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Questions and Answers
The strength of a structural element is the maximum internal force which it can withstand. This depends on both the strength of the constituent material and the size and shape of its ______.
The strength of a structural element is the maximum internal force which it can withstand. This depends on both the strength of the constituent material and the size and shape of its ______.
cross section
The ultimate strength of the element is reached when the stress level exceeds the failure stress of the ______.
The ultimate strength of the element is reached when the stress level exceeds the failure stress of the ______.
material
Several different types of stress can occur in a structural element depending on the direction of the load which is applied in relation to its principal ______.
Several different types of stress can occur in a structural element depending on the direction of the load which is applied in relation to its principal ______.
dimension
If the load is coincident with the principal axis of the element, it causes axial internal force and produces axial stress called normal or direct ______.
If the load is coincident with the principal axis of the element, it causes axial internal force and produces axial stress called normal or direct ______.
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The stress that is perpendicular or normal to the cross-section of the element is called normal or direct stress (designated as ______) at that point.
The stress that is perpendicular or normal to the cross-section of the element is called normal or direct stress (designated as ______) at that point.
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The axial stress in an element is uniformly distributed across a cross section and is calculated from the following equations. P / A = ______; where σa = axial stress, P = axial force.
The axial stress in an element is uniformly distributed across a cross section and is calculated from the following equations. P / A = ______; where σa = axial stress, P = axial force.
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Wood is often assumed to be an ______ material with the three principal elasticity directions coinciding with the longitudinal, radial, and tangential directions in the tree.
Wood is often assumed to be an ______ material with the three principal elasticity directions coinciding with the longitudinal, radial, and tangential directions in the tree.
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The growth of trees is by the addition of cells under the ______, at the ends of branches and at the roots.
The growth of trees is by the addition of cells under the ______, at the ends of branches and at the roots.
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The thickness and structural characteristics of the new cell layer depend upon many factors such as temperature, ______, and species.
The thickness and structural characteristics of the new cell layer depend upon many factors such as temperature, ______, and species.
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Most cells are oriental along the ______ axis of the tree while fewer cells develop radially and usually none tangentially.
Most cells are oriental along the ______ axis of the tree while fewer cells develop radially and usually none tangentially.
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The addition of cells occurs, overall, in a ______ manner and creates the grain appearance in wood.
The addition of cells occurs, overall, in a ______ manner and creates the grain appearance in wood.
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In estimating the strength properties of some woods, the number of annual rings per inch is used as a partial ______.
In estimating the strength properties of some woods, the number of annual rings per inch is used as a partial ______.
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The longitudinal centroidal axis of the beam is also known as the neutral ______
The longitudinal centroidal axis of the beam is also known as the neutral ______
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In the bending process, some of the longitudinal fibres are ______
In the bending process, some of the longitudinal fibres are ______
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The unstrained middle surface of the beam is known as the neutral ______
The unstrained middle surface of the beam is known as the neutral ______
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Sections AB and FD are the ends of the small element, and they are parallel to each other when the beam is in an ______ condition
Sections AB and FD are the ends of the small element, and they are parallel to each other when the beam is in an ______ condition
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Strains due to bending increase with increasing distance from the neutral ______
Strains due to bending increase with increasing distance from the neutral ______
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The fibre HJ is parallel to the longitudinal C-z axis, and is at a distance y from the neutral surface on the ______ side of the beam
The fibre HJ is parallel to the longitudinal C-z axis, and is at a distance y from the neutral surface on the ______ side of the beam
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Equation (4.7) is known as the Fundamental Equation of Elastic ______ and is very important in the analysis of bending stress.
Equation (4.7) is known as the Fundamental Equation of Elastic ______ and is very important in the analysis of bending stress.
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The magnitude of the bending stress varies within each cross-section from maximum stresses in tension and compression in the extreme fibres on opposite sides of the cross-section, to a minimum stress in the centre (at the ______) where the stress changes from compression to tension.
The magnitude of the bending stress varies within each cross-section from maximum stresses in tension and compression in the extreme fibres on opposite sides of the cross-section, to a minimum stress in the centre (at the ______) where the stress changes from compression to tension.
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It may also vary between cross-sections due to variation in the bending moment along the ______.
It may also vary between cross-sections due to variation in the bending moment along the ______.
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Distribution of elastic bending stress on a beam cross-section ABCD illustrates the distribution of bending stress on a cross-section of a beam element carrying a bending-type ______.
Distribution of elastic bending stress on a beam cross-section ABCD illustrates the distribution of bending stress on a cross-section of a beam element carrying a bending-type ______.
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The deflected shape of the compressive stress occurs on the inside of the curve (upper half of the cross-section) and the tensile stress on the outside of the ______.
The deflected shape of the compressive stress occurs on the inside of the curve (upper half of the cross-section) and the tensile stress on the outside of the ______.
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Shear force and shear stress are not ______.
Shear force and shear stress are not ______.
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The normal stress on the principal plane is termed as the principal stress. The principal stress is obtained by differentiating Equation (3.1) with respect to angle and equating to zero to obtain 2 xy (3.3) tan 2 p ________________ where θp is the angle of the normal to the principal plane.
The normal stress on the principal plane is termed as the principal stress. The principal stress is obtained by differentiating Equation (3.1) with respect to angle and equating to zero to obtain 2 xy (3.3) tan 2 p ________________ where θp is the angle of the normal to the principal plane.
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The value of stresses on this plane is obtained by defining the sine and cosine of angle 2p with reference to Equation (3.3) and substituting in Equation (3.1) to arrive at 22 x y (3.4) 1 ( x y ) 2 4 2xy 2 2. This equation provides two normal stress components namely ________________ at the point concerned in 2-dimension (1 2).
The value of stresses on this plane is obtained by defining the sine and cosine of angle 2p with reference to Equation (3.3) and substituting in Equation (3.1) to arrive at 22 x y (3.4) 1 ( x y ) 2 4 2xy 2 2. This equation provides two normal stress components namely ________________ at the point concerned in 2-dimension (1 2).
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In a similar manner, the maximum shear stress is derived by differentiating Equation (3.2) with respect to the angle and equating to zero, we have x y (3.5) tan 2 s ________________.
In a similar manner, the maximum shear stress is derived by differentiating Equation (3.2) with respect to the angle and equating to zero, we have x y (3.5) tan 2 s ________________.
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Comparing Equation (3.5) with (3.3), we observe that tan 2 s tan 2 p ________________.
Comparing Equation (3.5) with (3.3), we observe that tan 2 s tan 2 p ________________.
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This implies that the angle differs by 90o. Therefore the angle of the normals to the planes differs by ________________.
This implies that the angle differs by 90o. Therefore the angle of the normals to the planes differs by ________________.
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The practical implication of this is the development of cracks at window and door openings which always extend at an angle of ________________.
The practical implication of this is the development of cracks at window and door openings which always extend at an angle of ________________.
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