Podcast
Questions and Answers
What does the symbol 𝑳𝒅 represent in the context of reinforcement?
What does the symbol 𝑳𝒅 represent in the context of reinforcement?
- Length for compression
- Lap splice for tension
- Development length for tension (correct)
- Standard hook length
What is a consequence of a lack of bonding between steel bars and concrete?
What is a consequence of a lack of bonding between steel bars and concrete?
- Steel and concrete will act as a unit.
- Steel bars may pull loose from the concrete. (correct)
- Improved structural integrity.
- Bars will remain fixed in place.
Which modification factor accounts for the casting position of reinforcement?
Which modification factor accounts for the casting position of reinforcement?
- ψ𝑇
- ψ𝑡 (correct)
- ψ𝑐
- ψ𝑠
What is the primary function of development length in reinforced concrete?
What is the primary function of development length in reinforced concrete?
Which symbol represents the specified yield strength of steel?
Which symbol represents the specified yield strength of steel?
The lap splice for tension is denoted by which symbol?
The lap splice for tension is denoted by which symbol?
What must occur for steel and concrete to effectively function together in reinforced concrete?
What must occur for steel and concrete to effectively function together in reinforced concrete?
Which modification factor applies to the size of the reinforcement?
Which modification factor applies to the size of the reinforcement?
What is the modification factor for lightweight concrete when the tensile strength, $𝑓𝑐𝑡$, is specified?
What is the modification factor for lightweight concrete when the tensile strength, $𝑓𝑐𝑡$, is specified?
What is the modification factor for epoxy-coated or dual-coated reinforcement?
What is the modification factor for epoxy-coated or dual-coated reinforcement?
Which covers on hooks for 36mmØ bars result in a modification factor of 0.7?
Which covers on hooks for 36mmØ bars result in a modification factor of 0.7?
What is the modification factor for uncoated or zinc-coated reinforcement?
What is the modification factor for uncoated or zinc-coated reinforcement?
Which condition does not alter the modification factor from 1.0?
Which condition does not alter the modification factor from 1.0?
What is the modification factor for 90-degree hooks of 36mmØ bars with proper cover?
What is the modification factor for 90-degree hooks of 36mmØ bars with proper cover?
For lightweight concrete, what modification factor is indicated for the development of hooked bars in tension?
For lightweight concrete, what modification factor is indicated for the development of hooked bars in tension?
What is the modification factor that applies to other conditions that do not fit specific criteria?
What is the modification factor that applies to other conditions that do not fit specific criteria?
What is the clear spacing requirement for bars or wires that are being developed or lap-spliced?
What is the clear spacing requirement for bars or wires that are being developed or lap-spliced?
For deformed bars and wires in tension, which equation is used to calculate the development length (𝑳𝒅)?
For deformed bars and wires in tension, which equation is used to calculate the development length (𝑳𝒅)?
What is the maximum value that the confinement term (𝑐𝑏 + 𝑲𝑡𝑟) can reach?
What is the maximum value that the confinement term (𝑐𝑏 + 𝑲𝑡𝑟) can reach?
In which case can 𝑲𝑡𝑟 be set to zero as a design simplification?
In which case can 𝑲𝑡𝑟 be set to zero as a design simplification?
What is the condition for clear cover required for deformed bars and wires?
What is the condition for clear cover required for deformed bars and wires?
What is the minimum code requirement for development length for deformed bars working under normal conditions?
What is the minimum code requirement for development length for deformed bars working under normal conditions?
The factor 1.1 used in the equation for calculating the development length (𝑳𝒅) accounts for what?
The factor 1.1 used in the equation for calculating the development length (𝑳𝒅) accounts for what?
To ensure adequate development length, the spacing of bars must be at least how many times the diameter (𝑑𝑏)?
To ensure adequate development length, the spacing of bars must be at least how many times the diameter (𝑑𝑏)?
What should be done if the slab thickness 'd' is less than the required 'd_required'?
What should be done if the slab thickness 'd' is less than the required 'd_required'?
In calculating required main bar spacing, what should the spacing 's' not exceed?
In calculating required main bar spacing, what should the spacing 's' not exceed?
What does the variable ρ represent in the context provided?
What does the variable ρ represent in the context provided?
To find the required area of steel reinforcement 'As', which formula is used?
To find the required area of steel reinforcement 'As', which formula is used?
Which factor is NOT considered in calculating spacing of deformed shrinkage and temperature reinforcement?
Which factor is NOT considered in calculating spacing of deformed shrinkage and temperature reinforcement?
What is the purpose of checking ρ_min?
What is the purpose of checking ρ_min?
What does the notation 'Mu = Ø Bf' signify in the context?
What does the notation 'Mu = Ø Bf' signify in the context?
If the relationship between the variables indicates 'd' is adequate, what is the implication for the slab design?
If the relationship between the variables indicates 'd' is adequate, what is the implication for the slab design?
What does the factor $K_{tr}$ represent?
What does the factor $K_{tr}$ represent?
Which option represents $c_b$ correctly?
Which option represents $c_b$ correctly?
What is the modification factor for lightweight concrete under specified conditions?
What is the modification factor for lightweight concrete under specified conditions?
In which condition does an epoxy-coated reinforcement have a modification factor of 1.5?
In which condition does an epoxy-coated reinforcement have a modification factor of 1.5?
What is the value of the modification factor for uncoated reinforcement?
What is the value of the modification factor for uncoated reinforcement?
For standard hooks in tension, $L_{dh}$ must be the greater of which options?
For standard hooks in tension, $L_{dh}$ must be the greater of which options?
What factor applies to deformed bars 20mmØ and smaller?
What factor applies to deformed bars 20mmØ and smaller?
What is the maximum allowable product of $ψ_t$ and $ψ_e$?
What is the maximum allowable product of $ψ_t$ and $ψ_e$?
What condition leads to a modification factor of 1.3?
What condition leads to a modification factor of 1.3?
When does epoxy-coated reinforcement for all other conditions receive a modification factor of 1.2?
When does epoxy-coated reinforcement for all other conditions receive a modification factor of 1.2?
What is the coefficient for the exterior negative moment if the support is a column?
What is the coefficient for the exterior negative moment if the support is a column?
Which formula represents the Factored Moment M2 to be carried by the slab?
Which formula represents the Factored Moment M2 to be carried by the slab?
How is the effective depth 'd' calculated in slab design?
How is the effective depth 'd' calculated in slab design?
What should be done with the moments calculated in accordance with Section 406.5.2?
What should be done with the moments calculated in accordance with Section 406.5.2?
For beams with a ratio of the sum of column stiffnesses to beam stiffnesses exceeding 8, what is the implication for design?
For beams with a ratio of the sum of column stiffnesses to beam stiffnesses exceeding 8, what is the implication for design?
What is the approximate shear value $(V_u)$ at the exterior face of the first interior support?
What is the approximate shear value $(V_u)$ at the exterior face of the first interior support?
What must be checked after computing the effective depth and factored moment for a one-way slab?
What must be checked after computing the effective depth and factored moment for a one-way slab?
For slabs with spans not exceeding 3 meters, which design consideration is necessary?
For slabs with spans not exceeding 3 meters, which design consideration is necessary?
Flashcards
Development length (tension)
Development length (tension)
The length of a reinforcing bar required to develop its design strength in tension within the concrete.
Development length (compression)
Development length (compression)
The length of a reinforcing bar needed to develop its design strength in compression within the concrete.
Development length of standard hook
Development length of standard hook
The required length of a standard reinforcing bar hook to adequately develop its strength.
Lap splice for compression
Lap splice for compression
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Lap splice for tension
Lap splice for tension
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Straight extension
Straight extension
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Bond stress
Bond stress
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Reinforcing bar diameter
Reinforcing bar diameter
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Development Length (Ld)
Development Length (Ld)
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Spacing of deformed bars/wires
Spacing of deformed bars/wires
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Development length formula for deformed bars
Development length formula for deformed bars
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Confinement term (cb + Ktr)/db
Confinement term (cb + Ktr)/db
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Ktr
Ktr
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Transverse reinforcement (stirrups/ties)
Transverse reinforcement (stirrups/ties)
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Minimum clear spacing (bars/wires)
Minimum clear spacing (bars/wires)
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Cover (concrete)
Cover (concrete)
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KtR factor
KtR factor
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Modification Factor (Tension)
Modification Factor (Tension)
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Lightweight Concrete Modification Factor
Lightweight Concrete Modification Factor
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Epoxy-coated reinforcement Modification Factor
Epoxy-coated reinforcement Modification Factor
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Standard Hook Development (Ldh)
Standard Hook Development (Ldh)
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Casting Position Correction (ψt)
Casting Position Correction (ψt)
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Modification Factor (𝝀)
Modification Factor (𝝀)
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Modification Factor (𝛙𝒆)
Modification Factor (𝛙𝒆)
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Modification Factor (𝛙𝒄)
Modification Factor (𝛙𝒄)
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Lightweight Concrete
Lightweight Concrete
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Epoxy-coated Reinforcement
Epoxy-coated Reinforcement
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Hooked Bars
Hooked Bars
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Discontinuous Ends
Discontinuous Ends
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Minimum Slab Thickness
Minimum Slab Thickness
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Effective Depth (d)
Effective Depth (d)
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Factored Moment (M2)
Factored Moment (M2)
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Factored Load (Wu)
Factored Load (Wu)
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Exterior Negative Moment
Exterior Negative Moment
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Approximate Shears for Continuous Beams
Approximate Shears for Continuous Beams
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Column Stiffness
Column Stiffness
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Beam Stiffness
Beam Stiffness
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Slab Thickness Check
Slab Thickness Check
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Required Slab Thickness
Required Slab Thickness
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Reinforcement Ratio (ρ)
Reinforcement Ratio (ρ)
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Minimum Reinforcement Ratio (ρmin)
Minimum Reinforcement Ratio (ρmin)
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Required Area of Steel (As)
Required Area of Steel (As)
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Spacing of Main Bars
Spacing of Main Bars
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Temperature Bars
Temperature Bars
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Spacing of Temperature Bars
Spacing of Temperature Bars
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Study Notes
Introduction to Reinforced Concrete
- Concrete is a mixture of aggregates (sand, gravel, crushed rock) and cement paste (cement and water). Sometimes admixtures are added to change concrete properties.
- Reinforced concrete combines concrete with steel reinforcement to improve tensile strength (concrete has low tensile strength). Steel also resists compression forces.
- Aggregates make up roughly three-quarters of concrete volume. Fine aggregates are usually sand, and coarse aggregates are usually gravel or crushed stone. Material that passes a No. 4 sieve (about 6mm in size) is fine aggregate.
Notations & Symbols
- Dead Load (DL): load from a structure's weight
- Earthquake Load (E): load from earthquakes
- Live Load (LL): load resulting from the use of a structure
- Wind Load (W): load from wind
- Modulus of elasticity of concrete (Ec): a measure of how much a material deflects under stress
- Modulus of elasticity of steel (Es): a measure of how much steel deflects under stress
- Specified compressive stress of concrete (fc): the maximum compressive stress concrete can withstand
- Specified yield strength of steel (fy): the stress at which steel begins to yield
- Diameter of aggregates (dagg): the size of aggregates
- Diameter of bar (do): diameter of reinforcing steel bars
- Diameter of stirrups (ds): diameter of reinforcement used in stirrups
- Area of bar (A): area of a single reinforcing steel bar
Concrete Design Properties (NSCP 2015)
- Specified Compressive Strength (fc): Values are specified in construction documents. Limits and structural strength requirements are in tables within the code.
- Modulus of Elasticity (Ec): a calculated value for concrete based on its strength, age, loading type, and proportions of cement and aggregates. Calculations use equations.
Minimum Spacing and Bundled Reinforcement (NSCP 2015)
- Parallel non-prestressed reinforcement in horizontal layers has a minimum clear spacing of at least 25mm, the diameter of the bar (d1), and (4/3) * diameter of aggregates (dagg).
- Parallel non-prestressed reinforcement in multiple horizontal layers has a minimum clear spacing of 25mm between layers
- Longitudinal reinforcement in columns, pedestals, struts, and boundary elements in walls has a minimum clear spacing of at least 40mm, 1.5 times the bar diameter (1.5d), and (4/3) * diameter of aggregates (dagg)
- Bundled reinforcement is limited to a maximum of four bars in any one bundle in contact.
- Bundled bars require transverse reinforcement.
Concrete Cover Requirements (NSCP 2015)
- Non-prestressed cast-in-place concrete members require specific concrete cover to surround reinforcement. The amount of cover varies based on exposure conditions.
- Prestressed concrete members also require specific concrete cover for reinforcement, ducts, and end fittings.
Strength Reduction Factors (NSCP 2015)
- Strength reduction factor (Ø) is a factor used to modify the nominal strength of parts of a structure based on factors like moment, axial force, and other conditions. Specific values are found in the code.
Loads and Load Combinations (NSCP 2015)
- Dead Loads (DL): Loads of constant magnitude in a fixed location, e.g. the structure's weight and permanent fixtures.
- Live Loads (LL): Loads that vary in magnitude and position. Examples include people, equipment, materials.
- Environmental Loads: Loads from the environment like wind, temperature changes, earthquakes.
- Load Combinations: Specific combinations of loads are used for design in the code.
Arrangement of Reinforcing Bars (Rectangular Beams)
- For maximum efficiency in rectangular beams, reinforcement bars are arranged to maximize the effective depth of reinforcement.
- Minimum cover for beams (40mm) and minimum spacing between parallel bars (25mm or bar diameter) are required.
Analysis and Design of Beams for Flexure
- Steel and concrete have different strengths and behaviors when stressed, so these need to be accounted for in the design.
- Steel yield strength and concrete compressive stress govern design.
Types of Failures and Strain Limits
- Tension-controlled section: Steel yields before concrete reaches maximum strength.
- Balanced section: Steel and concrete fail simultaneously.
- Compression-controlled section: Concrete fails before steel yields.
T-Beams
- T-beams have a wider flange section to support loads efficiently and are analyzed as a combination of the web and flange. The width of the flange varies depending on the web and support locations, as specified in tables in the code.
- Analysis is different depending on whether the flange is in compression or tension.
Doubly Reinforced Beams
- If moments exceed the capabilities of the concrete alone, compression reinforcement is added.
Analysis and Design of One-Way Slabs
- One-way slabs bend in one direction perpendicular to the supports
- The minimum slab thickness (h) varies depending on support conditions, as specified in tables in the code.
- Minimum areas of steel reinforcement needed to meet code requirements are based on the span length and load conditions.
Analysis of Continuous Beams and One-Way Slabs
- Coefficients are used for determining moment and shear based on the span length and load conditions in continuous beams and one-way slabs. Values are in tables, according to the supported condition.
Shear in Beams
- Beams need to be designed for both shear and bending moment to avoid failure.
- Code specifies requirements for calculating shear forces based on the factored load Vu and nominal shear strength of concrete (Ve) and reinforcement (Vs)
- Code limits spacing of stirrups, and areas.
Torsion in Beams
- Torsion resistance needs to be accounted for in some situations.
- There are methods for calculating and designing stirrups to resist torsion. The code provides tables and formulas based on the structural member and load conditions.
Short Columns
- Columns are subject to axial loads and bending.
- The code provides criteria for classifying columns, determining nominal load capacity based on material properties, and the limits of reinforcement.
Long/Slender Columns
- Slender columns magnify moments, requiring special procedures to account for the impact on capacity.
- Slenderness ratios, moment magnification, and other factors govern design in long columns.
- Charts (alignment charts) and formulas are used to account for these conditions and magnification factors.
Bond, Development Length, Hooks and Splices of Reinforcement
- Bond stresses are the stresses in the concrete that transfer load from steel to concrete to anchor the reinforcement at its ends
- Development lengths are required to anchor and stress the steel. There are rules for minimum lengths, considering hooked bars and splices. Code provides tables for these values based on the concrete and steel properties and location,
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