Axial Force Loading Research Articles

Experimental and Analytical Analysis of RC Frames Strengthened Using RC External Shear Walls

In this study, we have investigated the application of an external RC shear wall as a method of improving the performance of reinforced concrete (RC) frames in an earthquake. We produced a series of eight RC frames, each of which was modeled at a 1/3 scale with two floors and two spans. These frames were of the same size and had design and construction deficiencies commonly encountered in the RC buildings in Turkey. We tested four of the eight frames without any strengthening, under reversed cyclic lateral loadings resembling earthquake loads. The remaining four frames we tested under the same conditions after strengthening them with RC external shear walls. We arranged the axial force loads applied to the columns of the test models in two different ways to result in tensile and compression failure. The test results were analyzed on the basis of a comparison using static push over analysis. The results of the experimental tests and analytical studies showed that the RC external shear wall improved the seismic character of the existing RC frame as much as RC infill walls, therefore this method can be used as an alternative strengthening method. Also, the method provides effective, practical and economical strengthening that minimizes the need for additional works and does not restrict the use of the RC building.

Biomechanical analysis of four different fixations for the posterolateral shearing tibial plateau fracture

The posterolateral shearing tibial plateau fracture is uncommon in the literature, however with the increased usage of computer tomography (CT), the incidence of these fractures is no longer as low as previously thought. Few studies have concentrated on this fracture, least of all using a biomechanical model. The purpose of this study was to compare and analyse the biomechanical characteristics of four different types of internal fixation to stabilise the posterolateral shearing tibial plateau fracture. Forty synthetic tibiae (Synbone, right) simulated the posterolateral shearing fracture models and these were randomly assigned into four groups; Group A was fixed with two anterolateral lag screws, Group B with an anteromedial Limited Contact Dynamic Compression Plate (LC-DCP), Group C with a lateral locking plate, and Group D with a posterolateral buttress plate. Vertical displacement of the posterolateral fragment was measured using three different strengths of axial loading force, and finally loaded until fixation failure. It was concluded that the posterolateral buttress plate is biomechanically the strongest fixation method for the posterolateral shearing tibial plateau fracture.

Classic Axial Load Injuries to the Upper Extremity

OPEN ACCESSFebruary 14, 2011Classic Axial Load Injuries to the Upper Extremity Matthew Levine, MD, Nathan Sandalow, MD Matthew Levine, MD Northwestern University The Feinberg School of Medicine Google Scholar More articles by this author , Nathan Sandalow, MD Long Island Jewish Medical Center Google Scholar More articles by this author https://doi.org/10.15766/mep_2374-8265.8325 SectionsAbout ToolsDownload Citations ShareFacebookTwitterEmail Abstract Introduction: Classic axial load injuries to the upper extremity (many of which are referred to as “falling on the outstretched arm” (FOOSH) are a frequent presentation in emergency medicine. Axial load can lead to classic patterns of injury from the hand to the shoulder. Demonstration of competency in assessing these injuries is essential in the practice of emergency medicine. This resource describes the classic axial load injuries of the upper extremity. Methods: This resource contains two PowerPoint presentations that use pictures, radiology images, and diagrams to demonstrate upper extremity injuries. One presentation focuses on classic injuries of these extremities, the other on load injuries. Results: For the last 8 years the primary author has been lecturing to fourth-year medical students on a monthly basis as part of orientation for their required emergency medicine clerkship. The lecture has been highly rated in student evaluations perennially. One of the students (the co-author) appreciated the lecture so much that, as part of a project for an anatomy elective, he collaborated with the primary author to apply his computer animation skills to enhance the orientation content. Student reviews have been overwhelmingly positive and they have been anecdotally observed applying the knowledge during clinical care in the emergency department. Discussion: Classic axial load injuries to the upper extremity are a frequent presentation in emergency medicine. These injuries are illustrated in a unique way using animations to help the learner truly understand the injury beyond simply the radiographic abnormalities. Educational Objectives By the end of this session, facilitators will be able to: Describe the classic injuries sustained from an axial load force applied to the upper extremity.Depict these injuries using animation schemes so that the learner understands how the mechanism results in the injury pattern to enhance retention.Teach high-yield pearls in the diagnosis and management of these injuries. Sign up for the latest publications from MedEdPORTAL Add your email below FILES INCLUDEDReferencesRelatedDetails FILES INCLUDED Included in this publication: Load Injuries to the Upper Extremity.pptx Classic Injuries to the Upper Extremity.pptx To view all publication components, extract (i.e., unzip) them from the downloaded .zip file. Download editor’s noteThis publication may contain technology or a display format that is no longer in use. CitationLevine M, Sandalow N. Classic Axial Load Injuries to the Upper Extremity. MedEdPORTAL. 2011;7:8325. https://doi.org/10.15766/mep_2374-8265.8325 Copyright & Permissions© 2011 Levine and Sandalow. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-No Derivatives license.KeywordsAxial LoadArm InjuriesFOOSHUpper Extremity Injury Disclosures None to report. Funding/Support None to report. Loading ...

Nonlinear vibration analysis of an axially moving drillstring system with time dependent axial load and axial velocity in inclined well

Abstract In this paper a nonlinear model was developed for a drillstring system in deviated well with axially moving motion and axial loading, using the perturbation techniques. The drillstring was considered as a simply supported axially moving rotor. Governing equations of motion were obtained based on Hamilton's principle and method of multiple scales was employed to solve the nonlinear motion equations in order to obtain the steady state response and stability region of the system. Then the effects of rotating speed, axial compression load, imbalance mass and nonlinear fluid force on the drillstring responses were investigated in detail and nonlinear natural frequencies and their corresponding mode shapes were presented. Analytical and numerical results reveal the rich and interesting nonlinear phenomena such as primary and parametric resonance that is being investigated for the first time in this study on the nonlinear vibration of the drillstring system. Finally in effort to validate the theoretical approach employed in this study, the numerical solutions obtained here were compared with a set of existing experimental data.

Spontaneous C1 anterior arch fracture as a postoperative complication of foramen magnum decompression for Chiari malformation type 1

Background:C1 fracture accounts for 2% of all spinal column injuries and 10% of cervical spine fractures, and is most frequently caused by motor vehicle accidents and falls. We present a rare case of C1 anterior arch fracture following standard foramen magnum decompression for Chiari malformation type 1.Case Description:A 63-year-old man underwent standard foramen magnum decompression (suboccipital craniectomy and C1 laminectomy) under a diagnosis of Chiari malformation type 1 with syringomyelia in June 2009. The postoperative course was uneventful until the patient noticed progressive posterior cervical pain 5 months after the operation. Computed tomography of the upper cervical spine obtained 7 months after the operation revealed left C1 anterior arch fracture. The patient was referred to our hospital at the end of January 2010 and C1–C2 posterior fusion with C1 lateral mass screws and C2 laminar screws was carried out in March 2010. Complete pain relief was achieved immediately after the second operation, and the patient resumed his daily activities.Conclusion:Anterior atlas fracture following foramen magnum decompression for Chiari malformation type 1 is very rare, but C1 laminectomy carries the risk of anterior arch fracture. Neurosurgeons should recognize that fracture of the atlas, which commonly results from an axial loading force, can occur in the postoperative period in patients with Chiari malformation.

In Brief: Lisfranc Fracture Dislocations

Lisfranc injuries are injuries to the tarsometatarsal joints which separate the midfoot from the forefoot. These injuries can be purely ligamentous or involve the osseous structures in the foot, in which case they are classified as fracture-dislocations. They are usually high-energy injuries and occur most often when an axial load or rotational force is brought on a plantar-flexed foot (Fig. 1). Less commonly, a direct blow to the midfoot can cause disruption of the joint complex. Fig. 1A−D (A) AP and (B) lateral radiographs are shown for a patient with a Lisfranc fracture-dislocation. There is lateral and dorsal displacement of the base of the second metatarsal with respect to the middle cuneiform. Postoperative (C) AP and (D) lateral radiographs ... Injury to the Lisfranc joint commonly affects males, frequently during the third decade of life, and often as a result of a fall from a height or a motor vehicle accident [2]. The majority of patients who sustain such an injury are polytraumatized, therefore, a high index of suspicion must be maintained so that subtle injuries are not missed [16].

A new design method for calculating critical temperatures of restrained steel column in fire

This paper presents a new simplified design method for calculating the buckling- and failure-temperature of uniformly heated, axially restrained steel column subjected to axial compression load or combined axial compression force and bending moment in fire. Here the term “buckling temperature” refers to the temperature at which the restrained column loses temporary stability due to increased axial compression load, while “failure temperature” refers to the temperature at which the axial load in column returns to the initial level. For a restrained column under axial load, this paper presents effects of three different column design parameters, including the axial restraint stiffness, the initial axial load and the column slenderness, on the column buckling- and failure-temperature using a calibrated finite element method model. Two additional parameters are analyzed, including the bending moment ratio and the end moment ratio, for a restrained column under combined axial force and bending moment. To derive design calculation equations, regression analyses were carried out to express the reduction in column buckling- and failure-temperature, from that of the column without axial restraint, as functions of the aforementioned column design parameters. The accuracy of these design equations are then assessed by comparison between their predictions and finite element predictions.

The Effect of Medial Versus Lateral Meniscectomy on the Stability of the Anterior Cruciate Ligament-Deficient Knee

Background: The pivot shift is a dynamic test of knee stability that involves a pathologic, multiplanar motion path elicited by a combination of axial load and valgus force during a knee flexion from an extended position. Purpose: To assess the stabilizing effect of the medial and lateral meniscus on anterior cruciate ligament-deficient (ACL-D) knees during the pivot shift examination. Study Design: Controlled laboratory study. Methods: A Lachman and a mechanized pivot shift test were performed on 16 fresh-frozen cadaveric hip-to-toe lower extremity specimens. The knee was tested intact, ACL-D, and after sectioning the medial meniscus (ACL/MM-D; n = 8), lateral meniscus (ACL/LM-D; n = 8), and both (ACL/LM/MM-D; n = 16). A navigation system recorded the resultant anterior tibial translations (ATTs). For statistical analysis an analysis of variance was used; significance was set at P < .05. Results: The ATT significantly increased in the ACL-D knee after lateral meniscectomy (ACL/LM-D; P < .05) during the pivot shift maneuver. In the lateral compartment of the knee, ATT in the ACL-D knee increased by 6 mm after lateral meniscectomy during the pivot shift (16.6 ± 6.0 vs 10.5 ± 3.5 mm, P < .01 for ACL/LM out vs ACL out). Medial meniscectomy, conversely, had no significant effect on ATT in the ACL-D knee during pivot shift examination (P > .05). With standardized Lachman examination, however, ATT significantly increased after medial but not lateral meniscectomy compared with the ACL-D knee (P < .001). Conclusion: Although the medial meniscus functions as a critical secondary stabilizer to anteriorly directed forces on the tibia during a Lachman examination, the lateral meniscus appears to be a more important restraint to anterior tibial translation during combined valgus and rotatory loads applied during a pivoting maneuver. Clinical Relevance: This model may have implications in the evaluation of surgical reconstruction procedures in complex knee injuries.

The Effect of Systemic Nicotine on Osseointegration of Titanium Implants in the Rat Femur

The purpose of this study was to determine whether high levels of plasma nicotine, delivered via subcutaneously placed mini-osmotic pumps, had an effect on bone development and osseointegration of a titanium implant in rat femurs in both the short and long term. In this study, we hypothesized that systemic nicotine may not affect bone development, but may affect osseointegration in both the short and long term. Thirty rats were assigned to 4 groups. Group 1 (n = 10) was subdivided into 2 groups, which both received nicotine during the duration of the experiment. Half of the group (n = 5) was sacrificed at 2 weeks after implant placement, and the other half (n = 5) was sacrificed at 4 weeks after implant placement. Group 2 (n = 10) was treated identically; however, this group was given saline placebo rather than nicotine. Nicotine/saline was administered via subcutaneous mini-osmotic pumps. Serum analysis was assessed biweekly and weight was assessed weekly. Implant placement consisted of mini-implant placement in the femur of the rats under general anesthesia. After sacrifice, the femurs were harvested and analyzed. Biomechanical push-in test was used to determine the degree of osseointegration by evaluating the breakpoint load. Micro-CT was performed on the femurs of the remaining 10 rats to determine the bone density and architecture. Micro-CT showed no significant difference in bone morphometric analysis. Push-in test showed significant difference in axial load force required to dislodge the implant between the nicotine-treated and control rats both at 2 and at 4 weeks after implant placement. The evidence indicates that while there was no significant difference in bone development and remodeling with exposure to systemic nicotine, there was a significant difference in bone wound healing, specifically with the osseointegration of titanium implants at both 2 and 4 weeks after implant placement. In conclusion, systemic nicotine may have a significant impact on the osseointegration of implants in the rat femur. Additional studies need to be conducted to further understand the specific way in which nicotine adversely affects wound healing on the molecular level.

Skeletal trauma in children: what is different?

Shoulder injuries are very common in all pediatric age groups. Very often, the shoulder is hit directly, or one falls on the shoulder so that it absorbs forces directly. These forces also usually are transmitted to the clavicle. This is an important point to remember, especially in terms of what happened to our patient. Indeed, our patient was tender over the clavicle; but, it is interesting that, very often, clinicians fail to palpate the clavicle with shoulder injuries, and yet this is very important. Why is this important? It is important because the clavicle often is the bone to take the brunt of the traumatic force. In terms of clavicular injuries, one of the first considerations is the most common overt or greenstick fracture of the clavicle. Another common consideration is an acromioclavicular separation. In other cases, there may be dislocation of the clavicle medially; but probably more common than all of these manifestations, except for the overt fracture of the clavicle, is the so-called plastic or bending fracture of the clavicle. This fracture is very common throughout the pediatric age range, including the adolescent. What happens in these cases is that the axial load forces exerted on the shoulder are transmitted to the clavicle and the clavicle bends. In some cases, it bends enough to produce a greenstick fracture (cousin of the plastic bending fracture); if one sees the fracture, there is no problem with diagnosis; but if no fracture line is seen, it is interesting how often the fact that the clavicle is bent is overlooked. In terms of the clavicle in almost every normal individual, with well-positioned radiographs, the clavicles look exactly the same. In this regard, however, it is best that the clavicles both be included on the same imaging study and not imaged separately. It is much more difficult to detect subtle bending fractures under the latter circumstance. On the other hand, when both clavicles and shoulders are included on the same image, accomplishing a diagnosis of a bending fracture is much easier. In this regard, in our patient, one should note that there is a distinct bend of the lateral end of the left clavicle as compared to the normal right clavicle (Fig. 2). This represents a plastic bending fracture. Emerg Radiol (2009) 16:35–36 DOI 10.1007/s10140-008-0718-1

Seismic behavior of wide-flange steel column with confined potential plastic hinge

This experimental project investigates and validates an innovative method to confine the potential plastic hinge zone of hot-rolled H-shape (or wide-flange) steel column for improved seismic behavior. Based on fundamental mechanics, the concept aims at controlling the local buckling of the flange and web elements of the H-shape steel in the potential plastic hinge region of a column. In the experimental program, six model columns were tested under constant axial load and cyclic lateral forces acting in either the weak or the strong axes. Compared with the conventional H-shape steel model columns, the model columns with their potential plastic hinge zone confined by either steel strips or reinforced concrete cover, exhibited excellent seismic performance with large ductility. Analytical efforts to compare with the test results were also made using simple moment-curvature analysis.

Biomechanical interactions in tooth–implant‐supported fixed partial dentures with variations in the number of splinted teeth and connector type: a finite element analysis

The aim of this study was to investigate the biomechanical interactions in tooth-implant-supported fixed partial dentures (FPDs) under several loading conditions with different numbers of splinted teeth and connector types (rigid and non-rigid) by adopting the three-dimensional (3D) non-linear finite element (FE) approach. A 3D FE FPD model was constructed containing one Frialit-2 implant in the mandibular second-molar region splinted to the first and second premolars. Frictional contact elements were used to simulate realistic interface conditions within the implant system and the non-rigid connector function. The main effects for each level of the three investigated factors (loading condition, number of splinted teeth and connector type) in terms of the stress values and dissimilar mobility of the natural teeth and implant were computed for all models. The results indicated that load condition was the main factor affecting the stress developed in the implant, bone and prosthesis when comparing the type of connector and the number of splinted teeth. The stress values were significantly reduced in centric or lateral contact situations once the occlusal forces on the pontic were decreased. However, the prosthesis stress for the non-rigid connections was increased more than 3.4-fold relative to the rigid connections. Moreover, the average tooth-to-implant displacement ratios (R(TID)) with a non-rigid connection were obviously larger than those for rigid connections under axial loading forces. Adding an extra tooth to support a three-unit tooth-implant FPD only exploited its function when the prosthesis withstood lateral occlusal forces. The load condition is the main factor affecting stress distribution in different components (bone, prosthesis and implant) of tooth-implant-supported FPDs. Minimizing the occlusal loading force on the pontic area through selective grinding procedures could reduce the stress values obviously. A non-rigid connector may more efficiently compensate for the dissimilar mobility between the implant and natural teeth under axial loading forces but with the risk of increasing unfavorable stresses in the prosthesis.

Ductility of Ultra High-Strength Concrete Tied Columns under Combined Axial Load and Lateral Force

Ductility of Ultra High-Strength Concrete Tied Columns under Combined Axial Load and Lateral Force

Internal Fixation of Dorsally Displaced Fractures of the Distal Part of the Radius

Volar plate fixation with use of either a locking plate or a neutralization plate has become increasingly popular among surgeons for the treatment of dorsally comminuted extra-articular distal radial fractures. The purpose of the present study was to compare the relative stability of five distal radial plates (four volar and one dorsal), all of which are commonly used for the treatment of dorsally comminuted extra-articular distal radial fractures, under loading conditions simulating the physiologic forces that are experienced during early active rehabilitation. With use of a previously validated Sawbones fracture model, a dorsally comminuted extra-articular distal radial fracture was created. The fracture fixation stability of four volar plates (an AO T-plate, an AO 3.5-mm small-fragment plate, an AO 3.5-mm small-fragment locking plate, and the Hand Innovations DVR locking plate) were compared under axial compression loading and dorsal and volar bending simulating the in vivo stresses that are generated at the fracture site during early unopposed active motion of the wrist and digits. A single dorsal plate (an AO pi plate) was used for comparison, with and without simulated volar cortical comminution. The construct stiffness was measured to assess the resistance to fracture gap motion, and comparisons were made among the implants. The volar AO locking and DVR plates had greater resistance to fracture gap motion (greater stiffness) compared with the volar AO nonlocking and AO T-plates under axial and dorsal loading conditions (p < 0.01), with no significant difference between the AO volar locking and DVR plates. The volar AO locking plate had greater resistance to fracture gap motion than did the volar AO nonlocking plate under axial loading and dorsal bending forces (p < 0.01). The dorsal pi plate had the greatest resistance to fracture gap motion under axial loading and volar and dorsal bending forces (p < 0.01). However, the pi plate was significantly less stable to axial load and dorsal bending forces when the volar cortex was comminuted (p < 0.01). In this model of dorsally comminuted extra-articular distal radial fractures, dorsal pi-plate fixation demonstrated better resistance to fracture gap motion than did the four types of volar plate fixation. The AO volar locking and DVR plates conferred the greatest resistance to fracture gap motion among the four volar plates tested. Volar locking technology conferred a significant increase in resistance to fracture gap motion as compared with nonlocking plate technology.

Segmental spinal dysgenesis: report of four cases and proposed management strategy

Segmental spinal dysgenesis, a rare developmental malformation, usually manifests during pregnancy or at birth. The resulting gross spinal instability necessitates spinal stabilization, which is inherently challenging in neonates. We report four cases of segmental dysgenesis: three in the thoracolumbar region and one at the cervicothoracic junction. The latter was maintained in a custom orthosis that restricted all craniospinal motion while allowing routine care. Two neonates underwent surgical stabilization. The fourth patient will remain in a brace until 12-14 months old when fusion is planned. Fusion with rib autografts failed in the two neonates. One patient has been followed for 13 years and is paraplegic. The second patient was lost to follow up. The patient with the cervicothoracic dysgenesis maintained normal neurologic function until his death at 8 months of cardiac failure. The fourth patient is 12 months old and has been maintained in a thoracolumbar orthosis with stable neurologic function. Several factors contribute to the challenge of creating a stable fusion in neonates. Incomplete ossification of the vertebral bodies and poor results with allograft materials restrict fusion options. Neurologic deficits often prevent ambulation and decrease the axial-loading forces that enhance fusion. To allow children to grow and develop, we advocate rigid spinal immobilization for 12-18 months before spinal fusion (preferably, rib or fibular autograft). Given the already narrow spinal canal, the use of instrumentation is controversial. We advocate the use of instrumentation in infants only when a sound construct cannot be obtained with the graft alone.

Seismic behavior of confined square CFT columns

The failure of conventional concrete filled tubes (CFT) under seismic loading is typically governed by the inelastic buckling and low cycle fatigue rupture. The second author has proposed to use additional confinement to control or delay the inelastic buckling of the steel tube at the potential plastic hinge zones of CFT members. Following the success of the previous studies on confined concrete filled tubes (CCFT) with circular sections, this paper reports the experimental results on square CCFT columns. One conventional CFT and five CCFT model columns were tested under constant axial load and cyclic lateral forces. Test results validated the concept of CCFT for square sections. Compared with the conventional CFT column model, the CCFT columns exhibited significantly improved seismic performance with large ductility. A design method for the additional confinement to the plastic hinge region was also developed and validated.

Vibration analysis of a magneto-elastic beam with general boundary conditions subjected to axial load and external force

In this study, the interactive behaviors among transverse magnetic fields, axial loads and external force of a magneto-elastic beam with general boundary conditions are investigated. The axial force and transverse magnetic force are assumed to be periodic with respect to time and two specified frequencies, one for axial force and the other for oscillating transverse magnetic field, are applied to the whole system. The equation of motion for the physical model is derived by using the Hamilton's principle and the vibration analysis is performed by employing the characteristic orthogonal polynomials as well as the Galerkin's method. The displacement of the beam with the effect of the magnetic force, axial force and spring force are determined from the modal equations by using the Runge–Kutta method. Based on the present study, we can conclude that the effect of the magnetic field not only reduces the deflection but also decreases the natural frequencies of the system, also it should be noted that the specified beam model can be adopted to simulate several structures in mechanical, civil and electronic engineering.

Dynamics of Initial Penetration in Drilling: Part 2—Motion Models for Drill Skidding and Wandering With Experimental Verification

This part of the paper is aimed at the development of models for the drill tip’s transverse and angular motions, the definition of models for establishing the drilled hole’s profile and, by combining these results with the dynamic force models of Part 1, the formulation of the complete model for drill skidding and wandering. An experimental verification of the models concludes the paper. For the development of the drill motion models the drill is simplified as a pretwisted beam subjected to a compressive axial load and radial forces acting on its tip. The governing equations are developed using Hamilton’s principle. Subsequently, the weak form of the governing equation is formulated to facilitate their solution by the finite element method. The corresponding boundary conditions for the motion model are also defined for three drilling phase, i.e., drill skidding, drill wandering and stabilized drilling. Based on the drill tip’s wandering locus and drill rotation, a mathematical model for describing the drilled hole’s profile is developed.

Vibration analysis of edge-cracked beam on elastic foundation with axial loading using the differential quadrature method

The eigenvalue problems of clamped-free and hinged–hinged Bernoulli–Euler beams on elastic foundation with a single edge crack, axial loading and excitation force were numerically formulated using the differential quadrature method (DQM). Appropriate boundary conditions accompanied the DQM to transform the partial differential equation of a Bernoulli–Euler beam with a single edge crack into a discrete eigenvalue problem. The DQM results for the natural frequencies of cracked beams agree well with other literature values. The sampling point number effect, the location of the crack effect and the depth of the crack effect on the accuracy variation of calculated natural frequencies are presented by using two elements in this work. The effects of axial loading, foundation stiffness, opening crack and closing crack are also studied.

A Simplified Analysis of the Post-buckling Behavior of a Compressed Reinforcing Bar

Recently, a computational methodology based on a sequential multiscale approach, which facilitates numerical simulation of an R/C building demolition has been developed. In this type of analysis, it is necessary to capture the behavior of compressed reinforcement bars until complete rupture, which occurs due to extensive bending in the post-buckling regime. To this end, a simplified analytical model of the post-buckling behavior of a compressed bar is proposed. The simplification consists namely in considering rigid-plastic material behavior, neglecting axial contraction of the central line, and approximating the shape of the deformed central line in the plastic hinges by a circular arch. Consequently, the axial loading force, bar end displacement, and extreme strain can be expressed in relatively simple closed forms. The results obtained with the proposed model show very close agreement with those obtained by a detailed and realistic finite element analysis, which justifies the use of the simplifying assumptions.