A Top and Bottom Chord

The top and bottom chord of Open joist purlin is made of cold form thin wall plate with patened appearance design of “Ω”. The width of chord is 150mm, and height 60mm. The shape ensures the chords with certain strength out plane as well as good rigidity in plane. The additional straight webs won't be needed.

The top chord edges will extend 40mm horizontally. The two 40mm edge extensions supply rigidity out plane as well as good interface connecting with roof sheet. The unique design of chords and accessories can meet any roof slope requirements.?

Connecting to Standing Seam Roof Sheet: The specially designed splice plate will be provided and inclined according to roof slope in result of movable pedestal fixer for roof sheet at most reasonable location.

Connecting to Small Slope Color Sheet with Screw: For color sheet less than 10% slope, the edge extension of top chord can serve as the pedestal for tighten screw.
Connecting to Big Slope Color Sheet with Screw: For color sheet more than 10%, a secondary purlin specially manufactured subject to roof slope will be added on the top chord before erecting of joist purlin.

B Welding Detail of Joist Purlin

The web of Open joist purlin is high frequency welding thin wall steel pipe both ends of which are rolled and cut diagonally according to web size. The fillet welding by CO2 gas shield is implemented between the web and chords to ensure the joist strength as well as a neat apperance of it.

If bigger uniform load is implemented on joist purlin, the straight webs can be added to reduce the length of top chord involved in calculation in plane.

C End Supports of Joist Purlin

For Open joist purlin is mainly used in the roof system, it must be worked out how to lay the gutter in joist purlin roof. In Open roof system, all the joist purlins will be raised up 200-300mm normally on end supports to ensure the gutter placement.

D End web of Joist Purlin

For joist purlin is fixed on the main frame by simple support style, the end webs are bearing the maximum tensile strength among webs. The end web is made of flat steel and the upper part of it put into the support to ensure its strength as well as passing the support reaction directly to the bottom chord in a result of eliminating the moment at end of top chord and acquiring more reasonable joist calculation.

E Free Access in Webs for Equipments' Cable or Pipe

The Height of Open joist purlin will be utilized effectively. For the space among the webs of joist purlin, certain equipments' pipe or cable can be put through freely in the webs in result of saving the indoor clear height. Meanwhile, because the bottom chord of joist purlin is made of cold-formed steel, it can be severed as the pipe rack for the equipments to save more investment.

F Sag Bracing between Joist Purlin

Every piece of Open joist purlin will be equipped with a splice plate which will make it easy to install the joist purlin sag bracing normally placed by horizontal arrangement. But between joist purlins at eave and ridge, the sag bracing should be laid by cross type as showed in left diagram.

The sag bracing's quantity between each purlin span relates to the span, clear height and load-bearing condition of joist purlin. It is recommended to set three to four rows of sag bracing in each purlin span.?

G Assembly of Joist Purlin's Chords and Webs

The Open joist purlin can be designed for the maximum span of 25 meters which will be so big that it cost much trouble to deliver. In order to solve such problems, the joist purlin longer than 12 meters will be fabricated by two parts respectively. Several high strength bolts will be enough for assembling the joist purlins at site.

This unique design can also make it very easy for you to deliver the joist purlins at site. Just taking consider of it that the 20 meters long joist purlin is delivered to hoist location separately only by labor for ground assembly. Thus you can not only save the time but strengthen greatly the erection security.?