Fire Resistant Steel-Concrete Floor With Catenary Tension Members
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Solution Overview
Problem
Steel-concrete floor structures require expensive fire protection measures for structural steel members during fires, which increase building costs and reduce the weight advantage over full concrete structures, while existing solutions for fire-resistant composite structures are not competitive or widely applied.
Innovation Solution
A steel-concrete floor structure design that incorporates tension members extending through the concrete slab between anchor points in fire-resistant bearing structures, allowing these members to support the slab by catenary effect when steel beams lose strength and stiffness in a fire, eliminating the need for expensive fire protection measures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fire protection measures are applied to steel beams, then fire resistance is improved, but building costs increase and weight increases
Solution Approach 1:
The invention extracts the fire protection function from the steel beams themselves and relocates it to the concrete slab through tension members. The steel beams are left unprotected, while the concrete slab is designed to actively engage in fire resistance through its tensile members that form a catenary arch structure during fire exposure.
Solution Approach 2:
The tension members embedded in the concrete slab act as intermediaries that transfer and redistribute loads during fire scenarios. These members mediate between the unprotected steel beams and the supporting structure, allowing the concrete slab to protect the overall structure from fire damage without protecting the steel beams directly.
2Reliability
If concrete encasement is provided for steel beams, then fire resistance is improved, but weight increases substantially
Solution Approach 1:
The invention removes the need for concrete encasement of steel beams by extracting the fire protection function and placing it in the concrete slab instead. This eliminates the additional weight that would result from encasing the beams while maintaining fire resistance through the slab's tension member system.
3Reliability
If tension members are made of steel with high tensile strength at high temperatures, then fire resistance is improved, but such materials are not yet competitive or widely applied
Solution Approach 1:
The invention changes the temperature parameter exposure for the tension members by embedding them in the concrete slab. The concrete provides thermal insulation, keeping the tension members at lower temperatures during fire scenarios, allowing the use of conventional steel materials that are widely available and cost-effective rather than requiring specialized high-temperature steel.
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 structure maintains outstanding performance in a fire scenario without requiring any fire protection, effectively limiting slab deflections and maintaining structural integrity, often surpassing the performance of protected steel beams or concrete encasements.
Implementation Method 1
the tension members extending through the concrete slab, wherein they are heating up more slowly than the structural steel members
Implementation Method 2
the tension members extending through the concrete slab are capable of supporting the loaded slab by catenary effect
Data Source
Figure 1~4
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Figure 8~9
AI summary
A steel-concrete floor structure (10), designed for having a prescribed fire resistance when exposed to a prescribed fire scenario in a fire compartment immediately below the steel-concrete floor structure (10), comprises horizontally extending structural steel members (12) and a concrete slab (14). In normal operation, these structural steel members (12) have to take the main part of the tensile stresses generated by the bending moment. It further comprises a plurality of tension members (34), each of these tension members (34) horizontally extending through the concrete slab (14) between two anchor points. These anchor points (36, 36', 36'', 36''') are arranged in one or more fire resistant bearing structures (38, 38', 38'') within the fire compartment, and/or in one or more external bearing structures (38'''), so that, when the strength and stiffness of the horizontal structural steel members (12) substantially diminish in the prescribed fire scenario, the tension members (34) extending through the concrete slab (14) are capable of supporting the loaded slab (14) by catenary effect and of limiting the deflection thereof.