chapter 11 design of beams (sections 1 and 2). recall, with beams we have two stresses to deal with,...
TRANSCRIPT
Chapter 11 Design of Beams (Sections 1 and 2)
Recall, with beams we have two stresses to deal with, normal stress, , and shear stress,
How are the design of these beams different???
Beam Recap:
• Beams are structural members designed to support loads applied perpendicular to longitudinal axis.
• Must be sized adequatly to reduce both shear stress and bending stress as well as shear flow if beam fabricated with fasteners!– Shear stress – issue with wooden beams,
short beams, beams with narrow sections (small t) or glued beams.
Beam Recap Cont’d”
– Bending stress – generally the stress designed to. Especially for long beams, steel beams, etc.
– Recall:
I
Mcmax
Let S = section modulus = I/c, then:
allowdreq
MS
'
Beam Design Summary:
• Find shear and moment diagram – get Vmax and Mmax. Determine material and type of beam.
• Calculate required section modulus using:
• Calculate max shear stress to make sure ok:
allowdreq
MS
'
allowIt
VQ
Optional: If fabricated with fasteners determine fastener spacing S =Fsd/q
If glued, calculate shear stress at glue joint to make sure ok!
Design Cross-Section!!!!
EXAMPLES:
