FAQ

What is ATENA?

ATENA is a totally new generation of our program SBETA. ATENA is a fully windows program with integrated pre- post-processing and finite element solution. The post-processing and pre-processing is improved significantly. In addition, it contains many new materials, solution methods and other capabilites as for instance options for 3D, plane strain, axi-symmetrical analysis or shell elements. You can learn more about ATENA on our ATENA page. The name ATENA is an abbreviation for Advanced Tool for Engineering Nonlinear Analysis.

Can I analyze 3D structures with ATENA?

Yes, the new version ATENA V4 can be used to analyse 3D structures in a native graphical environment. In addition part of standard ATENA installation are scripts for interfacing the ATENA software with several general purpose finite element pre and post-processors: GID and FEMAP version 7.

What is SBETA?

SBETA was our very first product developed in 80's for DOS operating system. It was a first user friendly non-linear FE software package on the market for non-linear finite element analysis of concrete and reinforced concrete structures. It could have been used to analyse beams, walls, reinforcing details and all other civil engineering structures, which could be idealized as two-dimensional problems.

I plan to buy a new PC to run ATENA on it, what do you recommend?

First of all, we have to warn against integrated graphics systems (e.g., Intel 965) - the OpenGL drivers are often that bad, that normal use of ATENA, GiD, or CAD in general is not possible. We recommend videocards targeted for CAD users (e.g., nVidia FX series, ATI FireGL/FirePro series). "Game cards" work with small restrictions in most cases (see Known issues or "KNOWN PROBLEMS" in Readme).

Up to now, ATENA can only use max. 2GB (as all 32bit programs, also in 64bit OS), therefore we recommend 2-3GB RAM for single-core processors, but nowadays, dual- or quad-core processors make more sense anyway. One can then run 1 (or 3) analyses simultaneously and prepare or posprocess another model at the same time. Attention has to be paid to the memory access speed - with dual channel Chipsets one has to have identical modules in the corresponding slot pairs, otherwise the system can slow down a lot (we have once had a quad-core with mixed memory modules and 2 analyses at a time were already slowed down by waiting for the memory, after upgrading to 4x 2GB four analyses run nicely).

The fastest and most expensive processors do not pay off in most cases, but the cheap models (Celeron from Intel and similar from Amd) are generally not good for numerical tasks (slow FPU, small cache).

Finally, of course, please do not forget that reducing the model as much as possible, like using symmetry (only modelling 1/2, 1/4 or 1/8, or even 2D or rotational symmetry when possible), "smart" meshing (only refined where needed), etc., usually make much more difference in the analysis running time than different computers.

How to model carbon or glass fibre wrap (CFRP, GFRP) strengthening in ATENA?

Adding a thin layer of epoxy (or glue or similar) containing directional carbon (or glass or other) fibres into a model requires special attention. With tetrahedral (or any other volume elements) the thin layers would need a lot of elements (imagine just 4 elements per the FRP layer thickness and 4:1 aspect ratio!). We think this modelling would not be feasible with today's computers...

A better option is to model the CFs as discrete bars at/near the concrete surface. About 2 bars per element (with the area corresponding to the total CF crossection area per the concrete element width) should be enough. However, it is not possible to capture debonding/delamination with this modelling.

Therefore, we recommend using shell elements for the wraps. Then, you can model the interface between the concrete and the wrap using contact (GAP) elements. You assign the properties of the matrix material (epoxy, glue; elastic modelling is often enough) to the shell volume, and add the fibres (usually, a trilinear working diagram is enough to capture the behaviour of the fibres) as reinforcement layers, a layer for each fibre direction.

Please see the Shell elements description in the Manual. Here, only the most important settings are summarized:

1. For all macroelements that use shell/plate elements, the following has to be set:
1.1. "quadratic" in FE mesh - Generation
and
1.2. "brick" in FE mesh - Macroelements

2. For pure tension, a 3-4-layered shell is enough, for setups where bending of the shell has influence, usually 6-10-layered shells are needed to get accurate results.

3. Please pay attention to the wrapped edges - the best connection at edges is a 45 degrees (or a different corresponding angle if the thicknesses are not the same, see the figures in the manual).
It should not matter which surface is top and which bottom, the important thing is that the thickness is defined in the right direction (the smallest one), and as long as the top and bottom surfaces are parallel, both give correct result. However, in corners where 2 FRP elements are connected, I would recommend that these have both the same orientation, i.e., both have "top" to the beam or both "bottom" to the beam.
Additionally, if one defines reinforcement layers in different depths of the shells, it makes sense to have consistent orientation such that the distances from top/bottom have the same meaning everywhere.

Frequent problems with ATENA

If you have a problem with ATENA, you may find the answer in ATENA known issues