BT 3 - Lesson 1: Reinforced Concrete Construction

Reinforced Concrete

Concrete i which steel reinforcement is embedded in such a manner that 2 materials act together in resisting forces. Also caled Beton arme, Ferroconcrete

Plain Concrete

Concrete having no reinforcement, or reinforced only for drying shrinkage or thermal stresses

Ferrocement

Constructed of cement-sand mortar over wire mesh that has been preshaped over a mold

Cast-in-Place Concrete, Cast In-Situ, In-Situ Concrete

Concrete which is deposited in place where it is required to harden as part of the structure, as opposed to precast concrete

Reinforcement

A system of steel bars, strands, or wires for absorbing tensile, shearing and sometimes compressive stresses in a concrete member

Deformed Bar

A reinforcing bar hot-rolled with surface deformations to develop a greater bold with concrete

Tension Reinforcement

Reinforcement designed to absorb tensile stresses

Compression Reinforcement

Reinforcement designed to absorb compressive stresses

Balanced Section

A concrete section in which the tension reinforcement theoretically reaches its specified yield strength as the concrete in compression reaches its assumed ultimate strain.

A design so proportional such that the max. stresses in the concrete and steel are reach simultaneously so that they fail together

Overreinforced Section

The concrete in compression reaches its assumed ultimate strain before the tension reinforcement reaches it specified yield strength

A dangerous condition since failure of the section could occur instantaneously without warning. 

This type of design is not advisable because concrete fails abruptly in compression

Underreinforced Section

Tension reinforcement reaches its specified yield strength before the concrete in compression reaches its assumed ultimate strain

Underreinforced Section

Desirable condition since failure of the section would be preceded by large deformations, giving prior warning of impending collapse. In this particular type of design, steel fails first while concrete has not yet reached its allowable values but failure is gradual with steel yielding

Assumptions in Elastic Theory in Concrete

1. Plane section remains plane before and after bending occurs

2. Concrete is elastic; that is the stress of concrete varies from 0 at the neutral axis to max.

3. Concrete is not good in carrying tensions and only the steel bars are carrying all stresses due to bending which is tension

4. There must be no slippage between concrete and steel bars

Joseph Monier (France) - 1867

Used the concept of iron reinforcing bars (rebars) when he reinforced William Ward’s (US) flower pots using wire

Beam

A rigid structural member designed to carry and transfer tranverse loads across space to uspporting elements

Simple Beam

Having single span supported at its end w/o a restraint at the support

Semi-Continuous Beam

With 2 spans with or w/o restraint at the 2 extreme ends

Cantilever Beam

A beam supported on one end and other end projecting beyond support, beam or wall

Continuous Beam

A term applied to a beam that rests on more than 2 supports

T Beam

Part of the floor and beam unit when poured simultaneously thereby producing a monolithic structure where the portion of the slab at both sides of the beam serves as flangers of such beam

Reinforced Concrete Beam

A concrete beam designed to act together with longitudinal and web reinforcement in resisting applied forces, formed and placed along with slab it supports

Beam Nomenclature

Refers to the naming and labeling system used to identify beams in drawings, models, or schedules. This helps engineers, architects, and contractors coordinate structural layouts efficiently.

Effective Depth of Section

Depth of a concrete section measured from the compression face to the centroid of the tension reinforcement

Bar Spacing

Center-to-center spacing of parallel bars, the resulting clear distance between the bars being regulated by bar diameter, max. size of coarse aggregate, and thickness of concrete section

Span of Supports

Refers to the distances between posts, columns, or supporting walls

Concrete Cover

Amount of concrete required to proetect steel reinforcement from fire and corrosion, measured from the surface of reinforcement to outer surface of concrete section

Bond

Adhesion between 2 substances, as concrete and reinforcing bar

Bond Stress

Adhesive force per unit area of contact between a reinforcing bar and surrounding concrete developed at any section of a flexural member

Development Length

Length of embedded reinforcement required to develop the design strength of reinforcement at critical section

Embedment Length

Length of embedded reinforcement provide beyond a critical section

End Anchorage

Length of reinforcement or mechanical anchor or hook or combination thereof beyond point of 0 stress in reinforcement

Hook

Bend or curve given to the end of a tension bar to develop an equivalent embedment length, used where there is insufficient room to develop an embedment length

Longitudinal Reinforcement

Essentially parallel to horizontal surface of a slab or to the long axis of a concrete beam or column

Percentage Reinforcement

Ratio of effective area of reinforcement to effective of concrete at any section of reinforced concrete member, expressed as a %

Top Bar

Any of the longitudinal bars serving as tension reinforcement in the section of concrete beam or slab subj. to negative moment

Bottom Bar

Any of the longitudinal bars serving as tension reinforcement in the section of concrete beam or slab subj. to positive moment

Web Reinforcement

Reinforcement consisting of bent bars or stirrups, placed in a concrete beam to resist diagonal tension

Bent Bar

A longitudinal bar bent to an angle of 30 degrees or more with the axis of the concrete beam, perpendicular to and intersecting the cracking that could occur from diagonal tension

Bend Reinforcing Bars

Reinforcing bars that are bent up on or near the inflection point and are extended at the top of beam across the support towards the adjacent span

No Bent Bars