CeSTaR 3

The software was developed with a financial support from TA ČR

CeSTaR 3 - Virtual prototyping for green concrete structural design – new multi-spiral reinforced concrete column and steel beam structures(Virtuální modelování pro návrh konstrukce ze zeleného betonu - konstrukce s novými multispirálovými železobetonovými sloupy a ocelovými nosníky) 

CeSTaR 3 – 4^th call of the DELTA 2* program of TA CR
Project ID: TM04000013 
Duration: 2023 – 2025
Partners:
Červenka Consulting s.r.o. - Ing. Radomír Pukl, CSc.
CTU Prague - Prof. Ing. Zdeněk Bittnar, DrSc.
National Taiwan University of Science and Technology - Prof. Yu-Chen Ou Ph.D., Taiwan
National Center for Research on Earthquake Engineering, National Applied Research Laboratories, Ruentex Engineering & Construction Co., Ltd, Taiwan

Objectives of the project
After water, concrete is the most used material by mankind. However, 7% of global CO2 is generated due to cement production. The aim of the project is to contribute to The GCCA 2050 Cement and Concrete Industry Roadmap for Net Zero Concrete by completing 3 targets: 1. Significant improvement in the performance and reduction of steel and concrete in reinforced concrete columns through the use of multi-spiral reinforcement, 2. Prefabrication-friendly structural systems with an effective combination of concrete columns and steel beams. Transfer know-how to Czech industry. 3. A significantly higher replacement of Portland cement by Supplementary Cementitious Materials. Creating a Virtual Prototype of a new specific system for simulating various situations and supporting decision-making.

Cíle projektu
Beton je po vodě nejpoužívanějším materiálem lidstva. Nicméně 7 % celosvětového CO2 vzniká v důsledku výroby cementu. Cílem projektu je přispět k plánu GCCA 2050 Cement and Concrete Industry Roadmap for Net Zero Concrete splněním 3 cílů: 1. Výrazným zlepšením vlastností a snížením obsahu oceli a betonu v železobetonových sloupech použitím multi-spirálové výztuže, 2. Podporou konstrukčních systémů vhodných pro prefabrikaci efektivní kombinací betonových sloupů a ocelových nosníků. Přenos know-how do českého průmyslu. 3. Podporou použití betonů s větším zastoupením náhrad portlandského cementu. Vytvoření virtuálního prototypu nového specifického systému pro simulaci různých situací během výstavby a pro podporu rozhodování.

TM04000013-V1: ATENA module with improved support for the simulation of the new-MRCS joints
Result V1 delivers a specialized ATENA-based numerical module for parametric modelling, design, and simulation of MRCS beam–column joints. The module enables advanced nonlinear FEM analysis of joint regions with explicit representation of concrete confinement, reinforcement detailing (including multi-spiral reinforcement), axial load effects, and interaction between reinforced concrete columns and steel beams.
The developed ATENA module was successfully validated against experimental results and benchmark simulations, confirming its suitability for design-oriented analyses. Result V1 provides a reliable numerical basis for further methodological developments and supports performance-based design and optimization of MRCS structural systems.
Finished 3/2025

Fig. 1: View of the ATENA – MRCS joint module with parametric support and advanced cycling and dynamic modelling capabilities.

The completion of the result TM04000012-V1 is documented by the following documents:
Video demonstration: CeSTaR-3-RESULT-V1-3.mp4
Sofware documentation: CeSTaR3-ATENA-MRCS-DOCUMENTATION-RESULT-V1_v3.pdf
ATENA CeSTaR-3 module is distributed as a part of new ATENA 2026beta

TM04000013-V2: ATENA module for analysis of a construction sequence considering the strength increase over time for concrete with high replacement rate of OPC by SCM
Result V2 [2] delivers an ATENA-based software module enabling advanced nonlinear modelling and design of concrete structures made of green concrete with increased content of supplementary cementitious materials (SCMs). The module extends standard ATENA capabilities by incorporating time-dependent material properties, maturity-based strength development, and staged construction and loading processes.

The main achievement of the result is the implementation and validation of a unified modelling framework that allows realistic simulation of cracking, confinement effects, stress redistribution, and structural response at different construction stages. The module supports both graphical and parametric workflows and enables systematic assessment of construction-sequence effects on structural safety and utilization.
The ATENA Green Concrete module was successfully verified using representative benchmark studies and application examples, confirming its suitability for design-oriented analyses and optimization tasks. Result V2 provides a reliable software tool supporting performance-based design and the practical adoption of low-carbon concrete technologies in engineering practice.
Finished 12/2025 

Fig. 2: ATENA Green-Concrete modelling of construction sequence with time-dependent material parameters simulation.

The completion of the result TM04000012-V2 is documented by the following documents:
Video demonstration:
CeSTaR-3-RESULT-V2.mp4
Sofware documentation:
CeSTaR3-ATENA-GREEN-CONCRETE-MODULE-DOCUMENTATION-RESULT-V2_v4.pdf
ATENA CeSTaR-3 Green Concrete module is distributed as a part of new ATENA 2026beta

TM04000013-V3: Software for the determination of the bearing strength of the new-MRCS joints
Project output TM04000013-V3, titled “MULTIBEAR,” is the culmination of research activities conducted within RA1. Initially, the experimental program was intended to be led and executed at NTU. However, due to significant changes in funding, the complete organization of this Research Activity was taken over by CTU.
The originality and novelty of the MULTIBEAR software lie in the implementation of a pioneering analytical model for the bearing strength of concrete prisms subjected to partial area loading at the free edge. This model was formulated using a comprehensive database of FEM results, which were thoroughly validated through experimental testing.
The new analytical model facilitates the construction of interaction diagrams, enabling the rapid and efficient design of transverse cross-sections and the optimization of intersecting concrete beam dimensions. It should be noted that the interaction diagram is not constructed through the conventional method of imposing curvature and axial strain over the entire cross-section. Instead, the capacity envelope is derived by evaluating the localized response to highly concentrated loading, specifically simulating the conditions under a beam's flange where bearing strength governs. Notably, this model represents the first application of its kind to be applicable not only to traditional tie reinforcement but also to (multi)spiral reinforcement. This advanced reinforcement method offers superior structural performance, enhances the utilization of material potential, and significantly reduces labor requirements.

The result finalization was postponed till 06/2026 when the link will become available.

TM04000013-V4: Device for identifying the parameters of the mechanical properties of confined concrete 
The project result TM04000013-V4 is a utility model (a form of legal protection for new technical solutions), whose technical solution relates to a mold for the production of test specimens from deformable solid materials, intended for measuring their mechanical properties.
This mold is used for tests that can replace the triaxial compression test, which is time-consuming and costly. The mold according to this technical design allows the production of test specimens with passive confinement using circular rings, which remain on the surface of the test specimen after it is removed from the mold and constrain its transverse expansion. Test loading of this test specimen only in the axial direction in a standard loading machine (press) can then fully replace the triaxial compression test.
The essence of the technical design lies in the fact that the individual ring inserts or their semicircular segments are advantageously equipped with seating locks in their mutual seating planes to facilitate their mutual alignment and simplify their assembly. The essence of the technical design also lies in the fact that the outer cylindrical body of the mold is advantageously equipped with a replaceable filling insert under its split lower ring insert, the height of which corresponds to the difference between the height of the mold and the height of the test specimen being produced, so that, on one hand, the constant ratio between the diameter and height of the test body is maintained and, on the other hand, their upper sides are in the same plane in order to maintain standard procedures in the production of test bodies. Another advantage is the ease of assembling the mold, in which individual split ring inserts with embedded circular rings are sequentially inserted into the vertically arranged outer cylindrical body of the mold together with the upper ring insert, which thus create an inner cylindrical space in the outer cylindrical body of the mold, which is then filled with the material of the test specimen being produced, e.g., concrete mix. Another advantage is the possibility of reusing individual parts. The outer cylindrical body of the mold is usually made of metal, the circular rings are made of aluminum alloys, and all ring inserts are preferably manufactured using 3D plastic printing technology. Their production is therefore not financially demanding, and they are easy to replace in case of damage or modification, e.g., dimensional. Fig. 3.4.1 and Fig. 3.4.2 show drawings of the designed mold for the production of test specimens (technical cross-section view of the mold and produced test specimen with the rings).
A request was submitted to change the deadline for submitting this result (postponement by 180 days) for administrative reasons necessary to secure the required documents and confirmations. Ultimately, everything was secured by the end of 2025 according to the original schedule.
Finished 12/2025

Fig. 3: Technical cross-section view of the mold for the production of the test specimen.

Fig. 4: Produced test specimens with the rings.

This results is registered at the Industrial Property Office under the registration number 39098

TM04000013-V5 Optimizing the production and assembly schedule of precast compressed elements reflecting delayed maturity of the concrete with a higher SCM content
Result V5 [3] delivers a practically applicable design and optimization methodology for structural systems made of green concrete with increased content of supplementary cementitious materials (SCMs), with a focus on prefabricated and staged construction systems such as New-MRCS. The methodology explicitly accounts for time-dependent development of material properties and their interaction with construction and loading sequences.
The main achievement of the result is the formulation of a structured, performance-based design framework that integrates experimental material characterization, maturity-based modelling, and nonlinear numerical simulation. The methodology enables rational selection of concrete mixtures and optimisation of construction sequences using a standard action–resistance safety format consistent with Eurocode and fib Model Code principles.
The methodology was demonstrated and verified on representative example problems, including an MRCS structural detail and a small frame system, confirming its applicability for engineering practice. Result V5 provides designers with a transparent and reliable approach for the safe and efficient use of green concrete in sustainable structural systems.
Finished 12/2025 

Fig. 6: Evaluation of stress development and material utilization at critical sections in the modelling construction sequence and material strength development.

The proposed guidelines developed during the project:
CeSTaR3-GREEN-CONCRETE-DESIGN-OPTIMIZATION-RESULT-V5_v4.pdf

TM04000013-V6 Experimental database of compression tests on plain concrete cylinders with high SCM content and passive confinement
(this is actual status and state, will be updated at 06/2026, including web addresses)
As one of the project outputs, an open-access web-based experimental database and graphical user interface were developed to provide structured access to experimental data from uniaxial compression tests of passively confined concrete and to support their storage, visualization, and distribution. The application is organized into two main sections: a data exploration interface and a data submission interface.
The exploration interface allows users to browse and filter the available records using predefined criteria such as strength class, effective confinement, SCM replacement rate, and specimen age. Based on the selected filters, the system displays detailed information on individual concrete mixtures and their associated specimens. For each mixture, the material composition is shown together with a table of available specimens and an automatically generated stress–strain diagram, which allows direct visual comparison of multiple specimens. All experimental data files can be downloaded either individually or in bulk for a selected mixture using an automated ZIP export function. In addition, the interface allows the generation of a summary PDF report containing the applied filters, mixture compositions, specimen parameters, and the corresponding stress–strain graphs.
The data submission interface enables users to upload new experimental data through structured input forms, including mixture composition, specimen parameters, and associated CSV files containing the measured stress–strain data. Before final storage, the system provides a complete preview of the entered data, including automatic graphical visualization of the uploaded stress–strain curves, which serves as a basic consistency check.
The database is implemented as a web-based client–server application with a Python/Flask backend and a relational SQL database and is intended to serve as a long-term publicly available data source for the development, calibration, and validation of constitutive models, in particular in ATENA and OOFEM, as well as for use in other software products.
The result finalization was postponed till 06/2026 when the link will become available.
TAČR approved 180-day extension to 06/2026

Fig. 7: Illustrative example of graphical data exploration interface.

Selected publications:

REHOUNEK, L., ZENISEK, M., Numerical Simulation and Model Validation of Multispiral-Reinforced Concrete Columns’ Response to Cyclic Loading, Buildings 2025, 15(21), 3855 (20 pages); https://doi.org/10.3390/buildings15213855, EID: 2-s2.0-10502156740

CERVENKA, J., Application of Eurocode 2 new safety formats for nonlinear analysis in design and assessment of concrete structures, Seminar of Nonlinear Finite Element Modelling in Construction Industry, Tagung, Berlin, Germany, November 14-15, 2024 PDF

JOJU, J., OU, Y., DEVELOPMENT OF HIGH-STRENGTH REINFORCED CONCRETE COLUMN AND STEEL BEAM (NEW-RCS) STRUCTURAL SYSTEM, ICES2024 November 8-11, 2024, Guangzhou, China PDF

ACI Fall Convention, Philadelphia, USA, November 3–6, 2024 Presentation

ACI Spring Convention in New Orleans titled: Advanced Modelling of Reinforced Concrete Structures by CERVENKA, J., March 24-27, 2024 Presentation

JOJU, J., OU, Y., BO-CHENG, L., JUI-CHEN, W., Development and seismic performance evaluation of New high strength reinforced concrete column and steel beam (New-RCS) joints, Engineering Structures 288 (2023) 116186 PDF

CERVENKA, J., CERVENKA, V., SKANDIS, U., REHOUNEK, L., UNCERTAINTY IN THE SIMULATION OF CONCRETE FRACTURE AND COMPARISON WITH BLIND COMPETITIONS, 11th International Conference on Fracture Mechanics of Concrete and Concrete Structures FraMCoS-11, Sept 10 - 14, 2023, IISc Bangalore PDF

OU, Y., NGUYEN, V., WEI-RU, W., Seismic shear behavior of new high-strength reinforced concrete column and steel beam (New RCS) joints, Engineering Structures 265 (2022) 114497 PDF

Commercial version is under development. Public beta version can be requested by requesting developers. Use the request form below.