GB/T 39794.2-2021Test method for wind uplift resistance of mental roof—Part 2: Dynamic pressure method (English PDF)

Foreword

GB/T 39794 "Test Method for Wind-Resistant Performance of Metal Roofing" is divided into 2 parts.

---Part 1: Static pressure method;

---Part 2: Dynamic pressure method. This part is Part 2 of GB/T 39794.

This section was drafted in accordance with the rules given in GB/T 1.1-2009.

1 Scope

This part of GB/T 39794 specifies the terms and definitions, detection principles, and inspection methods of the dynamic pressure detection method for the wind resistance of metal roofs. Test device, test piece and installation, test, test report.

This section applies to engineering inspections and product inspections for wind-lift resistance of metal roofs using the dynamic pressure method.

2 Normative references

The following documents are indispensable for the application of this document. For dated reference documents, only the dated version applies to this document. For undated reference documents, the latest version (including all amendments) is applicable to this document.

GB/T 39794.1 Test method for wind resistance performance of metal roof Part 1: Static pressure method

3 Terms and definitions

The following terms and definitions apply to this document.

4 Detection principle

Use the air supply equipment to inflate the lower pressure tank of the metal roof to form a stable positive pressure, and at the same time pump air to the upper pressure tank of the metal roof, and Through the control device, the periodic undulating negative pressure is generated to form a resultant force that simulates the upward action of the wind load on the metal roof, so as to detect the metal The ability of the roof to resist wind.

5 Detection device

5.1 The detection device consists of an upper pressure tank, a lower pressure tank, installation frame, air supply equipment, pressure control device, pressure measurement device, and displacement measurement device. Measuring device and other components (see Figure 1).

5.2 The opening size of the upper and lower pressure tanks should be able to meet the requirements for the installation of the test piece, and should not be less than 3.05m×3.05m. The strength of the pressure tank The degree should be able to meet the testing requirements. Observation windows should be installed around the pressure tank, and lighting devices should be installed inside. The air outlet of the pressure tank should be installed Flow baffle.

5.3 The upper and lower pressure tanks should have independent air supply equipment. The air supply equipment should have the ability to apply a specified pressure difference, and the static pressure control device The setting should be able to adjust the stable air flow, and the dynamic pressure control device should be able to adjust the periodic fluctuating wind pressure, the peak and trough of the fluctuating wind pressure The value should meet the testing requirements, and the air supply and pressure control capabilities should meet the requirements of Chapter 7.

5.4 The angle between the side of the collecting cover of the upper pressure tank and the horizontal direction is 30°±2°, and the size of the top plate is (610±10)mm×(610±10)mm, And reserve the air outlet.

5.5 The installation frame should have sufficient rigidity and strength.

5.6 The total pressure measuring tube of the upper pressure tank is composed of 5 independent pressure measuring tubes distributed inside the box. The pressure measuring tube is 6mm in inner diameter.

Copper tubes, of which 4 piezometer tubes are diagonally distributed, and the angle between each piezometer tube and the bottom of the box is 45°, and the distance from the corner of the box is 1000mm, The fifth piezometric tube is arranged in the center of the upper box, and the ends of all piezometers are located at 180mm from the bottom surface of the box.

5.7 The total pressure measuring tube of the lower pressure tank is also composed of 5 independent pressure measuring tubes distributed inside the tank, and the pressure measuring tube has an inner diameter.

6mm copper pipes, of which 4 piezometer tubes are diagonally distributed, and the angle between each piezometer tube and the bottom of the box is 45°, and is away from the corner of the box 1000mm, the fifth piezometric tube is arranged in the center of the lower box, and the ends of all piezometers are located at 180mm on the upper surface of the bottom of the box.

5.8 The accuracy of the differential pressure sensor should reach 1% of the indicated value, and the measurement response speed should meet the requirements of fluctuating pressure measurement; the accuracy of the displacement meter should reach To 0.25% of full scale.

6 Specimen and installation

6.1 The test piece should be representative and consistent with the actual project. The profiled metal sheet roof shall include at least 3 spans and 5 panel widths and Its supporting system. Other metal roofs should include at least one force-bearing unit.

6.2 The materials, specifications and models of the test pieces shall be consistent with the drawings provided by the manufacturer, the installation of the test pieces shall meet the design requirements, and the stress conditions shall be consistent with those provided by the manufacturer.

In accordance with the actual situation, no special attachments or other additional measures should be taken.

6.3 The test piece and the pressure tank should be installed reliably and effectively sealed. The connection and sealing of the test piece and the pressure tank shall not restrict the change of the test piece shape. For single-laminated metal sheet roofs, plastic films with a thickness of no more than 0.15mm should be used for sealing before testing. Plastic film dense See Appendix A for the sealing method.

7 Detection