Partial Safety Factors and Design Loads

Q. Partial safety factor for concrete and steel are 1.5 and 1.15 respectively, because

1. concrete is heterogeneous while steel is homogeneous
2. the control on the quality of concrete is not as good as that of steel
3. concrete is weak in tension
4. voids in concrete are 0.5% while those in steel are 0.15%

Q. Factor of safety is the ratio of

1. tensile stress to working stress
2. compressive stress to working stress
3. bending stress to working stress
4. yield stress to working stress

Q. Combination of partial safety factors for loads under limit state of collapse and limit state of serviceability will be

1. 1.5(DL + LL) or 1.5 (DL +WL) or 1.2(DL + LL) and DL + 0.8 (LL + WL)
2. 1.5(DL + LL) and DL + 0.8 (LL + WL)
3. 1.5(DL + LL) or 1.5 (DL +WL) or 1.2(DL + LL + WL) and 1.0(DL + LL) or 1.0 (DL + WL) or DL + 0.8 (LL + WL)
4. 1.2 ( DL + LL + WL) and 1.0 (DL + LL) or 1.0 (DL + WL) or DL + 0.8 (LL + WL)

Q. A reinforced concrete beam is subjected to the following bending moments:

Dead load - 20 kN-m
Live load - 30 kN-m
Seismic load - 10 kN-m

The design bending moment for limit state of collapse is

1. 60kN-m
2. 75 kN-m
3. 72 kN-m
4. 80 kN-m

Q. The factored loads at the limit state of collapse for DL + LL + WL combinations, according to IS : 456 - 1978 are respectively.

1. 1.5 DL + 1.5 LL, 1.2 DL + 1.2 WL, 1.5 DL + 1.5 LL + 1.5 WL
2. (0.9 or 1.5) DL + 1.5 LL, 1.5 DL + 1.5 WL, 1.2 DL + 1.2 LL + 1.2 WL
3. 1.2 DL + 1.2 LL, 1.5 DL + 1.5 WL, 1.5 DL + 1.5 LL + 1.5 WL
4. 1.5 DL + 1.5 LL, (0.9 or 1.5) DL + 1.5 WL, 1.2 DL + 1.2 LL + 1.2 WL

Q. Consider the following statements:

1. The limit state of collapse is defined as the acceptable limit for the stresses in the materials.
2. Limit state method is one that ensures adequate safety of structure against collapse.
3. In the limit state design method, actual stresses developed at collapse differ considerably from the theoretical values.

Which of these statements is/are correct?

1. 1 and 2
2. 1 and 3
3. 2 and 3
4. None

Q. When assessing the strength of a structure as per the limit state of collapse, the value of partial safety factor for steel is taken as

1. 2.0
2. 1.5
3. 1.15
4. 1.00

Q. The design load for combination of dead and live load is 450 kN. If Live load = 180 kN and wind load = 100 kN , find the design load as per limit state of collapse

1. 450 kN
2. 420 kN
3. 480 kN
4. 330 kN

Q. For avoiding the limit state of collapse, the safety of RC structures is checked for appropriate combination of Dead Load(DL), Imposed Load or Live Load (LL), Wind Load(WL) and Earthquake Load(EL). Which of the following load combinations is not considered?

1. 0.9 DL + 1.5 WL
2. 1.5 DL + 1.5 WL
3. 1.5 DL + 1.5 WL+1.5 EL
4. 1.2 DL + 1.2 LL +1.2 WL

Q. Dead Load = 200 kN
Live Load = 300 kN
Wind Load = 120 kN
Earthquake Load = 180 kN
The Design Load (kN) as per limit state of serviceability is

1. 750
2. 500
3. 816
4. 584