### What is the design criteria of bolted Slip-Critical Joints? Explain in details step by step procedure of a design of bolted Slip-Critical Joints with required formula and an example.

Designing a bolted slip-critical joint involves ensuring that the joint can resist slipping or relative movement between the connected members. Slip-critical joints are commonly used in structures where the prevention of slippage is critical, such as in steel structures subjected to lateral loads. Here is a step-by-step procedure for designing a bolted slip-critical joint:

- Determine the Loads: Identify the applied loads that the joint needs to resist, such as shear, tension, or combined forces. Consider both static and dynamic loads and determine the design loads based on applicable design codes and standards.
- Material Selection: Select appropriate materials for the members being joined, considering factors such as yield strength, shear strength, and thickness. Ensure that the materials being joined have compatible mechanical properties.
- Calculate Design Forces: Determine the design forces acting on the joint based on the applied loads. This may involve analyzing the structural system and considering factors such as load distribution and load combinations.
- Select Bolt Type: Choose the appropriate bolt type for the joint based on the design requirements. Common bolt types for slip-critical joints include high-strength bolts or friction-grip bolts. Consider factors such as shear capacities, corrosion resistance, and other applicable criteria.
- Calculate Bolt Shear Capacity: Determine the required shear capacity of each bolt based on the design forces. Calculate the shear capacity of an individual bolt using the formula:Shear Capacity = Bolt Area * Bolt Shear StrengthThe bolt shear strength can be obtained from bolt manufacturer specifications or design codes.
- Determine Bolt Size: Select an appropriate bolt size that satisfies the required shear capacity. Consider the limitations imposed by the available bolt sizes and the practicality of fabrication and installation.
- Determine Bolt Spacing: Calculate the required bolt spacing based on the design forces and the desired level of performance. The bolt spacing should be sufficient to distribute the applied loads evenly and avoid excessive deformation or stress concentrations. Consider factors such as edge distance, end distance, and any specific requirements specified in the design codes.
- Determine Bolt Layout and Number of Bolts: Determine the layout of the bolts along the joint and calculate the required number of bolts. The bolt layout should consider the load distribution, symmetry, and practical aspects of fabrication and installation.
- Check Bolt Preload: Calculate the required bolt preload to ensure proper clamping force. Bolt preload is typically determined based on the desired level of stiffness, the anticipated external loads, and the requirements specified in the design codes.
- Design Details: Determine the specific design details of the joint, such as the use of washers, nut type, and any additional reinforcement or stiffeners required. Consider practicality, constructability, and maintenance requirements.
- Quality Control: Implement quality control measures during fabrication and installation to ensure the integrity of the joint. This may involve visual inspection, torque verification, and dimensional checks.
- Design Verification: Perform structural analysis or calculations to verify the strength and performance of the bolted slip-critical joint. This may include checks for bolt shear capacities, bolt spacing, and joint deflections.

Example: Design of a Bolted Slip-Critical Joint

Given:

- Applied shear load: 120 kN
- Yield strength of the members: 300 MPa
- Bolt shear strength: 400 MPa

Step 1: Determine the Loads The applied shear load is 120 kN.

Step 2: Material Selection Select appropriate materials based on the yield strength requirement.

Step 3: Calculate Design Forces Design force is 120 kN.

Step 4: Select Bolt Type Choose a bolt type suitable for slip-critical applications.

Step 5: Calculate Bolt Shear Capacity Calculate the required shear capacity of each bolt: Shear Capacity = Bolt Area * Bolt Shear Strength

Step 6: Determine Bolt Size Select an appropriate bolt size that satisfies the required shear capacity.

Step 7: Determine Bolt Spacing Calculate the required bolt spacing based on design requirements.

Step 8: Determine Bolt Layout and Number of Bolts Determine the layout and calculate the number of bolts needed for the joint.

Step 9: Check Bolt Preload Calculate the required bolt preload to ensure proper clamping force.

Step 10: Design Details Specify the details of washers, nut type, and any additional reinforcement if required.

Step 11: Quality Control Implement quality control measures during fabrication and installation.

Step 12: Design Verification Perform structural analysis or calculations to verify the strength and performance of the bolted slip-critical joint.

It is important to note that the specific formulas and procedures for designing bolted slip-critical joints may vary depending on the design codes and standards being used. It is recommended to consult the relevant design code or consult with a qualified structural engineer to ensure accurate and compliant joint design.