Lesson 4-5

Question 1

___________ arise from sudden movements in a rupture zone in the Earth’s crust.

Answer 1

Seismic Waves

Question 2

The upper part of the building remains in delay in respect to the foundation moving, due to its _______. This causes strong vibrations of the structure with ___________________ between the structure and the ground and hence large inertial force arise.

Answer 2

mass, resonance phenomena

Question 3

Due to its weight, the soil is overloaded, becoming _______, hence producing change in its behavior.

Answer 3

stiffer

Question 4

Part of the vibrating energy of buildings is released into soil through waves produced by buildings.

Answer 4

Soil Effect

Question 5

The severity of shaking is controlled primarily by two (2) factors:

Answer 5

a. Attenuation of ground motion.
b. Earthquake characteristics

Question 6

The dissipation of seismic energy as seismic waves move through layers of varying soil and rock strata.

Answer 6

Attenuation of ground motion

Question 7

Characterized as the decrease in amplitude of the seismic waves with distance from source. It results from geometric spreading of propagating waves, energy absorption and scattering of waves.

Answer 7

Attenuation of ground motion

Question 8

Other important earthquake measurement parameters are the measured ground motions at the ground surface. These are:

Answer 8

Peak Ground Acceleration (PGA)
Peak Ground Velocity (PGV)
Peak Ground Displacement (PGD)

Question 9

_________________ has become the most popular parameter to denote the measure of an earthquake and has been related to the magnitude through several empirical relationship.

Answer 9

Peak Ground Acceleration (PGA)

Question 10

are essential for describing the important characteristics of strong ground motion in compact, quantitative form.

Answer 10

Ground motion parameters

Question 11

The most common way of describing a ground motion is with

Answer 11

Time history

Question 12

As the PGA value decreases with the epicentral distance, these empirical relationships are also called

Answer 12

attenuation laws

Question 13

refers to the fact that the state of the system and the applied forces do not vary in time; they are time-independent.

Answer 13

Static

Question 14

is the study of systems subject to time-varying applied forces.

Answer 14

Dynamics

Question 15

considered as the study of a body or structure in dynamic equilibrium and the mathematical expression of this equilibrium is the equation of motion.

Answer 15

Structural dynamics

Question 16

expresses the equilibrium of internal and external force terms and the mass inertia and damping effects.

Answer 16

equation of motion

Question 17

______________ involves the second derivative and the damping term the first derivative of the displacement with respect to time.

Answer 17

inertia term

Question 18

second-order differential equation with constant coefficients.

Answer 18

equation of motion

Question 19

All bodies possessing inertia (mass) and elasticity (degree of stiffness) are capable of

Answer 19

vibration

Question 20

a system put out of its equilibrium position and vibrates under the action of forces inherent in the system

Answer 20

Free Vibration

Question 21

a vibration that takes place under the action of external forces.

Answer 21

Forced Vibration

Question 22

Types of Vibration

Answer 22

a. Free, undamped vibration
b. Free, damped vibration
c. Forced, undamped vibration
d. Forced, damped vibration

Question 23

is equal to the number of independent coordinates necessary to describe the motion of a system.

Answer 23

Degree of Freedom (DOF)

Question 24

The time required for the system to complete one cycle of the vibration.

Answer 24

Period

Question 25

The number of cycles per unit time (cycles per second)

Answer 25

Frequency

Question 26

Formulated by estimating an equivalent lateral seismic loads as a fraction of the total system weight.

Answer 26

Static Analysis

Question 27

The fraction is determined from a notional earthquake, which is based on the risk posed by the seismicity of the site and is captured in a single graph known as the

Answer 27

response spectrum

Question 28

The procedure for this analysis models the load effect of earthquakes more accurately by using either a set of specific earthquake ground motion time history records (response time-history analysis procedure) or the effect of same notional earthquake as the equivalent static analysis (the design response spectrum).

Answer 28

Dynamic Analysis

Question 29

a linear or nonlinear mathematical model of the system is used to determine the system response (displacement and accelerations, which are used to determine the internal loading in each member) at each increment of time for a suite of ground motion acceleration time histories.

Answer 29

Response time history analysis procedure

Question 30

uses established methods of structural dynamics to determine system vibration mode shapes and their associated natural periods, which along with the response spectrum are used to establish the maximum structural response.

Answer 30

modal response spectrum analysis procedure

Question 31

• is needed to determine the circular frequency., which once obtained can be used to determine the natural period of vibration of the system.
• defined as the ratio of force (or moment) to
  displacement (or rotation).

Answer 31

STRUCTURAL STIFFNESS, k

Question 32

caused by initial conditions (displacement and velocity) and not by applied force.

Answer 32

Free vibration