After updating PVElite with 2010 release, I have the wind loads halved. I do not see any reason for that, because the wind input remained the same and I haven't changed the column.
Is there any major change in calculating the wind shear/bending in PVElite 2010?
I have to mention that I calculate according Indian Wind Code IS-875.

P.S. Looking more attentively to the output I observed that factor k2, which can be found in table 2 from IS:875 has been decreased.
For example, for Terrain Category 2, Class B the standard indicates k2=0.98 for the first 10m, while PVElite 2010 output indicates k2=0.67. This is the reason of decreased wind loads and this has begun with PVElite June 2009.
In my opinion, this is a mistake. Please confirm urgently.

Camelia,

You are correct. Previously PV Elite was conservative. It had to do with using k2 factor from table 33 if the gust effect is considered.

The k2 from table 33 for 10m and category 2 is 0.67, (page 49 of IS 875 (Part3) 1987. The wind loads from PV Elite 2010 are correct (and less conservative) as compared to PV Elite 2009. I did not except the change in loads to be different by a factor of 2.

If your vessel is sizable, you should have the box checked for "Use the Gust Response Factor". I will also suggest that you run the analysis without the gust factor (I think you should get smaller wind loads but you will see the k2 factor of 0.98 in that case).

Another thing you can do is to try using the cf factor from table 23. This is new check box that was added to PV Elite.

It is always good to review the latest software update and the build.txt file that comes with it, which has a list of major changes in it.

I hope that answers your question.

Thank you for your quick reply. I appreciate it.
Unfortunately, the specification I use indicates the wind pressures calculated with k2 from Table 2, the gust factor method and cf of 0.7. So I am stucked.

However, I have also small vertical vessels for which the factor K2 is taken from the table 2, even if the box "Use the Gust Response Factor" is checked.

I have another vessel for which k2 is neither from those tables. From 10m, k2 is 0.7008, from 15m is 0.7302 etc.

Is there an explanation for these cases?

This is puzzling, as users in India had asked for this change.

Why would they want k2 from table 2 with the gust method. To add additional conservatism,as this is not per the code. Can you check with your customer on this and let us know.

Can somebody from India respond to this, Mukesh, ...

Yes Mandeep,

I will see the issue and try to reply it tomorrow...

Mukesh
www.theculminates.com
M:+91-9428500192

Camelia,

I have checked the issue. Followings may help you.

1. About Cf: If you are using IS-875, then you must follow table:23 for Cf. Before PV Elite 2010 version this facility was not there in form of check box as said by Mandeep. You must follow value of Cf from table:23 of IS-875 Part-3 as same is higher than 0.7. Remember one thing mostly client's specifications are general.

2. About K2 : One thing you must understand that when you are using said IS Code without gust factor then value of K2 would be 0.9839 upto 10 m for Class-B, Category-2. If your geometry or client's requirement calls for gust factor consideration then check the box in PV Elite. Once you check the box then automatically it will read the value of K2 from table:33 as said by Mandeep because as per IS-875, Part-3 for gust factor method K2 value shall be from Table:33. So PV Elite is correct here.

3. About Clients Data: As I said above, mostly client's specifications are general. If you are designing without gust factor then table:2 is applicable for K2 and if you are designing with gust factor method then talbe:33 is applicable. If your Cf value from IS Code is coming higher than client's specified value then you need to follow the Code.

4. Different K2 which are not tabulated: PV Elite also interpolate values for different heights other than that tabulated in the values...
So you may not get exact values as tabulated in the IS Code.

5. Wind Loads Reduced by factor of 2: It is difficut to say that loads are reduced by factor of 2 just switching over from PV Elite 2009 to PV Elite 2010...If your gust factor check box was checked in 2009 version as well as in 2010 version then your loads would be increased with the tick on check box of "Compute Cf from table-23" as Cf is increasing form 0.7 to higher value. But Cf from table-23 is not taken then your PV Elite 2009 files is required to check the issue how loadings is reduced by a factor of 2.

Hope this clarifies your all queries.

Don't follow client's requirement blindly. Read it, think on the same and if required then ask them to change there inputs if same are conflicting with Code requirements and Code requirements are conservative.

Thanks.

Mukesh
www.theculminates.com
M:+91-9428500192

Thanks Mukesh.