Three-dimensional Solid Finite Element Research Articles

A nonlinear analytical method for pipeline strain under soil thaw subsidence load in permafrost region

In frozen terrain, the transportation of heated oil triggers thermal soil thaw and collapse, leading to pipeline distortion and breakdown. During substantial ground settlement in such terrains, current strain prediction techniques for pipelines fall short, neglecting significant pipeline bending, non-linear material behaviors, or detailed pipeline-permafrost interplay. To address this, a model focusing on pipeline-soil dynamics is devised, incorporating material non-linearity and pronounced pipeline distortion. This model derives analytical strain solutions for pipelines by aggregating incremental distortions of pipeline components via a strain iteration technique. Concurrently, a three-dimensional solid finite element model is crafted, assessing pipeline strains across varying subsidence zone dimensions, factoring in the complicated permafrost environment. The model's efficiency is affirmed by its less than 3% discrepancy from finite element method results, showcasing its enhanced accuracy and dependability in predicting pipeline strains under extensive soil settlement scenarios.

An experimental and numerical study on the shear performance of friction-type high-strength bolted connections used for CLT-steel hybrid shear walls

One type of friction-type high-strength bolted connections (FHBCs) was developed to connect steel frames to the infilled cross-laminated timber (CLT) shear walls. In the FHBC, an opening was cut in the CLT near the wall-to-beam interface. Two predrilled holes existed within the CLT panel, running vertically from the bottom surface of the opening to the wall-to-beam interface. Two slotted holes were also predrilled on the top flange of the steel beam. Two high-strength bolts were attached to the upper anchor plate installed in the opening and the bottom anchor plate placed below the top flange of the steel beam. By applying the pretension force on the bolts, the CLT panel was pressed against the steel beam, forming the static friction force to resist the shear force along the wall-to-beam interface. In the study, cyclic tests were conducted to evaluate the friction properties of the interface between the infilled CLT wall and the steel beam. The CLT-steel friction coefficient was carefully investigated, which was a critical parameter for determining the maximum static friction force of the FHBCs. Three-dimensional solid finite element models were developed to predict the load-slip behaviors of the FHBCs, and their multi-stage load-slip behaviors were analyzed using the step-by-step method. It is found that the CLT-to-steel interface can perform with considerable shear-resisting capacity and shear stiffness in the pre-sliding friction as well as stable energy-dissipating capacity in its post-sliding behavior. The maximum static friction coefficient and the dynamic friction coefficient of the interface are recommended as 0.55 and 0.50, respectively. When the pretension force is enhanced from 40 kN to 80 kN, for the FHBCs with the three-layer CLT and those with the five-layer CLT, their ultimate shear-resisting capacity increases by 75.85% and 35.67%, respectively. The load-slip curves from the FHBC models exhibit a similar pre-sliding behavior with considerable shear stiffness and shear-resisting capacity. Whereas, the numerical load-slip curves of the post-sliding stage are distinctive between the FHBCs with the three-layer CLT and those with the five-layer CLT.

Study on restraint coefficient of the stirrups-stiffened square concrete filled double-skin steel tube axial compression stub columns

This paper proposes a novel structural design for stirrups-stiffened square concrete-filled double-skin steel tubular stub columns (SCFDST) that offers high capacity and superior advantages in terms of low consumption of concrete and steel, as well as economic efficiency. The study includes an axial pressure test on two sets of 8 SCFDST columns with varying hollow ratios and stirrup ratios, with a specific focus on the influence of stirrups on mechanical properties. Experimental results demonstrate that stirrups significantly enhance the mechanical properties of SCFDST columns with large hollow ratios, including stiffness, bearing capacity, and ductility, with a more pronounced effect observed as the stirrup ratio increases. A three-dimensional solid finite element (FE) model of the SCFDST columns is developed and validated using ABAQUS software and appropriate constitutive models. Parameter analysis is then conducted based on the FE model, revealing that the stirrups not only restrain the concrete itself but also provide additional restraint by limiting the deformation of the steel tube. This improvement effect was more significant in the middle of steel tubes section. When stirrup ratio was 0.015, the steel tube had the highest constraint efficiency on the concrete. The study introduces a constraint enhancement factor to represent the enhanced restraining effect of stirrups on the steel tube, which is incorporated into a fresh equation for determining the maximum bearing capacity (Nu) of SCFDST columns. The derived formula offers clear physical meaning and high accuracy, building upon the existing formula for CFDST columns.

Three-Dimensional Aeromechanical Analysis of Lift Offset Coaxial Rotors: A Helios Test Case

Three-dimensional (3-D) solid finite element analysis (FEA) is used to model and study coaxial helicopter rotors. The 3-D FEA is coupled with a lifting line aerodynamic model with free wake to capture rotor-rotor interactions. Two open-access models are developed: one is the Metaltail (a hingeless coaxial rotorcraft), and the other is the coaxial rotor built from articulated UH-60A-like rotors. The former is the main focus of this work and is developed as an example case for the U.S. Army/DoD rotorcraft simulation software CREATETM–AV Helios, while the latter is merely for a regression test. The analysis is performed on a low-speed transition flight for which qualitative data are available for the Sikorsky S-97 Raider aircraft for comparison. Predictions of performance, airloads, vibratory loads, and 3-D stresses are discussed. In the absence of available geometry or property data of the S-97, this study is primarily meant to serve as a capability demonstration of 3-D rotor structural dynamic modeling for such rotors.

Cyclic behavior of unbonded post-tensioned precast segmental concrete columns fabricated by 3D printed concrete permanent formwork

A 3D printed concrete permanent formwork of composite unbonded post-tensioned precast segmental concrete (3DPCPSC) column is proposed in this research. Its hysteresis performance and the failure mode are researched by quasi-static experiment and compared with the precast segmental reinforced concrete (PSRC) columns. Two interface enhancement methods, stainless-steel-nails internal shear bonds and prestressed steel-hoops external active confinement are proposed, and the enhancement effect and mechanism of 3DPCPSC columns with two interface enhancement methods are studied. Furthermore, the pouring and vibration load of 3D printing concrete formwork is analyzed using a three-dimensional solid finite element model finite element model. The results indicate that the energy dissipation capacity of 3DPCPSC columns is better than that of the PSRC column when the 3DPC formwork does not spall. The largest accumulated energy dissipation of the 3DPCPSC specimen is 1.14 times of the PSRC column. The 3DPCPSC column without interface enhancement has the phenomenon of formwork spalling, the bearing capacity is lower than the PSRC column, and the bearing capacity of the 3DPCPSC columns with two interface enhancement methods is close to or higher than the PSRC column. The initial stiffness of all the 3DPCPSC specimens is larger than the PSRC column. A comprehensive evaluation factor η is proposed to evaluate the hysteretic performance of precast segmental concrete columns. The comprehensive performance of the 3DPCPSC and PSRC is compared by the comprehensive evaluation factor η.

Stiffness and geometry characteristics of flange connection with bolt failure and its influence on rotor dynamics

Flange connection is widely used in aero-engine rotor system. The state of bolt is very important to the stable operation of the rotor, but the impact of bolt failure on the dynamic characteristics of the rotor system is not clear. Thus, the stiffness and geometry characteristics of flange connection with bolts failure and its influence on rotor dynamic response are studied. Firstly, a three-dimensional solid finite element model considering contact characteristics and a stiffness test device for flange connection with spigot are established. The stiffness characteristics and axis bending characteristics of flange connection after bolt failure are obtained by numerical simulation and experiment test. Secondly, the motion equation of the rotor with the characteristics of local stiffness asymmetric and initial bending result from bolt failure of the flange connection is established by a novel modeling method, and the dynamic response characteristics of the rotor are studied; Finally, a rotor test bench with flange connection is established to test the dynamics of the rotor when bolts fail, and its frequency spectrum and orbit characteristics are analyzed. The research results can provide a theoretical basis for simulation and identification of the bolt failure in rotating machinery system.

Calculation and analysis of ampacity and stress of overhead transmission line

To ensure the safe operation of a transmission line, it is necessary to study the radial temperature rise and the stress and strain distribution of the transmission line under on-load state. A three-dimensional solid finite element model of reinforced aluminum conductor steel was established, and the temperature and stress distribution of the conductor were calculated. The effects of operating tension, wind speed, and radial temperature difference on the temperature and stress distribution were analyzed. The radial temperature difference increases about 1.40–3.16 °C with the rise of the mean temperature of the conductor. When the ambient temperature decreases from 20 to −40 °C, the mean temperature of the conductor decreases from 50.34 to −9.31 °C, and the external layer stress increases from 44.59 to 60.19 MPa. At the same time, the external layer stress of the conductor increases with the increase in wind speed and operating tension. The stress of the outermost aluminum conductor of the conductor under the radial temperature difference load increases with the rise in the temperature difference, and the stress of the inner aluminum conductor and the inner steel core decreases with the rise in the temperature difference.

Research on the optimized environment of large bridges based on multi-constraint coupling

To reduce the pollution emissions of bridges to the environment, researchers need to conduct more in-depth research and design the structure. Today's architectural, structural, and mechanical engineers pay more attention to funders' requirements and pursue the maximization of economic benefits. The research begins with establishing a theoretical model of the bridge's robustness under dead and dynamic loads: applying a Three-Dimensional (3D) solid finite element model, swarm intelligence optimization algorithm, and mathematical model of quadratic interpolation approximation solves the problems of multiple loads, discrete data, and convergence. Based on the establishment and analysis data of the research model, the research and analysis of the optimal topology bridge model are completed, and the optimal structure size is obtained. The carbon emissions from the bridge optimization decreased by 2242.92 t, accounting for 25% of the total emissions. This data is shocking, and it also gives investors and governments a painful reminder that they must pay more attention to the sustainable construction and development of the construction industry and achieve the goal of zero carbon emissions in the construction industry as soon as possible.

Seismic failure behavior of masonry domes under strong ground motions

General stability and failure behaviors of masonry domes under static loads have been investigated extensively in literature. However, a few studies have been done on the seismic failure behavior of masonry domes under strong ground shaking. This study aims to investigate the seismic failure behaviors and failure angles of masonry domes with support system including drum and buttresses using advanced 3D nonlinear numerical simulations. Four types of masonry domes with thickness-to-span ratios t/R = 0.092, such as a dome with circular drum (Dome A), a dome with circular drum and buttress (Dome B), a dome with dodecagon drum (Dome C), a dome with dodecagon drum and buttress (Dome D), built on historical structures are selected. Three-dimensional solid finite element models of the selected masonry domes are created using isotropic continuum macro modelling technique with homogenized properties. The finite element models are utilized to simulate the seismic behaviors of the masonry domes under three different strong ground motion acceleration records matched according to the target response spectrum with a return period of 475 years in the Turkish Building Earthquake Code. The seismic failure behaviors of four masonry dome models are evaluated by comparing mode shapes, displacements, maximum principal stresses, damage propagation patterns and failure angles. It is determined that the average angle intervals of hoop tension failure regions of Dome A, Dome B, Dome C and Dome D models under strong ground motions vary between 39, 25, 35 and 26 degrees, respectively.

Effect of coronal fracture angle on the stability of screw fixation in medial malleolar fractures: A finite element analysis.

Malleolar screw fixation is the most widely used treatment method for medial malleolar (MM) fractures. Here, although buttress plate fixation is advocated for vertical MM fractures, the angular discrimination between oblique and vertical MM fractures is still not fully understood. The purpose of this study is to test the adequacy of screw fixation in MM fractures with different angles and determination of a 'critical fracture angle' to guide surgeons in the decision-making for screw fixation for MM fractures by utilizing an advanced engineering simulation approach. In addition to loading of the healthy tibia structure, various cases of the MM fracture double screw fixation (14 simulation scenarios in total with fracture angles between 30° and 90°, in 5° increments) were considered in this research and their static loading conditions just after fixation operation were simulated through nonlinear (geometric and contact nonlinearity) finite element analysis (FEA). Patient-specific computed tomography scan data, parametric three-dimensional solid modelling and finite element method (FEM) based engineering codes were employed in order to simulate the fixation scenarios. Visual and numerical outputs for the deformation and stress distributions, separation and sliding behaviours of the MM fracture fragments of various screw fixations were clearly exhibited through FEA results. Minimum and maximum separation distances (gap) of 3.75 and 150.34 µm between fracture fragments at fracture angles of 30° and 90° were calculated respectively against minimum and maximum sliding distances of 25.87 and 41.37 µm between fracture fragments at fracture angles of 90° and 35°, respectively. The FEA results revealed that while the separation distance was increasing, the sliding distance was decreasing and there were no distinct differences in sliding distances in the scenarios from fracture angles of 30°-90°. The limitations and errors in a FEA study are inevitable, however, it was interpreted that the FEA scenarios were setup in this study by utilizing acceptable assumptions providing logical outputs under pre-defined boundary conditions. Finally, the fracture healing threshold for separation and/or sliding distance between fracture fragments was assigned as 100 µm by referring to previous literature and it was concluded that the screws fixed perpendicular to the fracture in a MM fracture with more than 70° angle with the tibial plafond results in a significant articular separation (>100 µm) during single-leg stand. Below this critical angle of 70°, two screws provide sufficient fixation.

GEOMETRICALLY NONLINEAR DEFORMATION AND BUCKLING OF SMOOTH AND FACETED SHELLS

Practical using of curvilinear shape shells is related with significant problems during their production especially for metal structures. Therefore during such shells production curvilinear shape is replaced by faceted. Realization of this method when designing needs additional investigations performing of faceted shells bearing capacity on the basis of appropriate numerical calculation method using. Problems of solving such tasks are practically not displayed in the literature. Break-in of the middle surface affect significantly to the shell stress-strain state. Accounting of temperature fields’ influence in the problems of their stability complicates their behavior research even more. In this paper the research results comparing analysis of static problems about smooth and faceted shells nonlinear deformation and stability under mechanical loads is presented. The problem is solving with using of software that are based on the finite element method: by method that realized the moment finite-element scheme and using software package LIRA. The solving method that used the moment finite-element scheme is based on the geometrically nonlinear equations of the 3D theory of thermoelasticity without application of theory of shells simplifying hypothesis and on the applications of the universal three-dimensional solid finite element.

Impact of engineering/technology factors and transient loads on the stress - strain state of a three-layer cylindrical shell

An issue of a stress-strain state of a three-layer cylindrical shell under variable loads has been considered. Assessment results of a three-layer cylindrical shell stress-strain state with regard to the physical and mechanical characteristics of an aggregate polymer filler and its reinforcement intensity by means of the stiffening rings rigidly connected to the shell coating are presented in the article. Calculations have been performed using the software Nastran. Values of displacements and stresses have been calculated by applying the direct transient dynamic process algorithm. The time interval was 0.0000025 sec, and the total number of steps was 200. Choice of the three-dimensional finite element type was conditioned by the need of acquiring more detailed and accurate calculation results. The finite element model included 8000 three-dimensional solid finite elements and 9360 nodes. Impact of the physical and mechanical characteristics’ parameters of integral polymeric filler through the stiffening rings on the shell’s stress-strain state under the axisymmetric inner impulse load has been investigated. Numerous results concerning dynamics of the three-layer structure, which have been obtained by the finite elements method, allow distinguishing the stress-strain state of a three-layered cylinder-type elastic structure at any moment within an analyzed time interval. Optimization of the shell design is recommended. Intensity of the polymeric filler reinforcement impacts considerably the stress-strain state of the shell, as well as its performance characteristics. Increasing the intensity of the shell’s polymeric layer reinforcement decreases considerably the deformation of the shell’s bearing layers. Comparison of the obtained results to the impact of other factors indicates the credibility of the approach used and that the unbiased information was received.

Subway Embedded Track Geometric Irregularity Safety Limits

A coupling dynamic model of a subway train and an embedded track is established to study the safety limits of track irregularities. The simulated vehicle system was a 74-degrees of freedom multi-rigid body model, and the rail was a Timoshenko beam. The slab was a three-dimensional solid finite element model. The sensitive wavelength irregularity was first studied, and then the safety limit of the sensitive wavelength was analyzed. The wheel-rail lateral force exhibited a substantial effect on the track alignment and gauge irregularity safety limit. The wheel-rail vertical force and the rate of wheel load reduction significantly affected the height and cross-level irregularity safety limit. The results demonstrate that the safety limits of the alignment, gauge, height, and cross-level embedded track geometric irregularity are 5.3 mm, [− 10.5, 8] mm, 5.6 mm, and 6 mm, respectively.

Numerical modelling of reinforced concrete frames with masonry infills and rubber joints

Masonry infill walls are critical components of reinforced concrete (RC) frames, which may be damaged even under earthquake events of moderate intensity, thus resulting in significant losses. Recent experimental and numerical studies have investigated innovative solutions for protecting these walls by reducing their interaction with the RC frame. Among these, specially shaped rubber joints were developed that can be inserted between the brick units, and between the masonry wall and the frame.In the present study, a novel computational modelling strategy is developed using ABAQUS to investigate the in-plane behaviour of RC frames with infill walls and rubber joints. The proposed approach employs three-dimensional solid finite elements to simulate the concrete components, 3D beam elements for the reinforcing bars, and a mesoscale approach for the infill wall with rubber joint. The numerical strategy is validated against two past experimental studies whose results can be found in the literature, one on RC frames with traditional infill walls, the other on RC frames with traditional walls and walls with rubber joints. The results shed light on the effectiveness of the rubber in minimising the in-plane seismic damage to the bricks, by localizing the deformation mostly in the rubber joints, and reducing the overall stiffness of the infilled system. Further analyses are carried out to investigate the effect of the rubber joints’ layout and stiffness on the behaviour and capacity of the system and its components.

A multi-director continuum beam finite element for efficient analysis of multi-layer strand cables

This study presents a multi-director continuum beam finite element developed for efficient analysis of multi-layer strand cables. The beam element is derived from the continuum mechanics based beam formulation incorporating multi-directors and cross-sectional elements to describe the helical geometries of wires that constitute the strand cables. The main advantage of the present continuum beam formulation is that complex geometries of strand cable and inter-wire motions can be addressed in the framework of the beam kinematics regardless of the numbers of layers and subordinate helical wires. This approach enables simple modeling together with efficient analysis, and allows both geometric and material nonlinearities to be considered. In addition to its excellent accuracy, the proposed beam element model requires a significantly reduced number of degrees of freedom compared to conventional three-dimensional solid finite element models for cable analysis. Through several numerical examples, the predictive ability of the proposed beam model is demonstrated.

Hysteretic behavior of CFST column-steel beam bolted joints with external reinforcing diaphragm

In this study, three concrete-filled steel tubular (CFST) column-steel beam bolted joints with external reinforcing diaphragm were tested under cyclic loading using 1/2 scaled specimens, and the influence law of steel beam size and tie plate of high-strength bolts on the failure modes were discussed. The ABAQUS program was used to establish the three-dimensional solid finite element models of the joints, and the joint models were then verified by the test data. Taking the welded rigid joint with external reinforcing diaphragm as the benchmark, a connection detailing of bolted rigid joint and a method for classifying the joint were proposed. The stiffness, bearing capacity and plastic energy dissipation of the bolted joints with different structural detailing and reinforcing measures were compared and analyzed. The obtained results show that the bolted joints with external reinforcing diaphragm can be classified as semi-rigid joint. The stiffness and bearing capacity of the bolted joint can almost be equivalent with the welded rigid joint counterparts, when the external reinforcing diaphragm with stiffeners was connected to the steel beam using four rows of bolts and simultaneously setting web stiffeners at the beam ends. With the above configuration, the total plastic energy dissipation of the bolted joint is over 80% of that of the welded rigid joint counterpart, and the steel beam is found to be the main component contributing the plastic energy dissipation.

Optimisation of energy harvesting for stiffened composite shells with application to the aircraft wing at structural flight frequency

The conversion of structural dynamic strain into electric power using piezoelectric transducers to power microelectronic devices and wireless sensor nodes for structure health monitoring has been receiving growing attention from academic researchers and industry. Harvesting electric energy from vibration and storing it in an external infinite life-span capacitor is a proposed technique to eliminate the drawbacks of using conventional finite life-span batteries. Optimisation of the harvested power is an important research topic to ensure an endless power source with sufficient flow of electricity.This paper concerns optimisation of energy harvesting for composite shells stiffened by beams, with discrete flexible composite piezoelectric sensors bonded to the surface and located optimally. A homogenous composite shell stiffened by beams with a bonded piezoelectric transducer connected to an external resistive load is modelled using three-dimensional solid finite elements. An efficient and effective placement methodology is proposed to find the optimal locations of piezoelectric sensors based on the maximisation of average percentage sensor effectiveness as an objective function. This study is firstly verified against published work for a cantilever flat plate and beam, and then implemented to optimise the energy harvesting for a composite aircraft wing at structural frequencies during flight. The results show a high reduction in computational effort and improved effectiveness of the methodology to optimise energy harvesting for complex and large-scale structures compared with alternative methods. Furthermore, the harvesting power obtained from optimal sensor distribution shows promise to be sufficient to activate wireless sensor nodes for health monitoring.

A non-linear cubic spline layerwise time domain spectral finite element for the analysis of impacts on sandwich structures

The present work addresses the non-linear impact dynamic response of sandwich composite plates with Hertzian contact interaction between the impactor and the plate. Initially, a well-established Cubic Spline Layerwise Theory is employed for the precise description of complex through the thickness kinematics of sandwich composite plates. Furthermore, the expressions of Green Lagrange non-linear strain terms, along with the Deshpande-Fleck flow rule for polymeric crushable foams are presented for non-linear explicit impact dynamics. The material and geometric non-linearities as well as the layerwise mechanics, are integrated into a Time Domain Spectral Element which possesses the attributes of high-order Lagrangian polynomial shape functions and node collocation with the integration points due to the Gauss-Legendre-Lobbato integration scheme. The aforementioned numerical package provides a fast and accurate non-linear explicit integration dynamic module for the prediction of the impact response of sandwich plates, demonstrating the universality and validity of using Hertzian contact in sandwich and laminated composite structures. The proposed novel non-linear numerical model is correlated with experimental results and also with a high-fidelity three-dimensional solid finite element model in terms of accuracy and computationally efficiency.

A numerical study of a self-centring SMA damper

Many SMA-based dampers were presented and they can show both energy dissipating capability and self-centring property. This paper aims to a self-centring damper composed by two groups of pre-tensioned SMA wires and two precompressed springs. The three-dimensional solid finite element models of the damper are constructed at ANSYS Workbench environment, and the Auricchio's model is used to simulate the superelastic behaviour of the SMA wires. To simulate the damper assembly process, the models of two springs are compressed and certain pre-tensions are imposed to the SMA wires. The initial stresses for the core components are figured out and imposed to the un-deformed damper. Then, the cyclic loads are imposed to the damper models and the mechanical behaviour of the damper is simulated. The numerical simulation results are compared with the theoretical analysis results based on the Brinson model of the SMA material. For a 1 m long damper with a 5 mm stroke in the case study, both the numerical and theoretical results show that a 35 kN reaction force is offered by the damper. The force-displacement curves of the damper model are flag-shaped, indicating the moderated energy dissipating capacity and full self-centring capability of the damper.

Analysis of temperature-induced deformation and stress distribution of long-span concrete truss combination arch bridge based on bridge health monitoring data and finite element simulation

Through decades of operation, deformation fluctuation becomes a central problem affecting the normal operating of concrete truss combination arch bridge. In order to clarify the mechanism of temperature-induced deformation and its impact on structural stress distribution, this article reports on the temperature distribution and its effect on the deformation of concrete truss combination arch bridge based on bridge health monitoring on a proto bridge with 138 m main span. The temperature distribution and deformation characteristics of the bridge structure in deep valley area are studied. Both of the daily and yearly temperature variation and structural deformation are studied based on bridge health monitoring. Using the outcome of monitoring data, three-dimensional solid finite element models are established to analyze the mechanism of temperature-induced deformation of the whole bridge under different temperature fields. The influence of temperature-induced effect is discussed on local damage based on the damage observation of the background bridge. The outcome of comparisons with field observation validates the analysis results. The relevant monitoring and simulation result can be referenced for the design and evaluation of similar bridges.