percentage of steel required, the thickness of the with a minimum of 0. Slabs are defined as two-way slabs when the ratio of long-to-short sides is less than 2. 05 percent of steel ireinforced concrete pavement, and the minimun m directions normal to each other for a distance of 3 allowable length of the slabs. Start simply by entering "Add/edit Section" to add the main beam section. Like our other calculators, this reinforced concrete Beam Capacity Calculator is very easy to use. As such, I would do one of two things: 1) Effectively lap the rebar with the rebar in the elements above and below. 25 kg. The next thing that you need to consider is that every four feet of the foundation wall will require concrete and rebar. 65 and the thickness of the slab is 6 inches, M = 0. The rebar is built in a grid structure and costs $2 to $3 per square foot. All reinforced concrete references for slab design divide into one-way and two-way if the quotient of lb la l b l a is greater or less than a value of 2, respectively. The PT Calculator is ideal for owners, developers, contractors, architects, and engineers who need to quickly estimate quantities and concrete sizes. Making sure to keep the rebar as level as possible, you should place each piece one foot apart. In this method, forces transfer from one bar to the other through concrete. 6% concrete volume. If an end-to-end distance between the lap is the least, then the lap should be provided in a staggered manner. (as in example diagram) Multiply the 2 different side lengths of each rectangle to find individual areas, then add them together to find Total Slab Area . A concrete slab is a common structural element of modern buildings, consisting of a flat, horizontal surface made of cast concrete. 6m × 5m × 0. ( M) Number of mats. 2. The gauge, or diameter, of the rebar is selected based on the purpose and the load-bearing requirements of the structure: For standard. Minimum dimensions and axis distances for reinforced concrete slabs. Assuming that you are referring to the number of steel bars needed for reinforcing a concrete slab, the calculation depends on several factors, such as the steel type, grade, size, spacing, and the dimensions of the slab. Reinforced concrete for a 6-inch thick concrete slab: For a 6-inch thick slab, #4 (1/2-inch diameter) or #5 (5/8-inch diameter) thicker rebar is often used. In such a case, the straight lapping length of the reinforcement bars must be greater than 200mm or 15 x d. For example, the percentage of reinforcement of a 30-inch slab with two layers of No. 0. This is the formula: mesh needed = slab area ÷ mesh area. 74 sq feet 5000/2. The Length and Weight of Rebar in Concrete Slab calculator computes the total length and weight of rebar needed for one or more mats of rebar in a concrete slab. (feet + inches) Enter the grid spacing. For instance, if the area of reinforcement required (A s,req) from calculation is 523 mm 2 /m, you can provide H12@200 c/c (Area of steel provided A s,prov = 565 mm 2 /m). Substituting the diameter of 0. Building Supply Stores; Online Retailers; Wholesale Distributors. The Rebar for an Irregular Shaped Slab calculator estimates the total length and weight of reinforcement bars (rebar) needed for an irregular shaped concrete slab. 78. First, you must determine the width and length of. The minimum compression development length shall not be less than 200mm. 05 percent of steel ireinforced concrete pavement, and the minimun m directions normal to each other for a distance of 3 allowable length of the slabs. ©2023 PJ's Rebar | 45055 Fremont Blvd | Fremont CA 94538. The rebar within the concrete takes in some of the force applied to the concrete matrix. For example, if you are using ½ inch rebar, divide 60 feet by 0. For multi sided slab, first draw the shape: 1: Hit Clear + Start and enter Side Length of first side to draw, then hit appropriate direction (Arrow) button to draw. INSTRUCTIONS: Choose units and enter the following: Rebar Grid - One Mat (L) Length of Slab (W) Width of Slab (D) Depth of Slab (rS) Size of Rebar (none, 2-11,14,18) (i) Rebar Inset from the edge of the slab. You will get the results in kilograms (Kg). For example, if the length is 10 feet and the width is 8 feet, the area would be 10 x 8 = 80 square feet. CRSI’s Reinforced Concrete Concept is an online tool for preliminary slab design that provides design and construction teams with comparative evaluations and estimates for the most. As an example, using a relatively simple two-story steel-frame office building as a model, the work phases might include Mobilization, Foundations, Elevator Pit, Slab On Grade, Brace Frame Closures, Slab On Deck, Pan Filled Stairs, and General. Inputs can be either imperial or metric with results shown to. When reinforcement bars of different sizes are bundled as compression bars, the lap length chosen must be larger of the following cases: Compression splice length of the least diameter bar or. L = Depth – 2 times cover. (Imagine you are walking around the slab) Hit Undo Last to Undo last side. 0. The compression development length is calculated using Section 25. 5. Result. pre-mix 80 lb bags: $8 – $15 per bag. Next, find the coverage of the roll. 4. You'll also need 26 at 30 feet for a total of 780 linear feet. 2m3 x 7850 kg/m3 x 0. The weight of a concrete slab can be estimated by computing the volume of the slab and multiplying the volume (V) by the density of the concrete. 75 m in both the X and Y directions (Image 1). L = Length of the reinforcement. Number of Required Bars Formula = (Length of slab / spacing) + 1. SOLVED EXAMPLE FOR ANCHORAGE LENGTH Calculate the design tension anchorage length of X16mm bar (f yk = 460 N/mm 2,. (Imagine you are walking around the slab) Hit Undo Last to Undo last side. 3. In the two-way slab, the same practice as mentioned above should be followed for both directions. Step-2: Get The Slab Reinforcement Details. The compression development length is calculated using Section 25. Noncontact lapping length generally shorter than contact lapping length. If you want to combine rods of two diameters, there would. Calculate. Re-do Example 1 Re-do Example 2 Calculating the Weight of complicated Objects – Using Weight per Foot Method There is a very simple way to calculate. Calculators for structural engineers, construction professionals and steel building specifiers. When the dimensions of a slab, wall or other form exceed the length of a single stick of rebar, it is required to overlap and tie rebar pieces to create the added length. Besides the cost of concrete and materials, there are also labor costs. Any suggestions/comments are appreciated. Concrete grade and. REINFORCEMENT. . (b) A flat slab which is the same as a flat plate except the areas around the columns have increased thicknesses, called. Step 1: Determine the dimensions: Measure the length and width of the concrete slab in feet. An older reinforced concrete design calculator that computes required steel area for T-beams and 1-way slabs can be found here. Step-2: Get The Slab Reinforcement Details. Some regulations specify how much rebar is required to be poured into concrete. As per thumb Rule, the amount of steel quantity required for an RCC roof slab should be 1% of total volume of concrete slab. 5%. Volume of Concrete in slabs in cubic yards and meters. Rebar, or reinforcement bars, are used in concrete slabs to help increase their strength. For example in a slab of 6-inch depth, a rebar of 6/8 inch will be used. The Rebar and Concrete in a Slab calculator computes the total length and weight of rebar and the volume of concrete needed for a slab. The formulas calculate materials needed. Once you know how much rebar you need, place an order or request an estimate. 2: Repeat and continue to draw complete (closed) shape. (D) Depth of Slab (e. . Tensile stress. It requires input values for the dimensions of the slab, the size and spacing of rebars, and other parameters, providing an estimate of the required rebar quantities. For example, if you’re calculating rebar for a slab, input the slab dimensions, reinforcement spacing, and desired rebar size. As a general rule, rebar should be spaced between 16 and 24 inches. This process is called lapping, and the. Thickness (inches) Result: Cubic Yard =. Rebar. Determine the Pad's Area. Click the button to calculate the volume of concrete and man-hours (not including mixing) needed for this job. Calculating The Rebar Spacing For A Concrete Slab. justcalc. Width (feet) width x12. The calculation of concrete cover takes into account the requirements for structural performance, fire resistance, and durability. 1—Introduction 11. Step-3: Study The Drawing. Effective depth d= Span / ( (L/d) Basic x modification factor) For obtaining modification factor, the percentage of steel for slab can be assumed from 0. Step 2: Calculate the area: Multiply the length by the width to find the area of the slab in square feet. Here are the in-depth steps for columns: Find the dimensions of your columns. The minimum concrete cover for rebar typically ranges from 25 mm (1 inch). For the day to day calculations of engineers, fischer offers an efficient way to design post. e. Input length, width and depth of the area. 2-inch slab; 2-inch chairs for a 4-inch slab; 21⁄ 2- i n c h chairs for a 41⁄ 2-inch slab and 3-inch chairs for a 5-inch slab. Lets take example of RCC Column, where reinforcement required is 2. Calculation of concrete cover for bond The minimum cover for bond c min,b is calculated in accordance with EN1992-1-1 §4. Whether you need stock rebar, fabricated rebar, or PJ’s Pre-Assembled Rebar Products, our rebar calculator can help you determine how much weight is in your job. 0⋅ Φ , where Φ is the diameter of the reinforcement bar (or equivalent diameter of. To get a more specific recommendation,. 2, Φ, is reduced to 0. Quantity Estimate for Reinforcement in Kg: Quantity Estimation of Reinforcement in Kg. Calculate and the answer is 0. Note that this calculation is the volume of your tubes only and does not account for any overflow or loss. This way, the concrete doesn’t receive as much stress . "Deign of Slabs-on-ground" ASCC Position. Calculate the volume of cubic yards needed to fill in a square or rectangular slab pour for flooring, walls & similar structures. Compute the cost per bag, cost per unit area, and the overall material costs. We first obtain the total factored bending moment to be carried out by the slab’s unitary width strip. The effective compressive strength of a column increases as it is confined by the slab, and the. The Length and Weight of Rebar in Concrete Slab calculator computes the total length and weight of rebar needed for one or more mats of rebar in a concrete slab. Finds how many rebars you need to create a reinforcement in the slab. Rebar must be placed at the center of or slightly above the center of the concrete slab —hence why it should be a certain thickness for best results. Step 1: Determine the dimensions: Measure the length and width of the concrete slab in feet. The weight of the concrete slab would then cause the cambered beam to deflect to a level plane at the speci-fied eleva t i o n . Added 54% extra mortar to convert wet volume into dry volume. Number of cubic yards = 64 cubic feet ÷ 27. INSTRUCTIONS: Choose units and enter the following: (r) Radius of Circular Slab (e. The registered design professional shall assign nonstructural concrete a freeze-thaw exposure class, as defined in ACI 318, based on the anticipated exposure of nonstructural concrete. The Rebar in a Circular Shaped Slab calculator estimates the total length and weight of reinforcement bars (rebar) needed for a circular shaped concrete slab. Concrete slabs on grade are a very common type of concrete construction. In order to simplify the analysis and to be able to use the superposition principle for evaluating the effect of load combinations, linear analysis is generally adopted even though concrete slabs normally have a pronounced non-linear response. It requires careful attention to detail and an understanding of the various factors that can affect the outcome. For reinforcement bars the minimum cover for bond is calculated in accordance with EN1992-1-1 Table 4. Stretch a string between two screws installed at the edge of both ends of the form boards. The quantities for Removal of Concrete and Class B Concrete are 21. If you’re wondering how many bar chairs you need per m2 for a sheet of mesh, generally, a minimum of 22 bar chairs per sheet of 6m x 2. Slabs are defined as two-way slabs when the ratio of long-to-short sides is less than 2. 9 of ACI 318-14 or Section 12. Next, you must decide how many layers of rebar are needed for the specific application. The size and type of rebar used in concrete slab footings will depend on the specific requirements of your project, including the size of the slab, the load it will support, and local building codes. Length (feet) length x12. 40 to $1. For compatibility with older ACI codes, Ψr is taken as 1. 5 feet. Weight (lbs/ft) = (Diameter^2 / 162. coverage = 250 sq ft. They seem to have that. 3 of ACI 318-11 or older. e. The total quantity of steel required in the given slab is 565. 0. Convert your longitude estimation into inches: 15 x 12 = 180. 1) Measure all dimensions (Length, width, and thickness) of concrete slab in feet, 2) Multiply length of slab by width and by thickness to determine cubic footage. It is used mostly in a combination of these two in concrete slabs. 2 CY for Site B when taken to the tenth of a cubic yard (0. How much rebar is needed for concrete slab? Generally, one stick of rebar. Compute the cost per bag, cost per unit area, and the overall material costs. Step 4. Provide the required spacing and diameter of the rebar. Columns that support flat plate slabs and columns that are supported by footings are the most common examples. Calculate rebar length for the slab — RL — using the formula: RL = SL – 0. of Main bars = (3000)/150 + 1. 87 (round up to 13) Add one rebar to your result: 13 + 1 = 14. INSTRUCTIONS: Choose units and enter the following: Rebar Grid - One Mat (L) Length of Slab (W) Width of Slab (D) Depth of Slab (rS) Size of Rebar (none, 2-11,14,18) (i) Rebar Inset from the edge of the slab. A 4” concrete slab can easily support 125 lbs. Calculate volume of concrete i. You’ll find that #3, #4, and #5 size rebar is most commonly found in home reno stores and used in footings for homes and other domestic structures. Now the 6% of the above value = (2/100)X12. Initially, they mostly used in masonry structures to enhance their capacity. Plain and untreated steel rebar costs $0. 3) Multiply the total cubic feet needed by the 0. Rebar is typically calculated at a rate of 1 for every 8 inches of footing width. Concrete slab resting o n grade containing minimal distributed st eel, usually of weld ed wire fabric (WWF), for the purpose of limiti ng crack width due to shrinkage and tempera-ture change. D. The Rebar in a Circular Shaped Slab calculator estimates the total length and weight of reinforcement bars (rebar) needed for a circular shaped concrete slab. No. Check it against the factored shear load on the slab, 0. These are known as rebar sticks. 075kN m. 26897 kg. Development Length is usually specified in the drawings, but if not then you can calculate it as, D. A 4” concrete slab can easily support 125 lbs. The net result is a more accurate and less. The first step is to determine how much rebar is required to support your foundation. 1. Enter the slab dimensions, desired rebar spacing and the spacing from the edge to quickly find how to lay out the rebar grid. Concrete Slab Volume Estimator Calculator Estimate the require concrete volume to fill the width, height and depth given. To calculate concrete for slabs, add ¼ of an inch to the slab thickness, assuming that the job is evenly graded to the proper depth. 360R-44 12. 0As(σ sd /f yd), with As = area of one lapped bar. That is Ce = Cn + dia/2. com The online Concrete Rebar calculations assists civil engineers how much Rebar for a concrete slab required. Concrete slabs thinner than 4” typically don’t need rebar. To calculate Total Area of a multi sided slab, first divide the shape into rectangles or squares. I am looking for information to calculate what is my required dowel rebar size and embedment length to dowel into a reinforced concrete slab? I know ACI has provisions for doweling a concrete column/pedestal into a footing, but I am trying to find something regarding doweling CMU rebar into a concrete slab. For heavy-duty purposes. Footings are especially important in areas with troublesome soils. Concrete is sold in cubic yards (27 square feet), so you will need to multiply your square footage from Step 1 by the depth of. Total rebar length 60 m. Once you know how much rebar you need, place an order or request an estimate. area = 25′ × 25′. Layout of Rebar for Concrete Slabs to Estimate the Quantity of Rebar in Slab. One Way Slab Bar Bending Schedule Calculation. 2: Repeat and continue to draw complete (closed) shape. Our calculator will instantly calculate the quantity of rebar required. Convert your longitude measurement into inches: 15 feet x 12 inches per foot = 180 inches. It has a foot print of four tires about 10 inches by 10 inches time 4. Additionally, additional bars should be placed 12” apart along all. Convert between weight and volume measurements used with concrete. 2 MPa) for Class F0; 3,000 psi (20. . Steel weight required for above slab = 3 x 7850 x 0. If you can get 20' long bars the total length of your slab can be 20'. Concrete - Water to Cement Ratios. g. 60 per square foot, including materials and labor. In order to calculate this, you need to input the length and width. With this calculator, you’re trying to calculate the dimensions of your rebar grid (length and width). When calculating V c, Equation a) for λ= 1 and a longitudinal reinforcement ratio ρ w < 1. Online Concrete Slab on Grade Analysis Calculator For Slab Subjected to Interior Concentrated Post or Wheel Loading Assuming Slab is Reinforced for Shrinkage and Temperature Only. For example, if the area is 10 feet long and 6 feet wide, the square footage is 60 feet. The construction of footings is best. NOTE: this calculator was updated on 16 Feb 2022 to accommodate the inset of rebar placement from the edge of the slab. 2. You’ll consequently require 14 lengths of rebar. After that, the following steps will be taken to compute steel quantity. Enhancement of the strength of the. It is generally accepted that rebar should have minimum 6″ clear cover from all edges, corners, and other forms of reinforcement. a weak concrete has a compression. So, Mass = Density X Volume. 3. The exact distance from the reinforced concrete slab’s edge to the rebar should depend on the specific application, size, and thickness of the slab. When you swing on a rope swing and jump into a swimming hole, you exert tensile stress on the rope. Based on the ACI 318-99 version "REBARS. 01942 lbs/ft. Building a concrete slab foundation costs $5 to $14 per square foot or $4,000 to $33,600 total on average. Multiply the measurements together to calculate the square footage of the area. Rebar, or reinforcing bar, is used in many masonry and concrete projects to reinforce slabs and structures. 4. 125 = 12. Figure 14 represents the plate’s local axes. 2. The gauge, or diameter, of the rebar is selected based on the purpose and the load-bearing requirements of the structure: For standard residential concrete slabs, #3 (3/8 inch diameter) to #5 (5/8 inch diameter) rebar is typically used. (default is one). 5 units. Total cost 1065. 2. You'll see both cubic yards and cubic meters in the answer area. 56% results in the greater concrete shear resistance. Weight of one m of rebar is 0. ( i) Inset distance from the side of the slab to the rebar grid (default of 3″). Rebar Development Length Calculator is a web application that supports the design of post-installed rebar in concrete applications by calculating the necessary tension and compression development lengths required in accordance with ACI 318-19 / ACI 318-14. The columns are modeled as elastic nodal supports by determining the spring stiffness. 01942 pounds per linear foot. 5 kN/m2 (153 kg/m2) in domestic buildings to approximately 1 0 kN/m2 (1053 kg/m2) in heavy industrial areas. Description. If your footings are 16 inches thick, multiply 16 by 80. Inches. (e) Crack Control According to. 1 m)Rebar Grid Calculator. xls" workbook. ( RL) Length of the pre-cut rebar sticks being used to. 666 feet. As you. FIrst, find number of rods required for main reinforcement and distribution. Mass / Volume Conversion. below grade) to have R-10 vertical insulation at the slab perimeter, extending downward from the top of the slab to a depth of at least 2 ft. The most common lengths of pre-cut rebar in the United States are 20`, 40' and 60'. This calculator finds rebar sizes and spacing for beams, girders, and 1-way slabs for a particular type of reinforced concrete floor system consisting of a regular grid of columns supporting a hierarchical arrangement of girders, beams, and 1-way slabs for which. 3. INSTRUCTIONS: Choose units and enter the following: (r) Radius of Circular Slab (e. Chapter 11—Fiber-reinforced concrete slabs-on-ground, p. For column = 2. The amount of rebar needed for a slab will depend on the size of the slab and the particular requirements of the project. 2. Using bonded rebar in a concrete slab is a common method to increase the punching shear strength of the RC slab-column systems [8, 9].