PPD Flashcards
What are the large outdoor equipment pieces you need on a large building site?
Dumpster - out of view, provides smell and loud noises
Transformer - translates from municipal service (poles or underground wires ) to in-building switch gear could be on pole, on ground outside (4’ from road ), underground outside building or inside building. Ugly and sometimes loud-put out of view. If inside- often non-flammable coolant is needed
Cooling Tower - large -out of view and they need access to the air so they can’t be indoors. They are often near the chillers they serve, but can be remote
Generator - loud, but IF it is a backup generator, it will be rarely used and the noise will not be a problem. Must exhaust outside, so typically sits outside the building. If it is an indoor generator, it must exhaust to the outside
How do you decide what is the least expensive construction technique?
What you see on sites is usually the least expensive option-
OsB sheathing is more common and less expensive than plywood sheathing
Plywood is more common as formwork, and less
Expensive, than insulated concrete forms (ICFs)
Vinyl siding is more common, and less expensive, than wood siding
Asphalt roadway is more common, and less expensive, than concrete as pavement.
Etc….
What is a right-hand reverse - bevel door?
Rh- right hand push
LH - left hand push
RHR - right hand reverse right hand pull
LHR - left hand reverse left hand pull
How can we shade windows in the northern hemisphere?
South facing - deciduous trees, horizontal lovers, light shelves, shade with other adjacent building masses
Requires longer horizontal overhang for lower southern sun
Shading high southern sun requires shorter horizontal overhangs
East- and west-facing: deciduous trees, vertical louvers, light shelves, shade with other adjacent building masses
North-facing-shading not required
Vertical Louvers on east/west faces
The geometry of the fins can vary relative to the position of the sun - position the vertical louvers on the east or west face so that the “cut- off” angle of each fin shades direct sun. The geometry will vary based on the specific location of the sun
Light shelf
A) Height of light shelf should be such that it shades room occupants from sky view
B) Height of top light should be as high as possible (with A note in mind)
C ) Extension of light shelf should be 1.4 times B IF light shelf faces due south ( 1.7 times flight shelf faces more than 20 degrees east or west of south) in hot climates the extension of the light shelf can be louvers to all an bult-up heat to escape upward
X) to get light deep into the room ( and to mitigate glare) sunlight should reflect Off top of light shelf and then off light-colored ceilings
R) because view to sky is shaded, areas close to the window have less glare
Z) top of light shelf should be painted white.in cold climates, the top surface can be mirrored. Bottom of light shelf should also be light colored so that it doesn’t contrast too heavily with the bright outdoors when viewed from within,
Why does climate matter?
1 - The sun is lower in the east and west than in the south, especially near sunrise and sunset. To shade from the sun, we need to extend the light shelf outward farther.
2- in a hot or mixed climate, a mirrored, top surface would reflect unwanted heat into the occupied space
What is the difference between active and passive radon mitigation?
Passive - caulk / sealant in foundation cracks and where the slab meets the foundation wall, and plastic sheet below the slab seals the building from the radon in the ground. Continuous, airtight plastic pipe extends from the sub-stab gravel straight up through the roof to allow an easy path for underground radon to escape without entering the house. No fan needed.
Active- fan pulls air through continuous plastic pipe from below stab or crawlspace to the atmosphere bypassing the building - we don’t want the radon that is pulled out of the foundation to leak back into the building, so we seal the slabs. We put the fan in the attic or anywhere else outside the enclosures; and we discharge the radon from the pipe at least 10 feet from a window, door or - other opening) at least 10 feet off the ground, and above the roofline, as close to the ridge as possible. Angle the pipe discharge away from the building surface to avoid moisture discharge or mildew build up on the building wall or roof.
For new homes, passive should be installed ( -its cheap and can be converted to active if needed)In areas where there are high radon levels, start with an active system
What is the “soft story” problem?
Discontinuity, indirect load path - not a continuous shear wall
Causes over stress on low level columns that cause collapse
Solution _ high first story with slender columns doesn’t have to cause soft story problems - the problem happens when the columns are the primary resisters of lateral force - add additional columns, add bracing, add external buttresses
Stair width-code
Calculate for the whole stair system based on the Floor with the highest occupant load (do not have to and cumulatively)
Min width 36” for less than 50 occ.
Min width over 49 occ. Is 44”
Handrails must not protrude more than 4,5” on each side
Multiply occ. X 0.2 IF sprintlered, X 0,3 if not, gives minimum total width ( all stairs combined)
Stairs must be within 30” of a railing to “count” as egress -so over 60” wide needs center rail or to be separated IF you need it for code)
Shear (pin) vs moment connection
Shear - with steel, the beam web is bolted or welded to the column, but flanges event. They resist gravity but don’t do well with lateral or seismic. (Need lateral cross bracing or a shear wall ) - most connections - it tone side disconnected it would swing down
Moment - generally bolt/weld both flanges and web to column and resist both vertical gravity and lateral wind/seismic - can handle the hurricane without additional shear wall or cross bracing - cost of moment connections is significant
Convective loop in a wall cavity
In wall cavities of greater than 4 inches - a convective loop forms as air naturally rises up the warm side of the cavity and falls along the cold side. This acts as a short circuit of the thermal barrier, accelerates the transfer of heat from inside to outside and cancels or reverses the thermal benefit of the cavity (especially in tall cavities in cold climates)
Radiant heat exchange across the cavity as the warm side “sees” the cold side and transfers its heat by electromagnetic energy.
Measure heat transfer through conduction (r-value)
Conduction, convection, and radiation across a wall assembly
Conduction - thermal bridge-heat exchange through sold continuous material
Convection - air cavity , heat rises on warm side, falls on cold side (loops) -r-value
Radiation - heat radiates from inside out
Are wind loads higher at the top of tall building?
Yes - wind speeds increase with height above ground - hard to account for in tall buildings
High pressure (windward ) side takes a “pushing” lateral load while low-pressure (leeward ) side takes a suction pulling load in same direction
Vortex shedding - the downward pattern formed by the building’s disruption of wind flow, can create a for ce perpendicular to the wind direction and dislodge a window
Softening corners of towers, taper or set back building plan as it rises, twist as it rises, provide large apertures in the windward face that allow wind to pass through at some floors, or position a heavy damper in a top floor to counteract the natural vibration of the building - these all help r reduce canyon effect on city below too
In which condition does an exit (stair) need to be pressurized to keep smoke out?
Pressurized stairs have a fan connected to the shaft activated by smoke detector - required in these types of buildings-
1 - tall buildings (takes a longtime to get down and out)
2- in underground buildings (you have to more up toward the smoke)
Underground’ buildings have stairs that must be pressurized
The egress path (the path for getting out in an emergency ) has 3 parts
1 - exit access (corridor from room to stars)
2-exit (the stairs)
3-exit discharge (door from the stairs to outside)
How do we best reduce the build-up of low-frequency sound in a room ( rumble from mechanical equipment)?
Position sound-absorbing materials near the corners and edges of walls - called a bass-trap
Low frequency sounds naturally build up around perimeter and in corners
Clay vs sand
Clay behaves unpredictably when it gets wet- it swells
Sand is more stable to build on
Proportion of clay in soils test will determine stability ( soils are mixed)
A good barrier for preventing sound from transmitting from one room to the other is ~
Airtight - assembles that are massive, airtight, and structurally discontinuous do the best job keeping out unwanted sound - sound absorption is used to reduce buildup in the same room as the sound
A larger room has a _ reverberation time than a smaller room.
Longer _ large rooms, rooms with fewer surfaces, and rooms with harder, smoother, less-fuzzy surfaces are more reverberant ( sound lingers longer after it is suddenly stopped ) The more reverberant the room, the longer the reverb time, measured in seconds. Rooms with unamplified speech, amplified speech, and amplified music generally want to be smaller with fuzzier surfaces - In contrast, rooms for unamplified music, like concert halls, generally want to be more reverberant-larger with harder and smoother surfaces
