Combined Shear and Torsion - Compression field method
Combined Shear and Torsion - Compression field method
(OP)
In earlier versions (pre 2005) of AASHTO LFRD Bridge Design Specifications, torsion was included in the determination of beta and theta in the "resistance" equations for epsilon_s. In the most recent Bridge Specs (2012), torsion was not included in the calculation of epsilon_s (Eqs 5.8.3.4.2-1, 5.8.3.4.2-2 and 5.8.3.4.2-3). However, in the current Canadian Standard, also using compression field method, torsion was included in similar equations.
Why are these two standards, both using the same method, treating combined shear and torsion differently ?
Why are these two standards, both using the same method, treating combined shear and torsion differently ?





RE: Combined Shear and Torsion - Compression field method
Both Canadian and US have sections on combined Shear and Torsion as well as you probably know.
HTH
VoD
RE: Combined Shear and Torsion - Compression field method
RE: Combined Shear and Torsion - Compression field method
krex.k-state.edu/dspace/handle/2097/7011
CSA S6 Cl.8.9.3.19 formula appears on page 24.
VoD
RE: Combined Shear and Torsion - Compression field method
In Canadian CHDBC 2006, Clause 8.9.3.19 requires the shear contribution to be included in the calculation of the longitudinal strain. In AASHTO 2012 (6th Edn), the commentary on page 5-59 states "A stress limit for principal tension at the neutral axis in the web was added in 2004. This check requires shear demand, and not the resistance, to be modified for torsion". This seems to suggest that the shear contribution from torsion is not to be considered in the calculation of the longitudinal strain in AASHTO 2012. I have also come across an example from an American road authority for a bridge related structure which show shear contribution not included in the calculation of the longitudinal strain.
The key question is:
If using AASHTO 2012 for combined shear and torsion, should the shear contribution be included in the calculation of the longitudinal strain ?