Effect Of Axial Force Research Articles

Calculating shear lag in steel-concrete composite beams under combined compression and bending

Long and complex composite steel-concrete structures are becoming common, requiring a deep understanding of the effects induced by the simultaneous action of axial forces and bending. In fact, the axial force generated, for instance, by cable inclination in cable-supported structures can modify the stress distribution within the elements compared to bending scenarios, thereby necessitating a revision of the effective width to be utilized. Nonetheless, current design codes, including Eurocode specifications and others, lack provisions for addressing the combined effects of axial force and bending, as they are exclusively tailored for bending. This limitation can introduce design complexities, necessitating the implementation of intricate Finite Element (FE) models, which impose substantial computational loads and design efforts. The methodology proposed in this paper overcomes these challenges allowing to assess the stress distribution and resistance of composite deck at Serviceability Limit State (SLS) and Ultimate Limit States (ULS) by leveraging results obtained from standard beam models typically used by structural designers or practitioners. A comprehensive parametric analysis using nonlinear finite element models is performed to validate the developed methodology. A comparison with the Eurocode 4 formulations highlights that the proposed method provides superior accuracy in estimating peak stress in concrete slabs under combined compression and bending. Additionally, it facilitates straightforward verification at the ULS in compliance with Eurocode requirements.

Study on plastic yield surfaces of pyramidal lattice materials with circular and rectangular cross-sections

The yield surfaces and the evolution of yield surfaces of a bending-dominated pyramidal lattice material under complex stress states considering the coupling effect of axial force and bending moment of a strut are studied theoretically. The two-dimensional primary yield surfaces, secondary yield surfaces, and complete yield surfaces of pyramidal lattice materials of two kinds of cross-section struts are obtained, and the analytical expressions of yield surfaces are established. The effects of the inclination angle and diameter-to-length ratio of the struts on the yield surfaces of pyramidal lattice materials with circular cross-sections are discussed. The results provide a basis for analyzing homogenized plastic properties of complex lattice material structures.

Shear behavior of reinforced concrete walls under variable axial tension‐compression and cyclic lateral loads

AbstractUnder a strong earthquake, the axial force of shear walls in tall buildings may vary from compression to tension, but few studies have been conducted on this. Three low‐aspect‐ratio reinforced concrete (RC) wall specimens subjected to coupled variable axial tension‐compression and lateral load were tested in this study, to investigate the effect of the fluctuating range of axial force and loading histories on the shear behavior of RC walls. The test results indicated that shear‐compression failure occurred under the compressive‐shear loading for all test wall specimens, and no obvious post‐peak strength degradation in tension‐shear loading. The hysteretic curves of test wall specimens were strongly affected by the loading histories; the shear strength and deformation capacity were mainly affected by the fluctuation of axial forces, especially for tension‐shear strength. The equation of ACI 318‐19 and JGJ 3‐2010 conservatively predicted the shear strength of RC walls under the variable axial force, while the equation of ASCE/SEI 43‐05 accurately predicted the shear strength with the mean values of the VTest/VASCE of 0.97 and 0.94 for compression‐shear and tension‐shear strength, respectively. Comparison with an RC wall under constant axial tension revealed that the failure modes of RC walls were strongly dependent on the initial cracking patterns. Finally, a finite element (FE) model was developed, and parametric analyses were carried out to further estimate the effect of variable axial force on the cyclic shear behavior of RC walls.

Analysis of the effect of nonlocal factors on the vibration of nanobeams

Abstract Currently, the Eluer-Bernoulli beam nonlocal theory does not fully consider the effects of foundation deformation and axial force on the beams, and cannot accurately reflect the real mechanical properties of nanobeams. The primary objective of this study is to introduce a novel computational method designed for an enhanced characterization of the vibrational behavior of nano beams. Initially, this method incorporates the influence of foundation deformation on beam bending, accounts for the effects of axial forces, integrates Eringen's nonlocal theory, and establishes a modified Euler-Bernoulli beam theory model for the first time, accompanied by a degradation validation of the model. Subsequently, the Laplace transform and Hasselman's complex mode synthesis method are utilized to solve the model, providing the first derivation of the state-space transfer function for the nano beam vibration model based on the modified Euler-Bernoulli beam theory that includes axial force effects. Lastly, the study elucidates the impact of nonlocal factors and various parameters on the vibration characteristics of nanobeams. The results show that the order n increases, and the peak frequency value moves in the direction where the nonlocal factor tends to zero. When the order n is less than 6, the frequency peak is mainly concentrated in the interval where the nonlocal factor is greater than 0 and less than 0.1. At the same order, the beam length increases, and the peak frequency moves in the direction of increasing non-local factor. The modified geometric parameters and the foundation beam stiffness parameters have a greater effect on the peak of the beam's vibration mode in the higher order case and a lesser effect in the lower order case. The larger the nonlocal factor, the larger the peak of the vibration mode. The foundation beam stiffness parameter also has an effect on the direction of the peak vibration mode at the 1st and 2nd orders. The research results will help to predict the vibration behavior of nano beams under different conditions more accurately and provide an important reference for related applications.

Crookedness detection of thrust ball bearing shaft washer based on nonlinear vibration responses

Bearing misalignments are common defects in machinery. One of the most important types of that is the angular misalignment of the bearing rings. In this study, crookedness specific signature related to thrust ball bearing shaft washer is investigated. For this purpose, a vertical structural thrust ball bearing test rig was considered. In the following, effects of rotational shaft speed, crookedness value and axial external force on the shaft washer crookedness signature were studied at several relative positions of sensors. It is shown that crookedness of thrust ball bearing shaft washer has specific frequency and sensor phase difference pattern in the nonlinear vibration responses. Also, the experimental results are applied to validate results of a 4-dof nonlinear dynamical system related to the shaft washer crookedness of thrust ball bearing. In the next step, by comparing input and output amplitude and also existence of flip bifurcation, it is illustrated that this system is a nonlinear dynamical experimental system. It was shown that this nonlinearity makes crooked shaft washer pattern difficult to identify. Finally, by the phase portrait of the sensor response and the relative error value of crookedness signature frequencies, it is clear that the crookedness of shaft washer creates quasi-chaotic behavior supporting crookedness signature frequencies and phase pattern as a supplement property.

Piezoelectric Hinged Beam with Arc Mass Stopper for Vibration and Human Motion Energy Harvesting.

Compact reliable structure and strong electromechanical coupling are hot pursuits in piezoelectric vibration energy harvester (PVEH) design. PVEH with a static arc stopper makes piezoelectric stress uniformly distributed and widens the frequency band by collision but wastes space. This Article proposes a hinged PVEH with two arc mass stoppers (AS-H-PVEH). Two arc stoppers as movable masses increase the vibration energy and the effective electromechanical coupling coefficient to achieve strong electromechanical coupling. AS-H-PVEH generates a 4.1 mW power output at 11.6-12.0 Hz and 0.2 g. AS-H-PVEH sustains 4 g acceleration vibration for 10 min without attenuation. To offset the resonance frequency increase caused by arc contact, we discuss the magnetic coupling, and axial force effects are discussed. The design of the arc stopper radius, nonlinear electromechanical coupling model, and system parameter identification method are presented. The displacement varied mechanical quality factor and effective electromechanical coupling coefficient are considered in the modified model for the first time. The model obtained good agreement under experiments. The power generation and driven wireless sensor performance of AS-H-PVEH was verified. This research has important theoretical and application value for the performance optimization of PVEH with an arc stopper.

Flexural behaviour of shallow-embedded steel column bases

This paper investigated the flexural behaviour (the initial rotational stiffness and ultimate moment resistance, in particular) of the shallow-embedded column bases through experimental and numerical approaches. Three full-scale tests with different embedded depth ratios (i.e., 0.5, 1.0 and 1.5) were carried out, from which the moment-resisting mechanisms were identified and the effects of the embedded depth ratio on the initial stiffness, moment resistance and ductility were evaluated. The test results were further used to evaluate the accuracy of the available resistance and stiffness models for the shallow-embedded column bases. The resistance models codified in design codes GB 50017-2017 and AISC 341-16 are highly conservative, with an average prediction accuracy of 0.268 and 0.451, respectively; by contrast, the resistance models recently reported in the published articles show better accuracy. The stiffness models are fewer in number and are also inaccurate for the shallow-embedded column bases. Complementary finite-element models were developed and validated. Subsequently, systematic parametric finite-element analyses were performed to investigate the effects of axial force and shear force in the steel column, as well as those of the structural details such as the presence of base plate, arrangement of anchor bolts and width of concrete foundation. Shear force has an adverse effect on both the initial stiffness and moment resistance, and this effect becomes more significant with the increase in the embedded depth ratio; axial compression force leads to an increase in both the initial stiffness and moment resistance, which is more pronounced for embedded column bases with smaller η-values. Among all structural details, the presence of the base plate has the most notable influence on the flexural behaviour of the shallow-embedded column base, increasing both its initial stiffness and moment resistance; comparatively, the effects of the other structural details are minor or even could be ignored.

An enhanced mathematical model for evaluating grid-to-rod fretting wear under complex boundary

Grid-to-rod fretting wear is a significant cause of fuel failure in pressurized water reactors and poses a challenge in fuel performance evaluation. As burnup increases, neutron irradiation can lead to complex changes in the grid-to-rod system, affecting its dynamic behavior. This paper presents an enhanced mathematical model that can simulate the coupled axial-lateral motion and complex boundary conditions, including relaxation support, friction, and gap constraint. Through multiple parametric studies, the model has revealed valuable results. Notably, grid relaxation of 10%–30% significantly impacts wear. Multiple critical excitation frequencies can cause drastic changes in vibration and wear. The increase in holding force due to rod swelling and the early opening of the gap due to creep down require careful attention. Moreover, the effect of axial force on changes in natural frequency and increased wear should be considered.

Investigation on Fracture Behavior of Electroslag Welding Joint with High-Performance Steel

This study aimed to investigate fracture behavior of electroslag welding (ESW) joint with 590-N/mm2 class steel using numerical analysis, covering a range of material scales in the structural level. The extended Mohr–Coulomb (EMC) fracture criterion was employed for finite element analysis (FEA). Uniaxial tensile test and three-point bending test were conducted to analyze the fracture behavior from the material scale and calibrate the fracture criterion. The test specimens consisted of the base metal, heat-affected-zone metal, and welding metal obtained from an ESW joint with a 590 N/mm2 class steel. Subsequently, FEA was conducted for a biaxial tensile test to investigate fracture behavior at a structural scale and verify the feasibility and accuracy of the calibrated fracture criterion. The comparison between the results from the FEA and test suggests that the FEA based on the EMC fracture criterion can accurately predict fracture behavior but tends to overestimate the bearing capacity. Thereafter, the effect of axial force on column was quantitatively investigated. The results suggest that the existence of tensile axial force at column decreases the ductility of ESW joint and shifts the fracture locus from the welding metal to heat-affected zone. However, the force has minimal influence on the pop-in load. Finally, the feasibility of applying the current Japanese specifications designated for the 490 N/mm2 class steel for the 590 N/mm2 class steel was examined. The results indicate that the provision can serve as a safe and reliable guideline for the 590 N/mm2 class steel as well.

Study on the vibration characteristics of double-row tapered roller bearings for high-speed rail axle box

PurposeThe purpose of this paper is to establish a dynamic model considering the actual operating conditions of the train and to study the dynamic performance and vibration characteristics of axle box bearings under different operating conditions.Design/methodology/approachIn this paper, based on the internal contact characteristics of double-row tapered roller bearings, a dynamic model considering the actual operating conditions of the train is established. The correctness of the model is verified by the vibration test of the bearing. Comparative analysis was conducted on the effects of axial force, radial force and rotational speed on the angular velocity of the cage, slip rate and vibration acceleration level of the inner ring.FindingsAs the force increases, the slip rate of the cages on both sides decreases, and the vibration acceleration level of the inner ring increases. With the increase of rotational speed, the cage slip rate of the axle box bearing increases and the vibration acceleration level of the inner ring increases.Originality/valueA dynamic model is established considering the actual operating conditions, and the dynamic performance and vibration characteristics of the axle box bearing under different operating conditions are analyzed by numerical method. The research content can provide reference for the parameter design of high-speed railway bearings.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2024-0085/

In-plane free vibration of a two-cable network with multiple flexible cross-ties considering the effects of dynamic axial forces of the cables

Equipping cross-ties on the cables of cable-stayed bridges to form a cable network is regarded as an effective measure to suppress large cable vibrations and has been realized in practical engineering. However, most of the existing studies on the suspended cable (small sag) network have ignored the contributions of dynamic axial forces to transverse forces of the cables. More importantly, the dimension of the characteristic matrix is relatively large. Therefore, the current study introduces the transfer matrix method (TMM) to solve the in-plane free vibration problem of a two-cable network with dynamic axial forces of the cables considered simultaneously. Compared with the methodology utilized by the previous studies, the dimension of the resulting characteristic matrix is smaller and is independent of the number of cross-ties. Three cases, i.e., a two-cable network with two cross-ties, with three cross-ties and with four cross-ties, are explored in detail. Their frequencies and mode shapes are compared with those obtained by finite element model (FEM) to demonstrate the validity of the results in this paper. Meanwhile, the effects of dynamic axial forces on the first two frequencies and mode shapes are analyzed. The results show that the contributions of dynamic axial forces should be taken into account in transverse forces when calculating the first two frequencies of the cable network with flexible cross-ties.

Higher‐order effect of axial force on free vibration and buckling of functionally graded sandwich beams

AbstractThis paper presents a novel higher‐order shear deformation beam theory for analyzing the stability and free vibration of functionally graded (FG) sandwich beams with emphasis on the effect of higher‐order moment (HOM) and cross‐sectional warping. The governing equation of axially loaded FG sandwich beams is derived from three‐dimensional equations of the theory of elastic waves in bodies with homogeneous initial stresses. The characteristic equations for typical end conditions are obtained exactly. The numerical results of the natural frequencies and critical loads are calculated and verified for special cases by comparing them with the existing solutions. The effects of gradient index, core thickness, HOM, and warping shapes on the natural frequencies and critical buckling loads are elucidated for different slenderness ratios and end constraints.

Numerical and Analytical Study of the Cyclic Behavior of ADAS Damper and the Effect of Axial Force on its Behavior

ABSTRACT The objective of this research was to study ADAS dampers and develop equations to calculate their seismic parameters. A model was used to analyze the dampers with various variables. The study proposed equations for stiffness, energy dissipation, and strength of the dampers. It also identified the variables with the most and least impact on the results. The effect of axial force on damper performance was investigated, including the calculation of critical load and examining its influence on stiffness, strength, and ductility. Reducing the opening area and height and increasing the width of the damper increased energy dissipation and effective stiffness.

Vector form intrinsic finite element analysis for nonlinear parametric resonances of planar beam structures

The parametric resonance of a beam structure may lead to a disastrous consequence. To assess the safety of a structure, structural engineers need a straightforward and practical method to calculate the large-amplitude nonlinear parametric resonance responses of the beam structure. This paper proposes a newly developed vector form intrinsic finite element (VFIFE) calculation scheme to analyse the nonlinear parametric resonance of planar beam structures. By taking into account the geometric stiffness effect of the internal axial force for the frame element, a new relationship between internal nodal forces and deformation components is first established based on the VFIFE principle and the parametric resonance mechanism of frame structures. A numerical example of a portal frame is presented to demonstrate the efficacy of this new calculation scheme. A parametric resonance test of the cantilever beam is conducted to verify the applicability of the VFIFE method. The numerical results show that the proposed scheme can well simulate the nonlinear phenomena of parametric resonances. The numerical predictions are consistent with the experimental observations. A filtering-based finite-time Lyapunov exponent approach is presented to determine the stability boundary of the structure. The numerical stability boundary of parametric resonance agrees well with the experimental boundary. Possible causes of deviations between the numerical and experimental results are discussed. The proposed VFIFE scheme is a simple and effective means of analysing the stability and nonlinear responses of the parametric resonance of planar beam structures.

Vibrational Analysis of Axially Loaded Rayleigh Beams on Variable Winkler Foundations with Implications for Structural Design

In this study, we explore the complex vibration problem of a Rayleigh beam under axial loads, positioned over a variable Winkler foundation with elastic properties changing along its length. The investigation delves into how factors like rotational inertia, axial forces, and foundation properties affect the beam’s dimensionless eigenvalues and eigenmodes. Employing the Differential Transform Method (DTM), we tackle the governing equations across various foundation conditions, including constant, linear, and parabolic variations. The results align well with the previous research, affirming their precision between scenarios considering or neglecting the elastic foundation’s effects. Notably, we emphasize the influence of linear spring stiffness on vibration characteristics, overshadowing rotary spring stiffness. Thus, the important novelty of the study lies in its comprehensive investigation into the vibration dynamics of a Rayleigh beam under axial loads on a variable Winkler foundation with elastic properties varying along its length. The findings illuminate a previously unexplored dynamic: the intricate interplay between linear and rotary spring stiffness, showcasing the dominant impact of linear stiffness on vibration characteristics. Of significant note is the profound effect of axial forces on fundamental eigenvalues, underscoring their critical role in structural behavior. These developments possess substantial practical implications, providing invaluable guidance for the accurate modeling of beams supported by elastic foundation, thereby enhancing structural design and performance.

A Wear Prediction Framework for Ball-Screw of Electro-Mechanical Brake Unit on Railway Trains

The electro-mechanical brake is a new advancement in railway train braking. Ball-screws are important components of electro-mechanical braking units (EMBUs), and their wear can cause EMBUs to degrade in performance or even fail to function. In this paper, we present a framework for prediction of ball-screw wear with discrete operating conditions as inputs, taking into account the time-varying characteristics of EMBUs. The framework includes determining the contact type, analyzing relative motion, calculating contact deformations, and estimating wear. The contact type is determined based on the quasi-static approach of Hertz theory. A dynamics model using multiple coordinate systems is established to analyze how balls and raceways move in relation to each other. The contact deformations of the ball–raceway contact are determined using numerical calculation. Then, the wear depth increment is calculated using the Archard model. The results of the calculation and the endurance test indicate that the wear on the screw raceway is greater than that on the nut raceway. The effect of velocity is greater than the effect of axial force. The presented calculation framework is reasonable and can be used for predicting EMBU ball-screw wear.

Simplified analytical model for prediction of collapse resistance of restrained steel beam-column substructure exposed to fire

This paper provides a simplified analytical model for the restrained steel beam-column substructure under a fire-induced progressive collapse scenario, which is applied to predict the collapse resistance of substructures under fire. The simplified model is formulated for axially and rotationally restrained two-span steel beam-column substructures under column-loss scenarios and involves rigid and semi-rigid connections. The response characteristics of restrained substructures exposed to fire under column-loss scenarios in each response stage are elaborately analyzed. A “negative” catenary stage, in consideration of the unique negative axial force effects induced by the temperature thermal expansion, was first introduced in the five-stage simplified model for restrained substructures exposed to fire against progressive collapse. Subsequently, the explicit calculation formulas for determining the vertical loads and deflection of both rigid and semi-rigid joint substructures exposed to fire were derived in a quantified way, based on rigid-plastic mechanisms and restraint coefficient methods. In addition, the corresponding numerical simulation analysis on a restrained two-span steel beam-column substructure with different end constraints and fire conditions was carried out to verify the applicability and reliability of established theoretical formulas. Comparisons of vertical load-deflection relationships between the calculation formulas and corresponding numerical simulation shows good accuracy. For more accurate prediction results, the error analysis was further conducted, and several theoretical formulas were modified, which were verified to be accurate and reliable after correction. With derived resistance functions, the resistance of steel beam-column substructures in fire-induced progressive collapse scenarios can be predicted.

Effect of joint stiffness on the load-carrying capacity of single-layer cylindrical reticulated shell with improved bolt-column (IBC) joint

To enlarge the application of single-layer reticulated shells, this study proposes an innovative semi-rigid joint based on the original bolt-column (OBC) joint, referred to as the improved bolt-column (IBC) joint. The mechanical behavior of the IBC joint under the pure load and the coupling effect of bending and axial force is investigated using numerical tests. Then, the practical analytical model of IBC joint is developed based on a three-parameters power model and component method. Subsequently, a mechanical model considering joint stiffness is developed to establish semi-rigidly connected single-layer cylindrical reticulated shell. A total of 456 numerical models of shells are conducted to examine the impact of different kinds of joint stiffness on the load-carrying capacity of shells systematically. The results demonstrate that (i) weak axis bending stiffness and axial stiffness significantly affect the load-carrying capacity of shells by approximately 19 % and 14 % on average respectively; (ii) strong axis bending stiffness and torsional stiffness have relatively minor effects on the critical load of shells, with average decline ratios of only 5 % and 6 % respectively; (iii) out-of-plane shear stiffness and in-plane shear stiffness exhibit negligible impacts on the load-carrying capacity of shells, with an average effect not exceeding 1 %. Finally, the findings of numerical simulation considering all stiffness of IBC joint reveal insights into both varying laws of load-carrying capacity and failure modes for shells. It is observed that the mean critical load can reach up to 59 % of the one of rigidly-connected shells, which is significantly higher than those observed in shells with pinned joints.

Nonlinear Performance of Steel Tube Tower in Ultra-High Voltage Transmission Lines under Wind Loads

As complex, statically indeterminate structures, transmission towers are subject to complex forces and are usually simplified into truss structures that only consider the effects of axial force. When the load and deformation of a tower are small, it is reasonable to carry out analysis according to the linear elasticity theory. However, the height of an ultra-high voltage (UHV) transmission tower is significantly large, meaning that the calculation result according to the current elastic analysis method often has a large deviation from the actual stress of the structure. With the influence of the bending moment at the end of the member, a numerical model is established considering the influence of geometric nonlinearity and material nonlinearity in this paper. The stress distribution characteristics and development law of UHV transmission towers in linear and nonlinear stress states are analyzed and studied. The real tower test and elastoplastic ultimate bearing capacity analysis show that the elastoplastic analysis is closer to the actual tower. The UHV steel pipe tower designed according to the linear elasticity and small deformation theory has a large safety margin under the design load, resulting in a significant waste of materials. Under the action of heavy load, the tower exhibits strong nonlinearity, and the influence of geometric and material nonlinear factors should be fully considered when designing the structural components in UHV transmission towers.

Cyclic behavior of a web hourglass-shaped pin damper made of low-yield-strength steel: Experimental and numerical analyses

Web hourglass-shaped pins fabricated from low-yield-strength steel (LYSWHPs) can be utilized as energy dissipation (ED) components in the connections of steel structures to effectively enhance ED and reduce damage to the primary structural components under intense earthquakes. First, quasi-static tests were carried out on three LYSWHP specimens made of LY225 steel; when bolted to its supporting plate, each exhibited a stable, suitable hysteretic response, excellent ED capacity, high ductility factor of 5.01–9.55, and excellent plastic deformation. Axial force effects and large plastic strains significantly increased the strengths of the LYSWHPs, with the maximum overstrength factor reaching 2.36. A finite-element analysis model was established in ABAQUS and confirmed against the behaviors of the test specimens to perform parametric analyses on individual and group LYSWHP models. The results demonstrated that the shape of the LYSWHP significantly affects its load-carrying capacity, ED capacity, and failure mode; the shape factor and slenderness ratio of the ED segment should be within 0.375–0.75 and 2.75–4.25, respectively, to ensure the desired behavior. The number of LYSWHPs, supporting plate thickness, and LYSWHP shape significantly affect the hysteretic behavior of an LYSWHP group. When the supporting plate provides strong restraint, the ED capacity and ductility of each LYSWHP is fully developed, all cumulative damage is concentrated within the LYSWHPs while the supporting and loading plates remain elastic, and the group will exhibit ductile failure. The findings of this study provide reference for the practical application of LYSWHPs in building structures.