[China Glass Net] Tempered insulating glass has been widely used in curtain wall engineering. In the project, there is a case where the insulating glass is broken on one side of the glass. In the process of waiting for repair, whether the remaining side glass has the ability to resist the design wind pressure is a project concern. At the beginning of the engineering design, the theoretical calculations were selected, and then the prototypes were assembled and tested in our central curtain wall laboratory.
1, test analysis
According to the theory of insulating glass, the load is shared by two sheets of glass, and the load between the glass is transmitted through the compressed intermediate gas layer. When one side of the glass is broken, the gas layer cannot transmit the load, and only the single piece of glass is subjected to the load. It can be inferred that the deflection of the monolithic glass will be much greater than the deflection under normal working conditions, and the deflection according to the empirical formula needs to be verified by experiments.
1.1, test description
The test sample is a component type hidden frame glass curtain wall with a width of 3.64m and a height of 3.15m. The design wind pressure Wk=3.4kPa, the panel is 8Low-E+12A+8 hollow tempered glass, and the panel measuring point is located at the bottom of the glass panel at the bottom of the sample plate. Indoor side. Different from the common hidden frame glass curtain wall panel, this project does not bond the glass sub-frame on the indoor side glass surface, but arranges the aluminum component between the two original pieces when the film is assembled, and the pressure block penetrates into the glass panel and the aluminum The function of fixing the panel to the main material.
The test is divided into 4 steps: 1 normal anti-wind pressure detection of the sample glass; 2 wind-resistant deformation performance detection after the indoor side glass is destroyed; 3 repeated pressure detection; 4 wind load design value safety performance detection.
The test is carried out according to the requirements of GB/T15227-2007, and the deflection of the long midpoint of the short side of the glass panel is measured. Three displacement measuring instruments are arranged in the short side direction of the middle of the glass panel, and the measuring point spacing is 1710 mm. The deflection of the panel method is calculated according to the formula 1 by measuring the deformation amount of the center of the panel and the edge of the panel.
Where: fmax - surface normal deflection value, mm.
A0, b0, c0 - the initial stable reading value of each measuring point after preliminary pressure, mm.
a, b, c - the normal displacement of each measuring point corresponding to a certain pressure, mm.
According to the design requirements, the pressure is gradually increased, and the displacement of the panel under various pressure differences forms a deflection curve. Repeated pressurization testing and design of wind pressure safety performance testing are then performed.
The interior side glass of the bottom panel of the template is crushed from the corner, and the broken panel is placed close to the outdoor side glass. Deflection deformation was measured on the broken interior side glass surface, and repeated pressurization tests and design wind pressure safety performance tests were performed. During the deflection deformation phase, a greater pressure differential was used to test the response of the single-layer glass panel to uniform pressure under large deflection conditions.
1.2, analysis of results
Anti-wind pressure deformation stage analysis. The deflection measurement data before and after crushing are shown in Table 1. The ratio is the ratio of the distance between the measuring points and the deflection, and the value is not greater than the standard requirement, which is an important evaluation index.
According to the measured raw data, the response of the panel to the pressure before and after the glass cracking of the indoor side can be obtained.
It can be seen from the two sets of measurement data and deflection curves that, under the same wind pressure, the deflection of the single-layer glass is significantly larger than the deflection of the double-layer hollow glass, and the deformation amount is close to the standard upper deflection limit under the design pressure value of 55%. 2 Under the condition of low pressure, the deflection of the panel is approximately linear with the wind pressure; the pressure increases, the deflection shows a certain degree of convergence with the increase of the load, and the nonlinear characteristic is more obvious [4]. Therefore, the surface normal deflection standard limit 1/60 cannot be simply converted into the upper limit of 1/150 of the deformation detection according to the linear relationship. The large deflection deflection result cannot be estimated based on the large deflection at the time of deformation detection, and must be tested by actual measurement.
Safety performance analysis: In the repeated pressure detection phase and the design wind pressure safety detection phase, the outdoor side glass is individually subjected to wind load without damage. The broken glass side of the indoor side is close to the glass side of the outdoor side, and remains intact without any debris falling, as shown in Figure 5.
The large surface of the broken surface itself is not subjected to wind load, and due to the special structure of the joint with the main material, the wind pressure is directly transmitted to the main material through the aluminum member and the compact, and no shear deformation is generated on the edge portion of the broken surface, The integrity of the interior side glass plays a positive role.
1.3, conclusion
Through the above analysis, the following conclusions can be drawn: 1 The indoor side glass is subjected to external force fracture (shard state but not dropped). After the design wind load pressure Wk acts for 10 seconds, the outdoor side glass is not damaged, and the indoor side glass fragments are not dropped. The specimen remains relatively intact. According to this, it can be inferred that in the actual project, if the indoor side glass is damaged, the curtain wall can resist the design wind pressure in a short time waiting for the replacement of the glass, and corresponding protective measures should be taken to prevent the debris from falling and causing damage. 2 After the indoor side glass is broken, it is closely attached to the outdoor side glass. In the anti-wind deformation detection stage, the deflection deformation amount is significantly increased. In the actual work, the influence of excessive deflection should be considered. 3 The glass splicing method of the project and the connection mode between the glass panel and the main material have positive significance for the overall wind pressure resistance performance after the indoor side glass is damaged, and have practical application value.
2, the conclusion
According to the empirical formula, or the results obtained by computer simulation, the curtain wall design is different from the actual project. In this project, the safety performance of the curtain wall in extreme cases needs to be confirmed by the laboratory. The engineering inspection of the curtain wall is of great significance for verifying the rationality of the design, promoting new techniques, and ensuring the quality of the construction project.
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