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How to calculate the carrying capacity of glass
Source：本站 Time：2020/3/9 10:04:13 frequency：
1. Glass bearing state
The door, window and curtain wall have two states under the action of wind pressure:
One is four-sided support, suitable for framed doors and Windows, curtain wall.
Two is two opposite edge support, suitable for glass doors, etc.
2. Calculation of wind load on glass
A) look up three sets of formulas from JGJ113
When the four-side support, when t≤6mm, Wk=0.2 majority
When t> At 6mm, Wk= (0.2t1.6+0.8) /Amax minority
When supported by two opposite sides, Wk=0.142 t/L glass door
Where, Wk -- wind load standard value kPa
Amax - large area of glass ㎡
L -- allowable span m of glass
T -- thickness of glass mm
Alpha - adjust the coefficient
Glass adjustment coefficient
Glass types of ordinary semi-tempered tempered sandwich hollow wire embossing fire
Adjustment coefficient 1.01.62.0~3.00.81.50.50.63.0~4.5
B) calculation by example
The size of 4 steel +A+5 is 1200×1800, and the bearing capacity of the glass is calculated.
Formula: Wk = 0.2 a alpha
Calculation and value: Wk=0.2×1.5×41.8/1.2×1.8=1.68kPa.
Analysis: (1) when the toughened sheet and float combination, according to the sheet calculation advantage, otherwise disadvantage, the cost is high;
(2) assume that the two pieces are equal, the outside is toughened, the inside is float, did not explain;
JGJ102 regulations for the outside of the steel, according to the outside of the steel calculation.
The thickness of the outer fireproof glass is 5mm, and the thickness of the inner toughened glass is 4mm.
Formula: Wk= = (0.2t1.6+0.8) /Amax
Calculation and value: Wk=0.8 (0.2×91.6+0.8) /1.2×1.8= 2.78kpa
Analysis: at this time the carrying capacity is large, but the main role is fire prevention, the cost is very high;
The wind pressure adjustment coefficient of toughened glass and monolithic fireproof glass should be determined by test.
Example three, adopt 15mm toughened glass, its dimension is the door of 800×2000mm, ask glass bearing capacity?
Formula: Wk = alpha 0.142 t/a L
Calculation and value: Wk=0.142×2×15/2.0
Analysis: (1) door glass strict requirements, and thick;
L take the disadvantage as long side, short side is 1.94kPa;
Glass damage is mainly tension damage, not pressure damage, so bending is the main contradiction.
3. Problems that should be paid attention to in calculation
A) the calculation formula of jgj113-2003 and 97 is the same, but the parameters are slightly changed.
Example: toughened glass is changed from 1.5~3.0 to 2.0~3.0 and the adjustment coefficient of fireproof glass is increased.
B) the curtain wall glass is still in accordance with the regulations of jgj102-× ×××, the two have differences and cannot be used in combination.
C) how to deal with insulating glass composed of toughened glass and float glass with different thickness.
Outer steel + inner float, 1.5 if two equal; When the outside is thin and the inside is thick, take thin slice, the problem is not big; When it's thick on the outside and thin on the inside, it's hard to use.
D) when the use condition of laminated glass exceeds 70℃, the adjustment coefficient is reduced from 0.8 to 0.6, and attention should be paid to the use in the south.
E) the adjustment coefficient of toughened glass and fireproof glass gives a range. How to take the value shall be provided by the manufacturer; otherwise, it is advantageous to take a small value, which shall be determined by test when the combination of toughened glass and fireproof glass is combined.
F) toughened glass, different places, glass manufacturers to provide, and to assume economic responsibility.
Analysis: (1) ANSI is the glass factory to provide parameter values, and ensure the quality;
(2) the toughened glass has the problem of self-explosion, abroad is about 8%0, abroad is greater than this value;
Toughened glass still has assembly problem, profile deformation problem, glass flatness is 2%0, from this take lower limit advantageous.
G) glass calculation, and the following items are not included in this scope, but should be noted.
Such as glass disturbance, glass thermal stress, glass gravity, glass gap, glass thermal performance, underwater glass, etc.
The door, window and curtain wall have two states under the action of wind pressure:
One is four-sided support, suitable for framed doors and Windows, curtain wall.
Two is two opposite edge support, suitable for glass doors, etc.
2. Calculation of wind load on glass
A) look up three sets of formulas from JGJ113
When the four-side support, when t≤6mm, Wk=0.2 majority
When t> At 6mm, Wk= (0.2t1.6+0.8) /Amax minority
When supported by two opposite sides, Wk=0.142 t/L glass door
Where, Wk -- wind load standard value kPa
Amax - large area of glass ㎡
L -- allowable span m of glass
T -- thickness of glass mm
Alpha - adjust the coefficient
Glass adjustment coefficient
Glass types of ordinary semi-tempered tempered sandwich hollow wire embossing fire
Adjustment coefficient 1.01.62.0~3.00.81.50.50.63.0~4.5
B) calculation by example
The size of 4 steel +A+5 is 1200×1800, and the bearing capacity of the glass is calculated.
Formula: Wk = 0.2 a alpha
Calculation and value: Wk=0.2×1.5×41.8/1.2×1.8=1.68kPa.
Analysis: (1) when the toughened sheet and float combination, according to the sheet calculation advantage, otherwise disadvantage, the cost is high;
(2) assume that the two pieces are equal, the outside is toughened, the inside is float, did not explain;
JGJ102 regulations for the outside of the steel, according to the outside of the steel calculation.
The thickness of the outer fireproof glass is 5mm, and the thickness of the inner toughened glass is 4mm.
Formula: Wk= = (0.2t1.6+0.8) /Amax
Calculation and value: Wk=0.8 (0.2×91.6+0.8) /1.2×1.8= 2.78kpa
Analysis: at this time the carrying capacity is large, but the main role is fire prevention, the cost is very high;
The wind pressure adjustment coefficient of toughened glass and monolithic fireproof glass should be determined by test.
Example three, adopt 15mm toughened glass, its dimension is the door of 800×2000mm, ask glass bearing capacity?
Formula: Wk = alpha 0.142 t/a L
Calculation and value: Wk=0.142×2×15/2.0
Analysis: (1) door glass strict requirements, and thick;
L take the disadvantage as long side, short side is 1.94kPa;
Glass damage is mainly tension damage, not pressure damage, so bending is the main contradiction.
3. Problems that should be paid attention to in calculation
A) the calculation formula of jgj113-2003 and 97 is the same, but the parameters are slightly changed.
Example: toughened glass is changed from 1.5~3.0 to 2.0~3.0 and the adjustment coefficient of fireproof glass is increased.
B) the curtain wall glass is still in accordance with the regulations of jgj102-× ×××, the two have differences and cannot be used in combination.
C) how to deal with insulating glass composed of toughened glass and float glass with different thickness.
Outer steel + inner float, 1.5 if two equal; When the outside is thin and the inside is thick, take thin slice, the problem is not big; When it's thick on the outside and thin on the inside, it's hard to use.
D) when the use condition of laminated glass exceeds 70℃, the adjustment coefficient is reduced from 0.8 to 0.6, and attention should be paid to the use in the south.
E) the adjustment coefficient of toughened glass and fireproof glass gives a range. How to take the value shall be provided by the manufacturer; otherwise, it is advantageous to take a small value, which shall be determined by test when the combination of toughened glass and fireproof glass is combined.
F) toughened glass, different places, glass manufacturers to provide, and to assume economic responsibility.
Analysis: (1) ANSI is the glass factory to provide parameter values, and ensure the quality;
(2) the toughened glass has the problem of self-explosion, abroad is about 8%0, abroad is greater than this value;
Toughened glass still has assembly problem, profile deformation problem, glass flatness is 2%0, from this take lower limit advantageous.
G) glass calculation, and the following items are not included in this scope, but should be noted.
Such as glass disturbance, glass thermal stress, glass gravity, glass gap, glass thermal performance, underwater glass, etc.