Heavy Reinforced Concrete & Steel Construction

Heavy Reinforced Concrete, Pre-Stressed Concrete & Steel Construction

• This material includes the compilation of information from journals, books, magazines, internet, review centers and other publications for architecture students

Heavy Reinforced Concrete, Pre-Stressed Concrete, and Steel Construction

• Foundation systems transfer lateral loads from the superstructure to the ground
• Lateral forces are transferred through soil friction and soil pressure
• Foundation systems are classified into shallow and deep foundations

Shallow Foundations

• Shallow or spread foundations are utilized when stable soil with adequate bearing capacity occurs near the ground surface
• The foundations transfer building loads directly to the supporting soil through vertical pressure

Individual or Isolated Footings

• These are spread footings that support free-standing columns and piers
  • Block or square footings
  • Stepped footings
  • Slope or pyramidal footings

Strip Footings

• Continuous spread footings of foundation walls
• Include stepped footings that accommodate changes in levels to maintain depth around a building

Combined Footings

• Support two or more columns
• Used when centering a footing is not possible, such as near property lines
• Footings are typically rectangular or trapezoidal

Cantilevered Footings

• Used instead of combined footings
• Footings of exterior and interior columns are connected by a tie-beam or strap

Continuous Footings

• Support a line of columns or all columns with strips at right angles

Mat or Raft Foundations

• Used on soil with low bearing power where unequal settlement is likely
• All foundation parts are tied together to act as one, assisting each other in maintaining level and plumb

Types of Mat foundations

• Flat slabs of plain or reinforced concrete
• Beams or girders with a slab underneath
• Beams or girders with a slab on top

Steel Grillage Foundation

• Used to avoid deep excavation and distribute load over a wide area
• Steel rails or beams provide resistance with minimal depth

Setting up a steel-grillage foundation

• The foundation bed is covered with at least 6 inches of concrete
• The beams are placed on this layer and grouted to secure them
• Concrete is placed between and around the beams to protect them
• The clear space between the top layer's flanges should be at least 2 inches

Deep Foundations

• Used when soil near the surface is unstable or lacks adequate bearing capacity
• Extend through unsuitable soil to transfer building loads to a better bearing stratum like rock or dense sand/gravel

Pile Foundations

• Pile foundations consist of end-bearing or friction piles as well as pile caps and tie beams
• Pile foundations transfer building loads to a suitable bearing stratum

End Bearing Piles

• Depend on soil or rock resistance beneath their feet for support

Friction Piles

• Depend on frictional resistance from surrounding earth mass
• Skin friction is limited by soil adhesion and shear strength

Wood Pile Foundations

• Use wooden piles made from tree trunks
• Piles should be straight with a small end diameter of at least 5 inches for light buildings, or 8 inches for heavy buildings
• The piles are driven with a drop hammer or steam hammer

Hammer Details

• Drop-hammers raise the hammer and drop it automatically or by hand, steam raises hammers. Hammer is generally raised by steam.
• Pile-driving hammers for building foundations typically weigh 1,500 to 2,500 lb. and fall from 5 to 20 ft.
• Steam-hammers deliver 60-70 quick, short blows per minute, giving the soil less time to settle around the piles

Pile Driving Considerations

• During pile driving, care must be taken to keep the piles plumb
• When penetration becomes small, reduce the fall to about 5 ft., giving rapid, successions of blows
• Piles that refuse to sink should be cut off and another driven beside it
• Further attempts are useless when piles sink less than 1/2 inch under 5 blows from a 1200 lb. hammer falling 15 ft.
• Protect the top of the pile by using a pile ring when the penetration is less than 6 inches at each blow

Soils and Point Types

• In soft/silty soils, piles drive better with a square point
• In compact soil (sand, gravel, or stiff clay), the pile should have an iron or steel shoe

Protective Measures

• Piles driven in or exposed to salt water should be thoroughly impregnated to prevent damage

Pile Spacing

• Piles should be 2-3 ft. on centers with a maximum allowable load of 20 tons
• The tops should be cut off at or below the low water mark to prevent decay
• Cap the Piles with concrete, timber or steel grillage

Concrete Piles

• Possess advantages over wood, are used in places where wooden piles can be driven, and where wooden piles would be subject to decay or deterioration
• Are advantageous for land foundations where the permanent ground water is at a considerable depth.
• In practice concrete piles are generally reinforced using molded before driving, or molded in place

Pre-Cast Piles

• Molded in a yard or at the site and allowed to cure for 4 weeks before using
• Provide a cast-iron point
• A driving head in which a cushion of sand, rope or other material is utilized
• Concrete piles are often sunk using water-jet

Cast-In-Place Piles

• Constructed in the ground, often reinforced
• A hollow steel tube, typically furnished with a tight-fitting collapsible steel core, is driven into the soil
• Then its core is collapsed, removed, and the steel shell filled with concrete
• A steel tube is fitted at the bottom with a conical cast-iron point and driven into the ground
• The concrete is poured into the hole formed as the steel tube is withdrawn then forms into the steel tube
• Then it is gradually withdrawn with forming a uncased pile

Steel Piles

• Concrete-filled steel pipes typically made to bear on rock or hard pan.
• The pipes are 10-18 inches in diameter and having of 3/8 to 5/8 inches in thickness and driven in sections with a steam-hammer.
• Internal sleeves by means of cast-iron or steel re-driven sections are added, then cleaned out by air or similar tools & concreted

Composite Piles

• Combination timber and concrete or steel and concrete
• Timber piles have concrete coatings

Caisson Foundations

• Cast-in-place; plain or reinforced concrete piers
• Formed by boring or excavating a shaft, filling it with concrete

Foundation Walls, Basement Construction, Cisterns

• Foundation walls support the superstructure above and enclose a basement or crawl space
• They must be designed to resist earth pressure and anchor the superstructure against wind/seismic forces

Types of Reinforced Concrete Columns

• Short columns
• Long columns

Short Columns

• Occur when the unsupported height is not greater than ten times the shortest lateral dimension of the cross section

Long Columns

• Occur when the unsupported height is more than ten times the shortest lateral dimension of the cross section

Types of RC Columns

• Include tied and spiral columns

Tied Columns

• Contain longitudinal bars and lateral ties
• The effective sectional area is 1-8%
• They should have at least 4 bars of a minimum size of #5

Lateral Tiles

• Shall be at least 3/8" (10 mm) diameter and shall be spaced apart not over than 16 bar diameters, 48 tie diameters, or the least dimension of the column
• Where there are more than four vertical bars, additional ties should be provided so that every longitudinal bar will be firmly held in its designed position
• The reinforcement for tied columns shall be protected by a covering of concrete, cast monolithically with the core, of at least 1-1/2" (38mm) thickness

Column Guidelines

• Vertical steel reinforcement should not be less than 1% or more than 8% of cross-sectional area, nor less than 5 - #4 bars.

Vertical Reinforcement

• Must be no less than 1% or 4% of cross-sectional area, or #4 bars or greater.

Ties Requirements

• Are 1/2" diameter, spacing should be no more than 48x the diameter or 16x the bars in diameter for lateral reinforcement
• Have min 3/8" diameter spaced in 3" segments or less

Spiral Columns

• Spiral columns are columns with longitudinal bars and continuously hooped Spiral columns, ratio is not 1-8% and shall contain bars numbered 6 shall be #5

Spiral Reinforcement

• Min-size of 3/8 consist of spaced at consistent rates with vertical bars that shall also have have to be anchored
• The center shall not exceed 3" center to center spacing and at least 1-3/8.

Dowel Bars

• Short bars used to transfer stress from columns to footings
• There must be at least one, with a cross area greater than that of longitudinal bars

Reinforcement Extension

• For plain bars, not less than 50 bars diameter, and 40 for deformed bars

Reinforced Concrete Column Types

• Composite Columns - Structural steel columns embedded into the centre of a spiral column
• Combined Columns - Has wire messe surrounded, reinforced w/ at least 7 cm of area in the inner face and outer cover
• Lally Columns - Fabricates steel pipes fitted with girder/girt filled plates then filled with grout to prevent corrosion

One-Way Slabs

• A main tensile reinforcement, tensile is along the shortest with continuous slab being alternately bent up w/ an angle of up to 30 to 45 degrees w/ quarter supporting joint. For a singular length the slabs can be up to quarter parts.

One Way Bars

• In addition to tensile, temperature ones are are provided going directionally

Coverings

• Has at least 20 mm/35" covering to slab reinforcements

One-Way Joist or Ribbed Slabs

• Composed of length of medium loads used in economical floor structural constructions
• A "T-Beam is is composed of adjacent parts where the webbing and ring sections are composed of clay tile, blocks and structural material; commonly referred to is the support rib distribution

Two-Way Slabs

• Typically has beams & walls installed parallel w/ bars that meet perpendicular to each other and may be applied in four supporting joints.
• This can be rectangular due in varying long length supports

Two Way strips

• Where there's a flooring design a "Column & middle" must take course along the column.
• It's important for the floor that there must be space for short load transferring connections

Two way construction applications

• Has high efficient application due "Sq or close to sq" application is needed w/ heavy load applications
• A "Rule of thumb depth application" must be perimetered in ratio

Two way Waffle Slab

• Commonly re-enforces the area and helps in greater resistance for supporting

Two way flat platers

• Uniform/constant thickness on supporting loads w/o additional support, has lower strength qualities but high structural resistance to Hotel Construction
• Possesses constant re-enforcement where column stability is important

Two way construction

• For increased resistance the area is thickened by supports and commonly used by column connections in various sections

Inflat Panels

• Typically has ratios to the column in both length to side and typically supported by 1:33

Slab Panel and Diameter Ratios

• A thickness if no drops is present then it must then at least L/36 in diameter but if diameters are present over L/40 area is needed where capital is 0.2 - 0.25L"

Reinforcing techniques for flat panels & slates

• Includes: 2 way, 3 way, 4 way systems/columns and has square resistant reinforcement styles

Reinforced Concrete Beams

• Transverse the overall loads with a girthier supporting the lesser/smaller beams in ratio for a gritting implementation/application

Concrete Beam Design

• There can be two supports made at each end but be lengthened along the top with splices & support in its column structure

Typical Bending Styles

• Simple Beams - Singular section, nothing resistant at its ends/support
• Cant Beams - Section supporting area that projects out or more its supports
• Continuous Beam Supports -

1-Sided beam Tension Styles

• Tension can provide the resistance at which its supported is by steel material