Code of practice for design and construction of machine foundations, Part 1: Foundation for reciprocating type machines

IS 2974 Part 1 (1982) - Scope & Key Specifications

Scope Summary:

• Applies to foundations for reciprocating and rotary machines.
• Defines notations (Appendix A) for vibration analysis and foundation design.
• Specifies data needed for design and testing.

Key Notations (Appendix A):

Necessary Data for Design (Clause 4.1.1):

• Machine description & type
• Operating speed(s)
• Cylinder count & arrangement
• Distance from main shaft axis to foundation top
• Max rated output
• Gearbox ratio (if any)
• Max operating temperature at machine base

Important Notes:

• Round off results per IS 2-1960.
• Use these parameters for vibration analysis, resonance frequency calculation, and foundation stiffness design.

flowchart LR
    A[Machine Data] --> B[Foundation Design]
    B --> C[Calculate Natural Frequencies (fn, fn1, fn2)]
    B --> D[Vibration Amplitudes (Ax, Az, Ap)]
    B --> E[Soil Parameters (

IS 2974 Part 1 – Definitions & Notations Summary

Key Definitions (Clause 2.0)

• Centroid of Bearing Surface (C): Center of foundation-soil contact area.
• Combined Centroid (0): Centroid of foundation + machinery system.
• Axes: Lateral, Longitudinal, Pitching, Rocking (see Fig.1 in code).

Important Notations (Appendix A, Clause 3.1)

Essential Data to Collect (Clause 4.1.1)

• Machine type, speed, cylinder arrangement
• Shaft axis to foundation top distance
• Max output, gear ratio, operating temperature

Conceptual Diagram of Foundation Vibrations

flowchart LR
    A[Machine + Foundation System]
    B[Contact Area with Soil (A)]
    C[Forces P, Moments M]
    D[Vibrations: Horizontal (Aₓ), Vertical (A_z), Rotational (A_p)]
   

IS 2974 Part 1 - Key Notations Summary

Important Formula (Limiting Natural Frequencies) - Appendix B

[ f_a = \frac{C_I}{4 \pi^2 M_{mo}} \quad,\quad f_i = \frac{C_T}{4

IS 2974 Part 1: Necessary Data Summary

1. Soil and Site Data (Clause 4.2)

• Soil profile & characteristics: Up to a depth ≥ 3 × (mean plan dimension of foundation) or up to hard strata.
• Soil investigation: Per IS 1892-1979 for geotechnical data; IS 5249-1977 for dynamic soil properties.
• Water table: Relative position below ground at various times of the year.

2. Machine Data (Clause 4.1)

Manufacturer must provide:

• Description of driving/driven machinery.
• Operating speeds or speed ranges.
• Number & arrangement of cylinders.
• Distance from main shaft axis to foundation top.
• Maximum rated output (power).
• Gearbox ratio (if applicable).
• Maximum operating temperature at machine bases.

Key Formula for Foundation Depth (from 4.2a):

[ \text{Depth of soil investigation} \geq 3 \times \sqrt{\text{Foundation area}} ]

Notations

Refer Appendix A of IS 2974 Part 1 for all symbols and units.

flowchart TD
    A[Machine Data] --> B[Foundation Design]
    C[Soil Profile & Properties] --> B
    D[Water Table Position] --> B
    B --> E[Safe & Stable Foundation]

This ensures foundation design accommodates machine dynamics and soil conditions per IS 2974 Part 1.

IS 2974 Part 1 — Design Criteria Summary

1. Soil Data Requirements (Clause 4.2)

• Soil profile depth: At least 3× the mean plan dimension of the foundation (mean dimension ≈ √(foundation area)).
• Soil investigation: Per IS 1892-1979 for static properties; IS 5249-1977 for dynamic soil properties.
• Water table position: Relative depth below ground at various times.

2. Design Criteria (Clause 5 & 4.1.2, 4.1.3)

• Static Design: Use soil parameters from static soil tests (bearing capacity, settlement).
• Dynamic Design: Consider dynamic soil properties (shear modulus, damping) for seismic or vibration loads.

3. Key Formulas

• Mean plan dimension, ( D_m ): [ D_m = \sqrt{\text{Foundation Area}} ]

• Depth of soil profile for investigation: [ H = 3 \times D_m ]

• Bearing capacity (general form): [ q_{ult} = cN_c + \gamma D_f N_q + 0.5 \gamma B N_\gamma ] where:

  • ( c ) = cohesion,
  • ( \gamma ) = unit weight,
  • ( D_f ) = foundation depth,
  • ( B ) = foundation width,
  • ( N_c, N_q, N_\gamma ) = bearing capacity factors.

4. Reference Tables

• Use IS 1892 and IS 5249 for soil parameters and dynamic properties.
• Appendix A of IS 2974 Part 1 defines notation for parameters.

flowchart TD
    A[Start: Foundation Design] --> B[Determine foundation area]
    B --> C[Calculate mean dimension \(D_m = \sqrt{Area}\)]
    C --> D[Soil investigation depth \(H = 3 \times D_m\)]
    D --> E[Collect static & dynamic soil data]
    E --> F[Apply static design criteria]
    E --> G[Apply dynamic design criteria]
    F & G --> H[Design foundation accordingly]

Note: Always cross-check soil data

IS 2974 Part 1: Materials and Construction - Key Points

1. Soil Data (Clause 4.2)

• Soil profile depth: At least 3× the expected foundation dimension (√area) or up to hard strata.
• Soil investigation: As per IS 1892-1979 for soil characteristics and IS 5249-1977 for dynamic soil properties.
• Water table: Record relative position throughout the year.

2. Concrete Specifications (Clause 6.1)

• Concrete grade: Minimum M15 as per IS 456-1978.
• Strength basis: 28-day cube compressive strength.

3. Design Data (Clause 5.4)

• Foundation design must consider soil data and concrete grade.
• Use notations from Appendix A (IS 2974 Part 1).

Typical Concrete Grades (IS 456:2000 update reference)

Summary Diagram: Foundation Design Inputs

flowchart TD
    A[Site Investigation] --> B[Soil Profile & Properties]
    B --> C[Water Table Data]
    C --> D[Foundation Design]
    E[Concrete Grade (≥ M15)] --> D
    D --> F[Structural Safety & Serviceability]

Note: Always refer to IS 2974 Part 1 for detailed design procedures and IS 456 for concrete mix design.

IS 2974 Part 1 - Measurement & Testing: Key Formulas and Specifications

1. Measurement Rounding (Clause 0.3)

• Final test values must be rounded per IS 2-1960.
• Retain the same number of significant digits as the specified value.

2. Important Notations (Appendix A, Clause 3.1)

3. Fundamental Relations

• Natural Frequency (horizontal/vertical):
  [ f_n = \frac{1}{2\pi} \sqrt{\frac{k}{m}} ]

• Circular Natural Frequency:
  [ \omega_n = 2 \pi f_n = \sqrt{\frac{k}{m}} ]

• Amplitude under force (P_0):
  [ A = \frac{P_0}{k} ]

• Moment of inertia (I):
  Depends on foundation geometry; used for rotational vibration analysis.

4. Testing & Measurement Guidelines

• Measure amplitudes (Aₓ, A_z, A_p) under applied forces/moments.
• Determine damping constants (C, C_c) via dynamic testing.
• Calculate natural frequencies (fₙ, f_r) to check resonance conditions.

IS 2974 Part 1 — Foundation Block Design Key Points

1. Dimensions of Concrete Foundation Blocks (Clause 5.4.2)

• Initial sizing based on empirical rules:
  • Length (L) ≥ 2 × width (B)
  • Thickness (D) depends on bearing capacity and load but must ensure stability.
• Proportions should prevent overturning and sliding (Clause 5.4.2.4).

2. Minimum Reinforcement (Clause 5.4.5)

• Provide minimum steel to control cracking and ensure ductility.
• Typical minimum reinforcement ratio:
  [ \rho_{min} = 0.15% \text{ to } 0.3% \text{ of cross-sectional area} ]
• Use mild steel or HYSD bars as per IS 456.

3. Design Considerations (Clause 5.4)

• Design for combined axial load and bending moment.
• Check for:
  • Bearing pressure ≤ soil allowable bearing capacity
  • Factor of safety against sliding and overturning ≥ 1.5
  • Adequate anchorage length for reinforcement bars.

Typical Formula for Bearing Pressure:

[ q = \frac{P}{A} \leq q_{allow} ]

Where:

• (P) = total load on foundation
• (A = L \times B) = area of foundation base
• (q_{allow}) = allowable soil bearing pressure

Summary Table:

flowchart TD
    A[Load on Structure] --> B[Foundation Block]
    B --> C{Check Bearing Pressure}
    C -->|q ≤ q_allow| D[OK]
    C -->|q > q_allow| E[Increase Block Size]
    B --> F{Check Stability}
    F -->|FS ≥ 1.5|

Key Specifications & Formulas for Piled Foundations (IS 2974 Part 1)

1. Soil Data Requirements (Clause 4.2):

• Soil profile depth ≥ 3 × foundation mean plan dimension (√area) or to hard strata.
• Soil investigation per IS 1892-1979 and dynamic soil properties per IS 5249-1977.
• Water table position at various times of the year.

2. Reasons for Using Piled Foundations (Clause 5.4.4.1):

• When soil bearing pressure exceeds permissible limits.
• To avoid resonance in foundations due to dynamic loads.
• To control vibration amplitudes and differential settlements beyond permissible limits.
• To minimize ground-borne vibrations affecting nearby structures/equipment.

3. Design Criteria (Clause 5.4.4):

• Use end-bearing or friction piles to alter foundation vibration frequencies or support heavy dead loads.
• Minimum pile cap thickness: 60 cm.
• Pile caps must satisfy all design criteria (load transfer, stability).

Typical Pile Bearing Capacity Formula (General Engineering Knowledge):

[ Q_u = Q_p + Q_s ]

Where:

• (Q_u) = Ultimate pile capacity
• (Q_p = A_p \times q_p) (End bearing capacity; (A_p) = pile tip area, (q_p) = bearing pressure at tip)
• (Q_s = \sum (P \times L)) (Skin friction along pile shaft; (P) = unit skin friction, (L) = length segments)

Pile Cap Thickness Recommendation:

flowchart TD
    A[Soil Investigation] --> B[Determine Soil Profile & Properties]
    B --> C{Bearing Pressure > Permissible?}
    C -- Yes --> D[Use Piled Foundation]
    C -- No --> E[Use Shallow/Foundation Block]
    D --> F[Design Pile Cap ≥ 60 cm thick]
    F --> G[Check Vibration & Settlement Criteria]

For detailed design, refer to IS 2974 Part 1 clauses and IS 2911 for pile design methods.

IS 2974 Part 1: Vibration Control & Anti-Vibration Mountings

Key Specifications:

• Anti-vibration mountings used:

  • Between machinery & foundation
  • Between foundation block & supporting system
    (Clause 5.4.6.2)

• Type & position of mountings must be indicated (Clause 4.1.3.4).

Important Notations (Appendix A, Clause 3.1):

Fundamental Formulas:

• Natural frequency (circular):
  [ w_n = \sqrt{\frac{k}{m}} ]

• Horizontal amplitude under force (P) and moment (M):
  [ A. = \frac{P}{k} \quad \text{(simplified)} ]

• Damping effect:
  Damping constant (C) affects vibration amplitude and resonance.

Vibration Control Design Principles:

• Select mountings to reduce transmission of vibrations to soil/foundation.
• Ensure mountings accommodate:
  • Vertical and horizontal vibrations
  • Rotational vibrations (moment effects)
• Consider soil stiffness coefficients (Cu, CT, Co) for foundation-soil interaction.

IS 2974 Part 1: Reinforcement Requirements for Block Foundations

Key Specifications (Clause 5.4.5):

• Minimum Reinforcement Quantity:

  • Normal foundations: ≥ 25 kg/m³
  • Special foundations (e.g., machines pumping explosive gases): ≥ 40 kg/m³

• Bar Size & Spacing (Clause 5.4.5.2):

  • Use 12 mm diameter bars
  • Spacing: 200 to 250 mm c/c
  • Bars placed both vertically and horizontally near all faces

• Reinforcement Arrangement (Clause 5.4.5.3):

  • Ends of mild steel bars must be hooked
  • Reinforcement at all faces
  • For block height > 1 m, provide shrinkage reinforcement in all three directions
  • Around pits/openings: reinforcement area = 0.50% to 0.75% of cross-sectional area

Summary Table:

Hooked Bar Ends Illustration:

graph LR
A[Bar End] --> B(Hook)
B --> C[Anchorage in Concrete]

This ensures adequate crack control, durability, and load transfer in block foundations per IS 2974 Part 1.

IS 2974 Part 1: Dynamic Analysis & Natural Frequencies

Key Formulas (Appendix B, Clause 5.4.3)

• Limiting Natural Frequencies:

[ f_a = \frac{C_I - W L}{4 \pi^2 M_{mo}}, \quad f_i = \frac{C_T A}{4 \pi^2 m} ]

where:

• (C_I, C_T) = soil elastic coefficients (compression, shear)

• (W) = weight of foundation + machine (kg)

• (L) = eccentricity (cm)

• (M_{mo}) = mass moment of inertia (kg-cm-s²)

• (A) = contact area (cm²)

• (m) = mass (kg-s²/cm)

• Natural Frequency Calculation (when CG and centroid aligned):

[ f_n = \sqrt{\frac{k}{m}} ]

• Amplitude of vibration:

[ A = \frac{P}{\sqrt{(k - m \omega^2)^2 + (C \omega)^2}} ]

where:

• (P) = oscillating force (kg)
• (k) = stiffness (kg/cm)
• (m) = mass (kg-s²/cm)
• (C) = damping constant (dimensionless)
• (\omega) = circular frequency (rad/s)

Important Parameters (Appendix A Notations)

Design Considerations (Clause 5.4.3)

• Use vibration calculations to finalize foundation dimensions.
• Check bearing pressure.
• Calculate

IS 2974 Part 1 – Installation and Grouting Key Points

1. Grout Composition (Clause 6.3.1)

• Cement grout mix:
  • 1 part Portland cement
  • 2 parts clean sharp sand
• Consistency: Moist, workable to fully fill all seatings
• Note: Quick setting cement not allowed

2. Formwork for Grouting (Clause 6.4.3 & 6.4.4)

• Height of forms: Minimum 150 mm head of grout on all sides from pouring side
• Clearance: Sufficient gap between forms and base edges for grout flow
• Strength: Forms must be strong, secure, and leak-proof
• Pouring:
  • Pour grout from one side only
  • Continuous, uninterrupted pouring to avoid air pockets
  • Ensure dense, full filling under base

Summary Table

flowchart LR
    A[Prepare Formwork] --> B[Ensure 150 mm head height]
    B --> C[Mix Grout (1:2 Cement:Sand)]
    C --> D[Pour grout from one side continuously]
    D --> E[Grout fills under base without air pockets]

This ensures proper embedding and seating of foundations as per IS 2974 Part 1.

IS 2974 Part 1: Appendices Key Data & Formulas

Appendix A: Notations (Clause 3.1)

Appendix B: Natural Frequencies (Clause 5.4.3)

• Limiting Natural Frequencies:

[ f_a = \frac{1}{2\pi} \sqrt{\frac{C_u}{m}} \quad , \quad f_i = \frac{1}{2\pi} \sqrt{\frac{C_T}{m}} ]

Where:

• ( C_u, C_T ) = soil elastic coefficients
• ( m ) = mass of system

Design Data (Clause 4.1.1