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Purlins Meet The Structural Requirements


Purlin force characteristics

1, purlins are distributed along the length of the roof of the horizontal components, located on the main rafters, support the secondary rafters. Ancient houses used to stir up rafters, made of roof of the crossbar, is one of the main building blocks, also known as truss

In the slope of the roof is often placed on the roof or inclined beam, which on the plate and waterproof layer, as the water along the dependent components.

Modern steel structure construction generally C / Z steel, Purlin H-shaped steel as the purlins, have a better tolerance

2, purlin classification

Steel structure of the internal support components, high-strength galvanized steel sheet by precision machining cold-rolled into C and Z-shaped steel.

Purlin with the main purlin and sub-purlin of the points.

The main purlins are connected to the roof and the external structure of the pillars. The purlins are used to connect the roof panels and the outer wall panels to the foundation structure. Purlin The primary purlins are the main structural components commonly used in modern steel structure design.

Some construction measures of purlins

When the purlins span greater than 4m, should be in the purlin between the cross-set position. When the purlins span 6m, should be in the purlin span three points to set a bar.

The effect of the pull is to prevent the purlin from being laterally deformed and twisted and providing an intermediate fulcrum in the x-axis direction. Purlin The force of the intermediate fulcrum needs to be transmitted to a larger member. For this purpose, it is necessary to provide a stay and a rigid stay at the roof or cornice.

When the wind suction exceeds the permanent load on the roof, the lateral force points to the opposite. At this time Z-shaped steel sandbar of the oblique bar need to be set in the roof, Purlin while the curling tank purlins are required to be located in the eaves.

Therefore, in order to take into account the two cases, in the wind load area or in the eaves and roof are set at the oblique bar, or the cross bar and the stay are made both tensile and pressure bearing rigid rod The

Strip is usually made of round bar, round bar diameter should not be less than 10mm. Purlin Round bar can be set in the purlin from the flange on the flange 1/3 height range.

When the wind suction under the purlin under the flange pressure, the roof should be directly with the self-tapping screw connected with the purlin, pull the bar should be located in the vicinity of the lower flange.

In order to take into account both windless and windy circumstances, can be in the upper and lower flanges near the layout.

1, according to the characteristics of force, purlin should be two-way bending components for internal force calculation and cross-section design.

2, purlin In the internal force analysis, the internal force calculation and the arrangement of the bar, when the layout of one or two pull bar, under the action of horizontal load qx by two or three spans continuous beam calculation.

3. Strip arrangement should take into account the impact of wind load, according to the actual force to calculate the strip section, Purlin and meet the structural requirements.

What are the design features of purlin?

(1) purlin for the thin-walled components, in the state of the composition of the plate may lose the local stability and produce buckling, but after the buckling can still carry (using the film effect, that is, the tension field). Design of the use of its flexural strength, the general use of effective cross-section method for strength calculation.

(2) purlins of the overall stability calculation is divided into two cases:

a. Under the action of wind pressure, the general pressure type steel plate (provided that there are enough anti-shear pieces) and the purlin strip provided in the compression zone can act as lateral restraint.

b. Under the action of wind suction, Purlin the lower flange is pressed (the purlin is continuously set under the action of wind pressure). The effect of the tension on the flange is considered to be the effect of the elastic foundation beam. The cross section and the lateral bending effect are equivalent to the lateral load acting on the lower flange to simplify the calculation. Structural requirements can also be used, Purlin such as setting the brace.

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