Layered Shell Element Research Articles

Numerical Analysis and Simulation of Spatial Concrete Frames after Fire

In order to analyze the mechanical properties under three conditions of fire-damage, rehabilitation and strengthening of spatial concrete frame structures after fire, two novel numerical models are developed in this paper by dividing the cross-sections of beams and columns into a lot of concrete fibers and steel fibers and dividing slabs into several layers along the direction of the slab thickness based on the concept of the fiber element model and the layered shell element model. These two models can consider the distribution of non-uniform temperature in the cross-sections of structural members and the changing of mechanical properties of fire-damaged, rehabilitated and strengthened materials. Besides, the Analytical System of Fire-damaged Concrete Frame (ASFCF) is established through the secondary development of ABAQUS Software that is completed by the programming language of Python. This system is used to analyze and compare the mechanical responses under three conditions of fire-damage, rehabilitation and strengthening of a multi-story, multi-span spatial concrete frame after fire. The results indicate that ASFCF can properly analyze the mechanical properties under three conditions of fire-damage, rehabilitation and strengthening of spatial concrete frames after fire, and it provides valuable references for assessing the residual mechanical properties and the mechanical properties after rehabilitation and strengthening of global concrete frame structures after fire.

Finite element model for NCF composite reinforcement preforming: Importance of inter-ply sliding

A semi-discrete model is proposed for the simulation of non-crimp fabric reinforcement preforming. This approach is based on experimental observations of in-plane shear deformations of the reinforcement, out-of-plane bending and inter-ply sliding during the non-crimp fabric preforming. The experiment highlights strong sliding between the two plies of the non-crimp fabric during forming. The two plies of fibers composing the reinforcement are modeled by two layers of shell elements; the stitches are modeled by bar elements. The relationship between bar and shell elements is managed with a specific contact and anisotropic friction law associated to sliding threshold. This meso-macroscopic approach allows the simulation of industrial part forming in a reasonable computational time. The model shows a good prediction of deformations during the forming on a hemispherical shape. In particular sliding between the two fiber layers of the NCF obtained by the simulation is in good agreement with that measured during the preforming experiment.

Study on Finite Element Modeling Aspects of Delaminated Honeycomb Sandwich Beams

The simulation of damaged honeycomb sandwich structures is an important aspect in the structural health monitoring and prognosis. This paper studies finite element modeling aspects of delaminated honeycomb sandwich structure. The models proposed are 3-D model of the honeycomb sandwich construction using isotropic shell elements and a layered shell element model, both with contact elements defined in between the delaminated skin and core. Case study is conducted on damaged and undamaged metallic sandwich beam with 3-D shell element modeling and layered element modelling. The models are validated using three point bending test of damaged and undamaged beams. Results are compared with the experimental, theoretical and finite element results. The results show that the layered element modeling simulates the stiffness and gives the similar results to that of 3D model in the global responses and is computationally efficient.

Analysis of Reinforced Concrete Slabs with Reinforcements under Partitions with Finite Element Method

There are no clear design standards for the reinforcements or concealed beams under partitions in reinforced concrete slabs which often appear in reinforced-concrete residential buildings. Designers, in most cases, have to rely on engineering experiences after a simple calculation to design such reinforcements or concealed beams. In this paper, we built a finite element model of such reinforced concrete slabs in SAP2000. The element for the plates was layered shell element. By changing the span , thickness and boundary constraints of the plate, the materials of the partition , the diameter of the reinforcements to analyze the force of the plate. Based on results analyzed, we discuss the internal forces of such plates, and offer suggestions for the selection of partitions and design of reinforcements.

Prediction of Natural Frequency of Laminated Composite Plates Using Artificial Neural Networks

The paper is focused on the application of artificial neural networks (ANN) in predicting the natural frequency of laminated composite plates under clamped boundary condition. For training and testing of the ANN model, a number of finite element analyses have been carried out using D-optimal design in the design of experiments (DOE) by varying the fibre orientations, –45?, 0?, 45? and 90?. The composite plate is modeled using linear layered structural shell element. The natural frequencies were found by analyses which were done by finite element (FE) analysis software. The ANN model has been developed using multilayer perceptron (MLP) back propagation algorithm. The adequacy of the developed model is verified by coefficient of determination (R). It was found that the R2 (R: coefficient of determination) values are 1 and 0.998 for train and test data respectively. The results showed that, the training algorithm of back propagation was sufficient enough in predicting the natural frequency of laminated composite plates. To judge the ability and efficiency of the developed ANN model, absolute relative error has been used. The results predicted by ANN are in very good agreement with the finite element (FE) results. Consequently, the D-optimal design and ANN are shown to be effective in predicting the natural frequency of laminated composite plates.

Experimental and numerical investigations of laminated glass subjected to blast loading

Laminated glass is widely used on the outside surface of modern buildings and it can protect the interior of a structure from the effects of an air blast. In this study several numerical models are reviewed and used to simulate the failure of the glass as well as of the interlayer. Layered shell elements with special failure criteria are efficiently employed in the simulations. For the PVB an elastic–plastic material law is used. For the glass, after the numerical failure at an integration point, stresses are set to zero under tension, while the material can still react to compression. If the interlayer reaches the failure criterion of PVB, the concerned element is eroded. Older and new experiments with laminated glass are used to validate the numerical results. The experiments include both the failure of the glass sheets and of the PVB interlayer. It is shown that the layered model can adequately reproduce the experimental results, also in cases where the interlayer fails. Results of a full 3D solid model are also presented and discussed.

Modeling and investigation of elasto-plastic behavior of steel–concrete composite frame systems

This paper presents a mixed finite-element model combining the fibered beam and layered shell elements using the general finite-element program MSC.MARC (2005r2) based on the discussion and comparison of the previous models. The proposed modeling procedure is intended for integrated elasto-plastic analysis of fully connected steel–concrete composite frames subjected to the combined action of gravity and monotonic lateral loads. The model is verified by extensive experiments and examples, and the behavior of composite frames is also investigated intensively. The slab space composite effect and the beam–column semi-rigidity are the two critical factors influencing the structural behavior. These two factors have not been considered simultaneously in some previous models but can be both included in the proposed model. Due to the complex slab space composite effect in composite frames, the previous models with a constant-width effective flange of slab can not trace the actual nonlinear slab behavior, but the proposed model can give accurate results. Since the slip effect between the steel beam and RC slab has negligible influence on the global calculation results of the structural system verified by the calculation examples, the slip effect is neglected in the present study to simplify the modeling procedure and enhance the calculating efficiency. The proposed model possesses good accuracy and broad applicability with simple modeling procedure and high calculation efficiency, and has a great advantage for the large-scale integrated analysis of multistory and high-rise composite frames.

Thermomechanical Analysis System for Building Structures under Fire Based on MSCPATRAN Platform

In order to analyze the behavior of building structures in a real fire, a numerical method is proposed, which employs fire zone model to simulate the fire growing and the temperature distributions in a firing room. Two computer programs are developed to predict the thermomechanical response of the structures, one for thermal response analysis, and another for structural analysis. The structural analysis program contains a fiber beam element and a layered shell element. These elements, validated against data from experimental tests, can be used to predict the response of beam/column and slabs in fire conditions. Based on these programs, a system for analyzing the behavior of structures under fire is developed on MSC/PATRAN platform. The behavior of building structures under fire can be simulated with this system and the results can be used as the reference for the fire safety analysis and assessment of general building structures under fire.

Layered-Shell Element Method of Calculating the Multi-Ribbed Composite Slab’s Elastic Lateral Stiffness

A new method for calculating the elastic lateral stiffness of the multi-ribbed composite slab by ANSYS—the layered-shell element method is introduced in this paper. In the modeling process, there are two ways for establishing the model using element SOLID46: the first refers to regarding the slab as a whole to make arranged layers. While the second type suggests that making arranged layers in each part already separated according to the materials. Especially when there are reasonable hypothesis, the analysis results can guarantee certain precision. By comparison among the two models and the experimental results, no errors with each other have exceeded 5%. The whole model is used for the numerical simulation in view of its briefness. Several factors affecting elastic lateral stiffness are considered, mainly including elastic modulus of the concrete, elastic modulus of the brick, and number of the ribbed-column. From the calculating results, conclusion can be deduced that all of these factors affecting the slab’s stiffness significantly. Along with the factors’ rising, the elastic lateral stiffness of the wall grows up. Basically, the influence factor and the elastic lateral stiffness of the slab present to be linear relationship. It is also meaningful to see that the elastic modulus of the brick plays a very important part in the elastic lateral stiffness of the wall. When compared to the SOLID65 and LINK8 used for the slab’s modeling before, the layered-shell element method is simple in principle, and distinct in conception. Above all, because only one type of element in the finite element analysis is used, it will cost less time when used on building a model of integrated architectural construction.

Experimental and Analytical Studies on the High Cycle Fatigue of Thin Film Metal on PET Substrate for Flexible Electronics Applications

This paper addresses the behavior of thin-film metal coated flexible substrates under high cyclic bending fatigue loading. Polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are widely used substrates in the fabrication of microelectronic devices. Factors affecting the fatigue life of thin-film coated on a flexible PET substrates were studied, including thin-film thickness, film material, bending radius, temperature, and humidity. A series of experiments for sputter-deposited copper and aluminum coated on a PET substrate were conducted. Electrical resistance and crack growth rate were monitored during the experiments at specified time intervals. In addition, a finite element model was built to simulate the bending of thin-films on flexible substrate structure. Layered shell elements were used in the model. Stress intensity and stress distribution across the film were obtained and compared with the experiments. Initial results of copper-coated PET showed a great agreement between the model and the experimental results.

Finite Element Modeling of Guastavino Tiled Arches

An investigation of Rafael Guastavino's arches has been conducted by means of finite element modeling and laboratory experimentation. A novel method of modeling laminated masonry tile construction via the finite element method has been devised. This technique takes advantage of the layered shell element features found in commercially available finite element programs. Historical Guastavino tiles have been tested to obtain material properties. These modem techniques have been employed in conjunction with Guastavino's original empirical design criteria to provide a better understanding of these historically significant structures.

A novel tetrahedal element for static and dynamic analysis of laminated composites

This paper presents a novel approach to formulating finite elements for modelling laminated composites. Most FE systems provide laminated composite elements based upon layered shell elements and some provide layered brick elements, but these require a hexahedral mesh which is difficult to generate for arbitrary geometries. This paper describes a tetrahedral element based on the concept of an equivalent graded material whose properties vary smoothly (rather than stepwise) and whose global behaviour replicates that of the laminate. This allows the possibility of automatically-generated models involving laminated composite behaviour. The element requires a non-standard integration system, and is presented for the cases of elastic, thermoelastic and dynamic behaviour.

Finite-Element Analysis of Reinforced Concrete Flat Plate Structures by Layered Shell Element

A finite-element model for nonlinear analysis of reinforced concrete flat plate structures is presented. A flexible layering scheme incorporating the transverse shear deformation is formulated in shell element environment. Each node of the layered shell element can be specified as either a normal node or a node with shear correction. A three-dimensional hypoelastic material model is implemented to model reinforced concrete. The cracking effects of tension softening, aggregate interlock, tension stiffening, and compression softening in multidirectionally cracked reinforced concrete are incorporated explicitly and efficiently. A flat plate, a flat slab with drop panel, and a large size flat plate with irregular column layout have been analyzed. The influence of the distribution of transverse shear strain on the punching shear failure mode has been identified in the numerical studies. The proposed finite-element model has been proved to be capable of simulating the localized punching shear behavior of slab-column connections and to be suitable for global analysis of structural performance of flat plate structures.

GA-LQR Based Optimal Vibration Control of Smart FRP Composite Structures with Bonded PZT Patches

In the present study a genetic algorithm (GA) based linear quadratic regulator (LQR) scheme has been developed and applied for optimal vibration control of smart fiber reinforced composite structure with surface bonded PZT patches. 3D layered shell elements have been formulated for modeling and analysis of smart fiber reinforced polymer (FRP) structures having piezoelectric sensors and actuators patches. Location of PZT patches have been decided based on the mode shapes and modal analysis has been performed to transform the coupled finite element equation to state space equation. Genetic algorithm has been used to search for optimal [Q] and [R] matrices in order to maximize the control performance while keeping actuator/input voltage within limits. The present control scheme has been applied to study the efficacy of vibration control of structures including doubly curved smart FRP structures. Results obtained from the work show that GA-LQR control scheme is much more effective in vibration control both in term of maximizing the control performance as well as closed loop damping coefficient within allowable actuator voltage.

Nonlinear Analysis of Reinforced Concrete Slabs Using Nonlayered Shell Element

A nonlayered approach is proposed for the finite-element analysis of reinforced concrete (RC) slabs to predict their strengths including the case of combined in-plane and transverse loading. The nonlayered form is derived from the layered Mindlin-type shell element, and the material matrix is derived from the assumed simple stress-strain curves of the materials. The proposed nonlayered approach is simpler than the layered approach. However, the numerical examples show that it is capable of estimating the deflection as well as the strength of RC slabs under both in-plane and out-of-plane loads with acceptable accuracy.

Torsion of honeycomb FRP sandwich beams with a sinusoidal core configuration

A combined analytical, numerical and experimental investigation of honeycomb fiber-reinforced polymer (HFRP) sandwich beam samples subjected to torsion loads is conducted. The sandwich panel considered in this study has unique sinusoidal core geometry in the plane extending vertically between face laminates, and it has been used primarily as decking systems in highway bridges. Using a homogenization process and mechanics of materials approach, the equivalent core material properties for the honeycomb core geometry are found, and the material properties of face sheets are obtained by micro/macromechanics. Equivalent material properties of the core and face sheets are then used to evaluate effective torsional stiffness properties of HFRP panels. The torsional analysis includes the evaluation of core equivalent in-plane and out-of plane shear properties and panel apparent torsional stiffness properties. Finite element models using layered shell elements are used to correlate with the analytical and experimental results for HFRP beams samples in torsion. Two types of models are presented in the finite element simulation: an actual geometry model, where the core and face sheet geometry are defined by layer shell elements, and an equivalent plate model, for which the equivalent material properties of the core and face sheets are utilized. In order to verify the accuracy of the analytical and numerical predictions, several honeycomb sandwich beam samples with sinusoidal core waves oriented along the longitudinal or transverse or vertical directions and with different face sheet configurations are experimentally tested in torsion. The present analysis and characterization procedures can be used in design applications and optimization of honeycomb structures, and they can also be employed to verify or refine in-plane and out-of-plane shear equivalent material properties for the present and other honeycomb FRP panels.

경로의존형 체적제어법을 이용한 철근콘크리트 중공 기둥의 유한요소해석

The volume control method which utilize a pressure node added into a finite shell element can overcome the drawbacks of conventional load control method and displacement control method. In this study, an improved volume control method is introduced for effective analysis of path-dependent behaviors of RC columns subjected to lateral cyclic loading or reversed cyclic loading along with compressive loading. RC shell structures and RC hollow columns are analyzed by discretizing the structures with layered shell elements and by applying in-plane two dimensional constitutive equations for concrete layers and reinforcement layers of the shell elements. The so-called path dependent volume control method as a finite element analysis technique is verified by comparing analysis results with other data including experimental results. The validity and applicability of the modeling technique is also confirmed by the comparison.

Simulation of laminate composites degradation using mesoscopic non-local damage model and non-local layered shell element

Simulating damage and failure of laminate composites structures often fails when using the standard finite element procedure. The difficulties arise from an uncontrolled mesh dependence caused by damage localization and an increase in computational costs. One of the solutions to the first problem, widely used to predict the failure of metallic materials, consists of using non-local damage constitutive equations. The second difficulty can then be solved using specific finite element formulations, such as shell element, which decrease the number of degrees of freedom. The main contribution of this paper consists of extending these techniques to layered materials such as polymer matrix composites. An extension of the non-local implicit gradient formulation, accounting for anisotropy and stratification, and an original layered shell element, based on a new partition of the unity, are proposed. Finally the efficiency of the resulting numerical scheme is studied by comparing simulation with experimental results.

ACTIVE TWIST OF MODEL ROTOR BLADES WITH D-SPAR DESIGN

The design methodology based on the planning of experiments and response surface technique has been developed for an optimum placement of Macro Fiber Composite (MFC) actuators in the helicopter rotor blades. The baseline helicopter rotor blade consists of D‐spar made of UD GFRP, skin made of +450/‐450 GFRP, foam core, MFC actuators placement on the skin and balance weight. 3D finite element model of the rotor blade has been built by ANSYS, where the rotor blade skin and spar “moustaches” are modeled by the linear layered structural shell elements SHELL99, and the spar and foam ‐ by 3D 20‐node structural solid elements SOLID 186. The thermal analyses of 3D finite element model have been developed to investigate an active twist of the helicopter rotor blade. Strain analogy between piezoelectric strains and thermally induced strains is used to model piezoelectric effects. The optimisation results have been obtained for design solutions, connected with the application of active materials, and checked by the finite element calculations.

A layered cylindrical quadrilateral shell element for nonlinear analysis of RC plate structures

This paper proposes a simple and accurate 4-node, 24-DOF layered quadrilateral flat plate/shell element, and an efficient nonlinear finite element analysis procedure, for the geometric and material nonlinear analysis of reinforced concrete cylindrical shell and slab structures. The model combines a 4-node quadrilateral membrane element with drilling or rotational degrees of freedom, and a refined nonconforming 4-node 12-DOF quadrilateral plate bending element RPQ4, so that displacement compatibility along the interelement boundary is satisfied in an average sense. The element modelling consists of a layered system of fully bonded concrete and equivalent smeared steel reinforcement layers, and coupled membrane and bending effects are included. The modelling accounts for geometric nonlinearity with large displacements (but moderate rotations) as well as short-term material nonlinearity that incorporates tension, cracking and tension stiffening of the concrete, biaxial compression and compression yielding of the concrete and yielding of the steel. An updated Lagrangian approach is employed to solve the nonlinear finite element stiffness equations. Numerical examples of two reinforced concrete slabs and of a shallow reinforced concrete arch are presented to demonstrate the accuracy and scope of the layered element formulation.