beam model static analysis - cern
TRANSCRIPT
Beam model static analysis
A. CatinaccioPH-DT Engineering Office, CERN
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CERN, May 27th 2015
FEA beam model
• Standard beam model of the main portal frames,
• Loading corresponding to the unit cell equivalent loads (1.6 m pitch)
• Capability to implement the rotational stiffness at the corner joints as
extracted from the analytical models ref. 6.4.1 and the FEA sub-models ref
6.4.2.It allows as well to simulate different joint conditions, such as pinned,
and fully moment constrained.
• The FEA model is built parametrically through and ANSYS APDL script.
• BEAM189 provides a linearized stress output as part of its output record.
• The internal stainless steel membrane and supporting grid are explicitly
neglected.
• The load conditions as described in ref. 6.2.1 and 6.2.2 are combined
according to section 6.1. Material and section properties are described in
sections 3.2 - Member size and availability and 4.1 - Material characteristics
and availability.
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APDL main parameters
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Main Model Parameters:
parameter Value / units description
w 18.058 m Portal beam neutral axis width
h 16.958 m Portal beam neutral axis height
gap 0.91+1.138/2 m load offset top and bottom
lockbottom 3.8 m +/- 3.8 m vertical support from portal symmetry axis (to
avoid no pulling reaction from the floor)
po 350 mbar Gas overpressure on the top of the LAr
pitch
1.6 m Pitch between main transversal portal frames
ro
1400 kg/m3 Lar density
rotstiff 1.25E9 N m Imperfect joint rotational stiffness
ymbeam 2E11 N/m2 Material Young Modulus
wf11 0.410 m Width flange HL1100-607
wf21 0.410 m Width flange HL1100-607
hb1 1.138 m Section height HL1100-607
thf11 0.055 m Flange thickness HL1100-607
thf21 0.055 m Flange thickness HL1100-607
thw1 0.031 m Web thickness HL1100-607
Model dimensions
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The support structure (after the 10mm SS plates) shall starts at:
Internal dimensions of warm structure
Length Width Height
[mm] 63’820 16’920 15’820
Dimensions of the main transversal portal frame
Model loads
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Model boundary Conditions
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Model loading and boundary conditions
Results
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Total displacement [m]Vertical displacement [m]
Results
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Max long stress on beams [Pa]
Bending Moment diagram [N m]
Results
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Shear force diagram [N]
Normal force diagram [N]
Results
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Linearized membrane stress on beams [Pa]
Linearized membrane stress on vertical beams [Pa]
Linearized bending stress on beams [Pa]
Calculation model: portal beam
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Summary of results from the above runs:
Pressure [mbar] Vertical Deflection [mm] Lateral Deflection [mm]
350 -14.6 39
20 -17.5 30
Stresses at 350 mbar top Max VM equivalent stress Max VM equivalent stress
Value [MPa] 160 1.4
ASME verification of results from the above runs:
Stresses at 350 mbar top Max VM equivalent stress Max VM equivalent stress
Value [MPa] 160 1.4
Location Vertical beam top flange Vertical beam web
Linearized stress category Pm+Pb Pm
ASME allowable (ref. 6.1) < 1.5 S = 331 MPa < S = 220 MPa
Factor 2.06 157
It should also be mentioned that the condition Pm < S is verified in all points of the main members of the frame, where the maximum membrane stress, detected on the bottom beam is Pm = 24.4 MPa.
• Sag conservative but in favour of safety: due to extra span in modelling beam length and
height to centroid axis and from rotational stiffness treatment for corner connections.
• Selected following EC3 to obtain conservative predictions.
• Moment & force results used to design and check connections
• ASME verification OK with minimum safety factor of 2
• Eurocode 3 verification on beam bending, shear, normal force capacity OK – buckling
verification OK (with bracings).
𝑃𝑚 < 𝑆𝑃𝑚 + 𝑃𝑏 < 1.5 ∙ 𝑆
𝑃𝐿 < 1.5 ∙ 𝑆𝑃𝐿 + 𝑃𝑏 < 1.5 ∙ 𝑆 √
Material
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A note on the moment transition• The transition point of M along the vertical beam is highly affected by:
– The rotational stiffness of the bottom joint
– The position of the bottom support (or contact point)
– (The behaviour of the floor beam)
• The top pressure 20, 120, 350 mbar does not influence the transition point
• The splice joint (seen these effects) must be capable of taking Moments
and Shear with some good safety factors
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