design load combinations 1

[lesgiu]

Hi, i am trying to design a timber truss. I have applied dead, live and wind loads.
The wind loads were not generated using staad, instead I created a load case type
wind and input there the wind loads.
After that i created the combination loads and designed the truss members.

I have noticed that staad designs using all the load cases, but i don't want staad
to use all the load case/ comb loads for designing. Is there a way to specify
which ones should be used for design only/

I've been looking where to specify that but without luck

any help???

thanks in advance

Leslie

 

[structuresguy]

After you specify the perform analysis command, you can add a command called "load list" and then list out the number of the load cases/combos that you want the design to utilize. It will still perform analysis for all cases/combos, but will limit design to those that you specify.

Here is an example of what i mean

perform analysis
load list 1 2
(steel design parameters and run design)
load list 3 4
(concrete design parameters and run design)

This way, different materials can easily be designed for different load combinations (ASD vs LRFD, for example) in the same analysis run.

Here is excerpt from staad manual:

5.39 Load List Specification

Purpose

This command allows specification of a set of active load cases. All load cases made active by this command remain active until a new load list is specified.

Description

This command is used to activate the load cases listed in this command and, in a sense, deactivate all other load cases not listed in this command. In other words, the loads listed are used for printing output and in design for performing the specified calculations. When the PERFORM ANALYSIS command is used, the program internally uses all load cases, regardless of LOAD LIST command, except after a CHANGE command. In these two cases, the LOAD LIST command allows the program to perform analysis only on those loads in the list. If the LOAD LIST command is never used, the program will assume all load cases to be active.

Example

LOAD LIST ALL
PRINT MEMBER FORCES
LOAD LIST 1 3
PRINT SUPPORT REACTIONS
CHECK CODE ALL

In this example, member forces will be printed for all load cases, whereas loading 1 and 3 will be used for printing support reactions and code-checking of all members.

Notes

The LOAD LIST command may be used for multiple analyses situations when an analysis needs to be performed with a selected set of load cases only. All load cases are automatically active before a first CHANGE command is used.

After a CHANGE command has been used anywhere in the data, it is good practice to specify the LOAD LIST command after an ANALYSIS command and before the next command; otherwise only the last case analyzed may be used in the design.

Do not enter this command within the loads data (from the first Load command in an analysis set to the associated Analysis command).

 

[lesgiu]

Thanks structuresguy, i will try your example .