Reduced Shear Force Research Articles

Optimization the Resistance Spot Welding Parameters of Austenitic Stainless Steel and Aluminum Alloy Using Design of Experiment Method

This research aims to study the effect of RSW parameters on the sheerforce of the spot weldedfor two materials {AISI 304L and AA 6061-T6}with (0.5 and 0.7 mm) thickness. Three values for each welding parameters (welding current, electrode force, squeeze time and welding time) are to be used. The effect of those parameters has been analyzed by using design of experiments (DOE) in order to determine and reduce the number of the tested specimens. The experimental tests have been donethat are;shear, micro hardness tests and microstructure examination. It was found that the maximum shear force in welding of similar material AISI 304L is (F = 4.78 KN for t = 0.7 mm), while in the joint of dissimilar material (AA 6061-T6 with AISI 304L), the maximum shear force is (F = 1.42 KN for t = 0.7 mm). These values have been optimized to reach (F =5.13 KN & F =1.54 KN) respectively by using DOE. The minimum shear force was (F = 0.07 KN in t = 0.5 mm). It was found that, increasing the welding current and sheet thickness gave an increase in the shear force, but at the same time the reduction in shear force has occurred during the increasing in electrode force, squeeze time and welding time. From micro hardness tests, it was found that the maximum value of hardness was at the center of nugget zone (NZ) and it reduces slightly until reaching constant values away from nugget zone.

Comparison of myofibrillar protein degradation, antioxidant profile, fatty acids, metmyoglobin reducing activity, physicochemical properties and sensory attributes of gluteus medius and infraspinatus muscles in goats

BackgroundThe functionality of myofibrillar proteins is a major factor influencing the quality attributes of muscle foods. Nonetheless, the relationships between muscle type and oxidative changes in chevon during ageing are meagrely elucidated. Postmortem changes in antioxidant status and physicochemical properties of glycolytic gluteus medius (GM) and oxidative infraspinatus (IS) muscles in goats were compared.MethodsTwenty Boer bucks (9–10 months old, body weight of 36.9 ± 0.725 kg) were slaughtered and the carcasses were subjected to chill storage (4 ± 0.5 °C). Analyses were conducted on GM and IS muscles sampled on 0, 1, 4 and 7 d postmortem.ResultsChill storage did not affect the antioxidant enzyme activities in both muscles. The IS had greater (P < 0.05) superoxide dismutase and catalase activities than GM. Carotenoid and tocopherol contents did not differ between muscles but decreased (P < 0.05) over storage. The IS had higher (P < 0.05) glycogen and ultimate pH and lower (P < 0.05) shear force and cooking loss than GM. The carbonyl content, % metmyoglobin, drip loss and TBARS increased (P < 0.05) while free thiol, metmyoglobin reducing activity (MRA), shear force and myoglobin decreased (P < 0.05) over storage. Muscle type had no effect (P > 0.05) on free thiol, MRA and TBARS. The GM had lower (P < 0.05) redness on d 0 and 1 than IS while the IS had greater carbonyl, % metmyoglobin and drip loss than GM on d 7. The reflective density of slow myosin heavy chain (MHC) was higher (P < 0.05) while the density of fast MHC and actin was lower (P < 0.05) in IS than GM. Regardless of muscle type, the density of MHC decreased (P < 0.05) while that of actin was stable over storage. Nonetheless, the degradation of fast and slow MHC was greater (P < 0.05) in IS than GM. Muscle type had no effect (P > 0.05) on consumer preference for flavour, juiciness and overall acceptability. However, IS had higher (P < 0.05) tenderness score than GM on d 1 and 4 postmortem. Intramuscular fat was higher (P < 0.05) in IS compared with GM. Fatty acid composition did not differ between the muscles. However, GM had lower (P < 0.05) n-6/n-3 ratio than IS. The n-3 and n-6 PUFA declined (P < 0.05) while the SFA increased (P < 0.05) over storage.ConclusionThe changes in myofibrillar proteins and physicochemical properties of goat meat during postmortem chill storage are muscle-dependent.

Behavior of RCC and Composite Structure under Seismic Loads

The structural community in India is yet to bring in practice the modern approach of composite modeling in tall building even after its proven benefits of speedy and easier erection, Labor saving, stiff- Strength, safe and full life span. Here this paper presents the comprehensive analysis of G+20 building. A true attempt is made to study the behavior of axial force, shear force, bending moment, Twisting moment base shear and displacement by using E-tab 2015 software. The result proves that performance of composite model is not only habitable, stable, safe but also cost and time saving. A qualitative better change is seen in the structural members of slab, beam and FEC column which indicate less bending, twisting moment, displacement and reduce shear force, axial force resulting into high strength, stiffness, speedy erection and efficient use of concrete and steel model of composite designing.

Freezing, thawing and aging effects on beef tenderness from Bos indicus and Bos taurus cattle

The objective of this study was to determine the effects of freezing prior to aging on the meat tenderness of young Nellore and Aberdeen Angus bulls. Samples of the longissimus thoracis muscle were submitted to two treatments: conventional aging and freezing (−20°C for 40days) followed by thawing and aging periods. The meats were evaluated after 0, 7, 14 and 21 aging days (1°C). Freezing increased (P<0.05) purge, cooking loss and total exudate loss throughout aging. Nellore meats had greater total exudate loss and shorter sarcomere lengths (P<0.05). Freezing increased proteolysis during aging in the meats of both breeds, but reduced shear force was found (P<0.05) only in Aberdeen Angus meats and only at time zero. These results suggest that the meat tenderizing process by freezing prior to aging may contribute to meat tenderness in the first weeks of aging, but it is dependent on the animal breed.

Effect of Buckling Restrained Braces Locations on Seismic Responses of High-Rise RC Core Wall Buildings

Conventionally, a flexural plastic hinge is designed and detailed at the core wall base and coupling beams ends to control the seismic responses. This strategy is based on allowing the damage to be concentrated on main structural components. To avoid such damage, an alternative strategy using energy dissipating devices (EDDs) such as buckling restrained braces (BRBs) is being studied and implemented nowadays. In this study, effect of BRBs locations on forty- (40-) story high-rise RC core wall case study building has been studied in detail using Nonlinear Response History Analysis (NLRHA) for seven spectrally matched ground motions. BRBs have been installed at critical locations identified with respect to the maximum DBE elastic modal racking shear deformation demands and force (shear and moment) demands in three different options. The force, deformation, and energy demands on structural components are compared for conventional design and different options of BRBs. The comparison with conventional design shows that BRBs not only are effective for reducing shear force demand along wall height, bending moment demand at mid height, and deformation demands by 10%, 45%, and 45%, respectively, but significantly reduce the rotation and energy demands in the core wall by 90% and 250%, respectively.

Flow boiling instability characteristics in expanding silicon microgap heat sink

The effects of mass flux, heat flux and microgap configuration on flow boiling instability in expanding microgap heat sink are experimentally investigated. Characterizations of instabilities are performed for deionized water mass fluxes, G=400–1000kg/m2s, imposed effective heat flux q″eff ranging from 0 to 80W/cm2 for three different microgap configurations, straight microgap of depth 200μm and expanding microgap having same inlet depth 200μm with gradually increasing exit depth 300μm and 460μm. High speed flow visualizations are conducted simultaneously along with experiments to explore the bubble behavior in expanding microgap heat sink. Results show that two phase expanding microgap heat sink has novel potential to mitigate the flow instabilities and flow reversal issues as the generated vapor has room to expand downstream and also due to reducing shear force along the direction of expansion. Reduced share force is beneficial as it contributes to easing flow in the direction of expansion and thus, eliminates flow reversal and maintains stable flow boiling condition. In addition, inlet pressure oscillation increases gradually with the increase of mass flux and heat flux due to the extensive repetitive backward expansion of vapor slug. Whereas, wall temperature oscillation decreases with the decrease of mass flux and increase of heat flux due to the presence of stable annular flow regime at high heat flux and low mass flux condition before dryout approaches.

Characteristics and Properties of Reinforced Oil Palm Frond Fibers (OPFF) in Polyvinyl Alcohol (PVA) Composite for Tubular-Shaped Trays

Effects on characteristics and mechanical properties of oil palm frond fiber (OPFF) as a reinforced element in poly vinyl alcohol (PVA) were investigated in this study. Series of different loading of OPFF were prepared by the following compositions: 5, 10, 15, 20 and 25 part per resin (phr). Glycerol at 35 phr was also compounded using twin-screw extruder to decrease degree of crystallinity and to reduce shear force of PVA to improve the processability. Injection molding was used to produce specimen for testing. The results indicated that the OPFF has an impact on mechanical properties of the composite material. Different scanning calorimeter (DSC) showed that the melting temperature (Tm) of OPFF reinforced PVA blended with glycerol was shifted to having decrease when compared to the pure PVA. Different loading contents of OPFF indicated that the compressive strength and morphological properties performed by a similar fashion. A highest compressive strength and the modulus of OPFF-reinforced PVA at 25 phr were achieved. Scanning electron microscope (SEM) indicated that OPFF-reinforced PVA at 25 phr yielded no accumulation of OPFF fibers but showed the dispersion in the matrix phase. In conclusion, the OPFF derived from oil palm industry can be used as reinforcement for manufacturing of plant pot in the future stage

Rocking-horse phenomenon of the glenoid component: the importance of inclination

Abnormal glenoid version positioning has been recognized as a cause of glenoid component failure caused by the rocking horse phenomenon. In contrast, the importance of the glenoid inclination has not been investigated. The computed tomography scans of 152 healthy shoulders were evaluated. A virtual glenoid component was positioned in 2 different planes: the maximum circular plane (MCP) and the inferior circle plane (ICP). The MCP was defined by the best fitting circle of the most superior point of the glenoid and 2 points at the lower glenoid rim. The ICP was defined by the best fitting circle on the rim of the inferior quadrants. The inclination of both planes was measured as the intersection with the scapular plane. We defined the force vector of the rotator force couple and calculated the magnitude of the shear force vector on a virtual glenoid component in both planes during glenohumeral abduction. The inclination of the component positioned in the MCP averaged 95° (range, 84°-108°) and for the ICP averaged 111° (range, 94°-126°). A significant reduction in shear forces was calculated for the glenoid component in the ICP vs the MCP: 98% reduction in 60° of abduction to 49% reduction in 90° of abduction. Shear forces are significantly higher when the glenoid component is positioned in the MCP compared with the ICP, and this is more pronounced in early abduction. Positioning the glenoid component in the inferior circle might reduce the risk of a rocking horse phenomenon.

Effects of forage silage species on yearling growth performance, carcass and meat quality, and nutrient composition in a forage based beef production system

Berthiaume, R., Lafrenière, C., Girard, C., Campbell, C. P., Pivotto, L. M. and Mandell, I. B. 2015. Effects of forage silage species on yearling growth performance, carcass and meat quality, and nutrient composition in a forage based beef production system. Can. J. Anim. Sci. 95: 173–187. Forty weaned, crossbred beef calves (predominantly Angus and Simmental) were forage-finished using all-silage diets (red clover–timothy versus tall fescue) to examine forage species’ effects on growth performance, carcass traits, meat quality, and nutrient composition. Weaned calves (257 d of age) were forage-finished using red clover–timothy or tall fescue silage and harvested at approximately 1 yr of age. During carcass processing, one side from each carcass was covered with a polyliner to examine if reducing rates of chilling could compensate for limited fat cover expected from low dietary energy contents fed, and limited time on feed. Longissimus thoracis, semimembranosus, and semitendinosus steaks were aged 10, 14, and 21 d to examine effects on Warner–Bratzler shear force values while fatty acid and vitamin B12 composition were determined on 10-d-aged steaks. Average daily gain, feed efficiency, hot carcass weights, and longissimus muscle area were greater (P&lt;0.03) when cattle were fed red clover–timothy versus tall fescue silage, most likely due to the higher protein content of red clover–timothy silage. Shear force was greater (P&lt;0.002) in steaks from all muscles evaluated from cattle fed tall fescue versus red clover–timothy silage. In comparison to 10-d-aged steaks, 14 d of ageing were needed to reduce (P&lt;0.001) shear force for longissimus steaks, while 21 d of ageing were needed to reduce (P&lt;0.001) shear force for semitendinosus steaks. Use of a polyliner decreased (P=0.0001) the rate of temperature decline at selected carcass sites, but did not reduce shear force values. The percent of n-3 fatty acids and polyunsaturated fatty acid/saturated fatty acid ratio were greater (P&lt;0.04) in longissimus from cattle fed red clover–timothy versus feeding tall fescue silage. Feeding red clover–timothy silage improved growth performance, carcass, shear force, and fatty acid composition traits versus feeding tall fescue silage.

Effect of radiation processing on meat tenderisation

The effect of radiation processing (0, 2.5, 5 and 10 kGy) on the tenderness of three types of popularly consumed meat in India namely chicken, lamb and buffalo was investigated. In irradiated meat samples dose dependant reduction in water holding capacity, cooking yield and shear force was observed. Reduction in shear force upon radiation processing was more pronounced in buffalo meat. Protein and collagen solubility as well as TCA soluble protein content increased on irradiation. Radiation processing of meat samples resulted in some change in colour of meat. Results suggested that irradiation leads to dose dependant tenderization of meat. Radiation processing of meat at a dose of 2.5 kGy improved its texture and had acceptable odour.

Factors Influencing the Shear Rate Acting on Silicone Oil to Cause Silicone Oil Emulsification

The shear force between silicone oil (SO) bubble and aqueous during eye movements may underlie the development of SO emulsification. This study examines factors that may affect such shear force induced by eye movements. A surface-modified model eye chamber was put under large-amplitude eye movements (amplitude 90°, angular velocity 360°/s, and a duration 300 ms). Agarose-made indentations were introduced to mimic the effect of encircling scleral buckle. Two SOs (1300 and 5000 centistokes [cSt]), three volumes (3, 4, and 5 mL), and two eye chambers (with and without indentation) were tested. Video recording was used to capture the movements of SO inside the model chamber under various conditions. The presence of indentation within the eye chamber significantly reduced the velocity of SO movements relative to the eye chamber movements (P < 0.001). To a lesser extent, an increase in viscosity also had a significant effect in reducing the relative movements. No significant effect was observed for the extent of SO fill in the chamber. Our experimental model suggests indentation within an eye, such as that created by scleral buckling, may have the greatest influence in reducing shear force induced by eye movements. Therefore, using an encircling scleral buckle may be similarly or more effective than using SO with higher viscosity in lowering the propensity to SO emulsification.

Study on grooved wall flow under rarefied condition using the Lattice Boltzmann Method

Decreasing energy consumption is a key issue for stratospheric airship to maintain its high altitude long-endurance feature. The airship envelope covered micro-grooves is considered as a feasible way to reduce resistance in order to save energy. The key to using grooves as the drag reduction technique is to evaluate its drag reduction ability under the condition of rarefied gas which is different from the original continuum atmospheric state. In this paper, the drag reduction ability of V-shape and rectangular micro-grooves under both continuum and rarefied condition is evaluated using the Lattice Boltzmann Method (LBM). This method modified for rarefied flow has been validated by the analytical solution in this paper. The local vortices are obviously observed within the grooves in the continuum and slippery flow regimes. The mechanism of drag reduction with grooves is elucidated at first and the ability of drag reduction under the rarefied condition is then evaluated by comparison of that under continuum condition. In the end, both the V-shape and rectangular grooved wall flow with different height and width are simulated. The relationships of drag reduction ability and the groove geometry are also determined and evaluated. Our results reveal that the grooves can reduce the resistance with a drag reduction rate of about 6% in the continuum. The drag reduction ability of the same grooves, however, decreases to 2.5% or less in the slippery regime. The grooves with appropriate size which make the vortices full within grooves can reduce shear force between fluid and wall. The results obtained in this paper are good references to the design of stratospheric airship envelope and the drag reduction technique.

Effect of freezing as pre-treatment prior to pulsed electric field processing on quality traits of beef muscles

The purpose of this research was to study the effects of freezing as pre-treatment prior to pulsed electric field (PEF) on the quality of beef semitendinosus muscles. Fresh and frozen-thawed samples were treated using square -wave bipolar pulses at electric field strength 1.4 kV/cm, pulse width 20 μs, frequency 50 Hz and total specific energy 250 kJ/kg. PEF caused significant microstructural changes of meat tissue compared to freezing. Combined freezing–thawing and PEF resulted in improved tenderness indicated by reduced shear force, but not PEF alone. PEF significantly increased purge loss but not cooking loss. A two log-unit increase in aerobic microbial counts during log phase of frozen-thawed PEF-treated samples was positively associated with increased purge loss. PEF itself did not affect the ratios of polyunsaturated/saturated fatty acids and omega 6/omega 3 nor the free fatty acid profiles. Freezing with and without PEF greatly affected the volatile profile of meat. PEF treatment provides an alternative to mechanical, thermal and enzymatic cell disintegration of animal raw materials, providing a short duration (milliseconds) and energy efficient treatment. In this study, the possible relationship between freezing prior to PEF and changes in beef tissue microstructure that influence storage stability and safety was investigated. The results of this study contribute toward understanding how PEF induced changes in beef microstructure influence the important quality attributes of beef. • PEF treatment resulted in microstructural changes in meat tissue. • PEF had a positive effect on shear force of frozen–thawed samples after storage. • PEF treatment had no effect on PUFA/SFA or on n6/n3 ratios. • Free fatty acid profile of beef samples was unaffected by PEF treatment. • PEF treatment decreases oxidative stability of frozen–thawed meat.

Development and evaluation of a system to assess the effect of footwear on the in shoe plantar pressure and shear during gait

In this paper, we propose a system to assess the effect of footwear on the in-shoe plantar pressure and shear during gait. In our previous study, we developed a system for measuring the plantar pressure and shear inside footwear using specialized shoes and insoles with sensors. In this study, based on the previous study, 1) we realized a method to measure directly the in-shoe plantar pressure and shear applied from footwear, 2) verified the validity and reliability of the method and 3) evaluated the ability of the system to assess the effect of footwear by measurements with multiple subjects and various footwear. The reliability and validity were demonstrated by comparison with our previous system. From the evaluation of the newly developed system, we found four suggestions as the following; a) Footwear does not always reduce the pressure and shear force. b) Fixing the instep with shoelace or straps is effective in the reduction of shear force on risk regions of plantar. c) People with callus show significantly higher peak shear force (3.31 ± 0.78 (kgf)) than people without callus (2.03 ± 0.42 (kgf)) when they walk with their usual wearing shoes (p < 0.01). But in barefoot walking, there is no significant difference (2.59 ± 1.08 (kgf) versus 2.67 ± 0.99 (kgf), (p = 0.66)). d) People with callus can reduce the shear force by changing footwear. The system employed in this study can be used for assessing the effect of the intervention such as footwear or instruction of a walk.

Increased horizontal shoulder abduction is associated with an increase in shoulder joint load in baseball pitching

Soft tissues of the shoulder undergoes substantial stresses due to humeral head movement, and this may contribute to throwing shoulder injuries in baseball pitchers. Prevention and management of throwing shoulder injuries critically rely on reduction of shear force at the shoulder joint. However, the amount and direction of the force applied to the shoulder during the throwing motion have not been clarified. The purpose of this study was to analyze forces applied to the shoulder during a baseball pitch. We performed biomechanical analysis of 213 baseball pitchers of various ages and skilllevels. Throwing motion was analyzed with a 3-dimensional motion capture system. The Eulerangle sequence was adopted to describe angular values of the upper arm relative to the trunk for shoulder rotation, and inverse dynamics was used to estimate the resultant joint forces at the shoulder. There was a significant relation between horizontal abduction/adduction angle and resultant anterior/posterior force at the point of maximum external rotation (MER) (r=-0.63, P<.01), whereby increased horizontal abduction was associated with increased resultant anterior force. There was a significant but weak correlation between abduction/adduction angle and superior/inferior force at MER (r=0.24, P<.01). Comparison among the groups with variable ages and skill levels showed larger horizontal abduction and smaller external rotation angles at MER in the adult amateur player group, whereas normalized compression force and internal rotation torque values at MER were smaller in the junior high school- and elementary school-aged groups. These results suggest that excessive horizontal abduction at MER increases anterior shear force in the shoulder and may lead to shoulder injuries. Focusing on reducing horizontal abduction at MER in the throwing motion may be key to preventing and managing shoulder injuries in baseball pitchers.

Effect of high-pressure short-time processing on the physicochemical properties of abalone (Haliotis discus hannai) during refrigerated storage

Abstract This study investigated the effects of high pressure short-time processing on the physicochemical and microbial characteristics of abalone during chilled storage. Pressurization at 200 MPa caused a decrease in pH and shear force compared to those in the control but thereafter increased with increasing pressure levels. Water holding capacity (WHC) of abalone decreased when pressurized at > 400 MPa. A greater reduction in shear force was observed after 1 week of storage. For color, reduction in the a* value of abalone was considerable during storage. Increasing pressure suppressed the generation of total volatile basic nitrogen compounds and total viable counts, whereas lipid oxidation occurred with increasing pressure. Pressurization at 200 MPa was the optimum pressure condition in which the shelf-life of abalone was extended to about 10 days compared to 3 days in the control. Industrial relevance For the use of high pressure as a pasteurization technique, commercial system is required not to exceed 5 min of holding time for the system maintenance purpose. In addition, this process is carried out under ambient temperature for the economical aspect. The abalone which is normally consumed as raw state in East Asia has very short shelf-life (

Tribology and Micromechanics of Chromium Nitride Based Multilayer Coatings on Soft and Hard Substrates

The tribological protection of carbon fiber reinforced epoxy composites (CFC) is essential for broadening their use from structural to functional applications, e.g., to linear bearings in mechanical engineering. However, their wear resistance in sliding and rolling contacts is low. This work focusses on the possibility of improving their tribological properties by the application of thin hard multi-layered coatings. Chromium nitride (CrN) single layer and chromium-CrN multilayer coatings of ~4 µm thickness, partly finished with a 1 µm diamond-like carbon (DLC) top layer, were deposited by magnetron sputtering at low temperatures on soft CFC and for comparison of the mechanical behavior on comparatively hard austenitic steel substrates. Structural investigations showed especially that the multilayer coatings possess a very fine grained, columnar microstructure and a very low density of intercolumnar micro-cracks, while the single layer coatings possess a coarse structure. The indentation testing and the analysis of the deformed and fractured cross-sections revealed a tougher behavior with improved plastic deformability of the multilayers in comparison to CrN single layers. However, in wear testing only coatings with DLC top layers significantly improved the tribological material properties of CFC. This is due to the reduced shear forces in sliding on low-friction DLC coatings on the soft epoxy-based CFC, decreasing the total dynamic stresses during sliding under high loads.

Molecular value predictions: Associations with beef quality, carcass, production, behavior, and efficiency phenotypes in Brahman cattle1

Data from 2 previously published experiments, New South Wales (NSW; n = 161) and Western Australia (WA; n = 135), were used to test molecular value predictions (MVP), generated from commercially available gene markers, on economically important traits of Bos indicus (Brahman) cattle. Favorable tenderness MVP scores were associated with reduced shear force values of strip loin (LM) steaks aged 7 d from Achilles-hung carcasses (P ≤ 0.06), as well as steaks aged 1 (P ≤ 0.08) or 7 d (P ≤ 0.07) from carcasses hung from the pelvis (tenderstretch). Favorable tenderness MVP scores were also associated with improved consumer tenderness ratings for strip loin steaks aged 7 d and either Achilles hung (P ≤ 0.006) or tenderstretched (P ≤ 0.07). Similar results were observed in NSW for rump (top butt; gluteus medius) steaks, with favorable tenderness MVP scores associated with more tender (P = 0.006) and acceptable (P = 0.008) beef. Favorable marbling MVP scores were associated with improved (P ≤ 0.021) marbling scores and intramuscular fat (IMF) content in the NSW experiment, despite low variation in marbling in the Brahman cattle. For the WA experiment, however, there were no (P ≥ 0.71) relationships between marbling MVP and marbling scores or IMF content. Although residual (net) feed intake (RFI) was not associated (P = 0.63) with the RFI (feed efficiency) MVP, the RFI MVP was adversely associated with LM tenderness and acceptability of 7-d-aged Achilles-hung carcasses in NSW (P ≤ 0.031) and WA (P ≤ 0.037). Some other relationships and trends were noted between the MVP and the other traits, but few reached statistical significance, and none were evident in both experiments. Results from this study provide evidence to support the use of the tenderness MVP. The value of the marbling MVP, which was associated with marbling in only 1 herd, warrants further evaluation; however, there appears to be no evidence to support use of the RFI MVP in Brahman cattle.

Optimum tuned mass damper design for preventing brittle fracture of RC buildings

Brittle fracture of structures excited by earthquakes can be prevented by adding a tuned mass damper (TMD). This TMD must be optimum and suitable to the physical conditions of the structure. Compressive strength of concrete is an important factor for brittle fracture. The application of a TMD to structures with low compressive strength of concrete may not be possible if the weight of the TMD is too much. A heavy TMD is dangerous for these structures because of insufficient axial force capacity of structure. For the preventing brittle fracture, the damping ratio of the TMD must be sufficient to reduce maximum shear forces below the values proposed in design regulations. Using the formulas for frequency and damping ratio related to a preselected mass, this objective can be only achieved by increasing the mass of the TMD. By using a metaheuristic method, the optimum parameters can be searched in a specific limit. In this study, Harmony Search (HS) is employed to find optimum TMD parameters for preventing brittle fracture by reducing shear force in additional to other time and frequency responses. The proposed method is feasible for the retrofit of weak structures with insufficient compressive strength of concrete.

Influence of distance between the rotation axis of back support and the hip joint on shear force applied to buttocks in a reclining wheelchair’s back support

The purpose of this study was to investigate the influence of the distance between the position of the rotation axis of the back support and hip joint on the changes in the shear force applied to the buttocks. Repeated-measures design. The subjects were 11 healthy adult men without leg and/or trunk diseases. The shear force applied to the buttocks was measured using a force plate. This study had three experimental conditions: the position of hip joint was taken as the 3 cm, 6 cm, and 9 cm forward from the standard sitting position. In returning to an upright position of back support, the shear force was 15.0 ± 2.9 %BW in the 3 cm forward condition, 16.7 ± 3.6 %BW in the 6 cm forward condition, and 19.5 ± 5.3 %BW in the 9 cm forward condition. Significant differences appeared between the 9 cm and the other conditions (p < 0.05). The results of this study suggested that the shear force applied to the buttocks changed in reclining back support and an increase in the distance between the axis of rotation of the back support and hip joint led to an increase in the remaining shear force after reclining the back support.