A friction grip connection, also known as a slip-critical connection, is a type of structural connection that relies on friction between the mating surfaces of steel components to transfer loads. It is commonly used in steel structures where the connection must resist shear, tensile, and compressive forces without relying on bolt preload. Friction grip connections are typically achieved by using high-strength bolts or high-strength friction-grip bolts.
Here is a step-by-step procedure for making a friction grip connection:
- Design and Preparation:
- Determine the required strength and load-bearing capacity for the connection based on the structural requirements.
- Select the appropriate high-strength bolts, nuts, washers, and other connection components based on the design specifications, considering factors such as material strength, size, and corrosion resistance.
- Ensure that the surfaces of the steel components to be connected are clean, smooth, and free from any debris, rust, or paint.
- Alignment and Positioning:
- Position the steel components, such as beams, columns, or plates, in their designated locations, ensuring proper alignment and fit.
- Use temporary clamps or tack welds to hold the components in place, preventing movement during the connection process.
- Marking and Drilling:
- Mark the positions for the bolt holes on the steel components, following the specified spacing and pattern.
- Use a drill press or portable drilling machine to drill holes through the marked positions on the components. 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 components to remove any debris, oil, or grease that may affect the connection’s integrity.
- Inserting Bolts:
- Insert high-strength bolts through the holes in one of the components.
- Place washers and nuts onto the exposed ends of the bolts.
- Tightening the Nuts:
- Begin tightening the nuts using an appropriate wrench or torque wrench.
- Tighten the nuts gradually and evenly, following the specified torque requirements.
- The goal is to achieve sufficient bolt preload to ensure the clamping force necessary for a slip-critical connection.
- Checking for Slippage:
- Apply a specified load or perform a test to check for slippage between the connected components.
- If slippage occurs, tighten the nuts further until the required friction force is achieved.
- Final Inspection:
- Inspect the connection to ensure that the bolts, nuts, and washers are properly seated and tightened.
- Check for any gaps, misalignment, or visible signs of damage or distortion.
- Verify that the connection provides the required friction grip and can resist the specified loads.
Example and Application: An example of a friction grip connection is the connection between steel plates in a bridge or building structure. Friction grip connections are commonly used in applications where it is essential to transfer loads without relying on bolt preload, such as in seismic-resistant structures or structures subject to significant vibrations or dynamic loads.
Applications of friction grip connections include:
- Bridges, where friction grip connections are used to connect steel girders, trusses, and other bridge elements. They provide resistance to shear, tensile, and compressive forces while allowing for thermal expansion and contraction.
- Industrial structures, such as power plants, offshore platforms, or manufacturing facilities, where friction grip connections are employed to connect steel components subject to dynamic loads, vibrations, or movements caused by operational machinery or equipment.
Friction grip connections offer advantages such as simplicity of installation, adjustability during construction, and the ability to disassemble and reassemble if needed. They provide reliable and durable connections that can accommodate thermal expansion, vibration, and dynamic loading conditions.
