What is Partially Restrained (PR) Connection? Explain in details step by step procedure to make a Partially Restrained (PR) Connection with example and application.
A partially restrained (PR) connection is a type of structural connection used in steel construction that exhibits a limited degree of rotational stiffness. It is designed to allow some rotational movement, while providing partial resistance to bending moments. PR connections are commonly used in steel frames to control the distribution of forces and ensure the overall stability of the structure.
Here is a step-by-step procedure for making a partially restrained (PR) connection:
- Design and Preparation:
- Determine the required level of rotational stiffness and bending moment resistance for the connection based on the structural requirements.
- Select the appropriate connection components such as bolts, plates, and welds based on the design specifications, considering factors such as material strength, size, and corrosion resistance.
- Ensure that the beam and column surfaces are clean, smooth, and free from any debris, rust, or paint.
- Alignment and Positioning:
- Position the beam and column in their designated locations, ensuring proper alignment and fit.
- Use temporary clamps or tack welds to hold the beam and column in place, preventing movement during the connection process.
- Marking and Drilling:
- Mark the positions for the bolt holes on the beam and column, following the specified spacing and pattern.
- Use a drill press or portable drilling machine to drill holes through the marked positions on both the beam and column. Ensure that the holes are aligned and perpendicular to the surface.
- Deburring and Cleaning:
- Remove any burrs or sharp edges around the drilled holes using a deburring tool or file.
- Clean the holes and surfaces of the beam and column to remove any debris, oil, or grease that may affect the connection’s integrity.
- Attaching the Connection Components:
- Position the connection plates or angles on the beam and column, aligning the bolt holes with the drilled holes.
- Insert bolts through the holes, ensuring a proper fit.
- Place washers and nuts onto the exposed ends of the bolts.
- Tightening the Bolts:
- Begin tightening the bolts using an appropriate wrench or torque wrench.
- Tighten the bolts gradually and evenly, following the recommended torque specifications provided by the bolt manufacturer or the design engineer.
- Welding (Optional):
- In some cases, additional welding may be required to enhance the connection’s strength and rigidity.
- Welds may be applied between the connection plates or angles and the beam, as well as between the connection plates or angles and the column.
- The welding process should be carried out by qualified welders, following the applicable welding codes and standards.
- Final Inspection:
- Inspect the connection to ensure that the components are securely attached to the beam and column, and the bolts and nuts are properly seated and tightened.
- Check for any gaps, misalignment, or visible signs of damage or distortion.
- Verify that the connection exhibits the desired level of rotational stiffness and provides the required partial resistance to bending moments.
Example and Application: An example of a partially restrained (PR) connection is the connection between a steel beam and a steel column in a building frame. The connection allows some rotational movement while providing partial resistance to bending moments.
Applications of partially restrained (PR) connections include:
- Multi-story buildings, where PR connections are commonly used to connect beams and columns, allowing controlled rotational movement and redistributing forces to ensure structural stability.
- Industrial facilities, warehouses, and manufacturing plants, where PR connections are employed to resist dynamic loads and accommodate movements caused by equipment or machinery.
- Bridge structures, where PR connections are utilized to handle varying loads and deformations due to temperature changes and traffic conditions.
Partially restrained (PR) connections provide a balance between flexibility and rigidity, allowing controlled movement and redistributing