Dear ATENA friends

Our fall newsletter brings always the information about the latest development on our ATENA software, which we strive to continuously develop in order to bring the latest achievements in the numerical modeling of reinforced concrete to your desk. The overview of the latest ATENA development is in the first part of our newsletter. It already became a nice tradition to introduce an interesting project where ATENA helped in providing deep engineering insight into the structural behavior. This time bridge engineer Niklas Bagge is sharing with you his experience in using ATENA in the investigation of a prestressed concrete bridge in Kiruna, Sweden. The project, performed at Luleå University of Technology, Sweden, nicely shows how the combination of various finite elements can result in effective nonlinear modeling of large-scale structures in ATENA. In the subsequent parts of our newsletter we would like to invite you to our training seminars, conferences and inform you about our latest publications, which we hope can be a great source of motivation and background information about new models and features.

Improved support for large scale analysis:

The analysis presented by Niklas Bagge in the success story section shows that engineers often need to effectively perform nonlinear analysis of complex and complete structural systems. In ATENA this is usually accomplished by optimal combination of beam, shell and solid elements. In the new ATENA version we have introduced new features to simplify this approach and namely to make it more effective during the model development and faster in the computational time. This namely involves the following new features:
- faster and more effective definition and detection of the contacts between the various element types, i.e. contacts "beams to solids" or "shell to solid", etc.
- improvements in the definition of complex beam profiles in GiD preprocessor

Nonlinear modeling of complete building section in ATENA software

Schematic description of the new ATENA durability and corrosion model

New models for durability and reinforcement corrosion:

The parameters of the surrounding environment can be specified as a new boundary condition. This typically includes chloride concentration, CO2 content or relative humidity. Based on this information the chloride or carbonation propagation is calculated in time taking into account the possible presence of cracks. When the propagation front reaches reinforcement, the corrosion model is activated, which results in the reduction of reinforcement area. This effect can be included in any reliability or strength assessment in ATENA calculation.

Improvements in post-processing:

The program ATENAStudio, which supports unique run-time visualization, has been extended with new post-processing and visualization features based on the requirements and input from you:

- improvements and enhancements in the visualization of diagrams of internal forces (i.e. M, N, V)
- new features for vector and tensor plots
- improvements and enhancements in the definition of user-defined color scales.

Top: reinforcement corrosion after 30 years (Nougawa bridge Japan) Bottom: single beam failure mode in ULS case after 80 years

Concrete cracking above the main support, moment evolution and deflection of a composite steel-concrete bridge analyzed by ATENA

The new version will be available to all users with valid maintenance support. Currently it is possible to download the ATENA 5.6.0 beta version from our website. Final release version will appear in this website section and in ATENA update check menu in mid November 2017. The latest official version is ATENA 5.4.1l, which is also available on our website. It contains mainly various minor improvements of problem corrections. For the detailed list of changes, see the corresponding readme file. If you need to check your maintenance status, please do not hesitate to contact us at cervenka@cervenka.cz

Also you can get motivated by the accomplishments of your colleagues with ATENA on our website of example projects, and enjoy selected ATENA nonlinear analysis videos on our YouTube Channel.

Nonlinear FE analysis for structural assessment of bridges – Experiences from failure tests of a 55 year-old PC bridge

Niklas Bagge, M.Sc., Ph.D. Department of Bridge and Hydraulic Design, WSP Sverige AB, Luleå, Sweden.

A 121.5 m long prestressed concrete girder bridge has been tested to failure in Kiruna, Sweden, with the objective to investigate its structural behaviour and ultimate load-carrying capacity. The superstructure was loaded by using bedrock-anchored hydraulic jacks, and shear-related failures were produced in both the girders and the slab (see Figure 1). Further details about the research project have been presented in [1].

Fig.1: Bridge loaded to failure.

Fig.2: FE model of the bridge for simulation of the failure test (load distribution beam and region for refined finite element sizes shown in high-resolution region).

Standard assessment methods (i.e. linear structural analysis combined with local resistance analysis) yielded very conservative estimates of the capacity; hence, the experiment was further evaluated with nonlinear FE simulations. ATENA Studio was used for the improved analysis. A 3D model was created for the entire bridge to accurately reflect the structural response (see Figure 2). However, nonlinear FE analyses of large structures are computationally demanding, and to reduce the computational effort, the bridge was modelled with different detailing (i.e. idealisation of material behaviour and discretisation by finite elements) depending on the structural part.

With high precision, the improved analysis was able to reflect the nonlinear structural response observed in the bridge test (see Figure 3), and the complex experimental failure was captured (see Figure 4). A sensitivity study also highlighted the importance of taking in situ bridge-specific information into account, for instance, associated with geometries, boundary conditions and material properties.

In addition to simulating the specific failure test, ATENA Studio has been used for structural assessment of the bridge. Nonlinear FE analyses were carried out based on the most adverse load case (i.e. groups of classification vehicles), determined according to standard assessment methods.

Fig.3: Load-deflection curves of the girder according to failure test and nonlinear FE analysis with indication of load-carrying capacity calculated by standard assessment methods.

Fig.4: Major principal concrete strains and indication of cracks (≥4 mm) at the peak load predicted by nonlinear FE analysis.

In order to verify the level of structural safety, FE analyses were combined with a probabilistic evaluation in SARA Studio. Thus, it was possible to account for some of the uncertainties in a rational way, and in relation to the initial assessment using standard methods, a 6.5-fold increase of the permissible axle load was indicated. This outcome can be compared with 5.6 times higher capacity for safety verification using the partial safety factor method, and 6.0 to 6.3 for different variants of the global resistance safety factor method.

[1] Bagge, N. (2017). “Structural assessment procedures for existing concrete bridges: Experiences from failure tests of the Kiruna Bridge.” PhD Thesis, Luleå University of Technology, Luleå, Sweden.

Dear users of ATENA software,

we would like to invite you to our ATENA Advanced User Seminar 2018. The seminar will take place in Prague, the Czech Republic on February 14-16 in Czech language and June 13-15, 2018 in English language.

In 2016 the content of the seminar was rearranged compared to the previous years. We decided to concentrate on fewer topics, but provide deeper coverage and more hands-on experience with particular problems. Based on the feedback from our hotline support we selected several topics, where we expect that ATENA users could benefit most from more indepth explanation or background information:

• Overview of new ATENA version 5.6.
• Modeling contact problems in ATENA.
• Modeling strengthening of reinforced concrete structures.
• Modeling of construction process in ATENA for bridges and tunnels.
• Modeling of fiber-reinforced concrete structures.

October 15-19, 2017
ACI Fall 2017
Anaheim, CA, USA
Event website

November 22-23, 2017
Concrete Days 2017
Litomyšl, Czech Republic
Event website

December 11-12, 2017
PROTECT2017 - 6th International workshop Performance, Protection & Strengthening of Structures under Extreme Loading
Guangzhou, China, South China University of Technology
Event website

CERVENKA, J., CERVENKA, V., KADLEC, L., SAJDLOVA, T., Uncertainty in Prediction of Shear Wall Strength by Finite Element Analysis, ACI Fall Convention, Session on Finite Element Modeling of Concrete Walls Subjected to Extreme Loads, D-Disneyland North Ballroom A, Anaheim, CA, USA, October 2017.

CERVENKA, J., HAJKOVA, K., JENDELE, L., SAJDLOVA, T., SMILAUER, V., 2017, Durability Assessment of Reinforced Concrete Structures Assisted by Numerical Simulation, 71st RILEM Annual Week & ICACMS 2017, Chennai, India, September 2017.

CERVENKA, J., JANDA, Z., JENDELE, L., PUKL, R., CERVENKA, V., 2017, Simulation of Severe Accident Scenarios in Nuclear Containments, 6th International Workshop on Performance, Protection & Strengthening of Structures under Extreme Loading, PROTECT2017, Guangzhou (Canton), China, December 2017.

CERVENKA, J., SAJDLOVA, T., CORDES, T., BERGMEISTER, K., 2017. Stability Analyses of the Partial Face Advance at the Cavern from the Access Tunnel Wolf, BBT. In: EURO:TUN 2017, Innsbruck University, Austria, 7 pages.

CERVENKA, V., MARKOVA, J., MLCOCH, J., PEREZ-CALDENTEY, A., SAJDLOVA, T., SYKORA, M., Uncertainties of Crack Width Models. Proc. of the fib Symposium, Maastricht, June 12-14, 2017, Springer International Publishing, D.A. Hordijk and M. Luković (eds.), High Tech Concrete: Where Technology and Engineering Meet, DOI 10.1007/978-3-319-59471-2_3, pp 1653-1616.

CERVENKA, V., MARKOVA, J., MLCOCH, J, PEREZ-CALDENTEY, A., SAJDLOVA, T., SYKORA, M., Uncertainties of Crack Width Models for Macro and Meso Levels of RC Structural Elements. Nordic mini-seminar: Crack width calculation methods for large concrete structure. 29-30 August 2017, Multiconsult ASA, Oslo, Norway.

PUKL R., CERVENKA V., SAJDLOVA T., CERVENKA J., NOVAK D., Probabilistic study about uncertainties in predicting shear beam cracking and failure. CCC 2017, Tokaj, Hungary, August 31 - September 1, 2017, pp 525-532.

PUKL R., NOVAK D., SAJDLOVA T., LEHKY, D., CERVENKA J., CERVENKA V., Probabilistic Design of Fibre Concrete Structures, Fibre Concrete 2017, Prague, Czech Republic, September 13-16, 2017. 

PUKL R., SAJDLOVA T., STRAUSS, A., LEHKY, D., NOVAK D., Sustainability of Transport Structures - Some Aspects of the Nonlinear Reliability Assessment, BESTInfra 2017, Prague, Czech Republic, September 21-22, 2017.

SAJDLOVA, T., PUKL, R.,  JUHASZ, K.P., NAGY L., Fibre reinforced concrete constitutive laws for numerical simulation. CCC 2017, Tokaj, Hungary, August 31 - September 1, 2017, pp 632-639.

SMILAUER, V., HAJKOVA, K., JENDELE, L., CERVENKA, J.: Durability Assessment of Reinforced Concrete Structures due to Chloride Ingress up and Beyond Induction Period, in: 39th IABSE Symposium - Engineering the Future, Vancouver, Canada, September 21-23, 2017, pp 2488-2495.