Material Nonlinear Finite Element Research Articles

Global Resistance Methods for the Design of Fiber-Reinforced Concrete (FRC) Beams with Material Nonlinear Finite Element Analysis

This article explores the application of the global resistance methods (GRMs) on the design of hybrid glass fiber-reinforced polymer (GFRP) and steel fiber-reinforced concrete (SFRC) beams. Addressing challenges posed by GFRP-reinforced beams, this study aims to assess the impact of material uncertainties on the behavior of such hybrid beams. The investigation involves the experimental testing of I-shaped SFRC beams, which are used to develop and validate nonlinear finite element analysis (NLFEA) models. These models incorporate material non-linearities while minimizing uncertainties related to modeling assumptions. Through the application of GRM, the study evaluates the global resistance safety factor, offering insights into the structural performance of hybrid reinforcement SFRC beams. Ultimately, this research seeks to facilitate a transition from traditional localized approaches to more accurate and comprehensive analyses for the design of hybrid reinforcement SFRC beams, contributing to the advancement of structural engineering by promoting safer, more resilient, and sustainable construction systems.

Modelling of fracture intensity increase due to interacting blast waves in three-dimensional granitic rocks

The complexity of the physics of rock blasting is a longstanding modelling challenge. This work presents in detail a three-dimensional, material non-linear finite element based model for wave propagation, combined with a postprocessing procedure to determine the fracture intensity caused by blasting. The rock is described with the Johnson–Holmquist-2 constitutive model, an elastoplastic-damage model designed for brittle materials undergoing high strain rates and high pressures and fracturing; it is also combined with an instantaneous tensile failure model. Additionally, material heterogeneity is introduced into the model through variation of the material properties at the element level, ensuring jumps in strain. A detailed algorithm for the combined Johnson–Holmquist-2 and tensile failure model is presented and is demonstrated to be energy-conserving, and is complemented with an open-source MATLABTM implementation of the model. A range of sub-scale numerical experiments are performed to validate the modelling and postprocessing procedures, and a range of materials, explosive waves and geometries are considered to demonstrate the model’s predictive capability quantitatively and qualitatively for fracture intensity. Fracture intensities on 2D planes and 3D volumes are presented. The mesh dependence of the method is explored, demonstrating that mesh density changes maintain similar results and improve with increasing mesh quality. Damage patterns in simulations are self-organising, and form thin, planar, fracture-like structures that closely match the observed fractures in the experiments. The presented model is an advancement in realism for continuum modelling of blasts as it enables fully three-dimensional wave interaction, handles damage due to both compression and tension, and relies only on measurable material properties.

An appraisal of the Vierendeel mechanism capacity of cellular beams with sinusoidal openings

The aim of this research is to investigate the performance of castellated beams with sinusoidal openings against Vierendeel mechanism (VM). Material nonlinear finite element (FE) analyses were conducted in two beams subjected to four-point bending with geometries selected to exhibit the desired plastification mode. Results of simulations revealed failure mode associated with the formation of four predominant plastic hinges along with shear yielding of the web-post necked region. Differently from the usual castellated beams with hexagonal or cellular openings, the critical hinges did not form at the ‘corners’ around a single opening, but at the innermost and outermost ‘corners’ at shear span. A significant stress redistribution could also be observed during the plastification process. The observation of a unique diagonal stress pattern along the web of the analyzed beams inspired the development of a simple two-dimensional model to predict the performance. A simplified nonlinear procedure was successfully developed to assess the evolution of plastification process with loading, with good agreement with the FE model and with an experimental result reported elsewhere in literature. Finally, it is shown that the current design guidelines for castellated beams (hexagonal and cellular) are not readily applicable to beams with sinusoidal openings for assessment of VM capacity.

Finite element simulation of fixed dental prostheses made from PMMA -Part II: Material modeling and nonlinear finite element analysis.

Material characteristics can change significantly with increasing chewing velocity. As these in-vitro examinations are very time-consuming and cost-intensive, the application of finite element analysis (FEA) offers a suitable alternative for predicting the material behavior of complex specimen geometries under clinically relevant loads. Although FEA is applied within numerous dental investigations, there are only few studies available in which a nonlinear FEA is validated with real experiments. Therefore, the aim of the present study was to predict the mechanical behavior of a clinically close three-unit temporary bridge composed of polymethyl methacrylate (PMMA) in the left upper jaw with nonlinear FEA and to verify the prediction through validation experiments. In conclusion, simplifying assumptions of linear elastic material properties for polymeric materials should be avoided in FEA studies, because rate dependencies, stress relaxation and plastic flow are not considered. Additionally, precise preliminary investigations for material characterization are necessary.

Three-field mixed beam-column finite element for geometric and material nonlinear analysis

A mixed element (3fME) for geometric and material nonlinear finite element analysis of plane skeletal structures is presented, which can reach any predefined accuracy with only one element per structural member. This element is based on the 3-field approach−an application of the Hu-Washizu principle−directly approximating the fields of displacements, strains and stresses. The presented formulation considers both (i) geometrically nonlinear behavior−by including the second-order term in the strain-displacement relations and establishing equilibrium in the deformed configuration−and (ii) materially nonlinear elastoplastic behavior, at the fibre level, automatically handling the axial-bending interaction. The illustrative examples include both compression- and tension-bending interaction, and compare the accuracy of the novel finite element with published results.

WITHDRAWN: A new approach of material nonlinear finite element analysis

Abstract In this article, a novel approach is proposed for solving material nonlinear analysis problems in which a torsion problem is solved. A torsion specimen was tested in the lab and with the experimental data, shear stress and shear strain are first defined. It is to be noticed that in the basic analysis procedure, linearity assumptions are nowhere used. For example, use of shear modulus is eliminated in the basic formulation. Instead, shear stress function and shear strain functions are used as the material input. These shear stress and shear strain functions are derived from the experimental torsion-rotation data. The methodology gives ideal result, either it is linear or nonlinear range of the loading condition, with much more accuracy than the conventional linear analysis approaches. It could be realized that the methodology could be regarded as stress-based structural analysis procedure.

An optimum indeterminate strut-and-tie model for reinforced concrete corbels

The failure behavior of a reinforced concrete corbel is complicated due to the shear span-to-effective depth ratio, reinforcement patterns, load conditions, and material properties. In this study, an optimum first-order indeterminate strut-and-tie model that reflects all characteristics of the failure behavior is proposed for the rational design of reinforced concrete corbels with a shear span-to-effective depth ratio of less than 1.0. A load distribution ratio that transforms the indeterminate strut-and-tie model into a determinate model is also developed to help structural designers design reinforced concrete corbels using the strut-and-tie model methods of current design codes. For the development of the load distribution ratio, a material nonlinear finite element analysis of the proposed first-order indeterminate strut-and-tie model was conducted repeatedly by changing the combination of primary design variables of the corbels. To examine the validity of our results, the ultimate strengths of 294 reinforced concrete corbels tested to failure by other investigators were predicted using the proposed strut-and-tie model with the load distribution ratio, the existing determinate strut-and-tie models representing arch and truss load transfer mechanisms, and the American Concrete Institute 318 conventional design method based on a shear friction theory. The ultimate strengths predicted by the proposed strut-and-tie model agreed fairly well with the experimental results. The ratio of the experimental strength to the predicted strength (and coefficient of variation) was 1.09 (28.0%), implying that the proposed strut-and-tie model can represent the load transfer mechanisms of corbels most appropriately.

Short sisal fiber reinforced recycled concrete block for one-way precast concrete slabs

This work is dedicated to the assessment of the structural performance of a new lightweight block for one-way precast concrete slabs made of short sisal fiber reinforced concrete (SSFRC) containing natural and recycled aggregate. The influence of the sisal fibers and recycled aggregate on the physical and mechanical properties was assessed experimentally, with clear benefits of fiber reinforcement on the post-cracking flexural capacity, while the higher water absorption of recycled aggregates had favorable impact on the compressive strength mainly in the FRC. Flexural tests were carried out on SSFRC blocks, as well as on ceramic and expanded polystyrene (EPS) blocks used commercially. The SSFRC blocks presented higher load and deflection capacity with much more ductile behavior, and with a geometry favorable for the passage of infrastructures. Slab panels including SSFRC, ceramic and EPS blocks were tested under four point bending configuration to assess the benefits of the new SSFRC block in quasi-real slab conditions. The results of these tests demonstrated the best structural performance of the SSFRC blocks over the other considered commercial solutions, not only in terms of initial stiffness, but also for the load at serviceability limit deflection conditions (average increase of 23%) and yield initiation (average increase of 38%); The observed continuous crack pattern crossing the SSFRC blocks and the main precast RC beams demonstrated the potentialities of these blocks to contribute for the structural performance of this type of slabs. Material nonlinear finite element simulations were carried out to derive, by inverse analysis, the values of the fracture mode I parameters of SSFRC. This multidirectional smeared crack model was also used to simulate the behavior of the composite materials and the SSFRC blocks, and the obtained level of accuracy has demonstrated the adequacy of the adopted inverse analysis strategy. A Finally, a parametric study was carried out to preview the potentialities of these new SSFRC blocks for this structural application, having been verified that a SSFRC block of 12 mm thickness and 250 mm height, of about 10 kg, is capable of accomplishing the standard recommendations, constituting a competitive and efficient solution for this market segment.

Experimental and numerical analyses of the ultimate compressive strength of perforated offshore tubular members

Tubular steel members are widely used as structural elements in offshore units. The strength capacity and design formulas for intact members, subject to axial compressive forces, have been thoroughly investigated. However, there are few studies on the behavior of perforated tubular members from offshore aged units and on their remaining load capacity assessment. Perforation damage leads to deterioration of strength capacity and life-time shortening of the structures. The aim of this paper is to present an experimental campaign and a numerical finite element model to obtain the ultimate strength of tubular structures with circular perforated damage subjected to axial compression. In the experimental program fifteen tubular scaled specimens are tested and results are compared with the ones from geometrical and material non-linear finite element model considering reconstructed geometries, variable thickness distribution and actual material stress-strain curves. Shell elements are used and the finite element meshes are obtained from detailed external wall 3D laser scanning of the experimental samples and ultrasonic thickness measurements in several cross-sections. Spatial thickness interpolation is performed to define the thickness in all meshed nodes. Results from numerical model analyses demonstrate considerable accuracy and good agreement with those directly measured from experimental perforated tubular member's samples in terms of axial load-displacement and strains. From the results, it has been concluded that the perforation size is the most important variable in determining the extent of the compressive strength degradation.

11.18: Seismic analysis of innovative hybrid steel concrete coupled walls

ABSTRACTAn innovative hybrid steel concrete coupled wall made by a single reinforced concrete wall connected to two steel side columns by means of dissipative steel links is considered in this study. Such a hybrid system is conceived to take advantage of the stiffness of the reinforced concrete wall and of the dissipation capacity of the steel links acting as dissipative fuses that can be replaced if damaged. The performance of the studied structural system under seismic conditions is assessed by means of multi‐record nonlinear incremental dynamic analysis. To this end a set of buildings is designed following a recently proposed ductile design approach and varying two parameters: the building height and the degree of coupling between the steel columns and the reinforced concrete wall. A material and geometric nonlinear finite element model developed within an open source software is introduced and the main results of the numerical analyses are presented to provide insight into the expected seismic response. Overall, the outcomes of the numerically simulated response results indicate that the proposed hybrid steel concrete coupled wall has interesting potentialities as seismic resisting system being able to effectively exploit the lateral stiffness of the RC wall as well as the dissipation capacity of the steel links.

03.17: Design of haunches in structural steel joints

ABSTRACTThe paper presents research into the advanced design of stiffeners in structural steel joints. Experimental results of six specimens of haunches with and without flanges are presented. Three specimens are without flanges and three specimens are supported by additional flanges. Flanges differ in stiffness to observe the increase of haunch resistances and its effect on buckling shapes.Haunches with and without flanges are validated by numerical model to tests and resistances are calculated and evaluated. The research finite element model (RFEM) is studied by material and geometrical nonlinear finite element analysis with imperfections under the actual stress conditions and validated on the measured experimental data. The quality of prediction is demonstrated on the comparison of load‐deflection curves and failure modes. The stability analysis of a joint with a haunch is used for design Component Based Finite Element Models (CBFEM) of complex joints. RFEM allows verifying the design FEM model (DFEM) and component based FEM model (CBFEM) developed for the design of complex joints in steel structures. To avoid local buckling of slender plates in CBFEM a design procedure is proposed and verified on research finite element model (RFEM). It is proposed to use a combination of material nonlinear analysis without imperfections with buckling analysis in CBFEM. The verification is shown on an example of a haunch in a welded portal frame joint. The stiffener is studied by numerical analysis, resistances and critical loads are determined in RFEM and CBFEM and results are compared. A numerical study illustrates the effect of the haunch's thickness on the joint's resistance.

Design of haunches in structural steel joints

The paper presents research in design of haunches in structural steel joints. Experimental results of six speci­mens of haunches with and without flanges are presented. Three specimens are without flanges and three specimens are supported by additional flanges. Flanges differ in stiffness to observe the increase in haunch resistances and the effect on buckling shapes. The research finite element model (RFEA) is studied by material and geometrical nonlinear finite element analysis with imperfections under the actual stress conditions and validated on the measured experimental data. The validity is demonstrated on the comparison of load-deflection curves, failure modes, stress distributions and yield line patterns. The stability analysis of a joint with a haunch is related to the research into component based finite element models of complex joints. The input and the results of the research finite element model are summarised in a benchmark case of a haunch with a flange. A numerical study illustrates the effect of the flange stiffness on the joint’s resistance. The effect is demonstrated on a simple arrangement with triangular stiffeners and on a beam-to-column joint. The main goal of the research is to verify proposed design procedure for stiffeners in steel joints.

Response sensitivity of material and geometric nonlinear force‐based Timoshenko frame elements

SummaryResponse sensitivity is an essential component to understanding the complexity of material and geometric nonlinear finite element formulations of structural response. The direct differentiation method (DDM), a versatile approach to computing response sensitivity, requires differentiation of the equations that govern the state determination of an element and it produces accurate and efficient results. The DDM is applied to a force‐based element formulation that utilizes curvature‐shear‐based displacement interpolation (CSBDI) in its state determination for material and geometric nonlinearity in the basic system of the element. The response sensitivity equations are verified against finite difference computations, and a detailed example shows the effect of parameters that control flexure–shear interaction for a stress resultant plasticity model. The developed equations make the CSBDI force‐based element available for gradient‐based applications such as reliability and optimization where efficient computation of response sensitivities is necessary for convergence of gradient‐based search algorithms. Copyright © 2016 John Wiley & Sons, Ltd.

Strength Prediction of Adhesively Bonded Joints using Plastic Zone Size Criterion

The prediction of the strength of adhesively bonded joints has been an issue of considerable interest in literature. This exercise requires numerical techniques combined with experimental programs and matching the two to arrive at a viable criterion. The configurations used for the study are single lap adhesively bonded joints between (i) aluminium (Al) – aluminium (Al) and (ii) carbon fibre reinforced composite (CFRP) and aluminium adherends with Redux-319A epoxy. Geometric and material non-linear finite element analysis was conducted using the NASTRAN software package to establish the proposed plastic zone size (PZS) failure criterion. On the same configuration both experimental program for joint strength and numerical analysis were conducted. The plastic zone size corresponding to failure load was initially estimated from Al-Al joints. The same value was used to predict failure load for CFRP-Al bonded joint. The average experimental value and numerical predictions for CFRP-Al joints matched within 7%. This study suggests an alternative method of strength prediction of adhesively bonded single lap joint in presence of inelastic behaviour of adhesive material.

Failure analysis of torsional buckling of all-terrain crane telescopic boom section

Abstract A telescopic boom section (TBS) is a type of slender thin-walled structure equipped in all-terrain cranes. It has an irregular cross-section and bears complex multi-directional loads; thus, local buckling failure is apt to occur under large hoisting loads, sudden rotation brakes or gusts. In this study, the torsional buckling of a TBS under multi-directional loads is investigated. To accurately and quickly predict the buckling load of the TBS, geometric, material and status nonlinear finite element (FE) analyses with implicit and explicit methods were used to study the telescopic boom of an all-terrain crane QAYX. The critical buckling load obtained using the displacement, strain and stress were discussed, in which the load obtained using the stress state transition was closest to the experimental critical buckling load. The implicit method required less computational time and demonstrated a qualitatively good agreement with the strain measurements before reaching buckling failure. The explicit method calculated an accurate deformation when compared with the experimental result and implicit method; however, a large local deformation resulted in the calculation of the implicit method being unable to converge after buckling.

Second-order effects in locally and/or distortionally buckled frames and design based on beam element analysis

In the design of steel portal frames, second order effects are usually accounted for by using a second order elastic analysis to calculate the deformations and internal actions of the frame. In this analysis, one-dimensional beam elements are employed irrespective of whether the cross-sections of members are slender or non-slender. However, frames composed of members with slender cross-sections may buckle in local and/or distortional modes before reaching the ultimate limit state. In this case, the flexural rigidity of the frame is reduced when local/distortional buckling occurs, and as a result it undergoes larger sway deflections than had local/distortional buckling not occurred. The additional second order moments thus caused by local/distortional bucking are not accounted for in current design provisions.In this paper, the additional second-order effects caused by the development of local/distortional buckling are studied by comparing numerically determined ultimate capacities with design capacities. The numerical ultimate strengths are based on previously calibrated geometric and material nonlinear shell finite element models, and the design capacities are determined using the Australian Standard for Cold-formed Steel Structures AS/NZS 4600. A simplified approach to account for local/distortional buckling in beam-element-based design is also proposed. The focus is on portal frames subject to in-plane sway failure.

Structural properties and out-of-plane stability of roller bent steel arches

In contemporary architecture the use of steel arches has seen a significant increase. They are applied in buildings and large span bridges, combining structural design with architectural merits. For arches lacking lateral support (or freestanding arches) the out-of-plane structural stability behavior is the decisive design criterion. However, suitable methods or design rules to assess the out-of-plane structural stability resistance of arches are lacking and the collapse behavior is often unknown. Nowadays engineers have to perform laborious calculations which can lead either to conservative or nonconservative arch designs. This Ph.D. project is aimed at studying the out-of-plane structural stability behavior of steel arches, and developing design rules for these arches. The out-of-plane structural stability behavior was studied by means of geometrical and material non-linear finite element analyses including structural imperfections with ANSYS v. 11.0. The investigation was confined to wide flange circular freestanding arches which are subjected to in-plane vertical loads and manufactured by the roller bending process. The roller bending process is a manufacturing technique by which steel members are bent at ambient temperature into circular arches. It was expected that the residual stresses and mechanical properties (e.g. yield stress, ultimate tensile stress) are altered due to roller bending. Since the alteration of residual stresses and mechanical properties (imperfections) can affect the out-of-plane structural stability of freestanding steel arches, the influence of the roller bending process was studied first. Residual stress measurements and tensile tests were conducted on both straight and roller bent members to assess the influence of roller bending. In addition to the experiments, finite element simulations of the roller bending process were performed in the ANSYS v. 11.0 environment to estimate the residual stress distribution in the arches. Good agreement between the experimentally and numerically obtained residual stresses in roller bent arches was observed. Based on the experimental and numerical studies of the imperfections in roller bent arches a residual stress model and distribution of mechanical properties across the steel bent section were proposed which serve as the initial state of a roller bent arch when assessing its structural performance by means of non-linear finite element simulations. Numerical analyses showed that the residual stresses in roller bent arches have a minor influence on the load carrying capacity. However, the alterations of the mechanical properties can result in a significant reduction of the arch strength The existing column curve formulations as given in EC3 were adapted to include out-of-plane buckling of arches by altering the form of the imperfection parameter. The column curves can give an accurate prediction of the out-of-plane buckling load provided an appropriate imperfection parameter is selected and the non-dimensional slenderness is known. Based on numerous finite element calculations an imperfection parameter curve was derived which was substituted into the column curve formulation rendering a column curve for roller bent arches failing by out-of-plane buckling. Finite element results showed that multiple column curves were necessary to capture the out-of-plane buckling response of arches for various load cases and steel grades. The column curves require the determination of the non-dimensional slenderness represented by the in-plane plastic capacity and out-of-plane elastic buckling load. Since any closed form equations are lacking to approximate these buckling parameters finite element techniques were adopted. For future research it is recommended that closed-form solutions or design graphs should be derived with mechanical models to obtain the elastic-plastic buckling load of freestanding roller bent arches without using finite element analyses.

Local seismic stability of flanged cruciform sections (FCSs)

Flanged cruciform sections (FCSs), as an appropriate alternative for column cross-section in orthogonal moment-resisting frames, need more cross-section specific code requirements in design specifications. To extend the specifications for FCSs, local buckling of webs, flexural ductility under axial compression and cyclic bending moments, and also P–MP interaction relationships have been studied. A validated material and geometric nonlinear finite element model in ABAQUS has been used to perform a comprehensive parametric study on FCSs. The modeling protocol includes a new residual stress distribution, as well as appropriate geometric imperfections. A wide range of web depth-to-thickness ratios is considered to evaluate the current AISC-341 seismically compact limit state. As the web slenderness and axial load have significant effects on the cyclic behavior and ductility of the FCS beam-columns, a new web seismically compact limiting ratio is proposed for FCSs as a function of the axial load to provide the desired ductility. It is shown that taking half of the depth in calculating web slenderness of FCSs and using the current I-section web compactness limitations for FCSs, can be non-conservative. The study shows that the AISC-341 and ASCE-41 P–MP interaction curves for beam columns made from wide flange sections are overly conservative when applied to FCSs. A modified interaction curve is proposed which more accurately represents beam column behavior of FCSs.

Nonlinear Finite Element Analysis on Shear Bearing Capacity of Masonry Wall Strengthened by SGFRP

4 finite element models of ANSYS were constructed according to the masonry wall specimens of the experimental study. A material nonlinear finite element analysis by the finite element calculation software ANSYS on masonry walls strengthened by SGFRP under the horizontal cyclic loads combined with constant gravity loads was performed. The load-displacement curves of the models obtained from ANSYS simulation were described. The ultimate loads of the 3 models strengthened by SGFRP increased significantly, and the fiber length affect the bearing capacity and the deformation capacity of the wall. The results of the nonlinear finite element analysis of the models agree well to the experimental results. Some effective and reasonable reinforcement suggestions are proposed.

Analytical Study on Effect of Floor Slab for Progressive Collapse Resistant Capacity of Steel Moment Frames

Abstract In this study, an improved energy-based nonlinear static analysis method are proposed to be used for more accurate evaluation of progressive collapse potential of steel moment frames by reflecting the contribution of a double-span floor slab. To this end, the behavior of the double-span floor slab was first investigated by performing material and geometric nonlinear finite element analysis. A simplified energy-absorbed analytical model by idealizing the deformed shape of the double-span floor slab was developed. It is shown that the proposed model can easily be utilized for modeling the axial tensile force and strain energy response of the double-span floor slab under the column-removal scenario. Keywords :Progressive collapse, floor slab, finite element analysis, axial tensile force, simplified method † Corresponding author: Tel: +82-31-250-1152; E-mail: corea13@snu.ac.krReceived November 15 2013; Revised January 17 2014;Accepted February 5 2014Ⓒ2014 by Computational Structural Engineering Institute of KoreaThis is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License(http://creativecommons. org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.