Building Systems, Materials, & Assemblies Flashcards
What is the internal resistance to an external force?
Stress. (Tension, Compression, Shear, Torsion, Bending, Combined Stresses)
Stress f = total force P / total area A
What are the three basic types of stress?
Tension, compression, and shear
What is tension?
Tension is stress in which the particles of the member tend to pull a part under load.
What is compression?
Compression is stress in which the particles of the member are pushed together and the member tends to shorten.
What is shear?
Shear is stress in which the particles of a member slide past one another.
Coefficient of Expansion
Thermal Stress
plastic, acrylic = 0.0000450 aluminum = 0.0000128 in/in-F bronze = 0.0000101 structural steel = 0.0000065 concrete = 0.0000055 glass = 0.0000051 marble = 0.0000045 brick = 0.0000034
What is the deformation of a material caused by external forces?
Strain (e)
strain (e) = total strain e / original length L
What is Hooke’s law?
As a force is applied to a material, the deformation (strain) is directly proportional to the stress, up to a certain point.
Elastic Limit
On a stress-strain graph, the point at which the material will experience deformation faster. (Prior to to this point stress and strain are directly proportional.)
Ultimate Strength
The failing point of a given material.
Yield Point
On a stress-strain graph, the point at which the material begins to deform with minimal increase in load (stress).
Modulus of Elasticity
A stress to strain ratio of a given material. €
e = PL/AE
Total strain (deformation) of a material under a given load.
A = total area P = total force L = original length e = total strain
Moment
The tendency of a force to cause rotation about a point.
Btu
The amount of heat required to raise the temperature of 1 lbm of water 1dF
Joule (J)
A measure of energy, one joule is a newton meter, or the force of 1 N acting through a distance of 1 m. One joule is 1/4.184 the amount of heat required to raise one gram of water by 1dC. One Btu equals about 1.055 kJ.
Coefficient of heat transmission
The overall rate of eight blow through any combination of materials, including air spaces and air layers on the interior and exterior of a building assembly.
Conductance
The number of British thermal units per hour that passes through 1 ft.² of homogeneous material of a given thickness when the temperature differential 1°F.
Dew Point
The temperature at which water vapor in the air becomes saturated and begins to condense two drops of water.
Dry-bulb temperature
The temperature of the air-water mixture as measured with a standard dry-bulb thermometer.
Enthalpy
The total heat in a substance, including latent heat and sensible heat.
Latent Heat
Heat that causes a change of state of a substance, such as the heat required to change water into steam. The amount of heat required to change the state of a substance is much greater than the heat required to raise the temperature of the substance (sensible heat).
The average value of latent heat per lb of moisture is 1061 Btu (1120 kJ).
Resistance
The number of hours needed for one Btu to pass through one square foot of material or assembly of a given thickness when the temperature differential is 1°F. It is the reciprocal of conductance.
Sensible heat
Heat that causes a change in temperature of a substance but not a change of state. For example, the sensible heat required to raise the temperature of 1 lbm of water from 50°F to 100°F is 50 Btu (53 kJ).
