Bolted Joints Analyses according to different Steel Codes

Bolted joints are commonly used to connect two or more components together in mechanical engineering applications. Bolted joints have proven to be effective and safe connections, with various design modification options ensuring best fit for general structure stability. There are several types of bolted joints, including:

• Lap Joint: A lap joint is created when two overlapping plates are bolted together. This type of joint is commonly used in sheet metal work.
• Butt Joint: A butt joint is created when two plates are placed end-to-end and bolted together. This type of joint is commonly used in structural applications.
• T-Joint: A T-joint is created when one plate is placed perpendicularly to another plate and bolted together. This type of joint is commonly used in structural applications.
• Corner Joint: A corner joint is created when two plates are placed at right angles to each other and bolted together. This type of joint is commonly used in structural applications.
• Edge Joint: An edge joint is created when two plates are placed edge-to-edge and bolted together. This type of joint is commonly used in sheet metal work.
• Flange Joint: A flange joint is created when two flanges are bolted together. This type of joint is commonly used in piping and other industrial applications.

Analyzing the performance of a bolted joint involves the preload applied to the bolts, the bolt material, the dimensions of the bolt and the materials being joined, and the loads applied to the joint during operation.

Some standard analyses performed on bolted joints include preload, stress, fatigue, finite element (FEA), and tightening torque analyses. Preload analysis involves calculating the required preload for a given joint based on the loads it will experience during operation. Stress analysis involves calculating the stresses and strains in the joint’s bolt, nut, and other components, helping to determine if the joint can withstand the applied loads without failure or permanent deformation. Fatigue analysis involves calculating the fatigue life of a bolted joint based on the load cycles it is expected to experience during its lifetime to determine the required maintenance schedule for the joint and predict when it may need to be replaced. FEA analysis can help optimize the joint’s design and identify potential failure modes and critical areas. Tightening torque analysis involves calculating the torque required to achieve the desired preload in a bolted joint. Overall, a comprehensive analysis of a bolted joint involves considering multiple factors and performing numerous types of research to ensure that the joint is safe, secure, and reliable during operation.

Best practice of Bolted connection design

Bolted connection design is a crucial aspect of many engineering projects, and it is essential to follow best practices to ensure safety, reliability, and efficiency. Usually engineers have to select the correct type of bolt depending on the application. For example, high-strength bolts – for high loads. Additionally, corrosion-resistant bolts – for environments where exposure to moisture or other corrosive substances is expected. Also, it is crucial to determine the appropriate bolt size and quantity depending on the loads and stresses expected in the joint.

Proper bolt installation should be determined to ensure safety and reliability of the joint. This includes using proper torque specifications, lubricating bolts as necessary, and ensuring that the bolts are tightened to the correct tension. Furthermore, engineers must consider the effects of external forces such as wind or seismic activity. These forces can put additional stress on the joint and may require additional bolts or reinforcement. Later, regular inspections are required to ensure that bolts are still in good condition and able to withstand expected loads. Inspections should include checking for signs of corrosion or damage to bolts, as well as checking the tension of bolts to ensure that they have not become loose over time. By following these best practices, engineers can design bolted connections that are safe, reliable, and efficient.

AISC 360-10 Bolt Check

AISC 360-10 Bolt Check is implemented in SDC Verifier. The standard specifies the use of high-strength bolts, which are grouped according to material strength, as follows:

Group A	ASTM A325, A325M, F1852, A354 Grade BC, and A449
Group B	ASTM A490, A490M, F2280, and A354 Grade BD

The standard also covers the use of slip-critical connections, which rely on the friction between the bolted surfaces to transmit the load.

AISC 360-10 considers various types of loads in the design of bolted connections. In SDC Verifier, such checks following AISC 360-10 can be quickly done:

• Tensile and Shear Strength of Bolts and Threaded parts
• Combined tension and shear in Bearing-Type connections
• High-Strength bolts in Slip-Critical connections
• Bearing strength at bolt holes

Both methods of bolt check, prescribed by AISC 360-10 – ASD and LRFD are implemented in SDC Verifier.

Eurocode 3 Bolt Check

Eurocode 3 Bolts (EN 1993-1-8, 2005) – Bolt checks according to EN 1993-1-8:2005. (Section 3 Connections made with bolts, rivets, or pins) is implemented in SDC Verifier. For the EN 1993-1-8 requirements can be performed shear connection checks for the bearing type, slip-resistance at serviceability, slip-resistance at ultimate; and for the tension connection: for non-preloaded, and preloaded bolts.

All bolts, nuts, and washers should comply with 1.2.4 Reference Standards: Group 4. Bolts, nuts and washers, where all relevant industry Standards’ chapters are listed.
The rules in this Bolt Check are valid for the bolt classes given in the table below.

Bolt Class	4.6	4.8	5.6	5.8	6.8	8.8	10.9
fyb (N/mm2)	240	320	300	400	480	640	900
fub (N/mm2)	400	400	500	500	600	800	1000

For the EN 1993-1-8 bolt check, the following checks can be performed in SDC Verifier:

• Shear connection
  • A. bearing type;
  • B. slip-resistance at serviceability;
  • C. slip-resistance at ultimate;
• Tension connection
  • D. non-preloaded;
  • E. preloaded.

VDI 2230 Bolt Check

The standard sets a guideline for ISO metric bolted joints to prevent potential failures like bolt yielding due to overstressing, clamp plates crushing, bolted joint preload loss due to embedding, crushing and slipping, thread stripping and bolt fatigue failures. The VDI covers high-duty bolted joints with constant or alternating loads. The VDI 2230, Part1 covers guidelines for high-duty bolted joints with constant or alternating bolts, made of steel, M4–M39. In the Guideline VDI 2230 Part 1, bolted joints are treated which have to transmit constant or alternating working loads and which are designed with high duty bolts. In the figure below, the joint geometry with the relevant applied loads, as well as the suggested calculation procedure, are shown.

SDC Verifier has a special Bolt Library for VDI 2230 Bolt Check

Other Bolt standards

The standards for bolt checks vary between different countries and regions. Part of them bases on AISC and Eurocode with annexes, but the other part is autonomous. It is essential to use the relevant standards requirements for the specific application and location where the bolted joint will be used. Here are some examples of different codes for bolt checks which are widely used in Heavy Lifting, Oil and Gas, Maritime and Offshore and other industries.

• ISO 10721-2:1999 (Steel structures – Part 2: Fabrication and erection Section 4.7 Bolts, nuts and washers) International standard of ISO for steel structures.
• ASME BTH-1 – 2020 (Design of Below-the-Hook Lifting Devices) is an American standard for the design of below-the-hook lifting devices. This standard provides minimum structural and mechanical design requirements. The bolted connections are based solely on the holes of the hoist.
• NSTS 080307 (NASA Space Transportation System: Space Shuttle Criteria For Preloaded Bolts). This standard presents an essential, required set of methods and criteria that every preloaded bolt must meet. It also provides suggested criteria and procedures that should be understood and considered in the design and analysis of prestressed connections.
• ASTM A325M-00 Standard Specification for High-Strength Bolts for Structural Steel Joints [Metric]
• Canadian Bolts Standards. CSA S16, Design of steel structures, in Chapter S16-09 the requirements for steel bolts, bolt heads, nuts, and washers are specified.
• CSA A23.3-04 (Design of Concrete Structures. Annex D (informative) Anchorage) is the Canadian standard for the design of concrete structures. This standard is mainly concerned with anchor bolts. Some requirements of this standard are in accordance with the National Building Code of Canada.
• BS 5950 (Structural use of steelwork in building) is a British Standard for the structural use of steelwork in buildings. This particular standard gives recommendations for the design of rolled and welded sections, including bolted connections. The structure of the standard is similar to the Eurocode.
• AS 4100 (Steel structures. Section 9.2 Design of Bolts) is the Australian standard for steel structures. This standard provides the minimum requirements for the design of bolted connections in structures using the limit state design method. It applies to steel buildings, structures and cranes.
• JIS B 8821 (Calculation standards for steel structures of cranes) is the Japanese standard for the calculation of steel structures of cranes. Crane structures are specified in JIS B 0146-1.
• CoP – SuoS (Code of Practice for the Structural Use of Steel. Section 9.3 Bolted connections) is the Hong Kong standard. This standard provides recommendations for the design of steel buildings and structures. This standard uses the limit state design method.
• GB 50017 (Standard for design of steel structures. Section 11 Connections) is the Chinese national standard. All calculations except fatigue are based on LRFD.
• Indian Standard IS 800 (2007) General Construction in Steel — Code of Practice (Section 10 Connections. 10.3 Bearing Type Bolts) It is the main document for any structural design and influences many other codes relating to steel structures. This standard gives only general guidance on the various loads to be considered in the design.
• IS 4000 is an Indian Standard for High Strength Bolts in Steel Structures (First Revision) adopted in 1992 by the Bureau of Indian Standards.
• The Egyptian Code of Practice for Steel Construction (ECP) contains requirements for Bolts according to LRFD and ASD.

Comparison for AISC 360-10, EN 1993-1-8, VDI 2230 Bolted Connections Checks

SDC Verifier implements these standards as widely used in many industries globally for verification of structures with bolted joints. Below is the general comparison of AISC 360-10, EN 1993-1-8 (Eurocode Bolt Check), VDI 2230 Bolted Connections Checks prepared by our engineering team.

	EN 1993-1-8	AISC 360-10	VDI 2230 (Part 1)
Bolt joint type (number of bolts in the connection)	Multiple bolt joint	Multiple bolt joint	Single bolt joint
Bolt joint type	Non-preloaded and preloaded	Non-preloaded and preloaded	Preloaded
Bolt classes	4.6; 5.6; 5.8; 6.8; 8.8 and 10.9	4.6; 5.6; 5.8; 6.8; 8.8 and 10.9	8.8; 10.9 and 12.9
Minimum and maximum spacing and end and edge distances	Prescribed in the tables	Prescribed in the tables	Not prescribed
Bolts strength check	Included	Included	Included
Bolts fatigue check	Not included	Not included	Included

Summary

With FEA simulation capabilities of SDC Verifier combined with a growing standards library, any design can be simulated and checked according to industry rules. Besides, the number of various features aimed to optimize the structure and save engineers’ time is increasing continuously according to users’ demands.