Documents published in Scipedia

• Numerical simulations of origami-based folded carbon-reinforced concrete shells

  H. Spartali, L. Mester, G. Kikis, S. Klarmann

  WCCM2024.

  
  

  Abstract

  The advantages of carbon-reinforced concrete (CRC) over traditional concrete elements reinforced with steel, including high strength, low weight, and corrosion resistance, make it a promising material for thin, efficient, and more sustainable designs. As the demand for less CO2-intensive materials such as concrete grows, a shift from simple massive elements to thin-walled elements with complex geometries is becoming increasingly necessary. However, to seek optimal design variants, efficient nonlinear numerical calculations that provide reasonable predictions of the structural behavior, including the stress-redistribution process and the failure mechanisms are essential. This paper presents FEM simulations of origami-based folded CRC shells that were experimentally investigated in a previous study. Two FEM modeling approaches were used, employing a smeared and a discrete representation of the carbon reinforcement. For both approaches a damage plasticity model for the concrete has been used. The load-deflection response from the discrete approach closely matches the experimentally obtained curves. Despite an overestimation of the load capacity, the computationally less expensive smeared FEM model qualitatively reproduces the structural response and the correct failure mechanism. Therefore, the quality of the results obtained from the smeared model is sufficient to determine preferable design variants in a typical design scenario. This is necessary to provide a deeper understanding of the structural behavior of these folded elements and to facilitate the sustainable design and application of thin-walled CRC elements in the future.

  Abstract
  The advantages of carbon-reinforced concrete (CRC) over traditional concrete elements reinforced with steel, including high strength, low weight, and corrosion resistance, [...]

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• Development of a design methodology for slender carbon-reinforced concrete columns in axial compression based on EC3

  Y. Ciupack, J. Giese, M. Curbach, B. Beckmann

  WCCM2024.

  
  

  Abstract

  Advancements in concrete construction, such as carbon-reinforced and ultra-high performance concretes, enable the creation of slender, high-capacity structures, enhancing resource efficiency and reducing CO2 emissions. Despite the clear advantages of such innovative material composites, challenging load-bearing and deformation behavior emerges in slender carbon-reinforced concrete components, indicating potential stability issues. To address this concern, current research is dedicated to experimental and analytical investigations of the structural behavior and failure of slender components in compression made of carbon reinforced concrete, aiming to enhance our understanding of stability-related aspects.

  Abstract
  Advancements in concrete construction, such as carbon-reinforced and ultra-high performance concretes, enable the creation of slender, high-capacity structures, enhancing [...]

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• Possibilities for numerical model validation through computed tomography generated data

  M. Pahn, C. de Sousa, S. Grzesiak, J. Giese

  WCCM2024.

  
  

  Abstract

  In order to make accurate predictions of the structural behaviour of non-metallic reinforced concrete elements, one of the key problems in the development of this type of new material system is the capacity of modelling the load transfer mechanisms between the concrete matrix and the reinforcement elements. To predict the load-deflection response up to ultimate limit state conditions, a wide range of numerical simulation approaches, with capability of modelling the bond behaviour between the different materials has been proposed over the years and compared to experimental results. This research work presents new possibilities for comparing numerical finite elements models with laboratory data generated by computed tomography, namely in the context of three-point bending tests performed on carbon-reinforced concrete specimens. The aim is to present the potential of in situ computed tomography for validation of numerical simulations. Examples of computed tomography generated quantitative results and data visualisation are shown, which focus on generated displacement fields and crack patterns.

  Abstract
  In order to make accurate predictions of the structural behaviour of non-metallic reinforced concrete elements, one of the key problems in the development of this type of [...]

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• Examples of analysis methods for ultrasonic vibration-assisted machining

  S. Aoki

  WCCM2024.

  
  

  Abstract

  Ultrasonic vibration has been applied to many machining processes. It has been reported that the application of ultrasonic vibration to machining has improved machining efficiency and accuracy. In this report, ultrasonic vibration is applied to welding, drilling, and knurling, and its effects are shown through experiments and analyses. In welding, it is shown that ultrasonic vibration can reduce tensile residual stress. In addition, the simulation method using a simple model showed that residual stress is reduced by the plastic deformation caused by ultrasonic vibration. In the drilling process, it was found that the surface roughness of the machined surface was improved when ultrasonic vibration was used. The conditions under which the surface roughness is improved by the impulse due to cutting resistance were also determined. In knurling, it was found that the pressing and friction forces were reduced by the use of ultrasonic vibration. It was also shown that the reduction in pressing force is expressed as the product of the equivalent mass and the amplitude of ultrasonic vibration

  Abstract
  Ultrasonic vibration has been applied to many machining processes. It has been reported that the application of ultrasonic vibration to machining has improved machining efficiency [...]

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• Coupled twin conical funnels or conical hoses: an internal process of dynamic flow distribution

  R. Ferreyra

  WCCM2024.

  
  

  Abstract

  The first objective of this study is to revisit an analytical test by the author that helps now for a prediction and explanation for the likely physical existence of twin funnels in the fluid crossed by shock wave, under certain conditions. These funnels function like a conical hose within shock waves traveling through matter. In terms of the laws of continuity, momentum, and energy the classical shock wave model is empowered with a not widespread actual function that explains a nonlocal physical phenomenon of matter distribution. The second objective is the recognition and application of two almost new analytical boundary conditions V1S = −V1 and 1 1 M S = iM , provided in the recent past that open the theory to the, at least, analytical existence of hoses or coupled twin funnels. Finally, given that supersonic and hypersonic solid cones are related to theoretical, experimental, natural, aeronautical, astronautical, geophysical and industrial interests, among others, certain analytical regions derived from this recently characterized formulation are shown and hoses or twin funnels located among them. These regions can be visualized on the plot of cone angle, shock angle, and free-stream Mach number for analogy, comparison, and prediction.

  Abstract
  The first objective of this study is to revisit an analytical test by the author that helps now for a prediction and explanation for the likely physical existence of twin [...]

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• Determination of high-order frequency response of nonlinear systems using the arc-length method

  L. Pini Tanabe, A. Serpa

  WCCM2024.

  
  

  Abstract

  While linear systems have been extensively studied in the past few decades, systems with strong nonlinearities are not as widely investigated. One of the reasons why these are less applied in engineering is due to the fact that solving nonlinear equations usually demands a steep increase in processing capacity and time when compared to their linear counterparts. As computers become more powerful, significantly more advanced nonlinear systems can be studied and analyzed, providing solutions that are more accurate for real-world applications. When it comes to frequency analysis, it is possible that nonlinear frequency response shows the phenomena of hardening or softening. In this case, the resonance peaks of the frequency response are tilted to the right or left, respectively, in comparison with linear frequency response. The consequences of these phenomena might prove essential to safety assessment of real-life structures as the resonance peak might greatly differ from those obtained in a linear analysis. In this study, the high-order frequency response of the Helmholtz-Duffing oscillator is analyzed in order to evaluate its influence on the system. The oscillator exhibits Duffing nonlinearities represented by cubic springs and Helmholtz nonlinearities represented by quadratic springs. The high-order harmonic balance method was used to determine the dynamic equation in the frequency domain. The nonlinearities were numerically integrated based on the coefficients of the Fourier series. Originally used to find the solution path of nonlinear static structural analyses, the arc-length method was adapted to determine the nonlinear frequency response

  Abstract
  While linear systems have been extensively studied in the past few decades, systems with strong nonlinearities are not as widely investigated. One of the reasons why these [...]

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• Hybrid structure health monitoring technique for enhancing modal parameter identification accuracy

  E. Mudahemuka, K. Yamamoto

  WCCM2024.

  
  

  Abstract

  SHM relies on the possibility of estimating structural modal parameters, such as mode shapes, natural frequencies, and damping, from the structure’s measured data. Nevertheless, modal parameter estimation still faces accuracy problems. The identification of bridge and/or vehicle system parameters and vibration characteristics have been studied both numerically and experimentally. The knowledge of bridge vibration characteristics and vehicle system parameters is crucial to the maintenance of bridges. The issue is that the techniques used to identify bridge and vehicle system parameters usually work very well with numerical simulation but present accuracy issues with experimental data due to environmental noise. Traditionally, measured data were obtained by instrumenting bridges with connected sensor systems, which had issues such as high cost, maintenance problems, safety concerns, and traffic disruption. More recently, indirect SHM (iSHM) methods, such as drive-by using passing instrumented vehicles, have been researched[1,2]. However, these methods still struggle with the accuracy of modal parameter identification, particularly for higher vibration modes sensitive to localized bridge damage, limiting the widespread adoption of iSHM methodologies[1,3]. A combination of indirect and direct monitoring methods is proposed to address these limitations. This approach aims to improve modal parameter identification, including higher vibration modes, for localized damage detection and structural assessment. The proposed method uses GPS-time synchronized sensors for simultaneous measurement of vehicle and bridge vibration data and is verified through numerical simulation assuming multiple runs over the same bridge. The study highlights the potential of this hybrid SHM technique to significantly improve the accuracy of indirect structural health monitoring, providing more reliable and precise modal parameter estimates, especially for higher vibration modes, allowing for the identification of localized bridge damage.

  Abstract
  SHM relies on the possibility of estimating structural modal parameters, such as mode shapes, natural frequencies, and damping, from the structure’s measured data. Nevertheless, [...]

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• An explicit time-marching procedure for elastodynamic analyses based on adaptive time-integration parameters and time-step values

  L. Ruffo Pinto, D. Soares Jr., I. de Souza Sales, W. João Mansur

  WCCM2024.

  
  

  Abstract

  This study discusses an explicit time-marching procedure that is designed for the time-domain resolution of elastodynamic models considering their physical properties and adopted spatial discretizations. The technique is entirely automated and proves itself to be highly effective, featuring second-order accuracy, adaptive algorithmic dissipation and extended stability limits. Additionally, the discussed methodology is truly explicit, truly selfstarting, and it incorporates automated subdomain/sub-cycling splitting procedures to enhance its overall performance. Thus, the algorithm automatically divides the domain of the problem into different subdomains, adjusting their time-step values according to the properties of the discretized model, which allows improving the efficiency and the accuracy of the analysis, while ensuring stability. Locally-defined adaptive time-integration parameters are also considered, establishing an entirely self-adjustable formulation. In this case, expressions for the timeintegration parameters are provided based on the local features of the discrete model, allowing to create a further link between the adopted temporal and spatial discretization procedures, better counterbalancing their errors. These parameters are locally formulated to nullify the bifurcation spectral radius of the method at pre-established sampling frequencies, providing maximal numerical damping at the highest sampling frequency of the elements of the adopted spatial discretization. This design optimizes the formulation to mitigate the influence of spurious high-frequency modes on the computed responses, allowing for enhanced analyses. In fact, the primary goal of introducing numerical damping is to eliminate non-physical spurious oscillations that may arise from the excitation of spatially unresolved modes. Therefore, the methodology not only tracks down the frequency range of the discretized model, but also it is designed to adaptively enforce significantly low values (close to zero) for the spectral radius of the method at the highest frequencies of the model, as well as it aims to provide relatively high spectral radius values (close to one, considering physically undamped models) in the important low-frequency range. Benchmark analyses are conducted at the end of this study to demonstrate the technique's effectiveness taking into account theoretical problems and complex models that are representative of real-world applications in the OIL & GAS industry.

  Abstract
  This study discusses an explicit time-marching procedure that is designed for the time-domain resolution of elastodynamic models considering their physical properties and [...]

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• An enhanced fully-adaptive explicit-implicit time-marching formulation for elastodynamics

  D. Soares, L. Pinto, I. Sales, W. Mansur

  WCCM2024.

  
  

  Abstract

  In this work, an explicit-implicit time-marching formulation, which adapts to the model's properties, its adopted spatial and temporal discretizations, and its computed responses, is studied for elastodynamic analyses. Explicit-implicit approaches have become referred to as effective time-domain solution methodologies since they allow to combine the advantageous features of both explicit and implicit formulations, such as reduced solver efforts and guaranteed stability, providing very attractive techniques.

  Abstract
  In this work, an explicit-implicit time-marching formulation, which adapts to the model's properties, its adopted spatial and temporal discretizations, and its computed responses, [...]

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• Non-destructive stress wave amplitude testing for interface bonding strength of 3D printable concrete

  C. Qi, Y. Wu, P. Zhi

  WCCM2024.

  
  

  Abstract

  The aim of this study is to investigate the impact of interface bonding properties of 3D printable concrete (3DPC) on non-destructive testing. By fabricating concrete specimens with varying numbers of layers and employing ultrasonic devices for non-destructive testing, it was observed that the presence of interface layers results in 3DPC exhibiting smaller wave amplitudes compared to conventionally cast concrete. Moreover, with an increase in printing layers, there is a trend of initial growth followed by a decline in interface bonding strength, accompanied by changes in amplitude attenuation. Through the use of non-destructive testing methods and by observing the pattern of amplitude decay, the interface bonding properties of 3DPC were investigated. The results indicate that, compared to conventionally cast concrete, 3DPC prepared using additive manufacturing techniques significantly affects the propagation of stress waves due to interface layers, and there exists a linear relationship between interface bonding strength and wave amplitude loss. This may also be a fundamental factor contributing to differences in non-destructive testing outcomes.

  Abstract
  The aim of this study is to investigate the impact of interface bonding properties of 3D printable concrete (3DPC) on non-destructive testing. By fabricating concrete specimens [...]

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