A Majetich's Communities Activities

Floor Load Generation Error - Complex 3D Quadrilaterals

A Majetich — Wed, 19 Jul 2023 13:46:33 GMT

I am modeling a 3d steel truss/frame pedestrian bridge and am running into an issue with the floor load command. Every time I try to apply floor loads to a group I have entitled "DECK" (see attached Command File) I receive an error stating that "Cannot Generate Load for Command".

I have made several attempts to resolve this issue by adjusting the X, Y, and Z ranges for the floor load command or by creating a "TEST" group of only one panel. I still receive the same error or it will only model on a panel in the middle of the span (not the panel in the TEST group).

Any guidance is much appreciated.

communities.bentley.com/.../Pedestrian-Bridge-Model.txt

Uniform Load Specification Bug

Nicholas Miller — Mon, 01 Apr 2019 17:25:45 GMT

I would like to post this to let the developers and others know about a little issue I recently found regarding uniform loads. This issue should not affect many people and I am honestly not sure why one of our previous engineers did this, but I've found it nonetheless and it could certainly cause an issue for others as well.

Take the example case below with the key line underlined

STAAD SPACE
START JOB INFORMATION
ENGINEER DATE 01-Apr-19
END JOB INFORMATION
INPUT WIDTH 79
UNIT FEET KIP
JOINT COORDINATES
1 0 0 0; 2 10 0 0;
MEMBER INCIDENCES
1 1 2;
DEFINE MATERIAL START
ISOTROPIC STEEL
E 4.176e+006
POISSON 0.3
DENSITY 0.489024
ALPHA 6e-006
DAMP 0.03
TYPE STEEL
STRENGTH FY 5184 FU 8352 RY 1.5 RT 1.2
END DEFINE MATERIAL
MEMBER PROPERTY AMERICAN
1 TABLE ST W6X20
CONSTANTS
MATERIAL STEEL ALL
SUPPORTS
1 2 FIXED
LOAD 1 LOADTYPE None TITLE LOAD CASE 1
SELFWEIGHT Y -1
MEMBER LOAD
1 UNI GY -0.08 0 0 2
1 UNI GY -0.04
PERFORM ANALYSIS
FINISH

One will get an error message saying that this line will be ignored in either V8i and Connect Edition. The user can run the code though and achieve a solution though without further modification. However, run a copy of the code with the line commented out and you will get a different answer. In fact, you will find that the member load has been applied along the full length of the member.

As you can imagine, I was surprised to find a model done by a previous engineer that had used this odd specification, which essentially translates to a point load of zero magnitude if you follow the documentation on syntax for the command. I suppose it could potentially be confused by someone that this could be equivalent to a 0.08kip point load... Either way though, the output will not match the expectation of the user based on the error message or the documentation on syntax and I feel like this represents an error/bug that should be addressed. To avoid confusion I think that this zero length uniform load specification should not be allowed (as the error message seems to imply), but I suppose that is for the developers to decide.

Design of a Freestanding Wall in RAM Elements

A Majetich — Thu, 10 Oct 2019 14:23:35 GMT

Hello,

I am currently using RAM Elements to model a freestanding, CMU wall (i.e. acts as a cantilever). I have modeled the wall as a shell with a continuous fixed support at the bottom. However, when I send the wall to the Masonry Module it shows that there are pinned level restraints at the top. The level restraints option is locked within the module. Is there anyway to release the nodes at the top in the main modeler of RAM Elements? Or do I have to design the wall using the Stand Alone option?

Thank you for your assistance!

See attached some photos below of the wall for reference:

Zero Thickness of Combined Footing in STAAD Foundation Advanced

A Majetich — Wed, 15 May 2019 19:31:08 GMT

Hello,

I am trying to design a combined footing for a concrete column and shear wall that act on the same footing.

The size of the footing is 6 ft x 15.5 ft x 2.5 ft.

The concrete column is 16 in. by 16 in. and the shear wall is 48 in. by 16 in. They are spaced 10'-08" on center from each other.

The column only has axial reactions and the shear wall has axial, shear and moment due to dead, live, roof live, and wind loading. Service load combinations were used (ASD combinations from ASCE 7-10).

I set up the job as combined footing ACI 318011 and listed my supports as a strip footing.

When I analyze the design it gives me a width and length for the footing but never a thickness (depth of footing) or any of the reinforcement needed. I have tried a combination of parameters as well as the "calculate dimensions" and "set dimensions" option.

I am at a loss of why the program is not outputting a thickness or reinforcement for the footing when it calculates the results.

Fatigue Analysis of Steel Plates due to AASHTO Live Loads

A Majetich — Fri, 13 Jul 2018 14:48:57 GMT

Hello,

I am currently working on a unique steel plate design to be used for a very minor lane widening on a bridge. This steel plate design is not an orthotropic steel bridge deck design.

However, AASHTO LRFD Bridge Specifications suggests for unique components and details that a refined analysis be used (but this complicates determination of force effects).

The model I have created is a Finite Element Model with fine plate element meshing around areas of concern (i.e. where plates and stiffeners meet).

I am currently doing a fatigue analysis due to live loads on the model, however I am having trouble understanding which stress outputs I should be using to calculate the fatigue stress range on my plate elements.

STAAD.Pro offers numerous stress type outputs: Max Absolute, Tresca, Von Mis, Membrane Stress (on local axises), Bending Stresses, and Shear Stresses (both in plane and out of plane).

Currently, based on the nominal stress approach, I am using the combined stress effects (membrane plus bending about local axises) to calculate the fatigue stress ranges. However, I wanted to make sure this was correct or if STAAD had a better way of determining fatigue evaluation.

Additionally, does STAAD.Pro treat connections between plates that are at an angle as welded joints? If so, does STAAD apply a stress concentration effect?

Thank you for your assistance.

Trouble with Assigning Wind Loads and Determining How the Resulting Nodal Loads are calculated

A Majetich — Fri, 22 Jun 2018 17:27:59 GMT

Hello,

I am working on a model involving Moment Frames connected by bracing (tension member only) and purlins.

I have generated a Wind Definition and intensities using the ASCE option. I have also assigned this wind load to a Group of Members (not using a X, Y, or Z range) to ensure that the wind load is only acting on the columns of the moment frame and not the bracing or the purlins. (I am more interested in the support reactions than I am in the stresses developed in the beams etc.)

When I view the resulting nodal loads from the wind load I am unsure of how STAAD obtained those values. I estimated the tributary area for a node and multiplied it by the corresponding intensities to find the nodal load. However, my calculation is two to three times greater than the nodal load value in STAAD.

Does STAAD have an option to demonstrate how it obtained the Nodal Load?

Or is there a way for STAAD to distribute the Wind Load as uniformly distributed loads on the members instead of the nodes?

Your assistance is greatly appreciated.

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Fri, 22 Jun 2018 00:50:45 GMT

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