Short Answer questions -S.A.II

                                      

        1.     What is Slope Deflection Method?(Oct/Nov 2010)

          The Slope Deflection  equations gives the moments at end of a member. These are expressed in terms of  the deformations (ie.slopes & displacements).

This method is used for the analysis statically indeterminate beams and rigid frames.

   2.     What are the assumptions used in the slope deflection method?(Oct/Nov 2010)

     1) The method of the structure is linearly elastic.

    2) The structure is loaded within the elastic limit of its material and the principle of superposition is also for the analysis.

   3) The axial displacements and shear displacements are negligible and they are neglected in the analysis.

     4) The flexural deformations (caused by B.M) are only considered.

    3. Explain  Stiffness Factor?(Oct/Nov 2010)

The term ”Stiffness” is defined as the ratio moment of inertia(I) to the length of the member(L).

 It is denoted by ‘K’.

                                        K=I/L

        

    4. State the reasons for the side sway?

   In the rigid portal frames, the side sway occurs due to one of the following cases:-

   1) Eccentric (or) the unsymmetrical loading on the rigid frames.

   2) Unsymmetrical geometry of the frames.

   3) Different boundary conditions of the column.

   4) The cross-section of the members of the frame are not uniform.

   5) Application of horizontal load on the frame (wind, seismic forces etc).

   6) Differential settlement of supports of rigid frames.

   5. What is Moment Distribution method?

     Moment Distribution Method is exactly same as the slope deflection method except the difficulty of solving the simultaneous equations. This was proposed by Prof.Hardy Cross in the year 1930.

 6. What are Carry over moments?

    When the moment ‘M’(balancing moment)is distributed among the members in any  joint ‘A’, all the adjacent joints to A are prevented from rotation. The moment needed to prevent the rotations are called “Carry-over Moments”.

7. What is Carry over Factor(CF)?

   The ratio of the carry over moment to the distribution moment for a particular member is called ”Carry-over Factor”.

    For all prismatic members, the value of CF will be same and equal to ½.

8. What is meant by Distribution Factor?( Oct/Nov 2010)

  The fraction of total moment shared by each member at a joint is called as “Distribution Factor” which is equal to ratio of the stiffness of the member to total stiffness of all the members meeting  at a joint.

                                                 Dij=Kij / ∑Kij

9. State Modified Stiffness Factor?

 The stiffness factor whose far end is hinged in a member will be (¾)*(I/L).

                                  MSF= (3/4)*K

10. What is a Cable?

 In the structural application, the term “Cable” means a flexible tension member.

 These are commonly used to support the suspension bridges as permanent guys for transmission towers, chimneys and building roofs. They carry only the tensile forces.

11. What is meant by Dip?

 The vertical distance from tower top to the lowest point on cable is called as the “Central Dip”. This is also called as “Sag”.  The central dip for the cable will be 1/10 to 1/12.    

12. What is Shape of a cable if it is supported to point loads ? (Oct/Nov 2010)

 Under the point loads, the cable will take the shape of “Funicular Polygon”.

13. What is Shape of a cable if it is supported to U.D.L along the span?

Under the uniformly distributed loads, the cable will take the shape of  "Parabola"

14. What is Shape of a cable due to its self weight?

Under the self weight ,the cable take the shape of "Catenary"
15. State eddy's theorem
The bending moment at any section of an arch is proportional to the vertical intercept between the Linear arch and center line of the Actual arch. 
16. What are the  Assumptions in  portal method ?

1. The points of inflection are located at the mid-height of each column above the first floor. If the base of the column is fixed, the point of inflection is assumed at mid height of the ground floor columns as well; otherwise it is assumed at the hinged column base.

2. Points of inflection occur at mid span of beams.

3. Total horizontal shear at any floor is distributed among the columns of that floor such that the exterior columns carry half the force carried by the inner columns. 

17. What are the  Assumptions in cantilever method ?

1. The points of inflection are located at the mid-height of each column above the first floor. If the base of the column is fixed, the point of inflection is assumed at mid height of the ground floor columns as well; otherwise it is assumed at the hinged column base.

2. Points of inflection occur at mid span of beams.

3. The basic assumption of the method can be stated as “the axial force in the column at any floor is linearly proportional to its distance from the centroid of all the columns at that level.