Ultimate Shear Force Research Articles

The usefulness of muscle color and pH for segregating beef carcasses into tenderness groups

A total of 3435 beef carcasses from animals 11 to 14 months of age (472 bulls, 978 heifers, 1985 steers) were evaluated over a ten year period to determine the usefulness of measurements of muscle color and pH for segregating carcasses into tenderness groups. All carcasses were aged for 6 days at 2°C. Color and pH measurements were obtained on the longissimus† muscle. A loin steak from the eleventh-twelfth thoracic vertebrae interface was microwaved to approximately 70°C to determine shear force values. Steers had the lowest ultimate pH and shear force values and bulls had the highest (P=0·0001). Steers also had lighter colored lean (P=0·0001) than bulls and heifers (i.e. higher mean colorimeter readings). Arbitrary segregation of carcasses into tenderness groups based on shear force values (⩽6·0 tender; >6·0 tough) resulted in the tender group having higher colorimeter readings (17·40 versus 16·76, P=0·0001) and ultimate pH values (5·70 versus 5·69, P=0·02) and lower shear force values (4·89 versus 7·65, P<0·0001). Year and breed effects were observed in all three traits (P=0·0001). However, time trends were not detected and the range in shear force values among breeds was relatively narrow (6·02–6·74). Subjective color scores, colorimeter readings, and ultimate pH values accounted for 48% or less of the variation in shear force values in all sex, year, and breed groups indicating that generally none of these traits were highly related to tenderness in a linear fashion. Arbitrary segregation of carcasses into tenderness groups based upon shear force value resulted in consistently higher shear force values for the toughh group (SV>6·0) and lower values for the tender group (SV⩽6·0) (P<0·05) than the overall mean shear force value in all sex groups. Plotting of colorimeter readings and ultimate pH values against shear force values resulted in peaks within the range of colorimeter readings 8·5–16·5 and pH values 5·8–6·19. Segregation of carcasses with colorimeter readings within the range 8·5–16·5 was effective in segregating the tough ess steer and heifer carcasses and the tender bull carcasses, while segregation based upon pH values between 5·8 and 6·19 was effective in segregating the tough carcasses in all sex groups. Segregation based on both color and pH appeared to offer little advantage over the use of pH alone. Segregation of beef carcasses with ultimate longissimus pH values between 5·8 and 6·19 appears to be an easy, nondestructive, practical means to effectively remove the majority of tough carcasses (shear value >6·0) in all three sex groups, regardless of breed.

Ultimate shear force of structural concrete members Without Transverse Reinforcement Derived From a Mechanical Model (SP-885)

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Shear behavior of ferrocement box beams

The shear behavior of ferrocement box beams has been studied by conducting flexural tests on 15 beam specimens. The major parameters used were amounts of wire mesh reinforcement in webs and in flanges of the beam and shear span to depth ratio, a/h. Test results indicate that cracking and ultimate shear forces increase as wire mesh in webs is increased; placing wire mesh in flanges also increases shear resistance through arresting the tension cracks and causing them to be finer. Hence, the shear behavior is studied in relation to the total volume fraction of wire mesh reinforcement V f , which includes mesh reinforcement in both webs and flanges. The cracking and ultimate shear strengths also increase as the a/h ratio is decreased. The ACI equation for shear strength of conventional reinforced concrete beams without web reinforcement underestimates the cracking shear strength of ferrocement box beams. Hence, an empirical equation has been developed here using a multiple regression analysis to predict the shear strength of ferrocement box beams.

INFLUENCE OF CALCIUM AND PHOSPHORUS ON BONE-STRENGTH OF SPENT HENS

ABSTRACT The effects of preconditioning, calcium and phosphorus levels, body weight, and bone geometry on the ultimate shear force and shear stress of the tibia, humerus, and radius were investigated. The shear breaking force and stress of the bones were not affected by increasing the levels of calcium and phosphorus during the last eight weeks of production nor affected by freezing and thawing before testing. The study showed that body weight could not be used as a means or predicting bone strength using a linear regression model. It was observed that bone wall thickness increased with bone breaking force and stress. Birds that did not lay for three or more weeks prior to the end of the production period had higher bone strengths than the egg producing birds.

Investigation of Concrete Haunched T‐Beams under Shear

Haunched beams are used in building construction for architectural and sometimes economical reasons. The American and British codes do not give any formulas for the design of haunched beams under shear. However, the German DIN code and some other European codes give a formula for calculating the equivalent shear stress. A formula is proposed by the writer, which gives the ultimate shear force of reinforced‐concrete haunched beams under shear in terms of concrete strength, stirrups contribution, and dowel action. The proposed formula is a modification of the American Concrete Institute (ACI) code expression for shear design. The modification takes into account the angle of haunch inclination and the dowel contribution. Ten beams of T‐cross section and different haunch inclinations were tested, and analyzed using the proposed formula to test its suitability for each beam. The correlation of results was satisfactory.

Torsional Strength of R/C Beams Containing Rectangular Openings

A method for predicting the torsional strength of a reinforced concrete beam containing a rectangular opening is developed using the principles of limit analysis. A simple yield criterion for yielding under combined bending and torsion is employed. The applicability of the method is limited to openings in which the chords are subjected to predominant bending and torsion, while the shear force at collapse is less than 2/3 of the ultimate shear force. Such openings are characteristically long, and a suitable length parameter to use is the ratio of ultimate bending moment to ultimate shear force of chords. The proposed method is easier to apply than other available methods because it requires only some hand calculations beyond the computation of ultimate values of bending moment, torsion, and shear force of the chords using standard methods. Comparison with available test results shows that the proposed method provides consistently good predictions.

Effect of body size and cage profile on the shear strength of bones of caged layers.

The effects of body size and cage profile on the shear strength of bones from caged layers aged 72 weeks were studied. Bones tested included the radius, ulna, humerus, femur, and tibiotarsus. The ultimate shear force of the femur, tibia, and humerus all increased as body size increased (P less than 0.01). The wing bones of birds housed in high profile cages had higher shear breaking loads than birds housed in low profile cages. The ultimate shear stresses of the bones were not affected by body size or cage profile. The radius had the highest shear stress (29.2 MPa), followed in descending order by the ulna (19.1 MPa), tibiotarsus, humerus (11.4 MPa) and femur (11.3 MPa).

RELATION BETWEEN ISOMETRIC TENSION, POSTMORTEM pH DECLINE AND TENDERNESS OF POULTRY BREAST MEAT

Postmortem changes in isometric tension, pH and shear force of poultry breast meat were studied to determine the relation between rigor contraction and tenderness. Strips of pectoralis major muscle immersed in isotonic saline solution held at 25°C developed measurable tension when their pH dropped to 6.1–6.3. The tension gradually increased until the pH dropped to a final value of 5.5–5.8, then started to decline. Muscle cooked at the start of tension development had the highest shear force. After that the shear force of the cooked meat gradually declined to a minimum value. The results indicate a high correlation (r=0.97) between ultimate shear force and degree of maximum tension developed during rigor.