ROBOT2009_2011 DYNAMICS ANALYSIS PROBLEMS

[falconado]

Hi dear friends,

robot 2011 do not true dynamic analysis ,if assign to floor rigid diaphfram property. i have tested more times. finnaly i decided not using rigid diaphrame because robot have a bug this subject. use slab as shell in dynamic analysis.

best regards.

[ksminh]

i see . when i define property of slabs with rigid diaphfram . i can not mesh it . but when i assign slabs with shell property be can mesh it very ok . why like that??? i do not understans ??? if i can not mesh slabs with rigid diaphram , when i analysis stress and force for beam , column ans slabs is not true . can you explaint it . thanks so much

[zipatton]

Hi,

it means that Robot is poor for dynamic analysis. In fact Robot is good for making linear analysis (static) for simple structures, design of beams, columns and give detailing. But it is not a great software for those who have to make complex projects. You rather take SAP2K. That's another world.

Best regards

Zipatt

[mecheil.edwar]

Hi dear friends,

robot 2011 do not true dynamic analysis ,if assign to floor rigid diaphfram property. i have tested more times. finnaly i decided not using rigid diaphrame because robot have a bug this subject. use slab as shell in dynamic analysis.

best regards.
----------------------------------------------------
Hi Falconado
I think now most of users agreee that there is a fatal mistake for Response spectrum analysis with Robot specially with Rigid links or Rigid Diaphragms.
Hoping the developers will support these Bugs

[giga]

Relax Guys, Relax

I read your experiences and suggestions about problems, warnings and many things about robot.
Unfornately i must say that almost of them are NOT true.
I read something about instability types, errors on rigid diaphragms, and many many things, and i must sa that instabilityes are not errors of program but are modeling mistakes and staticly instabilyties at structures given by user, ( you can reed manual of robot for instability types 1,2,3 ....and reasons why)
For rigid diaphragms you must define yourself propertyes of rigid diaphragms ( not by library) and be carefully when you restraint all directions, because if you want to define inplane rigid behaviour you must restrain X and Y direction of moving compatiblity, and not Z.
I agree with you that there are many good softwares for structural analysis purpose ( like SAp, ETABS, Midas GEN or CIVIL, ......) and i agree to you that CSi is very great ( otherway with some weak points) , but also ROBOT is good for many structural analysis purpose, especially for low and middle rise RC and steel buildings.

Relax, And maybe we can discus for any point step by step

Good Work

[zipatton]

Hi everybody,

I used Robot in the past and now I use SAP2k and ETABS. The difference :

1 - Very clear documentation with CSI. Confused with Robot.
2 - Clear error messages with CSI, confused with Robot
3 - Fast analysis with CSI. Erratic with Robot.

May be Robot is good for treatment but ease of use (wich is a part of safety use, isn'it?) is not safe with it. I feel that a lot of intelligence is embarked in CSI software. In Robot, it is honest, no more.

Hey, i am an old engineer of 51 years old.

Best regards

Zipatt.

[TAFATNEB]

My first reaction to introduce the concept of the diaphragm was the manual approach, similar to the concept introduced with the software sap80,
after its introduction and comparison of its results with the STAADPRO, ETABS, SAP2000, I would note that the results were not similar.
but the introduction of the concept of the diaphragm with "membrane" specified by the robot fights, we find the same results of "dynamic analysis.

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I hope Autodesk won't spoil it. Since their having bought Robot from RoboBAT, they did absolutely nothing to improve the software.
The Robot's strongest point is the very convenient user interface. I would recommend it for all FEA tasks, and it is especially suitable for steel design.

[giga]

@TAFATNEB
Which type of diaphragm are you using
If you use diafragm i prefer you to create an user defined diafragm property, and in option RIGID CONNECTION OF NODES FOR THE SLAB dont chose full stiffering.

Otherwise every type of panel ( shell or diafragm) are not increase the speed of system solutions at robot.

I agree to you that best way is to use shell model for panels.

regards

[TAFATNEB]

the "kinematic aspect of the concept of infinitely rigid floor is universal.
the horizontal plane of the floor is XY. Definition of the diaphragm means liberation from the floor along X and Y and rotation around Z.
if you introduced this concept with the robot, the results will be inaccurate and not comparable with other software .

I made several significant projects with Robot - lightweight steel pavillions, concrete frames, retrofit of old industrial cast-in-situ RC building etc. ....

but from the 2009 version, I avoid using it especially when I make a dynamic study of a reinforced concrete structure with WALLS.

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but from the 2009 version, I avoid using it especially when I make a dynamic study of a reinforced concrete structure with WALL.

kinematic aspects of diapgragm is universal, if the floor is in the XY plane, the definition of infinitely rigid floor results in the liberation of the degree of freedom along the X and Y axes and rotation around the "vertical axis Z .
if we introduce this concept into account this defintion, the software robotbat gives erroneous results.

[giga]

Carefully
If you use full rigidity dafragm in robot you have assign same X, Y, Z, displacements and X,Y,Z rotations to be same for all nodes in panel which is asumed to behave like as rigid diafragm.

Can you explain what kind of results are not matching