CN113158284B - Method for calculating lateral bearing capacity of orthogonal laminated wood wall-floor slab angle steel node after fire - Google Patents
Method for calculating lateral bearing capacity of orthogonal laminated wood wall-floor slab angle steel node after fire Download PDFInfo
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- 239000002023 wood Substances 0.000 title claims abstract description 44
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 39
- 239000010959 steel Substances 0.000 title claims abstract description 39
- 238000000034 method Methods 0.000 title claims abstract description 22
- 238000004364 calculation method Methods 0.000 claims abstract description 24
- 238000010304 firing Methods 0.000 claims abstract description 12
- 238000005452 bending Methods 0.000 claims abstract description 8
- 238000010079 rubber tapping Methods 0.000 claims description 32
- 238000003763 carbonization Methods 0.000 claims description 25
- 239000002184 metal Substances 0.000 claims description 16
- 238000012937 correction Methods 0.000 claims description 7
- 230000000694 effects Effects 0.000 claims description 7
- 238000005315 distribution function Methods 0.000 claims description 4
- 230000035515 penetration Effects 0.000 claims description 2
- 238000012360 testing method Methods 0.000 abstract description 2
- 238000013461 design Methods 0.000 description 4
- 238000011160 research Methods 0.000 description 3
- 239000004566 building material Substances 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 230000032798 delamination Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 230000009970 fire resistant effect Effects 0.000 description 1
- 239000011120 plywood Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/10—Geometric CAD
- G06F30/13—Architectural design, e.g. computer-aided architectural design [CAAD] related to design of buildings, bridges, landscapes, production plants or roads
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/20—Design optimisation, verification or simulation
- G06F30/23—Design optimisation, verification or simulation using finite element methods [FEM] or finite difference methods [FDM]
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F2119/00—Details relating to the type or aim of the analysis or the optimisation
- G06F2119/14—Force analysis or force optimisation, e.g. static or dynamic forces
Abstract
The invention discloses a method for calculating lateral bearing capacity of an orthogonal laminated wood wall-floor slab angle steel node after fire, which is characterized by comprising the following steps of: the method comprises the following steps: step one: determining the section layering condition of the CLT laminate after firing by the firing time of the orthogonal veneer wall body-floor slab angle steel node; step two: calculating the equivalent pin slot bearing length and the effective nailing length of the pin shaft type fastener according to the determined sectional layering condition of the CLT laminate after the fire; step three: and calculating the residual bearing capacity of the CLT wall-floor angle steel node after the fire is received by adopting a lateral bearing capacity calculation formula considering the influence of the additional bending moment. The error between the calculated value and the test value is within 11%, and the method has certain reliability.
Description
Technical Field
The invention designs a calculation method for lateral bearing capacity of an orthogonal glued wood wall-floor slab angle steel node after fire, and belongs to the technical field of wood structure design.
Background
With the continuous promotion of the urban process in China, various buildings are pulled up, but huge energy consumption and environmental pollution are brought while rapid development is carried out. Compared with the traditional building material, the wood has outstanding environmental protection performance, and along with the continuous improvement of people's environmental awareness, the wood structure building becomes a new development trend. The orthogonal laminated wood (CLT) is a novel building material, is generally formed by bonding and pressing 3, 5 or 7 layers of solid wood sawn timber or structural composite boards in an adhesive manner, has excellent mechanical properties because of a special assembly mode, and is commonly used for plates and walls of building structures.
The orthogonal glued wood wall-floor slab node is used as the key stress part of the structure, is the most complex part in the design, and the wood structure has the characteristic of inflammability, and has important significance for researching the fire performance of the orthogonal glued wood wall-floor slab node. Many researches have been carried out by students at home and abroad aiming at wood nodes, but most of the researches focus on normal-temperature bearing capacity, fire performance and the like, and only basic researches at normal temperature exist for bearing capacity calculation of the nodes, so that a method for calculating the bearing capacity of the nodes after the fire is not yet proposed.
Disclosure of Invention
The invention aims to: in order to provide related theoretical guidance for fire-resistant design of the angle steel node of the orthogonal laminated wood wall body-floor slab, a novel method for calculating lateral bearing capacity of the angle steel node after fire is provided.
In order to achieve the above purpose, the technical scheme adopted by the invention comprises the following steps:
step one: according to the firing time of the angle steel node of the orthogonal laminated wood wall body and the floor slab, calculating the carbonization depth a of the orthogonal laminated wood char The equivalent thickness of the full-strength layer of the wood in the folding area is reduced, so that the section layering condition of the CLT laminate after the fire is determined, and the calculation method is as follows:
a char ＝β t t＝2.15β n t 0.813
h equ ＝h ||,equ +h ⊥,equ
wherein beta is n For the nominal linear carbonization speed of the wood, 0.635mm/min was taken, t being the time to fire. h is a equ Is the equivalent thickness of the full strength layer, h ||,equ To reduce the equivalent thickness of the wood grain layer in the zone x ||,1 X is the nearest distance between the carbonization layer and the following stress layer ||,2 K is the farthest distance between the carbonization layer and the following stress layer || (x) A reduction coefficient distribution function for reducing the wood grain layer strength in the area, h ⊥,equ To reduce the equivalent thickness of the wood transversal layer in the zone x ⊥,1 X is the nearest distance between the carbonization layer and the transverse stress layer ⊥,2 K is the farthest distance between the carbonization layer and the transverse stress layer ⊥ (x) And the distribution function of the reduction coefficient is used for reducing the intensity of the wood transverse grain layer in the area.
Step two: according to the section layering condition of the CLT laminate after the fire, which is determined in the step one, calculating the equivalent pin groove bearing length t in a calculation formula of the lateral bearing capacity of the pin shaft type fastener mod And effective staple length l in the axial bearing capacity calculation formula ef 。
t mod ＝t ini -d char -d z +h equ -ηγ
l ef ＝min{t l ,t mod -t d }
Wherein eta is an equivalent pin groove bearing length correction coefficient considering the carbonization effect of the round corners, r is the carbonization radius of the round corners, t ini D is the bearing length of the pin slot before fire z To reduce the thickness of the area, the value is 16.3mm, t l For the length of the threaded part of the self-tapping screw, t d The length of the tip of the self-tapping screw is approximately equal to the diameter of the screw.
Step three: and (3) selecting a calculation formula of the lateral bearing capacity of the orthogonal laminated wood wall-floor slab angle steel node after fire according to the thickness of the node metal plate, and taking the calculation result of the step two into the formula to obtain a calculation result, wherein when the thickness of the metal plate is between the thin plate and the thick plate, the lateral bearing capacity of the node is calculated by adopting a linear interpolation method.
Resistance to plucking bearing capacity of self-tapping screw:
for a metal thin plate (thickness of the metal plate is less than or equal to 0.5d ef ) The lateral bearing capacity takes the minimum of the following two formulas:
for thick metal plates (thickness of metal plate is equal to or greater than d ef ) The lateral bearing capacity takes the minimum value of the following three formulas:
F v,Rk ＝f h,k t mod d ef
wherein d is the outer diameter of the self-tapping screw, l ef For effective driving length ρ of self-tapping screw k The value is related to the nailing direction of the self-tapping screw, the density of the CLT plate is obtained when the self-tapping screw is nailed perpendicular to the plane of the CLT plate, the density of the nailing layer plate is obtained when the self-tapping screw is nailed parallel to the plane of the CLT plate, and epsilon is the self-tapping screw and the CLT plateIncluded angle of plane, t ini For a small value between the CLT thickness and the fastener penetration depth before firing, t mod For the bearing length of the equivalent pin groove after fire correction, f h,k Is the bearing strength of pin grooves at normal temperature, d ef For the effective diameter of the fastener, the effect of the threaded part should be considered for the screw, 1.1 times of the inner diameter of the thread is taken, M y,Rk F is the yield bending moment after the self-tapping screw is high Wen Shejian ax,Rk Is the pulling-resistant bearing capacity of the fastener. In the formula (i),the value of the term is the bearing capacity under the rope effect, and the value of the term is smaller than or equal to the calculated bearing capacity of the previous term.
When the thickness of the metal plate is between the thin plate and the thick plate, the lateral bearing capacity of the metal plate is calculated by adopting a linear interpolation method between the thin plate and the thick plate.
The beneficial effects of the invention are as follows: the additional bending moment effect caused by the fact that the section is reduced due to wood carbonization of the angle steel node of the orthogonal laminated wood wall body and the floor after the fire is considered, and the calculation method for the lateral bearing capacity of the angle steel node of the orthogonal laminated wood wall body and the floor after the fire is provided for reference of designers.
Drawings
FIG. 1 is a flow chart of calculation of lateral bearing capacity of an orthogonal laminated wood wall-floor slab angle steel node after fire;
FIG. 2 is a schematic illustration of an orthogonal plywood wall-floor angle steel node;
FIG. 3 is a cross-sectional delamination of a CLT laminate after firing;
FIG. 4 is a schematic view of a stress layer with the normal lines and the transverse lines in the reduced area (the normal line layer is close to the carbonization layer);
FIG. 5 is a schematic view of a compliant, cross-grain stress layer (cross-grain layer near char layer) for a reduced zone;
FIG. 6 is a schematic diagram of equivalent bearing length values;
fig. 7 is a schematic view of effective staple length values.
Wherein: 1. CLT wall; 2. CLT floor; 3. a screw; 4. angle steel.
Detailed Description
The calculation method of the present invention will be further described with reference to the present embodiment.
According to the invention, the orthogonal laminated wood wall body-floor slab angle steel nodes are formed by connecting a CLT wall body 1, a CLT floor slab 2, a screw 3 and an angle steel 4, and the figure 2 is seen.
The sizes of the CLT wall body and the floor slab of each angle steel node are 300mm multiplied by 125mm, the section of the CLT plate is 5mm multiplied by 25mm, each CLT plate is fixed with the angle steel connecting piece through 8 self-tapping screws, and the screw cap length of the self-tapping screws is 3mm.
Example 1:
in order to calculate the lateral bearing capacity of the angle steel nodes of the orthogonal laminated wood wall and the floor slab after being subjected to fire, the calculation method provided by the invention has the advantages that the CLT wall and the floor slab of each angle steel node are 300mm multiplied by 125mm, the section of the CLT plate is 5 multiplied by 25mm, each CLT plate is fixed with an angle steel connecting piece through 8 self-tapping screws, the nut length of each self-tapping screw is 3mm, the self-tapping screw length of each angle steel node is 60mm, and the fire time is 20min.
The length of the tapping screw of the angle steel node 2 is 80mm, and the fire time is 20min.
When the fire time is 20min, the related calculation parameters are as follows:
yield bending moment of self-tapping screw after high temperature reduction: m is M y,Rk ＝3917N·mm，
And considering the equivalent pin groove bearing length correction coefficient of the fillet carbonization effect: η=0.2.
The method comprises the following steps:
the first step: according to the firing time, the carbonization depth of the CLT is calculated, the wood grain layer in the area is reduced, and the equivalent thickness of the horizontal grain layer is as follows:
depth of carbonization of CLT: a, a char ＝β t t＝2.15β n t 0.813 ＝2.15×0.635×20 0.813 ＝15.6mm
The thickness of the laminate of the CLT plate is 25mm, the carbonization depth is 15.6mm, the thickness of the reduced area is 16.3mm, so that the thickness of the smooth layer in the reduced area is 25-15.6=9.4 mm, and the thickness of the transversal layer is 16.3-9.4=6.9 mm
Equivalent thickness of the reduced area compliant layer:
equivalent thickness of the cross grain layer of the reduced area:
equivalent thickness of the full strength layer of the reduced area:
h equ ＝h ||,equ +h ⊥,equ ＝6.5+9.4＝15.9mm
and a second step of: according to the section seal layer condition after the CLT laminate is ignited, which is determined in the step one, calculating the equivalent pin groove bearing length t in a calculation formula of the lateral bearing capacity of the pin shaft type fastener mod And effective staple length l in the axial bearing capacity calculation formula ef 。
According to the finite element software ABAQUS analysis results, the fillet char radius r=13 mm. Equivalent pin groove bearing length correction value:
t mod ＝t ini -d char -d z +h equ -ηγ＝60-3-15.6-16.3+15.9-0.2×13＝38.4mm
effective staple length: l (L) ef ＝min{t l ,t mod -t d }＝min{40,38.4-5}＝33.4mm
And a third step of: according to the thickness of the node metal plate, a calculation formula of the lateral bearing capacity of the orthogonal laminated wood wall-floor slab angle steel node after fire is selected, and the calculation result of the second step is brought into the formula to obtain a calculation result, and the lateral bearing capacity is calculated by adopting a linear interpolation method because the thickness of the metal plate is between the thin plate and the thick plate.
Axial bearing force of self-tapping screw after receiving fire:
1) For 2.09mm (0.5 d ef ) Thick goldThin plate
(1) Pin rigid body rotation yield
(2) Single plastic hinge yielding of side member
Taking F v,Rk =200+200=400N 2) for 4.18mm (d ef ) Thick metal thick plate
(1) Bearing yield of pin slot of main component
F v,Rk ＝f h,k t mod d ef ＝23.28×38.4×4.18＝3736N
(2) Yield of single plastic hinge of main component
(3) Yield of double plastic hinge
Taking F v,Rk =381+381=762N 3) for a 3mm thick metal plate
Calculating the lateral bearing capacity corresponding to the metal plate with the thickness of 3mm by adopting a linear interpolation method:
2 rows of self-tapping screws are shared in the CLT wall body-floor slab angle steel node, 4 self-tapping screws are shared in each row, and the bearing capacity of the whole node is that:
F v,Rk,sum ＝558×2×4＝4464N。
example 2:
in order to calculate the lateral bearing capacity of the angle steel node of the orthogonal laminated wood wall body and the floor slab after being subjected to fire, the calculation method provided by the invention has the advantages that the length of the self-tapping screw of the angle steel node is 80mm, and the fire time is 20min.
When the fire time is 20min, the related calculation parameters are as follows:
yield bending moment of self-tapping screw after high temperature reduction: m is M y,Rk ＝3917N·mm，
And considering the equivalent pin groove bearing length correction coefficient of the fillet carbonization effect: η=0.2.
The same calculation method as in example 1 was used to calculate the calculated load capacity remaining after firing of the angle steel node.
Table 1 shows the calculated values of the residual bearing capacity after firing of the angle steel nodes of example 1 and the angle steel nodes of example 2 compared with the test values.
As can be seen from table 1, according to the method for calculating the residual bearing capacity of the orthogonal laminated wood wall-floor angle steel node after fire, the calculated bearing capacity of the node has smaller difference from the experimental value, and the error is within 11%, so that the method can be used for reference by related designers.
Claims (4)
1. A method for calculating lateral bearing capacity of an orthogonal laminated wood wall-floor slab angle steel node after fire is characterized by comprising the following steps: the method comprises the following steps:
step one: determining the section layering condition of the CLT laminate after firing by the firing time of the orthogonal veneer wall body-floor slab angle steel node;
step two: calculating the equivalent pin groove bearing length t of the pin shaft type fastener according to the section layering condition of the CLT laminate after the fire is determined in the step one mod And effective staple length l ef ；
Step three: calculating the residual bearing capacity of the CLT wall-floor angle steel node after fire by adopting a lateral bearing capacity calculation formula considering the influence of the additional bending moment;
the first step comprises the following steps:
calculating carbonization depth a of CLT laminate char ：
a char ＝β t t＝2.15β n t 0.813
Wherein beta is n Is the nominal linear carbonization speed of the wood; t is the time of firing;
reducing the wood strength in the double-reduction area, and calculating the equivalent thickness h of the full-strength layer equ ：
h equ ＝h P,equ +h ⊥,equ
Wherein h is equ Is the equivalent thickness of the full strength layer; h is a P,equ Is the equivalent thickness of the wood grain layer in the reduction zone; x is x P,1 Is the nearest distance between the carbonization layer and the following stress layer; x is x P,2 Is the farthest distance between the carbonization layer and the following stress layer; k (k) P (x) A reduction coefficient distribution function for reducing the wood grain layer strength in the area; h is a ⊥,equ Is the equivalent thickness of the wood transverse grain layer in the reduction zone; x is x ⊥,1 Is the nearest distance between the carbonization layer and the transverse stress layer; x is x ⊥,2 Is the farthest distance between the carbonization layer and the transverse grain stress layer; k (k) ⊥ (x) A reduction coefficient distribution function for the intensity of the wood cross grain layer in the reduction area;
determining the section layering condition of the CLT laminate after firing according to the carbonization depth and the equivalent thicknesses of the transverse grain layer and the smooth grain layer;
in the second step, the equivalent pin slot bearing length t mod And effective staple length l ef The method comprises the following steps of:
t mod ＝t ini -a char -d z +h equ -ηγ
l ef ＝min{t l ,t mod -t d }
wherein t is ini The bearing length of the pin groove before the fire is reached; d, d z The thickness of the folding zone is 16.3mm; η is an equivalent pin groove bearing length correction coefficient considering the fillet carbonization effect; r is the carbonization radius of the fillet; t is t l The length of the thread part of the self-tapping screw is equal to that of the thread part of the self-tapping screw; t is t d The length of the tip of the self-tapping screw is;
in the third step: the calculation formula of the lateral bearing capacity of the CLT wall-floor angle steel node after being subjected to fire is as follows, wherein the influence of the additional bending moment is considered:
resistance to plucking bearing capacity of self-tapping screw:
for a thickness of less than or equal to 0.5d ef The lateral bearing capacity of which takes the minimum of the following two formulas:
for a thickness equal to or greater than d ef The lateral bearing capacity of the metal thick plate is the minimum value in the following three formulas:
F v,Rk ＝f h,k t mod d ef
wherein d is the outer diameter of the self-tapping screw; l (L) ef The effective nailing length of the tapping screw is as follows; ρ k The value is related to the nailing direction of the tapping screw, the density of the CLT plate is obtained when the tapping screw is nailed perpendicular to the plane of the CLT plate, and the density of the nailing layer plate is obtained when the tapping screw is nailed parallel to the plane of the CLT plate; epsilon is the included angle between the self-tapping screw and the plane of the CLT plate; t is t ini Is a small value between the CLT thickness and the fastener penetration depth before fire; t is t mod The bearing length of the equivalent pin groove after fire correction is as follows; f (f) h,k The pin groove bearing strength at normal temperature; d, d ef Is the effective diameter of the fastener; m is M y,Rk Is the yield bending moment of the fastener;
when the thickness of the metal plate is between the thin plate and the thick plate, the lateral bearing capacity of the metal plate is calculated by adopting a linear interpolation method between the thin plate and the thick plate.
2. The method for calculating the lateral bearing capacity of the orthogonal laminated wood wall-floor angle steel node after fire according to claim 1, which is characterized by comprising the following steps: thickness d of the reduced area z The value is 16.3mm.
3. The method for calculating the lateral bearing capacity of the orthogonal laminated wood wall-floor angle steel node after fire according to claim 1, which is characterized by comprising the following steps: is the nominal linear carbonization speed beta of wood n Taking 0.635mm/min.
4. The method for calculating the lateral bearing capacity of the orthogonal laminated wood wall-floor angle steel node after fire according to claim 1, which is characterized by comprising the following steps: is the effective diameter d of the fastener ef The value is 1.1 times of the thread inner diameter of the fastener.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110008637A (en) * | 2019-04-22 | 2019-07-12 | 东南大学 | Consider the determination method of orthogonal glued wood floor char depth under laminate dropping situations |
| CN110059420A (en) * | 2019-04-22 | 2019-07-26 | 东南大学 | The method for determining single side orthogonal gluing wood floor zero intensity layer thickness value under by fire |
| CN110750829A (en) * | 2019-10-18 | 2020-02-04 | 东南大学 | Method for determining zero-strength layer thickness value of orthogonal laminated wood floor slab under single-side fire |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110008637A (en) * | 2019-04-22 | 2019-07-12 | 东南大学 | Consider the determination method of orthogonal glued wood floor char depth under laminate dropping situations |
| CN110059420A (en) * | 2019-04-22 | 2019-07-26 | 东南大学 | The method for determining single side orthogonal gluing wood floor zero intensity layer thickness value under by fire |
| CN110750829A (en) * | 2019-10-18 | 2020-02-04 | 东南大学 | Method for determining zero-strength layer thickness value of orthogonal laminated wood floor slab under single-side fire |
Non-Patent Citations (1)
| Title |
|---|
| 胶合木梁三面受火后力学性能的试验研究;胡小锋;陈玲珠;许清风;韩重庆;冷予冰;;建筑结构(第16期);全文 * |
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