Load Position Research Articles

Mechanical responses of bell‐and‐spigot joints in buried prestressed concrete cylinder pipe under coupled service and surcharge loads

AbstractPrestressed concrete cylinder pipe (PCCP) is widely used in hydraulic engineering. The bell‐and‐spigot joint is a weak point along a PCCP pipeline, since damage of joint can affect the operation of the whole pipeline. In this paper, a three‐dimensional numerical model of buried PCCP, considering the simulation of rubber gasket in bell‐and‐spigot joint is established. The fluid–structure coupling of PCCP is accomplished using the Mesh‐based parallel Code Coupling Interface (MpCCI), where the pipe and the surrounding soil are characterized in the software ABAQUS, and the pressurized water is modeled in the software FLUENT. The force and rotation angle at joints of PCCP under different conditions, including surcharge load, loading location, cover depth, and internal pressure, are analyzed. It is shown that the rotation angle of joint exceeds the allowable value, when the surcharge load is greater than 180 kPa. Compared with the effect of surcharge load, the offset distance (i.e., distance between the loading position and the pipe axis) has a greater influence on the development of horizontal displacement and rotation angle. As the offset distance increases, both the horizontal displacement and rotation angle at joints increase first, and they decrease after the peak.

Dorsal Bone–Ligament–Bone Reconstruction of Chronic Lunotriquetral Instability: Biomechanical Testing

PurposeLunotriquetral (LT) instability is uncommon and few biomechanical analyses of the condition exist. For chronic LT instabilities, arthrodesis has long been the treatment of choice but has a high risk for nonunion. The aim of this study was to evaluate an alternative treatment option using a bone–ligament–bone graft in a cadaver model and compare it with a conventional arthrodesis.MethodsWe used 10 cadaveric forearms with different loading positions. We employed computed tomography scans to evaluate the LT joint. Scans were performed with the joint intact after we sectioned the dorsal LT ligament and the palmar LT ligament. The joints were then reconstructed using a bone–ligament–bone graft from the capitate–hamate joint as well as with a compression screw simulating arthrodesis. The joints were then rescanned and 3-dimensional analysis was performed using specialized 3-dimensional software.ResultsSectioning the dorsal part of LT ligament had little effect on kinematics; however, additional division of the palmar LT ligament resulted in increased mobility. Restoration of physiological kinematics could be partially achieved after bone–ligament–bone reconstruction. Arthrodesis showed increased intercarpal motion in the adjacent scapholunate and lunocapitate joints compared with the bone–ligament–bone reconstruction.ConclusionsThe bone–ligament–bone reconstruction displayed physiologic carpal kinematics in the adjacent joints compared with arthrodesis. It provided enough stability but still some mobility in the LT joint to be able to use it as a treatment modality for chronic LT instability without the risk for nonunion. Decreased intercarpal motion was not statistically significant although there appeared to be a trend toward it.Type of study/level of evidenceTherapeutic IV.

Effect of angular misalignment of inner ring on the contact characteristics and stiffness coefficients of duplex angular contact ball bearings

Ring misalignment is unavoidable in most applications of bearing and significantly affects bearing performance. However, it has not been thoroughly studied for duplex angular contact ball bearings. To overcome the deficiency, this paper presents the analysis for duplex angular contact ball bearings by considering inner ring angular misalignment. A highly modular five degree-of-freedom model of duplex angular contact ball bearings is proposed based on vector-and-matrix method for back-to-back, face-to-face and tandem configurations. Five-dimensional stiffness matrix of bearing is also presented. On the basis, influences of ring misalignment on load distribution, maximum and average contact loads of bearing with back-to-back and face-to-face configurations are analyzed. Finally, translation and tilting stiffness coefficients of bearing are further discussed under misalignment condition. The results show that, ring misalignment considerable changes the contact characteristic of ball-raceway and causes uneven load distribution. Ring misalignment affects the position of maximum contact load and significantly impacts the diagonal stiffness of bearing. Contact characteristics and stiffness are also dependent on the bearing configuration. The results suggest the importance of bearing alignment and demonstrate the necessity of misalignment effect analysis.

Dynamic Response of Rigid Pavement Plate due to Localized Blast Load

In structural and transportation engineering applications, the dynamic response of orthotropic plates is an essential matter. Engineers did not consider the effects of dynamic loads such as those from machine vibrations or blast load. Dynamic analysis of rigid pavement plates due to local blast loads on concrete slabs in this research is modeled as concrete slabs with boundary condition that every edges of plates have a dowel-tie bar support and The rigid concrete pavement sitting on elastics Pasternak foundation is modeled by using the Kirchhoff theory of thin plates. Pasternak foundation have elastic vertical spring support and continuous shear layer. The main system responses that are observed are the transversal deflections at midspan and the internal stresses of the plate, particularly the maximum principle stress, minimum principle stress and maximum shear stress. Three loading phases are included in the analysis, namely: the positive phase, the negative phase, and the free vibration phase. Analyses are carried out utilizing a numeric approach termed the Modified Bolotin Method with two trancedental equation. The analysis is performed when the load is above the plate (0 ≤ t ≤ t0). Deflections resulting from various load positions on the set of slab models throughout all three phases are then compared side-by-side. Bending moment, shear forces, and stresses are calculated on all slab models with the Friedlander localized blast loading applied at midspan and the results are presented as stress contours that are then compared between each model.

Emerging Challenges for Numerical Simulations of Quasi-Static Collision Experiments on Laser-Welded Thin-Walled Steel Structures

This paper re-evaluates recently published quasi-static tests on laser-welded thin-walled steel structures in order to discuss the fundamental challenges in collision simulations based on finite element analysis. Clamped square panels were considered, with spherical indenter positioned at the mid-span of the stiffeners and moved along this centerline in order to change the load-carrying mechanism of the panels. Furthermore, the use of panels with single-sided flat bar stiffening and web-core sandwich panels enabled the investigation of the effect of structural topology on structural behavior and strength. The changes in loading position and panel topology resulted in different loading, structural and material gradients. In web-core panels, these three gradients occur at the same locations making the panel global responses sensitive for statistical variations and the failure process time-dependent. In stiffened panel with reduced structural gradient, this sensitivity and time-dependency in failure process is not observed. These observations set challenges to numerical simulations due to spatial and temporal discretization as well as the observed microrotation, which is beyond the currently used assumptions of classical continuum mechanics. Therefore, finally, we discuss the potential of non-classical continuum mechanics as remedy to deal with these phenomena and provide a base for necessary development for future.

Robust concurrent topology optimization of multiscale structure under load position uncertainty

Concurrent topology optimization of macrostructure and microstructure has attracted significant interest due to its high structural performance. However, most of the existing works are carried out under deterministic conditions, the obtained design may be vulnerable or even cause catastrophic failure when the load position exists uncertainty. Therefore, it is necessary to take load position uncertainty into consideration in structural design. This paper presents a computational method for robust concurrent topology optimization with consideration of load position uncertainty. The weighted sum of the mean and standard deviation of the structural compliance is defined as the objective function with constraints are imposed to both macro- and micro-scale structure volume fractions. The Bivariate Dimension Reduction method and Gauss-type quadrature (BDRGQ) are used to quantify and propagate load uncertainty to calculate the objective function. The effective properties of microstructure are evaluated by the numerical homogenization method. To release the computation burden, the decoupled sensitivity analysis method is proposed for microscale design variables. The bi-directional evolutionary structural optimization (BESO) method is used to obtain the black-and-white designs. Several 2D and 3D examples are presented to validate the effectiveness of the proposed robust concurrent topology optimization method.

The effects of rib shape and slit on fatigue properties of orthotropic steel decks

Orthotropic steel decks are composed of comparatively thin steel plates (as thin as 6 mm) that deform in the in-plane and out-of-plane directions at longitudinal-to-transverse rib connections in response to vehicle loads. Since such deformations can change as the load positions move, local stress directions can also vary such that hot spots along the weld toes are moved and the relationship between the load position and hot spot stress becomes complex. Furthermore, the deformations will differ depending on the specific type of connection. The present work investigated the effects of rib shapes and slits (that is, cut-outs) on the fatigue properties of such connections by calculating structural hot spot stresses at various connections by finite element analyses. The hot spot locations along weld toes were determined to vary depending on the load position, the longitudinal rib shape, and the presence of slits. It was also found that the load positions associated with maximum and minimum hot spot stresses at slit connections tended to be eccentric relative to the center axes of the evaluated ribs.

DYNAMIC ANALYSIS OF COMPOSITE MULTI I-GIRDERS BRIDGE USING FINITE ELEMENT METHOD

Three dimensional finite element models are developed to deal with the bridge-vehicle interaction problem of simply supported composite multi I-girders bridge. The bridge is modeled by using ANSYS 15.0 program with solid and shell elements to represent concrete and steel members, respectively. AASHTO HL-93 truck is idealized as 3D non-linear model consisting of five lumped masses connected by rigid beams and supported by spring-dampers. The separation between the tires and road surface and surface roughness condition are simulated by Gap and actuator elements, respectively. The road surface roughness profiles are generated from power spectral density (PSD) and cross spectral functions. The models used are capable to take all bridge and vehicle responses into consideration with no limitations on the complexity of the models. The dynamic responses of the multi I-girder bridge are investigated under conditions of various loading positions, roughness classes, vehicle speeds, and bump height. The dynamic behaviors are presented in terms of Dynamic Amplification Factors (DAF). The results show the girder that itself supporting the moving vehicle has lower value of DAF because of higher static responses. A 45 km/hr vehicle speed provides higher DAF value. The bump heights have significant effect on DAFs for bridge with short span.

Theoretical and Finite Element Analysis of Steel Corbel Columns under Eccentric Compression

In order to study the stress characteristics of steel corbel column under eccentric pressure, the corbel column is regarded as a cantilever column for theoretical analysis based on engineering mechanics, and the analytical solution of structural stress of corbel column is obtained. The three-dimensional finite element models of three kinds of corbels are established by using ABAQUS software. The static analysis under eccentric load is carried out, and the stress distribution of corbel columns is obtained. The results show that changing the loading position will have a great impact on the stress state of the structure, and finding out the reasonable loading position can make the component better exert its mechanical performance. Finally, the reasonable loading position and structural measures of the single corbel column in this project are proposed, which can provide reference for similar projects.

Design and deflection evaluation of a portal crane subjected to traction load

Abstract In this study, deflection values occurring on the main girder of a portal crane at various payloads were investigated theoretically, numerically and experimentally. The entire portal crane structure was analyzed on via a computer model in order to assess the reliability of the main girder in terms of deflection. Variations in deflection on the main girder were determined in accordance with load lifted and the crane trolley position. In addition, deflection values at critical points on the main girder of the portal crane were measured experimentally. Results indicate that maximum deflection value occurring on the main girder when the crane trolley was located at the middle of main girder were 1.34 times greater than the deflection value when the crane trolley was located at loading position 3.

Design and deflection evaluation of a portal crane subjected to traction load

Abstract In this study, deflection values occurring on the main girder of a portal crane at various payloads were investigated theoretically, numerically and experimentally. The entire portal crane structure was analyzed on via a computer model in order to assess the reliability of the main girder in terms of deflection. Variations in deflection on the main girder were determined in accordance with load lifted and the crane trolley position. In addition, deflection values at critical points on the main girder of the portal crane were measured experimentally. Results indicate that maximum deflection value occurring on the main girder when the crane trolley was located at the middle of main girder were 1.34 times greater than the deflection value when the crane trolley was located at loading position 3.

The Influence of Loading Position in A Priori High Stress Detection using Mode Superposition

For the analysis of structural components, the finite element method (FEM) has become the most widely applied tool for numerical stress- and subsequent durability analyses. In industrial application advanced FE-models result in high numbers of degrees of freedom, making dynamic analyses time-consuming and expensive. As detailed finite element models are necessary for accurate stress results, the resulting data and connected numerical effort from dynamic stress analysis can be high. For the reduction of that effort, sophisticated methods have been developed to limit numerical calculations and processing of data to only small fractions of the global model. Therefore, detailed knowledge of the position of a component’s highly stressed areas is of great advantage for any present or subsequent analysis steps. In this paper an efficient method for the a priori detection of highly stressed areas of force-excited components is presented, based on modal stress superposition. As the component’s dynamic response and corresponding stress is always a function of its excitation, special attention is paid to the influence of the loading position. Based on the frequency domain solution of the modally decoupled equations of motion, a coefficient for a priori weighted superposition of modal von Mises stress fields is developed and validated on a simply supported cantilever beam structure with variable loading positions. The proposed approach is then applied to a simplified industrial model of a twist beam rear axle.

Effect of position of partial load on buckling and vibration characteristics of composite panels with circular cutouts

Abstract In this, the effect of different positions of partial ledge loads on buckling behavior of laminated panels with the centrally placed circular cutout is studied by developing finite element formulation using 9 - noded heterosis element. The formulation includes the effect of shear deformation and rotary inertia. The effect of various parameter such as cutout size, ply-orientation and thickness of the panel included in this work to study the buckling behavior of each parameter in detail. It is observed that the buckling resistance of the panel decreases with the increase in cutouts size irrespective of position of partial load. However, the position of partial load at extreme ends show higher buckling resistance as compared to that of centrally placed edge loads, irrespective of cutout size. Further, cross-ply symmetric laminates show extremely higher and least buckling resistance, when partial load acting at the extreme edges and at the center of the partial edges respectively, as compared to all other layup schemes.

Influence of rigidity of retainers on dynamic behavior of implant-supported removable partial dentures

BackgroundImplant-supported removable partial dentures (ISRPDs) are an effective treatment for partially edentulous patients. ISRPDs improve patients’ satisfaction and oral function to a greater extent than RPDs by improving denture stability and enhancing support. However, the effect of a type of direct retainer on displacement of the abutment teeth and dentures in ISRPDs remains unclear. Therefore, we made a resin mandibular model of unilateral mandibular distal-extension partial edentulism for mechanical simulation and compared the dynamic behavior of the abutment teeth and the denture base among different tooth-borne retainers with various rigidities for RPDs and ISRPDs.MethodsA resin mandibular model for mechanical simulation that had unilateral mandibular distal-extension edentulism and was missing the first molar, second molar, first premolar, and second premolar, and a denture fabricated from the patient’s computed tomography images were used. Three types of direct retainers with different connecting rigidities were evaluated. The vertical displacement of the denture base and buccal and lingual sides and the mesial displacement of the abutment teeth were measured.ResultsRegardless of the rigidity of the direct retainers and loading positions, the displacement of the denture bases in the ISRPDs was significantly smaller than that in the RPDs (P < 0.001). There was no significant difference in vertical displacement of the denture bases among direct retainers with various connecting rigidities in the ISRPDs. Conversely, horizontal displacement of the abutment teeth in both the RPDs and ISRPDs tended to be larger with the cone crown telescope, which has high rigidity, than with the cast cingulum rest and wire clasp, which have much lower rigidities.ConclusionOur results suggested that cast cingulum rest and wire clasps as direct retainers are appropriate ISRPDs to minimize denture movement and suppress displacement of the remaining teeth in patients with unilateral mandibular distal-extension partial edentulism.

Identification of Axial and Radial Impacts for Pneumatic Artificial Muscles in Static and Dynamic Processes Based on Autocorrelations of Differential Pressure Signals

Since the pneumatic artificial muscle is usually employed to actuate the robot, it is inevitable that it will collide with obstacles and/or other objects such that there will be impacts. The typical impacts include the axial and radial ones. This paper detects these two kinds of impact by a designed differential pressure measurement system, and achieves the goal of identifying them by the autocorrelations of their differential pressure signals in both static and dynamic processes, which are the two main work processes of the pneumatic artificial muscle. In detail, first we design an experiment scheme by connecting the pneumatic artificial muscle to the differential pressure sensor through two pressure tubes; then the axial and radial impact signals are acquired via the impact experiments under different work conditions (impact strength, internal pressure, load, and impact position); finally, the identification of the axial and radial impact signals are achieved based on the autocorrelation technique with a well-selected threshold. The experiments illustrate the effectiveness of the whole method.

Effect of Moisture and Axes Orientation on the Mechanical Properties of the Myrobalan Fruits and its Seed Under Compressive Loading

The main objective of inducted research was to test mechanical properties of two myrobalan fruits Terminalia bellerica and Terminalia chebula based on variation in the moisture content and the loading position of the fruit and its seed along the longitudinal, intermediate and transverse axes. The mechanical properties were tested in terms of deformation, rupture force, toughness and energy absorbed. The results revealed that the forces required to deform the Terminalia chebula whole fruit (163.09 N) and seed (890.53 N) were minimum along the transverse axis, while for the Terminalia bellerica it was found to be minimum along longitudinal axis for both whole fruit (725.25 N) and seed (554.84 N) at 4% (wet basis) moisture content. The increase in the moisture content of the fruit and seed showed an increase in the deformation as elasticity increased, while the toughness of the fruit decreased from 0.90 to 0.13 mJ/cm3. The obtained results find its application in the designing of various unit operation equipments such as decorticator and graders.

On Predicting the Ultimate Capacity of a Large-Span Soil\u2013Steel Composite Bridge

The limit state design of large-span soil–steel composite bridges (SSCB) entails that understanding their structural behaviour in the ultimate state is as much needed as their performance under service conditions. Apart from box culverts, the largest loading-to-failure test was done on a 6.3-m span culvert. More tests on larger spans are believed essentially valuable for the development of the design methods. This paper presents the numerical simulation efforts of an 18.1-m span SSCB pertaining to its ongoing preparations for a full-scale field test. The effect of the different loading positions on the ultimate capacity is investigated. Comparisons are made between three-dimensional (3D) and two-dimensional (2D) models. The results enabled to realise the important role of the soil load effects on the ultimate capacity. It is found that the failure load is reduced when the structure is loaded in an asymmetrical manner. A local effect is more pronounced for the live load when the tandem load is placed closer to the crown. The study also illustrates the complex correlation between 3D and 2D models, especially if one attempts to simultaneously associate sectional forces and displacements.

Electromechanical Response and Residual Thermal Stress of Metal-Core Piezoelectric Fiber /Al Matrix Composites.

It is well known that the curing residual stress induced during a fabrication process has a great influence on the performance of piezoelectric composite devices. The purpose of this work was to evaluate the residual thermal stress of lead zirconate titanate piezoelectric fiber aluminum (Al) matrix (piezoelectric fiber/Al) composites generated during fabrication numerically and experimentally and to understand the effect of the residual thermal stress on the electromechanical response. The three-dimensional finite element method was employed, and the residual stress generated during the solidification process of the Al matrix was calculated. The output voltage was also calculated in the analysis when putting stresses on the composite materials in the length direction of the piezoelectric fiber. It was shown that the cooling from higher temperatures increases the electromechanical conversion capability. Furthermore, we also performed the simulation, and we recorded the output voltage under concentrated load to investigate its application as a load position detection sensor, and we also discussed the influence of the position by changing the modeling with a different fiber position in the Al. The residual stress of hot press molded piezoelectric fiber/Al composite was then measured, and the comparison was made with the calculated values. The simulation results revealed that our model predictions reproduced and explained the experimental observations of curing residual stress. After this study, similar models of composite materials can be analyzed by this simulation, and the result can be used to design piezoelectric composite materials.

Study of experiment in field for long-span cable-stayed bridge

In order to provide the reasonable optimization measures for the construction of long-span steel bridge deck pavement in the alpine area, the actual pavement effect under the real load is studied by simulation simulation with the finite element analysis software relying on the construction of the bridge deck of No.1 Bridge of Haidong Avenue, Ledu District, Haidong city. Through different load positions and loading methods, the control load loading points are determined, and the parameterized analysis is carried out for the elastic modulus, thickness and temperature difference of the pavement, and finally the structural parameters of the pavement suitable for the bridge are obtained; the experimental analysis results show that the theoretical calculation idea adopted is feasible, and the measured value is within the expected range. It can be seen that the construction optimization measures and suggestions are of great significance to the construction of steel bridge deck pavement in the high cold area.

Application of ultrasound elastography in the evaluation of muscle strength in a healthy population.

To investigate the validity of shear wave elastography (SWE) for the evaluation of muscle strength compared with isokinetic muscle testing, and to assess the influence of demographic factors such as height, weight, and body mass index (BMI) on the shear wave velocity (SWV). Sixty healthy volunteers were consecutively enrolled. SWE was used to measure the SWV of the right quadriceps femoris in a relaxed position, in a tensive position, and under loads of 1 and 2 kg. Muscle strength parameters including peak torque (PT), PT to body weight ratio (PT/BW), and total work (TW) were evaluated using isokinetic muscle testing. The SWV of the rectus femoris in different positions were compared using the Friedman test and the Kruskal-Wallis test, and the SWV and muscle strength parameters were compared between different genders and age groups using the Mann-Whitney U test. Additionally, Spearman's correlation coefficient was used to evaluate the correlation between SWV and muscle strength, as well as the possible effects of height, weight, and BMI on SWV. As the load increased, the SWV of the rectus femoris increased (P<0.001). In the relaxed position, there was no significant correlation between the SWV and the results of isokinetic muscle testing. With increasing load, the SWV and the results of isokinetic muscle testing were not significantly correlated (r=-0.256--0.392, P<0.05). In the 1 kg load position, height and weight were not significantly correlated with SWV (r=-0.261--0.393, P<0.05). In the relaxed position, there were no significant differences in the maximum, minimum, or mean SWV of the rectus femoris between different genders and age groups (P>0.05). However, under a 1 kg load, the maximum, minimum, and mean SWV of the females in this study were significantly higher than those of the males (4.49±0.60 vs. 3.98±0.68 m/s; 2.55±0.61 vs. 2.20±0.63 m/s; and 3.51±0.60 vs. 3.06±0.58 m/s; P=0.003, 0.028, and 0.004, respectively). Furthermore, there were significant differences in the maximum and mean velocities between the groups aged 20-34 and 35-60 years (4.11±0.62 vs. 4.47±0.70 m/s; 3.17±0.53 vs. 3.52±0.69 m/s; P=0.045 and 0.044, respectively). Ultrasound elastography (UE) shows potential for the measurement of muscle strength. The SWV of muscles demonstrate an increasing trend with the increase of impedance. Additionally, age and gender have a significant effect on SWV, while the effects of height, weight, and BMI require further investigation.