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A field-enriched finite element method is proposed in this paper to simulate the failure process of rocks. According to the different types of defects, the proposed method can select the appropriate failure criteria for voids and cracks. Field variables are used to characterize the crack location and to realize the influence of cracks on the physical field of the numerical model. The main features and the capability of the field-enriched finite element method to efficiently simulate the failure process of rocks with different defects are illustrated with some numerical examples. The results show that the field-enriched finite element method proposed in this paper can obtain the crack propagation path which is consistent with other numerical methods and experimental observations. Moreover, the numerical method proposed in this paper has the advantages of simple implementation process and higher computational efficiency and accuracy in some cases. Therefore, it is a promising numerical simulation method.

In this paper, based on the nodal displacement of the crack surface element, a novel node-scheme method is proposed to model the frictional contact problem in the framework of extended finite element method (XFEM). The paper systematically illustrates the novel node-scheme including the fundamentals of the proposed method, the coupled Coulomb's friction model. The novelty of the proposed method is that the node-scheme method is first introduced into the XFEM, it can consider the stress redistribution in the local part of the crack surface, and it has the advantage of solving the locking phenomenon in the numerical simulation of the frictional contact problem. The numerical results show that the proposed method is accurate and applicable to efficiently solve the frictional contact crack problem.

This work deals with the numerical evaluation of the structural response of simply supported (transversally loaded at mid-span) and cantilever (subjected to tip point loads) beams built from a commercial pultruded I-section GFRP profile. In particular, the paper addresses the beam (i) geometrically linear behaviour in service conditions, (ii) local and lateral-torsional buckling behaviour, and (iii) lateral-torsional post-buckling behaviour, including the effect of the load point of application location. The numerical results are obtained by means of (i) novel Generalised Beam Theory (GBT) beam finite element formulations, able to capture the influence of the load point of application, and (ii) shell finite element analyses carried out in the code Abaqus. These numerical results are compared with (i) the experimental values reported and discussed in the companion paper (Part 1) and (ii) values provided by analytical formulae available in the literature.

In this paper, the multi-time-step method (MTS) of time integration is proposed to reduce the computational cost of solving the dynamic interaction of a train-track-bridge coupled system (TTBS). Considering the different domain frequency characteristics of the dynamic responses of the train, track, and bridge, the MTS method decomposes the TTBS into two smaller subdomains: the train-track coupled subsystem with a high domain frequency, and the bridge subsystem with a low domain frequency. A fine time-step and a coarse time-step are respectively adopted for the train-track subsystem and the bridge subsystem to improve the computational efficiency. The two subsystems are coupled by the interaction forces between the track and bridge. Two partition types of the TTBS are introduced and the effect of different decomposition types on the accuracy and efficiency of the MTS method are discussed. The proposed method is validated by comparing the numerical results with field measurement data of a simply supported bridge. A numerical simulation of a train traversing a long-span cable-stayed bridge is used to demonstrate the computational efficiency and accuracy of the proposed method. It is shown that the proposed method is accurate and computationally more efficient than using a uniform time-step for the entire TTBS.

The present paper is concerned with numerical simulation of two-dimensional (2-D) cracks and material interfaces by an effective computational approach. A local mesh refinement in terms of extended finite element method is thus described. The new approach combines a posteriori error estimation algorithm, a local non-conformal mesh connection strategy, and local enrichment. An error estimator based on recovery strain for adaptivity is used; allowing the mesh where it is needed is subsequently refined. Unlike preceding local refined methods, variable-node elements are integrated into the present formulation instead, which aims to treat mismatching problem induced by different scale-meshes in an effective way. The discontinuity and singularity of cracks or material interfaces are captured by local enrichments in terms of partition of unity. Due to existence of different types of elements in the model, a special technique is thus proposed for appropriately and accurately treating numerical integration. We address the developed methodology, assessing its numerical properties and performance through several numerical examples. In particular, discontinuity problems with material interfaces, multiple inclusions, single and multiple cracks are analyzed. The obtained results indicate a high accuracy, low cost and good performance of the proposed method in simulation of 2-D cracks and material interfaces.

A comparative study of three composite implicit schemes including the Bathe scheme (Bathe and Baig, 2005), the TTBDF scheme (Chandra et al., 2015) and the Wen scheme (Wen et al., 2017) is conducted in this paper. The stability and accuracy characteristics of these schemes are studied and compared by analytical and numerical simulation analysis. In the solution of wave propagation problems, a demonstrative dispersion analysis is given and problems are solved to illustrate the capabilities of the schemes for the solution of wave propagation problems as well as the numerical dissipation characteristics of the schemes. The nonlinear dynamic behavior of the Wen scheme is studied by considering commonly used nonlinear dynamic problems where the nonlinear performance of the scheme is exclusively compared with the Bathe and TTBDF schemes. The priority ranks of three presented composite schemes for different types of dynamic problems are obtained by theoretical and numerical analysis.

Damage detection of local and tiny delamination in a laminated composite plate is studied in this paper using piezoelectric patches embedded in composite plate and the energy distribution of structural dynamic responses decomposed in various frequency bands by wavelet packet analysis. This method is based on energy distribution of structural vibration sub-signal and can be in situ implemented using a few piezoelectric patch sensors and actuators embedded in the composite plate. The obtained results show that the method for structural damage detection proposed in this paper is much more sensitive than the existing methods. Using this method, a delamination area of only 0.13% of the total area of the composite plate may be detected. The results show that numerical simulation are quite consistent with experiment results.

In this paper, the space model for train carriages is developed and introduced in dynamic analysis of train–bridge interaction. The rail irregularities described by the power spectral density functions are generated by inverse Fourier transformation. The equations of motion of train–bridge systems are derived and reduced to simulate the dynamic responses of bridges under moving trains. The Newmark’s β integration method is adopted to solve the non-linear coupling equations. Numerical examples show that the method of this paper has high accuracy in simulating train–bridge interactive dynamics.

In a previous paper [Comput. Struct. 46, 905–916 (1993)], a general formulation was presented for the nonlinear material and geometric, instantaneous and long-term nonlinear analysis of prestressed concrete structures. Such a formulation is based on a discrete treatment of the prestressing tendons where both the prestress geometric and mechanic effects are introduced consistently with the displacement formulation of the finite element method. In the present paper the application of this formulation to the nonlinear analysis of prestressed concrete shells of general geometry is discussed. Special concern is devoted to the definition of the space curved shell and tendon geometries, which potentially require large amounts of data preparation. In order to minimize this requirement, a set of automatic procedures have been adopted which, using an analytical description as data, generate a complete work interpolation for both the shell middle surface and the tendon axial curves. Finally, three numerical examples are presented through which, by comparison with existing experimental results, the efficiency and the reliability of the method are shown.

This paper presents a stochastic simulation method which is used to evaluate dynamic characteristics of elastically jointed structures. Due to the joint friction and clearances involved in the analytical model of elastic joints, the conventional numerical simulation can only provide the system performance in certain specific conditions. The effects of dynamic disturbances and other random factors are hardly included. In this research, the vibration process of the jointed structure is simulated through a vibration data generation process, which is based on a newly-developed, theoretical joint model and the stochastic process theory. The vibration pattern and joint contact force can be analyzed from the vibration data. These data are also used to estimate the parameters of a stochastic model so that the system eigenvalues can be evaluated. The stochastic simulation method has been applied to a truss-cell unit structure. The results of the simulation study are shown in this paper. They are compared with experiment results and show a satisfactory comparison.

Inflatable membrane structures with the advantages of light weight, large span, long duration and aesthetical appearance have gained considerable attentions from buildings, super-pressure balloons, airships and deployable antennas. This paper presents a novel computational method for in-situ finite element modeling of inflatable membrane structures based on geometrical shape measurement using photogrammetry for further structural analysis. Firstly, kinematic equations of membrane link structure simplified from the measured inflatable membrane structure are established on force equilibrium between membrane internal and external forces to calculate the tensile forces. Then, computational method for solving zero-stress state is proposed through unloading internal pressure based on equilibrium matrix theory. Finally, true finite element model is established through numerical simulation of reloading internal pressure with considering the zero-stress state as initial model. For verifying purpose, inflated forming and normal working tests of an ethylene-tetrafluoroethylene (ETFE) air-inflated cushion structure were carried out. By comparing geometrical shapes and stress distributions of ETFE cushion between numerical and experimental results, good agreements with 0.72% and 4.76% maximum errors are acquired. These findings strongly confirm the need of in-situ finite element modeling of inflatable membrane structures undergoing long-term service and provide an effective computational method for further structural analysis.

Damage-plasticity models can be used for predicting punching shear behaviour of concrete slabs.FEA results using two damage plasticity models; one implemented in FEAP and the second from ABAQUS are presented.Punching shear FE analysis is sensitive to the representation of the tensile concrete behaviour.Regularization must be adopted to avoid premature predicted failure due to localized cracking. The paper presents numerical simulations of punching shear in a reinforced concrete slab-column configuration formerly tested in the laboratory. A brief description of the test program at the University of Waterloo is reported. For the simulation, a symmetric quarter of the test configuration is employed. Full three-dimensional finite element discretized geometry is considered together with elastic-plastic reinforcement embedded as truss elements in concrete. Two regularized numerical models of concrete, formulated within elastic-plastic-damage theories, are applied. The first one, called gradient damage, is refined by an additional averaging equation where gradient enhancement involves an internal length scale. In the second one, called rate-dependent damaged plasticity model, a viscoplastic strain rate is introduced. The results for the first model implemented in FEAP and the second model from ABAQUS are discussed in detail. Different issues of numerical simulation to properly predict punching shear behaviour in the slab-column configuration are presented.

International audience; In aeronautics, the issue of ice shedding prediction is of prime importance in the assessment of electro-thermal ice protection systems. In this paper, an ice shedding mechanism based on pressure redistribution in the water film formed at the ice/airfoil interface is proposed. This pressure distribution induces a stress concentration that leads to crack propagation in the ice. To determine whether this mechanism is relevant or not, two numerical experiments are performed. The results of these numerical experiments and the influence of a few material parameters are discussed, as well as their limitations and possible consequences arising from some of the hypotheses.The numerical modeling is based on recent works on damage/fracture mechanics which provide a general framework for fracture mechanics computation. The effects of numerical parameters and mesh size are discussed. A mixed mode test case based on experimental data is also performed. This test casehad not been attempted before on this particular numerical method, which therefore serves as further validation.

This paper treats the blast response of a pile foundation in saturated sand using explicit nonlinear finite element analysis, considering complex material behavior of soil and soil–pile interaction. Blast wave propagation in the soil is studied and the horizontal deformation of pile and effective stresses in the pile are presented. Results indicate that the upper part of the pile to be vulnerable and the pile response decays with distance from the explosive. The findings of this research provide valuable information on the effects of underground explosions on pile foundation and will guide future development, validation and application of computer models. Accepted version

Conserving and dissipative implicit algorithm designs in the single-field form via the total energy framework for N-body systems are summarized in this paper which provides new avenues with improved physical interpretation, and can also explain analogous past efforts. We show various algorithm designs via two distinct approaches based on the algorithmic time level consistency theorem, namely, the discrete total energy conservation method, and the classical and normalized time weighted residual methodologies; and therein draw comparisons among the various time-stepping algorithms and features. A simple numerical simulation is shown to demonstrate the pros/cons for the conserving properties of various algorithms.

This paper presents a damage detection technique combining proper orthogonal decomposition (POD) with self-adaptive differential evolution algorithm for structural health monitoring considering environmental variability and measurement noises. The damage detection methodology consists of three stages. Identification of the exact time instant of damage and exact spatial location of damage using proper orthogonal modes constitutes the first two stages. The damage severity assessment is the third stage and is formulated as a constrained optimisation problem, solved using newly proposed self-adaptive differential evolution algorithm. Numerical simulation studies indicate that the proposed method is robust and can be used effectively in SHM applications.

A method to identify both damages in bridge and the vehicular parameters from the structural dynamic responses is presented. A dynamic response sensitivity-based finite element model updating approach is used to identify both the structural damages and the vehicular parameters. The solution is obtained iteratively with the penalty function method with regularization from the measured dynamic responses. The effects of measurement noise, different vehicle models, measurement time duration and modeling error on the identification results are investigated in the numerical simulation. Studies in this paper indicate that the proposed method is efficient and robust for both damage and parameter identification.

This paper addresses accuracy issues of nodal stresses in both finite elements and finite volumes. Strategies to evaluate nodal stresses for finite elements are also briefly discussed. Emphasis is placed on the application of finite volumes to solid mechanics and an overview of recent advancements is presented. Numerical simulation of test problems shows that accuracy of nodal stresses evaluated using finite elements is strongly dependent on the recovery strategy. In all cases, stress recovery at boundary nodal points renders large errors for all non-patch schemes. Contrastingly, finite volumes provide an accurate computation of nodal stresses, including at domain boundaries.

The simulation of the wind action over the CAARC (Commonwealth Advisory Aeronautical Council) standard tall building model is performed in the present work. Aerodynamic and aeroelastic analyses are reproduced numerically in order to demonstrate the applicability of CFD techniques in the field of wind engineering. A major topic in this paper is referred to one of the first attempts to simulate the aeroelastic behavior of a tall building employing complex CFD techniques. Numerical results obtained in this work are compared with numerical and wind tunnel measurements and some important concluding remarks about the present simulation are also reported.

In this paper, sloshing waves have been analyzed for baffled and un-baffled tanks. Numerical simulations were carried out based on volume of fluid (VOF) techniques with arbitrary-Lagrangian-Eulerian (ALE) formulation which adopts the displacement of solid, the pressure and displacement in the fluid as variables to model the coupled system. The response of the coupled system is obtained by using the well-known software ADINA, which offers efficient fully coupled fluid-structure interaction capabilities by finite element method. The results obtained are compared with the available experimental data to demonstrate the reduction of sloshing effects in fluid model.

This paper presents a time domain system identification (SI) scheme for detection of sudden structural damage that occurs during an earthquake. A moving time window technique is proposed to trace abrupt changes in the structural parameters caused by sudden damage. The time window represents a finite time interval, in which the SI procedures are performed assuming time-invariant system parameters. As the time window moves forward, the variation of system parameters in time is identified. The error function is defined as the time integral of the squared errors between measured accelerations and calculated accelerations by a mathematical model. Structural damping is approximated by the Rayleigh damping model, and damping properties as well as stiffness properties of a structure are considered as system parameters. A regularization technique is adopted to alleviate the ill-posed characteristics of SI problems. In the formulation of a new regularization function in time domain, a weighting factor is introduced to balance the relative regularization effect between stiffness and damping parameters. A truncated singular value decomposition scheme is applied to impose the regularization function on the minimization of the error function. Numerical simulation studies are presented to demonstrate the validity of the proposed method.

This paper concerns the numerical simulation of feedback, adaptive feedforward and hybrid (combined feedback/feedforward) control systems on the active control of vibrations of beams with Active Constrained Layer Damping (ACLD) treatments. For the simulation a 1-D beam finite element (FE) model with an arbitrary number of elastic, piezoelectric and viscoelastic layers attached to both sides of the beam is utilized. The damping behavior of the viscoelastic layers is considered by a Laplace transformed Anelastic Displacement Fields (ADF) method. The analyzed case study regards the disturbance rejection of an aluminium beam with a pair of surface mounted ACLD patches. In the design and simulation of the control system a Single-Input Single-Output (SISO) configuration with the output being the velocity at one point of the beam and the input being the control voltage applied into the piezoelectric constraining layers is considered. The case study allows to assess and discuss the outcomes and drawbacks of the feedback and feedforward controllers when used individually and the advantages of the hybrid controller.

In this paper, a novel method of damage identification for beam using artificial neural network (ANN) based on statistical properties of structural dynamic responses is developed. In this method, the changes of variances (or covariance) of structural responses are selected as damage indices for damage identification. Firstly, the feasibility of using the statistical property as damage index is validated theoretically with sensitivity analysis. Then the back-propagation ANN with the change of variance of structural response as input and damage status as output is adopted for identifying the damage in beams. The damage identification for a three-span continuous beam using the developed method is numerically simulated. From the results of numerical simulation in both single damage case and multi-damage case, it is found that the ANN with the statistical property as damage index can correctly detect the damage location and identify the damage extent with high precision. Finally, the conclusion is given that the novel method using the statistical property of structural response as damage index for damage identification is feasible and efficient.

A Lagrangian model for the numerical simulation of fluid-structure interaction problems is proposed in the present paper. In the method both fluid and solid phases are described by smoothing particle hydrodynamics: fluid dynamics is studied in the inviscid approximation, while solid dynamics is simulated through an incremental hypoelastic relation. The interface condition between fluid and solid is enforced by a suitable term, obtained by an approximate SPH evaluation of a surface integral of fluid pressure. The method is validated by comparing numerical results with laboratory experiments where an elastic plate is deformed under the effect of a rapidly varying fluid flow.

This paper presents a new algorithm to simulate theseismic responseofN-story building frames incorporating friction energydissipators; a device per floor is considered. The frames with the dissipators are described by 2Dlumped masses modelswith twodegrees of freedomper floor, namely the horizontal displacements of the main structure and of the dissipators. The proposed algorithm consists of a modification of thelinear accelerationmethod; the main innovation consists of checking at each calculation instant the sliding or sticking condition at each floor, hence, the number of “active” degrees of freedom changes continuously, ranging in betweenN(there is sticking condition at every dissipator) and 2N(there is sliding condition at every dissipator). Some results given by this algorithm are compared to experimental results fromad-hoc testingand to numerical results obtained with the ADINA software package. In both cases, agreement is satisfactory while the proposed method is more computationally efficient.

The response of a building structure to a nearby explosion is complicated by the drastic spatial and time variation of the blast load. Existing studies on the structural responses to explosion effects often employ simplified structural model with assumed loading patterns, such as element-based (beam-column, slab) models, single degree of freedom or lumped mass systems. The validity of a simplified approach depends on whether the governing response and failure mechanisms are well represented in the simplified scheme. For such validation more sophisticated models are required. This paper presents a numerical simulation study aiming to characterize the various structural effects of above-ground explosions. A coupled numerical approach with combined Lagrangian and Eulerian methods is adopted to allow for the incorporation of the essential processes, namely the explosion, shock wave propagation, shock wave-structure interaction and structural response, in the same model. The computational domain extends to the soil around the base of the structure, allowing also for an evaluation of the significance of the ground vibration effect. Results show that for a typical above-ground explosion scenario, the critical structural damage is dominated by air shock loading, while the ground shock induces only some additional vibration whose structural effect is minor. The distribution of structural damage tends to be governed by member level effects on the front face of the structure, whereas the global dynamic response of the system appears to be insignificant. Similar modeling approach may be applied to explore other blast-induced complex response phenomena.

In the design of protective structures, concrete walls are often used to provide effective protection against blast from incidental events. With a reasonable configuration and proper reinforcement, the protective structure could sustain a specified level of blast without global failure. However, the concrete wall may generate spallation on the back side of the wall, posing threats to the personnel and equipment inside the structure. For this concern, it is important to establish appropriate concrete spallation criteria in the protective design. Earlier analytical studies have been based on simplified one-dimensional wave theory, which does not consider the complex three-dimensional stress conditions in the case of close-in explosion and the structural effects. This paper presents a numerical simulation study on the concrete spallation under various blast loading and structural conditions. A sophisticated concrete material model is employed, taking into account the strain rate effect. The erosion technique is adopted to model the spallation process. Based on the numerical results, the spallation criteria are established for different levels of spallation. Comparison of the analytical results with experimental data shows a favorable agreement. It is also shown that the structural effects can become significant for relatively large charge weight and longer distance scenarios.

This paper is concerned with an accurate prediction of the effects of adjacent structures on the blast loads on a building in urban terrain. Blast loadings on structures have typically been evaluated using empirical relationships. These relationships assume that there are no obstacles between the charge and the target. In real situations, the actual blast loads can either be reduced due to shadowing by other buildings or can be enhanced due to the presence of other buildings in the vicinity. Results of the numerical simulations presented in this study for multiple buildings in an urban environment have demonstrated the importance of accounting for adjacent structures when determining the blast loads on buildings. An approach to determining the enhancement factors is described.

In this paper a numerical model is presented for assessing the stress and displacement state of RC structures with textile post-reinforcement. The physical nonlinear computational model is based on layered hybrid finite elements with assumed stress distribution, which are extended by the introduction of an arbitrary number of discrete, coupled parallel reference planes in such a way that deformations perpendicular to the reference planes and shear deformations along the interfaces between the layers may be taken into account on a discrete basis. Besides a verification of the method on the basis of experimental results, practical application possibilities are also demonstrated.

Passive noise control by modification of structural geometry moves more and more into the field of vision for designers. This structural-acoustic optimization shows high potential in minimization of radiated noise especially for thin shell geometries. Since computer systems have been enhanced dramatically in recent years numerical simulation of structural vibration and acoustic field was accelerated significantly. But still the sensitivity analysis represents the bottle neck in computational efforts of gradient-based optimization. Furthermore, the coupling between FE and BE analysis in structural-acoustic simulation of large scale models will occur as an additional challenge because of non-matching meshes. In this paper, a fast method for computation of sensitivities of acoustic properties with respect to shell geometry is presented. Therefore, a concept to parameterize the structural geometry is explained. Additionally, the coupling procedure is simplified to reduce computational effort. Finally, this method is applied to an academic example. The sensitivity of the sound pressure at an internal point of an oblique box is investigated, when one side of this six-sided box is geometrically modified.

The paper presents a numerical model for the simulation of the bearing behaviour of textile-reinforced concrete structures under static load taking into account the specific bond characteristics. For the numerical simulation an assumed strain finite element based on the Reissner–Mindlin shell theory for finite rotations is used. The developed numerical model for textile-reinforced concrete allows cost efficient calculations and faster computer-aided analyses. The model verification is carried out by numerical simulations of experiments on textile-reinforced tension bars and also by simulating four-point-bending tests of textile-reinforced beams with thin-walled cross-sections under various loads. A comparison between the results of the simulations and the results of experiments is presented and discussed.

The spectral representation method has been greatly developed as the performance of computer was enhanced. For the time-domain analysis of long cable-stayed bridge, it is required to simulate wind velocity histories at many points arranged on the overall bridge. However, the number of these points is usually so large that the spectral representation method obviously becomes computationally prohibitive. In this paper, a practical method is introduced to simplify stochastic wind velocity field for long cable-stayed bridges. According to the properties of both the structural type and the vibration mode of long cable-stayed bridge, and considering the correlation characteristics of natural wind, an overall three-dimensional (i.e. three components of natural wind) wind velocity field of a long cable-stayed bridge can be simplified into many one-dimensional (i.e. just one component) wind velocity fields, respectively, along pylons and deck. The wind fluctuation along each pylon can be simulated independently by omitting the wind velocity correlation between one pylon and another. Using the explicitly expressed Cholesky's decomposition of the cross-spectral density matrix, the wind velocity field along the deck can be simulated relatively fast. The FFT (Fast Fourier Transform) technique is adopted to further improve the computational efficiency. As an example, the stochastic wind field of a three-pylon cable-stayed bridge is simulated. The spectrum and correlation characteristics of the simulated samples are checked, which demonstrates that the simulation results agree with the corresponding targets.

The main purpose of this paper is to present the numerical simulation of different strategies for the seismic retrofit of reinforced concrete frames, comparing the obtained solutions with the experimental results, and evaluating benefits concerning their structural behaviour under the seismic action. This work is based on the study of a RC frame, representative of the typical construction of the 70s, which has been submitted to real scale experimental tests at the Elsa Laboratory in Italy, involving the use of some retrofitting techniques. The numerical simulation of such tests, as well as the application of a non-linear dynamic analysis methodology to evaluate the structural behaviour and the structural safety improvement of the various retrofit techniques adopted, is presented. The aim is, therefore, to contribute for developing and calibrating a procedure that enables the evaluation of the efficiency of the different retrofit solutions, their possibilities and fields of application.

Tailored welded blanks allow the combination of different materials and different sheet thicknesses in a single blank, thus letting designers and engineers to fit, in initial blank, local needs of strength or other demands in the stamped component. The selection of the best material combination for a part involves a high number of parameters associated with the technologies used in industry. Sheet metal forming technology is widely used to obtain different type of parts. In these processes a large amount of plastic deformation is generally imposed to the sheet. The complexity of the plastic deformation has lead to the development of numerous techniques to predict or evaluate the formability of the raw materials. In the last few years, important developments have been achieved, based on new theoretical models and experimental validation. In this paper two experimental benchmarks are used to evaluate the ability of tailored welded blanks in the drawing process. In addition, the numerical simulation of such examples was performed and the comparison with experimental results is also presented.

In this paper, the use of the finite element method in conjunction with abductive network is presented to predict an acceptable product of which the minimum wall thickness and the protrusion height fulfill the industrial demand on the T-shape tube hydroforming process. The minimum wall thickness and the protrusion height are influenced by the process parameters such as the internal pressure and the die fillet radius. Different internal pressures combined with various fillet radii are taken into account as the process parameters in this study. A finite element based code is utilized to investigate the material flow characteristics under different process parameters, and the abductive network is then applied to synthesize the data sets obtained from the numerical simulation, then a prediction model is established. From the prediction model, a suitable range of the process parameters for producing an acceptable T-shape tube that fulfills the industrial demand can be found.

A numerical model is described in this paper that can analyse a cantilever beam/column member with partial interaction plating under lateral loading. This type of analysis is complicated due to the relative movement, or slip, that occurs at the interface between the concrete and plate elements. The accuracy of the numerical procedure was verified through comparisons with laboratory tests results. The numerical procedure was found to be numerically stable over the full range of response, including post-peak behaviour. The numerical analyses of plated RC columns also show that steel plating can be used to improve a column’s strength, ductility, or both.

In this paper, a model of the behavior of metallic structures subjected to flexural effects is proposed. The model focuses on the description of failure due to local buckling. It is assumed that the main inelastic phenomena involved in the process: plasticity and local buckling, can be lumped at inelastic hinges. The model takes into account that in planar frames, two local buckling can appear in the plastic hinge region: one due to a positive moment the other one related to a negative moment. The elastic behavior of frame members with two local buckling is assumed as unilateral. The plastic behavior is described using the concept of equivalent moment on a damaged plastic hinge. A new hypothesis, that authors have called “counter-buckling”, is introduced. The counter-buckling concept states that as a consequence of the evolution of one local buckling, the other one results partially blocked. The notion of counter-buckling is used to describe local buckling evolution during cyclic loadings. Finally, the model is verified through the numerical simulation of several experimental tests on frame members and framed structures.

The present paper deals with FE-simulations of damage and failure processes in reinforced concrete structures, with emphasis on the description of suitable material models. For concrete, the generally accepted equivalent strain concept (pseudo-1D) is applied, which allows consideration of arbitrary concrete qualities. In the case of cyclic processes, elastic, plastic as well as micro-damage material phases are considered in an empirical manner, as initially proposed by Bazant and Cedolin [ASCE J. Eng. Mech. 106 (1980) 1287]. Two-dimensionality has been considered by the application of a 2D failure model. Macro-cracking and debonding is treated on the meso-level through special crack elements as computational units of the length of the crack distance. This concept yields crack widths and crack distances with sufficient accuracy and it is also impervious to possible size effects due to the strain localization. The second main issue concentrates on simulation concepts for large structures, elucidating the applied shell elements and the required multi-level-simulation techniques. Finally, exemplary results are presented, demonstrating crack-damage induced response phenomena of a large cooling tower shell up to structural failure.

A long term task of design analysis for a prototype machine, used in plasma fusion research, is described in this paper. The core part of each plasma fusion experiment, the superconducting coils and their surrounding structure, are under consideration here. Specificity and complexity of the task are discussed as well. The R&D activities on the structural system of the experimental device were done in a time spread of over 10 years. For the numerical simulation and analysis of the phenomena inside the structure, the ADINA code was chosen right from start. This decision was mainly guided considering the efficiency of ADINA in solving nonlinear problems with a large number of degrees of freedom. The ADINA code is still most commonly used for numerical simulations on the current project which is presently in the state of manufacturing.

A ‘smart’ mild steel damper is proposed in this paper to provide active damping for seismic control of structures. Smart material, which is bonded to the surface of hysteric dampers, is employed as actuator to exert active control force to increase damping effect for the vibration reduction of structural systems. ‘Smart’ finite element formulation is outlined for the numerical analysis of the proposed control device. Two control algorithms were adopted to regulate active control forces. The results of numerical simulation with two example models show the effectiveness of smart material used for active damping.

According to current Greek and international regulations regarding repair of damage in concrete structures or masonry, epoxy based mortars can be used for these applications. In this paper, the mechanical behaviour of epoxy based mortars under typical laboratory testing conditions such as uniaxial compression, was simulated by means of finite element analysis of two-dimensional models. The analysis was performed in the elastic domain for the aggregates and the elastoplastic domain for the resin. Four elementary models were created and material model values were based on laboratory data. Comparative diagrams of stresses and displacements are presented and compared. The prominent failure mechanism is identified as plastic deformation of the resin material.

The aeroelastic wind forces acting on a streamlined bridge deck are analytically modeled and implemented in a finite element code for the investigation of aeroelastic instability and for structural analysis in non-linear dynamics. The present paper extends a previously introduced model, fully in the time domain, taking into account the “memory effect” of the aeroelastic processes, in order to reduce the computational effort. The implementation is tested on a two-DOF system and on a suspension bridge model.

This paper presents numerical results obtained from finite element simulations of the time-dependent behaviour of moderately loaded patch-repaired reinforced concrete short columns. Patch repair is a structural concrete repair method in which damaged concrete is replaced with one of a wide range of materials. Relative to the concrete substrate, the patch repair materials used in this study had different properties, such as the elastic modulus, shrinkage and creep. A priori, it would appear that simple theory such as the engineer's theory of bending cannot be used to quantify the behaviour of the patch-repaired member. Experimental evidence needed to clarify such issues remains scarce. The finite element simulations performed in this study indicate that shrinkage and creep cause the progressive shedding of the load carried by the patch repair to the concrete substrate. Finite element results compare favourably with the predictions of the engineer's bending theory. Relative to test results some qualitative agreement is observed though there is significant quantitative deviation.

There exist three different lines of computational form finding methods: (i) simulation of hanging models, (ii) numerical simulation of soap films, and (iii) structural shape optimization. The aim of the present paper is to show their differences and common aspects when applied to the special task of maximizing stiffness. The inverse problem of simulation of soap films is formulated in more detail on the basis of differential geometry. The effect of internal pressure is discussed. Several illustrative examples are given.

The numerical simulation of rolling processes requires the coupling of several models that describe different physical phenomena such as the deformation of the work-piece together with its thermo-metallurgical evolution and the thermal evolution of the rolls together with its mechanical deformation. In this paper we develop the coupling between the purely mechanical model of the work-piece and the thermo-mechanical model of the rolls. We test the numerical formulation in the analysis of the hot rolling of steel coils and in the analysis of the hot mandrel rolling of seamless steel tubes.

This paper describes a finite element procedure which simulates the conjugate action of spur gear drives, by approximating both the rotations of gears and the elastic deformations of the load carrying teeth. Drive members are considered as individual subdomains, being able to rotate around corresponding axes, allowing elastic engagements at successive contact points. Discretizing gear motion by imposing incremental rotations on the driver gear, one establishes rolling contact between operating teeth surfaces. The load transmission occurred by the contacting surfaces arises variable elastic deformations which are being evaluated through finite element analysis. Accounting on standard proportions of gears and transmission characteristics of drives, the proposed model formulates a computational design problem by means of a few linearly independent global variables. Considering the necessary cases, the numerical efficiency of the method was examined and time histories of some significant stress components are presented and discussed. The proposed model describes effectively both the tooth loading conditions and the variation of stresses, and constitutes further a potent tool in analyzing gear drives.

A split Hopkinson bar set-up is often used for the dynamic testing of materials. Test execution is relatively simple, and interpretation of test results is considered to be straightforward. Classical treatment of Hopkinson bar test results is based on the assumption of a homogeneous, uniaxial stress state in the specimen. However, non-axial stress components inevitably accompany the axial stress. These stresses have a large influence on the mechanical behaviour of concrete. To investigate the dynamic tensile properties of concrete, a split Hopkinson bar set-up was built. To obtain the full understanding, numerical simulations of the behaviour of the test set-up have been performed. The results are presented in this paper.

A procedure for numerically simulating wind-induced forces on bridge deck sections is presented in this paper. The procedure entails solving the governing flow equations of motion using the finite-difference method. The two-dimensional, unsteady, incompressible, laminar form of the Navier-Stokes flow equations of motion are solved in a body-fitted curvilinear coordinate system. Numerical solution of the flow equations of motion yield the unsteady values of horizontal, u and vertical, v , components of the flow velocity vector, V, as well as the flow field pressure distribution. The surface integral of the wall pressure around the body is then evaluated, in order to obtain the desired wind-induced forces on the bridge deck sections. The procedure has been applied to the bridge deck section of a proposed cable-stayed bridge over the Chesapeake and Delaware canal. The simulated wind forces obtained from using two different grid sizes are presented and discussed. Barring computer memory and computational time constraints resulting from use on an IBM-PC with a 486 micro-processor, the force values seem reasonable when compared with the mean values from wind tunnel testing.

Parametric studies on cable-stayed bridges are performed in the paper for investigating the individual influence of different sources of nonlinearity in such bridges. The sources of nonlinearity in the cable-stayed bridge mainly include the large deflection, beam-column and cable sag effects. The influence of such kind of effects on the analysis and the structural behavior of cable-stayed bridges has been detailedly examined in the study. A finite element procedure for the nonlinear analysis of cable-stayed bridges is first set up, and then detailed parametric studies for the initial shape analysis and static deflection analysis of such bridges are carried out. The numerical results show that in the initial shape analysis the cable sag effect is most important and the other two effects are insignificant. However, in the static deflection analysis of cable-stayed bridges the large deflection effect plays the key role, the beam-column effect is also significant but minor than the large deflection effect and the cable sag effect becomes the least important one.

In this paper, a method called the equivalent addition force method (EAFM) is presented for the problem of elastic-plastic analysis of destructive structures. When the destruction takes place, the structural rigidity will be changed. We transform this kind of change from stiffness into external force, the variation of quantities is the value of equivalent addition force (EAF). Therefore, the finite element stiffness matrix stays unchanged and the computing program is stil conventional. The formulation for the EAF of an elastic-plastic problem is also given. Numerical results of the EAFM compare with those achieved by finite element method (FEM) to demonstrate the utility of the present method.