The following text explores this topic in detail. It is an excerpt from the white paper: "Bridge Design, Construction, and Maintenance: Insights and Best Practices in a Rapidly Changing Industry", produced by Nord-Lock Group.
Many European bridges are part of aging infrastructure built in the middle of the 20th century. This requires maintenance and renewal of bridges to better meet the ever-increasing traffic demands. History, regional preferences, and bridge types are all key background factors that influence the connection methods used in bridge construction and maintenance.
There are many factors to consider when deciding whether to use welding or bolting to connect bridge components together. In some cases, existing preferences may determine this decision. However, in order to make the best decision, it is important to consider each item individually.
A difficult choice
Historically, bridges and other steel structures were riveted, such as the Golden Gate Bridge. The process involves heat treatment and forging of rivets, and then cooling through a process called annealing. A single rivet is not very strong, which means that many rivets must be used to ensure the safety of the structure. This is also a cumbersome process and is no longer used in the bridge construction department.
However, although riveted bridges are no longer being built, existing bridges that use rivets still require maintenance. Bolts are usually used to replace worn rivets, especially high-strength bolts designed to resemble rivets. Due to the degradation of bridge materials, welding is not a viable option for maintaining old bridge joints, which can make it unsafe.
Bolting and welding are currently the two most popular methods of connecting components together. When it comes to which method to use, the decision may be as controversial and country-specific as the decision between concrete and steel. It must also be pointed out that some countries have very high levels of welding qualifications. This is an example of how the national environment can play a role in the preferred construction method. Bridge
In addition to the influence of country preference, there are several important factors that can determine whether a part is welded or bolted. One of them is the type of bridge being built-see the infographic on the next page.
For larger bridges, hollow box sections are usually used because they can absorb torsional stress well and only the outside needs to be considered when planning corrosion protection. The disadvantage of the cross-section of hollow boxes is that they can only be accessed from one side, making it difficult to connect with bolts. Therefore, welding is the most logical method. Tolerance and offset compensation are also related to larger structures. There is no error in the bolt connection, because the bolt must be accurately installed in the pre-existing hole. Welding is more flexible because you can compensate for the offset when necessary. Different types of bridges
On the other hand, truss bridges can be bolted well due to their interlocking triangular cross-sections. However, the size must also be taken into consideration. Small truss bridges may be welded together in the production workshop and transported to the construction site as a whole. Nevertheless, even though welding is the preferred connection method, bolted connections will still be widely used for bridges. This is because secondary structures such as railings and soundproof walls are usually bolted. These main structures (such as cable clamps, bearings, transition joint structures) are also dynamically loaded to compensate for bridge movement.
Temporary bridges are almost completely bolted, because they are demolished and rebuilt elsewhere every few years. Since bolted connections create temporary joint connections, these joints can be easily disassembled and the bolts and washers themselves can be reused. Since welding produces permanent joint connections, it is very complicated, expensive and time-consuming to use it for temporary bridges. A lot of effort must be invested in creating welds first and then removing them. In this way, bolted connection is a more effective and beneficial method of use. Efficiency and ease of use
Efficiency and ease of use are also important factors when considering welding or bolting. This includes the decision to connect at the factory or on-site. Welding usually requires certified welders and advanced tools, and is considered risky due to the high temperatures involved. Therefore, it will be faster and easier to perform this task in a factory where everything is ready. Due to the high cost of setting up welding and testing facilities on site, it is also cheaper to perform welding in the factory, which also leads to longer bridge erection times.
In fact, if you want to connect on site, bolting is usually the simplest and most effective method. This is because bolting is a more controllable operation and will not cause any unnecessary risks in the construction environment. These components are also easy to transport and install because they can be used without any special equipment. In most cases, only a simple hand-held torque wrench is required to operate. Unlike welding, bolted connections have the added advantage of being non-permanent, which means that accidental problems can be repaired faster, easier, and cheaper.
This article is an excerpt from a white paper by the Nord-Lock Group: "Bridge Design, Construction, and Maintenance: Insights and Best Practices in a Rapidly Changing Industry (2021)".
To download a free paper, please visit:
Will joined Fastener Fixing Magazine in 2007. In the past 12 years, he has experienced all aspects of the fastener industry-interviewing key figures in the industry, visiting leading companies and exhibitions around the world.
Will manages the content strategy of all platforms and is the guardian of the magazine's prestigious high editorial standards.
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