Section Check

[Anonymous]

Hi,

I have a steel truss structure model, and the section check for the upper and lower chords are too large, 

please, can anyone help me to find the idea which gives this huge result,

note the span of the truss is 20 m and the section must be in the logical range,

Best regards,

[Simau]

@Anonymous 

Zip and upload your model

[Anonymous]

Dear Simau, 

I have attached the model,

Note that the section of the upper and lower chord of the truss are too large due to the wind load in the X direction,

but logically the critical wind must be in the Y direction, 

there isn't any release of the upper bars but the lower bars are released for RY, can you please check it also ?

Best regards,

[Rafacascudo]

Did you assign the code parameters ( member type)to all the bars?

[Anonymous]

yes, I assigned the code parameters for all bars,

Note that I named the code parameters for each bar as the bar name,

Kindly check it from the model and advise me,

[Simau]

Hi @Anonymous 

Your current structure is not stable (huge desplasments):
columns released and truss relesead over columns, then no portal effect
absence of Bracing on the roof.
Lower chord not really secured against out of plan buckling.

Look at these screenshots and new parameters of  bars type in the model attached.

[Simau]

with the model

[Anonymous]

thank you a lot,

Can you send the file as robot 2018 ? the model doesn't open on my PC

[Simau]

Sorry,

2018 is no longer installed here.

There is no change except the parameters of the upper and lower chord type

[Anonymous]

the buckling length y for the lower chord must be 0.1 L, right?

[Simau · Accepted solution]

No

1/20 of the total length in y direction and 1/4 in z direction. 

[Anonymous]

thank you a lot, I will correct it,

The last question, how the end gable columns transfer the wind load in Y direction (long direction) without any connection between the end gable column and the bracing? (based on your comment to put the bracing at the upper chord level).

 Should I extend the end gable column bars to the top of the truss? 

[Simau · Accepted solution]

Correct

The upper part of the column will be a part of the truss

[Anonymous]

How to solve the member stability check problem in the attached picture?

and should I delete the release for the columns? 

[Simau]

Change the local axis of all lower chords so that that  z axis is pointing horizontally

[Anonymous]

Why should I change the Z direction?

the robot takes the Z direction based on the weak inertia direction.

If I rotate the local axes for the lower bars, I must change the buckling coefficient in the code parameter, right?

[Simau]

By changing local axis you'll put the strong inertia where the buckling length is bigger and then reduce the kyz coefficient.

Don't change anything in the code parameter

[Anonymous]

Dear Simau,

How can I define the release in the attached picture?

Note that I delete all the releases for the lower chord, upper chord, and columns.

I suppose that the connection between the columns and beams is a welded connection, so can I said that the connections can support the RX, RY, and RY?

Best regards,

[Simau]

@Anonymous 

Difficult to answer without showing other releases in the whole structure.

Attach  your model

[Anonymous]

Note that I take all your comments to edit my model, so thank you very much for your help,

I will attach the model as per your request,