B4. Extra Reinforcement at Corners of Two-Way Slabs at Building Edge

Code Compliance & Reference
This detail complies with HKRC2004 Clause 6.1.3.3 (d) (v) & (vi) regarding the reinforcement at retrained two-way slabs.

Comments

1. I must first say that I’ve only one consultant with this details – MINE. I’ve also seen OVE having similar details in their typical details book, but not in their submission drawings.
2. The idea is simple: add U-bars to the corners of two-way slabs at building edges. The U-bars act as torsional reinforcement to give the two-way slabs a restrained corner.
3. The code requires “the area of reinforcement ... should be three quarters of the area required for the maximum mid-span design moment in the slab”. It is not easy to ‘typical-ize’ this requirement. Hence, to make things simple, I choose to keep these U-bars same size as the mid-span reinforcement and make the spacing increased by 4/3 to that at mid-span.
4. However, for slabs with bar diameter >10mm and bar spacing >225mm, there will be some waste of steel (because I also limited the spacing to a maximum of 300mm). Well, I guess it’d be up to the designer to choose whether to specify the U-bars for each two-way slab at corners/edge of building, or just to accept a small over-provision of steel reinforcement. (Afterall, there isn’t many corners and edges for a two-ways slabs in a building)

Blog Post: Typhoon No. 8 tonight! 3 hours after the No.8 is hoisted, there are still some colleauges working in my office. Crazy.