Support Tube Dynamic Analysis

• KEK’s ANSYS simulation– model details– Single Point Response Spectrum analysis

• SUGGESTED improvements– beam model– Harmonic Response Analysis– Random Analysis– Transient Dynamic Analysis (time domain)

E. Doyle 12/6/99

KEK model constraints

horiz rotations free, all other d.o.f. fixed

Four freq/displacement points used in KEK SPRS analysis

- analysis of max response to transient event

- damping accounted for in response curve

Beam Model - simply supported

more efficient than shell model

Beam Model vs. Shell Model

• Natural frequencies in Hz

Mode# KEK SLACvert 1 61.7 62.1

2 70.0 78.8horiz 1 61.9 74.2

2 70.2 91.2

Beam Model - cantilever

Responses of Concern

• Differential motion between Q1 magnets• Resulting from

– non-uniform ground motion at two ends– structure asymmetry

• ANSYS can be used to explore these– tube support dynamics– benefit from joining two cantilevers

(creation of common modes)

Excitation Modes of Concern

• Harmonic - cultural sources– Harmonic Response Analysis

• Random - natural and cultural sources– Random PSD (power spectral density)– Transient Analysis (time domain)

Harmonic Analysis

• Sinusoidal excitation at specified ampl & freq• Response at magnet mount points

• Combine responses at all frequencies of interest

Harmonic analysis - vert base motion, unit amplitude

Different damping for the two beams

Random Vibration Analysis

• Input PSD of base motion

• Result is PSD response at each magnet

• how to interpret?

Absolute PSD Response

( 1m2/hz flat input)

--------- FREQUENCY

PSD Response relative to base motion

--------- FREQUENCY

Transient Dynamic Analysis

• Input sampled ground motion (time domain)• Response is motion in time domain• Combine in time domain (outside ANSYS)• Generate cross correlation function (outside ANSYS)