Bridge bearing selection: Plate type rubber bearings, bowl type bearings, spherical bearings. Why is it said that "what is suitable is the best"?

In the selection of bridge bearings, the core principle that has been verified in engineering practice is' what is suitable is the best '. Plate type, bowl type, and spherical bearings each have their unique performance and applicable scenarios. It is meaningless to talk about their advantages and disadvantages without specific engineering conditions. The key lies in whether they match the stress characteristics, environmental conditions, and usage needs of the bridge.

1、 Core characteristics and applicable boundaries of three types of supports

1. Plate type support

Core advantages: simple structure, low cost, easy installation, mainly relying on the elastic deformation of rubber to bear vertical loads and adapt to small angle rotation.

Limitations: Small displacement (usually ≤ 50mm), limited bearing capacity (usually ≤ 3000kN), weak adaptability to temperature changes and large turning angles.

Suitable scenario: Small and medium span bridges (such as highway bridges with a span of ≤ 30m and urban branch bridges), working conditions with small loads and low deformation requirements.

2. Basin type support

Core advantages: Through the pressure bearing of rubber plates inside the steel basin, it has a large bearing capacity (up to tens of thousands of kN), strong horizontal displacement ability (able to adapt to displacement of ± 200mm or more), and flexible rotation.

Limitations: The structure is complex, the cost is high, the installation accuracy is required, and regular maintenance is needed to prevent steel corrosion.

Suitable scenarios: Long span bridges (such as highway bridges and railway bridges with a span of 30-100m), heavy loads (such as bridges with heavy vehicle traffic), or working conditions with significant horizontal displacement (such as continuous beam bridges and curved bridges).

3. Spherical bearings

Core advantage: It achieves flexible rotation at multiple angles through spherical rotation, and can adapt to extremely large angles (up to 0.05 rad or more) and complex forces (such as bidirectional horizontal forces), with excellent seismic performance.

Limitations: The highest cost, precise structure, and extremely strict requirements for construction and maintenance.

Suitable scenarios: ultra long span bridges (such as cable-stayed bridges, suspension bridges), wide or curved bridges (requiring multi-directional displacement adaptation), bridges in earthquake prone areas (requiring absorption of seismic energy), and other engineering projects with extremely high requirements for rotation and displacement

2、 The core criteria for determining suitability

1. Bridge span and load: Small spans and light loads can be met with plate supports, without the need to pay additional costs for "high performance"; Long spans and heavy loads must rely on the bearing capacity of bowl or spherical bearings.

2. Displacement and rotation requirements: The displacement and rotation of simply supported beam bridges are small, and the plate supports are sufficient; Continuous beam bridges and curved bridges have large displacements and angles, requiring bowl shaped supports; The complex deformation of cable-stayed bridges and suspension bridges cannot be achieved with non spherical bearings.

3. Environmental and maintenance conditions: In humid and corrosive environments, the rubber of plate bearings is prone to aging, and it is necessary to prioritize pot or spherical bearings with better anti-corrosion performance; If the maintenance of bridges in remote areas is inconvenient, simple plate bearings are actually more "suitable" (reducing maintenance costs).

4. Economic balance: Blindly choosing high-performance bearings can lead to skyrocketing costs (such as using spherical bearings for small and medium-sized bridges, which may increase the cost several times), while choosing low-end bearings may pose safety hazards (such as using plate bearings for large-span bridges, which are prone to premature failure due to insufficient bearing capacity).

3、 Summary: There is no 'best', only 'most suitable'

The core function of bridge bearings is to "transfer loads+adapt to deformation", and the essence of selection is to find the optimal solution between safety, performance, and cost by matching the specific needs of the bridge. For example, using slab supports for rural small bridges is both cost-effective and sufficient; The use of spherical bearings for cross river bridges is necessary to ensure long-term safety under complex stress conditions. The selection of "high-performance" that deviates from engineering reality may actually result in resource waste or functional overcapacity, while the selection of "suitable" can achieve multiple goals of "safety, reliability, economic rationality, and convenient operation and maintenance" - this is the deep logic of "what is suitable is the best".