In many cases these misfits span large distances, for example, the macrostresses between reinforcements and concrete in prestressed concrete. Whatever their cause or classification, they originate from misfits ( Fig. They may be categorized by cause (e.g., thermal mismatch stresses), by the scale over which they self-equilibrate (e.g., macro- or microstresses), or according to the methods by which they can be measured. Residual stresses are difficult to assess, because they are self-equilibrating and so, unlike applied stresses, they cannot be calculated from the forces, impulses, and couples experienced by a material, component, or assembly. * This span has single conductor phases (no bundle spacers to be removed). Exposures are totaled for danger areas under each phase of each modeled span assuming either end fails. Note: Total Station Risk is calculated for the whole station per year. K = a coefficient accounting for 53 m spans not modeled explicitly (= 14/6)į = 19.5 - for all lines connected to Middleport TS (230 kV) P i prProbability of Accident (per span).With bundle spacers removed from 53 m spans With bundle spacers present in 53 m spans The mismatch there is primarily due to the unmodeled high-frequency dynamics. Excellent agreements are found in all but the very high frequency range.
The magnitude and phase plots of its transfer functions are compared to the experimental FRF data in Figures 6.3 and 6.4. The final discretetime state-space realization has 10 states. The key identification parameters are given in Table 6.1. The MF parameterization is chosen for the curve-fitting, which is complemented by the ERA method for state-space realization. The experimental FRF is preconditioned to eliminate the second order direct current (dc) zeros from acceleration measurement. The sampling rate is set at 256 Hz, and the frequency resolution is set at 0.125 Hz. For this purpose, a DSPT Siglab spectrum analyzer is used to measure the FRF data. The goal of the identification is to capture accurately the first five pairs of the complex poles of the structure. The accelerations of these floors are selected as the system measurement outputs and are sensed by PCB accelerometers. The system is excited by impulse force produced by a PCB hammer and applied individually at the 16th, 12th, 8th, and 4th floors. The first identification target is a 16-story steel structure model shown in Figure 6.2.
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