Sliding Pendulum Seismic Isolation with Segmented Bearings
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Solution Overview
Problem
Existing sliding pendulum seismic isolation systems are costly and less effective for service level earthquakes, as they are designed primarily for stronger design level earthquakes, leading to increased costs and reduced protection for structures during service level earthquakes due to larger displacement requirements.
Innovation Solution
Configuring multiple independent sliding pendulum mechanisms in series, with varying effective lengths and frictions that activate at different seismic motion strengths, and specific bearing configurations tailored to support types and loads, to reduce seismic forces and costs by optimizing performance for different earthquake levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If sliding pendulum bearings are designed for design level earthquakes, then they can resist strong seismic forces, but they become less effective and more costly for service level earthquakes
Solution Approach 1:
The bearing is divided into multiple independent sliding pendulum mechanisms with different effective lengths and friction coefficients. Each mechanism is optimized for specific earthquake intensity levels, allowing the system to provide appropriate protection for both service level and design level earthquakes rather than being over-designed for the strongest event.
Solution Approach 2:
Different portions of the bearing have different friction coefficients and pendulum lengths tailored to specific earthquake scenarios. The bearing surfaces and sliders are configured with varying local properties to optimize performance for different earthquake intensities, with lower friction for service level events and higher friction for design level events.
2Length of moving object
If bearings are designed to accommodate maximum credible earthquake displacements, then they meet building code requirements, but costs of bearings and structural frames increase substantially
Solution Approach 1:
The displacement capacity is segmented across multiple mechanisms with different travel ranges. Each mechanism handles a portion of the total displacement, allowing the system to accommodate large maximum credible earthquake displacements without requiring each individual component to be oversized and expensive.
Solution Approach 2:
The bearing system dynamically adjusts its characteristics through the sequential activation of different sliding pendulum mechanisms. As displacement increases from service level to design level to maximum credible earthquake levels, different mechanisms engage, providing cost-effective accommodation of varying displacement demands.
3Device complexity
If all sliders slide in unison during seismic movements, then the system has one effective pendulum length, but it cannot optimize performance for different earthquake intensities
Solution Approach 1:
The slider assembly is segmented into multiple independent sliding pendulum mechanisms that can operate independently. Each mechanism has its own slider(s) that can slide at different rates and engage at different displacement thresholds, enabling the system to adapt to varying earthquake intensities while maintaining a relatively simple overall structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution reduces earthquake forces and displacements on structures, lowers the cost of isolation bearings and structural frames, and effectively accommodates various seismic loads and displacements, making the system more cost-effective and efficient across different earthquake intensities.
Implementation Method 1
The friction, which occurs between the sliders and the concave surfaces, serves the important function of dissipating the energy associated with the seismic movements
Implementation Method 2
The lifting of the structure results in an equivalent pendulum motion. The radii of curvature of the concave surfaces result in an effective length of the pendulum arm, that determines the dynamic natural period of vibration of the isolation system
Data Source
AI summary
An inventive method is presented for a sliding pendulum seismic isolation system that reduces seismic forces on the supported structure and reduces the costs of the isolation bearings, seismic gaps, and supported structural frame. The inventive method is to configure the isolation system to achieve increased effective friction with increased displacement amplitudes, and to employ specific bearing configurations that suit the different types and magnitudes of loads present at particular structure support locations. Three bearing configurations are presented which are comprised of multiple sliders that slide along different concave spherical surfaces, each constituting an independent sliding pendulum mechanism having a specified pendulum length and friction. Two bearing configurations are presented which are comprised of multiple sliders that slide along different concave or convex cylindrical surfaces, one configured to carry both compression and tension loads, and one configured to be cost-effective for carrying light compression loads and accommodating large displacements.