What is Pinned Joint. Explain in details different types of Pinned Joint used in steel structure construction.

In structural engineering, a pinned joint, also known as a hinged joint or a simply supported joint, is a type of connection that allows for rotation between two or more structural members. It provides a moment-free or nearly moment-free connection, allowing the connected members to rotate around a common axis or point. Pinned joints are commonly used in steel structure construction, particularly in frameworks and trusses, where the ability to accommodate rotation and distribute forces is important.

Here are some of the commonly used types of pinned joints in steel structure construction:

1. Pinned Connection: A pinned connection consists of a pin or a bolt that allows for rotational movement between two connected structural members. The pin is typically inserted through holes drilled in the members and secured with nuts or cotter pins. Pinned connections are commonly used in trusses, where the members experience predominantly axial forces.
2. Gusset Plate Connection: A gusset plate connection involves using a plate to connect multiple members at a joint. The plate is typically bolted or welded to the members, allowing for rotation. Gusset plates are commonly used in truss systems, where they provide stability and transfer forces between members.
3. Pinned Base Connection: A pinned base connection is used to connect a steel column to its foundation. The column is typically embedded in the foundation and supported by a base plate. The connection between the column and the base plate is designed to allow for rotation and prevent the transmission of moments. Pinned base connections are commonly used in steel structures subjected to vertical loads, such as buildings and towers.
4. Pin-Ended Connection: A pin-ended connection, also known as a simple span connection, involves connecting two beams or truss members end-to-end using pins or bolts. The connection allows for rotation at the joint, enabling the members to act independently under loading conditions. Pin-ended connections are commonly used in simple-span beams and trusses.
5. Pinned Flange Connection: A pinned flange connection is used to connect the flange of one beam or girder to the web of another beam or girder. The connection allows for rotation and redistributes the bending moment between the connected members. Pinned flange connections are commonly used in steel structures, such as bridge girders and crane girders.

Pinned joints are designed to primarily resist axial forces while allowing for rotational movement. They are advantageous because they simplify the structural analysis and design, as they eliminate the need to consider moments at the joint. Pinned joints also accommodate thermal expansion and contraction, as well as provide flexibility in response to external loads and displacements.

However, it’s important to note that pinned joints may require additional bracing or lateral stability measures to prevent buckling or excessive deflection. The selection and design of pinned joints depend on factors such as the type of structure, applied loads, and design codes and standards.

Consulting a qualified structural engineer and referring to relevant design guidelines is essential for ensuring the appropriate selection and design of pinned joints in steel structures.