ã€ALUMINIUM NETWORK】At present, many doors and windows companies lack the support of theoretical calculation methods in calculating the wind pressure resistance performance of insulated aluminum alloy doors and windows. Therefore, there are few solutions and they are very helpless; The scientific calculation formula is used to calculate the result. There are two possible results. One is the instability of the “degree of rigidity†of the middle stern member, which leads to the hidden dangers of the project quality, resulting in poor airtightness of the doors and windows, deteriorating the insulation performance, and encountering wind and rain. In the weather, the doors and windows leaked; the other is that the safety factor of the "steel" design of the Zhongwan rod was too large, causing unnecessary waste.
The American Building Construction Association (AAMA) TIR-A8-04 standard describes the deflection calculation of insulation beams, the calculation of large compression and tensile stress, and the calculation of large vertical shear stress. It is a reference book for door and window designers. .
First, the calculation principle:
1. Calculation of deflection and equivalent moment of inertia of insulation beams:
This paper is a method to estimate the equivalent moment of inertia of a simply supported beam with a non-uniform cross section under the effect of concentrated or uniform loads. This model is a "composite" beam that is continuously joined by a relatively hard surface (such as aluminum alloy) and a softer core material (insulated polyurethane structural glue).
The key issue for calculating insulating aluminum alloy profiles is the shear deformation of the insulation material. In calculating the simply supported beam of a pure aluminum-aluminum alloy profile subjected to a concentrated or uniform load, the formula is: Bernoulli-Euler equation (EIy "= M), and the amount of shear deformation is ignored. However, when When there is a relatively soft thermal insulation material in the axial direction of the profile bars, the behavior of the “composite†beam will be complicated.When subjected to the load, the cross-sectional size of the “composite†beam will be due to the shear deformation of the insulation material. The change occurs in the shear deformation of the insulating material so that its shape changes from a rectangular shape to a parallelogram shape.
Since the insulation material is located between two aluminum alloy profiles, when it is used as a simply supported beam, the deformation of the entire composite profile and the stress on the aluminum alloy profile are increased compared with pure aluminum alloy profiles; The shear flow transmitted in the length direction (the shear stress of the thermal insulation rubber multiplied by the width b' of the thermal insulation glue) is greatly reduced.
Figure 1
In the formulas and diagrams we will use the following parameters:
A=tw(hg)—Shear area of ​​aluminum alloy material (mm2)
AC—The total cross-sectional area of ​​the elastomer (mm2)
A1,a2—area of ​​aluminum profiles 1 and 2 (mm2)
b=AC/DC—average width of elastomer (mm)
B'—the net width between two bumps (mm)
C11,c22,D—are the distance from the centroid axis to the outer surface of the two aluminum profiles and the distance between the two axes. (mm)
DC—large depth of heat-sink (mm)
E=70000N/mm2—Young's modulus of aluminum section EC—Young's modulus of elastic body (1650N/mm2)
G—insulation distance between two bumps of heat insulation groove (mm)
GC=EC/[2(1+v)]—elastomeric shear modulus (N/mm2); v is the Poisson's ratio of the elastomer
h—The total width of the aluminum section (mm)
H1, h2—distance between the center of gravity of the aluminum profile and the two outer surfaces (mm)
I01, I02 - moment of inertia of aluminum profiles 1 and 2 (mm4)
L—span, distance between two fulcrums (mm)
W0—uniform load (N/mm)
P—Concentrated load (N)
Tw—the thickness of the aluminum struts, or the sum of the thicknesses of the aluminum bars. Tw=Aw/(hg), Aw is the sum of the standing bars of the two profiles multiplied by their respective heights.
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