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Winching (lowering) of the mass using a constant speed (1ft/sec) of the winch and the associated dynamic effects will be modeled. The dynamic effects will be introduced take place primarily at the beginning and the end of the winching operation when the speed of the winch changes from 0ft/sec to 1ft/sec and vice versa.
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- The qualitative response is the primary focus and therefore no specific dimensions and properties were are shown in Figure 1. If needed, these properties can be obtained directly from the attached model file.
- The cable is not being modeled as moving over the pulleys. Instead, it is directly connected to the pulleys (joints 2 and 3) represented as springs. These springs resist load normal to the cable at the middle point of contact, but not tangentially. There is no consideration of the radius of the pulley.
- Winching (lowering of the mass) is modeled by applying deformation load to the vertical cable. This moves the mass downward. Dynamical behavior of the mass is captured. Dynamics of the cable itself is not, presumably it is insignificant.
- Time history load case "Payout NL" is used to increase this the deformation load of the vertical cable linearly in time, which would correspond to a constant speed of winching. The "Payout NL" load case uses time function "Payout start" at the beginning and the end of the winching to smooth the response to eliminate high frequencies in the results. This corresponds to the behavior of the actual structure for which the winching would start and stop with a gradual increase or decrease of speed.
- Since the model utilizes only cables elements which inherently include P-Delta and displacement effects, it is not necessary to specify these effects in the definition of the "Payout NL" load case.
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