General Mix Flashcards
Which occupancy group requires a rated fire wall between it and every other occupancy group?
Residential!
How would one calculate the minimum weight of the wall shown in the drawing? Code requirement that stabilizing moment is 1.5x the overturning moment
Correct. This is a three-part calculation. First, we must calculate the moment about point B. Then, we must calculate the weight of the wall needed to stabilize against this moment. Finally, we must apply the 1.5 factor of safety.
- Step 1: Calculate the moment about point B.*
- The overturning moment will equal the sum of moments produced by the lateral forces about point B. We calculate around point B because that is the point around which the structure would overturn, if forces acting from the left of the diagram were strong enough to overturn it.*
The force at the 2nd floor is 8 kips, and is 15’ away from point B along the Y-axis. The force at the 3rd floor is also 8 kips, and is 25’ away from point B along the Y-axis. The force at the 4th floor is 12 kips and is 45’ away from point B along the Y-axis. The equation is as follows:
- M ov(B) = 8 kips x 15ft + 8 kips x (15ft + 10ft) + 12 kips x (15ft + 10ft + 10ft)*
- M ov(B) = 8 x 15 + 8 x 25 + 12 x 35*
- M ov(B) = 740 kip-ft*
- Step 2: The stabilizing moment is given by the following equation, where ‘w’ is the weight of the wall needed to stabilize the structure. (We will use a capital ‘W’ in the next equation, which accounts for the factor of safety.)*
- Since the wall acts upon the centroidal axis of the structure (that is, it is in the middle of the building), we must find the distance along the X-axis from point B to the wall. Since the building is 30 feet wide, we divide 30 in half to arrive at the distance of the moment arm.*
- By definition, the stabilizing moment, M st(B), is equal to the overturning moment, M ov(B).*
- M st(B) = w (30 ft / 2)*
- 740 kip-ft = w (15 ft)*
- 740 kip-ft / 15 ft = w*
- 49.33 kips = w*
Step 3: Finally, we apply the 1.5 factor of safety. This is simply done by multiplying 1.5 times the stabilizing moment:
- W = factor of safety (w)*
- W = 1.5 (49.33 kips)*
- W = 74 kips*
Do vapor barriers prevent the movement of air?
No! Just moisture
What are the three different types of facing bricks?
FBS - Size & Color variation
FBA - Almost uniform, but vary in size, color, and texture
FBX - Extreme Mechanical perfection
When is a door a reverse swing?
When it swings towards you opening it.
What is a board foot?
Equal to a 12” x 12” x 1” piece of wood.
Which standards reflect the technical requirements for sprinkler systems?
National Fire Protection Agency (NFPA)
What are the four major causes of heat gain?
- Solar radiation through roof, walls and floors
- People
- Lighting
- Equipment
What are the two major sources of heat loss?
- Outside air infiltration
- Radiation through roofs, walls and floors
VAV HVAC
Variable Air Volume.
Just uses air.
Individual spaces control the amount of air
Can control humidity as well
Dual-Duct System
Separate ducts for heating and cooling
Uses air only
Reheat System
Uses only air.
May also filter and use outside air.
Like an in-wall unit, this system will condition air and put it back into a room.
Multizone HVAC System
Provides heating and cooling ducts to separate zones of a building.
Uses air only.
What are four types of air-only HVAC systems?
VAV
Dual Duct
Reheat
Multizone
How many BTUs is in a “Ton” of HVAC capacity?
12,000 BTU/hr is how much heat is required to turn a ton of ice into water in one day.
What is the difference between a register, grille, and diffuser?
A register has operable fins, a grille has a grate or wire weave, a diffuser is in the ceiling.
How many BTU/hr are in 1 Watt?
3.413 BTU/hr
How many Watts are in 1 Horsepower (HP)?
746 W = 1 HP
What are the typical electrical voltages supplied to a building?
Small & Residential - 120/240 volt single-phase 3-wire
Most commercial projects - 120/208 volt 3-phase 4-wire
Very-large-scale projects - 277/480 volt 3-phase 4-wire
What is Ohm’s Law?
The forumla to find resistance
Voltage = Amperage x Resistance
or V=IxR
How high should outlets be?
12”-18” AFF
Where are GFCI outlet protection required?
Bathrooms/Lavatories
Kitchens
Garages
How many feet of vertical water can 1 PSI of force lift?
2.3’ (or 2’-4”)
What type of pipes are most susceptible to water hammer?
Copper pipes!