This set of Earthquake Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Theory of Seismic Pickups”.
1. Which disease occurs because of adverse effects of vibrations?
a) Cholera
b) Dengue
c) White-finger
d) Beriberi
View Answer
Explanation: White-finger is the disease caused by adverse effects of vibration on human beings. The nerves in the fingers are damaged permanently which results in loss of touch sensitivity. Very small insignificant vibrations can also excite the resonant frequencies of many structural parts and be amplified into major noise or vibration sources.
2. Which of the following is used to measure the vibration of the ground?
a) Odometer
b) Speedometer
c) Electrometer
d) Transducer
View Answer
Explanation: The seismic transducer, also known as a seismic pickup, is employed to gauge ground vibrations. It comprises two primary components: the displacement transducer and the spring-mass damper. Following the analysis of the data collected by this device, the vibrational characteristics are deduced.
3. Find the natural frequency of oscillator, if the tuning ratio (η) is 1.5 and frequency of base motion (ω) is 20 rad/sec?
a) 30 rad/sec
b) 13.33 rad/sec
c) 45 rad/sec
d) 8.89 rad/sec
View Answer
Explanation: Given,
Tuning ratio (η) = 1.5
Frequency of base motion (ω) = 20 rad/sec
Tuning ratio (η) = ω/ωn
ωn = ω/η = 20/1.5
ωn = 13.333 rad/sec
4. What is the ratio of frequency of base motion to the natural frequency of oscillator known as?
a) Tuning ratio
b) Transmissibility ratio
c) Damping ratio
d) Amplification factor
View Answer
Explanation: The ratio of frequency of base motion to the natural frequency of oscillator known as tuning ratio. The transmissibility ratio is defined as the ratio of amplitude of the force transmitted to the support of the amplitude of the applied harmonic force. Damping Ratio is dimensionless parameter which describes how an oscillating or vibrating body comes to rest. Amplification factor is the ratio of maximum displacement of forced vibration to the static deflection due to static force.
5. Vibration spectra is a graph of which of following?
a) Amplitudes vs time period
b) Amplitudes vs frequency
c) Time period vs damping
d) Damping vs tuning ratio
View Answer
Explanation: Vibration spectra is the graph of amplitudes of vibration vs the frequency. When the amplitudes of various responses like displacement, velocity and acceleration of a certain vibration records are measured for the ground motion of various frequencies, the resulting graphs are referred to as vibration spectra.
6. Find the tuning ratio (η), if the natural frequency of oscillator (ωn) is 30 rad/sec and frequency of base motion (ω) is 42 rad/sec?
a) 0.714
b) 1.96
c) 0.51
d) 1.4
View Answer
Explanation: Given,
Frequency of base motion (ω) = 42 rad/sec
Natural frequency of oscillator (ωn) = 30 rad/sec
Tuning ratio (η) = ω/ωn
η = ω/ωn = 42/30
η = 1.4
7. What is the value of frequency ratio (β), if loading frequency is 2π rad/sec and structure’s natural frequency is 3π rad/sec?
a) β = 1.5
b) β = 0.82
c) β = 1.22
d) β = 0.67
View Answer
Explanation: Given,
Loading frequency ωe= 2π rad/sec
Structure’s natural frequency ω = 3π rad/sec
frequency ratio (β) = ωe/ ω = 2π/3π = 0.67
8. For a system with damping ratio (ξ) 5%, determine the number of free vibration cycles (n) required to reduce displacement amplitude to 10% of initial amplitude?
a) 2.12 cycles
b) 3.18 cycles
c) 7.33 cycles
d) 9.54 cycles
View Answer
Explanation: Given,
Damping ratio (ξ) = 5%
A2 = 0.1 A1
Ln (A1/ A2) = 2π*n*ξ
Ln (A1/0.1 A1) = 2π*n*ξ
Ln (10) = 2π*n*0.05
n = 7.33 cycles
9. What are the shapes of the curves of vibration spectra known as?
a) Response shapes
b) Spectral shapes
c) Response spectra
d) Mode shapes
View Answer
Explanation: Vibration spectra is the graph of amplitudes of vibration vs the frequency and the shapes of the curves of vibration spectra are known as spectral shapes. These graphs are used to judge the parameters. It is advantageous to select the parameter which has the flattest vibration spectrum in the frequency range of our interest.
Sanfoundry Global Education & Learning Series – Earthquake Engineering.
To practice all areas of Earthquake Engineering, here is complete set of Multiple Choice Questions and Answers.
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