CeSTaR - Computer simulation and experimental validation - complex service for flexible and efficient design of pre-cast concrete columns with innovative multi-spiral reinforcement

Motivation

Cement and steel production account for about 7% and 5%, respectively, of CO2 generation. It is therefore highly desirable to optimize the design of reinforced concrete structures in sucha way that the properties of these materials are fully utilized. For this purpose, it is necessary to apply innovative ideas of structural design and advanced computational models, which must be carefully validated. Interactions between the implementation of highly costly and time consuming validation experiments and the computational model must be considered from the very beginning. This means that the computational model will be used in the design of the experiment, including optimization of the sensor layout, and then the measured data will be compared with the computationally predicted values. The detected differences will be exploited for improvements of the mathematical model.
The innovative design idea to be investigated in this project is inspired by the multi-spiral reinforcement for reinforced concrete columns initially developed by the National Taiwan University (NTU) and Ruentex Engineering & Construction Co., Ltd. One example of a successful application of this concept is the five-spiral reinforcement. Previous tests have shown that columns with the innovative five-spiral reinforcement exhibit much higher structural performance under axial compression load and lateral cyclic load than conventional columns. Moreover, the five-spiral reinforcement reduces the material cost by 43%, which can significantly reduce CO2 emissions generated by production of cement and steel. Labor cost can also be reduced by 33% due to automation in the production of innovative reinforcement systems.
In spite of the success in the development of the innovative multi-spiral reinforcement, the optimal design parameters of the reinforcement remain largely unknown. Moreover, a computational model that is able to predict the structural behavior of columns with confinement generated by multi-spiral reinforcement is yet to be developed. Such a computational model not only can help to gain insight into the mechanisms of the structural behavior but also can be used to determine the optimal design parameters of both concrete and reinforcement to achieve the most effective use of the materials.

Project objectives

  • To develop extension modules for software ATENA and academic research software OOFEM, which will provide computational support for the design of pre-cast columns with the innovative spiral reinforcement.
  • To work out a confinement model that represents the spiral reinforcement correctly and becomes applicable to a computer-based optimal design which, while maintaining the required safety, will reduce the consumption of both concrete and steel.
  • To develop software for identification of the parameters of used constitutive models. The cooperation in this part of the project is absolutely crucial. Full use of computer simulations is not possible without reliable experimental data.
  • To design and manufacture a prototype of a new simple device for an innovative compression test of concrete with the effect of confinement.

Project outputs

Conference papers

  • P. Havlásek, M. Jirásek, Z. Bittnar: Modeling of precast columns with innovative multi-spiral reinforcement. In: Concrete Innovations in Materials, Design and Structures - Proceedings of the fib Symposium 2019. fib Symposium 2019, Krakow, 2019-05-27/2019-05-29. Lausanne: Fédération Internationale du Béton, 2019. p. 2301-2307. ISSN 2617-4820. ISBN 978-2-940643-00-4.

Software

  • P. Havlásek: Malcolm version 1.0, 2019. Software, Documentation.
    Program Malcolm is a user-friendly parametric pre-processor for nonlinear analysis of precast concrete columns with multi-spiral reinforcement subjected to a combination of compression and bending. The program creates an input file for the finite element package OOFEM. The multi-spiral layout of transverse reinforcement offers significantly better carrying capacity and ducility than conventionally reinforced columns with stirrups and ties. In the case of circular columns reinforced with a single spiral, high ductility and improved strength is limited to compressive loading with a small eccentricity only. Whereas with the multi-spiral reinforcement, superb structural performance and high resilience is obtained for almost arbitrary loading, which makes this solution suitable particularly for structures built in seismic regions.
  • E. Janouchová, K. Mikeš, A. Kučerová: Software, Documentation.
    The presented manual describes the basic usage of the software for material model parameter identification delivered by the CTU team as a partial result of the project CeSTaR - Computer simulation and experimental validation - complex service for flexible and efficient design of pre-cast concrete columns with innovative multi-spiral reinforcement. There are two main MATLAB programs: IDENTIFICATION and SENSITIVITY ANALYSIS, which provides information about relations between inputs and outputs of the investigated material model for concrete and estimation of the model inputs' values together with the associated uncertainties for given experimental data.

Verified technology

  • Z. Bittnar, P. Bittnar, P. Havlásek, P. Padevět: Innovative test for evaluation of concrete material parameters by compression test with confinement, 2019.
    Concrete is a material with different tensile and compressive behavior. It is quasi-brittle in tension. In compression it has the character of a plastic material whose ductility strongly depends on the level of lateral confinement. 20 years ago, RUENTEX, a Taiwanese company, developed a multi-spiral column reinforcement technology which makes more use of confined concrete. A number of time- and cost-demanding tests have been conducted in Taiwan to verify the impact of this technology. We have received funding for a joint research that will link experiments with computer simulations. However, data on the behavior of compressed concrete is necessary to perform computer simulations. It is very difficult and demanding to describe in detail the behavior of concrete in compression, especially on experimental technique. Therefore, we have proposed a relatively simple test which produces confinement that can be achieved using multi-spiral reinforcement.

Reports

  • R. Pukl, Z. Bittnar, P. Havlásek, M. Jirásek: Theoretical description, implementation and validation of the developed software tools, 2018.
    The scope of this report is to briefly present the material models for concrete, steel and bond used in ATENA and OOFEM finite element programs, to show their verification against experimental data from the literature, and to demonstrate that a complex computational model is capable of capturing the complex behavior of a precast column with multi-spiral reinforcement. The last section deals with the transfer of the CAD geometry to FEM using BIM technology and established data formats.
  • Z. Bittnar, P. Havlásek, K. Mikeš, E. Janouchová, A. Kučerová, P. Bittnar: Identification of material parameters, design of a new compression test, 2018.
    The material models for concrete failure contain large quantity of material parameters, some of which are difficult to identify and some cannot be identified at all from standard tests. For this purpose a new uniaxial compression test with passive confinement is being developed and the best currently available identification techniques will be utilized for the identification of model parameters. The progress in the development of the new test and the identification within year 2018 is the scope of this report.