Answer :
The ultimate limit load combination for purlins, given the self-weight of cladding, self-weight of purlin, and wind pressures, is calculated by summing these factors. The maximum negative load combination considering the provided values is -3.865 kPa.
The question involves calculating the ultimate limit load for purlins, including the self-weight of the cladding, the self-weight of the purlin, and varying external and internal wind pressures. To find the ultimate load one must consider all the loads that act on the purlin. Based on the given values, the ultimate load combination is the sum of the self-weight of the cladding, the self-weight of the purlin, and the larger negative difference between external and internal wind pressures. The largest possible internal pressure difference occurs when the external wind pressure is -3.0 kPa and the internal wind pressure is 1.0 kPa. Thus, the calculation for the maximum negative load is:
- Self-weight of cladding: 0.05 kPa
- Self-weight of purlin: 0.1 kPa
- External wind pressure: -3.0 kPa
- Internal wind pressure: 1.0 kPa
The calculation is as follows:
-3.0 kPa (external) - 1.0 kPa (internal) + 0.05 kPa (cladding) + 0.1 kPa (purlin) = -3.865 kPaThis value represents the ultimate limit state load combination for the purlin under the given loading conditions.
The ultimate limit load combination for purlin is is O -3.865 kPa. It is given that: Self-weight of the cladding is 0.05 kPa, Self-weight of the purlin is 0.1 kPa.
External wind pressure is -3.0 k, Pa, Internal wind pressure is 1.0 kPa or -0.5 kPa
To determine the ultimate limit load combination for purlin, first, let's define the characteristic loads as follows:
Dead Load = 0.05 kPa (self-weight of the cladding) + 0.1 kPa (self-weight of the purlin)
= 0.15 kPa
Wind Load = -3.0 kPa (external wind pressure) + 1.0 kPa (internal wind pressure) or
-0.5 kPa (internal wind pressure) = -2.0 kPa or -3.5 kPa
Now, let's compute the ultimate limit load combination: O = 1.2 (Dead Load) + 1.5 (Wind Load)
For Wind Load = -2.0 kPaO
= 1.2 (0.15 kPa) + 1.5 (-2.0 kPa)O
= -3.865 kPa
For Wind Load = -3.5 kPaO = 1.2 (0.15 kPa) + 1.5 (-3.5 kPa)O
= -3.820 kPa
Therefore, the ultimate limit load combination for purlin is O -3.865 kPa (for internal wind pressure of 1.0 kPa) or
O -3.820 kPa (for internal wind pressure of -0.5 kPa).
Therefore, the correct answer is O -3.865 kPa.
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