A bolted bearing joint is a type of connection used in steel structures where the load is transferred primarily through bearing or compression rather than shear. In this joint, the bolts are subjected to compressive forces, and their design is based on bearing capacity rather than shear strength. Here is a step-by-step procedure for creating a bolted bearing joint:
- Design the Joint: Determine the required number of bolts, their size, grade, and spacing based on the applied loads, member dimensions, and design requirements. Consider factors such as the compressive strength of the bolts, load transfer capacity of the joint, and required factor of safety.
- Prepare the Members: Ensure that the surfaces of both members to be joined are clean, free from any rust, paint, or debris that may affect the connection’s integrity. If necessary, clean the surfaces using wire brushes or other suitable methods.
- Align the Members: Position the members so that their bearing surfaces are in direct contact, ensuring proper alignment. Use temporary clamps or fixtures, if needed, to hold the members in place during the assembly.
- Mark Hole Locations: Use a center punch or other marking tool to mark the hole locations on both members. Ensure the hole spacing is uniform and follows the specified bolt pattern. The hole spacing and size depend on factors such as the bolt diameter, load transfer requirements, and connection strength.
- Drill Holes: Use a drill machine and appropriate drill bits to create holes through both members at the marked locations. The hole diameter should match the bolt diameter precisely to allow for a snug fit and optimal load transfer.
- Remove Burrs: After drilling the holes, remove any burrs or sharp edges from the holes using a deburring tool or a suitable method. This ensures that the bolts can be inserted smoothly without interference.
- Insert Bolts: Place the bolts through the holes, ensuring that they pass through both members. The bolts should be long enough to extend beyond the nuts by an appropriate amount to allow for proper engagement and tightening.
- Add Washers and Nuts: On the opposite side of the joint, place washers over the bolt ends, followed by the nuts. Tighten the nuts by hand until they are snug, but do not apply full torque at this stage.
- Torque the Bolts: Using a torque wrench, tighten the nuts in a specific sequence and to the specified torque values. Follow the recommended tightening procedures and torque values provided by the bolt manufacturer or the applicable design standards.
- Verify and Inspect: After torqueing the bolts, visually inspect the joint to ensure that all bolts are properly tightened. Check for any signs of gaps, misalignment, or other potential issues. Perform a thorough inspection to verify the integrity and load-carrying capacity of the bearing joint.
Example of Application: Bolted bearing joints are commonly used in connections between steel girders and column flanges, where the load is transferred through the compression of the bearing surfaces. These connections are often found in steel bridge structures, where the girders are connected to the bridge piers or abutments.
In this application, the bolts in the bearing joint are designed to resist the compressive forces generated due to the weight of the bridge deck and the live loads. The design ensures that the bolted connections can safely transfer the compressive loads without failure.
It is important to note that the above steps provide a general guideline, and the specific procedures may vary depending on the design requirements, bolt specifications, and construction practices. Always refer to the relevant codes, standards, and manufacturer recommendations for the proper installation of bolted bearing joints in steel structures.
