Chpt 3 Flashcards
A ___ is defined as any effect that a structure must resist
Load
The impact effect the wind has on a surface. This force may be reduced by streamlining the surfaces encountered.
Direct pressure
When wind encounters an object, it’s fluid nature causes it to flow around the object. This exerts a drag effect on the object.
Aerodynamic drag
A suction effect produced on the downwind side of the building resulting in an outward pressure
Negative pressure
A back and fourth effect due to variations in the velocity of the wind.
Rocking effects
Wind passing over a surface such as a roof may cause vibration of the surface depending on the velocity of the wind and the harmonic characteristics of the surface
Vibration
The tendency of wind to dislodge objects from a building j
Clean off effect
The ____ noted above is of particular concern where a building has projections such as canopies and parapets
Clean off effect
The vibrational motion of the surface subjects buildings to forces known as ____ that can be very destructive as history shows
Seismic forces
Are produced in a structural member when it is twisted
Torsional forces
Are movements of relatively larger amplitude resulting from a small force applied at the natural frequency of a structure
Resonant forces
The shifting of the earths surface can also produce forces that are either ______in nature
Torsional or resonant
Occurs where the soil is of a loose, sandy nature and is saturated with water.
Soil liquefaction
The basic concept of ____ is to isolate the building from the horizontal movement of the earths surface
Base isolation
Create a layer between the building and the foundation, which has low horizontal stiffness
Elastomeric bearings
Make use of special plates sliding on each other
Sliding systems
These systems isolate the building from the horizontal shear force created by an earthquake
Sliding systems
Exerts a horizontal pressure against a foundation
Soil
The pressure exerted by the soil against the foundation is known as the
Active soil pressure
The force of the foundation against the soil is known as the
Passive soil pressure
Buildings can also be provided with ____ to control building motion
Damping mechanisms
Are typically installed at the connections between columns and beams, and they absorb energy as the structure moves
Damping mechanisms
A ____ is the weight of any permanent part of the building
Dead load
A ____ is any load that is not fixed or permanent
Live load
Is one that is applied at one point or over a small area
Concentrated load
Water from fire fighting operations can add an additional _____
Live load
A stream of water discharging 250 gpm introduces ______ of water per minute
2082 pounds of water per minute
A water depth of 3 inches will impose a load of ___ per square foot
20.8 pounds
Are loads that are steady or are applied gradually
Static loads
Are loads that involve motion
Dynamic loads
When the support provided by a structural system is equal to the applied loads, a condition known as ____ exists
Equilibrium
The forces that resist the applied loads are known as
Reactions
A beam that is supported at one end is known as a
Cantilever beam
Tends to pull the material apart
Tension
Tends to squeeze the material
Compression
Tends to slide one plane of a material past an adjacent plane
Shear
The magnitude of the interior forces that occur in structural members is evaluated by a quantity known as
Stress
Can also be classified as axial, eccentric, or torsional
Exterior loads
An ____ is a load applied to the center of the cross section of a structural member and perpendicular to that cross section
Axial load
An ___ is a load that is perpendicular to the cross section of the structural member but does not pass through the center of the cross section.
Eccentric load
A ___ is offset from the center of the cross section of the structural member and at an angle to or in the same plane as the cross section.
Torsional load
A ____ produces a twisting effect that creates shear stresses in a material
Torsional load
A ___ is a structural member that can carry loads perpendicular to its longitudal dimension
Beam
The primary design consideration of____ is their ability to resist bending from the applied loads
Beams
At the middle of the beam, a point known as the ____, the tension and compression stresses are actually zero
Neutral axis
Are structural members designed to support an axial compressive load.
Columns
An ___ is a curved structural member in which the interior stresses are primarily compressive
Arch
Can be thought of as flexible structural members that can be used to support roofs, brace tents, and restrain pneumatic structures
Cables
Although cables can be used in applications where they are essentially straight, a cable used to support loads over a distance will assume the shape of a
Parabola
Are framed structural units made up of a group of triangles in one plane
Trusses
The top members of a truss are called the
Top chords
The bottom members of a truss are called
Bottom chords
Lightweight wood or metal trusses, known as _____, have become very common in floor construction, taking the place of solid joists
Truss joists
Are truss structures that are developed in three dimensions
Space frames
A common method of construction uses the walls of the building to support spanning elements such as beams, trusses, and precast concrete slabs. These are appropriately known as______structures
Bearing wall structures
Uses a series of vertical elements to support horizontal elements that are subject to traverse loads
Post and beam
Typical dimensions for the posts are_____ when supporting roofs only
6x8 inches post and beam construction
