Finite Element Model Calibration Research Articles

Member capacity of cold-rolled aluminium alloy channel columns - part I: Experimental investigation

Cold-rolled aluminium alloy sections have been recently introduced in Australia as newly developed thin-walled products. To fabricate these sections, the roll-forming process used in cold-formed steel production has been employed, which has proven to be more cost-effective than the conventional extrusion process. This paper describes a series of compression tests to investigate member buckling behaviour and ultimate strengths of cold-rolled aluminium alloy 5052-36 channel columns. Twenty-eight specimens of three commercially available sections (C10030, C25025 and C40030) were tested at the University of Sydney. Two configurations of end boundary conditions were specially designed to capture flexural, flexural-torsional and local-global interaction buckling failure modes. Prior to testing, initial geometric imperfections were measured using a laser scanning method, and flat/corner coupons were tested to determine compressive and tensile strengths of the aluminium alloy material. The experimental results are compared with ultimate column strength predictions by current Australian/New Zealand, North American and European design specifications for aluminium structures. Additionally, the test results provide data for calibration of finite element models of cold-rolled aluminium structural members for use in parametric and similar studies. A companion paper describes such parametric study and the derivation of new design guidelines for member buckling of cold-rolled aluminium channel columns based on the numerical parametric data and the experimental data presented herein.

Analyzing the Mechanical Response of a Calibrated Finite Element Model for Flexible Pavement with Embedded Dynamic Wireless Power Transfer Technology

Analyzing the Mechanical Response of a Calibrated Finite Element Model for Flexible Pavement with Embedded Dynamic Wireless Power Transfer Technology

Stability bearing capacity of equal-leg angle steel columns with end connection joints

This study investigated the stability bearing capacity of Q355 equal-leg angle steel columns with end connection joints for transmission towers and proposed a new design method for stable bearing capacity. A total of 39 structural tests were conducted considering the connection joints. The test results, including the failure modes and load-response histories, were reported. The numerical simulations were conducted and validated using multiple comparisons. An extensive parametric study based on a calibrated finite-element model was conducted to investigate several influential parameters. The critical elastic buckling load of a three-span continuous beam with rigid or elastic supports was derived, and the relationship between the effective length coefficients and the support stiffness was obtained. Based on the experimental and numerical simulation results, a stable bearing capacity design method applicable to equal-leg angle steel columns with end connection joints was proposed. It is shown that the proposed design method improves the consistency and reliability of the prediction of the ultimate strength.

Southbank Place development: tunnel movement predictions and monitoring performance

The Southbank Place project comprised the redevelopment of the UK headquarters of the Shell Company (formerly known as the Shell Centre) in the Waterloo area of London. The project included the demolition of all structures within the site except for the iconic tower building, local extension of the existing basement and the construction of eight new mixed-use buildings. London Underground's (LU) Bakerloo Line and Northern Line running tunnels pass beneath the site. The excavation of the basement and construction of the Shell Centre in the late 1950s caused movements of the underlying Bakerloo Line tunnels that were much larger than expected. The monitoring of these tunnels between 1958 and 1995 has provided a classic case history for the behaviour of London Clay. The proposed redevelopment offered an opportunity to analyse and monitor the behaviour of LU tunnels over a period of 60 years and two phases of significant construction. This paper presents a back-analysis of the historical monitoring of the Bakerloo Line tunnels and the calibration of a sophisticated finite-element model. The model was subsequently used to predict the impact of the redevelopment on the tunnels as part of the assurance procedure with LU.

Calibration of finite element model of bridge with pier retrofitted using Fe-SMA strips

Calibration of finite element model of bridge with pier retrofitted using Fe-SMA strips

Sensitivity and reliability assessment of buckling restrained braces using machine learning assisted-simulation

Buckling Restrained Braces (BRBs) play an essential role in seismic protection due to their remarkable energy dissipation capacity, ductility, and stiffness. This paper represents the first thorough evaluation of the reliability and uncertainty of BRBs, accounting for various sources of uncertainty and varied conditions, such as different gap sizes, friction coefficients between the encasing and the steel core, and other geometric and mechanical properties of the connecting parts. This paper introduces an innovative application of an integrated probabilistic approach that combined Finite Element (FE) modeling, Artificial Neural Networks (ANN), and Monte Carlo simulation to characterize the seismic behavior of BRBs. Experimental results from literature is used to validate the FE model constructed using ABAQUS. This validated model is then integrated into a Low-rank Tensor Approximation process to yield variance-based sensitivity measures for the considered variables. The most influential variables identified in this process along with the calibrated FE model is utilized to conduct a reliability assessment through an ANN-assisted Monte Carlo simulation. This analysis is conducted to quantify the reliability level of the investigated BRBs as a function of the gap size and establish the resistance factors necessary to maintain the reliability level above prescribed thresholds. It was found that the highest reliability can be achieved at a small gap size equal to half the radius of gyration of the main steel core, requiring a resistance factor of 0.9. For gap sizes higher than this value, a resistance factor ranging between 0.70 and 0.85 is needed.

Research on the Construction of a Finite Element Model and Parameter Calibration for Industrial Hemp Stalks

Finite element numerical simulations provide a visual and quantitative approach to studying the interaction between rigid mechanical components and flexible agricultural crops. This method is an important tool for the design of modern agricultural production equipment. Obtaining accurate material model parameters for crops is a prerequisite for ensuring the reliability and accuracy of numerical simulations. To address the issue of unclear mechanical constitutive model parameters for industrial hemp stalks, this study utilized the theory of composite materials to establish a mechanical constitutive relationship model for industrial hemp stalks. Compression, tensile, and bending tests on different components of the stalk were conducted, using a computer-controlled universal testing machine, to obtain their elastic parameters. Combined with the measured basic material parameters and contact parameters of industrial hemp stalks, a finite-element numerical simulation model of industrial hemp stalks was established. By conducting Plackett–Burman and central composite experiments, it was determined that among the six measured parameters, the anisotropic plane Poisson’s ratio of the phloem and the isotropic plane Poisson’s ratio of the xylem have a significant influence on the maximum bending force of the stalk. Parameter optimization was carried out, using the relative error of the maximum bending force as the optimization objective, resulting in an anisotropic plane Poisson’s ratio of 0.054 for the phloem and an isotropic plane Poisson’s ratio of 0.28 for the xylem of industrial hemp stalks. To validate the accuracy and reliability of the optimized parameters, a numerical simulation was conducted and compared with the physical experiments. The simulated value obtained was 405.81 N while the actual measured value was 392.55 N. The error between the simulated and measured values was only 3.4%, confirming the effectiveness of the model. The precise parameters for the mechanical characteristics of industrial hemp stalk material obtained in this study can provide a parameter basis for future research on the numerical simulation of mechanized industrial hemp harvesting and retting.

Parameter optimization in a finite element mandibular fracture fixation model using the design of experiments approach

Only a few mandibular bone finite element (FE) models have been validated in literature, making it difficult to assess the credibility of the models. In a comparative study between FE models and biomechanical experiments using a synthetic polyamide 12 (PA12) mandible model, we investigate how material properties and boundary conditions affect the FE model's accuracy using the design of experiments approach.Multiple FE parameters, such as contact definitions and the materials' elastic and plastic deformation characteristics, were systematically analyzed for an intact mandibular model and transferred to the fracture fixation model. In a second step, the contact definitions for the titanium screw and implant (S–I), implant and PA12 mandible (I-M), and interfragmentary (IF) PA12 segments were optimized. Comparing simulated deformations (from 0 to −5 mm) and reaction forces (from 10 to 1′415 N) with experimental results showed a strong sensitivity to FE mechanical properties and contact definitions. The results suggest that using the bonded definition for the screw-implant contact of the fracture plate is ineffective. The contact friction parameter set with the highest agreement was identified: titanium screw and implant μ = 0.2, implant and PA12 mandible μ = 0.2, interfragmentary PA12 mandible μ = 0.1. The simulated reaction force (RMSE = 26.60 N) and surface displacement data (RMSE = 0.19 mm) of the FE analysis showed a strong agreement with the experimental biomechanical data. The results were generated through parameter optimization which means that our findings need to be validated in the event of a new dataset with deviating anatomy.Conclusively, the predictive capability of the FE model can be improved by FE model calibration through experimental testing. Validated preoperative quasi-static FE analysis could allow engineers and surgeons to accurately estimate how the implant's choice and placement suit the patient's biomechanical needs.

Block shear and tear-out in bolted connections as limited by curling

In the literature, the block shear and tear-out phenomena and strengths of cold-formed steel bolted connections have been well understood and thoroughly investigated. However, the strength of these failure modes in the bolted connections between thin and thick plates may be governed by the effect of out of plane curling of the thin plate, and this phenomenon has not been studied in detail yet. It is apparent that the curling not only affects the shear strength but also changes the behaviour of the bolted connections. In particular, the design shear strength of the bolted connections remains unchanged with high ductility even though the end distance between the bolt holes and the free edge is becoming larger. An experimental program on the block shear and tear-out behaviour of bolted connections was performed at the University of Sydney in order to provide a better understanding on the effect of the curling. A total of 48 tests including thicknesses of thin plates (1.0 mm, 1.2 mm and 1.9 mm) and 10 mm thick plates was conducted at the University of Sydney with three configurations of bolted connections in conjunction with two different hole diameters (9 mm and 14 mm) and various end distances as the main variables. Three different failure modes being block shear, tear-out and curling were observed in the tests. In addition, different material properties of the cold-formed sheet steels (i.e., G300, G450, G500 and G550) were also considered in this program to create a large database for the investigation. Consequently, a design equation for block shear and tear-out strength accounting for the curling effect is proposed in this paper. It provides a better correlation with the experimental results than those predicted in the current Australian and New Zealand Standard (AS/NZS 4600) and the North American Specification for cold-formed steel structures (AISI S100). In addition, a calibrated Finite Element Model (FEM) was subsequently developed using the commercial finite element program ABAQUS to verify against the test results. The reliable data set of the FEM models is further utilised to extend the data range in a parametric study and is finally used for the verification procedure of the proposed formula over a wider range of data.

Model-informed deep learning strategy with vision measurement for damage identification of truss structures

Structural damage identification approaches can be divided into two categories, i.e. data-driven approaches via statistical pattern recognition and model-based approaches via finite element (FE) model updating. These two approaches have their own merits, and their main shortcomings can be remedied by each other’s merits. Therefore, this study proposed a deep learning-based damage identification strategy involving both data-driven and model-based approaches, termed as model-informed deep learning (MIDL)-based strategy. This strategy first proposes a vision-based displacement estimation approach to extract structural displacement responses from video data. This approach reduces the displacement drift induced by conventional optical flow approaches and improves the tracking accuracy of feature points. Then, a calibrated FE model is built to construct data sets with different damage levels via FE model updating and time-history analysis. Following this, a one-dimensional convolutional neural network (1D CNN) is established to detect and localize structural damage by using direct displacement responses. Finally, FE model updating is performed again to quantify structural damage level with constrained targets. A truss structure is further used to evaluate the accuracy of the proposed strategy experimentally. Results illustrate that the proposed MIDL strategy, which uses time series to localize the structural damage, achieves a global location accuracy of 86.09% and avoids the feature extraction process. Meanwhile, with the known damage location, the efficiency and accuracy of structural damage quantification via rerunning model updating can also be significantly improved. In addition, the displacements estimated by the proposed approach have a good match with ground truth values with error standard deviations of less than 0.3 mm.

Modelling Strategies for the Updating of Infilled RC Building FEMs Considering the Construction Phases

This paper deals with modelling strategies for the updating of Finite Element Models (FEMs) of infilled Reinforced Concrete (RC) frame buildings. As is known, this building typology is the most adopted worldwide for residential houses and strategic buildings, such as hospitals, schools, police stations, etc. The importance of achieving trustworthy numerical models for these kinds of structures, especially the latter ones, is clear. The updating procedure mainly consists in changing the geometrical and mechanical material properties of models until pre-determined convergence criteria are verified, the latter based on the comparison between numerical and experimental outcomes. In this work, the modelling strategies that can be adopted to refine FEMs of infilled RC buildings are treated in-depth, starting from the simple model usually developed for design purposes. Modelling techniques relevant to the geometry, the mechanical properties, the mass, and the restraint conditions of the model are discussed. Moreover, the approaches that can be adopted to calibrate numerical models during the construction process are addressed as well. Then, an application of the proposed strategies is provided with reference to a real building that was investigated during its construction. The proposed modelling strategies proved to be effective in the model updating of the considered building and provide useful support for the calibration of FEMs of this building typology in general.

8-MW wind turbine tower computational shell buckling benchmark. Part 2: Detailed reference solution

An assessment of the elastic–plastic buckling limit state for multi-strake wind turbine support towers poses a particular challenge for the modern finite element analyst, who must competently navigate numerous modelling choices related to the tug-of-war between meshing and computational cost, the use of solvers that are robust to highly nonlinear behaviour, the potential for multiple near-simultaneously critical failure locations, the complex issue of imperfection sensitivity and finally the interpretation of the data into a safe and economic design.This paper presents a detailed reference solution to the computational buckling analysis of a standardised benchmark problem of an 8-MW multi-strake wind turbine support tower. Both linear and nonlinear analyses are performed, including advanced GMNIA with several different models of geometric imperfections. The crucial issue of interpreting the imperfection amplitude in a way that is compliant with the new prEN 1993-1-6 is discussed in detail. The solution presented herein is intended for use by analysts in both industry and academia for training, verification and calibration of finite element models and is intended to initiate a public repository of such computational solutions for metal civil engineering shell structures.This paper is the second of a pair. The first paper [37] presents a synthesis of 29 submissions to an international round-robin exercise performed on the same benchmark problem.

Evaluation of Spliced UHM CFRP Strip Panels for Strengthening Steel Beams

Short ultrahigh-modulus (UHM) carbon fiber–reinforced polymer (CFRP) strip panels connected through a finger joint configuration offer a convenient modular method for strengthening steel girders. Three-dimensional nonlinear finite-element (FE) analysis was conducted to characterize the interfacial and flexural behavior of strip panels. The calibrated FE model provides an efficient and economical method of evaluating different parameters related to the material properties and strengthening configuration of the UHM CFRP strip panels, for which experimental data are not available. Analysis implemented robust features, including debonding of CFRP using a mixed-mode bond–slip model, CFRP rupture, steel yielding, and concrete slab crushing. Predictions were calibrated and validated against experimental results from double lap shear tests and flexural tests of steel beams and steel–concrete composite beams. The FE model was used to investigate the effects of finger joint location, joint length, and laminate thickness. Strip panels with 300-mm-long finger joints and thicknesses of up to 2 mm equaled the strength of a continuous laminate with the same CFRP area. Both failed by CFRP rupture. At greater thicknesses, debonding occurred at lower ultimate loads than for a continuous laminate. The finger joint splice was also compared to the traditional splice plate method. The splice plate length required to achieve the same level of load transfer was longer than the finger joint length when the connection was in the maximum moment region. For a given CFRP thickness and splice plate length (or finger joint length), strip panels with finger joints provide greater load-carrying capacity.

Experimental and Numerical Study on Unreinforced Brick Masonry Walls Retrofitted with Sprayed Mortar under Uniaxial Compression

The use of shotcrete or sprayed mortar is a common construction alternative to retrofit unreinforced brick masonry (URM), and extensive research has already been carried out in this area. However, most studies have been conducted on lateral strength, for example, eccentric compression or seismic forces. On the other hand, there are few studies about uniaxial compression, and the results of most studies confirm a strong relationship between the thickness of the retrofitting layer and whether it is a double-sided retrofitting section. However, most studies are exclusively experimental, with few samples, and lack numerical analysis; therefore, deeper research is required on this issue. In this sense, this paper combined experiments and finite element (FE) simulations to further study the uniaxial compression. A series of cyclic uniaxial compression experiments on URM retrofitting with sprayed mortar were performed. The experimental results were used to calibrate the FE model. Using these calibrated FE models, more variable parameters were run so that more reference results could be obtained. Moreover, the resulting damageable model of FE will be useful for studying the behavior in the inelastic phase. Results found that the compression strength of most composite walls retrofitted with sprayed mortar increases with the thickness of the sprayed layer and can improve the construction defects of the masonry itself. An over-thin sprayed layer reduces the range of the elastic phase of the composite wall. This phenomenon tends to stabilize with increasing thickness. The ultimate strength of the composite masonry is generally positively correlated with the overall increase in the thickness of the sprayed mortar but may cause a negative contribution to the ultimate strength of the composite masonry when the sprayed layer is too thin. The contribution of double-sided spraying to the ultimate strength of the composite wall was not as large as expected, but the contribution to the improvement of the elastic modulus of the wall was significant.

Experimental and numerical study on the effective length of tower cross bracing

Based on the present study, a new design formula for the effective length coefficient of the commonly used cross bracing in transmission towers is proposed. A total of 22 structural tests were conducted considering the interaction in the buckling of cross bracing. The test results, including the failure modes and load-response histories, were reported. The numerical simulations were conducted and validated using multiple comparisons. The ultimate strengths, calculated by the Chinese design code of DL/T 5154, are not sufficiently accurate. An extensive parametric study based on a calibrated finite-element model was conducted to investigate several influential parameters. Implicit theoretical equations for effective length were formulated and evaluated. The numerical results were subsequently used to obtain a new design formula for the effective length coefficient associated with the stress ratios. It is shown that the proposed formula, which was obtained from piecewise linear fitting, improves the consistency and reliability of the prediction of the ultimate strength.

Calibration of Finite Element Model of Titanium Laser Welding by Fractional Factorial Design

This paper focuses on the calibration of heat source parameters to reproduce temperatures and distortions in welded joints. Specifically, the proposed methodology, which combines the Finite Element Method and Design of Experiments, is applied to calibrate a T-joint dissimilar titanium laser welding process. The thermal problem is addressed using a 3D transient model with a Conical Gaussian heat flux, and the mechanical problem is tackled using a 3D elastic-plastic model. A Fractional-Factorial Design is performed to define a set of thermo-mechanical uncoupled models. Finally, optimal parameter combinations that replicate experimental data are identified. This methodology allows automation that replaces the traditional trial and error process, which frequently does not provide good results, is an exhausting task and requires a dubious amount of time.

A Literature Review and Result Interpretation of the System Identification of Arch Dams Using Seismic Monitoring Data

The system identification of concrete dams using seismic monitoring data can reveal the practical dynamic properties of structures during earthquakes and provide valuable information for the analysis of structural seismic response, finite element model calibration, and the assessment of postearthquake structural damage. In this investigation, seismic monitoring data of the Pacoima arch dam were used to identify the structural modal parameters. The identified modal parameters of the Pacoima arch dam, derived in different previous studies that used forced vibration tests (FVT), numerical calculation, and seismic monitoring, were compared. Meanwhile, different modal identification results using the input-output (IO) methods and the output-only (OO) identification methods as well as the linear time-varying (LTV) modal identification method were adopted to compare the modal identification results. Taking into account the different excitation, seismic input, and modal identification methods, the reasons for the differences among these identification results were analyzed, and some existing problems in the current modal identification of concrete dams are pointed out. These analysis results provide valuable guidance regarding the selection of appropriate identification methods and the evaluation of the system identification results for practical engineering applications.

An experimental-numerical method for the calibration of finite element models of the lumbar spine

We present a systematic and automated stepwise method to calibrate computational models of the spine. For that purpose, a sequential resection study on one lumbar specimen (L2-L5) was performed to obtain the individual contribution of the IVD, the facet joints and the ligaments to the kinematics of the spine. The experimental data was prepared for the calibration procedure in such manner that the FE model could reproduce the average motion of the 10 native spines from former cadaveric studies as well as replicate the proportional change in ROM after removal of a spinal structure obtained in this resection study. A Genetic Algorithm was developed to calibrate the properties of the intervertebral discs and facet joints. The calibration of each ligament was performed by a simple and novel technique that requires only one simulation to obtain its mechanical property. After calibration, the model was capable of reproducing the experimental results in all loading directions and resections.

Design of cold-rolled aluminium alloy channel beams subject to global buckling

The paper presents the development of new design guidelines for cold-rolled aluminium alloy 5052-H36 channel beams subject to global buckling. The validation data are obtained from the experimental and numerical Finite Element (FE) results as performed in previous studies by the authors. The failure modes in the experiments were observed as flexural–torsional buckling modes, and good agreement was achieved between the experimental and FE results. Based on the reliable and calibrated FE models, a parametric study is carried out in this paper to extend the data range by varying section dimensions and member lengths. Subsequently, all experimental and FE ultimate strengths of the parametric study are compared with nominal member capacities of aluminium beams as predicted by the current Australian/New Zealand, American and European aluminium design standards. Additionally, the Direct Strength Method (DSM) design rules from the Australian and New Zealand standard - AS/NZS 4600 for cold-formed steel structures are applied to predict member bending capacities for comparisons. Finally, reliability analyses are performed to evaluate the efficiency of the abovementioned design methods. It is found that the design guidelines for nominal member bending capacities to the AS/NZS 4600 standard provide accurate predictions and are therefore proposed to be used for the design of cold-rolled aluminium alloy channel beams as investigated in this paper.

Capacity prediction of straight and inclined slender concrete-filled double-skin tubular columns

PurposeConcrete-filled double-skin tubular (CFDST) columns have been gaining significant attention since these columns proved to be more efficient compared to concrete-filled steel-tubular (CFST) columns. This paper presents a tool to design slender CFDST columns with/without inclination.Design/methodology/approachFirst, 3D nonlinear finite element (FE) models of twenty-two straight CFDST columns are calibrated and it is found that FE results are in good agreement with the experimental outcomes. This is validated based on available experimental data. Subsequently, a parametric study is conducted by adjusting each calibrated FE model to account for three different angles of inclination. These models are used to quantify the effective length factor of these inclined columns.FindingsIt is found that FE results are in good agreement with the experimental outcomes. An equation is developed in this paper to calculate the characteristic concrete compressive strength for the design of straight CFDST columns. In addition, an equation is presented for engineering practice to calculate the effective length factor at different inclination angles and slenderness ratios to design CFDST columns. The predicted load capacity compares well with the experimental results of straight columns and FE results of inclined columns.Originality/valueAdvancement in the structural design procedure is required as a response to the continuous innovations in architectural design. Designers might introduce an inclination in columns in buildings or bridges, and there are no available guidelines to design them.