If you’ve ever stood in front of a large-scale space truss structure—think a long-span airport terminal roof, a seismic-resistant sports arena, or a bridge deck that needs to handle both movement and heavy loads—you’ve probably wondered how engineers make that seemingly impossible balance look so easy. A huge part of that secret lies in space truss rubber bearings, the unsung heroes that let these structures move safely under seismic activity, temperature changes, or wind loads while keeping their integrity intact. As a supplier of space truss rubber bearings, I talk to project managers, structural engineers, and contractors every week who ask the same question: should I go with spherical or cylindrical bearings for my project? There’s no one-size-fits-all answer, so let’s break this down based on real-world use cases, engineering specs, and what actually works for different types of projects.
First, let’s get on the same page about what these two bearing types do, because their core functions are similar but their capabilities diverge in important ways. Both are part of the broader family of vibration-mitigation products that keep structures safe during dynamic events, working closely with other tools like Pot Rubber Bearings, Viscoelastic Dampers (VED), Viscous Fluid Dampers, Metal Yield Dampers, and Tuned Mass Dampers (TMD) to manage movement and reduce structural stress. Space truss bearings specifically support the truss nodes, transferring vertical loads to the foundation while allowing horizontal and rotational movement—something that’s critical for space trusses, which are designed to be lightweight but can’t handle the same rigid stresses as solid structures.
Cylindrical space truss rubber bearings are the more straightforward of the two, shaped like a short, hollow cylinder with a rubber core laminated between steel plates. Their design limits movement to two primary horizontal axes (usually X and Y) and allows for a fixed rotational axis along the cylinder’s centerline. Think of them like a heavy-duty drawer slider, but for entire building sections. Spherical bearings, on the other hand, have a curved, ball-shaped rubber core enclosed in a curved steel housing, which means they can move freely in all horizontal directions and rotate around any axis—no fixed line of movement. They’re like a ball joint for your structure, giving far more flexibility but with a more complex design.
Let’s start with when cylindrical bearings make the most sense, because that’s where I see the most common (and most successful) applications for this type. The sweet spot for cylindrical bearings is projects where movement is predictable and limited to specific directions, and where you want to keep costs down without sacrificing reliability. For example, most standard bridge overpasses use cylindrical bearings because their movement is primarily along the length of the bridge (thermal expansion and contraction from temperature changes, and small horizontal forces from traffic). I recently worked with a team on a 2.5km highway overpass project in the Midwest that went with cylindrical bearings for exactly that reason—they calculated that the maximum horizontal movement needed was just 120mm along the bridge axis, with almost no cross-axis movement, so a cylindrical bearing’s fixed rotational axis was perfect. They saved about 18% on bearing costs compared to spherical, and after two years of monitoring, the bearings are holding up exactly as expected.
Another big use case for cylindrical bearings is low-seismic regions. If your project is in an area where earthquakes are rare and low-magnitude, you don’t need the extra movement capacity of spherical bearings. I often advise industrial warehouses and standard retail strip malls in places like the central U.S. (where seismic activity is minimal) to go with cylindrical. These projects usually have simple, rectangular space trusses that don’t experience complex rotational movement, so the cylindrical bearing’s limits aren’t a constraint. Also, cylindrical bearings are simpler to install—they come in pre-aligned units that just bolt to the truss node and foundation, so contractors save time on site, which translates to lower overall project costs. That’s a huge win for budget-conscious projects where every hour of installation matters.
But wait, I should be honest about the limitations of cylindrical bearings, because they aren’t right for everything. The fixed rotational axis is a problem when trusses need to rotate in multiple directions, like when wind blows asymmetrically on a long-span roof. For example, a 180m-long exhibition hall I worked on a few years ago tried cylindrical bearings first, and halfway through the design, we realized the wind load calculations showed that the truss nodes on the east side would need to rotate up to 2.5 degrees in both the X and Y axes. The cylindrical bearings we’d specified could only handle rotation along the Y axis, so we had to switch, which added some costs and delay. That’s where spherical bearings shine, and that’s what brings us to when spherical is the clear choice.
Spherical space truss rubber bearings are built for projects where movement is unpredictable, multi-directional, or subject to seismic activity. The curved ball-and-socket design lets them rotate up to 5 degrees (sometimes more, depending on the design) in any direction, and they can handle horizontal movement along any axis, not just two. That makes them ideal for high-seismic zones, like the West Coast of the U.S., Japan, or parts of Europe. I recently supported a project for a new hospital in Los Angeles, which is in a high-seismic area, and the structural team specified spherical bearings for all 42 truss nodes. Their reasoning was simple: during an earthquake, the ground can move in any direction, and the truss can rotate as it distributes the seismic load, so cylindrical bearings’ fixed axis could cause stress concentrations that might lead to failure. The spherical bearings evenly distribute that movement, reducing the risk of damage to the truss and the building above.
Long-span space trusses are another no-brainer for spherical bearings. If you’re building a roof that’s wider than 100m—like an airport terminal, a sports arena, or a train station—thermal expansion and contraction can be extreme, and wind loads can create asymmetrical movement across the entire span. Cylindrical bearings would only allow movement along one axis, so the opposite side of the roof would be forced to move in a way that creates stress in the truss members. Spherical bearings let every truss node move independently, so the entire roof can shift and rotate as needed without straining the structure. The same goes for cable-stayed bridges or large roof structures with complex geometries, where truss nodes aren’t aligned in a simple grid.
Another advantage of spherical bearings is their ability to handle uneven settling. Over time, foundations can settle slightly differently—for example, if part of a building is on fill soil and another part is on bedrock. Cylindrical bearings can only compensate for linear movement, but spherical bearings can adjust for both horizontal movement and rotational settlement, keeping the truss aligned without creating stress. I had a client on a university science building project that initially planned to use cylindrical bearings, but when their geotechnical report showed 12mm of differential settlement across the building’s length, we switched to spherical. A year later, when we did a structural audit, there were no signs of stress in the truss, which would have been a problem with cylindrical bearings.
Of course, spherical bearings aren’t perfect—they cost more, are more complex to install, and require more precise alignment on site. The curved design means more machining and material, so the upfront cost is usually 20-30% higher than a cylindrical bearing of the same load capacity. They also need to be handled more carefully during installation, because the ball and socket can get damaged if dropped or improperly aligned, which means contractors need to take extra steps to protect them. That’s why it’s crucial to work with a reputable supplier who can provide pre-tested, aligned spherical bearings to reduce installation risk.
Let’s talk about some edge cases where you might not be sure which to choose, because these are the projects that make the difference between a good bearing selection and a great one. For example, a medium-span roof in a moderate-seismic zone—say, a 60m-long community center in Denver, which has some seismic activity but not as much as Los Angeles. The structural team there initially wanted to go with spherical bearings, but after doing a cost-benefit analysis, they found that the seismic movement was low enough that cylindrical bearings with a custom rotational axis could handle the load. Wait, but that’s not exactly a pure cylindrical bearing—we modified the cylindrical bearing to have a slight curved surface on the upper plate, so it could rotate a few degrees in both axes without the full spherical design. That’s a middle-ground option that works for some medium-complexity projects.
Another edge case is bridges that need to handle both thermal movement and seismic loads. A lot of people think cylindrical bearings are only for low-seismic bridges, but I’ve worked on bridges that combine cylindrical bearings with Viscous Fluid Dampers to handle seismic movement. The cylindrical bearing handles the regular thermal movement, and the dampers kick in during an earthquake to control the extra movement. That’s a great way to save money without sacrificing safety for bridges in moderate-seismic zones.
I also want to mention load capacity, because that’s a big factor for truss bearings. Both cylindrical and spherical bearings come in a wide range of load capacities, but spherical bearings tend to be better for very heavy loads. If your truss nodes are carrying 1000 tons or more, the spherical design distributes the load evenly across the curved surface, while cylindrical bearings can have higher stress concentrations along the edges of the cylinder. That makes spherical the better choice for heavy industrial structures, power plant support structures, or large bridge piers.
So, putting this all together, here’s a quick guide to help you decide: go with cylindrical space truss rubber bearings if your project is in a low-seismic zone, has limited, predictable movement along specific axes, is a standard span (under 80m), and you’re focused on upfront and installation cost savings. Go with spherical bearings if your project is in a high-seismic zone, has long spans (over 80m), unpredictable or multi-directional movement, uneven foundation settling, or very heavy truss loads. For medium-seismic, medium-span projects, consider a hybrid approach: cylindrical bearings combined with dampers like Viscoelastic Dampers or Metal Yield Dampers to add the movement capacity without the full cost of spherical.
As a space truss rubber bearings supplier, I’ve seen firsthand how the wrong bearing selection can lead to costly delays, structural stress, and even safety issues. Last year, we worked on a residential development with a 90m-long truss roof that used cylindrical bearings in a moderate-seismic zone. Within 18 months, a small earthquake caused the truss to develop hairline cracks at the node points, because the cylindrical bearings couldn’t handle the cross-axis rotational movement. We had to supply and install spherical bearings to fix the problem, which cost the developer more than double what they would have paid for the right bearings upfront. That’s why taking the time to do the movement calculations, seismic zone assessment, and load analysis before choosing your bearings is so critical.
No matter which type you choose, it’s important to work with a supplier who can provide bearings tested to international standards—like ISO 10134 for bridge bearings or ASTM D4015 for rubber bearings. All our space truss bearings, both spherical and cylindrical, undergo rigorous load testing, movement testing, and environmental testing to make sure they can handle extreme temperatures, humidity, and dynamic loads. We also work with engineers to customize bearings for specific projects, whether that’s adjusting the movement range, load capacity, or material composition for harsh environments.
If you’re still not sure which bearing type is right for your project, or if you want to talk about combining bearings with vibration mitigation products like dampers or Tuned Mass Dampers (TMD) for extra safety, I encourage you to reach out. Every project is unique, and a one-size-fits-all approach doesn’t work when it comes to structural bearings. The right bearing selection will keep your structure safe for decades, while the wrong one can lead to expensive repairs or even safety risks.
Don’t guess when it comes to your space truss bearings. Whether you need standard cylindrical bearings for a warehouse, custom spherical bearings for a hospital, or a hybrid solution for a bridge, we can provide the right products and expert guidance to fit your project’s needs. Contact us today to start the conversation about your bearing requirements, and let’s make sure your structure is built to last.
References
- International Organization for Standardization. (2017). ISO 10134:2017, Rubber and steel laminated bearings for bridges and other structures — Specifications.
- American Society for Testing and Materials. (2020). ASTM D4015-20, Standard Test Method for Rubber Properties in Compression.
- Kelly, J. M. (2013). Earthquake Resistant Design with Rubber (2nd ed.). John Wiley & Sons.
- Priestley, M. J. N., Seible, F., & Calvi, G. M. (1996). Seismic Design of Bridges. John Wiley & Sons.
- Zhang, H., & Li, A. (2021). Performance comparison of spherical and cylindrical bearings for long-span space trusses under seismic loads. Journal of Structural Engineering, 147(8), 04021092.