Depth - Transportation Flashcards
how many different definitions are there for radius formula? and which ones?
2 different formulas. the chord and arc definition
In horizontal curve problems what is the definition of L and Lc?
L = length of the arc and Lc = length of the chord
what is the deflection angle?
an angle that is between the BC and any point along the curve. formula no longer in reference manual
how do you find the station of the PT in a horizontal curve?
find the station of PC and find the length of the arc then add them together
what is the difference between the long chord and a chord?
there is no difference it is the same value
what can be found dividing the inflection angle (delta or I) by 2?
deflection angle can be found
deflection angle formula is not given in reference manual
what is important to remember about the difference in the intersection angle and the degree of curvature?
the degree of curvature is a sliver of the intersection angle. the degree of curvature is also WITHIN the intersection angle hence why it is much smaller than delta angle.
what should i do for problems where i am given 2 bearings?
draw the tangents, find where they intersect, and then find the intersection/delta angle
how should i approach reverse curve problems?
whenever given a reverse curve problem always find the forward tangent, then find the length of curves for both of those curves
the tangent that is shared in a reverse curve is a combination of what?
the shared tangent is T1+T2 in the reverse curves
in vertical design, what is important to remember about the parabolic equation and the units?
when finding the elevation always have the units in STATIONS not feet
are vertical curves symmetrical?
yes
is the lowest point of a sag curve at the PVI?
false it is not in the middle of the curve
when reading the azimuth and bearings name the degrees for each quadrant
NE=0 degrees to 90 degrees
SE=91 degrees to 180 degrees
SW= 181 degrees to 270 degrees
NW=271 degrees to 360
what is headway?
the spacing between cars but in the units of time (sec/veh)
is there a formula in the reference manual that contains monthly or seasonal factors for ADT?
yes!!
what is the difference between time mean speed and space mean speed?
TMS = the mean of the speeds of the cars passing a specific point
SMS = mean of the speeds of vehicles passing through a stretch of the fwy
how do you find the elevation for BVC in vertical curve design? (formula)
Elevation PVI - g1(L/2)
what is a method of solving a compound curves problem?
to solve a compound curves problem create a triangle between the 2 curves and find the interior angles from the 2 bearings given
can PHF be greater than 1?
no PHF should not exceed 1
what happens to speed as it decreases?
density increases as speed decreases
what is the volume to capacity ratio?
the volume to capacity ratio is used to calculate the LOS
what is free flow speed?
the mean speed of cars during a low volume and low density
what is a clinker?
a shiny surface material that is rock which later gets turned into a powder and can be found in PCC
what happens to hydration when the cement has very fine sands in it?
it reduces the time cement needs to hydrate and it can reach its max strength faster
when using water for concrete design what should it be?
potable, clean, and water that does not contain any odors.
what is the Los Angeles abrasion test?
it is used to measure aggregates’ toughness and abrasion resistance. the aggregate is placed in a huge drum and is rolled and hit for 500 revolutions. afterwards it is sieved and the percentage passing the sieve corresponds to the abrasion of the aggregates
what is SSD?
saturated surface dry is the condition where aggregate doesn’t absorb any portion of the mixing water and does not add to the mixing water
can the strength of PCC exceed the aggregates strength?
no it cannot exceed the aggregates strength
what is a well graded aggregate?
it is an aggregate mix that is dense and has a variety of soils and sands
what do air entrainers do?
air entrainers produce tiny bubbles in the hardened concrete that provide extra space for expansion in water due to freezing
what is a water reducer?
they reduce the extra amount of water that is needed for the workability w/o having to add extra water but still increase the concrete’s workability
what does work ability do to the mix?
workability is increased, reduces slumps, workability is achieved at a lower W/C ratio so strength is increased, and less materials (water) then it is cost effective
what is a super plasticizer?
high range water reducers that greatly increase flowability of concrete and reduce the amount of water. also have been used to help sections with thin concrete
what is a retarder?
use whenever you cast in high temperature areas OR wherever placing in long members. it increases the time between mixing and finishing the concrete
what is a corrosive component of accelerators?
calcium chloride
what can fly ash do for concrete?
fly ash extends the hydration process, reduces water, reduces air content, increases the workability, and reduces the heat in hydration
what is a pozzolan?
it is a aluminous material which in itself has little or no cementitious properties but when added in water will react with calcium and process cementitious properties
how is workability measured?
workability is measured through slump. remember we did the slump test by creating a concrete mix and placing it in a cone and seeing how much it will shrink due to water ratio
in hardened concrete, what is obtained on the 28th day?
the compressive strength is obtained on day 28 or the peak of the curve
why do we pick the offset at 0.002 from the stress and strain concrete graph?
that is where the yield strength will be found
when tested, when is compressive strength is acceptable?
average of 3 tests are greater than or equal to fc and none of the test results are less than fc + 500 psi (if fc is <= 5000 psi)
what is another formula for the SSD using the middle ordinate and radius?
SSD = (R/28.65) * (cos -1*(1-M/R))
what is the formula for RMEV?
RMEV = no of accidents * 10^6 / (ADT * 365 days *number of years)
what design manual can i find information on ADA curb ramp and sidewalks on?
you can find it in the AASHTO greenbook
what is the average walking speed of a pedestrian?
3.5 ft/s
what is the superpave method?
the superpave method is a mix design that involves lab compaction and performance testing. the superpave number also depends on the temperature testing for a 7 day maximum design temp
what does an ahead tangent mean?
ahead tangent is the tangent corresponding to the back tangent
when solving a crest curve problem and asking for length of curve with questionable weather conditions, which table should you use?
use the decision sight table with “maneuver conditions”
what is the formula for the accident rate along a certain distance?
A = (# of accidents)*(10^8) / (ADT)(L)(365)(# of years)
when solving an accident rate problem, does property damage count?
no it doesnt. any other injury like personal or item fatal accident counts
what is the average haul distance?
A/Q
divide the area by the volume
