# Design of Steel Structures Questions and Answers – Angles Under Tension and Factors affecting Strength

This set of Design of Steel Structures Quiz focuses on “Angles Under Tension and Factors affecting Strength”.

1. Which of the following is not true for angles as tension members?
a) Angles if axially loaded through centroid can be designed as plates
b) Angles connected to gusset plates by welding or bolting only through one of the two legs results in eccentric loading
c) When load is applied by connecting only one leg of member, there is shear lag at the end connection
d) When angles are connected to gusset plates by welding or bolting only through one of the two legs resulting in eccentric loading, there is a uniform stress distribution over cross section.

Explanation: Angles if axially loaded through centroid can be designed as plates. Angles connected to gusset plates by welding or bolting only through one of the two legs results in eccentric loading, causing non-uniform stress distribution over cross section. When load is applied by connecting only one leg of member, there is shear lag at the end connection.

2. Which of the following is true statement?
a) thickness of angle has no significant influence on member strength
b) net section efficiency is lower when long leg of angle is connected rather than short leg
c) when length of connection decreases, the tensile strength increases
d) effect of gusset plate thickness on ultimate tensile strength is significant

Explanation: (i) The effect of gusset plate thickness on ultimate tensile strength is not significant, (ii) the thickness of angle has no significant influence on member strength, (iii) the net section efficiency is higher(7-10%) when long leg of angle is connected rather than short leg, (iv) when length of connection increases, the tensile strength increases upto four bolts and effect of any further increase in number of bolts on tensile strength of member is not significant.

3. The additional factor to be added for angles for design strength of tension member corresponding to net section rupture is given by :
a) βAg0fyγm0
b) βAg0fym0
c) βAg0γm0
d) βAg0/fyγm0

Explanation: The design strength of angle section governed by tearing at net section is given by Tdn = (0.9Ancfum1) + βAg0fym0 , where Anc = net area of connected leg, Ag0 = gross area of outstanding leg, fu = ultimate strength of material, γm1 = partial safety factor for failure due to rupture of cross section = 1.25, γm0 = partial safety factor for failure in tension by yielding = 1.10.

4. The constant β in βAg0fym0 for tensile strength of angle section does not depend on :
a) area of unconnected leg
b) size of outstanding leg
c) ultimate stress of material
d) thickness of outstanding leg

Explanation: β = 1.4 – 0.076[(bs/Lc)(w/t)(fy/fu)] , where fu and fy are ultimate and yield stress of material, w and t are size and thickness of outstanding leg respectively, bs is the shear distance from edge of outstanding leg to nearest line of fasteners, Lc is the length of end connection measured from centre of first bolt hole to centre of last bolt hole in the end connection.

5. Which of the following is correct?
a) β ≥ fuγm0/fyγm1
b) β ≥ fuγm1/fy γm0
c) β ≤ fuγm0/fyγm1
d) β ≤ fuγm1/fy γm0

Explanation: Tdn = (0.9Ancfum1) + βAg0fym0, where β = 1.4 – 0.076[(bs/Lc)(w/t)(fy/fu)] and β ≤ fuγm0/fyγm1, β ≥ 0.7.
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6. What is the maximum value of β in βAg0fym0 for tensile strength of angle section?
a) 1.2
b) 0.9
c) 1.4
d) 0.7

Explanation: Tdn = (0.9Ancfum1) + βAg0fym0, where β = 1.4 – 0.076[(bs/Lc)(w/t)(fy/fu)] and β ≥ 0.7.

7. What is the value of partial factor of safety for material α for preliminary design for angle section as per IS code for three bolts in connection?
a) 0.6
b) 0.7
c) 0.8
d) 1.0

Explanation: As per IS code, the equation for preliminary design of angle tension member with partial factor of safety for material is given by Tdn = αAnfym1, where α = 0.6 for one or two bolts, 0.7 for two bolts, 0.8 for four or more bolts in the end connection or equivalent weld length.

8. Which of the following statement is correct?
a) strength of members with punched holes is less than members with drilled holes
b) strength of members with drilled holes is less than members with punched holes
c) strength of members with punched holes is greater than members with drilled holes
d) strength of members with punched holes is equal to members with drilled holes

Explanation: Strength of members with punched holes may be 10-15% less than the members with drilled holes. This is due to strain hardening effect of material around punched holes and consequent loss of ductility.

9. The presence of holes _____ the strength of tension member
a) does not affect
b) improves
c) reduces
d) doubles

Explanation: The bolt holes reduce the area of cross section available to carry tension and hence reduce the strength of tension member.

10. Staggering of holes __________ the load carrying capacity of tension member
a) reduces
b) improves
c) does not affect
d) halves

Explanation: Staggering of holes improves the load carrying capacity of tension member for given number of bolts. The failure paths may occur along sections normal to axis of member, or they may include zigzag sections when more than one bolt hole is present and staggering of holes may help to make the net area minimum.

11. The actual failure mode in bearing depends on
a) length of metal plate
b) length of bolt
c) hole diameter
d) bolt diameter

Explanation: The actual failure mode in bearing depends on end distance, bolt diameter and thickness of the connected material.

12. The shear lag effect _____ with increase in connection length
a) increases
b) reduces
c) does not change
d) doubles

Explanation: The shear lag effect increases with increase in connection length. The shear lag reduces the effectiveness of component plates of tension member that are not connected directly to gusset plate.

13. Which of the following statement is correct?
a) increase in ductility reduces strength of member
b) reduction in ductility increases strength of member
c) increase in ductility does not affect strength of member
d) reduction in ductility reduces strength of member

Explanation: Reduction in ductility tends to reduce strength of member. An increase in ductility tends to increase net section strength by allowing better plastic redistribution of stress concentration over cross section.

14. Which of the following statement is true regarding residual stresses?
a) residual stress result in local early strain hardening
b) it increase plastic range of member
c) it is not important when fatigue is involved
d) it improves strength of member

Explanation: Residual stress result in local early strain hardening and reduce plastic range of member. Residual stresses have no consequences with respect to static strength of member, they can be important if fatigue is involved.

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