1800 x 600 wide RC Beam - Deflection
1800 x 600 wide RC Beam - Deflection
(OP)
Iam currently designing a 10 storey reinforced concrete building to be located in a highly active seismic zone with around 0.35g. Today iam looking closely at a RC transverse beam loaded with a structural 200 series blockwall above it at the carpark on the 2nd floor. The client wants to maximise parking hence the depth to my beam is limited to 600mm deep and columns limited to 300mm wide!
Im experiencing problems with long term deflections. I came up with a beam 1200wide x600 mm deep for my ultimate limit bending strength. However, deflection fails so i have to bump up the size to 1800 x 600mm to accomodate for deflection. My span is 10 metres. Whats the best thing to do in this case?
Im experiencing problems with long term deflections. I came up with a beam 1200wide x600 mm deep for my ultimate limit bending strength. However, deflection fails so i have to bump up the size to 1800 x 600mm to accomodate for deflection. My span is 10 metres. Whats the best thing to do in this case?






RE: 1800 x 600 wide RC Beam - Deflection
RE: 1800 x 600 wide RC Beam - Deflection
RE: 1800 x 600 wide RC Beam - Deflection
Dik
RE: 1800 x 600 wide RC Beam - Deflection
AUCE98
RE: 1800 x 600 wide RC Beam - Deflection
dik
RE: 1800 x 600 wide RC Beam - Deflection
For your span of 10m (32.8 ft) the 600mm (23.6 in.) depth seems adequate. For simple span concrete beams, the minimum depth required so as to not have to check deflections is L/16 = 625mm (24.6 inches).
Usually, if you have deflection problems in concrete beams you can either
1. Deepen the beam
2. Widen the beam
3. Add reinforcing in the tension zone (i.e. increase effective moment of inertia, Ie)
4. Find ways to redirect the load on the beam to other structural members or load paths (i.e. dik's suggestion to use the wall).
Be sure to take advantage of any monolithic slab flanges.
Also, for long term deflections, you can add steel in the compression zone to reduce long term creep.
RE: 1800 x 600 wide RC Beam - Deflection
By my calculations, increasing the width to 1800 would only reduce the deflections by about 15%.
You could put in 4 times the amount of bottom reinforcement you need for strength and an equivalent amount of top reinforcement and you will get the deflections down enough (assuming I have modelled something similar to what you have briefly defined)
If you want to rely on the wall spanning by itself, make sure you reinforce the bottom of it to make sure it can span by itself and that noone is going to want to cut holes at the bottom of the wall in the future.
It may be easier to just fill the cores and reinfroce the wall and even supply starters out of the slab into the wall.
RE: 1800 x 600 wide RC Beam - Deflection
RE: 1800 x 600 wide RC Beam - Deflection
RE: 1800 x 600 wide RC Beam - Deflection
Concrete compressive strength to be used is 40Mpa. All reinforcement bars yield strength fsy= 500Mpa. Stirrup(ligs, fitments in other words) will be R12 bars.