Double Raft Foundation Seismic Isolation via Teflon Sliding
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Solution Overview
Problem
Current seismic protection systems, such as energy dissipators, are ineffective for light-weight wooden or reinforced concrete buildings with two or three floors during earthquakes, and existing raft foundations do not adequately insulate structures from seismic stress.
Innovation Solution
A double raft foundation system featuring a lower raft with a Teflon layer and an upper raft composed of steel and/or Teflon slabs with low friction coefficients, allowing the upper raft to slide on the lower raft during earthquakes, thereby decoupling the superstructure from ground seismic energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If bitumen sliding layer is used in double raft foundation, then the foundation can provide seismic insulation, but the friction coefficient between sliding layer and plates is very high (approximately 0.5)
Solution Approach 1:
The patent changes the material parameter of the sliding layer from bitumen to Teflon, which fundamentally alters the friction coefficient from approximately 0.5 to ≤0.04. This parameter change enables the sliding layer to effectively reduce friction between the lower and upper rafts during earthquakes, allowing the upper raft to slide freely and isolate seismic stresses from the superstructure.
Solution Approach 2:
The patent uses Teflon plates on the upper raft that replicate and interact with the Teflon sliding layer on the lower raft. This copying approach ensures consistent low-friction characteristics throughout the system, where both the sliding layer and the contacting plates are made of the same low-friction material to maximize seismic insulation effectiveness.
2Object-affected harmful factors
If energy dissipators are applied to protect building structure from earthquakes, then seismic protection is achieved, but the system is only effective for heavy structures with minimum four floors
Solution Approach 1:
The patent segments the foundation system into distinct components: a lower raft with Teflon sliding layer, Teflon plates on the upper raft, and a superstructure. This segmentation creates a modular seismic protection system that can be independently applied to any building type regardless of height or weight, making it universally adaptable from single-story to multi-story structures.
Solution Approach 2:
The Teflon sliding layer and Teflon plates act as an intermediary mechanism between the lower and upper rafts. This intermediary low-friction interface allows relative movement and seismic energy dissipation without requiring the superstructure to be heavy, enabling effective seismic protection for light-weight structures of any size.
3Object-affected harmful factors
If double raft foundation with sliding layer is used, then seismic insulation is provided, but the sliding system requires maintenance and may lose efficiency over time
Solution Approach 1:
The Teflon material provides self-lubricating properties that enable the sliding system to maintain low friction coefficients over time without external intervention. The material's inherent characteristics ensure continuous self-maintenance, preventing sticking and reducing wear, thereby maintaining reliable seismic insulation performance throughout the structure's lifetime without requiring periodic maintenance.
4Ease of operation
If Teflon layer and steel/Teflon slabs are used with low friction coefficient, then the upper raft can slide on the lower raft during earthquakes, but the manufacturing and installation complexity increases
Solution Approach 1:
The patent uses homogeneous Teflon material for both the sliding layer on the lower raft and the plates on the upper raft. This homogeneity simplifies the manufacturing process and ensures consistent performance, as the same material can be produced using identical processes and will interact predictably with itself, reducing installation complexity despite the specialized material requirements.
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 system effectively dissipates seismic energy, reduces structural stress, and maintains structural integrity, making it suitable for light-weight structures while minimizing costs and requiring no maintenance, with the Teflon-steel or Teflon-Teflon interface providing excellent friction reduction and durability.
Implementation Method 1
a layer of material with a low friction coefficient applied jointly on the lower raft, a platform comprising a plurality of coplanar slabs of material with a low friction coefficient, slidingly disposed on said layer with a low friction coefficient of the lower raft
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A double raft foundation (1) for buildings comprises: a lower raft (3), a layer (4) of a material with a low friction coefficient applied on the lower raft (3), a platform comprising slabs (5) of material with a low friction coefficient, slidingly disposed on said layer (4), an upper raft (6) joined with said slab platform (5) and a superstructure (60) joined with the upper raft (6); wherein the upper raft (6) is disposed on the lower raft (3) in such manner that, in case of an earthquake, said platform of slabs (5) of the upper raft can slide slidingly on said layer (4) of the lower raft, allowing the upper raft to move relatively with respect to the lower raft.