What size beam do I need for a 18 foot span | what size wood beam do I need for a 18 foot span | RCC beam size for 18 feet span | LVL beam size for a 18 foot span | Glulam beam size for 18 feet span | RSJ beam size for 18 feet span | steel beam size for 18 feet span | how big of a beam do i need to span 18 feet.
Beam is generally made of RCC ( reinforced cement concrete) concrete providing with reinforcement Steel. It is also made of timber or wood, RSJ beam (rolled steel joist), steel, LVL ( laminate veneer lumber), Glulam (Glued laminated timber).
Beam is load bearing structure and flexural member of concrete that vertical transfer all the incoming dead load, live load and self load of rcc roof slab to the column via column beam joint through development length of structure element.
Size of beam generally depending on span or distance between two support, types of beam structure, species of wood, width of house 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.
RCC 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 18 foot span
RCC 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.
Using thumb rule, for a 18 foot span, you will need atleast 12″×15″ size of RCC beam for 1 to 2 story building and 12×18″ for 3 story building in which 18″ is the depth of the beam and 12″ is width 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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There is various method to deciding beam size its width and depth of beam. 1) IS 456:2000 and 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).
2) Thumb rule method:
You can also calculate the size and depth of the beam according to thumb rule method mention: 1 foot (span of the beam) = 1 inch (depth of beam), If the span is of the beam is 15 feet, then the depth of the beam will be 15 inches and beam width 15/1.5=10″, taking as 12″.
What size RCC beam for 18 feet span
Thumb rule for sizing RCC beam: as per general experience and thumb rule, to calculate the required and necessary depth of beam, divide the span length in inches by 20 such as span length in inches/ depth = 20 for primary rcc beam. For example: for 18 feet span depth of beam = (18×12) / 20 = 12″ minimum.
For a 18 foot span, you will need atleast 12″×15″ size of RCC beam for 1 to 2 story building and 12″×18″ for 3 story building in which 18″ is the depth of the beam and 12″ is width 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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How big of a beam do i need to span 18 feet?
You will need atleast 12″×18″ size of rcc big beam to span 18 feet. For a 20 foot span, using thumb rule, size of rcc beam 12″×18″ used for 2-3 storey residential building, 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.
What size Steel beam for a 18 foot span
Thumb rule for sizing steel beam: as per general experience and thumb rule, to calculate the required and necessary depth of beam, divide the span length in mm by 18 to 20 such as span length in mm/ depth = 18 to 20 for primary beam and for secondary beam span length to depth ratio is about 15 to 18. For example, 18 feet or 5400mm span, depth of beam = 5400/ 20 = 300mm, rounding to ISMB300.
For a 18 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″) or W12 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.
What size Wood beam for a 18 foot span
For a 18 foot span, size of wood beam should be 4- 2×16, or 8″×16″ or 4 nailed 2×16 which used for residential building or projects or construction in which depth of section of beam is 400mm (16″) and width of beam is 140 mm or 6″. Thus, 4- 2×16, or 8″×16″ or 4 nailed 2×16 size of wood beam most suitable to span 18 feet.
What size LVL beam for a 18 foot span
For a 18 foot span, size of LVL beam should be 10- 12 inches deep and 3 1/2 inches wide, thus you need something like a 10- 12″ LVL (Laminated vanner lumber) to span upto 18 feet used for residential building or projects. Thus for span upto 18 feet, generally you need atleast 3 1/2× 11 1/4 standard size of LVL beam on normal weight condition which providing great stability for your projects.
What size Glulam beam for a 18 foot span
For a 18 foot span, size of Glulam beam should be 10- 12 inches deep and 3 1/2 inches wide, thus you need something like a 10- 12″ Glulam (Glued laminated timber) to span upto 18 feet used for residential building or projects. Thus for span upto 18 feet, generally you need atleast 3 1/2″× 11 1/4″ standard size of Glulam beam on normal weight condition which providing great stability for your projects.
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Conclusions:
You will need atleast 12″×18″ size of rcc beam, or 4- 2×16 or 4 nailed 2×16 size wood beam, or 3 1/2″× 11 1/4″ size LVL beam, or UB 300 ×140 (12″×6″) or W12 size steel beam, or 3 1/2″× 11 1/4″ size Glulam beam for a 18 foot span.