What size beam do I need for a 20 foot span? Hi guys in this article we know about beam size for 20 foot span | how big of a beam do i need to span 20 feet.
Beam is generally made of concrete providing with reinforcement Steel. It is load bearing structure and flexural member of concrete that vertical transfer all the incoming dead load,live load and self load of rcc slab to the column via column beam joint through development length of structure element.
Size of beam generally depending on span between two support and all the load acting on it. Beam is structural member subjected to flexural stresses and shear forces . The size of the beam (width and depth of beam) are governed by the different type of shear forces and stresses.
When the beam is subjected to loading the bending moment is developed and the moment carrying capacity of the beam depends mainly on the depth of the beam.
How the size of beam could be decided? In case of RCC beams an appropriate width of the beam is assumed on the basis of experience , the magnitude of maximum bending moment and in some cases on the basis of the width of the wall present below the beam. This width of the should be sufficient to provide rebars with sufficient side cover and spacing between the bars. After assuming the width the effective depth of the beam is calculated based on the bending moment and then the overall depth of the beam is determined by adding effective cover to the effective depth calculated.
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Beam is different types like cantilever beam, continuous beam, simply supported beam, fixed beam, overhanging beam,lintel beam, primary beam and secondary beam. A cantilever beam is a rigid structural element that extends horizontally,one end is free and is supported at only one end. Simply supported beam is supported at two end and continuous beam is supported by more than two support end.
What size beam do I need for a 20 foot span?
Beam is provided with the top bar which experience compression and bottom bar which experiences tension. Mainly tension bar encounter the bending moment and stirrup of which are provided to incounter the shear forces.
We can always take the standard size of the rcc concrete beam size at least 230mm x 230mm (9” x 9”) in which width and depth of beam is 230mm (9″). The depth of the beam increases or decreases according to their span and applied load on the beam. Now there is remarkable question “what size beam do i need for a 20 foot span?”.
There is various method to deciding beam size its width and depth of beam. 1) IS 456:2000, 2) Thumb rule method
1) According to IS 456:2000 for designing of minimum size of RCC column for 2- 3 storey building its recommendation is:- a) for cantilever beam span to effective depth ratio is 7 (span/effective depth=7), for simply supported beam span to effective depth ratio is 20 (span/effective depth=20) and for continuous beam span to effective depth ratio is 26 ((span/effective depth=26).
Simply supported beam size for 20 foot span:- for simply supported beam span to effective depth ratio is 20 (span/effective depth=20), given span 20 foot, effective depth =20 ×12″/20=12″, dia of bar=16mm, clear cover of 1″, so overall depth= effective depth+clear cover +1/2dia of bar = 12″+1″+0.3″=13.3″, taking round figure beam depth=15″. Width of beam = D/1.5=15″/1.5=10″, in general it is taken as 12″ inch.
What size beam do i need for a 20 foot span? For 20 foot span, size of simply supported beam for 2-3 storey residential building, using thumb rule, is about 12″×15″ in which beam width is 12″ and beam depth is 15″ providing with 2nos of 12mm bar at top, 2nos of 16mm bar at bottom and 2nos of 12mm crank bar of Fe500 with stirrup T8@6″C/C and M20 grade of concrete ratio (1:1.5:3) with clear cover 25mm.
Continuous beam size for 20 foot span:- for continuous beam span to effective depth ratio is 26 (span/effective depth=26), given span 20 foot, effective depth =20 ×12″/26=9.23″, dia of bar=16mm, clear cover of 1″, so overall depth= effective depth+clear cover +1/2dia of bar = 9.23″+1″+0.3″=10.53″, taking round figure beam depth=12″. Width of beam = D/1.5=12″/1.5=8″, in general width of beam is taking as 9 inch.
For 20 foot span, size of continuous beam for 2-3 storey residential building, using thumb rule, is about 9″×12″ in which beam width is 9″ and beam depth is 12″ providing with 2nos of 12mm bar at top, 2nos of 16mm bar at bottom and 2nos of 12mm crank bar of Fe500 with stirrup T8@6″C/C and M20 grade of concrete ratio (1:1.5:3) with clear cover 25mm.
How big of a beam do i need to span 20 feet? For 20 foot span, size of beam for 2-3 storey residential building, using thumb rule, for simply supported beam, it could be 12″×15″ and for continuous beam,it could be 9″×12″, using steel grade of Fe500 with stirrup T8@6″C/C and M20 grade of concrete ratio (1:1.5:3) with clear cover 25mm.
2) Thumb rule method:
You can also calculate the size and depth of the beam according to thumb rule method mention below
1 foot (span of the beam) = 1Inch (depth of beam)
If the span of the beam is 20 feet, then the depth of the beam will be 20 inches, beam depth taken as 18″ and beam width 20/1.5=13.33″, taking as 12″.
What size beam do I need for a 20 foot span?For 20 foot span, size of beam for 2-3 storey residential building, using thumb rule,1 foot (span of the beam) = 1inch (depth of beam), is about 12″×18″ in which beam width is 12″ and beam depth is 18″ providing with 2nos of 12mm bar at top, 2nos of 16mm bar at bottom and 2nos of 12mm crank bar of Fe500 with stirrup T8@6″C/C and M20 grade of concrete ratio (1:1.5:3) with clear cover 25mm.
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Steel beam size for a 20 foot span
As per general thumb rule, for a 20 foot span size of steel beam or universal beam or w beam or I beam or UB’s or hot rolled section should be ISMB 300 or UB 300×140 (12″×6″) used for residential building or projects or construction in which depth of section of beam is 300mm (12″) and width of flange or width of beam is 140mm. This is standard and most suitable size of steel beam used for a 20 foot span under normal load condition. Mathematical calculation such as depth of steel beam = 6× 1000mm/20 = 300mm or 12″ and width of beam = depth/2 = 300mm/2 = 150mm, but 140mm flange width is used.
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Wood beam size for a 20 foot span
As per general thumb rule, for a 20 foot span, size of wood beam or lumber joist should be 2×14 which placed at 16″ apart from centre used for residential building or projects or construction in which depth of section of beam is 350mm (14″) and width of beam is 50 mm or 2″. In general terms, joist or beam which spaced 16 inches apart on Centre can span 1.5 times in feet their depth in inches. A 2×14 can span upto 20 feet.
What size beam to span 20 ft
As per general thumb rule and guidelines, a 4 nailed 2×16 or 4-2×16 or 8×16 size of wood beam can allow to span 20 ft. Thus, for a 20 foot span, you will need atleast 4-2×16 or 8×16 size of wood beam. For a 20-foot spans, the wood beam has to be at least 16 inches in depth and 8″ in width (4-2×16) used for residential building or projects.
LVL beam size for a 20 foot span
As per general thumb rule, for a 20 foot span, size of LVL beam or GLULAM should be 10-12 inches deep and 3 inches wide, thus you need something like a 10-12″ GLULAM or LVL to span upto 20 feet used for residential building or projects. Thus for span upto 20 feet, generally you need 3 × 11 1/4 standard size of LVL beam on normal weight condition which providing great stability for your projects.