preventing shear walls from carrying any lateral loads in this particular case so please help

[ayelamayem77]

Dear all
[highlight #FCE94F]my question seems to be silly !!!![/highlight] but please be patient and think with me about this rule in asce7-05 regarding dual frame system

[highlight #FCE94F](resistance to lateral forces is provided by moment-resisting frame capable of resist 25 present of the design base shear)[/highlight]

all i mean that i want to activate this rule in Etabs program, so i made a separate model and i applied 25% of total base shear, i need to design the columns under this seismic load case situation as you know the design in this particular case should be made under load combination consists of (seismic and gravity loads) as follows
(1.2d+1.0E+f1L+f2s 2006 ibc eq.16-5) & (0.9d+1.0E+1.6H 2006 ibc eq.16-7).

[highlight #FCE94F]I want to keep the shear walls in this model am taking about to support gravity loads with the columns according to their stiffness, because if i remove the shear walls the columns will be subjected to high axial loads in accordance with the seismic forces, which will lead to big columns sections when i start the design by Etabs.
In other words in most design cases in dual frame system or shear wall-frame interactive system the resent rule in asce-7-05 will governs the design of columns.[/highlight]

thanks all for your support

 

[slickdeals]

Change the f11,f22 and f12 to very small values (say 0.001) so that the shear walls don't carry any in-plane shear.

 

[ayelamayem77]

Dear slickdeals

[highlight #FCE94F]thanks allot for your concern and for your quick replay[/highlight] so i guess that you agree with me that i have to keep the shear walls , but please be aware of [highlight #FCE94F]if i changed the f22 value to a very small one the shear wall will not carry any of the gravity loads[/highlight]
so i tried to convert the shear wall section from shell to membrane and modify only f12, so in this case the shear wall will take zero shear force value, but will be capable of resisting the gravity loads, but still the analysis give me many and many warning message about (negative stiffness values) and at last the dangerous message appeared (the structure is unstable) but the previous message [highlight #FCE94F]appeared only when i activated p-delta analysis and if not no problem about warnings in the analysis log file will come[/highlight]

[highlight #FCE94F]so i have very important two questions:
1- is p-delta analysis is required when designing the columns under asce-7-05 rule (resistance to lateral forces is provided by moment-resisting frames capable of resisting at least 25 percent of the design base shear)?????
2-if p-delta is required and to avoid the previous warning messages, do i have to make the shear wall membrane section one part from the foundation to the roof (without meshing) ??[/highlight]
thanks for your concern.