3D Nonlinear Finite Element Analysis Research Articles

Nonlinear 3D Finite Element Analysis of a Coupled Soil–Structure System by a Deterministic Approach

Fully coupled soil–structure analyses were performed for a building of strategic importance located in the city of Messina (Sicily, Italy). The structure was built after the destructive 1908 earthquake, also known as the ‘Messina and Reggio Calabria earthquake’, which caused severe ground shaking. A parametric study considering three seismograms of this earthquake was performed. Deep in situ and laboratory investigations allowed the definition of the geometric and geotechnical model of the subsoil. Numerical analyses were performed with PLAXIS3D finite element software (Version 21.01.00.479). The Hardening Soil model with small-strain stiffness was accurately calibrated using laboratory and field data. The dynamic response was investigated in terms of accelerations, response spectra, amplification functions, displacements and stress–strain hysteretic loops. The findings show that many aspects must be investigated for the retrofitting of buildings with shallow foundation in areas characterized by a medium to high level of seismic risk: (i) a key role is played by an accurate investigation of the soil; taking into account the specific conditions of the soil, it was possible to investigate its filtering effects; (ii) the dynamic response of the fully-coupled soil–structure system deviates from the free field-site response analysis; (iii) the results reveal the importance of considering the soil nonlinearity in seismic soil–structure interaction problems.

A NEW PREDICTIVE EQUATION FOR PUNCHING SHEAR STRENGTH OF REINFORCED CONCRETE FLAT SLABS BASED ON NUMERICAL PARAMETRIC STUDY

The paper proposes a new equation for the prediction of punching shear strength of reinforced concrete flat slabs. The basis of the new predictive equation is a detailed numerical parametric study conducted using the nonlinear 3D finite element analysis u

Non-linear 3D finite element analysis of built-up cold-formed steel section beam subjected to four-point bending load

The behaviour of cold-formed steel (CFS) built-up section beams under the flexural load has become an attentive area for search, especially with associated complex failure modes, such as local, distortional, lateral-torsional, and global buckling. Previous studies in this area have primarily focused on the compression capacity of CFS members, neglecting their flexural behaviour. Moreover, the CFS beam flexural analysis is more complex in terms of failure mode form and design. This study conducted A 3D non-linear finite element analysis (FEA) run on ABAQUS software on a CFS built-up section beam that was tested under four-point bending. This study examines the bending response of the built-up beam in terms of its load-bearing capacity, the ways in which it fails, and the stress distribution among its cold-formed steel components. The constitutive material laws for CFS, the screws modelling strategy and the contact interaction between the CFS components were considered in this study. The finite element model was verified by comparing it to the experimental results from a previously published study, focusing on the load–deflection response and how the beam failed. The results demonstrated that the FEA could replicate the flexural response of the CFS built-up section beam with an acceptable level of accuracy. Furthermore, the stress profile evaluation showed that the compression flange was the most affected component during the four-point bending loading. Overall, the FEA model developed in this study is a valid tool for predicting the bending behaviour of a CFS built-up section beam and assessing design variables for this type of beam under flexural loading.

Nonlinear 3D Finite Element Model for Round Composite Columns under Various Eccentricity Loads

Composite columns are often used in constructing high-rise structures because they can reduce the size of a building's columns while increasing the usable area in the floor plan. This research aimed to develop a nonlinear 3D finite element analysis model using the ABAQUS, version 6.13-4, of various round composite column designs with varied multi-skin of tubes for solid and hollow columns subjected to various eccentricity loads (90, 180 mm). Extended data to another 12 specimens of composite columns by numerical method, based on six references experimental data of composite columns. The results of ABAQUS data in this study show that; increasing eccentricity for applied loads causes a decrease in loads to fail for composed columns. The ultimate load of hollow composite sections under eccentricity is lower than solid composite sections under different eccentricity loads. Also, the same results indicated fort eccentricity loads. The same results indicated an increased number of steel layers. The stiffness of concrete is greatly influenced by its strength. When the concrete strength rises, the stiffness of the composite column rises as well. The ratios of concrete compressive strength values according to the reference column (CC1S00 with fc’=31.96 MPa) were (-4.4, 3.1, and 6.5) percent for the specimen (CC1S00) with (fc’=25, 35, and 40) MPa, respectively. The method utilized is in the nonlinear analysis, and the finite element results are in good agreement with the experimental results.

Biomechanical Performance of PEEK and Graphene-Modified PMMA as Telescopic Removable Partial Denture Materials: A Nonlinear 3D Finite Element Analysis.

To assess stress and deformation in telescopic removable partial denture (RPD) frameworks manufactured with polyether ether ketone (PEEK) or graphene-modified polymethyl methacrylate (PMMA), as well as the stress of the underlying mucosa, via nonlinear 3D finite element analysis. The 3D model of a full mandible was merged with a 3D-scanned Kennedy Class I model with bilaterally missing molars. The tissues, the telescopic crowns, and the RPD framework were designed and created using dental CAD software. The model was duplicated, and two materials-PEEK and graphene-modified PMMA-were assigned to the telescopic crowns and their frameworks. A force of 200 N was applied perpendicularly to the molars, and constraints were placed in the mandibular ramus and the inferior border. The generated von Mises stress and deformation of the frameworks, as well as the stresses of the telescopic crowns and mucosa, were also assessed. Statistical analysis of the differences between the tested materials was conducted via an independent samples t test at (α = .05). The von Mises stresses of the telescopic crowns and their frameworks in the graphene-modified PMMA model were significantly higher than in the PEEK model. In contrast, the deformation of the telescopic RPD framework of the PEEK model was significantly higher than the graphene-modified PMMA model. The stresses of the mucosa in both models showed an insignificant difference. PEEK material showed better biomechanical performance than the graphene-modified PMMA in telescopic RPDs.

Stress behavior of an anterior single implant restored with high-performance polymer abutments under immediate and delayed loading: A 3D FEA study.

To evaluate the stress generated on peripheral bone, implant, and prosthetic components while using polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) hybrid abutments in two different loading situations with nonlinear 3D finite element analysis. Standard tessellation language (STL) files of original components were used for the in-silico modeling of implant, standard titanium abutment, and hybrid abutments (PEEK and PEKK). The implant was placed in the bone block to imitate immediate loading, in which a friction coefficient of 0.3 was set between the bone and the implant interface, or delayed loading, where the bone-implant interface was assumed to be perfect. In all models, both a horizontal force (25.5 N) and a 30-degree oblique force (178 N) were applied to the long axis of the implant to the palatal surface of the restoration. The stress distribution was evaluated. While more stress was observed in the prosthetic structures in the PEEK and PEKK models, the stresses on the implant and bone were similar in all models, regardless of the loading situation. Under immediate loading, PEEK hybrid abutments caused excessive stress accumulation on the titanium base abutment. Even though abutment type did not affect the stresses on peripheral bone, PEEK and PEKK abutments generated greater stresses on the implant and the standard titanium abutment accumulated higher stresses. Oblique forces mostly generated greater stress than horizontal forces. Oblique forces on an immediately loaded implant led to stresses higher than the yield strength of a titanium implant when restored with PEEK hybrid abutment.

Non-linear 3D finite element analysis of precast reinforced concrete Beam-Column joint under monotonic static load

This paper presents a three-dimensional (3D) non-linear finite element (FE) analysis for a precast reinforced concrete (RC) beam-column joint under monotonic static load using ABAQUS software. The constitutive material laws for concrete and steel, the concrete-concrete interaction, the concrete-steel bond-slip at beam component, and the modelling of the linking parts of discontinuous main bars were considered in this study. The FE model was validated with experimental results from another published research. The validated FE model was then utilized to parametrically investigate the effect of the connection location and bar linking parts within the connection zone on the load capacity and failure patterns of the beam-column joint. Results demonstrated that the FE model is able of reproducing an identical behaviour to the experimental test. Further, locating the precast connection away from the column face can result in increased load capacity and minor damage at the connection region. Additionally, the bar link parts had a minor effect on load capacity but a significant impact on stress and crack distribution. Overall, the developed FE model can replicate the structural behaviour of the precast beam-column joint connections under the static load, and therefore, it can be used as an effective tool for examining the connection design parameters.

Nonlinear 3D finite element analysis of suction caisson-tower-soil system subjected to horizontal earthquake excitation

Suction caissons are widely used as a promising alternative foundation for offshore structures under variable offshore environments. In this paper, a three-dimensional finite-element model which takes into account soil inelasticity was used to study the seismic behavior of a suction caisson in clay taken from an offshore wind farm in the Hebei province of China. The results showed that the maximum acceleration of the soil increases with increasing depth. There is a distinct amplification for relatively low frequencies when seismic waves propagate to the mudline. It was assumed that the rotation center of suction caisson under seismic conditions was virtually existent. The rotation center was obtained by the proposed formula to explore the movement positions of the suction caisson. The time of the peak of lateral displacement of the lid did not synchronize with that of the changing direction of displacement of the rotation center, indicating that the displacement of the lid can not be a comprehensive assessment of the position state of suction caissons. The point mass at the top of the wind turbine tower was responsible for the increase of vibration amplitude of displacement. • In this paper, a three-dimensional finite-element model taking account of soil inelasticity was carried out to study the seismic behavior of suction caisson in soft clay. A 3D equivalent viscous-spring artificial boundary element is applied to eliminate the unnatural reflection wave generated on the boundary. • It is assumed that the rotation center of suction caisson under seismic conditions is virtually existent and it was obtained by the proposed formula to explore the movement positions of the suction caisson. • The time histories of lateral and vertical displacement were extracted for studying seismic behavior of the wind turbine tower under seismic loading.

Nonlinear 3D finite element analysis of a shear-wave vibrator-ground interaction system

Shear-wave vibrator is a type of equipment usually employed for natural gas exploration, consisting of a vibrating machine which applies dynamic loads to the surrounding soils in order to ease the extraction of the gas. Detailed numerical simulations of these devices are scarce in the literature. Thus, in this paper, a nonlinear 3D finite element numerical simulation has been conducted to investigate the main features of the dynamic response of the vibrator. Nonlinear aspects such as baseplates-soil interaction, soil plasticity, and non-reflect boundary conditions, usually neglected in previous simulations, are considered in this model. The stress distribution, plastic deformation, shear wave propagation, ground force and energy characteristics of the vibrator-ground system are analyzed in detail. Based on the achieved results, an evaluation criterion is developed to quantify the performance of the shear-wave vibrator. Moreover, a parametric analysis has been conducted and the effects of some system parameters, such as excitation frequency, different soil properties and embedded depth, are analyzed and discussed in detail. The results can provide a reference for operating or optimizing the design of shear-wave vibrators.

Non-linear 3D finite element analysis of the anchorage zones of pretensioned concrete girders and experimental verification

This paper focuses on the modelling of the anchorage zone of a pretensioned girder. The finite element software Abaqus was used to create a 3D non-linear finite element model (FEM). This analysis was performed on a full-scale pretensioned girder with end blocks and with various types of strand modelling, where accurate contact properties between prestressing steel and concrete are essential. The model has been validated by comparing the numerical strain results with the strain measurements on a full-scale girder with end blocks, which was produced in a precast concrete plant. At the same time, a parametric study was executed to determine the value of the coefficient of friction between the strands and the concrete and to examine the sensitivity of the input parameters of the model. The results have indicated that an accurate determination of the concrete properties at the time of release is very important. Furthermore, the Hoyer effect is analysed. It is found that the radial expansion of the strand in the finite element model is in good agreement with the theoretically calculated expansion of the strand which demonstrates the accuracy of the finite element model. In addition, it is shown that the Hoyer effect influences the force transfer of two adjacent strands. The aim of this research is to investigate the potential of an alternative FE model of a pretensioned girder based on strand to concrete frictional behaviour, rather than the commonly used models based on an assumed shear stress distribution along the transfer length.

Experimental and numerical performance of shear connections in CLT–concrete composite floor

The hybrid cross-laminated timber (CLT) and concrete system has drawn attention as an attractive application for residential and commercial buildings. However, it is crucial to fully understand the mechanical characteristics of the CLT–concrete composite connections before such a hybrid structure becomes widely applicable. This paper assesses the structural performance (force–slip response, slip modulus, and failure mode) of a CLT–concrete composite by conducting fifteen pushout test specimens, which were designed by using the γ-method (Eurocode 5). In these composite specimens, the CLT floor panels were connected to concrete slabs using common mechanical connectors, and the effect of different connection types, connection angles, the penetration depth of the connector, and concrete topping thickness were investigated. The results show that all of the specimens had good trend in the failure mechanisms with a little crush occurred in the CLT and concrete. The finding revealed that the inclination connectors were appeared as an attractive connector layout for CLT–concrete composite components. Non-linear 3D finite element analysis was also developed to simulate the load-slip behavior of the CLT-concrete specimens under shear load. In general, a reliable non-linear finite element model using ANSYS is a great tool for capturing shear capacity and the overall behavior of the hybrid push-out specimens.

Effects of the Crack Tip Constraint on the Fracture Assessment of an Al 5083-O Weldment for Low Temperature Applications.

The constraint effect is the key issue in structural integrity assessments based on two parameter fracture mechanics (TPFM) to make a precise prediction of the load-bearing capacity of cracked structural components. In this study, a constraint-based failure assessment diagram (FAD) was used to assess the fracture behavior of an Al 5083-O weldment with various flaws at cryogenic temperature. The results were compared with those of BS 7910 Option 1 FAD, in terms of the maximum allowable stress. A series of fracture toughness tests were conducted with compact tension (CT) specimens at room and cryogenic temperatures. The parameter for the Al 5083-O weldment was evaluated to quantify the constraint level, which is the difference between the actual stress, and the Hutchinson-Rice-Rosengren (HRR) stress field near the crack tip. Nonlinear 3D finite element analysis was carried out to calculate the parameter at cryogenic temperature. Based on the experimental and numerical results, the influence of the constraint level correction on the allowable applied stress was investigated using a FAD methodology. The results showed that the constraint-based FAD procedure is essential to avoid an overly conservative allowable stress prediction in an Al 5083-O weldment with flaws.

Investigation on Strengthening Approaches Adopted for Poorly Detailed RC Corbels

Poor detailing of the position of bearing pad over reinforced concrete (RC) corbel may lead to premature failure, which is undesired and structurally vulnerable. An appropriate retrofitting solution is necessary to ensure the functionality of such RC corbels. Considering the growing popularity of external carbon fiber-reinforced polymer (CFRP) in retrofitting, this research examines the effectiveness of an externally wrapped unidirectional CFRP sheet and compares its performance against traditional retrofitting methods. Moreover, it is intended to fulfill the lack of extensive research on external CFRP application for corbel strengthening. A total of eight medium-scale corbel specimens were tested on vertical load. Observed premature failure due to placing the bearing pad near the edge of corbel was verified and the effectiveness of the proposed structural strengthening solutions was studied. Experimental results show that although the loading capacity of the damaged corbel due to the poor detailing of bearing pad position could not be fully recovered, the external CFRP wrapping method demonstrated superior performance over RC jacketing and was able to prevent localized failure. Further study based on non-linear 3D finite element analysis (FEA) was carried out to identify the governing parameters of each retrofitting solution. Numerical studies suggested important parameters of various retrofitting alternatives for higher capacity assurance.

Nonlinear 3D finite element analysis of soil–pile–structure interaction system subjected to horizontal earthquake excitation

The dynamic response of a seismic soil–pile–structure interaction (SSPSI) system is investigated in this paper by conducting nonlinear 3D finite element numerical simulations. Nonlinear behaviors such as non-reflecting boundary condition and soil–pile–structure interaction modeled by the penalty method have been taken into account. An equivalent linear model developed from the ground response analysis and the modified Drucker–Prager model are separately used for soil ground. A comparison of the two models shows that the equivalent linear soil model results in an underestimated acceleration response of the structure under this ground shaking and the soil behavior should be considered as a fully-nonlinear constitutive model in the design process of the SSPSI system. It was also observed that the dynamic response of the system is greatly affected by the nonlinearity of soil–pile interface and is not sensitive to the dilation angle of the soil. Furthermore, the effect of the presence of pile foundations on SSPSI response is also analyzed and discussed.

Affecting aspects on the behaviour of frame joints

The variation of reinforcement details, confinement and joints angle are considerable factors which affect the ultimate limit moment of joints and joints efficiency. The variation of joint size is another factor that significantly affects the ultimate limit moment of joints and frame joints efficiency. These previous factors were not considered in design. Corners may be subjected to closing moments, which subject to tensile stresses in the outside of the corner, or to opening moments, which cause tensile stresses in the inside of the corner. The last type of moments arise more detailing problems. Opening joints may be found in retaining walls water tanks, open channels, bridge abutments, high rises due to wind effect, frame structures, etc. in the other hand the closing joint may be found in two hinged and fixed frames and underground water tanks. Hence two types of joints should be compared.The presented paper introduces an experimental and analytical study in order to investigate the effect of reinforcement details, confinement, joints size, joints angle on the frame joints efficiency and comparison between closing joints and opening joints. Experimentally, a total of eleven specimens were tested under vertical load. All specimens were tested up to failure and the behaviour was fully monitored. Moreover, a nonlinear 3D-finite element analysis was established using ABAQUS program and verified with the experimental results in order to give design recommendations for those structural elements.

Non-linear 3D finite element analysis of full-arch implant-supported fixed dentures

Despite the necessity for faster clinical protocols for immediate loading of implant-supported dentures, there is a lack of biomechanical studies to confirm the rigid splinting effectiveness. We compared the stress in mandibular full-arch implant-supported fixed dentures under immediate loading through three-dimensional finite element analysis. Edentulous human mandible models were restored with a 4-implant fixed denture. Implants were splinted with a metallic framework and submitted to conventional loading (group A—control), with acrylic resin and submitted to immediate loading (group B), with a metallic framework and submitted to immediate loading (group C), and with acrylic resin and a prefabricated distal bar and submitted to immediate loading (group D). Models were supported by masticatory muscles. A 100-N oblique load was applied on the first molar. Group A presented the lowest stress and implant displacement values, whereas group D showed the highest values. In bone, groups under immediate loading exhibited the highest stress, whereas the group experiencing conventional loading showed an approximately 50% reduction. All groups submitted to immediate loading presented similar stress values in peri-implant bone. The loading protocol influenced the stress and implant displacement, but the design of the fixed denture did not affect the stress in the peri-implant bone. Rigid splinting of implants submitted to immediate loading is not essential for treatment success.

Effect of Lüders Plateau on Fracture Response and Toughness of Pipelines Subject to Extreme Plastic Bending

The reeling technique presents an economical pipeline installation method for offshore oil and gas applications, especially for thick-wall (low D/t) pipelines. During reeling, the pipe is subjected to large plastic bending strains up to 3%. In thick-wall pipes, the tensile fracture response of the pipeline/girth weld would normally be the governing limit state. Seamless line pipes are preferred for the reeling applications in which the Lüders plateau is often exhibited in materials stress-strain response. In this paper, the fracture response of such pipelines is investigated from a continuum perspective using a nonlinear 3D finite element analysis. A typical pipeline with a hypothetical defect is considered, with the material having a range of Lüders strains and strain hardening indices. Results show that the Lüders plateau modifies the shape of the moment-strain response curves of the pipe, as well as the J-integral fracture response. It is observed that the response is always bounded between two limiting material models, which are (i) the elastic-perfectly plastic stress-strain response and (ii) the conventional elastic-strain hardening plasticity response, without a Lüders plateau. Also, the Lüders plateau was observed to decrease the crack opening stress ahead of the crack tip and thus the crack tip constraint. On the other hand, the presence of a Lüders plateau elevates the near tip plastic strain and stress triaxiality fields, thus promoting ductile fracture. A micromechanical damage integral model coupled with a modified boundary layer analysis was incorporated to study this aspect. Based on the findings of this study, it is believed that the presence of Lüders plateau could significantly alter the fracture response and toughness of pipes subject to relatively high strains.

Thermal and Mechanical Characterization of High Power GaN Packages

The typical package available for high power GaN application has the devices directly attached onto a metal flange, which could contribute significantly to the overall thermal resistance. This paper discusses an alternative approach to packaging both single and multiple devices through a heat spreader, which could potentially improve thermal performance and bring significant benefits to assembly in yields and cost. However, the heat spreader could also introduce significant CTE mis-match and potential concerns in reliability. Nonlinear 3D finite element analysis (FEA) was conducted to characterize the thermal performance and evaluate mechanical/reliability concerns. Thermal modeling considered single and multiple die applications, and the results show13–15% thermal improvement with the copper heat spreader. Mechanical analysis focused on the thermal loads of the die attach and solder reflow processes. It reveals that the die attach process is more critical as shown in the higher stress due to higher thermal load, but stress/strain levels appear to be acceptable. Thus, this alternative approach could be a viable solution.

Punching Shear of Two-way Slabs Retrofitted with Prestressed or Non-prestressed CFRP Sheets

This study presents punching shear behavior of two-way slabs strengthened with prestressed or non-prestressed carbon fiber reinforced polymer (CFRP) sheets. Four two-way slabs (2360 × 2360 × 150 mm3) with a steel reinforcement ratio of 1.44% are tested under concentric load. All slabs exhibit a punching shear failure mode. The strengthened slabs show an increase of up to approximately 20% in load-carrying capacity and an increase of up to 25% in cracking load with respect to the unstrengthened control slab. A detailed stress analysis in reinforcement is conducted along the loading span of the slabs, including the critical shear perimeter surrounding the column stub. The effective strain zone near the slab—column connection, where a sudden increase of strains in the reinforcement is observed, is also studied. The development of shear stresses in the vicinity of the slab—column connection is examined. A non-linear 3D finite element analysis is conducted and analytical predictive models for the punching shear failure are evaluated as well.

Finite element investigation of the structural behaviour of deck slabs in composite bridges

This research studies the structural behaviour of bridge deck slabs under static patch loads in steel–concrete composite bridges and investigates compressive membrane action (CMA) in concrete bridge decks slabs, which governs the structural behaviour. A non-linear 3D finite element analysis models was developed using ABAQUS 6.5 software packages. Experimental data from one-span composite bridge structures are used to validate and calibrate the proposed FEM models. A series of parametric studies is conducted. The analysis results are discussed and conclusions on the behaviour of the bridge decks are presented.