Combined Axial Loading Research Articles

Cyclic lateral load test and finite element analysis of high-strength concrete-filled steel box columns under high axial compression

This paper presents an experimental study of the seismic performance of high-strength concrete-filled box columns (CFBCs) under combined axial and cyclic lateral loads. Specimens were made of high-strength SM 570 M steel (with yield strengths between 520 and 580 MPa), and concrete with compressive strength (fc') greater than 80 MPa. Three parameters that affect the seismic performance of CFBCs were investigated: the width-to-thickness (b/t) ratio of the steel column, magnitude of the axial load, and the addition of concrete infill. The specimens, which were 280–420 mm in width and 2000 mm in height, were tested under combined axial (4058–10,090 kN) and cyclic lateral loads. Experimental results indicated that the lateral displacement ductility decreases significantly with an increase in either the axial load or b/t ratio. The addition of concrete infill inside a hollow steel box column does not improve the lateral displacement ductility of CFBCs under high axial load. Although the CFBC specimens satisfied the b/t requirement of a highly ductile member, as per AISC Seismic Provisions (2016), specimens under high axial load (40%Pn) failed at 4% drift, indicating that the requirement does not guarantee that CFBCs will sustain high axial load under significant drift (i.e., >3%). The Eurocode 4 (2009), AISC Specification (2010), and Architectural Institute of Japan (2014) reasonably estimate the flexural strength of high-strength CFBCs under axial load; however, ACI 318 (2011) does not. The finite element analysis program ABAQUS can be used to estimate the hysteretic behavior of specimens before significant strength degradation.

Dynamic stability of cylindrical nanoshells under combined static and periodic axial loads

The dynamic stability of cylindrical nanoshells subjected to combined static and time-dependent periodic axial forces is studied by employing the two-dimensional nonlocal elasticity theory together with the first-order shear deformation theory of shells. The differential quadrature method as an efficient and accurate numerical technique is applied to discretize the equations of motion under different boundary conditions in the spatial domain and transform them into a system of coupled Mathieu–Hill-type equations in time domain. Subsequently, the Bolotin’s first approximation method is employed to extract the dynamic instability regions of the cylindrical nanoshells. The approach is validated by showing its fast convergence rate and carrying out comparison studies with existing results in the limit cases. Afterward, the effects of the nonlocal parameter, length and thickness-to-mean radius ratios together with different boundary conditions on the principal dynamic instability regions of the cylindrical nanoshells are studied in detail.

Critical buckling load prediction of axially compressed cylindrical shell based on non-destructive probing method

Critical buckling load prediction of axially compressed cylindrical shell is investigated based on the non-destructive probing method in this paper. Finite element model of the cylindrical shell under combined axial load and radial probe is established using ABAQUS and the static modified Newton-Raphson method that uses artificial damping is chosen in the geometrically and materially nonlinear buckling analysis. By the means of repeatedly probing the shell under different prescribed axial loads, the three-dimensional representation of probe force, probe displacement and prescribed axial load is established. Based on that, the critical buckling load of the shell is predicted by the fitting curve that reflecting the relationship between the maximum probe force and the prescribed axial load. Applying this prediction method, the perfect cylindrical shell, the cylindrical shells with dimple-shape imperfections and the cylindrical shell with measured imperfections have been studied. All of the predicted results are compared with the real critical loads in buckling behavior of the shells under axial compression. Effects of poker size and probing location on the prediction results are analyzed. Results show that the critical loads for the first buckling pattern of the cylindrical shells with notable local imperfections can be predicted accurately when the shell is probed at the location with the largest imperfection amplitude. If the shell is probed away from that area, the predicted result will become much larger. Compared to the probing location, the poker size has little effect on the prediction results. For the cylindrical shell with measured imperfections, probing at the location with largest imperfection amplitude has achieved the most accurate prediction result. Besides, the predicted critical buckling loads obtained by probing at other locations are also acceptable. It is believed that for a general cylindrical shell without notable local defects, the smallest one of different predicted results obtained by probing a series of representative locations on the cylindrical shell could be regarded as the critical buckling load.

Field and numerical analysis on effect of axial load on the lateral response of a pile

Purpose Piles often carry combination of axial and lateral. Currently, piles are designed separately for axial and lateral load. In the literature, few information is available on the influence of axial load on lateral behaviour of the pile. This paper aims to present the results of load deformation of a pile under pure lateral load and combined axial and lateral load. Design/methodology/approach The field load tests were carried out on four different pile diameters at two different bridge sites. Moreover, the paper addresses the numerical simulation of filed load test carried out on the pile under the combination of axial and horizontal load. Findings After field load tests and numerical simulation, it was found that the vertical load had a remarkable effect on the lateral load response of a pile. The lateral deflection of the pile was decreased about 25% under the effect of vertical load. In addition to this, the results from field and numerical simulation are quite comparable. Originality/value Typical field load tests were simulated numerically. This research adds a value in the areas of pile foundation subjected to vertical and lateral load particularly for structure such as transmission line tower and jetty.

Flexural‐Torsional Vibration of Thin‐Walled Beams Subjected to Combined Initial Axial Load and End Bending Moment: Application to the Design of Saw Tooth Blades

The present paper analyzes the vibration issue of thin‐walled beams under combined initial axial load and end moment in two cases with different boundary conditions, specifically the simply supported‐end and the laterally fixed‐end boundary conditions. The analytical expressions for the first natural frequencies of thin‐walled beams were derived by two methods that are a method based on the existence of the roots theorem of differential equation systems and the Rayleigh method. In particular, the stability boundary of a beam can be determined directly from its first natural frequency expression. The analytical results are in good agreement with those from the finite element analysis software ANSYS Mechanical APDL. The research results obtained here are useful for those creating tooth blade designs of innovative frame saw machines.

Improved SDOF Approach to Incorporate the Effects of Axial Loads on the Dynamic Responses of Steel Columns Subjected to Blast Loads

In this paper, a complicated single‐degree‐of‐freedom (SDOF) approach was developed to determine the global response of steel columns under combined axial and blast‐induced transverse loads. Nonlinear section and member analyses were incorporated into the suggested SDOF method to account for the complex features of the material behavior, the high strain rate effect, and the column geometry. The SDOF technique was validated through comparisons with available finite element and experimental data, and a good consistency was obtained. Then, the validated SDOF approach was utilized to derive the pressure‐impulse curves under various levels of axial loading. The level of the axial load was shown to have a significant influence on the dynamic behavior of a steel column subjected to a blast load.

EXPERIMENTAL INVESTIGATION ON CONCRETE FILLED STEEL TUBULAR COLUMN TO FOUNDATION CONNECTIONS SUBJECTED TO COMBINED AXIAL AND LATERAL CYCLIC LOADING

Abstract This study focuses on performance of CFT column to foundation connections subjected to combined axial and lateral cyclic loading. Experimental investigations were carried out on five specimens with exposed column base and embedded column base connections. The parameters considered were number of stiffeners and embedment depth of CFT column. The force - displacement response of all the specimens were compared. Providing increased number of stiffeners, increase the strength of connection. An additional mesh provided on the embedded connection was found to be good in improving the ductility of the connection which is a feasible solution for composite structures in earthquake prone regions.

Non-symmetric bifurcation and collapse of elastic-plastic thick-walled cylinders under combined radial and axial loading

Thick-walled cylinders, which are loaded by accidentally excessive internal or external pressure, axial force or both, may fail due to non-symmetric bifurcation modes with multiple axial and peripheral waves. These failure modes are most relevant to submarines, onshore- and offshore pipelines, vacuum containers, subsea structures, and pressure vessels. Continuum theory is adopted to analyze the bifurcation behavior of such cylinders, considering large elastic-plastic deformation with non-linear hardening. The presented general comprehensive solution is capable of calculating the loads and deformation at the onset of bifurcation for modes of any order in both axial and peripheral directions. As a case study, several bifurcation limit curves of different orders have been calculated using the proposed theoretical solution for a closed thick-walled long cylinder loaded radially and axially. The results are validated numerically by FEA simulations using commercial software. Limit curves of column buckling (first order) and section-collapse (second or higher order) modes of bifurcation are calculated using the proposed solution. The results demonstrate that adding tensile or compressive axial force to external pressure loading delays the occurrence of the section-collapse bifurcation mode.On the other hand, adding external or internal pressure to an axial compression force, the axial strain at column buckling is also increased. The results also explain and quantify the transition between section-collapse and column-buckling bifurcation modes. While the presented results focus on different modes of non-symmetric buckling, the theory is also capable of calculating the axisymmetric and non-symmetric bulging as well as axial necking bifurcation modes. The presented solution offers deeper insight and substantial help to the designers of thick-walled cylindrical components of structures, particularly those subject to excessive external pressure, possibly combined with an axial force.

Performance of natural rubber and silicone-based magnetorheological elastomers under large-strain combined axial and shear loading

This study presents an experimental investigation on large-strain behavior of natural rubber– and silicone-based magnetorheological elastomers within a larger scope of structural vibration mitigation due to wind, traffic and seismic events. Magnetorheological elastomer samples with different weight percentages of iron particles, additives, and elastomer matrix were fabricated. The microstructures of specimens were examined, and their mechanical properties were investigated by a unique electromagnetic double-lap shear experimental setup capable of applying simultaneous compression and shear loads. The experimental results demonstrated that the isotropic natural rubber–based magnetorheological elastomers exhibit about 30% magnetorheological effect under large strains, while they achieve a higher magnetorheological effect under the combined axial and shear loading. The magnetorheological effect was 92% and 33% for 10% and 100% shear strains when 100 psi axial stress was applied. A natural rubber–based magnetorheological elastomer was further investigated applying dynamic cyclic load with and without compression load for different strains, frequencies, and magnetic field intensities. It was observed that for higher frequency, magnetorheological effect was reduced. Magnetorheological effects were 73% and 29% for 0.1 and 10 Hz frequencies, respectively, under 100 psi axial stress at 150% shear strain. The result of this study suggests that isotropic natural rubber–based magnetorheological elastomers may be suitable for high-demand-force applications, and in particular, in civil structures.

Mechanical and failure properties of rocks with a cavity under coupled static and dynamic loads

In this study, a series of one-dimensional coupled static and dynamic loading tests were performed by using a modified split Hopkinson pressure bar. Intact prismatic sandstone specimens and specimens with a prefabricated internal circular cavity were tested. The results show that, the dynamic strength of intact specimens and specimens with a cavity decreases with the increase of axial static pressure under 20–70% of the uniaxial compressive strength (UCS). However, the combined dynamic-static strength of intact specimens and specimens with a cavity increases slightly with the increase of the axial static pressure. Besides, the total strain of specimens under coupled axial static and dynamic loads is approximately a fixed value (about 1.16%). Under a low axial static pressure (20–40% of UCS), dynamic load plays a major role in rock failure, resulting in tensile splitting failure in intact specimen; under a medium axial static pressure (60% of UCS), both of static and dynamic loads play a major role in rock failure, resulting in a composite tensile-shear failure in intact specimen; under a high axial static pressure (70% of UCS), static load plays a major role in rock failure where shear failure occurs in intact specimens. However, for the specimen with an internal cavity, no matter how large the axial static pressure is, X-shaped shear failure occurs under the combined axial static and dynamic loads.

Response of UHPFRC Columns Submitted to Combined Axial and Alternate Flexural Loads

This paper deals with the experimental determination of ductility of ultra-high-performance fiber-reinforced concrete (UHPFRC) columns with longitudinal passive reinforcement, tested under combined axial and alternate flexural load. The influence of axial load has been studied, as well as the presence or not of a reduced shear reinforcement. One companion column made of ordinary concrete and with a high shear reinforcement ratio has also been tested for comparison. The ductility has been assessed with energy dissipation and ductility coefficient calculations. In addition, the maximum bending moment has been compared with theoretical calculation, using the material characteristics determined from characterization tests. The paper concludes that UHPFRC columns with a longitudinal reinforcement which have not been specifically designed for seismic resistance do display a ductility coefficient higher than 2 and a noticeable ability to protect the rebars from buckling, but have a rather high decrease of bending moment under the succession of series of alternate flexural load cycles.

Performance of a gasketed joint under bolt up and combined pressure, axial and thermal loading – FEA study

In this paper the strength and sealing performance of a gasketed bolted flanged pipe joint is studied under bolt up and combined operating conditions using 3D nonlinear finite element analysis. The key combinations of internal pressure, axial and thermal loading are considered. The strength of the joint is seen to be affected by the axial and thermal loading combination whereas the joint sealing is seen to be dependent on the bolt up strategy during assembly and is slightly affected under pressure but only partially affected under axial loading in certain locations. Thermal loading was also considered and was found to have a significant effect on the sealing performance up to 100 °C, but beyond that no sealing was observed, resulting in the possibility of leakage and hence increasing the risk of overall joint failure. Finally, the joint load capacities are determined under various combined loadings showing its safe and unsafe operational limits.

Hybrid corrugated members subjected to impact loading: Experimental and numerical investigation

Latest development in material and manufacturing technologies make it possible to increase the yield strength of steel to more than 1200 MPa. These steel grades, suitable for structures prone to extreme loadings, give potentials for considerable weight reduction and a cost-effective way to produce energy-efficient members. Having analysed the impact behaviour of corrugated members recently, this paper now investigates the performance of hybrid corrugated (HC) sections consisting of mild-steel corrugated plates and ultra-high strength (UHS) steel tubes. Three different types of trapezoidal corrugated plates are considered so as to examine the effect of geometrical corrugation parameters on the performance of entire member. Along with this, in order to study the contribution of UHS tubes in the performance of HC members under impact loading, their performance is also examined separately. In combined lateral impact and axial loading scenario, the tube is initially compressed axially; thus an indenter perpendicularly impacts the specimen at mid-span. An advanced numerical model in which nonlinear strain-rate dependent material behaviour of steel is taken into account is also developed by using ABAQUS/Explicit. Thus, the residual deformations, time histories, global lateral deflection, and energy absorptions are discussed and compared with those of experimental results.

Nonlinear analysis of cylindrical roller bearing under the influence of defect on individual and coupled inner–outer race

In this paper, new mathematical model has been developed for the cylindrical roller bearing by considering coupled influence of radial deflection due to normal loading, roller titling, roller skewing, radial clearance, and also individual as well as coupled inner and outer race defects. Novel defect function is also developed for inner and outer race defects based on literature, to make a set of nonlinear equations for mathematical model, which are solved by using MATLAB. Newmark-β method is applied to solve the equation of motion. The results are plotted in time domain, velocity-displacement, and envelope analysis. The obtained results show the sensitiveness of the system with the variations in speed for the inner, outer, and combined inner–outer race defects. The peak displacement, velocity, and acceleration have been observed for various defects which are helpful to obtain the system’s dynamic behavior under speed varying condition for combined radial and axial load. A major finding of this paper is regarding the understanding of the system’s behavior like periodic to chaotic under varying speed conditions with the attention of individual and coupled inner and outer race defects with the inclusion of normal loading, tilting, skewing, and radial clearance effect and validation of simulated results with the calculated one.

Effect of welding and complex loads on the high-strength steel T-stub connection

After welding, a heat affected zone (HAZ) is formed in the area near a weld toe. The main microstructure is composed of high-strength steel (HSS) that is not stable at high temperatures. Therefore, it is necessary to investigate whether EC3 formulae based on examining a mild steel T-stub can be used to design an HSS T-stub. In the study, an experiment with two groups of Q690 T-stubs was performed. The results indicate that the EC3 formulae cannot be directly used to design the HSS T-stub. The effect of HAZ was further investigated by performing a finite element analysis (FEA). With respect to the specimens in the study, the factor χHAZ that represents the effect of HAZ is quantified by using the results of the experiment and FEA. The modified EC3 method2 was validated to accurately predict the first yield resistance of HSS T-stub. The T-stub is subjected to combined axial and shear loads. The relation between transversal and axial displacements of the T-stub under combined axial and shear loads was established. The effect of combined axial and shear loads on the connection behavior of the HSS T-stub was examined through the FEA. The result shows that the ductility of the T-stub under combined axial and shear loads is lower than that of the T-stub under axial load. We introduce a factor χCL to propose a formula to predict the first yield resistance of HSS T-stub by considering the effect of combined axial and shear loads.

Experimental study on seismic performance of partially precast steel reinforced concrete columns

This paper aims to develop two kinds of innovative precast steel reinforced concrete columns, which are partially precast steel reinforced concrete (PPSRC) columns and hollow precast steel reinforced concrete (HPSRC) columns. Both the two kinds of composite columns have precast reactive powder concrete (RPC) shells, and the PPSRC column has a cast-in-place column core. In this paper, a series of cyclic loading tests on 10 column specimens subjected to combined static axial loading and cyclic lateral loading were carried out to explore their seismic performances. All specimens were evaluated by the failure modes, hysteresis characteristics, strength and stiffness degradation, energy dissipation capacity and ductility. The effects of section shape, stirrup spacing, axial compression and concrete strength of cast-in-place inner-part were investigated in details. The experiment results indicated that the PPSRC columns exhibited more satisfactory seismic behavior than the HPSRC columns in terms of hysteretic behavior, strength degradation, ductility and energy dissipation, while their bearing capacities were almost identical under low axial compression. Steel fibers could effectively prevent the cracked concrete from spalling, therefore, the encased steel shape was efficiently confined by the surrounding concrete during the entire test process. Higher stirrup ratio and lower axial compression of the column leaded to more satisfactory energy dissipation capacity, stiffness degradation and higher ductility. Based on the plastic stress theory, the seismic bending moment capacity analysis was conducted, and the results obtained form the formulas agreed well with those from the experiments.

A liquid spring–magnetorheological damper system under combined axial and shear loading for three-dimensional seismic isolation of structures

This study focuses on experimental investigation of a fail-safe, bi-linear, liquid spring magnetorheological damper system for a three-dimensional earthquake isolation system. The device combines the controllable magnetorheological damping, fail-safe viscous damping, and liquid spring features in a single unit serving as the vertical component of a building isolation system. The bi-linear liquid spring feature provides two different stiffnesses in compression and rebound modes. The higher stiffness in the rebound mode prevents a possible overturning of the structure during rocking mode. For practical application, the device is to be stacked together along with the traditional elastomeric bearings that are currently used to absorb the horizontal ground excitations. An experimental setup is designed to reflect the real-life loading conditions. The 1/4th-scale device is exposed to combined dynamic axial loading (reflecting vertical seismic excitation) and constant shear force that are up to 245 and 28 kN, respectively. The results demonstrate that the device performs successfully under the combined axial and shear loadings and compare well with the theoretical calculations.

Effects of combined environmental exposures and axial load on CFFT

Concrete-filled fiber-reinforced polymer tube (CFFT) columns have demonstrated superior advantages on mechanical behavior and ease of construction during the past few decades. The fiber-reinforced polymer (FRP) tube not only improves the mechanical properties of the concrete core by confinement, but also provides a protection layer for the concrete against the outer corrosive environment. However, one obstacle hindering the greater acceptance of the FRP composite as a conventional construction material in civil engineering applications is the susceptibility of FRP to complex, severe environmental exposure. The purpose of this study is to investigate the durability of CFFT cylinders with glass fiber reinforced polymer (GFRP) tubes under exposure to combined freeze/thaw, heating/cooling, and wet/dry cycles. The effects of combined sustained load and environmental conditions were also investigated during this study. Compression and hoop tensile tests were carried out on both conditioned and controlled specimens. In addition, scanning electron microscopy (SEM) and differential-scanning calorimetry (DSC) tests were used to characterize the aging effect on physical and thermal properties of FRP material. Test results showed that more pronounced degradation occurred on the ultimate strain than on the ultimate strength. The sustained load had a negative effect on CFFT cylinders by creating more microcracks in the GFRP tube.

Capacity of exposed column base connections subjected to uniaxial and biaxial bending moments

ABSTRACT Current guidelines do not address the design of column base connections under combined biaxial bending moment and axial load. An analytical study is conducted to develop a biaxial moment-axial load interaction curve for design of exposed, unstiffened column base plates. First, a 3D finite element analysis model is developed for these connections. The response of the model is validated through a series of existing experimental data. Next, the model is used to investigate the response of a few connections subjected to various biaxial moments and axial loads. Based on simulation results, a simple and reasonably accurate interaction equation is proposed. Since the uniaxial capacities of the connection are involved in the interaction curve, an analytical method for predicting the uniaxial capacities, is also presented. This analytical method, which is based on formation of plastic mechanisms, is able to predict the strength of flexible base plates with high accuracy. The behavior of exposed base plates with I-shaped columns under minor-axis moments is also studied. Findings of this study assists practitioners with a reliable and convenient column base connection design.

Effect of rod-to-grain angle on capacity and stiffness of axially and laterally loaded long threaded rods in timber joints

Long threaded rods have recently been widely used as a reinforcement of glued laminated timber in perpendicular to the grain direction. The recent research has thus focused mainly on the withdrawal properties of the threaded rods in the axial direction. Utilizing their large withdrawal stiffness and strength, the threaded rods can also effectively be used as connectors in moment resisting timber joints. Yet, in joints, the threaded rods are often imposed to a non-axial loading, due to inclination of the rod axis to the grain as well as loading direction different from the rod axis. No design models are currently available for the combined axial and lateral loading of the threaded rods. In the present work, the effects of the rod-to-grain and load-to-rod angles on capacity and stiffness of the threaded rods are investigated by use of experiments and finite element models. Based on those, analytical expressions for determining stiffness and capacity of axially and laterally loaded threaded rods are proposed, intended as a basis for practical joint design. Furthermore, effect of various boundary conditions applied at the rod-ends is studied.