Truss Analysis and Friction

What is a truss?

A structure composed of straight members connected at their ends to form a rigid framework.

Where are trusses commonly used?

In bridges, roofs, and towers to efficiently carry loads while minimizing material usage.

What are the three types of trusses?

Simple Truss, Compound Truss, Complex Truss.

What is a Simple Truss?

A truss formed using triangular units to ensure stability.

What is a Compound Truss?

A combination of two or more simple trusses.

What is a Complex Truss?

An indeterminate structure requiring advanced analysis.

What are the key assumptions in truss analysis?

Joints are pinned, loads act only at joints, and members experience pure tension or compression.

What is the Method of Joints?

A technique that analyzes forces at each joint using equilibrium equations (ΣFx = 0, ΣFy = 0).

What are the steps for solving a truss using the Method of Joints?

1. Draw the Free Body Diagram, 2. Determine external reactions, 3. Solve for forces joint by joint.

When should the Method of Joints be used?

When solving forces for multiple members systematically.

What is a zero-force member in a truss?

A member that carries no force and can be removed without affecting equilibrium.

What is the first rule for identifying zero-force members?

If only two non-collinear members meet at a joint with no external load, both must be zero-force members.

What is the second rule for identifying zero-force members?

If three members meet at a joint where two are collinear and no external force is applied, the third is a zero-force member.

What is the Method of Sections?

A shortcut for determining forces in specific truss members by making a strategic cut and applying equilibrium equations.

When is the Method of Sections preferable?

When solving for forces in only a few specific truss members instead of the entire structure.

What are the steps for using the Method of Sections?

1. Determine support reactions, 2. Make a strategic cut, 3. Apply equilibrium equations to solve for forces.

What is friction?

A resistive force that opposes relative motion between two surfaces in contact.

What causes friction?

Surface irregularities and intermolecular forces between surfaces.

What are the three types of friction?

Static Friction, Kinetic Friction, Rolling Friction.

What is static friction?

The force that prevents motion between two surfaces until a certain threshold force is applied.

How does static friction compare to kinetic friction?

Static friction is usually greater than kinetic friction.

What is the equation for static friction?

Fs ≤ μs N, where μs is the coefficient of static friction and N is the normal force.

What is kinetic friction?

The force that resists motion once an object is already sliding.

What is the equation for kinetic friction?

Fk = μk N, where μk is the coefficient of kinetic friction and N is the normal force.

Does kinetic friction depend on speed?

No, kinetic friction remains constant regardless of speed.

What is rolling friction?

The resistance force acting against a rolling object, such as a wheel or a ball.

How does rolling friction compare to static and kinetic friction?

Rolling friction is much smaller than both static and kinetic friction.

What is the angle of friction?

The angle at which an object just starts to slide.

What is the equation for the angle of friction?

tan θf = μs, where μs is the coefficient of static friction.