CELE Reinforced & Prestressed Concrete — Reinforced Concrete SlabsConcept Map

Concept

One-Way vs Two-Way Slab Classification

Sub Concepts

• Span ratio criteria (long/short ≥ 2)
• Support conditions
• Load distribution patterns
• Bending behavior

Relationship To Central

Foundational classification determining design approach and analysis method

Concept

Minimum Thickness (Deflection Control)

Sub Concepts

• Support condition formulas (L/20, L/24, L/28, L/10)
• Yield strength adjustment factor
• NSCP 2015 provisions
• Cantilever considerations

Relationship To Central

Critical requirement to prevent excessive deflection without explicit checks

Concept

Flexural Design per Metre Strip

Sub Concepts

• Unit strip analysis (b = 1000 mm)
• Moment calculation (Mu)
• Moment strength (Rn = Mu/φbd²)
• Steel ratio computation (ρ)
• Required reinforcement (As)
• Bar spacing conversion (s = Ab×1000/As)

Relationship To Central

Main structural design methodology for slab capacity

Concept

Shrinkage and Temperature Steel

Sub Concepts

• Minimum ratio (ρtemp = 0.0018 for fy = 415–420)
• Alternative ratio for fy = 275
• Placement perpendicular to main bars
• Spacing limits (5h, 450 mm max)

Relationship To Central

Essential secondary reinforcement perpendicular to main steel

Concept

Two-Way Slab Analysis Methods

Sub Concepts

• Coefficient method (on stiff beams)
• Direct Design Method (DDM) on columns
• Equivalent Frame Method (EFM)
• Static moment distribution (Mo = wuL₂Ln²/8)
• Column and middle strip moments

Relationship To Central

Advanced analysis for panels supporting loads in both directions

Concept

Reinforcement Detailing and Limits

Sub Concepts

• Main bar spacing limits (3h, 450 mm)
• Temperature bar spacing (5h, 450 mm)
• Minimum steel ratios
• Bar size and development length
• Curtailment requirements

Relationship To Central

Practical construction and crack-control requirements

Concept

Code Provisions and Standards

Sub Concepts

• NSCP 2015 (National Structural Code of the Philippines)
• ACI 318 (American Concrete Institute)
• RA 544 (Philippine Building Safety Law)
• AISC 360 (relevant for composite action)

Relationship To Central

Regulatory framework governing all slab design decisions

To

Flexural Design per Metre Strip

From

One-Way vs Two-Way Slab Classification

Strength

strong

Relationship

Classification determines whether single-direction or dual-direction analysis is performed; one-way uses strip method directly

To

Flexural Design per Metre Strip

From

Minimum Thickness (Deflection Control)

Strength

strong

Relationship

Minimum thickness establishes the effective depth d available for moment capacity; adequate thickness ensures structural depth for reinforcement

To

Shrinkage and Temperature Steel

From

Flexural Design per Metre Strip

Strength

strong

Relationship

After main flexural steel is determined, perpendicular temperature steel is designed to prevent shrinkage cracking; minimum ratio may govern total steel

To

Flexural Design per Metre Strip

From

Reinforcement Detailing and Limits

Strength

strong

Relationship

Spacing limits constrain the practical application of calculated steel areas; bar selection and spacing are derived from design area

To

Shrinkage and Temperature Steel

From

Reinforcement Detailing and Limits

Strength

strong

Relationship

Both main and temperature steel must satisfy independent spacing limits (3h vs 5h); limits ensure crack control and constructability

To

Flexural Design per Metre Strip

From

Two-Way Slab Analysis Methods

Strength

strong

Relationship

Two-way analysis methods (coefficient or DDM) produce moment distributions that are then designed using the same per-metre strip flexural methodology

To

Two-Way Slab Analysis Methods

From

One-Way vs Two-Way Slab Classification

Strength

strong

Relationship

Two-way classification triggers the need for specialized analysis methods (coefficient method, DDM, or EFM) not required for one-way slabs

To

Minimum Thickness (Deflection Control)

From

Code Provisions and Standards

Strength

strong

Relationship

NSCP 2015 and ACI 318 define the minimum thickness formulas (L/20, L/24, etc.) and adjustment factors for different yield strengths

To

Shrinkage and Temperature Steel

From

Code Provisions and Standards

Strength

strong

Relationship

NSCP 2015 and ACI 318 mandate minimum ratios (0.0018 or 0.0020) and spacing limits for temperature steel

To

Two-Way Slab Analysis Methods

From

Code Provisions and Standards

Strength

strong

Relationship

NSCP 2015 and ACI 318 prescribe coefficient values, DDM assumptions, and static moment distribution rules for two-way slabs

To

Reinforcement Detailing and Limits

From

Flexural Design per Metre Strip

Strength

moderate

Relationship

The calculated steel area (As) is converted to practical bar spacing using development length, splice requirements, and spacing limits from detailing rules

To

Reinforcement Detailing and Limits

From

One-Way vs Two-Way Slab Classification

Strength

moderate

Relationship

Classification affects curtailment patterns and reinforcement continuity; one-way slabs typically have simpler curtailment than two-way panels