Terms Flashcards
Stress
The resistance of a body to a load aka internal force and measured in kips
Factor of safety
Ratio of the ultimate strength of material in psi or ski
Strain
The deformation of a material caused by external loads. Tensile loads stretch, and compressive loads shorten.
Section modulus
Is the ratio of a cross sections second moment of area to the distance of the extreme compressive fiber from the neutral axis
Center of gravity
The point at which the mass of a member is concentrated is called what
Shear
Two pushing or pulling adjacent forces, acting close together but not directly opposing each other
Centroid
The actual point at the center of gravity that measurements are taken
Yield strength
is the lowest stress that produces a permanent deformation in a material.
Shear wall
A wall with in-plane rigidity
redundancy
Having the ability to redistribute loads to another part of the structure
lamella
a series of parallel arches, skewed with respect to the building, which intersects another series of skewed arches
bracketed duration
The time between the first and last peaks of motion that exceeds this threshold value of 0.05g
Frequency
Is the inverse of period or the number of cycles that will occur in a second abd is measured in hertz
Response spectrum
A site response spectrum is a graph that plots the maximum response values of acceleration, velocity and displacement against period.
Dynamic amplification
The increase of the structural movement over that of the ground motion
Drift
Deflection of vertical structural members like columns and walls
Eccentricity between the center of mass and the center of resistance
Torsional forces are created in a building by a lack of balance between the location of the resisting elements and the arrangement of the building mass
Soft story
Are less stiff or more flexible than stories above
Weak stories
Have less strength than stories above
P-delta effect
P is the gravity force or weight and delta is the eccentricity or the extent to which the force is offset. All objects that overturn do so as a result of this phenomenon.
Moment of inertia
directly proportional to the amount of deflection. If the deflection is high
Liquefaction
Soil liquefaction describes a phenomenon whereby a saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress, usually earthquake shaking or other sudden change in stress condition, causing it to behave like a liquid.
Resonance
It causes amplification of damage for instance when the buildings period matches the soils period
Slenderness Ratio
The ratio of a structural members unsupported height to its thickness
Space frame
A structural system consisting of trusses in two directions rigidly connected at their intersections
Two way structural slab system
Composed of concrete members usually spaced 24 or 36 inches apart, running in one direction and framing into larger beams
Surcharge
It is the load above the stem in terms of retaining walls
Buttress vs counterfort
Conterfort is in tension while the buttress is in compression
Stub girder system
A steel beam and girder system in which the floor beams sit on top of the main girders, rather than framing into them.
Hertz
One hertz is one cycle per second
Triggers
Events or actions that require owners to seismically retrofit their buildings
Main Wind Force Resisting System
A structural assembly that provides for the overall stability of the building and receives wind loads from more than one surface
How is framing anchor used to resist lateral forces ?
Prevents wind uplift
Movement parallel to the axis of the wall
Forces moving the roof perpendicular to the wall
Bent
A frame is made of a number of columns and beams connected rigidly to each other to resist lateral loads
Bent
A frame is made of a number of columns and beams connected rigidly to each other to resist lateral loads
tack weld
After items to be welded together have been positioned as required, generally, by clamping them on suitable fixtures, tack welds are used as a temporary means to hold the components in the proper location, alignment, and distance apart, until final welding can be completed.
counterfort
A counterfort retaining wall is a cantilever wall with counterforts, or buttresses, attached to the inside face of the wall to further resist lateral thrust.
Schwedler dome
This has ribs extending down from the crown of the dome, rings extending horizontally around the dome, and diagonals extending from intersections between ribs and rings on one horizontal ring to those on the next .
Schwedler dome
This has ribs extending down from the crown of the dome, rings extending horizontally around the dome, and diagonals extending from intersections between ribs and rings on one horizontal ring to those on the next .
Monolithic Beam-Girder System
16-32 ft span
One Way Joist System
50 ft span
Flat Plate System
12-35ft span
Flat Slabs with Drop Panels
Up to 40’ span
Two-Way Joist System
Up to 60’ span Depth 8-28 inches
Exposure Factor (Ce)
This factor depends on the type of terrain and also the roof exposure. The smallest value being an exposed roof and the largest factor being the not subject to direct sun.
Thermal factor (Ct)
This factor considers if a building is unheated and snow may stay on the roof for a long period of time. Most buildings use a factor of 1
Importance factor (I)
This factor considers the importance of the structure to the society. For structures like hospitals the factor is higher than 1. Most buildings use a factor of 1.
Ground Snow Load (pg)
This factor is based on the location and a map by the IBC is given for various locations.
Thermal coefficient of Aluminum
0.0000128
Thermal coefficient of Steel
0.0000065
Thermal coefficient of Concrete
0.0000055
Thermal coefficient of Masonry
0.0000034
Thermal coefficient of Wood
0.0000030
Live Load
The load superimposed by the use and occupancy of the building which excludes wind, dead or seismic loads.
Modified Mercalli Scale
measures the earthquakes intensity
Damping
Due to internal friction and absorbs energy. Dampers generate damping and force a vibrating system to stop quickly.
Basic Wind speed (V)
The wind does correspond to 3-second gust speeds at 33 ft above the ground. The values are measured at airports at various locations across the country.
Wind Stagnation Pressure (qs)
As the wind increases it exerts more pressure on objects.
Exposure Factor (kz)
Exposure B (lowest) urban /surburban: closely spaced obstructions Exposure C (moderate) "country" Exposure D ( largest) shorelines, open water, desert.
Topographic Factor (Kf)
Buildings sited on the upper half of an isolated hill or escarpment are subjected to higher wind pressures than those situated on level ground.
Directionality Factor (Kd)
This factor considers the possibility of max winds flowing from any given direction.
ASD
Allowable Stress Design; service loads
LRFD
Load Resistance Factor Design ; factored loads i.e. 1.2
Richter scale
The amount of energy released in an earthquake
Pressure waves
Cause a relatively small movement in the direction of wave travel
Shear waves
Produce a sideways or up and down motion that shakes the ground in three directions ( most damaging).
Surface waves
Travel at or near the surface and can cause both vertical and horizontal earth movement.
