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Construction Requirements Of Purlin

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Design features of Purlin

(1) Purlin is a thin-walled member, which may lose local stability and produce buckling in the force state, but can still be loaded after buckling (using the film effect, i.e. the tension field). In the design, the strength is calculated by using the effective section method.

(2) The overall stability calculation of purlin is divided into two kinds of situations:

A. Purlin Under the action of the wind pressure, the general pressure steel plate (the condition is sufficient shear parts) and the compression zone set by the Purlin tension bar can play a lateral restraint role.

B. Under the action of wind suction, the lower flange under pressure (the continuous setting of purlin under the action of wind pressure is similar), Purlin the force state similar to the elastic Foundation beam, according to the research, it is considered that the constraint of the flange to the elastic Foundation beam can be calculated by the compression bar of the flexible foundation beam, and the torsion of the section and the lateral bending effect are equivalent to the lateral loads acting on the lower flange to simplify the calculation. Purlin can also be used in construction requirements, such as setting the corner.

Purlin is a purlin roof system and wall structure of the main components, Purlin because of its large area of use, so the proportion of steel in the housing structure is also larger, so should pay attention to the design of a reasonable choice of purlin form, and pay attention to the layout of Purlin. Experience shows that one of the effective measures to save the steel quantity of purlin is to enlarge the spacing of purlin and reduce the weight of roofing materials. In terms of the cross-section of Purlin, purlin are generally divided into real abdomen type, hollow type and truss type Purlin.

The sectional form of the commonly used real abdominal purlin:

(1) Real belly purlin

The cross height ratio of the solid-bellied Purlin is generally taken $number, Purlin and the cross-sectional width can be determined by the section height h and the selected section steel specification. Commonly used are:

1 Steel Purlin

Ordinary channel steel and light groove steel commonly used as purlin, because of the thickness of ordinary channel steel, more for the deflection control design, Purlin the strength can not be fully played, so it has a large quantity of steel defects. The use of light channel steel as purlin can improve these drawbacks, but it is not ideal.

2 h-shaped steel purlin

High-frequency welded H-shaped steel is a light steel, with thin webs, good bending stiffness, the direction of the two axis of inertia is closer, flange plate straight, easy to connect and so on.

3. Rolled Edge Groove steel purlin. Rolled Edge Groove Steel, also known as C-shaped steel, is a thin-walled steel, used in the use of Purlin good interchangeability, with steel.

4 roll Edge Z-shaped steel purlin. The z-shape of the Z-shape and the diagonal roll-edge are two kinds, which are suitable for the i≥1/3 of the roof slope, Purlin at which time the action line of the roof load is close to the bent heart of the section. The stiffness of the main plane x-axis of the Z-shaped steel purlin is large and the amount of steel is saved.

5 Angle Steel Purlin. Angle Steel purlin is composed of single angle steel, easy to draw, but stiffness is poor, suitable for span, purlin distance and load are smaller occasions.

6 steel Purlin of combined channel. Purlin Combined channel steel purlin, welded from two angle steel, with more than ordinary channel steel, but the welding workload is large, suitable for the occasion of l≤4m.

7) combination Z-shaped steel purlin. The composite Z-shaped steel purlin, welded by two pieces of angle steel, is suitable for the occasion of Roof slope I≥1/3, when it is more reasonable than the channel steel.

(2) Hollow type Purlin

The upper and lower chord of the hollow purlin is composed of angle steel, the middle is connected with the connecting plate, because of its empty-stomach structure, the section inertia moment and radius big, thus can make full use of the steel strength, achieves saves the steel the goal. Purlin One of the advantages of the hollow-type purlin is that it can make full use of small angle steel (upper, chord) and thin steel plate (the plate), the disadvantage is that the spacing is more dense, splicing and welding workload, and the other kind of purlin lateral stiffness is poor, so the application of a certain limit.


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