Axial Load Distribution Research Articles

Residual compressive behaviour and CFRP strengthening of SRCFST columns after combined damage of fire and lateral impact

Composite structure may be subjected to impact and fire during its service life, and the damaged member face challenges in the performance evaluation and strengthening. This study conducted an experimental and numerical investigation into the residual compressive behaviour of steel-reinforced concrete-filled steel tubular (SRCFST) columns after combined damage of fire and lateral impact. Thirteen damaged specimens under axial loading were tested, with three specimens strengthened with carbon fiber reinforced polymer (CFRP). The failure modes of specimens, residual compressive capacity, deflection distribution, and strain development were discussed. The finite element analysis model on the residual compressive behaviour of damaged SRCFST columns was then developed and calibrated. The full-range analysis on the residual performance of damaged columns was carried out, included the temperature development, distribution of axial load and bending moment, degradation mechanism of bearing capacity, stress development, and effects of fire exposure time. The parameter study was finally conducted to investigate the effects of various factors on the residual compressive performance of damaged SRCFST columns. The results indicated that increasing the fire exposure time and impact height reduces visibly the residual compressive capacity of damaged specimens. As the two damages accumulate, the axial load of each component gradually reduces, while the axial compressive capacity proportion redistributes.

Analyzing Operational Dynamics: Centralized Load Distribution and Suspended Wagons in Self‐Propelled Trains

ABSTRACTThis paper primarily focuses on the distribution of axial loads in railway networks. The analysis assesses the advantages and disadvantages of articulated trains. In addition, the perspectives and proposed solutions of academicians are analyzed. Simpack accurately models all aspects of this articulated train model. Subsequently, the program emulates the control system of the train. This study demonstrates a control system that utilizes a hydraulic actuator. The proposed model and control system actuator's dynamic response are evaluated according to EN14363 and UIC518 standards to validate the functionality of the component. The stability of a railway train, particularly when making turns, relies on the proper allocation of weight on the wheels and axles. This research investigates the hazards associated with the uneven distribution of loads in train wagons, particularly when navigating curving tracks. A train designed for intercity travel was constructed utilizing a specific control system. The discrepancy in axle load is mitigated by implementing a straightforward control method. The train's carriage, which is suspended without bogies, resulted in fluctuating axle load. A disparity in axle load was established by an actuator positioned between the wagons. The control mechanism minimized load disparity and regulated axle load.

Insights from the numerical analysis of axially loaded piles in liquefiable soils

Axially loaded piles in liquefiable soils can undergo severe settlement due to an earthquake event. During shaking, the settlement is caused by the decreased shaft and tip capacity from excess pore pressures (ue) generated around the pile. Post shaking, soil settlement from the reconsolidation of liquefied soil surrounding the pile results in the development of additional load (known as drag load), causing downdrag settlement of the pile. Estimating the axial load distribution and pile settlement is essential for designing and evaluating the performance of axially loaded piles in liquefiable soils. In practice, a simplified neutral plane solution method is used, where the liquefied soils are modeled as a consolidating layer without considering the effect of ue generation/dissipation. A TzQzLiq analysis models the load and settlement response of axially loaded piles in liquefiable soils by accounting for the effect of excess pore pressure (ue) generation/dissipation on the shaft and tip capacity. This paper presents the deficiencies of the simplified neutral plane method in predicting the drag load as well as the downdrag settlement by comparing it with the TzQzLiq analysis validated with hypergravity model tests. The results show that the drag load and the downdrag settlement predicted by the neutral plane method might be over- or under-estimated depending on the pile load, the rate of ue dissipation, and the soil settlement. For the cases studied, it was found that most of the pile settlement occurs during shaking due to the decrease in the pile's tip resistance from the development of ue in the soil surrounding it. While large drag loads develop during reconsolidation, the resulting downdrag settlement is small. While the neutral plane method generally predicted a downdrag settlement comparable to that of the TzQzLiq analysis, it overpredicted drag load and could not predict co-seismic settlement. Finally, the study advocates for the development and use of a displacement-based procedure (accounting for all the mechanisms occurring during and after an earthquake event) such as based on TzQzLiq analysis in accurately evaluating the performance of the pile (i.e., the pile settlement and the maximum load), thus providing an overall safe, efficient, and optimized design.

Nonlinear finite element analysis for axial load distribution of thread considering plastic deformation

Nonlinear finite element analysis for axial load distribution of thread considering plastic deformation

Load-carrying capacity of hole threads in TOBs bolted curved T-stubs to circular steel tube connections

This study investigates the load-carrying mechanism and proposes precise strength prediction methods for hole threads in Thread-fixed One-side Bolts bolted curved T-stubs to circular steel tube connections. A series of parametric analysis was performed with an advanced 3D finite element model considering critical parameters including tube wall thickness, bolt angle and bolt size. The axial load distribution along the hole threads and the shear stress distribution at the thread root were analyzed in detail. It was found that there were three typical load distribution patterns along hole threads, which were (1) linear pattern; (2) concave parabola pattern; and (3) convex parabola pattern, and the ratio of bolt stiffness to tube wall stiffness was identified as the pivotal factor affecting the axial load distribution. Meanwhile, the analysis results indicated that the bending moment on the TOBs did not affect the load distribution along hole threads, but led to a non-uniform stress distribution along the thread in the same turn. In the end, the prediction formulas for the carrying capacity of hole threads are presented by modifying Yamamoto’s equation based on the analysis findings. The formulas are validated against the finite element analysis results and previous test results. The prediction can reach the highest accuracy when adopting the proposed failure criterion 2, with average errors of − 0.001 and − 0.002, respectively, demonstrating the accuracy and reliability.

Axial Compressor Transonic Rotor Shock Interaction With Upstream Stator Row

Abstract Modern multistage axial compressors are designed for high aerodynamic loading and wide range with front stages rotor inlet relative Mach number above one over a large portion of span. Rotor shock waves propagate and reflect in the upstream stator where they provoke extra aerodynamic losses and aeromechanic risks. This paper discusses stator–rotor shock interactions using both steady and unsteady numerical simulations. The computations focus on three different stage designs with the same capacity and total pressure ratio, but different axial gaps and load distribution in stator and rotor. Speedlines from steady and unsteady computations compare the designs, and the detailed flow fields are analyzed at design and close to stall conditions. The steady and unsteady calculations predict similar stage performance, but different stator–rotor loss split. The analyses reveal how the rotor shocks orientation with respect to the upstream stator camber line controls the intensity of shocks interaction with the stator row and its propagation upstream. Finally, the paper indicates the ways to reduce the shock-driven rotor–stator interaction and suggests simple criteria to determine when to switch from steady to unsteady calculations for a reliable transonic stage performance prediction.

Axial live load distribution among single row of piles of integral bridges

This study investigates the axial live load distribution among steel H-piles in single-span integral bridges. To achieve this, two- and three-dimensional finite-element models for various integral bridges are conducted and analysed using the structural analysis software SAP2000, to determine the maximum axial loads in steel H-piles within two- and three-dimensional models. Subsequently, axial live load distribution factors from the ratio of axial loads calculated from these models are derived. The parametric study reveals that girder spacing and pile spacing exert notable influences on the axial live load distribution among the steel H-piles in integral bridges. Then, non-linear regression analysis is employed to formulate practical equations as functions of these two parameters. These equations can effectively calculate the live load distribution factors for the piles in integral bridges. To validate the accuracy of the live load distribution factors calculated from the proposed formulae, a comparative analysis is performed with results obtained from structural analysis. The standard deviations of the ratios between these two results are found to be a mere 2%. This clearly demonstrates that the developed formulae yield highly precise estimates of axial live load effects in integral bridge piles.

The Role of Trabecular, Ligamentous-Intervertebral Disk and Facet Joints Systems: A Finite Element Analysis in the L4-S1 Vertebrae.

Descriptive. Trabecular bone in the vertebrae is critical for the distribution of load and stress throughout the neuroaxis, as well as the intervertebral disk, ligamentous complex, and facet joints. The objective was to assess the stress and strain distribution of the L4-S1 spine segment by a finite element analysis. A lumbosacral spine model was built based on a CT-Scan. Trabecular-to-cortical bone distribution, ligaments, intervertebral disk, and facet joints with cartilage were included. A perpendicular force was applied over the L4 upper terminal plate of 300N, 460N and 600N in neutral, plus 5Nm and 7.5Nm for flexion and extension movements. Maximum principal stress and total deformation were the main studied variables. Trabecular bone confers resistance to axial loads on the vertebrae by elastic capacity and stress distribution. MPS and TD showed axial stress attenuation in the nucleus pulposus and longitudinal ligaments, as well as load distribution capacity. Facet joints and discontinuous ligaments showed greater TD values in flexion moments but greater MPS values in extension, conferring stability to the lumbosacral junction and axial load distribution. We propose 3 anatomical systems for axial load distribution and stress attenuation in the lumbosacral junction. Trabecular bone distributes loads, while the ligamentous-intervertebral disk transmits and attenuate axial stress. Facet joints and discontinuous ligaments act as stabilizers for flexion and extension postures. Overall, the relationship between trabecular bone, ligamentous-intervertebral disk complex and facet joints is necessary for an efficient load distribution and segmental axial stress reduction.This slide can be retrieved from the Global Spine Congress 2023.

Probabilistic buckling assessment and reliability of fiber-metal laminate, composite and aluminum cylindrical panels under compression with load and fabrication uncertainties

The objective of this article is to study the buckling behavior and reliability of fiber metal laminated (FML), composite and aluminum cylindrical panels under uniaxial compression taking into account fabrication and loading uncertainties. A 3D finite element modeling with ANSYS software has been implemented for this purpose. The panels are discretized using shell elements and the eigenvalue buckling analysis is conducted for the prediction of elastic buckling. The influences of load and fabrication uncertainties on the buckling load factor are studied with probabilistic analyses and the reliability of the panels is calculated. It is found that the thickness of aluminum layers is the most significant uncertain variable for the critical buckling load factor of FML panels, whereas the fiber misalignment angle of their composite layers is insignificant. As the metal volume fraction decreases, the sensitivity of the elastic buckling load factor to variations of the axial load distribution is reduced whereas its sensitivity to variations of the thickness of composite layers is increased. Consequently, the metal volume fraction is an important design parameter for the uncertain buckling behavior of the panels.

The Impact of Axial Load Distribution on Brazilian Tensile Testing on Rock

The Impact of Axial Load Distribution on Brazilian Tensile Testing on Rock

Field study on behavior of load distributive compression anchor installed in weathered rock and soft rock

As a load distributive compression anchor (LDCA) consists of multiple anchor bodies and unbonded tendons, the load applied to the tendon is transmitted to grout and ground by the movement of each anchor body installed along the anchor length. Therefore, the load transfer behavior of LDCA is affected by the interference between adjacent anchor body, and the effect of multiple anchor bodies should be considered in the LDCA design. This study performed a series of pull-out field tests on LDCAs installed in soft rock. LDCAs were designed to have various number and spacing of anchor bodies to investigate the effect of multiple anchor bodies. Furthermore, the test results were compared with the results of pull-out field tests conducted on weathered rock to examine the effect of ground conditions. The load-displacement relationship showed that the grout failure occurred in the LDCA installed in soft rock, and thus the ultimate bearing capacity was smaller than that of the LDCA installed in weathered rock. Additionally, the grout axial load distribution indicated that the LDCA installed in soft rock expressed tensile stress in the grout due to the effect of multiple anchor bodies leading to the tensile failure on the grout.

Effect of structural parameters and load states on PTRB’s load distribution

The planetary thread roller bearing (PTRB), as a new type of ball bearing, has the advantages of high-power density, no need to be used in pairs or combinations, and the ability to carry axial-radial combined load and bidirectional axial load. Its load distribution characteristics serve as the basis for building PTRB’s performance models, such as dynamic load rating, static load rating, and friction torque. In this paper, PTRB’s structure and the transmission paths of force were briefly introduced, and the elastic deformation of the threaded roller, inner ring, and outer ring was analyzed on the basis of the Hertz theory and Hooke’s law. Next, the methods for calculating the compressive deformation of shaft when PTRB was under different load states were presented. In view of the nonlinear relation between force and elastic deformation as well as the compatibility equation, the theoretical model of PTRB’s load distribution was set up accordingly. There was a discrepancy between the variation trends and values of load distribution under four axial load states, with a larger load distribution coefficient at the contact point closer to the flange. With the increase of load from 10 to 30 kN, the increase rates of the axial and radial load distribution coefficients were ≯1.2%, so that the load distribution coefficient could be approximately deemed as an inherent characteristic of PTRB. Within the value range of each structural parameter, the variation of the pitch diameter of threaded roller had the most significant effect on axial load distribution coefficient, with a variation rate of 7%; the variation of the number of threaded rollers had a significant effect on radial load distribution coefficient, with a variation rate of 37%; the variation of the remaining structural parameters had a minimal effect on load distribution coefficient, with a variation rate of ≯3%. When a follow-up optimization design is conducted on the performance of PTRB with a fixed dimension, and the contact angle, number of thread teeth per roller, and pitch diameter of threaded roller are deemed as design variables, the load distribution coefficient can be set as a constant value, and the number of threaded rollers can be set as the maximum value to simplify the optimization design process of PTRB’s performance and improve the optimization design efficiency.

Variation in axial load distribution of piles in liquefiable slope by centrifuge test

During seismic loading, the axial pile response is significantly affected, due to the development and dissipation of excess pore pressure in the foundation soil. Positive skin friction is reduced by liquefaction during shaking, while negative skin friction is caused by reconsolidation after the end of the shaking. In particular, the negative skin friction causes a large drag load, resulting in pile compression and settlement. Thus, this study investigated the axial pile response under seismic loading by performing dynamic centrifuge tests on liquefied sand with the slopes of 15° and 27°. The centrifuge tests were conducted to simulate the end-bearing single and 2 × 2 group piles embedded in a liquefied slope. During the centrifuge spinning, the obtained drag load due to the negative skin friction agreed with the value calculated with the beta method for shaft resistance. The model was shaken with sinusoidal base motion with peak amplitudes of 0.1 and 0.2 g, and it was found that the liquefaction caused a loss of spin-induced drag load. The dissipation of excess pore pressure resulted in reconsolidation settlement, leading to large drag loads acting on the pile. In addition, the negative skin friction was found to be larger than the liquefied residual strength recommended in the current practice codes. As a result, it is seen that the consideration of the strength reduction is not necessary for the calculation of negative skin friction induced by reconsolidation, since the liquefied ground regains skin friction after the dissipation.

Tolerance Analysis of Cylindrical Roller Bearing under Combined Radial and Axial Loads

In order to analyze the influence of tolerance values of key parameters for cylindrical roller bearings under combined axial and radial loads, a coupled model, incorporating a dynamic model of cylindrical roller bearings, contact model, and fatigue life model, is developed to investigate the effect of flange angle, roller-end radius, interval of roller length gauge, and roller profile on contact performance and fatigue life. The results show that the grouping design of flange angle and roller-end radius in the tolerance range was helpful for reducing contact ellipse truncation. The difference of the roller length would change the axial load distribution of the bearings. For the longest roller located in the bottom position, the bigger the difference, the bigger the roller tilt angle and carried-axial load. The (0, +2.5 μm) tolerance range of the crown drop can limit the difference of the fatigue life within 20% in the current analysis.

Numerical Modeling of Liquefaction-Induced Downdrag: Validation against Centrifuge Model Tests

Earthquake-induced soil liquefaction can cause soil settlement around piles, resulting in drag load and pile settlement after shaking stops. Estimating the axial load distribution and pile settlement is important for designing and evaluating the performance of axially loaded piles in liquefiable soils. Commonly used neutral plane solution methods model the liquefiable layer as an equivalent consolidating clay layer without considering the sequencing and pattern of excess pore pressure dissipation and soil settlement. Moreover, changes in the pile shaft and the tip resistance due to excess pore pressures are ignored. A TzQzLiq numerical model was developed using the existing TzLiq material and the new QzLiq material for modeling liquefaction-induced downdrag on piles. The model accounts for the change in the pile’s shaft and tip capacity as free-field excess pore pressures develop or dissipate in soil. The developed numerical model was validated against data from a series of large centrifuge model tests, and the procedure for obtaining the necessary information and data from those is described. Additionally, a sensitivity study on TzLiq and QzLiq material properties was performed to study their effect on the developed drag load and pile settlement. Analysis results show that the proposed numerical model can reasonably predict the time histories of axial load distribution and settlement of axially loaded piles in liquefiable soils both during and postshaking.

A parametric study of large piled raft foundations on clay soil

In the present study, three-dimensional numerical analyses have been conducted to understand the behavior of large piled rafts on stiff clay. The effects of pile number, pile spacing, pile length and loading intensity have been examined. For the same soil, the raft thickness is varied such that the its stiffness changes from flexible to intermediate flexible and to rigid. The load-settlement behavior, load-sharing ratio, raft bending moment and pile axial load distribution are presented and discussed in detail. For a higher pile number, locating piles over a larger central raft area is necessary for the effective reduction of differential settlement. For the intermediate flexible raft, addition of piles covering the maximum raft area is not beneficial in decreasing the differential settlement or the raft bending moment. With the intermediate flexible raft, decreasing the pile length can prove to be advantageous in removing hogging differential settlement. Based on the loading intensity and serviceability limit considerations, the appropriate pile configuration can be determined from the results of the parametric study in the cyclical sequence of firstly the selection of pile number, secondly the adjustment of pile spacing, and finally the reduction of pile length.

Both radial and axial load distribution measurement on a V-band clamp by a new load cell design

This paper presents a method for determining the axial and radial load distribution of the moment generated in a V-band clamp and is validated experimentally using finite element analysis (FEA). The method comprises a slotted flange, which is distinguished by having three different profiles for different levels of load symmetrically divided among eight sectors. Each sector is characterised and calibrated. The load cell is analysed using finite element Abaqus software to predict and corroborate the system. In the experimental test, the axial and radial loads are measured using strain gauges for each sector and the total axial load is validated by three button sensors. Tests on the V-band clamp were successfully carried out and indicated a non-uniform distribution of axial and radial loads, with three highlights relating to existing papers: improved results for axial loads, new results for radial loads and an analysis of the moment and its direction, which is consistent with finite element studies.

Research on Contact and Wear Characteristics of the Planetary Roller Screw Mechanism with Screw Misalignments

Misalignments are unavoidable in most applications of the planetary roller screw mechanism (PRSM) due to many potential causes. However, the effect of screw misalignments on the contact characteristics for the PRSM have not been thoroughly investigated. In this paper, a comprehensive analytical procedure for the PRSM performance considering screw misalignments is proposed. First, the contact positions and clearances of the PRSM with screw misalignments are calculated. Next, an improved model is presented for evaluation of the load distribution, in which the variation of axial clearances is taken into consideration. The numerical results are validated by finite element analysis. Then, the precision loss model caused by wear is derived considering the variation of contact forces. The results indicate that the contact positions slightly change due to the misalignment angle of the screw, while the axial clearances and load distribution at the screw-roller interface are significantly affected. At the same time, the contact forces over thread vary periodically. In addition, the screw misalignment aggravates the wear of the PRSM, resulting in accuracy degradation. The theoretical investigations lay the foundation for the engineering application of the PRSM.

Experimental and Computational Study on Conductors Bearing Capacity in Offshore Drilling.

The height of the cementing cement sheath of the conductor for offshore drilling is the key factor affecting wellhead stability. For the influence of the insufficient return height of cement slurry on the mechanical behavior of the conductor after running the conductor by shallow water exploration well drilling, the axial load distribution characteristics and bearing capacity mechanism of conductor were first analyzed from the perspective of operation characteristics of the drilling method. Second, a calculation model of axial bearing capacity of the conductor with the size of the conductor and the return height of cement slurry as variables was established on the basis of the hole enlargement that often occurs during drilling. In addition, the law of the influence of the return height of cement slurry on the ultimate bearing capacity of conductor and the strength difference of the two cementing surfaces between conductor and cement ring and between the cement sheath and submarine soil layer and its changing rules with time were explored and studied by field experiment. It was concluded that the friction between the cement sheath and the soil layer is the key factor that decides the main bearing capacity of the conductor.

Centrifuge modeling of the behaviour of helical piles in cohesive soils from installation and axial loading

Centrifuge modeling offers a viable tool for research in the soil-pile interaction, but this technique has not been used for helical piles in cohesive soils. A centrifuge model test program of helical piles in cohesive soils was carried out to investigate the axial soil-pile interaction and pile failure mechanism. Helical piles were installed while the centrifuge was spinning, which enabled the determination and interpretation of installation torque and pore pressure response of the soil. An analytical model for calculating the installation torque of helical piles screwed into cohesive soils was proposed and verified by test results. The pore pressure response to pile installation was monitored near two piles at two depths. Comparing the measured dissipation curves with the analytical curves for driven piles suggested that the excess pore pressure was primarily induced by the helical pile shaft. The model piles were axially loaded under 20 g condition. The present research may be considered as the first centrifuge test program that measured the axial load distribution along helical piles. The shaft internal loads were recorded using an innovative strain gauging method. The results show that the axial failure modes of helical piles depend on the strength of soil and inter-helix spacing. In general, it may be easier for a stiffer clay to form an inter-helix soil cylinder during axial pile movement.