When performing static analysis in Caesar II, are there any tips regarding the combination of operating conditions?

Well, let me explain my approach and then we can discuss it together. Taking the calculation of wind load in a certain direction as an example: Suppose there is only one normal operating condition, which is defined as 1, (OPE) W+T1+P1. The installation condition is 2, (SUS) W+P1. Then there’s a combined operating condition, 3, (OCC) W+T1+P1+WIN1. We also need to consider a combination of the installation condition and wind load: 4, (OCC) W+P1+WIN1. This leads to another condition involving WIN1, namely 5, (OCC) L5=L3-L1. Additionally, there’s the condition related to thermal stress: 6, (EXP) L6=L1-L2. In total, there are 6 such conditions. 1. (OPE) W+T1+P1 2. (SUS) W+P1 3. (OCC) W+T1+P1+WIN1 4. (OCC) W+P1+WIN1 5. (OCC) L5=L3-L1 6. (EXP) L6=L1-L2. Once, when calculating seismic loads according to the design specifications of a foreign company, it was done as follows: Taking the calculation of seismic loads in a certain direction as an example, assuming there is only one normal operating condition, which is designated as 1. (OPE) W+T1+P1; the installation condition is 2. (SUS) W+P1. Then there is a combined operating condition, namely 3. (OCC) W+T1+P1+U1. It is also necessary to consider a combination of the installation condition and wind load, resulting in 4. (OCC) W+P1+U1. According to these design specifications, the condition for U1 is 5. (OCC) L5=L4-L2, rather than L5=L3-L1. Additionally, there is a thermal stress condition: 6. (EXP) L6=L1-L2. In total, six conditions need to be considered. 1, (OPE) W+T1+P1 2, (SUS) W+P1 3, (OCC) W+T1+P1+U1 4, (OCC) W+P1+U1 5, (OCC) L5=L4-L2 6, (EXP) L6=L1-L2

There are a total of 6 operating conditions. 1. (OPE) W+T1+P1 2. (SUS) W+P1 3. (OCC) W+T1+P1+WIN1 4. (OCC) W+P1+WIN1 5. (OCC) L5=L3-L1 6. (EXP) L6=L1-L2 Which of the above are the operating conditions for checking stress?

Thank you for Spidi’s reply. Personally, I think your combination is more intuitive. This is how our company combines them (taking wind load as an example): 1. (OPE) W+T1+P1 – Installation condition; 2. (SUS) W+P1 – There is then a combined operating condition; 3. (OCC) W+T1+P1+WIN1 (the previous elements remain the same); 4. (OCC) L4=L3-L1; 5. (OCC) L5=L2+L4; 6. (EXP) L6=L1-L2. The difference lies in the combination of installation condition and wind load. I asked why WIN1 isn’t calculated directly by addition, rather than using the value from point 4. The answer was that calculating WIN1 in point 4 takes into account the non-linearity of constraints, whereas directly entering WIN1 does not. I understand that this makes a difference, but it still doesn’t explain why it isn’t calculated by direct addition. Additionally, how are these various operating conditions combined (algebraically? vectorially?). And why?

The stress values to be checked under OCC conditions are: 1. (OPE)W+T1+P1; 2. (SUS)W+P1; 3. (OCC)W+T1+P1+WIN1; 4. (OCC)W+P1+WIN1; 5. (OCC)L5=L3-L1; 6. (EXP)L6=L1-L2. The combinations 4, (OCC)W+P1+WIN1, and 5, (OCC)L5=L3-L1, should be calculated as vector sums. After discussing with colleagues about how to obtain pure WIN1 or U1 from these combinations, no definite conclusion was reached – different companies use different methods. In the end, it was decided that it would be reasonable to first calculate L3-L1 to get pure WIN1 or U1, and then compare that result with L3-L1+W+P1. As you said, this order of combination takes into account the non-linearity of the constraints. I figured these things out on my own; it would be great if someone could give me a standard answer.

4, (OCC) W+P1+WIN1. May I ask, when you checked the stress using the method mentioned in point 4 above (assuming B31.3), did the foreign party or any THIRD PARTY raise any objections? This post was last edited by ssmith2007 on 2007-12-26 at 16:33

4,(OCC) W+P1+WIN1 Well, this was my first time dealing with wind loads and seismic loads; I looked into the results from foreign reports, and since they had performed verification, I did the same. In B31.3, no verification is required if it isn’t used: L

It’s not that verification isn’t necessary; for details, please refer to B31.3 302.3.6 Limits of Calculated Stresses due to Occasional Loads. This post was last edited by ssmith2007 on 2007-12-26 at 18:43.]

What kind of combination is a scalar? We use a scalar when combining L2+L5(L3-L1+W+P1)OCC – why do we use this approach?

For the scalar value, you can find it by using caesarii F1; when performing stress checks, the values are added together. For example, if L2=3 and L5=4, then L2+L5=7. The scalar value for this combination follows the b31.3 standard – but other standards may vary; the specific way of combining values depends on the requirements of each standard. Last edited by ssmith2007 on 2007-12-28 at 13:08.]

My mentor also told me that when calculating seismic loads, they should not be combined with temperature effects; work stops during an earthquake. As Spidi mentioned, the design specification for condition U1 is: 5, (OCC) L5 = L4 – L2, rather than L5 = L3 – L1. However, the seismic loads we usually consider take into account accelerations in both directions – there are two components in the uniformly distributed load, and both need to be calculated. W+P1+U1 W+P1+U2 W+P1 L1-L3 OCC L2-L3 OCC

Changes in load distribution due to temperature need to be taken into account. As for shutting down operations during earthquakes, many earthquakes occur suddenly... and the temperature doesn’t drop to room temperature immediately either. It is generally recommended that, in the presence of different operating conditions, the maximum value of the seismic loads assigned under each condition be used. However, if the temperature changes are not significant, it is acceptable to ignore temperature effects. Last edited by ssmith2007 on 2007-12-28 13:06.]

In the specifications, seismic conditions are combined with those caused by sustained loads. Is there any accurate and authoritative definition of seismic conditions? How should they be defined?