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RE: RISA3D vs ETABS

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Paul, I am glad someone has had good experience with Etabs.  I had a few
problems with it, but there must be workarounds.

When I added a few new columns and drop panels, on a grid line, I wasn't
able to get them to connect to the slab.  I erased and recreated them
several times before they were recognised.  But I sure would like to
have confidence in Etabs.  It has a great interface.

Kevin Below


-----Original Message-----
From: Paul Feather [mailto:pfeather(--nospam--at)SE-Solutions.net] 
Sent: 10-Feb-06 12:41
To: seaint(--nospam--at)seaint.org
Subject: Re: RISA3D vs ETABS


I do not agree at all.

We use both, and we use ETABS extensively.  The fact is they are very 
different programs, and ETABS requires a higher level of sophistication
on 
the users part to ensure proper modeling and results.  ETABS is much
more 
powerful than RISA, but like any true FEA program requires cautious and 
judicious use with a clear understanding of the different elements and
what 
they are doing in the model, and how the element stiffnesses affect the 
analysis run.  RISA is more simple with "text book" analysis the way you

learned classical analysis techniques.  RISA has some very useful
features, 
and for certain types of structures and analysis may be the program of 
choice; for other types there is no question ETABS is superior.

There have been bugs in the software, but screwed up mesh and node 
incompatibility is not a program bug, it is a user bug.  I have always
found 
tech support to be very helpful, you just have to be asking the right 
questions.  Programs like ETABS take commitment on the part of the user
and 
the company that implements it.  I am sure any of the other advanced FEA

programs require an equal commitment in time and understanding.


Paul Feather PE, SE
www.SE-Solutions.net
pfeather(--nospam--at)SE-Solutions.net
----- Original Message ----- 
From: "Joseph Harouni" <jharouni(--nospam--at)sbcglobal.net>
To: "Suresh Acharya" <SAcharya(--nospam--at)ci.alameda.ca.us>; <seaint(--nospam--at)seaint.org>
Sent: Wednesday, February 08, 2006 3:30 PM
Subject: Re: RISA3D vs ETABS


> Wow, thank you for the info.
> Joseph
> On Feb 8, 2006, at 3:19 PM, Suresh Acharya wrote:
>
>> Hi Joseph,
>> I have used both RISA and ETABS until 2002.
>>
>> RISA is good at what it promises, and is simple.  But ETABS promises 
>> more than what it can do reliably.
>>
>> ETABS is full of bugs, so much that they produces patches every 
>> often. Sometime results are riddiculous. Once I found the seismic 
>> mass was wrong, although it calculated gravity reactions correctly. 
>> When plate elements are used to model concrete slabs, it can 
>> generates meshes automatically - but there is no connection between 
>> individual  meshes and the beams or girders - when you look at the 
>> mode shapes, you see they are vibrating independently.
>>
>> Modeling the main frames with ETABS is fine, as long as you verify 
>> results manually. But I would not rely on ETABS' other builit-in 
>> features which are meant to make you life easier, but in fact it may 
>> make your life miserable.
>>
>> When you call ETABS, you will be feeling that you are not talking to 
>> a structural engineer, but rather more like a programner with some 
>> engineering background. They are changing the user interface and 
>> modeling concept (except, probably the core FEA engine which was  
>> written in FORTRAN at UC Berkeley) every often that everytime is 
>> loaded  with new bugs. Besides, they are still using Visual Basic to 
>> write routines - that is the reason why it is sluggish even in new 
>> computers.
>>
>>
>>
>
>
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