General Construction In Steel – Code of Practice

IS 800:2007 – Scope & Basis for Design

The Scope of IS 800 covers the general requirements for design, fabrication, and erection of structural steel works.

Key Points from Clause 3.1 & 5.1 (Basis for Design):

• Design Philosophy: Limit State Design (LSD) method is adopted.

• Load Combinations: As per IS 875 (Part 1 to 5).

• Material Properties: Use characteristic values of steel strength (fy) from IS 2062 or IS 808.

• Design Strength:
  [ f_{d} = \frac{f_y}{\gamma_m} ] where (\gamma_m) = partial safety factor for material (usually 1.10 to 1.15).

• Design Loads: Include dead, live, wind, seismic loads as per relevant IS codes.

• Structural Systems: Applicable for rolled, built-up, welded steel sections.

Common Tables & Specifications:

Summary:

• Scope: Structural steel design using Limit State Method.
• Design Basis: Material strength, load combinations, safety factors.
• Codes Referenced: IS 875 (loads), IS 2062 (steel), IS 800 (design).

flowchart LR
    A[Loadings (IS 875)] --> B[Design Strength (IS 2062)]
    B --> C[Limit State Design (IS 800)]
    C --> D[Structural Steel Design]

This concise framework guides all steel structure design under IS 800.

IS 800: Materials - Key Formulas, Tables, and Specifications

1. Material Properties (Clause 2.1)

• Use nominal values as characteristic values for design.
• Yield stress (fy), Ultimate tensile stress (fu), and Elongation (%) are key parameters.

2. Tensile Properties of Structural Steel (Table 1, Clause 1.3.119)

(Refer IS 800 Table 1 for full details)

3. Common Specifications (Clause 1.5)

• Bolts & Nuts: IS 1367 (high strength bolts), IS 6623 (nuts)
• Washers: IS 5369, IS 5370, IS 5372, IS 5374
• Welding Electrodes: IS 6419, IS 6560
• Structural Steel Plates & Sections: IS 513, IS 814

4. Design Use

• Use fy as design yield strength.
• For bolted connections, use bolt grade properties (e.g., 8.8, 10.9).
• For welding, follow electrode specifications and welding procedures per IS codes.

flowchart TD
    A[Structural Steel] --> B[Yield Stress (fy)]
    A --> C[Ultimate Tensile Stress (fu)]
    A --> D[Elongation %]
    B --> E[Design Strength]
    C --> E
    D --> E
    E --> F[Member Design]

Summary: IS 800 provides nominal material values (

IS 800: General Design Requirements (Section 3)

Key Points from Clause 3.1 - Basis for Design:

• Design shall ensure safety, serviceability, and economy.
• Loads and load combinations as per relevant IS codes (e.g., IS 875).
• Material properties as per IS 800 and related standards.
• Stability against buckling, lateral-torsional buckling, and local buckling must be checked.
• Limit state design philosophy is adopted.

Important Specifications:

• Design strength: ( f_d = \frac{f_y}{\gamma_m} )

  • ( f_y ) = Yield strength of steel
  • ( \gamma_m ) = Partial safety factor (typically 1.10 to 1.15)

• Load combinations (simplified example):

  Load Case	Combination
  1	( 1.5 \times \text{Dead Load} )
  2	( 1.2 \times \text{Dead Load} + 1.6 \times \text{Live Load} )
  3	( 1.2 \times \text{Dead Load} + 1.6 \times \text{Wind Load} )

Design Checks Include:

• Strength (axial, bending, shear)
• Serviceability (deflection limits)
• Stability (buckling resistance)

flowchart TD
    A[Loads & Material Properties] --> B[Design Strength & Safety Factors]
    B --> C[Structural Analysis]
    C --> D[Check Strength & Serviceability]
    D --> E[Stability Checks]
    E --> F[Safe & Economical Design]

For detailed tables and formulas, refer to IS 800 Section 3 and related clauses.

IS 800: Loads and Forces (Clauses 3.2 & 12.2)

Key Points:

• Clause 3.2 (Loads and Forces):
  Defines types of loads acting on structures:

  • Dead Load (DL)
  • Live Load (LL)
  • Wind Load (WL)
  • Earthquake Load (EL)
  • Other loads (snow, temperature, etc.)

• Clause 12.2 (Load Combinations):
  Specifies load factors and combinations for design (Limit State Method):

Load Factor Summary:

• Dead Load (DL): 1.5
• Live Load (LL): 1.5
• Wind Load (WL): 1.5
• Earthquake Load (EL): 1.5
• Serviceability combinations use lower factors (e.g., 1.0 for DL and LL)

Wind Load Formula (from IS 875 Part 3):

[ P = 0.6 \times V^2 \times K_1 \times K_2 \times K_3 \times A ]

• (P) = design wind pressure (N/m²)
• (V) = basic wind speed (m/s)
• (K_1) = terrain, height & structure size factor
• (K_2) = topography factor
• (K_3) = importance factor
• (A) = projected area (m²)

Earthquake Load (IS 1893):

[ E = A_h \times W ]

• (E) = design seismic force
• (A_h) = design horizontal seismic coefficient
• (W) = seismic weight of the structure

IS 800 - Fire Resistance Key Points (Clause 16.11)

Fire Resistance Rating (Tables 31 & 32)

Notes:

• Protection thickness excludes any finish.
• Hollow protections may have air cavities; thickness varies accordingly.
• Solid protections typically use concrete or lightweight concrete.
• Fire resistance levels: 0.5h, 1h, 1.5h, 2h, 3h, 4h as per requirement.

Quick Reference Formula for Fire Protection Thickness:

[ t = \text{Thickness required as per Table 31 or 32 for desired fire rating} ]

Where:

• ( t ) = thickness of fire protection material (mm)
• Fire rating = 1h, 1.5h, 2h, 3h, or 4h

Summary Diagram: Fire Protection Layers on Steel Column

graph LR

IS 800: Design of Tension Members (Clause 11.2 & Section 6)

Key Points & Formulas:

• Tension Members: Members subjected to axial tensile force only.

• Effective Net Area (Aₙ):
  [ A_n = A_g - \sum \text{(Area of holes)} \times \text{(Reduction factor)} ] where ( A_g ) = Gross cross-sectional area.

• Design Strength:
  [ P_u = 0.9 \times f_y \times A_n ]

  • ( f_y ) = Yield strength of steel (MPa)
  • 0.9 = Reduction factor for net area

• Net Area Reduction: For bolted connections, reduce area by hole diameter plus clearance: [ d = \text{Bolt diameter} + 2 \text{ mm (clearance)} ]

• Clause 5.4 Factors:
  Ultimate strength governed by:

  • Yielding of gross section
  • Fracture of net section

• Check Both:
  [ P_u \leq \min(0.9 f_y A_n, f_y A_g) ]

Typical Table: Hole Diameter for Bolts

flowchart LR
    A[Tension Member] --> B[Calculate Gross Area (A_g)]
    B --> C[Subtract Hole Areas → Net Area (A_n)]
    C --> D[Calculate Design Strength: 0.9 × f_y × A_n]
    D --> E[Check Yielding: f_y × A_g]
    E --> F{Design Strength = Min(Net Section, Gross Section)}

Summary: Design tension members by calculating net area considering bolt holes, then apply (0.9 f_y A_n) for fracture and (f_y A_g) for yielding checks, taking the lesser as design strength.

IS 800: Design Details (Clause 7.3) & Basis for Design (Clause 3.1)

Key Points from Clause 7.3 (Design Details)

• Connections: Must ensure adequate strength, stiffness, and ductility.
• Welds and Bolts: Follow prescribed sizes, types, and spacing.
• Plates & Sections: Thickness and dimensions per design loads.
• Allowable tolerances: Fabrication and erection tolerances as per IS 800.

Basis for Design (Clause 3.1)

• Design per Limit State Method.
• Use factored loads: ( \text{Design Load} = \text{Load} \times \text{Load Factor} ).
• Material properties as per IS 800 and relevant IS codes.
• Safety factors incorporated in design strength.

Important Formulas

• Design Strength of Bolt in Shear:

[ P_{bs} = 0.6 \times f_u \times A_s ]

Where:
( f_u ) = ultimate tensile strength of bolt
( A_s ) = tensile stress area of bolt

• Design Strength of Weld:

[ P_{w} = 0.7 \times f_{uw} \times A_w ]

Where:
( f_{uw} ) = ultimate tensile strength of weld metal
( A_w ) = effective throat area of weld

Typical Tables (from IS 800)

flowchart LR
    A[Loads] --> B[Factored Loads]
    B --> C[Member Design]
    C --> D[Connection Design]
    D --> E[Bolts & Welds]
    E --> F[Check Strength & Stiffness]

Summary: IS 800 Clause 7.3 mandates detailed design for connections ensuring strength and ductility

IS 800: Design of Beams — Key Points

1. Design Strength in Bending (Clause 8.2)

• Design bending strength, ( M_u ):

[ M_u \leq \phi_b \times M_d ]

where

• ( M_d = f_y \times Z ) (Design moment capacity)
• ( f_y ) = Yield strength of steel
• ( Z ) = Section modulus (elastic or plastic depending on design)
• ( \phi_b ) = Strength reduction factor (typically 0.9)

2. Plastic Properties of Beams (Annex H, Table 46)

• Provides sectional properties for ISMB, ISWB, ISLB, ISHB beams:

3. Design of Beams and Plate Girders with Solid Webs (Clause 8.6)

• Check for:
  • Flexural strength
  • Shear strength
  • Web buckling (local and shear buckling)
  • Lateral-torsional buckling

Summary Formula for Flexural Design:

[ M_u \leq f_y \times Z_p ]

where ( Z_p ) is the plastic section modulus from Table 46.

Visual Concept: Beam

IS 800: Design of Compression Members (Clause 7.1 & 7.2)

Key Formulas

1. Design Strength of Compression Member:

[ P_d = \frac{0.9 \times f_{cd} \times A_{ef}}{\gamma_{m}} ]

• (P_d): Design axial load capacity
• (f_{cd}): Design compressive stress (depends on slenderness)
• (A_{ef}): Effective cross-sectional area
• (\gamma_m): Partial safety factor (usually 1.5)

2. Slenderness Ratio:

[ \lambda = \frac{L_e}{r} ]

• (L_e): Effective length (depends on end conditions)
• (r): Radius of gyration of the cross-section

3. Effective Length ((L_e)) Calculation (Clause 7.2):

• Depends on end conditions (fixed, pinned, free) and member restraint.
• Typical values from IS 800 Table or:

[ L_e = K \times L ]

where (L) = actual length of member.

Important Tables (from IS 800)

Design Details (Clause 7.3)

• Use effective area (A_{ef}) after considering local buckling.
• Use stiffeners for laced/battened columns (Clauses 7.6, 7.7).
• Column bases as per Clause 7.4.

IS 800: Design of Connections (Clause 10.6)

Key Specifications & Formulas:

• Connection Classification (Fig. 33 - Bjørhovde):

  • Connections are classified by type (A to H) such as single web angle, double web angle, end plate, T-stub, header plate, etc.

• Curve-Fitting Constants (Table 44, Clause F-4.3.2):

• Secant Stiffness for Preliminary Analysis (Table 45):

Notations:

• d = Depth of beam (mm)
• da = Depth of angle (mm)
• db = Bolt diameter (mm)
• g = Gauge distance (mm

IS 800: Key Formulas & Specs for Bolts and Fasteners

1. Effective Area of Bolts (Clause 10.3.1)

• Effective tensile stress area ( A_e ) depends on bolt diameter and thread profile.

• For standard bolts, use tabulated values (e.g., IS 1367) or approximate as:

  [ A_e = \frac{\pi}{4} (d - 0.9382 \times p)^2 ]

  where ( d ) = nominal diameter, ( p ) = pitch of thread.

2. Actual Stresses in Fasteners (Clause 11.6.2)

• Tensile stress in bolt:

  [ f_t = \frac{P}{A_e} ]

• Shear stress for single shear:

  [ f_v = \frac{V}{A_s} ]

  where ( P ) = axial load, ( V ) = shear load, ( A_s ) = shear area (usually minor diameter area).

3. Bearing Type Bolts (Clause 10.3)

• Bearing stress on connected plate:

  [ f_b = \frac{P}{d \times t} ]

  where ( d ) = bolt diameter, ( t ) = thickness of connected plate.

4. Location Details of Fasteners (Clause 10.2)

• Minimum edge distance = ( 1.5 \times d )
• Minimum spacing between bolts = ( 2.5 \times d )

Summary Table: Bolt Parameters

IS 800: Seismic Design and Bracing Key Points

1. Bracing Types (Clause 12.7.1.2 & 12.8.1.2)

• Allowed: Diagonal and X-bracing only.
• Not Permitted: K-bracing in seismic-resisting systems.
• For V and inverted V bracing, consult specialist literature.

2. Effective Length Factor for Columns (Annex D, Clause 7.2.2)

• Non-sway frames (Braced):

[ K = \sqrt{[1 + 0.145(B_1 + B_2) - 0.265 B_1 B_2]^2 - 0.364(B_1 + B_2) - 0.247 B_1 B_2} ]

• Sway frames (Moment Resisting):

[ K = \sqrt{ \frac{1 - 0.2(B_1 + B_2) - 0.12 B_1 B_2}{1 - 0.8(B_1 + B_2) + 0.6 B_1 B_2} } ]

• (B_1, B_2 = \frac{\Sigma K_c}{\Sigma K_p}) (stiffness ratios of columns to beams)

• Use Table 35 for correction factor (C) based on end conditions (Pinned, Rigid, Fixed).

3. Partial Sway Bracing (Clause 3.3, Table B-3.3)

Diagonal strut area (A) for infill wall panels:

[ A = K_c \sum K_e \cdot h \left(\frac{h}{b}\right) \left[1 + \left(\frac{h}{b}\right)^2\right]^{3/2} ]

• (h) = storey height, (b) = braced bay width
• (\sum K_e) = sum of stiffness (I/L) of columns
• (E_s p) = spring stiffness of panels, calculated from panel thickness and modulus.

Summary Table: Bracing & Effective Length

IS 800: Fabrication and Erection - Key Formulas, Tables, and Specs

1. General Requirements (Clause 1.1.3)

• Fabrication and erection quality must align with design assumptions.
• Additional requirements may apply per project specs, structure type, or construction method.

2. Handling & Safety (Clause 17.13.4.1)

• Skilled workers only.
• Use tested lifting devices and wire rope slings of correct size.
• Devices must be well maintained and operated by experienced personnel.

3. Tolerances

a) Fabrication Tolerances

• Refer IS 7215 for fabrication tolerances.

b) Erection Tolerances

• Refer IS 12843 for erection tolerances.

c) Welding Guidance

• Refer IS 9595 for fabrication by welding.

4. Straightness Tolerances (Table 34, Clause 7.13.3.1)

• L = Length between lateral restraints.
• Z = Length between lateral restraints (similar to L).

Summary:

• Fabrication & erection must meet IS 7215 & IS 12843 tolerances.
• Use skilled labor and tested equipment.
• Maintain straightness within 0.1% to 0.2% of member length depending on section type.

flowchart TD
    A[Fabrication] --> B[Quality per IS 7215]
    C[Erection] --> D[Quality per IS 12843]
    E[Handling] --> F[Skilled Workers + Tested Equipment]
    G[Straightness] --> H[0.001L (solid) or 0.002L (hollow)]
    B & D & F & H --> I[Safe & Quality Structure]

For detailed project-specific requirements, always cross-check with relevant standards and specifications.

IS 800: Testing and Acceptance Criteria - Key Points

1. Acceptance Test Load (Clause 14.2.1)

• Purpose: Non-destructive test to verify structural performance.
• Load for acceptance test, ( F_{test} ):
  Determined based on design loads and agreed limits to avoid permanent damage.
• Note: Some permanent distortion may occur without failure; this must be pre-agreed.

2. Criteria for Acceptance (Clause 14.5)

• Acceptance is based on:
  • No visible failure or excessive deflection.
  • Deformations within permissible limits.
  • No significant cracks or instability.
• Specific limits depend on structure type and design.

3. Inspection and Testing (Clause 17.12)

• Includes:
  • Visual inspection.
  • Dimensional checks.
  • Non-destructive testing (NDT) methods.
  • Load tests as per design requirements.

Summary Table: Acceptance Test Load and Criteria

Typical Acceptance Test Load Formula (Conceptual)

[ F_{test} = \alpha \times F_{design} ]

• ( \alpha ) = factor (>1) depending on structure and safety margin.
• ( F_{design} ) = design load as per IS 800.

flowchart TD
    A[Start: Structural Element Ready] --> B[Apply Acceptance Test Load \(F_{test}\)]
    B --> C{Observe Structural Response}
    C -->|No Failure & Deflection OK| D[Accept Structure]
    C -->|Failure or Excessive Deflection| E[Reject or Repair]
    D --> F[Complete Testing]
    E --> F

Note: Always refer to the detailed clauses of IS 800 for specific values and conditions related to your project type.

IS 800: Durability Key Points

Definition (Clause 1.3.31)

• Durability: Ability of material/structure to resist deterioration over long periods.

Factors Affecting Durability (Clause 5.6.3)

• Environment: Aggressive (marine, industrial) or mild.
• Degree of Exposure: Atmospheric conditions, moisture, chemicals.
• Shape & Detail: Avoid water traps, sharp corners.
• Protective Measures: Coatings, galvanization, paint.
• Maintenance: Ease and frequency of upkeep.

Requirements for Durability (Clause 15.2)

• Use materials and protective treatments suitable for exposure.
• Design to prevent corrosion and deterioration.
• Ensure proper cover to reinforcement in concrete.
• Specify maintenance schedules.

Criteria for Acceptance (Clause 14.5)

• Materials and workmanship must meet durability standards.
• Inspection for protective coatings and cover thickness.
• Testing for corrosion resistance where applicable.

Typical Durability-Related Specifications in IS 800:

flowchart TD
    A[Durability] --> B[Environment]
    A --> C[Exposure Degree]
    A --> D[Member Shape & Detail]
    A --> E[Protective Measures]
    A --> F[Maintenance]

Summary: Design and material selection per IS 800 clauses ensure structural durability by addressing environmental exposure, protective measures, and maintenance.

Fire Protection & Temperature Effects (IS 800 - Clause 16.11 & 16.6.3)

1. Fire Resistance Rating (Tables 31 & 32)

2. Temperature Effects (Clause 16.6.3)

Steel temperature-time curves from standard fire tests can be used if:

• Fire protection system and thickness match or exceed the prototype.
• Fire exposure conditions are identical.
• Surface area to mass ratio ≤ prototype.
• Stickability of fire protection demonstrated if tested unloaded.

3. Thickness Formula (Clause 5.2)

For four-sided fire exposure:

[ t = 5.2 + 0.022 \times T + 2 + 3311 \times 0.433T ]

(where t = thickness, T = temperature/time parameter)

Summary Diagram: Fire Protection Layers on Steel Column

graph TD
A[Steel Column] --> B[Fire Protection Material]
B --> C[Metal Lathing]
B --> D[Gypsum Plaster]
B --> E[Concrete Encasing]

Key points:

• Protection thickness depends on fire rating (1h to 4h).
• Different materials (gypsum, plasterboard, concrete) have specified thicknesses.
• Ensure fire protection