Direct Compressive Forces Research Articles

Experimental behaviour of plate girders in steel – Internal forces in intermediate transverse stiffeners

Economical design of steel plate girders usually adopts slender web panels sometimes combined with large panel aspect ratio, which determines the elastic stability of the web panel. The adoption of transverse stiffeners is one efficient strategy to retard the web buckling due to shear. The primary role of intermediate transverse stiffener is clear: divide the web into panels providing lateral support to the web plate along the span – This increases the shear strength of the web. However, FprEN 1993-1-5: 2022 [1] stiffener design approach is based mainly on direct compressive forces resulting from the tension filed action in post buckling phase. According to multiple investigations, this area requirement is much higher than that found in laboratory testing and numerical simulations. The findings of experimental testing on eight plate girders with thin webs and two configurations of transverse stiffeners under ultimate load are presented. Using the web and stiffener measure strains, the internal stiffener forces are calculated past the shear failure of the plate girders. These results show that the axial compression and bending moment measured in the intermediate transverse stiffeners are considerably lower than those specified for the design by the FprEN 1993-1-5: 2022 [1].

Temperature Evolution and Heating Rates of Biomass undergoing Ablative Pyrolysis

The ablative reactor may be employed to enable fast pyrolysis to produce bio-oil from relatively large-sized biomass samples. Ablation mainly involves direct compressive force and conductive heat transfer between a hot surface and the biomass materials. Temperature evolution and heating rates are important operating factors in the biomass thermal conversion process. In this work, experimental and analytical investigations were carried out for different vertical dimensions of the biomass samples (2-20mm) and hot plate temperatures (400-550°C). It was shown that the thermal characteristics of the biomass were mainly affected by the transient conditions. It was observed that volatile release occurred during the transient heat transfer periods. It was found that at the maximum hot plate temperature of 550°C, the highest heating rate that could be achieved by ablation was more than 600°C/min.

A Review of Common Shoulder Injuries

The shoulder complex is an intricate combination of bones, muscles, and ligaments that function synergistically to move the arm. While the shoulder is a very mobile joint, allowing for movement in all planes, it is not an apparatus known for stability. The injuries that can be sustained by the shoulder are often extensive and could give rise to further injuries in other aspects of the body, including the arm, back, and sternum. Two of the most common injuries that can be sustained by the shoulder include clavicular fractures and anterior shoulder dislocations. Clavicular fractures are most commonly sustained by direct compressive force directed towards the sternum and applied to the ipsilateral shoulder, while anterior dislocations commonly occur as a result of direct force projected anteriorly while the arm is externally rotated and abducted. The mechanism of injury for both clavicular fractures and anterior dislocations dictates the injuries' severity which subsequently determines the extent of treatment and rehabilitation that is needed. Both conservative and surgical methods are effective in treating shoulder injuries depending upon an individual's activity level and the extent of the injury. Following treatment, proper rehabilitation of the injury is crucial to regain the shoulder's active pain-free range of motion, strength of surrounding muscles, and neuromuscular control, while ensuring a timely return to daily activities.

English

INTRODUCTION: Abdominal trauma continues to account for a large number of trauma related injuries and deaths. Motor vehicle accidents, accidental fall are leading causes of blunt and penetrating trauma to abdomen. Blunt abdominal trauma is one of the leading preventable causes of the unnatural death in developed and developing countries. Blunt trauma is particularly deceptive as the clinical manifestations of the injury may be delayed for hours or days even though internal damage is serious and sometimes lethal. In open cases of abdominal trauma the clinical manifestations, diagnosis and management will be easier but closed cases of abdominal trauma offers a great challenge to the treating surgeon. Injuries to the abdominal viscera, caused by blunt trauma, are particularly common in civilian life. The blunt trauma differs from penetrating trauma, as the different organs are characteristically injured by compression from blunt straining. The solid organs such as spleen, liver, kidney, pancreas, etc., are the most vulnerable, while the hollow viscera like stomach, intestines and bladder are less likely to be involved. The outstanding features of injury to solid organ are the haemorrhage and shock, while in hollow visceral injury shock follows with the development of peritonitis. The aim of this study is to analyse the incidence of hollow viscus perforation and solid organ injuries and find out the morbidity and mortality in blunt abdominal trauma. AIM OF THE STUDY: 1. To evaluate the age and sex incidence of the involved patient population. 2. To evaluate the different organ systems involved in various modes of presentations as a primary tool in early diagnosis. 3. To find a possible treatment protocol cases of blunt trauma to the abdomen following road traffic accident. MATERIALS AND METHODS: 162 cases of blunt trauma following road traffic accidents admitted in all the surgical units at Thanjavur Medical College Hospital during the period of September 2016 to September 2017 The cases were selected with accurate history of trauma including the mode of injury, the time elapsed since injury till admission and history of primary resusitation documented carefully. Based on a careful history and meticulous physical examination combined with adjunctive investigations, a decision to operate or to manage conservatively was taken. Baseline laboratory parameters like blood urea, blood sugar, serum electrolytes and blood grouping was done in all cases. Plain x-ray abdomen in an erect posture was taken for all stable patients. Other investigations appropriately taken for associated injuries. Ultra sonogram and CT scan abdomen was not done as a routine diagnostic investigation, however few cases were subjected to the same in view of special circumstances. A performa of each case including the case, sex, mode of injury, and an accurate history suggesting the mode of injury was compiled. Personal history of previous trauma or surgeries and alcohol or drug intoxication was specifically sought for. Plain skiagram of the abdomen and four quadrant aspiration was done in all the cases. 17 All the patients were resusitated with ringer lactate solution and blood before surgical intervention. All the patients were manadatorily maintained on nasogastric suction, intravenous fluid replacement and broad spectrum antibiotics. Selected cases were catheterised. Post operative complications were specifically sought for and treated appropriately. DISCUSSION: In our study of blunt injury abdomen, caused due to road traffic accidents, 162 cases were admitted in thanjavur medical college and hospital from september 2016 to september 2017. Males accounted for 103 patients [45%]. Vijay malhotra et al also reported similar sex incidence in the landmark 1998 study. The proportionate majority of males could account for the male preponderance involved in road traffic accidents, also to a certain exten by their aggressive behaviour. Solid organ injuries like liver and spleen injuries due to direct compressive forces resulting from collision. Bowel injuries might have been contributed by deceleration shear stess and sudden increase in abdominal pressure. 49 cases [30.2%] were hemodynamically unstable at presentation and required aggressive reusitation. The connectialt and suffolk show a 44% shock incidence at presentation. 20 cases died among 162 cases, in which peritonitis waas the cause of death in 15 cases and 5 patients died due to hypovolemic shock, this is due to late presentation after which they have treated in mofsul hospitals and was referred to TMCH. Physical examination revealed abdominal bruises in 62 cases, abdominal pain and distension in 70 cases. Guarding found in all cases. Rigidity was noticed in 20 patients. Davis et al reported abdominal pain in 75% of the patienst, rigidity and rebound tenderness in 25%.

Mechanosensitivity of a Rapid Bioluminescence Reporter System Assessed by Atomic Force Microscopy

Cells are sophisticated integrators of mechanical stimuli that lead to physiological, biochemical, and genetic responses. The bioluminescence of dinoflagellates, alveolate protists that use light emission for predator defense, serves as a rapid noninvasive whole-cell reporter of mechanosensitivity. In this study, we used atomic force microscopy (AFM) to explore the relationship between cell mechanical properties and mechanosensitivity in live cells of the dinoflagellate Pyrocystis lunula. Cell stiffness was 0.56 MPa, consistent with cells possessing a cell wall. Cell response depended on both the magnitude and velocity of the applied force. At the maximum stimulation velocity of 390 μm s−1, the threshold response occurred at a force of 7.2 μN, resulting in a contact time of 6.1 ms and indentation of 2.1 μm. Cells did not respond to a low stimulation velocity of 20 μm s−1, indicating a velocity dependent response that, based on stress relaxation experiments, was explained by the cell viscoelastic properties. This study demonstrates the use of AFM to study mechanosensitivity in a cell system that responds at fast timescales, and provides insights into how viscoelastic properties affect mechanosensitivity. It also provides a comparison with previous studies using hydrodynamic stimulation, showing the discrepancy in cell response between direct compressive forces using AFM and those within flow fields based on average flow properties.

Performance analysis of the protective effects of bicycle helmets during impact and crush tests in pediatric skull models

Bicycle accidents are a very important cause of clinically important traumatic brain injury (TBI) in children. One factor that has been shown to mitigate the severity of lesions associated with TBI in such scenarios is the proper use of a helmet. The object of this study was to test and evaluate the protection afforded by a children's bicycle helmet to human cadaver skulls with a child's anthropometry in both "impact" and "crushing" situations. The authors tested human skulls with and without bicycle helmets in drop tests in a monorail-guided free-fall impact apparatus from heights of 6 to 48 in onto a flat steel anvil. Unhelmeted skulls were dropped at 6 in, with progressive height increases until failure (fracture). The maximum resultant acceleration rates experienced by helmeted and unhelmeted skulls on impact were recorded by an accelerometer attached to the skulls. In addition, compressive forces were applied to both helmeted and unhelmeted skulls in progressive amounts. The tolerance in each circumstance was recorded and compared between the two groups. Helmets conferred up to an 87% reduction in so-called mean maximum resultant acceleration over unhelmeted skulls. In compression testing, helmeted skulls were unable to be crushed in the compression fixture up to 470 pound-force (approximately 230 kgf), whereas both skull and helmet alone failed in testing. Children's bicycle helmets provide measurable protection in terms of attenuating the acceleration experienced by a skull on the introduction of an impact force. Moreover, such helmets have the durability to mitigate the effects of a more rare but catastrophic direct compressive force. Therefore, the use of bicycle helmets is an important preventive tool to reduce the incidence of severe associated TBI in children as well as to minimize the morbidity of its neurological consequences.

Effect of mechanical compression due to load carrying on shoulder muscle fatigue during sustained isometric arm abduction: an electromyographic study

The use of surface electromyography (EMG) for studying the effect of mechanical compression of occupational origin on muscle fatigue has been the subject of poor attention in ergonomic research. This study examined the effect of backpack carrying on fatigue of two shoulder muscles during sustained low force static contraction: the middle deltoid (MD) muscle and the upper trapezius (UT) muscle on which the backpack strap exerted direct compressive force. EMG activities of MD and UT muscles, of the dominant and non-dominant sides, were studied on eight subjects during two tasks, a maximal and an exhausting submaximal bilateral isometric 90 degrees arm abduction, which were performed while carrying a backpack load of 0, 10, and 20 kg, respectively. EMG amplitude (root mean square, RMS) and spectral (mean power frequency, MPF) parameters were computed from the recorded signals. No significant differences between the dominant and non-dominant sides were found for none of the parameters whatever the load-carrying mass. Load-carrying masses which were tested did not influence significantly the maximal bilateral arm abduction performance contrary to the time to exhaustion during the submaximal task, which decreased significantly with increasing load-carrying mass. A significant increase in fatigability, defined by the slope of MPF decrease, was observed for both muscles when load-carrying mass increased; but only UT presented a significant increase in muscle fatigue level, defined by the MPF value with respect to its initial value, at the end of the exhausting submaximal task. Furthermore, the increase in muscle activation of UT, quantified by RMS, during the exhausting task was not significantly higher with increasing load-carrying mass. So, the increased signs of local fatigue of UT may be interpreted by a localised blood flow impairment resulting from the direct compressive force exerted by backpack on this muscle.

Interface corrective force measurements in Boston brace treatment.

Brace application has been reported to be effective in treating idiopathic adolescent scoliosis. The exact working mechanism of a thoracolumbo spinal orthosis is a result of different mechanisms and is not completely understood. One of the supposed working mechanisms is a direct compressive force working through the brace upon the body and thereby correcting the scoliotic deformity, achieving optimal fit of the individual orthosis. In this study we measured these direct forces exerted by the pads in a Boston brace in 16 patients with idiopathic adolescent scoliosis, using the electronic PEDAR measuring device (Novel, Munich, Germany). This is designed as an in-shoe measuring system consisting of two shoe insoles (size 8 1/2), wired to a computer, recording static and dynamic pressure distribution under the plantar surface of the foot. After positioning the inserts between the lumbar and thoracic pads and the body, we measured the forces acting upon the body in eight different postures. In all positions the mean corrective force through the lumbar brace pad was larger than the mean corrective force over the thoracic brace pad. Some changes in body posture resulted in statistically significant alterations in the exerted forces. There was no significant correlation between the magnitude of the compressive force over the lumbar and thoracic brace-pad and the degree of correction of the major curve. Comparing the corrective forces in a relatively new (<6 months) and old (>6 months) brace, there was no statistically relevant difference, although the corrective force was slightly larger in the new braces. We think that the use of this pressure measurement device is practicable and of value for studies of the working mechanism of brace treatment, and in the future it might be of help in achieving optimal fit of the individual orthosis.

Deformation and rupture of the articular surface under dynamic and static compression

Cartilage-on-bone samples were dynamically and statically compressed at various stress levels to determine the deformation and rupture behaviour of the articular surface (AS). Instantaneous deformations were captured photographically by using a transparent indenter in combination with a ultra high speed flash. Principal strains (PS) were evaluated using large deformation theory. The tensile strains induced indirectly in the AS were a function of the rate at which the direct compressive force was applied. At the same compressive stress the tensile strains induced statically were approximately twice those induced dynamically. Rupture of the AS occurred in about 60% of those specimens tested statically at 15 MPa and followed approximately the split-line direction. By contrast, no rupture was observed dynamically even at stresses as high as 28 MPa. In terms of joint function the research demonstrates that the AS is considerably more resistant to rupture under dynamic than under static loading. The biomechanical parameter governing rupture appears to be the level of indirectly induced surface strain rather than the directly applied compressive stress. The very different mechanisms controlling the compressive deformation of articular cartilage (AC) at high vs low rates of loading clearly influence the levels of in-plane strain induced in the AS.

Head injuries in sport.

Injuries to the head and neck are the most frequent catastrophic sports injury, and head injuries are the most common direct athletic cause of death. Although direct compressive forces may injure the brain, neural tissue is particularly susceptible to injury from shearing stresses, which are most likely to occur when rotational forces are applied to the head. The most common athletic head injury is concussion, which may very widely in severity. Intracranial haemorrhage is the leading cause of head injury death in sports, making rapid initial assessment and appropriate follow up mandatory after a head injury. Diffuse cerebral swelling is another serious condition that may be found in the child or adolescent athlete, and the second impact syndrome is a major concern in adult athletes. Many head injuries in athletes are the result of improper playing techniques and can be reduced by teaching proper skills and enforcing safety promoting rules. Improved conditioning (particularly of the neck), protective headgear, and careful medical supervision of athletes will also minimise this type of injury.

Dynamic fracture characteristics of the osteochondral junction undergoing shear deformation

This paper presents a biomechanical study of the dynamic fracture response of the osteochondral regions of both immature and mature cartilage-bone laminates induced through shear loading. An instrumented impact machine, providing both mechanical and real-time macro-photographic fracture data, was used to load the osteochondral region in shear by means of a direct compressive force applied to the cartilage layer only, and in a direction parallel to the plane of the osteochondral junction. This force was applied at a known velocity of 2500 mm/s. Our results show that under these conditions of shear loading the dynamic mode II fracture toughness of the osteochondral region of the mature tissue is approximately 1.5 times that of its immature counterpart, and that the derived dynamic shear stiffness of the immature tissue is about 4 times that of the mature. The structural studies demonstrated that the mature tissue delaminates within a well-defined tidemark region whilst the immature fractures through the subchondral bone into which fingers of articular cartilage penetrate. We suggest that this pseudo-brittleness of the immature tissue could explain why there is an increased susceptibility to osteochondral failure in the younger human joint. Finally, we note that the strength-to-toughness relationship, in which stiffer engineering materials are known to exhibit lower fracture toughness, also applies to the cartilage-bone system.

The impact origin of genetic material

It is proposed that high velocity asteroidal impacts with the Earth created polymeric nucleotide sequences out of monomeric nucleotides via direct compressive forces. The developed model describes the simultaneous formation of histone-equivalent proteins and RNA DNA -equivalent template structures as a natural and expected consequence of bolide impactions with organic material accumulating on the crustal surface of the Earth approximately 3.8–3.5 billion years ago. It is shown that literally billions of different gene-equivalent nucleotide sequences, each one having a set of surface-complementary histone-equivalent proteins, might be created in such a manner. It is hypothesized that it is this process that gave rise to the chemical substrate upon which Darwinian selective forces have acted ever since.