Design of unreinforced Elastomeric bearings-Lec02: Design of Bridges #CIVIL

Introduction

This tutorial provides a step-by-step guide on the design of unreinforced elastomeric bearings, as discussed in the video by CIVIL Enlightener. Elastomeric bearings are crucial components in bridge construction, allowing for flexibility and movement while supporting loads. Understanding their design is essential for civil engineers involved in bridge projects.

Step 1: Understand the Purpose of Elastomeric Bearings

• Functionality: Elastomeric bearings are designed to accommodate movements due to temperature changes, vibrations, and settlement.
• Advantages: They offer resistance to shear and are lightweight compared to traditional bearings, making them suitable for various bridge designs.

Step 2: Determine Material Properties

• Elastomer Selection: Choose suitable elastomer materials (e.g., natural rubber) based on properties like:
  • Shore hardness
  • Tensile strength
  • Compression set
• Testing Standards: Refer to relevant ASTM and AASHTO standards for material testing to ensure compliance with safety and performance criteria.

Step 3: Calculate Bearing Dimensions

• Load Analysis: Assess the maximum vertical load the bearing will support.
• Dimensioning: Use the formula: [ Area = \frac{Total Load}{Bearing Pressure} ]
  • Ensure the bearing area is adequate to distribute loads effectively.
• Thickness Selection: Choose a thickness that allows for desired flexibility without compromising strength.

Step 4: Design for Movement and Rotation

• Movement Types: Consider both horizontal and vertical movements in the design.
• Rotation Allowance: Design bearings to accommodate rotational movements, ensuring that the elastomer can deform without failure.

Step 5: Prepare for Installation

• Site Conditions: Assess site conditions that may impact bearing performance, such as soil type and moisture levels.
• Installation Method: Plan for proper installation procedures to prevent damage during setting, including:
  • Using lifting equipment
  • Ensuring level surfaces

Step 6: Conduct Quality Control Checks

• Inspection: Before installation, inspect bearings for defects or inconsistencies.
• Testing: Conduct load tests to validate the bearing's performance under simulated conditions.

Conclusion

The design of unreinforced elastomeric bearings is a critical aspect of bridge engineering. By understanding their purpose, selecting appropriate materials, calculating dimensions, and ensuring proper installation, engineers can ensure the longevity and safety of bridge structures. For further learning, consider exploring more advanced topics in bridge design or specialized elastomer properties.