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Posted on Sep 14, 2022 in Social sciences

Airport Planning/Design

ATC, Airside facility design, capacity, length requirements, environmental effects

In Canada airports were recently privatized in 1994 with the National Airport Policy (NAP) in an effort to make airports more self-sufficient as air travel demand increases

Airports classified into 5 types, National (>200k passengers/yr), Regional/Local (<200k passengers/yr), Small (Recreational), Arctic, and Remote

To design airside facilities, consider:

Future travel demand (Usually designed to handle 90% of average annual hourly volumes)

Route structure (hub+spoke vs transit)

Aircraft types

Transfer frequency

Visual Flight Rules (VFR) for small planes in good visibility conditions, only in less travelled air corridors

Instrument Flight Rules (IFR) needs more pilot training and is for heavily travelled corridors and safe separation is maintained by ATC

Airspace in Canada has low and high level airways connecting airports

Airspace 5000ft-25000ft around airports are controlled (needs ATC clearance)

Objective of ATC is safety + efficiency of aircraft movement

En-route airways between airports

Low level airways from 2200ft AGL to 17999ft ASL

High level airways from 18000ft to 45000ft ASL separated by 1000ft vertically, West (180°-359°) at even alt, East (000°-179°) at odd alt

Runway labelling

Runways labelled using bearings, ex: runway from east to west is running from 90° to 270°

The direction heading towards east (90°) would be labelled 09 and the direction heading towards west (270°) would be labelled 27 (runway # = heading/10 round to whole #)

If multiple runways exist, they are labelled with L, C, and R respectively

Wind rose diagram

The diagram is circle divided into sections based on direction and windspeed (units kn)

A percentage written into each section representing percentage of time in a year a wind vector whose tail is in that section and head at the center occurs

Using this diagram draw outline of runway 15kns wide and add sections and parts of sections inside outline to find % of time runway is usable (estimate each section as 0%, 50%, or 100% covered)

If want to figure out if runway is usable with certain wind vector need to calculate component of wind vector perp and parallel to runway (perp=crosswind<15kn and parallel=tail/head wind<5kn for tail but doesn’t matter if head)

Runway Capacity

Queue time is the difference between arrivals and service rate vertically

Ex: From graph queue lasts from hour 2.3 to hour 5 and max queue length is around 8 people

Poisson distribution

Where  is probability of n arrivals in t time,  is mean arrival rate,  is # of arrivals/hour, and t is time in hours

With a First in First out (first come first serve basically) system and a poisson arrival distribution, many conditions can be specified based on  (arrival rate/hour) and  (service rate/hour)

 (probability of having n aircraft in system)

 (average # of vehicles in system)

 (average length of queue in # of aircraft)                            Where:

 (average time spend in system in hours)

 (waiting time in queue in hours)

Runway Capacity

Using space time diagrams: Arrival separation, aircraft speed, and runway occupancy times will be given in Table 2.4 and 2.5 on page 2-23

Need to remember: Take off separation of 3nm and insertion (arrival after departure) separation of 2nm

Given sequence of aircraft, draw space-time diagram, estimate interval time, find ops/hour (service rate/hour)

Mixed Index = %Class C+3*%Class D, used to estimate ops/h

Runway Lengths

Many diff landing gear configurations and tail heights

Runway length depends on wing loading, wing area, lift coefficient, and air density (Take off occurs when lift>wing loading)

, where p is air density, V is airspeed over wing, S is wing area, and C_L is coefficient of lift

FAR take off length req usually 115% of demonstrated takeoff dist and 167% of demonstrated landing dist; Factors: air density (temp/elev), speed (runway gradient), coeff of lift (flaps), lift (mass of aircraft)

Taxiways

Configuration decides what operations runway can support (land/takeoff)

Taxiways designated by alpha/numeric identifier ex A1 (alpha 1)

Easterly taxiways are odd and westerly are evenly numbered

Due to large wheel spans some taxi ways need to be redesigned by:

Increase radius of inner curve

Using compound curve on outside

Restrict use of small curves for large aircraft

Noise impact of airports

, where P is rms of sound pressure (N/m²), Po is weakest audible sound (20µN/m²), and L_p is sound pressure level in dB

, where dBx is summation of sound pressure levels (dB) and s_i is a source of sound in dB

, SEL = sound exposure level of one aircraft and T_i is the time associated with sound s_i

SEL equivalent in 1 hour is the summation of the SEL of one aircraft * #ops, a 10dB penalty is given to night operations

, where L_dn is day night equivalent sound level, must be<65dB for residential areas

Noise exposure forecast (NEF)

Limited by transport Canada and thus design of planes started to take into account noise levels and planes got quieter

Highway planning and design

Highway has two primary functions, vehicle movement between points and access to land, in conflict as access disrupts traffic flow

Five types of roads:

Freeways (Controlled access highways, ramps, no stop light, think 401 Collector)

Expressways (Similar to freeway, less access from local roads, think 401 Express)

Arterial (Major local roads, think Yonge street)

Collector (Carry traffic from local to arterial)

Local (Driveway/parking lot to collector)

Further classified into Urban vs Rural and Divided vs Undivided and design speeds

Example road classification: RLU40 (Rural Local Undivided 40km/h design speed)

Second example: UED100 (Urban Expressway Divided 100km/h design speed)

AADT: Average Annual Daily Traffic, the design hourly volume (DHV) typically uses 30^th highest hour volumes -> usually around 10% AADT

Also need to consider directional split (usually 50/50) and composition of traffic

Typically the posted speed is 20km lower than design speed

Design speed is safe for favourable conditions, but not for extreme conditions such as ice or high traffic volumes

Typically consider wet pavement conditions (coeff of friction  0.3) for design to account for somewhat unfavorable conditions, don’t design for worst case conditions as its too costly

Design speed determines geometric requirements (SSSD, horizontal/vertical alignments, super elevation, etc)

When designers restricted, good practice to warn drivers with signs

Grade, Air, Rolling, Curve resistances and sometimes weight of vehicle act against vehicle in motion

Typical driver reaction times is assumed to be 2.5s (Very slow)

To calculate SSSD:

t_pr = 2.5s, v = speed (m/s), g = 9.8m/s², f = coeff of friction, G = average grade

Vertical Alignment

Profile of road along centerline, usually series of crest and sag curves defined by K-values, larger K-value = gentler curve

, L = horizontal length of curve, A = algebraic difference in grade (%)

Considerations include driver vision, forces on vehicle, acceleration/deceleration on grades, cost (earthworks)

Grade of road affect safety as trucks may have trouble navigating steep grades in icy conditions and increased fuel consumption uphill

Grades restricted by design speed, highway classification, traffic volume, terrain/property, and the environment (<3% grades okay, >5% grades difficult for trucks)

Crest (dictated by driver SSSD over curve) and sag curves (dictated by headlight visibility) used to transition between grades

, H = drivers eye height (1.05m), h₁ = object height (0.38m)

, H = headlight height (0.5m),  = light beam angle (1º)

Horizontal Alignment

Roadway in plan view, change direction of travel from tangent sections to circular curves using transition/spiral curves

Minimum horizontal curve restricted by design speed, pavement friction, super elevation

Super elevation is banking of curve, usually <6% up to 8% sometimes

, v = m/s, V = km/h, e = super elevation,  = side friction

Transition/spiral curve used to transition between tangent section and circular curves

Develop super elevation and allow driver to turn gradually

, A = spiral parameter (m), R = radius of circular curve (m), L_s = length of transition curve (m)

Length restricted by:

aesthetics (short spiral not visually appealing)

, V = design speed in km/h

super elevation (min length to develop super elevation)

, w = pavement width, e = super elevation,

s = relative slope

comfort (centripetal acceleration )

, v = m/s, V = km/h

Clear Zones

Clear zone provides area for vehicles to recover if they leave roadway, defined as distance from edge of roadway to hazard

Minimum clear zone influenced by design speed, traffic volume, cut/fill slopes, steepness of slopes, horizontal curves, and should protect ~80% of errant vehicles

Clear zone also considered inside curves, due to visibility requirements

Use SSSD and geometry to determine clear zone needed to see hazard in time

Consider lane width (driver on middle of inside lane) and radius of the curve

Radius given is to middle of road, subtract ½ or 1,5 lane width for 2 or 4 lane respectively for inner radius

, ,

Rural Highway Capacity

Capacity of max num of vehicles expected on a given road under prevailing conditions

Physical features of road & traffic conditions

Level of service defines quality of traffic flow in terms of V/C

Steps for design in general: Determine design value, determine adjustment factors, assume # of lanes, calculate service volume and compare to design value

For multi lane rural hwy in 1 direction:

SV is service volume in ONE direction, N is #lanes in one dir, V/C is volume to capacity ratio specified by LOS, T is truck adjustment factor, W is lateral clearance factor

 to find truck factor where E_T is car equivl, and P_T is %trucks

SV in units of veh/hr, design for 30^th highest hourly volume as % of AADT

Can find all values using Tables 3.9 to 3.12 and Figure 3.19

For two lane rural hwy in both directions:

SV is service volume in BOTH directions, V/C is volume to capacity ratio specified by LOS, T is truck adjustment factor, W is lateral clearance factor

Long sight distance (450m+) provides passing opportunity (PO%)

Truck factor different for climbing lane sections, use half % trucks for T, for downhill 2 cars = 1 truck

Uses different set of Tables 3.13 to 3.17

Intersections

Joins 2+ directions, complicated for drivers, goal is to provide change of direction while minimizing conflicts

Must consider off-tracking of back wheels of trailers

Roundabouts benefits:

Lower speed

Short pedestrian crossing

Only right turns

Fewer stops/delays (less emissions)

For design of roundabouts for a WB-20 vehicle f and g are related by provided table

f is total width of roadway portion of roundabout or inscribed circle diameter

g is width of roundabout between curbs

Pavement Design

Pavement refers to subbase, base, and asphalt/concrete layers but doesn’t include subgrade or native soils, the four main functions are:

Provide water proofing

Spread traffic loading to reduce stress transferred to subgrade

Provide surface which provides adequate friction

Provide smooth/comfortable surface for vehicles

Three types include rigid (Portland cement), flexible (asphalt), composite (both)

Pavement design is process of selecting pavement types/thicknesses to support given traffic and climate loads for specified life cycle while being as cost effective as possible

Subgrade is foundation of roadway, usually made from native fill (sometimes with imported)

Soil investigation conducted to determine existing soil engineering properties:

Thickness of top/organic soil (note that organic soils have extremely variable properties and are hard to design for, and therefore should be removed when possible)

Identify soil types and corresponding engineering properties

Depth of bedrock

Groundwater conditions

Existing pavement structure layer thickness & properties

Unified Soil Classification System (USCS) classifies soils based on particle size distribution and plasticity, soils given name & symbol

Note that D₆₀, D₃₀,and D₁₀ refers to 60%, 30%, and 10% passing diameter respectively

Frost Susceptible Soils

Certain types of subgrade soils susceptible to developing ice lenses, can be mitigated by:

Removing water close to subgrade (effective drainage)

Removing the frost susceptible soil

Insulating the subgrade

Chamberlain method, analyze soils <2mm in diameter,

certain proportions are frost susceptible

Frost penetration can be estimated with:

, where P is frost penetration,

and F is freezing index

Aggregates make up 95% of pavement structure

Mined from quarries, naturally occurring, recycled,

or artificial

Layers of pavement structure from bottom to top include:

Subbase first layer of aggregate (larger grain sizes),

transfers traffic loads to subgrade, transmit moisture and provide insulation to subgrade

Base layer above subbase, transfers loads and moisture, also provides insulation, aggregate used usually <19mm dia and of higher quality vs subbase

Pavement surface layers has two types (both impermeable to water until cracking):

Asphalt which uses high quality aggregate mixed with bitumen

Portland Cement which uses quality aggregate mixed with water and cement

Aggregate gradation has specified ranges for %passing at different grain diameters for different mixtures, find if mixture is within the specified ranges by plotting or comparison on paper

Asphalt cement is waste product from refining crude oil, used as a binder in asphalt concrete

Classified using penetration test, higher penetration number = softer asphalt cement

Also temperature range, i.e PG 64 – 22 means asphalt meets performance criteria if 7 day max pavement temp below 64°C (20mm below surface) and min temp is -22°C at surface

Portland cement is mixture of fine and coarse aggregates bonded together by cement paste

Most common type is general use, with other types such as high sulfate resistance (HS)

Important function of pavement is to distribute load into

subgrade (relatively weak)

This depends on stiffness (angle of distribution)

Also depends on thickness of layer

Pavement deteriorates over time, and quality is assessed by:

Serviceability, or ability to serve high speed, high

volume, car & truck traffic

Performance, or serviceability over time

Measured in Canada with

RCI, ranges from 8-9 for new

Pavement, resurfaced at 4.5

Usually cheaper to maintain

assets than rehabilitating

Structural design can be simplified

to two main steps, selecting

materials and thickness of those

material layers (Factors: traffic loading, environmental conditions, subgrade, available materials, quality of construction, funding, service life and ride quality requirements, etc.)

Traffic loading predicted based on past traffic and theoretical projections

The unit of ESAL is the load on the road by an 80kN load on a single axle with dual tires

Estimate using fourth power approx:

Better estimate using exponential curves in Figure 4.14 on page 4-30

Small vehicles often has negligible impact and are ignored

Then measure ESAL of the most loaded lane over a year using:

AADT is average annual daily traffic (all lanes, both direction)

HVP is heavy vehicle %

HVDP is % of heavy vehicles in design lane (note 50/50 directional split)

TF is equivalent ESAL caused per truck AKA LEF (usually given)

TDY is days load is imparted per year, use 365 unless specified

Cumulative ESAL over design life calculated using exponential growth formula:

g is projected annual growth rate and t is time in years

Design methods for conventional pavements

Empirical with field observations and theoretical with calculated strain, stress, etc.

Also experience based design such as standard sections in Table 4.7-4.9

Round up ESAL calculated to use the next highest table

Standard designs can be modified with granular base equivalents (GBE)

AASHTO 93 Flexible Pavement Design

Results in a Structural Number (SN), which provides minimum level of capacity

a is the structural layer coeff of that layer

D is thickness of the layer

m is drainage coeff of that layer

Relative damage: , where  is the relative damage and  is the resilient modulus for a given time period

To calculate the  over a year, convert the  of each month to , sum the  and then convert back into

 is usually measured but can be estimated with

Reliability usually assumed as 95% and standard deviation assumed to be 0.4

With given information, use Figures 4.16-4.18 to find structural coefficient and resilient modulus of each layer

Using resilient modulus of the layer below, determine structural number with % Reliability, standard deviation, cumulative ESAL, and  (serviceability loss)

Using structural number, calculate thickness of layer required (subtract SN of layers on top if there are any), check with minimum thickness, if below minimum, use minimum

Repeat for all layers to find the thickness of each layer required