P-DELTA Analysis in ETABS 2017 including respose spectrum analysis

1. Define a new load case "PDELTA".

2. Set it to start from zero condition.

3. Assign load names that will act as vertical forces when lateral sway occurs i.e usually DL + some factor*live loads.

4. Set Geometric non linearity to P-Delta

OK

Now for the load cases that you want to act once p-delta occurs set the initial conditions to "Continue from state at End of Non linear ..." where you will find the initially defined "PDELTA".

If you want to do response spectrum analysis. You need to create a new modal load case "PDMODE" and do same as above. Then in RSX and RSY load case assign modal case to PDMODE.

In concrete design do not forget to include P-DELTA in view/revise preferences.

Equilibrium and Compatibility Torsion

I shall directly talk with an example. Imagine a horizontal cantilever slab on a beam. The beam is subjected to torsion. Let us now release the the beam end connections in torsional direction or imagine it like the beam is a wheel and axle system. We see that the slab immediately falls or rotates about the beam axis and hangs on it vertically. It is because the beam is unable to resist the torsion due to slab. This kind of torsion is equilibrium torsion.

Now take a 4 edge discontinuous slab. The edge beams are again subjected to torsion. Once again consider the beams  to be of wheel and axle system i.e all the torsional degree of freedom are released. We see that the end beam rotates for some angle but the beam/slab system doesn't collapse like in previous case. The equilibrium is still maintained. So this kind of torsion when the joints were not released is compatibility torsion.

unfinished(black) bolts vs finished bolts from BC punima

Unfinished(black) bolts vs finished (turned and fitted) bolts from BC punima

Torsion reduction in beams.

It's hidden in clause 11.5.2 in ACI318-08 (presumably the same in 2011 version) if you read between the lines. 

Equations representing stress strain values of steel rebars.

The equations are derived by third order polynomial curve fitting of the data given in SP-16 table  in Indian code.

For Fe 250:
 y = 10802254950x3 - 47811496.7x2 + 74481.40335x + 205.8829164

For Fe 415:
y = 8634745755x3 - 84776621.6x2 + 284712.3995x + 29.42076793

For Fe 500:
y = 7949113254x3 - 89302413.2x2 + 343343.7433x - 20.40632679

Working transparent Plane not shown or visible in 3d window in sap2000 / etabs ?

Go to options and click show bounding plane.

LOAD DISTRIBUTION IN ONE WAY SLAB IN SAP2000

Sap 2000 distributes one way slab load to red colored axis direction only and not towards longer edges. So you'll have to rotate your local axis of slab such that red axis points to your longer edge.