Chapter 6 Flashcards
General aim of using mechanical plants
- Produce a structure of reasonable cost
- Ensure sound workmanship
- Overcome shortage of manpower
Plants are classified into 4 categories
- Small powered plants
- Excavation and earth moving plants
- Transporting plants
- Concrete mixer plants and pumps
Small powered plants are divided into two classes
- Hand held tools
- Power tools (E.g. Electric drill, cartridge hammer, vibrators)
Types of fixed position excavating plants
- Face shovel
- Backactor
- Grab
Types of moving excavating plants
- Dredger
- Scraper
- Grader
Factors that affect the choice of Earth moving plants
- Location of site
- Ground condition of site
- Time allowed to complete the work
Types of transporting plants
- Lorries/trucks
- Hoist
- Crane
Factors that affect the choice of transporting plants
- Site condition
- Time available
- Type of material to be removed
Types of contracts
- Fixed-price contract (Measured contract, Lump-sum contract)
- Cost reimbursement contract (Cost-plus contract, All-in contract)
Common terms of contract documents
- Defect Liability Period
- Retention Fund
- Progression Payment
- Liquidated Damages for Delay
- Provisional Sum
- Certificate of Completion
Contract can select a contractor by three means
- Open tendering
- Invited tendering
- Negotiation of a contract with a selected contractor
Documents required to form a contract
- Conditions of contract
- Drawings
- Specifications
- Schedule of Rates
Measured contract
Most common form of contract, includes BQ
Lump-sum contract
Used for small projects such as addition and alteration work, does not include BQ
Cost-plus contract
Used for exploratory or urgent work whereby no detailed design, BQ or specification is unavailable
All-in contract
Covers both the design and construction works
Types of cranes
- Movable cranes
- Static cranes
- Tower cranes
Movable cranes
Able to move from one position to another position
Static cranes
Fixed, used primarily for lifting heavy loads such as steel work
Tower cranes
- Used for construction of high-rise building
- Comes with horizontal jib and a lifting hook
Hoist
- Static
- Mobile
Concrete pumps
Used as a transporting plant for wet concrete
Advantages of concrete pumps
- Site plant and space are reduced
- No shock landing on formwork
- Faster pour can be achieved with less labour
Types of concrete mixer plants
- Concrete drum mixer
- Central mixing and batching plant
Types of concrete drum mixer
- Tilting drum (used only for small batches)
- Reversible drum
Types of concrete plants
- Ready mix plant
- Central mixing plant
Ready mix plant and central mixing plant difference
Ready mix plant combines all ingredients except water at the concrete plant, central mixing plant combines some or all ingredients including water at a central location
Conveyors
- Used mainly for transporting aggregates and cement
- Transports materials up to 0.7m
Main parts of bulldozer
- Tractor
- Engine
- Tracks
- Blade
- Ripper
Function of bulldozer
Used for stripping and excavating up to a depth of 400mm below the level of the machine
Function of load shovel
Used for scooping loose material in the bucket
Function of face shovel
Used for excavating into the face of an embankment
Function of backactor
Used for excavating trench, basement and pit
Function of grab
Used to excavate loose soil
Function of dredger
Used for deepening rivers and estuaries
Function of scraper
Used to excavate and transport soil
Function of grader
Used for finishing to fine limits in large area of ground
