Compliant Deck Tower Earthquake Isolation
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Solution Overview
Problem
Offshore oil and gas platforms face challenges in isolating surface facilities from earthquake energy, with existing solutions like friction bearings being prone to deck uplift and maintenance issues, and compliant towers being economically viable only in deep water.
Innovation Solution
A compliant deck tower design featuring a working deck structure with articulated legs and flexible attachment points, utilizing universal joints or structural flex joints to create a natural vibration period greater than earthquake energy but less than storm energy, along with sub-structure attachment and isolation bearings to decouple deck energy from substructure-soil system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If friction bearings are used to isolate the deck from the lower substructure, then earthquake energy isolation is improved, but deck uplift and toppling risk increase due to dependence on vertical load
Solution Approach 1:
The patent introduces an intermediary mechanism (isolation bearings with rotational constraint) between the deck and substructure that mediates the interaction during earthquakes. This intermediary provides earthquake energy isolation while preventing deck uplift through rotational constraint, resolving the contradiction between isolation effectiveness and deck stability.
2Object-affected harmful factors
If compliant towers are designed with flexible structure to achieve natural period above storm and earthquake energy ranges, then earthquake energy isolation is improved, but economic viability is limited to deep water environments
Solution Approach 1:
The patent segments the compliant tower system into distinct functional components: the substructure, the isolation bearing system, and the deck. This segmentation allows the earthquake isolation function to be achieved through the bearing system rather than requiring the entire structure to be compliant, enabling economic viability in both shallow and deep water environments while maintaining earthquake energy isolation.
3Object-affected harmful factors
If isolation bearings are used to decouple deck energy from substructure-soil system, then earthquake energy isolation is improved, but surface friction deterioration requires continuous monitoring and maintenance
Solution Approach 1:
The patent replaces the traditional friction-based isolation mechanism with a rotational constraint mechanism. Instead of relying on surface friction that deteriorates in marine environments, the new mechanism uses rotational constraint at the bearing to provide isolation, eliminating the need for continuous monitoring and maintenance while maintaining effective earthquake energy isolation.
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 compliant deck tower effectively isolates deck energy from earthquake excitation, minimizing deck uplift and maintenance needs, and is economically feasible in both deep and shallow water environments, providing enhanced stability and reduced risk of toppling or shearing.
Implementation Method 1
The stabilization against rotational moment provides a restoration couple sufficient to establish a natural vibration period greater than the peak period range of earthquake energy but less than that of storm energy.
Implementation Method 2
establish a natural vibration period greater than the peak period range of earthquake energy but less than that of storm energy
Implementation Method 3
CTs yield to excitation energy by oscillating around a bottom underwater section (or base) in a controlled inverted pendulum manner. This oscillation creates an inertial restoring force which opposes the applied forces.
Implementation Method 4
oscillating around a bottom underwater section (or base) in a controlled inverted pendulum manner
Data Source
AI summary
Compliant offshore platforms with isolated decks using one or more bearings located on a generally horizontal plane that is in proximity to the vertical center of gravity of the deck.