Pukao
Civil/Environmental
- Oct 24, 2022
- 4
Hi everyone,
I am working on the design of a simply supported concrete deck spanning approximately 7m. The deck will have a width of around 10m. A series of service ducts will also run along the span of the deck, and the requirement is for these ducts to be embedded within the concrete, effectively creating a void. The plan is for the deck to be constructed from reinforced concrete planks (300mm thick) with an in-situ topping (300mm below and 300mm above the ducts). The structure spans over water, hence why planks are used as permanent formwork.
Putting aside the fact that the structural concept could be optimized to use less concrete, I would be interested to know how others would approach the analytical modeling of this deck. My plan was to develop a grillage model following Hambly´s methodology for orthotropic slab decks, as follows:
If the attached represented a longitudinal grillage member, the longitudinal bending stiffness, Ix, would be equal to bh^3/12, where b is the width of the beam and h is the thickness of the in-situ above and below the ducts (the area with red hatching is discounted), including the thickness of the planks. In the transverse direction, the bending stiffness, Iy, would again be equal to bh^3/12, but this time h would just be equal to the thickness of the in-situ above and below the ducts, since the planks only span in the longitudinal direction.
Then, according to Hambly, the torsional constant, c, in the longitudinal and the transverse directions is the same, using expression c=2*sqrt(Ix*Iy).
Many thanks and looking forward to hearing your ideas!
Pukao
I am working on the design of a simply supported concrete deck spanning approximately 7m. The deck will have a width of around 10m. A series of service ducts will also run along the span of the deck, and the requirement is for these ducts to be embedded within the concrete, effectively creating a void. The plan is for the deck to be constructed from reinforced concrete planks (300mm thick) with an in-situ topping (300mm below and 300mm above the ducts). The structure spans over water, hence why planks are used as permanent formwork.
Putting aside the fact that the structural concept could be optimized to use less concrete, I would be interested to know how others would approach the analytical modeling of this deck. My plan was to develop a grillage model following Hambly´s methodology for orthotropic slab decks, as follows:
If the attached represented a longitudinal grillage member, the longitudinal bending stiffness, Ix, would be equal to bh^3/12, where b is the width of the beam and h is the thickness of the in-situ above and below the ducts (the area with red hatching is discounted), including the thickness of the planks. In the transverse direction, the bending stiffness, Iy, would again be equal to bh^3/12, but this time h would just be equal to the thickness of the in-situ above and below the ducts, since the planks only span in the longitudinal direction.
Then, according to Hambly, the torsional constant, c, in the longitudinal and the transverse directions is the same, using expression c=2*sqrt(Ix*Iy).
Many thanks and looking forward to hearing your ideas!
Pukao
