And this is why the Cantilever beam system is far more efficient than the simple two-joist span.Īlso, the beam usually has less stress because it uses a shorter span length. Note that you will only find a Cantilever beam for up to 20 feet.

And then, you should take the round figure beam depth = 12″.Īt this point, you will be able to derive the width of the beam, which in generality will be 9 inches. The overall depth will be = effective depth + clear cover + 1/2dia of bar = 9.23″ + 1″ + 0.3″ = 10.53″. Using a Continuous beam in dealing with a 20-foot span, you should arrive at an effective depth = 20 ×12″/26 = 9.23″, dia of bar 16mm, and a clear cover of 1”. Here, the continuous beam span to effective depth ratio is 26 (span/ effective depth = 26). So, in general, you can take it as 12 inches. With that, you can then attain the width of the beam = D/1.5 = 15″/1.5 = 10″. And then, you should include the round figure beam depth = 15. Therefore, the overall depth will be effective depth + clear cover + ½ dia of bar = 12″ + 1″ + 0.3″ = 13.3″. This recommendation shows a simply supported beam span with an effective depth ratio of 20 (span/ effective depth = 20).įor a 20-foot span, you need the effective depth = 20×12”/26 = 9.23”, a clear cover of 1”, dia bar of 16mm. Continuous beam span to effective depth ratio is 26 (span/ effective depth = 26).A Simply supported beam span to effective depth ratio is 20 (span/ effective depth = 20).Cantilever beam span to effective depth ratio is 7 (span/ effective depth = 7).However, you need to know that you can use various methods to determine a beam’s size, width, and depth.Īccording to this method, when designing a minimum RCC column for 2 to 3-story buildings, there are three beam recommendations Hence, this is why I am giving you the correct size of a flitch beam that will span 20 feet in the first paragraph of this subheading. If I try using a structural engineering formula to explain the replacement of the 6×18 beam, it will become very complex and confusing for you. For instance, you make use of steel plates which you will then bolt together with wood planks. Today you don’t commonly see it because it is labor and material intensive. This combination allows a flitch beam to carry much more weight and will do this without necessarily increasing the wood plank’s depth. But thanks to the ½-inch plate, it can now support 10,971 pounds.īefore the era where we now use glue-laminated wood beams and rolled steel beams, we used the flitch beam, just like a sandwich of two wood planks with a steel plate in the middle. Note also that at 20 feet span, these two 2×12 beams with an F b of 1400 psi will be only good at supporting 3,090 pounds. It will sum up to a total of 10,971 pounds of weight. In the case of a flitch beam, to span 20 feet, you need two 2×12 beams with a ½-inch steel plate bolted together in the middle.

Lvl beam span table ridge