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What value of scale factor should I use to define a time-history load case?

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1. In the time-history definition, what is Format Type? Also, which option should be used?
2. In the time-history load case, what is Arrival Time? Does this imply that the segment at the beginning of the time-history record may be neglected?

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1. Format Type options indicate how data is presented in the time-history function text file.
   
   
   • Free Format is applied when spaces or tabs separate the data.
   • Fixed Format is applied when data is not separated by spaces or tabs. In this case, the number of Characters per Item should be specified in the edit box. Also, the Number of Prefix Characters should be specified under Function File. The software begins reading data after skipping this many spaces.
2. Arrival Time is the time at which a load assignment begins. This value may be positive, negative, or zero. Time-history analysis always begins at time zero for a given load case. Therefore, when a negative arrival time is specified for a given load assignment, any portion of the record which occurs before time zero is ignored. For example, an arrival time of -5sec will neglect the first 5sec of the input function. Arrival time may also be useful when staggering the application of ground motion in the global X and Y directions.

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Answer: Time-history results may be displayed at each time step by selecting the appropriate response quantity through Display > Show Tables, then by selecting Modify/Show Options, as shown in Figure 1:

Figure 1 - Choose Tables for Display

Direct History Results should then be changed from Envelopes to Step-by-Step, as shown in Figure 2:

Figure 2 - Output Options