Reinforced Concrete Design Lecture Notes

50 English vocabulary flashcards summarizing key terms and definitions from the lecture on reinforced concrete design.

Concrete

A mixture of sand, gravel or crushed rock (aggregates) held together by a paste of cement and water; strong in compression but weak in tension.

Compressive Strength (f'c)

The capacity of concrete to resist axial load; ordinary values range from 3,000–4,000 psi (20–28 MPa) and can reach 9,000–10,000 psi for special applications.

Tensile Strength of Concrete

Roughly one-tenth of its compressive strength, requiring steel reinforcement to carry tensile forces.

Cement

The binding component of concrete; ordinary Portland cement (Type I) is the most common.

Aggregates

Fine and coarse particles making up 60–80 % of concrete volume and 70–85 % of its mass, influencing strength and durability.

Water-Cement Ratio

The mass ratio of water to cement; the most influential factor on compressive strength, with practical limits around 0.30–0.35.

Admixtures

Chemicals added during mixing to modify workability, strength, setting time, durability, or other concrete properties.

Steel

An iron-based alloy (primarily iron and carbon) valued for high strength and versatility in construction.

Steel Bar

A long metal rod, typically steel, used to reinforce concrete and resist tension.

Mild Steel Bar

Smooth-surfaced rebar commonly used for general construction; easy to weld and fabricate.

Deformed Steel Bar

Rebar with ribs, lugs, or indentations that improve bond with concrete and reduce slippage.

Corrosion-Resistant Steel Bar

Rebar treated or alloyed (e.g., rust converter) to improve resistance against corrosion.

Reinforced Concrete

Composite material in which steel reinforcement supplies tensile capacity that concrete lacks.

Advantages of Reinforced Concrete

High compressive strength, good tensile capacity with steel, fire/weather resistance, durability, and ability to be cast into varied shapes.

Disadvantages of Reinforced Concrete

Low native tensile strength, need for costly formwork and shoring, and relatively heavy members per unit strength.

Formwork

Temporary structures that shape and support fresh concrete until it hardens.

Shoring

Temporary supports used to keep formwork or structural elements in place until concrete gains sufficient strength.

Mixing

Combining cement, water, aggregates, and admixtures into a uniform blend.

Casting

Placing the mixed concrete into formwork to create the desired shape.

Curing

Maintaining adequate moisture and temperature to ensure proper hydration and strength development.

Modulus of Elasticity of Steel

Stiffness of steel; about 200,000 MPa (29,000 ksi) in typical design.

Yield Strength of Steel

Stress at which steel begins to deform plastically; common Philippine grades are 33 ksi (227 MPa), 40 ksi (274 MPa), and 60 ksi (414 MPa).

Modulus of Elasticity of Concrete

Slope of a chosen stress-strain line for concrete; no single value, often approximated by empirical formulas.

Poisson’s Ratio

Ratio of lateral to longitudinal strain, typically 0.11–0.21 (average ≈ 0.16).

Shrinkage

Volume reduction due to moisture loss, causing surface cracking especially under hot, windy conditions.

Creep

Time-dependent deformation under sustained load, leading to additional strain in the load direction.

Limit States

Conditions beyond which a structure becomes unfit; include ultimate and serviceability limit states.

Ultimate Limit State

State associated with structural collapse or loss of equilibrium of part or all of the structure.

Serviceability Limit State

State where durability, deflection, cracking, vibration, or similar factors make the structure unfit for use though not collapsed.

Allowable Stress Design (ASD)

Traditional method using service loads with no load factors; may be conservative or unsafe depending on conditions.

Strength or Load and Resistance Factor Design

Design method where material strengths are reduced and loads are factored upward, utilizing full material capacity for economical safety.

Balanced Design

A reinforced-concrete design proportioned so concrete and steel reach allowable stresses simultaneously at failure.

Under Reinforced Design

Design with less steel than balanced; steel yields before concrete crushes, leading to ductile failure.

Over Reinforced Design

Design with more steel than balanced; concrete crushes before steel yields, producing brittle failure.

Ductile Failure

Gradual, warning-type failure characterized by steel yielding and large deformations.

Brittle Failure

Sudden failure with little warning, often caused by concrete crushing in over-reinforced sections.

ASTM C39

Standard test method for determining compressive strength of cylindrical concrete specimens (molded cylinders and drilled cores).

ASTM C31

Standard practice for making, curing, protecting, and transporting concrete test specimens under field conditions.

Rebound Hammer Test

Non-destructive test that estimates concrete compressive strength by measuring surface rebound.

Concrete Coring

Destructive test involving extraction of cylindrical cores from existing concrete for strength evaluation.

Supplementary Cementitious Materials (SCMs)

Materials added to partially replace Portland cement, such as fly ash, slag cement, silica fume, and metakaolin.

Fly Ash

Pozzolanic by-product from coal combustion used as an SCM to improve workability and long-term strength.

Slag Cement

Ground granulated blast-furnace slag used as an SCM to enhance durability and reduce heat of hydration.

Silica Fume

Very fine amorphous silica used as an SCM to increase strength and reduce permeability.

Mixing Water Quality

Potable water is generally acceptable; non-potable water must be tested to ensure it does not harm strength or durability (e.g., avoid saltwater in reinforced concrete).

Age Effect on Strength

Concrete gains strength with age; 28-day strength is standard, but strength may continue increasing for years, especially under moist curing.

Seismic Importance Factor

Multiplier (e.g., 1.00, 1.25, 1.50) used to adjust design loads based on occupancy and post-earthquake functionality.

Stress-Strain Diagram of Steel

Graph showing elastic region, yield plateau, strain hardening, and ultimate fracture point for reinforcing steel.

Young’s Modulus

The slope of the initial linear portion of a material’s stress-strain curve; for steel ≈ 200 GPa, for concrete variable.