5. SIMPLE TRUSSES, Theory of Structures, CE 4003 (Same as CC 4003)

Rajasthan Polytechnic (BTER) February 28, 2025

🎉 Welcome to the Rajasthan Polytechnic Blog! 🎉


For 4th Semester Polytechnic CE Students
Written by Garima Kanwar | Blog: Rajasthan Polytechnic

📢 🔔 Important Updates:
👉 Full PDFs available in our WhatsApp Group | Telegram Channel
👉 Subscribe to YouTube Channel: BTER Polytechnic Classes 📺

Subject: Theory of Structures (CE 4003 Same as CC 4003)

Branch: Civil Engineering 🏗️
Semester: 4th Semester 📚

📍⚡ Important Links:
👉 WhatsApp Group: Join Now 💬
👉 Telegram Channel: Join Now 📱
📄 Notes in Hindi: Click Here
📄 Notes in English: Click Here
🔥 4th Semester All Subjects Notes: Click Here 📑

💖 Support Our Initiative
If you find these resources helpful, your generous support helps us continue providing valuable study materials to students like you. Every contribution, big or small, makes a difference! 🙏

UPI ID: garimakanwarchauhan@oksbi 💳

Thank you for your kindness and support! Your help truly matters. 🌟💖 

5. SIMPLE TRUSSES ✏️

A truss is a structure made up of straight members (called beams) connected to each other to form a framework. This framework supports loads, especially in buildings, bridges, and roofs. Trusses are lightweight and efficient at distributing weight.

The primary idea behind a truss is that the straight members only carry axial forces (either tension or compression) and not bending forces. This makes the structure strong and cost-effective.

5.1 Types of Trusses 🔧

Different types of trusses are designed based on the span (distance between supports) and the type of load they will carry. Let's explore each type:

5.1.1 Simple Truss 🛠️

A simple truss is the basic form of a truss and typically has a triangular shape. It is made up of several triangular sections that are connected together.

  • Structure: Consists of only straight members forming triangles.
  • Application: Used in small and simple structures, like small bridges or roofs.

Example: A triangular truss used for a small bridge.

5.1.2 Fink Truss 🔺

The Fink truss is used in roof structures and is characterized by a series of triangular sections that distribute the load efficiently. It has diagonal members that help in supporting vertical loads.

  • Structure: It has a vertical post in the center and diagonal members forming triangles.
  • Application: Ideal for residential roofs.

Example: Roof trusses in houses.

5.1.3 Compound Fink Truss 🏠

The compound Fink truss is similar to the regular Fink truss but has additional diagonal members. These extra members help in spreading the load more evenly, making it more efficient for larger structures.

  • Structure: Contains extra diagonal members for better load distribution.
  • Application: Used in larger roofs or structures requiring more strength.

Example: Used in large buildings and warehouses.

5.1.4 French Truss 🇫🇷

The French truss has horizontal and diagonal members to distribute the load efficiently. It is designed for specific uses in architectural structures where appearance and load distribution are both important.

  • Structure: It has multiple diagonal and horizontal members, making it more complex.
  • Application: Used in structures like domes or arches.

5.1.5 Pratt Truss 🔧

The Pratt truss is one of the most commonly used types of trusses. It has diagonal members that slant towards the center of the truss, and vertical members at the center. This design is excellent for carrying heavy vertical loads.

  • Structure: Diagonal members slope towards the center, and vertical members provide support.
  • Application: Often used in bridges and long-span roofs.

Example: Bridges that carry heavy loads like railways.

5.1.6 Howe Truss 🏗️

The Howe truss is the opposite of the Pratt truss. It has diagonal members that slant towards the ends, and vertical members in the middle. This design is more efficient for handling compression forces.

  • Structure: Diagonal members slant towards the ends, with vertical members in the center.
  • Application: Used for larger bridges and structures where compressive forces are high.

Example: Large-span bridges and roof systems.

5.1.7 North Light Truss 🌞

The North Light truss is specifically designed to allow natural light into industrial or commercial buildings. It has a slanted profile that lets sunlight pass through while providing support for the roof.

  • Structure: Features a combination of slanted and horizontal members for stability and light penetration.
  • Application: Industrial buildings, warehouses, and factories.

Example: Large warehouses that need natural lighting from the roof.

5.1.8 King Post and Queen Post Trusses 👑

The King Post and Queen Post trusses are simple and effective designs for medium to large spans.

  • King Post Truss: A single central post (the "king" post) supports the truss.
  • Queen Post Truss: Has two vertical posts (the "queen" posts) for greater support, used for larger spans.

Example: Historically used in bridges and roof structures.

5.2 Calculate Support Reactions for Trusses Subjected to Point Loads at Joints ⚖️

When a truss is subjected to point loads at its joints, we need to calculate the support reactions at the points where the truss is supported. These reactions help in determining how much force each support is taking.

Steps to calculate support reactions:

  1. Identify the Loads: Point loads are applied at various joints of the truss.
  2. Use Equilibrium Equations: The truss is in static equilibrium, so:
    • ∑Fx=0\sum F_x = 0 (Horizontal forces must balance).
    • ∑Fy=0\sum F_y = 0 (Vertical forces must balance).
    • ∑M=0\sum M = 0 (Sum of moments about any point must be zero).
    These equations help you find the unknown reaction forces at the supports.

Example: For a truss with two supports (A and B) and point loads applied at joints C and D:

  • You would first sum up the vertical and horizontal forces at each support.
  • Then, use the moment equation to calculate the reactions at supports A and B.

5.3 Calculate Forces in Members of Truss Using the Method of Joints 🔍

The Method of Joints is a technique used to find the forces in each member of a truss. By using equilibrium equations for each joint, we can solve for the forces.

Steps for the Method of Joints:

  1. Start at a Joint with Known Reactions: Begin at a joint where only two unknown forces exist. This makes calculations easier.

  2. Apply Equilibrium Equations: For each joint, apply the equilibrium equations:

    • Sum of horizontal forces = 0 (∑Fx=0\sum F_x = 0).
    • Sum of vertical forces = 0 (∑Fy=0\sum F_y = 0).

  3. Solve for Unknown Forces: Use these equations to solve for the unknown forces in the members connected to the joint.

  4. Move to the Next Joint: After solving for the forces at one joint, move to another joint and repeat the process until all member forces are determined.

Example: Let’s say we have a simple truss with supports at two ends (A and B), and a point load is applied at joint C.

  • Calculate the reactions at A and B using equilibrium equations.
  • Begin with joint C (if it has only two unknowns) and solve for the forces in the members connected to it.
  • Repeat for other joints until all forces in the truss members are found.

Summary of Key Points 📚

  • Types of Trusses: Trusses come in many shapes and sizes, from simple triangular trusses to more complex ones like Pratt and Howe trusses. Each type is designed to carry loads in specific ways, depending on the span and the forces involved.

  • Support Reactions: These are calculated using equilibrium equations. Reactions at supports help us understand how much force is acting at each support point.

  • Method of Joints: A systematic method to calculate forces in truss members by applying equilibrium conditions at each joint. It is easy to apply when the number of unknowns is low at each joint.

By mastering these methods, you’ll be able to analyze and design various types of trusses used in real-world applications, from simple bridges to complex roof structures!

📢 🔔 Download PDFs & Join Study Groups:
📥 WhatsApp Group: Join Now
📥 Telegram Channel: Join Now
📺 Watch Lectures on YouTube: BTER Polytechnic Classes
📍 Stay connected for more study materials and updates! 🚀

💖 Support Our Initiative
Your support means the world to us! If you find our resources helpful and wish to contribute, your generous donations will enable us to continue providing quality study materials and resources for students like you. Every contribution, big or small, helps us reach more students and improve the content we offer.

Let’s build a brighter future together! 🙏

UPI ID: garimakanwarchauhan@oksbi
QR Code: 

Thank you for your kindness and support! Your help truly makes a difference. 💖

Rajasthan Polytechnic (BTER)

Posted by Rajasthan Polytechnic (BTER)

Hi! I’m Garima Kanwar, founder of Rajasthan Polytechnic (BTER). This platform provides notes, PDFs, and video lectures for all Polytechnic branches (ME, CS, EE) and semesters to make learning easy .I ensure exam-focused, updated, and simple-to-understand content, along with academic updates and career guidance.

Post a Comment

0 Comments