This set of Prestressed Concrete Structures Assessment Questions and Answers focuses on “Analysis by Guyon and Magnel”.
1. The length of beam within which the dispersion of prestressing force takes place is known as:
a) Zone of action
b) Zone of transmission
c) Zone of anchorage
d) Zone of tendons
Explanation: The length of beam within which the dispersion of the prestressing force takes place is called as zone of transmission; Guyon has developed design tables for the computation of bursting tension in the end blocks which are based on his earlier mathematical investigations concerning the distribution of stress in end blocks subjected to concentrated loads.
2. The tensile forces developed in the transverse direction to the axis are known as:
a) Bursting forces
b) Concentrated forces
c) Reduced forces
d) Tensioned forces
Explanation: The tensile forces developed in the transverse direction to the axis of concentrated force are called as bursting forces; the concept of symmetrical or equivalent prism for eccentric cables and the method of partitioning for the analysis of stresses developed due to multiple cables have been introduced by Guyon.
3. The adjacent surface to the anchor plate is also subjected to:
a) Compressive forces
b) Tensile forces
c) Transverse forces
Explanation: The adjacent surface to the anchor plate is also subjected to tensile force at the end section and these are called as spalling forces, the eccentric forces and multiple cables, the symmetric prism method may be used, this consists of a prism of concrete of side equal to twice the distance of the prestressing force from the nearest free edge.
4. During zone of transmission prestressing force is applied through the anchor plate at:
Explanation: The prestressing force p is applied through the anchor plate which is placed at the centre of the end beam during zone of transmission, When the forces are arranged such that the resultant of the stress distribution at a distance equal to the depth of the end block coincides with the line of action of the force then the forces are considered to be evenly distributed.
5. Which are formed due to the horizontal, vertical and shear stresses induced at zone of transmission:
Explanation: Due to the horizontal, vertical and shear stresses induced at zone of transmission, trajectories of principle stresses are formed, the line of action of the resultant force is taken as the axis of an equivalent prism of length and depth equal to twice the distance of axis from the free edge or the adjoining equivalent prism.
6. The transmission length is influenced by:
Explanation: The transmission length is influenced by depth of the anchor plate and is taken equal to the depth of beam in general, the transverse stress distribution is computed by using the coefficients under the category of concentrated eccentric force and eccentric shear forces since the coefficients are applicable for forces at interval of one eighth of the prism depth, the end forces have to be replaced by a statically equivalent system of normal and shear forces acting at these regular intervals.
7. The transmission length and bursting forces can be obtained depending on the ratio of:
a) Depth of anchorages
b) Depth of tendons
c) Depth of bond
d) Depth of curve
Explanation: Depending on the ratio of depth of anchor plate to the depth of beam, the transmission length and bursting force can be obtained, the position of zero stresses, maximum transverse stress and its magnitude for the forces which are evenly distributed are computed by using the coefficiants under the category of distributed axial forces. According to guyon, the bursting tenson is expressed as, Fbst = 0.3P(1-(ypo/yo)0.58, p = anchorage force, ypo/yo = distribution ratio.
8. In general the transmission length and depth of beam are taken as:
c) Less than 1
d) More than 1
Explanation: Generally, the transmission length is taken as equal to the depth of beam and bursting forces are considered in case of transmission length, when it is not possible to arrange the end forces evenly, Guyon recommended that transverse tensile stresses be investigated along successive resultants, such as resultant of all forces, resultant of smaller groups of forces, lines of action of individual forces.
9. The bursting force with depth of beam d’ and the depth of anchor plate d is given by:
Explanation: The bursting force with depth of beam d’ and the depth of anchor plate d is given by:
Pb = 0.3P (1-d’/d), the distribution of bursting stress for d’/d = 0.8 and d’/d = 0.5 are given as distance along the transmission line.
10. The d’/d value for 0.42d is:
Explanation: The distribution of bursting stresses d’/d = 0.8 and for d’/d = 0.5 are shown below:
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