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Dear friends, I have resigned from my position at Bahria Town. This position is open now. Any interested candidate with structural design experience of 5 years and plus may apply. Send your cv's to Senior Structural Engineer Ch. Muhammad Amin amin.bahriatown@gmail.com, Structural Engineer, Muhammad Bilal Afzal Virk bilal.bahriatown@gmail.com, Department Head Brig(Rtd.) Tarique Mehmood tarique.bahriatown@gmail.com Ask anything if you like to. Regards

I have worked with some engineers that like to assign high stiffness modifiers to rafts to get conservative flexural and shear design of foundation. Assigning modifiers would increase amount of rebar in your raft. I personally think that this is good practice as nothing is perfectly rigid and cracking in inevitable, which would result in loss of inertia and high flexural stresses. The general procedure is to create two models. One with no stiffness modifiers and one with modifiers for foundation/ raft. You should use the first model to calculate piles reactions and the second to do flexural and shear design. Thanks.

Changes in ACI 318 Anchorage Concrete Seismic.pdf

The reinforcement is given in Av/s (in2/ft) in my case. I use the formula Ab / (Av/s) x12 = spacing in inches. Ab = area of stirrup bar x no; of legs

Some general concepts, regarding shear reinforcement output of ETABS, are discussed in following thread: http://www.sepakistan.com/topic/1584-shear-reinforcement-in-etabs/ In your case for IS 456-2000 code, the shear reinforcement value should be in 'mm2/m' units. You may verify this manually, using critical shear force values of relevant members (beam or columns) output by ETABS. To provide required shear reinforcement, select a suitable rebar size (e.g., 10 or 12 mm diameter) and calculate required bar spacing as per normal procedure per IS 456. Shear reinforcement may be higher for a cantilever beam (compared to a beam supported at both ends), as all the shear force of a cantilever beam is transferred to a single support (instead of of two supports as for a beam supported on two supports). You may check & verify this from the shear force diagrams of the two beams. HTH