Eccentric Compressive Force Research Articles

Nonlinear Analysis on Large Deformations in a Slender Beam with Hinged Support subjected to Eccentric Compressive force

Nonlinear Analysis on Large Deformations in a Slender Beam with Hinged Support subjected to Eccentric Compressive force

Flexural Behavior of RC Beams Using Fe-Based Shape Memory Alloy Rebars as Tensile Reinforcement

Recently, various studies for the use of Fe-based shape memory alloy (Fe-SMA) in the construction field have been widely conducted. However, most of the studies for using Fe-SMA are carried out for applying Fe-SMA for strengthening deteriorated structures. However, if Fe-SMA is used as a reinforcement for new structures, the disadvantages of conventional prestressed concrete can be effectively solved. Therefore, in this work, an experimental study was conducted to evaluate the flexural behavior of concrete beams in which Fe-SMA rebars were used as tensile reinforcement. For the study, ten specimens were constructed with the consideration of the cross-sectional area and activation of Fe-SMA rebars as experimental variable. Activation of the Fe-SMA rebars by electrical resistance heating applied an eccentric compressive force to the specimen to induce camber. The camber increased by an average of 0.093 mm as the cross-sectional area of the Fe-SMA rebar increased by 100 mm2. It was also confirmed through the four-point bending tests that the initial crack loads of the activated specimens were 47.6~112.8% greater than those of the nonactivated specimens. However, the ultimate strength of the activated specimens showed a slight difference of 3% to those of the nonactivated specimens. Therefore, it was confirmed that the effect of Fe-SMA activation on the ultimate strength of specimens was negligible.

A bio-inspired robotic fish utilizes the snap-through buckling of its spine to generate accelerations of more than 20g

Inspired by the fastest observed live fishes, we have designed, built and tested a robotic fish that emulates the fast-start maneuver of these fishes and generates acceleration and velocity magnitudes comparable to those of the live fishes within the same time scale. We have designed the robotic fish such that it uses the snap-through bucking of its spine to generate the fast-start response. We have used a dynamic snap-through buckling model and a series of experiments on a beam under snap-through buckling to describe the robotic fish’s motion. Our under-actuated robot relies on passive dynamics of a continuous beam to generate organic waveforms. In its transient fast-start maneuver, our robotic fish produces mode shapes very similar to those observed in live fishes, by going through a snap-through bifurcation. We have also used a nonlinear structural model subjected to a non-conservative eccentric compressive force, which is constrained to act tangential to the structure at all times, coupled with a simple fluid dynamic model to approximate the transient behavior of the robot. We relate the numerical results from our nonlinear model to the dynamics observed in the live system proposing an updated kinematic model to understand the mode shapes observed in the fast-start maneuver of the live fishes. We also report on deploying the robotic fish in a river.

Effects of out-of-plane eccentric axial compression on in-plane hysteretic behavior of SC walls

Steel-concrete composite (SC) walls may be subjected to simultaneous in-plane (IP) and out-of-plane (OOP) loads in some civil and industrial buildings. However, there are few studies and no design guideline for SC walls under such load conditions. In this paper, four SC wall specimens were designed and tested to investigate the effects of OOP loading on IP hysteretic behavior. During the experiment, a constant eccentric axial compressive force was applied to the top of the specimen, which generated an OOP bending moment. The variables considered in the experiments were the eccentric distance and the axial compression ratio. All four specimens demonstrated characteristics of the flexural failure mode. The IP bearing capacity and deformation capacity of the specimens were significantly reduced due to the influence of OOP loading. A nonlinear analysis program based on fiber model method was presented to calculate the IP and OOP bearing capacity under different load combinations. An interaction surface, N-Mx-My, and a simplified formula were developed as a simplistic tool to consider simultaneous IP and OOP bending moment.

Load carrying ability and optimal characteristics of the roof slab made of profiled sheeting

The subject of the study is the roof slabs, made of profiled sheetings, supported by bottom truss systems. The profiled sheet, being the upper belt of these structures, experiences longitudinal-transverse bending under the distributed transverse load and a longitudinal eccentric compressive force. Analytical and numerical studies determined the stress-strain state of the profiled sheeting. The dependences of the limiting value of the distributed load on the compressive longitudinal force and the eccentricity of its application are revealed. A technique for optimizing the design parameters of roof slabs have been developed. The studied roof slabs made of profiled sheeting, supported by a truss system, have a rather complicated design with many parameters, on which the performance criteria depend. Studies of the ties between these parameters are quite laborious. Therefore, it is not possible to solve the problems of optimizing these structures by known analytical and numerical methods. To find the rational parameters of the studied slabs, we used the method of phased numerical experiments using simplex optimization. Using this technique, the optimal structural parameters of the slabs with spans of 6-12 m were determined for a given efficiency criterion.

Pinned - Fixed Beam - Column Resistance Verification According to European Standards

Abstract Verification of beam-column resistance can be accomplished according to design approaches given in EN 1993-1-1 [1]. These approaches are derived from verification of single span beam with pinned end conditions subjected to compression and bending moments. In the case of different end conditions, the application of those approaches is not so accurate and more difficult. Therefore, the comparison of verification according to above standard EN 1993-1-1 [1] as well as EN 1999-1-1 [2] to results of experimental analyses of beam-columns having pinned-fixed end conditions subjected to an eccentric compressive force simulating the behaviour of columns integrated into frames is presented in this paper.

A students' challenge for the estimation of the maximum compressive load of masonry prisms / Studentenwettbewerb zur Ermittlung der maximalen Druckfestigkeit von Mauerwerksprismen

AbstractThe paper presents the “IMC Students' Challenge” competition held in 2014, during the 9th International Masonry Conference, in Guimarães. The objective of the competition was to predict the maximum compressive load of two masonry prisms built of solid bricks, and of hollow blocks, with mortar joints. To increase the complexity of the problem, all prisms were tested under eccentric load. The students, who enthusiastically participated in the final laboratory tests, presented different approaches to estimate the maximum eccentric compressive force on masonry prisms. The challenge was a great experience, not only for students and conference participants, but also for sponsors and organizers.

The Ultimate Load-Carrying Capacity of a Thin-Walled Shuttle Cylinder Structure with Cracks Under Eccentric Compressive Force

The Ultimate Load-Carrying Capacity of a Thin-Walled Shuttle Cylinder Structure with Cracks Under Eccentric Compressive Force

Structural performance of a large-scale space frame assembled using pultruded GFRP composites

A space frame structure assembled by pultruded circular hollow section (CHS) GFRP members is presented. This large-scale structure was built with the span length of 8m, width of 1.6m and depth of 1.13m, but weighing only 773kgf. The structural details and design considerations are developed for potential pedestrian bridge applications and may be further extended for roof structures with pedestrian activity. Experiments were conducted under three-point bending to understand the structural stiffness, load-carrying capacity, and failure modes. The structure showed satisfactory overall stiffness and load-carrying capacity in terms of potential pedestrian bridge applications. It was further found that the second order bending of critical compressive members might cause large nonlinear deformation of the overall structure. This is because bending of the critical compressive members resulted in a decrease in structural stiffness, with maintenance of the load applied and increase of deformation until the ultimate material failure. The structural behavior can be well described by FE modeling considering realistic initial imperfections such as out-of straightness, eccentricity of members, and additional eccentric compressive forces.

Strength of cold formed battened columns subjected to eccentric axial compressive force

The strength of a battened beam-column composed of four slender cold formed angles is mainly governed by the local buckling of its elements as well as the overall buckling of the column. The local buckling mode is mainly affected by local slenderness ratio of one angle (between batten plates). Overall buckling mode is mainly affected by overall member slenderness ratio as well as angle legs width to thickness ratio. Members' failure modes occur by local buckling and yielding at short lengths, and by local flexural buckling at intermediate and flexural at long lengths. In the present study, the behavior of bi-axially loaded battened beam-columns composed of four equal cold formed slender angles is investigated. A nonlinear finite element model was developed to study the effect of the aforementioned factors on the ultimate capacity of members. Geometrical and material nonlinearities were considered in the model. A parametric study was performed on a group of battened beam-columns with variable angle legs having different outstanding leg width–thickness ratios, angle local slenderness ratios, and column overall slenderness ratios. The axial–bending interaction curves are presented for short, medium and long beam-columns having two different square cross sections. These interaction curves were compared with different code rules. These design rules have been shown to be reliable using reliability analysis.

Local autograft retrieval from a cervical vertebral body: biomechanical consequences

To avoid the cost of bone graft substitutes and the morbidity of iliac crest bone graft retrieval, locally harvested vertebral body bone has been used to fill interbody cages. When marginal hypertrophic osteophytes are used, there is little impact on the adjacent vertebrae, but when cancellous bone is removed from the central part of the vertebral body, it is not clear how significantly this procedure weakens the vertebra. The objective of this study was to investigate the immediate mechanical response of the cervical spine after removing bone from the central vertebral body. Fourteen cervical functional spinal units (FSUs) (mean age 73.3 years, range 63-90 years) were used. For each FSU, bone mineral density (BMD) was determined using lateral-view dual-energy x-ray absorptiometry studies. The FSUs were assigned to 1 of 2 groups (test group or control group) with an equal distribution of BMD. All specimens received a cage placed into the cleaned disc space. The specimens from the test group had a 5-mm-diameter bone plug removed from the vertebral bodies superior and inferior to the cage-fitted disc. The specimens were loaded in flexion-compression until failure via an eccentric compressive force at 0.25 mm/second. The yield compression strength was 1149 ± 523 N for the test group and 1647 ± 962 N for the control group (p = 0.25). The ultimate compression strength was 1699 ± 498 N for the test group and 2450 N ± 835 N for the control group (p = 0.06). Force at 4 mm displacement was 1064 N for the test group and 1574 N for the control group (p = 0.15). Displacement at yield compression strength was 4.4 mm for the test group and 4.2 mm for the control group (p = 0.78). There was no significant intergroup difference for any of the studied parameters. There does not appear to be a significant early biomechanical weakening of adjacent vertebrae caused by aforementioned technique of local bone harvest.

Vibration of viscoelastic beams subjected to an eccentric compressive force and a concentrated moving harmonic force

The problem of lateral vibration of a beam subjected to an eccentric compressive force and a harmonically varying transverse concentrated moving force is analyzed within the framework of the Bernoulli–Euler beam theory. The Lagrange equations are used to examine the free vibration characteristics of an axially loaded beam and the dynamic response of a beam subjected to an eccentric compressive force and a moving harmonic concentrated force. The constraint conditions of supports are taken into account by using the Lagrange multipliers. In the study, trial function denoting the deflection of the beam is expressed in a polynomial form. By using the Lagrange equations, the problem is reduced to the solution of a system of algebraic equations. Results of numerical simulations are presented for various combinations of the value of the eccentricity, the eccentric compressive force, excitation frequency and the constant velocity of the transverse moving harmonic force. Convergence studies are made. The validity of the obtained results is demonstrated by comparing them with exact solutions based on the Bernoulli–Euler beam theory obtained for the special cases of the investigated problem.

Softening behaviour of concrete prisms under eccentric compressive forces

Softening behaviour of concrete prisms under eccentric compressive forces

Softening behaviour of concrete prisms under eccentric compressive forces

The behaviour of reinforced concrete elements has been analysed by means of tests on prisms subjected to normal forces with different degrees of eccentricity. The tests were performed in strain-controlled conditions until failure. Along the fibres running parallel to the axis of the specimen, stress–strain curves are seen to be homogeneous before peak load is reached, whereas the deformations measured in the softening branch are more scattered and are found to depend on gauge length due to strain localisation within the compressive zone. This behaviour is also verified for specimens subjected to centred compression and makes it difficult to define the stress–strain plot in the softening branch. By assuming a σ–ε constitutive law based on the deformation measured over a predetermined gauge length in centred compression tests, the results of tests conducted with eccentric loads were compared to those obtained under the commonly accepted assumption of plane section remaining plane and the possibility of stress integration. In this case, all specimens were of the same size and the measurements were performed over the same gauge length. The maximum loads obtained experimentally for each test were seen to be higher than the theoretical loads and to increase in percentage with increasing eccentricity. Since increasing eccentricity corresponds to a decrease in the size of the compression zone, it can be inferred that the scale effect on the compressive strength of concrete is a function of the height of the compression zone.

Mechanical behavior of the female sacroiliac joint and influence of the anterior and posterior sacroiliac ligaments under sagittal loads

Objective. The purpose of this study was to examine the mechanical behaviour of the female sacroiliac joint and the effects of its two major ligaments to joint stability. Design. A cadaveric model was used to study the mechanical behaviour of the sacroiliac joints, and sequential dissection was performed to examine the contribution of the anterior and posterior sacroiliac ligaments in joint stability. Background. Instability of the sacroiliac joints have been suspected as a possible cause of low back pain. Despite several investigations on joint anatomy and joint mobility, its stabilising mechanism is still not clear. Methods. Four fresh cadaveric specimens of the female pelvis were tested on an Instron material testing machine. Eccentric compressive force of 60% of the subject's body weight was applied to the pelvis through the sacrum. Relative three-dimensional six-degree-of-freedom movement at the left sacroiliac joints was recorded with a specially designed motion tracking device. The device has an accuracy of 0.01 mm and is compact enough to be mounted across the joint. The test was repeated after sequential selective dissection of the bilateral anterior, and then posterior sacroiliac ligaments. Results. Rotation up to 1.2 ° and translation up to 0.9 mm were measured from the intact specimens. Lateral rotation, which tended to open the top portion of the joint, and sacral nutation were the primary rotations. On average, the rotation angles increased 10% when either the anterior or posterior ligaments were cut, and 30% when both ligaments were cut. Conclusions. Lateral rotation and nutation rotation of the sacrum were found to be the predominant motion, though the values were limited to less than 1.2 °. Both the anterior and posterior sacroiliac ligaments were found to play an important role in resisting rotations at the joints.

Stability of Masonry Piers under Their Own Weight and Eccentric Load

The stability of masonry piers subjected to their own weight and to eccentric compressive force at the top is analyzed. Prismatic fixed free-ended columns are examined, considering no tension material having linear behavior in compression. The column is ideally divided into a number of elements that is unknown a priori, all of the same length. Along each of them, the curvature corresponding to the equilibrium condition is assumed to be constant. For each assigned value of rotation of the free end this hypothesis makes it possible to express in recursion form the rotation of the cross sections characterizing the model, which obviously decreases with an increase in the number of elements considered starting from the upper cross section. The unknown length of the column corresponding to an assigned load condition is deduced from the number of elements needed to obtain a zero value of rotation, because the latter condition characterizes the section at the base. Applying the procedure with variation in the value of rotation of the free end, stability domains are deduced for different ratios between weight and concentrated load. The results, obtained in dimensionless form, show the optimum value of this ratio for a given eccentricity value.

Composite columns of double-skinned shells

Abstract Tests were carried out on 12 hollow circular columns of composite shell walls with a view to investigating their behaviour when subjected to eccentric end compressive forces. The cross-section of the columns consists of two concentric thin steel shells, and the ring-shaped space between then is filled with either grout or microconcrete. The columns have a buckling length of about 4 m, and the results of the tests are reported here. The experimental failure loads are compared with the predictions of the British Standard BS 5400, and also with the results of a finite element analysis. The test results reported here confirm the viability of such novel columns as a practical solution to unusual situations. The results also emphasize the need for experimental investigations before the application of the British Standard BS 5400 to the design of composite columns of unusual cross-sections.

Safety Condition Of Masonry Columns Subjected ToHorizontal Forces: Effects Of Material NonlinearityAnd Cyclic Loading

A lot of historical masonry buildings are characterized by the presence of slender bearing structures (columns or walls) which exhibit in the main flexural rather than shear behaviour when subjected to a seismic excitation. The equilibrium limit state of such resisting elements is investigated here by the following phases of study: choice of a suitable a-e constitutive law able to represent experimental results related to different masonry kinds; consequent modelling of the moment-curvature laws and definition of the equilibrium domain of a column section, assuming the normal compressive load to be constant and the bending moment to be monotonically increasing; limit analysis of the deflected column by modelling the earthquake actions by equivalent horizontal static forces and by including the largedeflection effects; comparison between the results of the previous analyses and the corresponding results derived assuming the horizontal forces to be cyclically acting. Each analysis step is carried out in dimensionless terms so that the results presented in this paper and the solution procedures proposed can be referred to a large class of masonry structures. 1 Analysis of section subjected to static load 1.1 Constitutive law Most studies concerning the flexural behaviour of masonry columns subjected to eccentric compressive forces are based on the assumption that the material has no tensile strength and is affected by a linear infinitely elastic a e law in compression. The first assumption is supported by experimental results which reveal tensile strength values negligible with respect to the strength in compression. The second assumption proves to be acceptable when the maximum stress which a generic column section reaches is fairly small, i.e. when Transactions on the Built Environment vol 26, © 1997 WIT Press, www.witpress.com, ISSN 1743-3509 398 Structural Studies, Repairs and Maintenance of Historical Buildings column collapse occurs because of instability, before the material's bearing capacity resources are fully involved. This circumstance is typical of very slender columns subjected to a concentrated compressive load acting eccentrically at the top, and in this case the critical load can be evaluated analytically (Frish-Fay [1]). If the first-order bending moment is produced by horizontal actions and/or the column slenderness is not very high, the material cannot be characterized adequately only by means of the tangent modulus of elasticity at the origin of the a 8 law, and, consequently, a more realistic constitutive model of the behaviour in compression has to be assumed. In this study the analytical relationship proposed by Shah et al. (1966) (see Ref [2]) to model the concrete behaviour is utilized with suitable specializations. The original form of this law is expressed by

Stability of a Bar Under Eccentric Follower Force

Uniform cantilevered bar subject to eccentric compressive follower force, considering warping rigidity, bending-torsional flutter and stability