Variable Axial Load Research Articles

Vibration analysis of laminated composite higher order beams under varying axial loads

The article develops a computational mathematical model to predict the dynamic response of composite laminated beam under variable axial load using a third higher order shear deformation beam theory, for the first time. The geometrical kinematic relations of displacements are portrayed with higher parabolic shear deformation beam theory. Constitutive equations of composite beam are used on the basis of plane stress problem. The variable axial load is distributed along the axial direction by: constant, linear, and parabolic functions. The equations of motion and associated boundary conditions are derived using Hamilton's principle. Then, the variable coefficients-differential equations of motion are discretized in spatial direction by using numerical differential quadrature method (DQM). The proposed model is verified with previous works available in literature. Parametric analyses are developed to present the influence of axial load type, orthotropy ratio, slenderness ratio, fiber orientations, and boundary conditions on the natural frequencies of composite beams. The present enhanced model can be used specially in designing of spacecrafts, naval, automotive, helicopter, the wind turbine, musical instruments, and civil structures subjected to the variable axial loads.

Full scale study of pile response to EPBS tunnelling on a Grand Paris Express site

This article presents a full-scale experiment on the effect of EPBS tunnelling on pile foundations in the Paris area. Three cast in-situ piles, instrumented with strain gauges and optical fibre cables, were installed at different distances from tunnel axis with various pile base positions to monitor pile strains as the EPBS progresses. This paper investigates pile – soil differential settlements at ground surface, axial load variations, shaft friction mobilization, base load variations, bending moments and pile structural failure possibility. The pile behaviour changed depending on the pile position with respect to the tunnelling machine, with the main changes occurring during the passage of the EPBS beneath or at pile level. Estimation of pile behaviour based on simplified modelling was confirmed by the field monitoring.

Analysis of the axial load of bolts of wheel-mounted brake discs of high-speed trains

In this paper, the axial load of bolts connected to the brake disc under emergency braking conditions with different initial speeds was tested by a 1:1 bench test. A finite element model was established to analyze the evolution law of the bolts’ axial load in the braking process in detail. The results show that the axial load variation range of bolts of the bench test first increased and then decreased with the increase of emergency braking initial speed. The maximum load value (59.4 kN) appeared under emergency braking conditions with an initial speed of 280 km/h. The variation range of the bolts’ axial load of the simulation was 55.5 kN, and the error was 7% compared with the test. The influence of material changes of disc and bolt on bolts’ axial load in the braking process was summarized, thus providing a reference for the material selection of bolt and disc.

Experimental and numerical analyses of seismic behavior of concrete shear wall with opening accompanied by steel frame and eccentric encased steel braces

Reinforced concrete shear walls with the steel reinforced concrete frames is a common lateral force resisting structural system that is applied high-rise steel buildings in various forms. In this study, seismic behavior of two reinforced concrete (RC) shear walls with openings accompanied by steel reinforced concrete (SRC) on scale of 1/3 were investigated. One of the shear walls consisted of a steel truss reinforced concrete (STRC) with a specified eccentricity in each story level and its end was connected to the bracing’s steel beam. Both of the shear walls were coincidentally subjected to specific constant gravity load and cyclic load. Behavior assessment of shear walls included determination of the failure mode cracking pattern, loading capacity, strength, stiffness and dissipated energy with respect to generated deformations. Results revealed that the shear wall with encased steel brace (ESB) was more effective in terms of all the mentioned parameters compared to SRC wall. In the following, pushover curves for shear walls were investigated using finite element (FE) models and confidentiality of analytical models and prediction of behavior of these walls were verified based on real prototypes. Finally, effects of axial gravity load variations on FE models of both shear walls were evaluated. This study can be useful in applied structural engineering because of applying eccentric braces in openings of a reinforced composite shear wall.

Numerical Study on Effect of Constant and Variable Axial Loads on RC Column Subjected to Blast Load

Numerical Study on Effect of Constant and Variable Axial Loads on RC Column Subjected to Blast Load

Effect of variable axial load on seismic behaviour of reinforced concrete columns

This study investigated the effect of variable axial loads (time-varying axial loads) on the seismic performance and failure mechanism of reinforced concrete (RC) columns with different constraints at the top. The contribution of horizontal and vertical ground motions to the variation in the axial force was revealed by evaluating the axial forces on the RC frame columns and bridge piers under the action of near-fault ground motions. The variation law of the axial force was arrived at using the fast Fourier transform (FFT). Based on previous experiments, 30 cases were designed to discuss the effect of various parameters, namely amplitude, frequency and phase of the variable axial load on the seismic performance of the column. The hysteresis behaviour of specimens under different variable axial loads in terms of hysteresis loops, skeleton curves, stiffness degradations, and energy dissipations were analysed. The results indicated that the frequencies of the variable axial load and lateral displacement of the RC column were constants related to the characteristics of the structure. In addition, variable axial loads were detrimental to the seismic performance of the RC columns, especially those with a large amplitude variation, high frequency, and an identical phase as the lateral drift. It is unsafe to design or evaluate the column based on a constant axial load. Furthermore, constraints at the top of the column strengthened the effect of the variable axial load on the seismic performance of the column, and this resulted in an opposite influence rule of the variable axial load.

Experimental Study on Mechanical Properties and Seepage Laws of Raw Coal under Variable Loading and Unloading Rates

This manuscript studied the effects of variable axial pressure loading rate and variable confining pressure unloading rate on the deformation behavior and seepage characteristics of raw coal under alternate loading and unloading of axial pressure and confining pressure. It believed that as axial stress increases, axial strain ε 1 decreases, radial strain ε 3 increases, and permeability k decreases, and ε 1 ′ , ε 3 ′ , and k ′ increase when confining pressure is decreases. With the loading of axial stress and the unloading of confining pressure, the variation amplitudes of ε 1 ′ , ε 3 ′ , and k ′ values reduce gradually. During axial stress loading, the rise in the amplitude of ε 1 is larger than that of ε 3 and the reduction in the amplitude of k , indicating that ε 1 is more sensitive to axial stress than ε 3 and k . During unloading of confining pressure, the increase rate of ε 3 is larger than that of ε 1 and k ; also, ε 3 showed a high sensitivity to confining pressure. In the stage of axial stress loading and confining pressure unloading, the evolution law of deformation and permeability parameters is basically consistent with the change in loading and unloading rate.

Vertical Displacement of a Single Pile Due to Axial & Lateral Loads

Pile foundation supports the upper structure to the subgrade, generally vertical loads. Still, if horizontal loads are very dominant, such as bridges, tall buildings, and tower structures, it must be calculated. Pile foundations with combined loads are generally analyzed. The axial load is first to determine the axial carrying capacity and vertical displacement, then the lateral load to determine the lateral bearing capacity and lateral deflection. In the field, the two loads work together/simulant. In Indonesia, loading tests do not simultaneously, so in construction, it does not account for the additional vertical displacement and lateral deflection due to the load that works simulant. However, there has been an association in ASTM D3966-07 about the simulant loading test. This research will investigate the analysis and experimental laboratory, the effect of vertical displacement on a single pile foundation, as the effect of combined loads. Also, it gets a relationship that can be used as a reference for analyzing additional vertical displacement due to combined loads on pile foundations based on available independent loading test. The research will be divided into two stages. Stage I is an analysis with the Finite Element Method (FEM) approach. Phase II is a laboratory model experimental test, which is inbox (100x100x80) cm3 filled silty sand soil as an illustration of conditions in the field, single pile foundation using steel with a length of 50cm and 60cm, the diameter of 1.5cm and 2cm, with axial and lateral load variations and combined loads. The results obtained show that after adding vertical load (Pu) about 5x, lateral load (Hu) on (Pu/Hu > 5) and the vertical displacement stays like the loading test until it collapses. Another (Pu/Hu ≤ 5), the lateral load, will increase the significant vertical movement due to the combination load. With axial load five times greater than lateral load, there is no increase in vertical displacement. Still, at an axial load less than five times the lateral load, there is an increase in vertical displacement that needs to be considered.

Effects of Pile Tip Support Condition on Pile Behavior under the Action of a Large Earthquake

AbstractEffective methods for evaluating the bending moment of a pile caused by lateral forces at the pile head are available. However, the effects of axial load variation caused by the overturning...

Generalized Loading Protocols for Experimentally Simulating Multidirectional Earthquake Actions on Building Columns in Regions of Low-to-Moderate Seismicity

AbstractThis study aimed to quantitatively develop realistic quasi-static loading protocols for simulating bidirectional cyclic actions and axial load variation on building columns in a way that is...

Thermal stress analysis of energy piles

This study is concerned with the problem of energy piles subjected to constant axial load and temperature variation uniform over the cross-section. In the first part of this paper, equations for the analysis of energy piles based on elastic theory and the load-transfer approach are described. Closed-form solutions are derived for a few simple cases. It is observed that temperature variation effects can be conveniently expressed by a factor of thermally imposed strain. In the second part of the paper, a study on the effect of the non-linearity of reinforced concrete on the performance of energy piles under tension is described. A newly developed finite-element model that is within the framework of the load-transfer approach is employed to simulate the response of a pile subjected to thermomechanical loads in isolated as well as in piled raft foundations. The results suggest that the performance of the structure is strongly affected by concrete post-cracking behaviour. Nevertheless, piles can accommodate thermally imposed strains if the ductility capacity is provided. The outcomes of this study may be combined with the knowledge of non-linear behaviour of soil–pile interfaces for a more rational performance-based design approach toward energy piles.

Seismic behaviour of enlarged cross steel-reinforced concrete columns under various loadings

Based on finite element software, a simulation programme is used to evaluate the seismic behaviour of new-type steel-reinforced concrete (SRC) columns, called enlarged cross steel-reinforced concrete (ECSRC) columns. With abundant simulations, the effects of the loading paths, number of loading cycles, incremental amplitude of displacement and variable axial load on the seismic response of the ECSRC columns were investigated. The results indicate that the seismic behaviour of the column is highly dependent on the loading paths, and it was observed that the loading paths produced a significant effect on the hysteretic response of the columns. Compared with those under uniaxial loading, the yield load, maximum load, ultimate displacement and ductility coefficient of the ECSRC columns under biaxial loading are reduced by 13.47%, 18.01%, 12.17% and 32.64%, respectively. The energy dissipation capacity of the columns is highly dependent on the loading paths. The skeleton curves are not significantly influenced by the number of loading cycles until the yield point of steel and longitudinal reinforcement is reached. With an increase in loading cycles, the yield load, yield displacement, ductility coefficient and maximum load, as well as the corresponding horizontal displacement of the column, are reduced, while the energy dissipation grows. In addition, the yield displacement, yield load, and ductility coefficient increase with an increase in the incremental amplitude of displacement; however, the energy dissipation decreases under these conditions. The seismic performance of the SRC column under variable axial loads clearly exhibits asymmetry that is worse than that observed under constant axial loads.

Discussion of “Experimental Evaluation and Numerical Modeling of Wide-Flange Steel Columns Subjected to Constant and Variable Axial Load Coupled with Lateral Drift Demands” by Julien Cravero, Ahmed Elkady, and Dimitrios G. Lignos

Discussion of “Experimental Evaluation and Numerical Modeling of Wide-Flange Steel Columns Subjected to Constant and Variable Axial Load Coupled with Lateral Drift Demands” by Julien Cravero, Ahmed Elkady, and Dimitrios G. Lignos

Closure to “Experimental Evaluation and Numerical Modeling of Wide-Flange Steel Columns Subjected to Constant and Variable Axial Load Coupled with Lateral Drift Demands” by Julien Cravero, Ahmed Elkady, and Dimitrios G. Lignos

Closure to “Experimental Evaluation and Numerical Modeling of Wide-Flange Steel Columns Subjected to Constant and Variable Axial Load Coupled with Lateral Drift Demands” by Julien Cravero, Ahmed Elkady, and Dimitrios G. Lignos

Analytical Estimation of the Residual Drift of Reinforced Concrete Columns under the Ultimate Displacement Capacity

Reinforced concrete columns are the most important structural elements that determine the ductility of the structures. The main parameters affecting the behavior of reinforced concrete columns are axial load level, shear span, percent of longitudinal reinforcement and percent of transverse reinforcement. The aim of this study is to examine residual damage behavior of RC columns under cyclic loading similar to the earthquake loads combined depend on variable axial load level, spanning to depth ratio, longitudinal reinforcement ratio and transverse reinforcement ratio. When the results of experiments are examined, it can be seen that the residual drift ratio of reinforced concrete columns can be used to characterize the damage occurred in the structure after earthquake or loading. In addition, the performance level of the reinforced concrete columns according to the residual drift ratio is defined in FEMA356. As a result of this study, the analytical equation that calculates the residual drift ratio of the reinforced concrete columns at the ultimate displacement limit is proposed.

Optimal weight for buckling of FG beam under variable axial load using Pareto optimality

In real situation, magnitude, distribution and/or location of axial loads causing a buckling are not known precisely, due to a lack of loading under different operational conditions. Thus, functionally graded structures have to be designed optimally in order to realize their potential. For this reason, this article investigates buckling of functionally graded (FG) beam under variable axial load and optimizes its wight to get the maximum buckling load. The gradation of beam through the thickness direction is described by different function distributions (i.e.; symmetric power and sigmoidal functions). Equations of equilibrium are developed on the basis of higher order shear deformation beam theory by using Hamilton’s principles. Load distribution through the axial direction is portrayed by step, linear and parabolical continuous functions. Numerical differential quadrature method (DQM) is used to solve the equilibrium equations and get buckling loads. Multiobjective optimization procedure is performed to design FG beams under varying axial load for maximum buckling load and minimum weight objectives. Pareto front representation of the best light weight design of a beam under variable axial load that maximizes the critical buckling load parameter is predicted through optimization process. The proposed model is efficient in analysis, design and optimizing an isotropic and FG beam under variable in-plane load.

WITHDRAWN: Dimension effect on the seismic behaviour of column by varying effective length-depth ratios

Abstract In the past few years, the seismic vulnerable zones are getting increased in India which increases the importance of the seismic study. The objective of this study is to assess the seismic behavior of the column with different effective length to depth ratio. By varying effective length to depth ratio under the seismic load, the seismic behaviors of columns have been found out. To choose the optimum and safest effective length to depth ratio, the building model has been created and fully analyzed under the seismic load by using STAAD.Pro. The effective length to depth ratio has been chosen as 7.5, 6, 5, 4.28, 3.75, and 3.33. The variation of axial load, Bending Moment & nodal displacement has been plotted against the location of the column. The suitable effective length by depth ratio of the column to withstand under the seismic load safely and also the economical size out of the chosen 6 ratios has been found out.

Bidirectional Response of Weak-Axis End-plate Moment Connections: Numerical Approach

Brittle failure mechanisms can affect the seismic performance of structures composed of intersecting moment resisting frames, if the biaxial effects are not considered. In this research, the bidirectional cyclic response of H-columns with weak-axis moment connections was studied using numerical models. Several configurations of joints with bidirectional effects and variable axial loads were studied using the finite element method (FEM) in ANSYS v17.2 software. The results obtained showed a ductile behavior when cyclic loads are applied. No evidence of brittle failure mechanisms in the studied joint configurations was observed, in line with the design philosophy established in current seismic provisions. However, beams connected to the column minor axis reached a partially restrained behavior. Joints with four beams connected to the column exhibited a partially restrained behavior for all axial load levels. An equivalent force displacement method was used to compare the hysteretic response of 2D and 3D joints, obtaining higher deformations in 3D joints with respect to 2D joints with a similar number of connected beams. Consequently, design procedures are not capable of capturing the 3D deformation phenomenon.

Axial Load Variation of Columns in Symmetrical RC Buildings Subject to Bidirectional Lateral Actions in Regions of Low to Moderate Seismicity

ABSTRACT Columns in building frame systems are subjected to the combined action of bidirectional horizontal loading and axial load variation during an earthquake. Whilst the behaviour of RC columns under unidirectional and bidirectional lateral loading with constant axial load is understood well, the behaviour under bidirectional lateral loading with axial load variation is rarely studied, especially for limited ductile RC columns prevalent in regions of low to moderate seismicity. This paper begins with a numerical study that aims to obtain the generalised patterns and range of axial load variation in RC building columns. To this end, a case study building is subjected to a suite of 15 ground motions, representative of low to moderate seismic regions, in OpenSees. This is followed by an experimental study in which limited ductile high-strength RC columns are tested under bidirectional lateral loading and two different axial load variation protocols, namely synchronous and nonsynchronous variable axial loading protocols. The results of the numerical study demonstrated that axial load variation of the columns in an RC building is primarily dependent on the response spectral acceleration corresponding to the fundamental period of the structure in the two orthogonal horizontal directions and/or the vertical direction. The results of the experimental testing showed that nonsynchronous axial loading (compared to constant and synchronous axial loading) results in the lowest collapse drift capacity and energy dissipation of the RC columns.

Static stability of higher order functionally graded beam under variable axial load

This article investigates effects of axial load distribution on buckling loads and their modes of functionally graded (FG) beams including a shear effect for the first time, since all previous studies focused on constant axial load. The parabolic higher order shear theory of Reddy is proposed to consider the shear effect of both thick and thin beams. The gradation of the material is distributed continuously through thickness direction with generalized power-law function. The in-plane axial compressive load is simulated by continuous functions through the axial direction, which are constant, linear, and parabolic functions. The equilibrium equations are developed by Hamilton’s principles, which yields variable-coefficients differential equations. Modified differential quadrature method (DQM) is employed to discretize and mesh the spatial domain and covert the differential equations and boundary conditions to algebraic equations. Algebraic set of equations is formed as a generalized matrix eigenvalue problem, then solved to obtain buckling loads (eigenvalues) and mode-shapes (eigenvectors). Numerical results are presented to illustrate effects of gradation parameter, load types, slenderness ratio and boundary conditions on buckling loads and mode-shapes of functionally graded beams structures. This model can be applied in designing of space-shuttle, spacecraft, nuclear structure, and naval structure subjected to distributed in-plane axial load.