What is bolted lap Joints? Explain in details with step by step procedure with example.
A bolted lap joint is a type of connection used in steel structures where two members overlap, and bolts are inserted through the overlapping portion to create the connection. This joint is commonly used in applications such as flange connections of beams or columns. Here is a step-by-step procedure for creating a bolted lap 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. Refer to structural design codes and standards for appropriate bolt selection.
- Prepare the Members: Ensure that the ends 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 they overlap by the required amount, typically determined by the joint design and specifications. The amount of overlap depends on factors such as the load transfer requirements, bolt spacing, and connection strength.
- 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 in accordance with the specified bolt pattern.
- Drill Holes: Use a drill machine and appropriate drill bits to create holes through both members at the marked locations. The hole diameter should be slightly larger than the bolt diameter to allow for ease of insertion and minor adjustments during the assembly.
- 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 from one side of the joint, ensuring that they pass through both members. If required, use temporary clamps or fixtures to hold the members in place during the bolt insertion process.
- 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.
- Align the Joint: Adjust the position of the members as necessary to ensure proper alignment and fit between the joint surfaces. This step is crucial to achieve a tight and effective connection.
- 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, the joint is secure, and the desired overlap and alignment are maintained. Check for any signs of gaps, misalignment, or other potential issues.
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 lap joints in steel structures.