Structural Component Model Research Articles

Automated Modeling of Three-Dimensional Structural Components Using Irregular Lattices

: Irregular lattices are used to model three-dimensional (3D) structural components consisting of a bulk material, curvilinear reinforcement, and their interface. Domain discretization is highly automated and involves the semi-random placement of nodal points within the domain, followed by Voronoi tessellation of the nodal point set. A technique is given for the Voronoi partitioning of nonconvex domains. For discretizing nonconvex domains, and for effective gradation of nodal point density, a minimum allowable distance between nodes is maintained and the domain is saturated with nodes. To accelerate this computationally expensive operation, a partitioned domain search is used during the filling process. Reinforcement, and its interface with the bulk material, are discretely modeled and freely positioned in the domain, irrespective of the geometry of the irregular lattice representing the bulk material. This method of discretization facilitates model construction, results interpretation, and possible revisions to the model. While the focus is on automated domain discretization and the modeling of reinforcement, elastic properties of the model are demonstrated through examples involving nodal stress calculations and deflection analyses of prestressed concrete beams.

Numerical Modeling of Stainless Steel Structural Components—A Consistent Approach

This article describes numerical modeling of the structural response of stainless steel hollow sections. The aim of the investigation was to develop a consistent approach to the modeling of stainless steel structures. The developed finite element models are more sophisticated than any other reported attempts to model stainless steel structural behavior, with general expressions defined for material stress-strain behavior, enhanced strength corner properties, initial geometric imperfection modes, and amplitudes (local and global), and residual stresses. The general expressions define a consistent means of describing the key input parameters. A compound (two-stage) Ramberg-Osgood model is developed to describe stainless steel material stress-strain behavior in tension and compression. For the prediction of enhanced strength corner properties, a simple, though accurate model is proposed. Characterization of local plate imperfection amplitudes is described whereby a model originally devised for hot-rolled carbon steel cross sections was recalibrated and applied to stainless steel cross sections. Numerical prediction of the key performance measures from tests is achieved with a high degree of accuracy: On average, ultimate load was predicted to within 3 percent and with a low standard deviation; deformation at ultimate load was within 6 percent, but exhibited a higher standard deviation; and the general form of the load-deformation response and the failure modes were similar.

Investigation and Optimization of a Spare Wheel Well to Reduce Vehicle Interior Noise

Optimization of structures with the intention to reduce noise emission has become an efficient tool during the past decade. Various approaches and applications have been published and will be briefly reviewed in this paper. Then, the structural component model of a spare wheel well and the fluid model of a sedan cabin are described. The noise transfer function is defined as the sound pressure level in vicinity of the driver's ear due to a harmonic force excitation at engine supports. The frequency range of 0–100 Hz is considered. In a first investigation, it is tested whether stiffening of the entire structural component really decreases the noise transfer function. It can be seen that this stiffening mainly affects noise emission in the upper frequency range. In a contribution analysis, i.e. analysis of the surface contribution to the noise at the driver's ear, the original model and the stiffened model are compared. This contribution analysis includes frequency ranges by summation of contribution and/or contribution levels. Modification of the structure by design variables consists of modification of the shell geometry, i.e. curvature. Two regions are selected at the bottom of the wheel well. Optimization of 30 design variables leads to a gain of 1.15 dB in the objective function being the root mean square value of the sound pressure level at the driver's ear. Finally, we discuss the results. In most papers on structural acoustic optimization, higher decreases have been reported. An explanation is provided, why this was not possible for the structure that has been investigated here. The new shape, however, seems to be a reasonable choice.

309 3Dデジタイザーと実験データ利用による高精度有限要素モデルの作成法

In this paper, the authors present a method for generating accurate finite element models of complex mechanical structural structures and components using a 3-dimensional digitizer and experimentally obtained modal parameters. The coordinates of many points on the surface of an objective body are accurately acquired using a 3-dimensional digitizer at first. A finite element model is then built up based on a kind of interpolation using the data of the surface. On the other hand, some of the modal parameters of the body are obtained by modal testing. The natural frequencies of interest are tuned with respect to the finite element model by referring the experimental parameters. The structural parameters to be tuned are Young's modulus of individual finite elements in this study.

Probabilistic Capacity Models and Fragility Estimates for Reinforced Concrete Columns based on Experimental Observations

A methodology to construct probabilistic capacity models of structural components is developed. Bayesian updating is used to assess the unknown model parameters based on observational data. The approach properly accounts for both aleatory and epistemic uncertainties. The methodology is used to construct univariate and bivariate probabilistic models for deformation and shear capacities of circular reinforced concrete columns subjected to cyclic loads based on a large body of existing experimental observations. The probabilistic capacity models are used to estimate the fragility of structural components. Point and interval estimates of the fragility are formulated that implicitly or explicitly reflect the influence of epistemic uncertainties. As an example, the fragilities of a typical bridge column in terms of maximum deformation and shear demands are estimated.

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An application of the J‐Q model for estimating cleavage stress in the brittle‐to‐ductile transition

A recent model was proposed by the authors to predict cleavage failure for steels based on a weak link mechanism and a crack tip stress field modified for planar constraint by the J–Q theory. The model uses the distribution of toughness results at a single temperature to predict a toughness distribution at a different temperature and/or geometry. In this model a material cleavage stress is needed to predict when the weak link fracture is triggered. This cleavage stress is a key input for the application of the model but it is not a property that is routinely measured and it is hence not available for most steel alloys. In this paper, a method to estimate the average value of the cleavage stress is presented, based on a characteristic of the model to predict cleavage failure. Examples of cleavage stress are given for several steels and these results are used to predict the toughness distributions for structural component models.

Reduction of pounding effects in elevated bridges during earthquakes

Pounding of adjacent superstructure segments in elevated bridges during severe earthquakes can result in significant structural damage. The aim of this paper is to analyse several methods of reduction of the negative effects of collisions induced by the seismic wave propagation effect. The analysis is conducted on a detailed three-dimensional structural component model of an isolated highway bridge. The results show that the influence of pounding on the structural response is significant in the longitudinal direction of the bridge and significantly depends on the gap size between superstructure segments. The smallest response can be obtained for very small gap sizes and for gap sizes large enough to prevent pounding. Further analysis indicates that the bridge behaviour can be effectively improved by placing hard rubber bumpers between segments and by stiff linking the segments one with another. The experimental results show that, for the practical application of such connectors, shock transmission units can be used. Copyright © 2000 John Wiley & Sons, Ltd.

Modelling nonlinear dynamics of bolted assemblies

The dynamics of threaded fastened assemblies represent a highly nonlinear constrained vibration problem that is nontrivial, but of considerable practical importance. In this paper, a dynamic model of a fastened assembly is developed which incorporates a dynamic fastener model with dynamic structural component models. Simulations from the model reveal that fastener placement in assemblies can be optimized to reduce vibration-induced loosening. This result is fundamentally significant since the current practice for placement and orientation of fasteners in assemblies is generally based on convenience or static load and strength considerations, and not dynamic considerations.

Nonlinear seismic analysis of carquinez strait bridges

This paper discusses the particular features and benefits of ADINA with respect to the requirements of advanced seismic analysis as applied to the Carquinez Strait Bridges in California. Major aspects of earthquake related analyses are discussed, i.e., static lateral push-over analysis, ground motion specification for dynamic analysis, and significant structural behavior phenomena associated with geometric and material properties of the structure. The modeling of typical structural components is presented, and strategies used in the analysis are summarized. Elastic and inelastic, local and global buckling, tension rupture, plastic hinging, and moment rupture, were simulated. Soil-structure interaction effects were captured via nonlinear spring and damper elements. Also, large displacement effects and contact actions were implemented.

A Dynamic Changepoint Model for Detecting the Onset of Growth in Bacteriological Infections

We consider a structural component model based on a random walk that incorporates a drift from an unknown point in time, τ, with the objective of providing an on‐line estimate of this changepoint. The application to detecting bacteriological growth in routine monitoring of feedstuff motivates the analysis, and the ability of this model to be tuned in different ways for different specific applications is the reason for its choice. The changepoint τ is regarded as a parameter and the posterior distribution (or likelihood function) of τ is computed at each time point by running a triangular multiprocess Kalman filter. The values of other parameters in the structural component model are tuned from previous data. The location and width of an 80% posterior interval give both an estimate of the changepoint and the magnitude of the evidence for a change. A more formal decision rule for on‐line and post‐sampling detection is derived by application of Bayesian decision analysis.

Fatigue Test of an Actual Car Body Structure. 2nd Report. Investigation of Strength Evaluation Methods for Spot-Welded Joints.

Fatigue strength evaluation methods for spot welding are studied by the fatigue test of an actual car body. The following results were obtained from the test. (1) The configuration of fatigue fracture on spot welds around the window corner near the supported point of a car body is in fair agreement with those of structural component models of the window corner. (2) The abovementioned fatigue strength of spot welds can be evaluated by (a) the carrying-load values of spot welds based on FEM analysis and by (b) the values of typical stresses measured around the spot weld. Judging from the test results, it was proven that the fatigue strength of spot welds in an actual car body against cyclic load can be estimated by the results of the fatigue test of test pieces and structural component models which were previously reported by the authors.

統計的疲労破壊確率に基づく機械・構造部材の耐疲労信頼性設計手法

The present paper deals with the reliability-based fatigue-proof design based upon a practical viewpoint through correct evaluation of engineering uncertainties caused by use of a limited number of experimental data. To this end is first discussed the distribution properties of the statistical failure probability constructed with the aid of parameter estimators in the Weibull distribution. At the same time, the effect of sample size on the estimation of failure probability is also investigated. Comparison is made between shapes of the distribution function of the statistical failure probabilities based upon a Weibull and a log-normal model in order to clarify which is more practical as the fatigue life distribution model of structural components. Furthermore, discussions are made on how to determine the optimum sample size of the fatigue experiment in order to meet the prescribed level of reliability imposed on structural components. Finally, a simple but important design principle is proposed for the reliability-based fatigue-proof design of structural components with Weibull fatigue life distribution.

複数表面欠陥からの疲労亀裂伝ぱ挙動評価法 ＩＩ 複数表面欠陥付直管試験体の疲労試験結果と亀裂伝ぱ評価結果との比較

It is one of the important subjects to evaluate appropriately the growth of surface cracks to ensure the integrity of a structural component with surface flaws, since the flaws are most frequently detected at the surface of a structural component by non-destructive examinations. Authors have been investigating the growth of surface cracks and the crack growth evaluation method, in which interaction and surface effect in multiple crack growth are considered, was proposed previously using empirical expressions. In the meanwhile, verification tests using structural component models were performed to confirm the validity of the evaluation method. In this paper is described the growth behavior of multiple surface cracks obtained from fatigue tests of straight pipes with multiple surface cracks in the inner surface, and is discussed the applicability of the growth evaluation method proposed in this study and that specified by the ASME Code Sec. E. Reasonable fatigue behavior evaluations were obtained by the proposed method for the straight pipes, whereas the method of the ASME Code Sec. XI gave overly conservative fatigue lives.