CTC-275 Construction Methods

Intro & Earthwork

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• Many different ways to build same building• How many ways can you build a ham and cheese

sandwich?• Types of ham, bread, cheese, toppings

• Construction methods change when– Materials change

• Why thatch roofs?• Why teepees and long houses?• How important where nails to building

– Equipment changes• Horses to steam engines to today• Erie Canal was dug with shovels and rock sleds• Steam engines were stationary with belts going

from pulleys to the engine

House Construction

• What materials can be used to build a house and what equipment is required– Wood – hammers, saws, drills, squares

• Can also use engineered wood • What has happened to lumber in last 100 years?

– Concrete – either cast in place, precast, or shotcrete• Can be above ground or below

– Steel– Stone– Brick– Adobe – only need forms– Haybales

House Construction

• Wooden houses can be constructed using three methods– 1. Balloon Framing– 2. Platform Frame– 3. Modular – assembly line

Questions

• What made skyscrapers possible?

• How old is concrete and who first used it

• How old are nails?

Construction Order

• There is an order to all projects– What activities get done first– What activities need to be done in a specific

order– What activities can be done at any point in

time

Construction Order

– Above ground Swimming pools• Remove topsoil & level area 3’ larger that pool

diameter• Rake soil to remove rocks and roots• Layout bottom track• Dump sand inside pool area• Level track• Layout wall parts• Roll wall and put on J channel and top rail• Bolt wall, attach skimmer

Construction Order

– Swimming pools• Spread sand inside pool wall – rake & tamp• Attach wall uprights• Attach liner to J channel• Use vacuum to suck liner to wall• Plumb sand filter & pump together w/ skimmer &

return line• Attach top coping• Add water• Cut out skimmer and return

Construction Order• Buildings:

• Clear site• Foundation work• Framing & Siding• Roofing• Windows and Doors• Siding• Electrical - rough• Plumbing - rough• Insulation• Wall finishes

Construction Order

• Buildings:• Foundation slab• HVAC• Ceilings• Electrical – finish• Plumbing – finish• Paint/wall coverings• Flooring• Landscaping• Pavement

Construction Order

• How far along do you need to be before starting next activity?

• On a house – probably one at a time

• On a 1 floor bldg – probably 1 activity at a time but depends on size

• Skyscraper – 1 activity per floor

Construction Order

• Highways• Centerline survey• Clearing• Bridge work• Centerline survey• Earthwork to get to bottom of subbase elevation• Centerline survey• Subbase placement• Centerline survey• Base placement

Construction Order

• Highways• Centerline survey• Drainage• Utilities (lights etc)• Pavement base course• Pavement wearing course• Side slope grading• Guard rail• Lights and signs• Pavement Markings

Construction Order

• Move from one end of project to the other with each activity

• Have multiple activities happening at any time

• Surveying is a full time activity

Start at beginning

• Earthwork– Moving rock or soil from one location to

another– Processing it to meet location, elevation,

density moisture content, etc– Efficient earthwork requires: accurate

estimating of work quantities and conditions, proper equipment, competent job mangement

Equip Selection

• Proper equipment has major impact on efficiency and profitablility

• Can equipment perform required work

• Also look at profitablility, other uses for equipment, return on investment, availability of parts and services, effect of downtime on other construction equip

Equipment planning

• Need to plan to effectively use equipment

• Production of equipment– Production = Volume per cycle/cycles per

hour– Cycles per hour is based on efficiency of

equip• Swing angle and elevation to truck bed• Soil hardness and Soil type• Room to manuever

Equipment planning

• Cost per production unit = equip cost per working hour/equip production per hour

• Table 2-1 show efficiencies

Soil And Rock

• General Soil Characteristics• Trafficability – ability of soil to support weight of

vehicles under repeated traffic– Controls traffic on unimproved access roads– Also gives measure of how earthmoving equip will

operate– Primarily function of moisture conditions and soil type

• Loadability – how difficult to excavate and haul a soil

– Granular – high – Compact cohesive - low

Soil And Rock

• Unit Soil Weight– Pounds /cy– Depends on soil type, moisture content,

degree of compaction– Relation between soil weight and bearing

capacity• So soil weight is used as a measure of compaction• Soil weight is also a factor in hauling

Soil And Rock

• Moisture Content(%) = (moist wt – dry wt)/dry wt X 100

• Soil sample 120#

• Dry weight 100#

• MC = (120-100)/100X100 = 20%

Soil ID

• Boulders• Cobbles – over 3” diameter• Gravel 1/4” – 3” diameter• Sand 0.7mm (200 sieve) – ¼” diameter• Silt 0.002 – 0.7 mm• Clay less than 0.002mm• Organic Matter decaying organic matter• Soils classified using these types

Soil Classification Systems

• Unified System– All material 3’’+ removed– Separates soils into two main groups- Fine grained

and coarse grained– Table 2-2, Figure 2-1

• AASHTO System– 7 classes of soil– Based on suitability of soil for subgrade– Table 2-3– Table 2-4

Soil Volume Change Characteristics

• Soil Conditions– Bank – material in natural state before

disturbance – Bank cubic yard– Loose – material that has been excavated or

loaded loose cubic yard– Compacted – material after compaction

compacted cubic yard

Soil Volume Change Characteristics

• Swell– Soil increases in volume when it is excavated

• Soil grains are loosened and air fills voids• So 1 unit of soil in bank is smaller than the soil

once it is excavated• Swell(%) = ((weight/bank vol)/(weight/loose vol)-

1)X100• Soil wt = 2800#/cy in bank• Soil wt = 2000#/cy loose• Swell = ((2800/2000)-1)X100 = 40%

Soil Volume Change Characteristics

• Shrinkage– Soil decreases in volume when it is

compacted• Air is forced out of soil• So 1 unit of soil compacted is smaller than the soil

in the bank or once it is excavated• Shrinkage(%) = (1-(weight/bank

vol)/(weight/compacted vol))X100• Soil wt = 2800#/cy in bank• Soil wt = 3500#/cy compacted• Shrinkage = (1-(2800/3500))X100 = 20%

Soil Volume Change Characteristics

• Load and Shrinkage Factors– Need a common unit of measure for earthwork (get

rid of calculations )– Can use any of the three measures

• Called pay measure in contract• Load factor = 1/(1+swell)

– How many BCY can fit on a truck

– LCY *Load Factor = BCY

• Shrinkage factor = 1- shrinkage• How many BCY needed for CCY• BCY * Shrinkage factor = CCY

Soil Volume Change Characteristics

• How many 10cy truck loads of soil = 1000CCY ?• Swell = 30%• Shrinkage = 25%• BCY = CCY/(1-shrinkage)• LCY = BCY*(1+Swell)• LCY = CCY/(1-shrinkage)*(1+swell)• LCY = 1000/(0.75)*1.30 = 1735 LCY• Truck loads = LCY/10 = 174 truck loads

Spoil Banks

• Material removed from excavation– Longer than wide – spoil bank – triangular x

section– Conical – spoil pile– To determine the size of the bank or pile need

swell and angle of repose for soil– Angle of repose = angle that soil on side of

bank naturally form• Varies with moisture content and type• Table 2-6

Spoil Banks

• Spoil bank– Vol = X sect area x length– B = (4V/(lx tan R))^1.2– H = (B x tan R)/2– B – base width– H height– L length– R angle of repose– V volume

Spoil Banks

• Spoil pile– Vol = 1/3 D/2)^2 X H– D = (7.64V/tan R)^1/3– H = D/2 x tan R– D – diameter of base– H height– R angle of repose– V volume

– How long would a spoil bank for 40000 cy be if it was 100’ wide? Angle of repose = 30 deg

– How high can a spoil pile 50’ in diameter be if the angle of repose = 35 deg?

• How many cy can it hold?

Estimating earthwork

• 3 types of excavations– Small pit– Trench– Large areas

• Roadways – Find cut and fill using cross sections– Mass diagram

Roadways

Estimating earthwork

• Pit Excavations– Area X average depth– Depending on size and ground may break into

several geometric shapes to get volume– Give bank volume

Estimating earthwork

• Trench Excavations– V = x sectional area X length– Take x sections every 50 feet and compute

volumes between x sections

• When estimating don’t forget the angle of repose and OSHA

Estimating earthwork

• Large Areas– Use a grid to find volume– V = A*(average depth)– For a rectangle– V = (LxW)(h1+h2+h3+h4)/4(1/27) cy

Estimating earthwork