Hi everyone,
Regarding wind case, I have Load case set up as

LC 4 OPE case

LC 13 OPE + win1
LC 14 OPE + win2
LC 15 OPE + win3
LC 16 OPE + win4

LC 35 Pure win1 (Alg)
LC 36 Pure win2 (Alg)
LC 37 Pure win3 (Alg)
LC 38 Pure win4 (Alg)

LC 39 Max 35,36 (Max)
LC 40 Max 37,38 (Max)
LC 41 39,40 SRSS (SRSS)

THen
Sus + 35 (Scalar)
Sus + 36 (Scalar)
Sus + 37 (Scalar)
Sus + 38 (Scalar)
Sus + 39 (Scalar)
Sus + 40 (Scalar)
Sus + 41 (Scalar)


My question is,

When we use 'srss', it gives false displacement. Means if at some location, -z restraint (axial direction) with 0 mm gap is given & has disp say -8 mm in z, while calculating srss '-' sign is gone & produces disp in + ve Z which is false due to - z restraint.

I've checked the system & the above is found correct. Moreoevr the failure is at only one point as a result of the above said false displacement in case no. 41 only.

Please tell me if the above understanding is correct & if so can I ignore/delete srss case, since rest of the part is safe even with the use of srss, which is on a conservative side.

Friends any opinion please!

My opinion is you do not provide enough background to allow more thoughtful opinions.
For example, must we assume that WIN1 & WIN2 are +X and -X and WIN3 & WIN4 are +Z and -Z? Must we assume that PURE WIN1 = (OPERATING+WIN1)-(OPERATING)?
And must we assume that your Engineering Design Specification requires you to build your occasional load case from the worst values for each wind direction combined by SRSS?

Hello Mr. Dave,
Thank you for the reply & sorry for incomplete information.

Yes, your assumptions are correct.
1. WIN1 & WIN2 are +X and -X and WIN3 & WIN4 are +Z and -Z
2. PURE WIN1 = (OPERATING+WIN1)-(OPERATING) i.e. (LC 13- LC 4) & so on.

Regarding Engineering Design Specification, it just says "Wind loads to be calculated as per procedures in ASCE 7-05."
Nothing else is specified about load cases to be taken or anything else.

The site location is in Hurricane prone region (3 sec gust at 52 m/sec above 10m from grade level )with

Importance factor 1.15
Wind Exposure Category as 'C'
Structural Classification Category III

Topographic Parameters
Height of Hill /Escarpment = 0 m
Crest Dist = 0 m
Distance from crest to site= 0 m
Hill type = No Hill

In this situation, is it mandatory to have SRSS combination? I mean, it is typically used for seismic calculation.
In my case there is problem only at one location, which I think is because of the +ve (which is false) displacement.

Please suggest.
Thank you.

You quote ASCE 7 for your design wind load magnitude, perhaps you could also use ASCE 7 for application.
ASCE 7-05 provides load sets for Main Wind-Force Resisting Systems (certainly NOT piping systems) in Figure 6-9. That figure shows full wind load along each principal axis - separately. Then also shows both horizontal loads together BUT using 75% of the design load, and these perpendicular loads are applied simultaneous, not SRSS.
So once again, it would be nice if you had a clear statement of load application in your engineering design specification.