Roof Poding Deflection Check

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Roof poding deflection check.

K2 1 using a spacing s 1 0 ft. In roof systems that are essentially flat provisions must be made to support ponding water. For your reference i have attached staad files. It should be handled with eq.

Ponding is a progressive event. 5 15 ponding on roofs. A flat roof for commercial businesses make a lot of sense for a host of reasons. Fijneman eindhoven university of technology the netherlands faculty of architecture building and planning department for structural design and construction technology sdct ponding of rainwater is a special load case that can lead to roof collapse.

For a flat or near flat roof it is necessary that the roof framing be sufficiently stiff to prevent ponding of water. If roof decking is the secondary system directly supported by the primary members i e no secondary beams joists etc. Structural failure due to long term effects of ponding water. The more water on the roof the more deflection you get which means that even more water can be retained which leads to more deflection etc.

The level roof surface is utilized for air handling units gas vents skylights and other mechanical equipment. A flat roof serves as a superstructure from which to attach joists and suspend piping hvac ductwork and lighting systems from. Fast check for ponding engineering journal american institute of steel construction vol. When there is the possibility of water ponding which may cause excessive loads and additional progressive deflection each component of the roof system including decking purlins beams girders or other principal structural supports should be designed accordingly.

2 where i made second file that having flat roof member i e no slope at roof member in which staad shows this member pass in deflection check. See the table below. Structural design for ponding of rainwater on roof structures f. 1 sloped roof having angle of 5 7 degree aprox in staad the sloped roof member shows failure in defection check.

For example the allowable deflection of a 12ft span floor joist with plaster l 360 is 0 4 12ft divided by 360. Primary member stress fo is the bending stress in the primary member due to the supported loading neglecting ponding. Note it gives the allowable deflection based on a fractional span quantity so a larger denominator will yield less deflection.