![]() Tile roof rafters are often applied in civil works such as houses, shared living houses, religious belief constructions,… 2.3 Wooden roof rafters In addition, when designing, it is necessary to focus on the distance between the tile roof rafters to ensure safety. Tile is a material which is heavier than corrugated steel, so the tile roof rafter frame needs to have a solid steel structure. In terms of shape, the corrugated steel roof rafter combined with the system of columns in the steel frame creates gable frames, single-roof trusses, curved roof trusses, multi-space trusses, roof systems,… 2.2 Tile roof rafters In addition, corrugated steel roof rafters often include a system of border gutters, central gutters and decorative details, substructures such as roof frills, gutter frills, fascia, roof. ![]() Reinforcing accessories: bracing rods, bracing cables, galvanized steel bolts.Roof purlin: has the function of linking between corrugated steel roofs and trusses, usually made from cold rolled galvanized steel.Trusses, struts: have the main bearing function and distribute the roof weight down to the pillars evenly.The corrugated steel roof rafter consists of the main parts: Prefabricated steel rafters combined with corrugated steel roofing can be the synthetic rafter or the space rafter depending on the requirements of each building. Here are some common rafter types based on the type of roofing material, customers can refer to: 2.1 Steel Frame Prefabricated Corrugated Steel Roofing rafter ![]() Types of common rafter nowadaysĬurrently, there are many rafter types in the market depending on the needs of customers. Please consult with a Registered Professional Engineer for actual designs.Pebsteel’s PebHybrid rafter optimizes space efficiently 2. If you were able to somehow acquire 2850f Machine Stress Rated 2×4 with a E value of 2300000 psi (very high grade material used by some truss manufacturers) spacing could be 18 inches on center.Īgain – remember these equations are just for checking for bending due to a minimal snow load, wind conditions may dictate. If you were to reduce spacing to say 11 inches on center then flatwise 2×4 #2 Southern Pine with a 20 psf roof snow load would be adequate. These calculations are based upon purlins every 24 inches on center. S = 21.217 psf using the appropriate load calculated aboveį b = 21.217 psf * 24″ / 12 in. Roof steel dead load = 0.63 psf steel American Building Components catalogueį b ‘ = F b * C D * C M * C t * C L * C F * C fu * C i * C rĬ M = 1 because purlins are protected from moisture by roofį b ‘ = 1100 psi * 1.15 * 1 * 1 * 1 * 1 * 1.1 * 1 * 1.15į b : bending stress from snow/dead loadsį b = (purlin_dead_load + S) * spacing / 12 * cos(θ) / 12 * (s f * 12 – 3) 2 / 8 * 6 / b / d 2 * cos(θ) ROOF PURLIN DESIGN – Main Building (Balanced snow load) ![]() In high wind areas, wind will fail purlins (or their connections) rather than snow! I have condensed calculations down to just bending and deflection and will use minimum snow loads in this example: When it comes to designing whether a roof purlin can achieve a given span, it takes a lot of calculations – both for live or snow loads, as well as wind loads. This is just one of many reasons why post frame buildings should be designed by a Registered Professional Engineer. Now I am relatively certain this building’s roof purlins were supposed to be 2×8 on edge between trusses – however for some obscure reason, they got installed flat wise! I am unsure as to how they were even able to get roofing installed without falling through. It was for a garage and sidewall columns and single roof trusses were placed every eight feet. “Can you 2 by 4 flat on an 8 foot span Truss”Ī few years ago, one of my neighbors bought a pole building kit from someone other than Hansen Pole Buildings. Chances are good if you have to ask a structural design question, then you are in over your head. ![]()
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