Handbook on Structures with Steel Portal Frames (Without Cranes)

Scope Summary - IS SP:40 (Steel Portal Frames)

Applicable Spans & Heights:

Design Parameters:

• Frame Spacing: 4.5 m or 6.0 m
• Wind Zones: I, II, III
• Earthquake Zones: I to V
• Support Types: Fixed and Hinged (both analyzed)
• Roof Slopes: 1 in 3, 1 in 4, 1 in 5

Design Basis:

• Structural design per IS 800-1962 (compatible with IS 800-1984)
• Wind pressure per IS 875-1964 (normal permeability ±0.2)
• Portal frame analysis via stiffness method (computer program)
• Includes design of purlins, girts, frame members, base plates, fasteners, and eaves beams
• Bracing and foundation designs are not typified but examples provided

Additional Notes:

• Forces for foundation design consider dead loads plus 30 kg/m² for AC sheeting and girts
• Welded connection details (haunch stiffener weld size, crown stiffener thickness) per section depth (see Table 84)
• Handbook intended for qualified engineers only

Portal Frame Configuration & Loadings (IS SP:40)

1. Portal Frame Configuration (Clause 1.2)

• Portal frames consist of beams and columns designed for max forces from load combinations.
• Columns limited to max slenderness ratio = 250 (due to bending).
• Sections used: ISLB, ISMB, ISWB, ISHB rolled I-sections or built-up sections if required.

2. Effective Length Factors (IS 800-1962, Clause 3.2)

3. Loadings (Clause 2.1)

• Dead Load (excluding columns): 40 to 60 kg/m²
• Live Load: As per IS 875-1964, adjusted for roof slope.
• Wind Load: Basic wind pressures per IS 875-1964 for 3 wind zones.
• Wind cases analyzed:
  • Perpendicular to ridge with internal suction (WLi)
  • Perpendicular to ridge with internal pressure (WL2)
  • Parallel to ridge with internal pressure (WL3)
• Drag forces on multi-bay frames included.
• Earthquake loads per IS 1893-1984 found non-governing.

4. Deflection Limits

• Max sway deflection of columns = H/325
• Max vertical deflection of beams = L/325

5. Unit Weight of Portal Frames (kg/m²) (Excerpt from Table 94)

Key Formulas & Tables for Load Analysis (IS SP:40 Part 40)

1. Load Combination for Portal Frames (Clause 107.51)

• Dead Load + Live Load (D.L + L.L) = 495 kg/m

2. Design Forces Table (Table 90)

• MB, Mc: Moments at base and crown.
• VA, VE: Vertical reactions.
• HA, HE: Horizontal reactions.

3. Load Parameters (Clause 6.0)

• Portal Span: 18 m
• Column Spacing: 6 m
• Column Height: 6 m
• Roof Slope: 1 in 3 (18.435°)
• Wind Pressure: 100 kg/m² (adjust foundation forces proportionally)

4. Foundation Forces (Table 80)

• Forces include dead, live, and wind loads with moments and horizontal forces.
• Add 30 kg/m² for dead load of AC sheeting and girts.

Important Notes:

• Use 0.75 factor on load combinations with wind load for design.
• Deflection is computed at joint D using unit load method under DL + WL2.
• For wind pressures other than 100 kg/m², scale forces proportionally.
• Supports can be hinged or fixed, affecting moment and reaction values.

Design of Frame Members (IS SP:40 & IS 800-1962)

1. Effective Length Factors (IS 800-1962)

• Max slenderness ratio for columns: 250 (due to bending behavior)

2. Deflection Limits

• Max sway deflection (columns): Span/325
• Max vertical deflection (beams): Span/325

3. Design Sections

• Use prismatic rolled I-sections: ISLB, ISMB, ISWB, ISHB.
• If unavailable, use next larger section in series.
• For taller columns (9m, 12m), built-up sections may be necessary.

4. Welded Connection Details (Table 84)

• Stiffeners must fit within section depth and extend to flange edges.

Quick Reference Formula for Column Slenderness:

[ \lambda = \frac{KL}{r} \leq 250 ]

• (K): Effective length factor (from table)
• (L): Actual length of member
• (r): Radius of gyration

flowchart TD
    A[Portal Frame Design] --> B[Determine Loads]
    B --> C[Calculate Forces & Moments]
    C --> D[Select Effective Length Factors]
    D --> E[Check Slenderness Ratio]
    E --> F{Slenderness \leq 250?}

IS SP:40 (S&T)-1987 — Key Connection Details for Steel Portal Frames

1. Welded Connection Details (Table 84)

• Note: Crown stiffener weld size = 5 mm.
• Stiffeners must fit within section depth and extend to flange edge.

2. Bolted Connection Details

Haunch Bolted Connection (Table 85)

• Bolt type: HSFG or high tensile (10k)
• Bolt diameter: 16 - 24 mm depending on section size
• Typical pitch (a) and gauge (b) vary with section depth (see Table 85)
• Refer to Fig. 8 for detailed geometry.

Crown Bolted Connection (Table 86)

• Bolt diameter: 16 - 20 mm
• Bolt pitch (a): 30 - 35 mm
• Bolt gauge (b): 30 - 40 mm
• Refer to Fig. 10 for details.

3. Column Base Details

Fixed Column Base (Table 87)

• Slab base size varies from 500x450 mm to 900x650 mm depending on column size.
• Anchor bolts: 6 nos, diameter 36-56 mm.
• Stiffener thickness: 10-16 mm, height 250 mm.
• Use 8 mm fillet weld for base plate connections.

Hinged Column Base (Table 88)

• Slab base sizes from 350x300 mm to 650x300 mm.
• Anchor bolts: 4 nos, diameter 14-22 mm.
• Plate thickness: 16-20 mm.
• Refer Fig. 11 for base details.

4. Design Notes

• Anchor bolt length calculation: Refer design example in clause 6.8.
• Connection forces should consider dead load + wind load (adjust forces proportionally).
• For detailed fabrication, refer to Figures 5-7 (haunch), 8 (bolted

Key Formulas and Specifications for Foundation Forces and Design (IS SP:40)

1. Foundation Forces from Tables (Typical values for Steel Portal Frames)

• Forces depend on column height (6m, 9m, 12m), number of bays, and foundation location.
• To adjust for wind pressure other than 200 kg/m², scale forces proportionally.
• Add 30 kg/m² to foundation forces for AC sheeting and girts dead load.

2. Allowable Soil Bearing Pressure and Footing Depth

• Allowable bearing pressure, ( q_{allow} = 15,000 , \text{kg/m}^2 )
• Required footing depth below grade = 2.5 m
• Unit weight of soil backfill = 1,500 kg/m³

3. Design Load Combinations

• Check for:
  • ( DL + LL )
  • ( DL + WL )
• Use the governing combination for design (usually ( DL + WL ) governs uplift and moment).

4. Anchor Bolt Design

• Total tension in bolts example: 13,205 kg for 3 bolts.
• Use net area = 0.75 × gross area of bolt (e.g., 36 mm diameter bolt).
• Calculate development length based on bolt tension and base plate design.

Summary of Design Approach

flowchart TD
    A[Determine Loads] --> B[Calculate Foundation Forces]
    B --> C[Select

Deflection Calculations as per IS SP:40 (S&T)-1987

Key points from Clause 34.7 and related tables:

• Load for deflection: Use actual load = 1.333 × Load from Table B.
• Deflection location: Maximum horizontal deflection occurs at joint D.
• Method: Unit load method using moment diagrams (M for actual load, m for unit load).
• Deflection (δ) formula:

[ \delta = \frac{\sum (Area\ of\ M\ diagram \times Ordinate\ of\ m\ diagram\ at\ C.G.\ of\ M)}{EI} ]

Where:

• (E) = Modulus of elasticity
• (I) = Moment of inertia of the member section

Table 91 (Example for Deflection Calculation)

Sum the products (S) for all members to get numerator for deflection.

Important Specifications:

• Deflection limit: Check against permissible deflection as per Clause 3.52.
• Load combinations: Use DL + LL or DL + WL as per Clause 107.51.
• Maximum sway deflection example: (X_I = 0.774 \times 10^5 , cm^4).

Summary:

• Use unit load method with moment diagrams.
• Calculate integral of M × m via area and ordinate products.
• Divide by EI to get deflection.
• Verify deflection against permissible limits.

flowchart LR
    A[Apply Actual Load] --> B[Draw Moment Diagram (M)]
    B --> C[Apply Unit Load at Deflection Point]
    C --> D[Draw Unit Load Moment Diagram (m)]
    D --> E[Calculate Area of M Diagram]
    E --> F[Find Ord

IS SP:40 (S&T)-1987 — Fabrication & Erection Details Summary

1. Welded Connection Details for Portal Frames (Table 84)

• Note: Stiffeners fit within section depth; breadth extends to flange edge.
• Use 5 mm weld for crown stiffeners.

2. Bolted Connection Details

• Haunch Bolted Connection (Table 85) and Crown Bolted Connection (Table 86) specify bolt diameters (mostly 16-20 mm), bolt numbers, and spacing (a, b in mm) depending on section type (ISLB, ISMB, ISWB, ISHB).
• Use HSFG (10k) high tensile bolts.
• Refer to figures 5–10 for detailed connection geometry.

3. Column Base Details

• Fixed Base (Table 87) and Hinged Base (Table 88) specify:
  • Slab base sizes (a × b in mm),
  • Thickness (t),
  • Anchor bolt diameter & quantity,
  • Stiffener thickness and height.
• Typical anchor bolt diameters: 30-56 mm, bolts number: 4-6.
• Use 8 mm fillet welds for base plate connections.
• Anchor bolt length per design example (Clause 6.8).

4. Sag Rod and Purlin Connection

• Sag rods: 10-12 mm dia, placed every 7th-8th panel.
• Max panel size: Roof purlin 1400 mm, wall girts 1700 mm.
• Use ISA sections for struts and sag rods.

5. Foundation Forces & Design

• Foundation forces given for fixed and hinged bases.
• Wind forces for 200 kg/m² basic pressure; scale for 100 or 150 kg/m².

IS SP Part 40: Bracing and Sag Rod Details Summary

1. Sag Rods for Purlins & Girts (Clause 12.7)

• Sag Rod Diameter: Typically 10 mm to 12 mm diameter rods (ISRO rods).
• Purlin Sizes with Sag Rods:

• Girt Sizes:

2. Sag Rod Force Calculation (Clause 123.18)

[ F_{\text{sag rod}} = \frac{5 \times 123.18 \times \sin 18.435^\circ \times 6 \times 8}{8} = 1169 \text{ kg} ]

• Required net area of sag rod:

[ A_{\text{net}} = \frac{1169}{1500} = 0.78 \text{ cm}^2 ]

• Use 12 mm diameter rod (area ≈ 1.13 cm²) for safety.

3. Bracing Design (Clause 6.9)

• Typical bracing types: Type b bracing recommended.
• Wind force perpendicular to ridge is resisted by frame action; nominal bracing needed in gable & side walls.
• Diagonal sag rods placed every 8th panel of purlins and at topmost panel.

Typical Sag Rod Detail (Fig. 4):

graph TD
    Purlin -->|Sag Rod| Frame

Expansion Joints - IS SP:40 (S&T)-1987 Key Points

• When Required: Expansion joints are generally not necessary for building lengths < 180 m. For longer buildings, provide expansion joints by dividing the structure into independent segments with separate super-structural supports.

• Structural Independence: Wind bracings and other structural systems must be discontinuous across the expansion joint, ensuring bracing systems are independent on either side.

• Gap Treatment: The gap at expansion joints should be properly bridged using cladding and roof sheeting to maintain weather tightness.

Summary Table for Expansion Joints

Additional Notes:

• Design expansion joints to accommodate thermal expansion and contraction.
• Typical gap width depends on expected movement; consult detailed design standards or manufacturer's specs.
• Ensure waterproofing and sealing at the joint to prevent leakage.

flowchart LR
    A[Building Length > 180m?] -->|No| B[No Expansion Joint Required]
    A -->|Yes| C[Provide Expansion Joint]
    C --> D[Divide Structure into Independent Segments]
    D --> E[Discontinuous Bracing Systems]
    E --> F[Bridge Gap with Cladding & Roof Sheeting]

For detailed connection and weld sizes at joints, refer to Tables 84-88 in the code for haunch and crown stiffeners, bolted connections, and base details.

Key Formulas, Tables & Specifications from IS SP Part 40 Design Example

Basic Parameters (Clause 6.0)

Wind Load Cases (kg/m²)

• Note: Wind drag at crown points must be considered for multi-bay frames.

Design & Analysis Highlights

• Portal frame analysis uses stiffness method (computer program).
• Structural design per IS 800-1962 (compatible with IS 800-1984).
• Internal pressure per IS 875-1964 for normal permeability (±0.2).
• Design covers purlins, girts, frame members, column base plates, fasteners, and eaves beams.
• Bracing and foundation design examples included but not typified.
• Joint details are illustrative, not exhaustive.
• Economical design conclusions based on spans, spacings, and slopes.

Typical Design Parameters Table (Clause 4.5)

IS SP:40 (S&T)-1987 — Summary and Conclusions Key Points

• Unit Weights of Portal Frames (kg/m²):
  Includes weight of steel frame + purlins (excludes sag rods, base plates, girts).
  Given for various spans (9m to 30m), column heights, number of bays, roof slopes (1:3, 1:4, 1:5), support types (fixed/hinged), spacings (4.5m & 6.0m), and wind pressures (100 & 150 kg/m²).

• Typical Unit Weight Ranges:

  • For 9m span, fixed support, 1 bay, 4.5m column height: ~22 to 34 kg/m² depending on slope and spacing.
  • Hinged frames generally heavier due to less restraint.

• Design Observations:

  • Transverse horizontal deflection limit (1/325) governs member design.
  • Analysis uses stiffness method (computer-based).
  • Design based on IS 800-1962; minor differences expected with IS 800-1984.
  • Internal pressure per IS 875-1964 considered.
  • Joint details shown are illustrative, not exhaustive.
  • Bracing and foundation designs vary; typical examples provided.
  • Detailed design examples included for practical use.

• Economical Design Tips:

  • Lower bays and optimized spacing reduce weight.
  • Fixed supports generally more economical than hinged.
  • Roof slope affects steel quantity moderately.

Representative Table Extract (Unit Weight kg/m² at 100 kg/m² wind pressure, spacing 4.5m):

IS SP:40 (S&T)-1987 Key Specifications & Tables (Bibliography Section)

1. Foundation Forces for Portal Frames (Table 79)

   • Forces given for frame spacings 4.5 m & 6.0 m, column heights 6m, 9m, 12m.
   • Forces include Dead Load, Live Load, Wind Load (p=200 kg/m²).
   • Downward force positive, horizontal force to left positive.
   • To adjust for wind pressures 100 or 150 kg/m², reduce forces proportionately.
   • Add 30 kg/m² to foundation forces for dead load of AC sheeting and girts.

2. Welded Connection Details (Table 84)

   Section Depth (mm)	Haunch Weld Size (mm)	Haunch Stiffener Thickness (mm)	Crown Stiffener Thickness (mm)
   200 - 350	8	16	6 to 8
   400 - 600	6	18	8

   • Stiffeners fit within section depth; breadth extends to flange edge.
   • Use 5 mm weld for crown stiffeners.

3. Bolted Connection Details

   • Haunch Bolted Connection (Table 85) and Crown Bolted Connection (Table 86) specify bolt diameters, spacing (a, b), and bolt types (HSFG 10k).
   • Refer to figures 5-10 for detailed geometry.

4. Column Base Details

   • Fixed Base (Table 87) and Hinged Base (Table 88) specify slab base sizes, anchor bolt diameters, numbers, and stiffener thickness.
   • Anchor bolt length calculated per design example (clause 6.8).
   • Use 8 mm fillet weld for base plate connections.

Important Notes:

• Foundation forces and connection details are based on roof slopes 1:3, 1:4, 1:5 for conservative design.
• Refer to Fig. 1, 5-11 for detailed drawings.
• Adjust forces for actual wind pressures as needed.

flowchart TD
    A[Frame Spacing & Column Height