Post on 24-Jul-2015
transcript
Challenge the future
DelftUniversity ofTechnology
Modified Bond Model for shearin slabs under concentrated loads
Eva Lantsoght, Cor van der Veen, Ane de Boer
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One-way vs. two-way shear (1)
Beam shear, one-way shear Punching shear, two-way shear
• Punching shear over perimeter• Beam shear over (effective)
width
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Beam Shear Failure
• Since 1899 (Ritter)• 1955: collapse of
warehouse
• Most experiments:• Beams• Heavily reinforced• Small size• Slender (a/d ≥ 2,5)
• Basis for design codes
amount of shear experiments done
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Punching Shear Failure Categories of methods for punching shear
Shear stress Beam analogy
Strut and tie Plate theory / FEM
The nature of shear failure is still not fully understood!
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Modified Bond Model (1)
• Adapted for slabs with concentrated load close to support
• Geometry is governing as in experiments
• Determine factor that reduces capacity of “radial” strip
• Maximum load: based on sum capacity of 4 strips
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Unequal loading of strips
• Static equilibrium• v2,x reaches max before
v1,x
'1, 0.1667x c
av f d
L a
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Loads close to free edge
Edge effect: when length of strip is too small to develop loaded length lw
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Comparison to experiments
Comparison between experimental results and (a) Modified Bond Model, (b) ACI 318-11 code, (c) NEN-EN 1992-1-1:2005.
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Comparison to experiments
AVG STD COV
Vexp/VACI 2,67 1,00 37%
Vexp,EC/VR,c 1,99 0,27 13%
Pexp/PMBM 1,33 0,14 11%
• Eurocode: increasing conservativism for higher capacities• MBM: follows 45º line better
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Summary & Conclusions
• Slabs under concentrated loads • Transition between one-way and
two-way shear
• Bond Model for concentric punching shear
• Modified Bond Model corresponds well to test results
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Contact:
Eva Lantsoght
E.O.L.Lantsoght@tudelft.nl // elantsoght@usfq.edu.ec
+31(0)152787449