DATA REDUCTION TECHNIQUE 



WAVEFORM CONSIDERATIONS 



Typical load and displacement traces from the Sanborn 320 and 322 

 strip chart recorders are shown for the case of the open-link chain 

 model in Figures 6 and 7 (fixed pivot anchor with scope-to-depth ratios 

 of 1.1 and 1.3 respectively) and Figure 8 (scope-to-depth ratio of 1.3 

 and excess chain lying on the bottom). Figure 6 represents the shortest 

 scope condition which results in the highest dynamic loads and the most 

 distorted signals, although this distortion is not strong enough to 

 prevent analysis of these data as if they were pure sinusoidal signals. 

 Small amplitude ripples on the signal may be due to pendulus motion 

 of individual links in the chain. 



The load traces shown in Figures 6,7, and 8 do not represent 

 pure horizontal and vertical forces because there are significant 

 interactions between the gages in the two component force dynamometer. 

 Also, inertia loads from the dynamometer itself are present in these 

 traces. Methods for eliminating these interactions and inertia loads 

 from the data analysis are discussed in the next section. 



The load traces for the other models are similar to Figure 6, 7, 

 and 8 but are of generally lower magnitudes. However, under some 

 conditions the load traces are highly distorted in that they show 

 sharp spikes that peak to much higher maximum loads than are observed 

 when the responses are sinusoidal. The following two distinctly 

 different conditions result in distorted loads: 



1. Models with smallest scope-to-depth ratios ( 6 = 1.1) 

 and highest preset trail distances (x = 3.79 feet at 

 U = 0.6 knot) have the highest tensions of any of the 

 models when the slider which drives the line is at the 

 top of its travel. This results in distorted load 

 traces, especially when the amplitude or frequency is 

 increased. An example is illustrated in Figure 9 for 

 for the open-link chain model. 



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