Finite Element Model Calibration Research Articles

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.

Structural health monitoring and modal parameters identification of Mezcala Bridge

Since 2016 the Instituto Mexicano del Transporte (Mexican Transport Institute) has continuously instrumented and performed the structural monitoring of the Mezcala Bridge, which is a cable-stayed bridge located in the State of Guerrero, Mexico. In order to identify early damage, several monitoring strategies based on changes in the bridge modal parameters have been implemented. To establish the limits of the parameters, such as the natural frequencies, damping ratios, and mode shapes, it is necessary to characterize the bridge dynamic behavior through monitoring information from the last 3 years, in order to analyze statistically every parameter and simulate different real damage scenarios. Modal parameters are calculated and evaluated every week or after accidents, earthquakes, or strong winds. Applying the proposed methodology based on the Enhanced Frequency Domain Decomposition (EFDD), the modal parameters of the Mezcala Bridge were efficiently estimated and monitored and subsequently, they could be used for finite element model development and calibration in order to evaluate the structural integrity of the bridge.

Fracture analysis of healthy and osteoporotic femora using clinical CT images, phantomless densitometry, and linear FE method.

Computational fracture analysis has become a growing branch of orthopedic research. Particularly, the associated methods provide reliable tools for the analysis of 3D CT-based models of bone. This paper reports the results of such analyses for 15 human femora (healthy and osteoporotic) under different loading orientations (85 different analysis cases). A new method was developed for the calculation of the density distribution in the models from ordinary clinical CT images without calibration phantom. This method, along with a strain-energy-based linear finite element (FE) analysis scheme, was used to predict the fracture strength and pattern of 10 cadaveric femora, for which the mechanical testing results and calibrated FE models were already available. The very good agreement and consistency between different sets of results showed the reliability and accuracy of the new density calibration method, as well as the linear analysis scheme. Accordingly, the method was applied to five new clinical images, gathered from two clinics that used different scanners with different protocols. The strength and fracture pattern of each one of these specimens were analyzed under 15 different loading conditions. A consistent behavior was found for variation of the fracture load and pattern of all specimens with the loading orientations, while very clear contrasts were observed between the strength amplitudes of healthy and osteoporotic specimens. The proposed methods can be easily applied to ordinary daily (even archived) clinical CT scans to conduct fast and reliable fracture analysis of human femora for general bone research and opportunistic studies of osteoporosis and trauma.

Calibration Method for Soft Robots Modeled With FEM: Application to Anisotropy

This letter aims at contributing to the sim2real challenge in soft robotics. We present a method for automatic finite element model calibration based on real data using quadratic programming optimisation. The method is generic and evaluated in this study to fit mechanical parameters from anisotropic materials. We show that we are able to optimise the mechanical properties of a given structure along its shape to achieve a given configuration goal. We show the methods interest for calibration by taking reference points from a real world robot and use them in our optimisation process as goals the simulation has to match. Our process will minimise the errors introduced by manufacturing, imperfect models or even mechanical fatigue/plasticity.

Annulus Calibration Increases the Computational Accuracy of the Lumbar Finite Element Model.

Mechanical simulations. Inadequate calibration of annuli negatively affects the computational accuracy of finite element (FE) models. Specifically, the definition of annulus average radius (AR) does not have uniformity standards. Differences between the elastic moduli in the different layers and parts of the annulus were not fully calibrated when a linear elastic material is used to define its material properties. This study aims to optimize the computational accuracy of the FE model by calibrating the annulus. We calibrated the annulus AR and elastic modulus in our anterior-constructed lumbar model by eliminating the difference between the computed range of motion and that measured by in vitro studies under a flexion-extension loading condition. Multi-indicator validation was performed by comparing the computed indicators with those measured in in vitro studies. The computation time required for the different models has also been recorded to evaluate the computational efficiency. The difference between computed and measured ROMs was less than 1% when the annulus AR and elastic modulus were calibrated. In the model validation process, all the indicators computed by the calibrated FE model were within ±1 standard deviation of the average values obtained from in vitro studies. The maximum difference between the computed and measured values was less than 10% under nearly all loading conditions. There is no apparent variation tendency for the computational time associated with different models. The FE model with calibrated annulus AR and regional elastic modulus has higher computational accuracy and can be used in subsequent mechanical studies.

Calibration and Validation of a Linear-Elastic Numerical Model for Timber Step Joints Based on the Results of Experimental Investigations.

The paper is dedicated to the numerical analysis of a single-step joint, enabling the prediction of stiffness and failure modes of both single- and double-step joints. An experimental analysis of the geometrically simplest version, the single-step joint, serves as a reference for the calibration of the subsequent finite element model. The inhomogeneous and anisotropic properties of solid timber make detailed modelling computationally intensive and strongly dependent on the respective specimen. Therefore, the authors present a strategy for simplified but still appropriate modelling for the prediction of local failure at certain load levels. The used mathematical approach is based on the linear elasticity theory and orthotropic material properties. The finite element calculations are performed in the environment of the software Abaqus FEA. The calibrated numerical model shows a good conformity until first failures occur. It allows for a satisfactory quantification of the stiffness of the connection and estimation of the force when local failure begins and is, therefore, recommended for future, non-destructive research of timber connections of various shapes.

Location Sensitivity of Non-structural Component for Channel-type Auxiliary Building Considering Primary-secondary Structure Interaction

To ensure the safe and stable operation of nuclear power plants (NPP), many non-structural components (NSCs) are actively associated with NPP. Generally, floor response spectrum (FRS) is used to design the NSCs. Nevertheless, it is essential to focus on the mounting position and frequency of NSCs which is normally ignored during the conventional design of NSCs. This paper evaluates the effect of mounting location for NSCs over the same floor in a channel-type auxiliary building. The modal parameter estimation is taken into account to capture the dynamic property of the NPP auxiliary building by the shake table test; which leads to the calibration of the finite element model (FEM). The calibration of FEM was conducted through response surface methodology (RSM) and the calibrated model is verified utilizing modal parameters as well as frequency response spectrum function. Finally, the location sensitivity was investigated by time history analysis (THA) under artificially generated design response spectrum compatible earthquakes and sine sweeps. The result showed that the right choice of location for NSCs can be an important measure to reduce the undesirable responses during earthquakes, which can reduce up to 30% horizontal and 70% vertical zero period acceleration (ZPA) responses in channel-type auxiliary buildings.

Reliability assessment of connections with slip-critical bolts and fillet welds in combination

This paper quantifies the reliability level of connections combining slip-critical bolts and longitudinal fillet welds using a probabilistic approach that integrates finite element (FE) modeling, meta-modeling, and Monte Carlo simulation. The proposed approach relies on experimental results to calibrate a FE model and quantify the uncertainties associated with various input parameters. The calibrated FE model is next integrated into a low-rank tensor approximation process to provide the variance-based sensitivity measures associated with the considered random variables. The influential variables, along with the calibrated FE model, are then used to evaluate the reliability by means of accelerated Kriging Monte Carlo simulation (AK-MCS). Finally, the proposed approach is applied to combination bolted-welded connections under direct tension to evaluate their reliability considering different faying surface conditions. The results of the conducted sensitivity analysis indicate that variability in weld geometry, bolt pretensioning forces, and friction coefficient of steel surface would significantly contribute to the variability of the load-carrying capacity of the investigated connections. In addition, the reliability of the combination connections with Class A and B faying surfaces is evaluated based on code provisions.

Calibration of the numerical model of a track section over a railway bridge based on dynamic tests

Progressive updating strategies are commonly used for the calibration of numerical models such as those of a track-bridge system. These strategies involve, first, updating the track model based on dedicated dynamic tests, and second, the calibration of the bridge model based on ambient vibration tests considering the updated track parameters. This subsequent procedure is suggested as some track parameters are, in relation to the modal responses of the bridge, generally not sufficiently sensitive for a successful parameter estimation. This work describes the calibration of a specific finite element (FE) model of a track section over a bowstring-arch railway bridge. The model includes the rails, rail pads, sleepers, the ballast layer and the interfaces with the bridge and neighbouring track sections. A track receptance test allowed for the identification of natural frequencies and mode shapes of the track by applying two different techniques, an output-only and an input-output. Several modes of vibration related to the movement of the sleepers on the ballast were identified using the SSI-DATA method, at frequencies between 83.8 Hz and 142.2 Hz. The calibration of the track FE model was performed using an iterative methodology by means of a genetic algorithm, which proves efficiency and robustness in estimating several track numerical parameters, besides a significant upgrade in relation to the numerical model before calibration.

Substructure Modeling and Loading-Control Techniques for the Test of a Full-Scale Spatial RC Frame with Buckling-Restrained Braces Subjected to Bidirectional Loading

To investigate the performance of reinforced-concrete frames with buckling restrained braces (RCF-BRB) subjected to bidirectional earthquakes, a full-scale two-story RCF-BRB was tested using substructured pseudodynamic (PsD), quasistatic, and pushover techniques. This paper focuses on the structural modeling for the substructured PsD tests, and the control and measurement issues of the bidirectional loading system. To make a credible reproduction of the structural response using substructured PsD technique, an overlap modeling technique together with tuning the mass of the lamped-mass model and stiffness of the numerical substructure was employed to reduce errors caused by the incomplete boundary condition. The outer-loop control method based on Newton’s iteration method was introduced for the loading system, with the data from external displacement sensors as the feedback to avoid errors caused by possible gaps in the connection parts of the loading system. The redundancy issue, caused by the actuators outnumbering the degrees of freedom of the floor to be controlled, is addressed with a force-displacement mixed control technique. The three of four actuators were controlled in displacement mode, whereas the redundant one was in force mode. The force command to the redundant actuator was determined with the optimization criteria to minimize the loads relative to the capacities of the actuators. The working range of the displacement sensors is investigated using numerical and geometric approaches. Failure examples from numerical simulation and experiment were shown to emphasize the importance of proper arrangement of displacement sensors. A rearrangement of the displacement sensors was proposed for the pushover test to enlarge the working range. Time-history results of the prototype structure using the calibrated finite-element model show that the PsD substructure test results could represent seismic responses of the prototype structure. The measured mass-center displacements accurately tracked the target displacements throughout the test, indicating the effectiveness of the loading control and measuring system.

Numerical Investigation of Deposition Characteristics of PLA on an ABS Plate Using a Material Extrusion Process.

Three-dimensional prototypes and final products are commonly fabricated using the material extrusion (ME) process in additive manufacturing applications. However, these prototypes and products are limited to a single material using the ME process due to technical challenges. Deposition of plastic on another dissimilar plastic substrate requires proper control of printing temperature during an ME process due to differences in melting temperatures of dissimilar plastics. In this paper, deposition of PLA filament on an ABS substrate during an ME process is investigated using finite element analysis. A heat transfer finite element (FE) model for the extrusion process is proposed to estimate the parameters of the ME machine for the formulation of a heat flux model. The effects of printing temperature and the stand-off distance on temperature distributions are investigated using the proposed FE model for the extrusion process. The heat flux model is implemented in a proposed heat transfer FE model of single bead deposition of PLA on an ABS plate. From this FE model of deposition, temperature histories during the ME deposition process are estimated. The results of temperature histories are compared with experiments. Using the calibrated FE model, a proper heating temperature of ABS for deposition of PLA is evaluated.

Numerical investigation and design of fully chord supported tubular T-joints

A numerical investigation focusing on the design of fully chord supported cold-formed high strength steel (CFHSS) tubular T-joints is presented in this paper. The nominal yield strengths of the tubular members were 900 and 960 MPa. Square, rectangular and circular hollow sections (SHS, RHS and CHS) were used as the brace members, while SHS and RHS were used as the chord members. The tests conducted by Pandey and Young (2019) [1] were used to calibrate finite element (FE) models developed in this numerical investigation. The developed FE models were capable of replicating the test results, including joint resistances, load-deformation histories and failure modes. In order to determine the compression resistance, axial compression loads were applied through the brace members by fully supporting the chord members along their lengths. These calibrated FE models were then subsequently used for the parametric study, which comprised of a total of 189 FE analyses on T-joints with SHS and RHS braces and 96 FE analyses on T-joints with CHS braces. The nominal resistances calculated from the EC3 (2005) [2] and CIDECT (2009) [3] were used to compare the compression resistances obtained from both the tests [1] and the parametric study. In order to check the applicability of the design rules of tubular T-joints, the nominal resistances from these specifications (EC3 (2005) [2] and CIDECT (2009) [3]) were obtained with and without incorporating the recommended reduction (or material) factors. Through the comparison of 307 joints, including 22 tests (Pandey and Young (2019) [1]) and 285 FE analyses, it has been demonstrated that the existing design rules of T-joints given in the EC3 (2005) [2], CIDECT (2009) [3] cannot be directly used for fully chord supported tubular T-joints of S900 and S960 steel grades with validity ranges of governing parameters exceeding the limits specified in these specifications (EC3 (2005) [2], CIDECT (2009) [3]). Hence, new semi-empirical design rules are proposed in this paper for the observed failure modes, including chord face failure, chord side wall failure and their combined failure modes. Reliability analyses were also performed to check the reliability levels of both the existing and proposed design rules.

Nonlinear Finite Element Model Calibration of a Reinforced Concrete Column with Distributed Plasticity

Nonlinear finite element models, whenever is possible, shall be validated using experimental data. The efficiency of the nonlinear analysis depends on the choice of finite element models parameters. In the present work the calibration is conducted with the goal of observe and minimize the difference between the experimental data and the nonlinear finite element models, using two distributed plasticity modelling approaches. Several models with different parameters of distributed plasticity are used herein and compared against experimental data. The results show that the nonlinear analysis, when associated to a proper modeling strategy, is capable to successfully simulate experimental data.

Experimental and numerical studies on shear behaviour of macro-synthetic fibre reinforced prestressed concrete beams

Experimental and numerical studies on shear behaviour of macro synthetic fibre reinforced prestressed concrete (MSFRPC) beams are presented. MSFRPC beams are tested at a shear span to depth ratio (a/d) of 2.4 to understand the role of macro synthetic polyolefin fibres on the shear resistance and failure modes. The fibre volume fraction of 0.0%, 0.5%, 1.0% and 1.5% are considered as study parameters. A three-dimensional nonlinear finite element (FE) analysis is carried out to understand the influence of fibres on shear behaviour using the concrete damage plasticity model. Tensile constitutive relations of FRC is derived using inverse analysis from fracture test results and used as input in the FE model. A stage-wise analysis is conducted to include the effects of prestressing and applied external shear loads. The results from FE analysis showed a good agreement with experimental results for different fibre dosages. The effect of level of prestressing and varying compressive strength is studied through calibrated FE models. Due to the addition of macro synthetic fibres, no significant improvement in compressive strength is observed. Low fibre volume addition of 0.5% did not produce an appreciable improvement in shear behaviour. However, test and FE results of beams with higher volume fractions of 1.0% and 1.5% significantly improved the post-cracking behaviour, ductility, and ultimate shear resistance of MSFRPC beams.

A cohesive XFEM model for simulating fatigue crack growth under various load conditions

This study presents calibration and validation of a cohesive extended finite element model for fatigue crack propagation in ductile materials. The approach relies on a separation between plasticity around the crack tip and fatigue crack growth at the crack tip such that the influence of plasticity on fatigue driving forces is predicted. This implies that characterization of crack growth requires effective Paris parameters. It is shown that the calibrated model can capture fatigue crack growth behaviour in ductile materials for in-phase and out-of-phase biaxial fatigue loading as well as in-phase biaxial loading with an overload.

Feasibility study for in-situ dynamic testing of structures and geotechnical systems

An evaluation of alternative techniques of in-situ dynamic testing for the calibration of fragility functions and finite element models of existing structures and geotechnical systems subjected to seismic ground motions is discussed in this paper. The cases of excitation of bridge structures, buildings and soils are considered, remembering that also effects on components, non-structural elements and dams can be studied. The advantage of these techniques is to perform in-situ tests on full scale systems in their real conditions and state of maintenance imposing ground motions or effective dynamic excitations, even at low frequencies. A dynamic testing system consisting of a totally independent mobile laboratory has been specifically designed and constructed. Peculiar requirements are necessary to achieve the test set-up, including the development of specific methods to build the reaction system and to prepare the base of the buildings. Finally, a feasibility study to evaluate the capability of the proposed dynamic testing system to study the phenomenon of liquefaction in-situ has been carried out by means of three-dimensional coupled dynamic analysis based on the effective stress approach.

Block shear behaviour and design of cold-formed staggered hole bolted connections

Block shear strength of cold-formed steel bolted connections has been thoroughly investigated in the literature, although the behaviour of block shear with staggered holes has not been studied in detail. It is more complex and apparent that a combination of tension and inclined shear behaviour due to the presence of the staggered holes affects the shear strength and behaviour of the bolted connections. This paper presents an experimental program on the block shear behaviour of staggered hole bolted connections to provide a better understanding on the failure modes. A total of 24 tests using G450 sheets was conducted at the University of Sydney with 1.9 and 2.4 mm thicknesses. Digital Image Correlation (DIC) was employed to capture both the full field of the displacement and the block shear failure mode of the staggered hole bolted connections during testing. A comparison of the experimental strength with existing design equations for block shear with staggered holes in AISI S100:2016 and AS/NZS 4600:2018 is included in the paper. A calibrated Finite Element Model is then developed by the commercial program ABAQUS to validate against the test results and to further provide detailed insights which could not be seen in actual tests (i.e, stress and strain distributions). In the FE simulation, to study the whole range of deformation of the staggered hole bolted connections (i.e., elastic, plastic and fracture stages), a plasticity model and a ductile damage model are applied to the cold-formed steel sheets to represent various stress states in the steel during failure.