1. Program Continuing - Stability of wall panels
Example with combined section in a stability wall
Floor level (Etageadskillelse)
Beam model (Bjælkemodel)
Stringer method (Stringermetoden)
Project
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2. Clasical procedure for building calculations: Define the building
Class of consequents
Location of the building (Wind category)
Define the loads
Design the load bearing system
Floor levels (Etagedæk)
Walls, columns, beams ect.
Design the stability system (plastic or elastic)
Design the wall panels for rotation and gliding
Design the floor levels (beam method or stringer method)
Connection – walls, decks ect. (Samlinger, støbeskel)
Robustness.
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3. Example of wind load >< mass load on the gable
Wind load on the gable:
we=qp(D-E)ρ
D og E is a formfactor for wind on the facade and is calculates to D=0,74 og E=-0,38 (Because of h/d=22/40=0,55)
correlationsfactor ρ=0,85
we=0,939*(0,74-(-0,38))*0,85=0,89kN/m2
This value is use in formula 6.10b
6.10b: 0,9*G 1,5*ψ0*Q 1,5*V*KFI (Q=0, when it is favorable)
6.12a/b: 1,0*G ψ2*Q + Ad (ψ2=0,2 for domestic- and office areas)
(ψ2=0,2 for både boliger og kontorer)
Which situation is the most dangerous one?
What's the contribution from geometrical imperfection Vθ?
This is not at sum. Combination of loads is a describtion on how to combine loads.
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4. Wall panel – Elastic design, tension
Stresses in the bottom of the wall is found by the use of Navier:
If there is tensile stress in the wall the wall will rotate and we need to aplly some reinforcement in the foundation (anchor the wall/in Danish: trækforankres).
Example P=15kN i LAK 6.10b:
σ = -123kN/m2 og 383kN/m2
Tension! I.e. the wall has to be anchored
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5. Shear force in a vartical connection in a wall Elastic design:
Connections in walls the shear stress can be calculated by the use of Grashoffs formula:
When using Grashoff the horizontal shear stress is determinate and this is equal to the vertical shear stress and can therefore be use.
See example 7.2 in the book
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6. Wall panel – Plastic design.
Eccentric vertical reaction
By the use of static equivalent the normal force can be moved the distance “e” and distributed over a smaller area
The effective area and the compressive stress is determinate.
The eccentric is calculated:
e=M/N
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7. Plastisk design – Shear in a wall connection
When combining profiles the force between the web and flange is determinate.
The flange i cut free.
Normal stresses in top and bottom of the flange is determinate.
The normal stress from the profile dead load is added.
Se the example in the book (7.4)
Now the shear force in the connection can be determinate by the means of equalibrium.
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8. Design - wall panel, plastic
3 storeys high
Wind on the facade
The wall carries no decks or a roof structure.
Design the wall for:
Rotation
Gliding
Shear force in the connection between body and flange
What would be different if the wind from the other side ? (from the right side)
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9. The Deck Function of the deck: Vertical load Designed as a plate/beam
Horizontal load is distributed to the stability walls:
Designed as a panel
To secure that the gable against suction from the wind
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10. Panel made of hollow decks
Eample of a deck plan with reinforcement.
(Eksempel på dækelementplan med fugearmering):
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11. Reinforment in decks and their function
Edge reinforcement:
Secures the outer deck elements in the gable from the wind
Tension in the deck panel when the deck is functioning as a beam
Shear forces between hollow decks can be obtained and transferred
U-bars around the edge reinforcement:
Makes sure that the façade elements are secured for suction on the facade. The same goes for the gable
Also function as reinforcement against shear forces – Like a beam
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12. Horizontal load on the deck panel
-0,3 til -0,7
0,7 til 0,8
-1,2 til -0,5
Wind pressure and suction on the facade
Wind suction on the gable
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13. Horizontal load on the deck panel
The load on the deck panel is distributed as a uniformed load [kN/m]
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14. Beam model
The deck panel is disigned as beam. It has 6 supports and we get the following section forces:
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15. Beam model L<2zcotθ Deck panel: The Moment
Deteminate the reinforcement in the connection at the facade for the maximale moment:
In most cases the reinforcement detemainate for Mmax is use in for the hole buildings length.
Design for shear forces:
The reinforcement are place in the gab between the deck so it function as a beam
Reinforcement for shear can be neglected, if:
L<2zcotθ
L, is the distant between the supports (stability walls)
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16. Example: Beam model Walls Shear Max moment
The panel is raktangular and can be considered as a beam. The beam has 3 supports. The horizontal load is distributed equally to the three walls (Ithere are no walls vertically to the load because of equilibrium)
Walls
Shear
Max moment
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17. Eksempel: Bjælkemodellen
Trækarmering. Normalt kaldet stringerarmering:
Choice: 1 Y8 med et As=50mm2.
Beware: robustness might increase the area of the reinforcement!
Shear:
Okay. No need for shear force reinforcement!
robustness might increase the area of the reinforcement!
L<2zcotθ → 10m<2*0,8*8*2,5=32m
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18. Intro - Stringermetoden
As an alternativ to the beam model the stringer method can be use.
Devide the building up in zones. The zones are shear zones and are inclosed by a stringer in tension or in compression.
Se betonkonstruktioner kap. 12
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19. Assignment- Etageadskillelser
How can you design the deck panel in case A and B according to the beam model? A
Stability walls B
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20. The deck panel – Stringer method vs. Beam model
Easy to apply and use for simple cases
You might have to divide the deck panel up into smaller beams
Stringer method
The method is a bit more complicated but god is you have a structure with a allot of holes.
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21. Project
Can you use the beam model?
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22. Næste gang – Forankring af gavl
Ved bygninger med bærende facader skal det sikres at gavlen er forankret til etageadskillelsen. Ikke altid nødvendigt med bøjler!
Det/de yderste dækelement virker som en bjælke, og skal derfor altid designes i ”fuld” bredde. Dvs. evt. paselement placeres længere inde i bygningen.
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23. Næste gang – Støbeskel
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