Pre-stressed Concrete Box Culvert Span Extension
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Solution Overview
Problem
Existing concrete box culverts have limited span lengths due to excessive bending moments and require strong soil bearing capacity, making them impractical for longer spans and low-bearing capacity soils, and are challenging to fabricate and transport for larger dimensions.
Innovation Solution
A pre-stressed concrete box culvert design featuring three-sided sections with male and female connectors and post-tensioning ducts, allowing for increased span lengths by dividing the culvert into sections that can be assembled on-site, reducing fabrication and transportation complexities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the span of concrete box culvert is increased beyond 35 feet, then the bending moment in the top slab becomes prohibitively large, but using traditional free-standing rebar cannot achieve the required strength
Solution Approach 1:
The patent changes the reinforcement method from free-standing rebar to pre-stressed tendons, fundamentally altering the structural parameters. Pre-stressing applies compressive forces to the concrete before loading, enabling the top slab to resist large bending moments over spans exceeding 35 feet without requiring prohibitively large section dimensions or excessive reinforcement.
Solution Approach 2:
The patent employs a composite system combining pre-stressed concrete with high-strength steel tendons. This composite approach allows the concrete to carry compressive loads effectively while the pre-stressed steel provides tensile resistance, enabling long-span capability that neither material could achieve alone with traditional reinforcement methods.
2Adaptability or versatility
If a four-sided box culvert is designed with large span (40 feet) and large height (10 feet or more), then the load is spread across the entire bottom slab requiring less soil bearing capacity, but fabrication, transportation, and installation become logistically challenging
Solution Approach 1:
The patent divides the four-sided box culvert into two separate three-sided sections that can be fabricated and transported independently. Each section includes sidewalls extending from a top slab, with connection elements provided for joining them in the field. This segmentation enables practical fabrication and transportation of large-span culverts while maintaining the load-spreading benefits of the four-sided configuration when assembled.
3Ease of manufacture
If three-sided box culvert is used with standard span limitation (30-35 feet), then fabrication and transportation are easier, but longer spans cannot be achieved
Solution Approach 1:
The patent applies pre-stressing technology to the three-sided box culvert, changing the structural behavior from simply supported to continuously supported with negative moment regions. This parameter change in the structural system allows spans significantly longer than the traditional 30-35 foot limitation while maintaining reasonable section dimensions and fabrication complexity.
4Strength
If piles are driven deep into the ground to achieve adequate foundation for long-span culvert, then the bearing capacity is sufficient, but the installation time and cost increase significantly
Solution Approach 1:
By segmenting the culvert into two three-sided sections, the patent enables the use of simpler, shorter pile foundations or direct placement on prepared ground. The segmented design distributes loads more favorably, reducing the need for deep pile foundations that would be required for a single large-span four-sided culvert, thereby significantly reducing installation time and cost.
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
Enables spans up to 60 feet or more while minimizing soil bearing requirements and simplifying installation, making it suitable for varied site conditions and reducing logistical challenges.
Implementation Method 1
a pre-stressed top slab of the three-sided culvert top section and a pre-stressed bottom slab of the three-sided culvert bottom section
Implementation Method 2
The first and the second sidewalls each include a free end that has at least one male or female connector. The pre-stressed concrete box culvert further includes a three-sided culvert bottom section having a pre-stressed bottom slab and a third sidewall and a fourth sidewall
Data Source
AI summary
A pre-stressed concrete box culvert includes a three-sided culvert top section having a pre-stressed top slab, a first sidewall and a second sidewall. The first and the second sidewalls extend orthogonally from opposite ends of the pre-stressed top slab, and the first and the second sidewalls each include a free end that has at least one male or female connector. The pre-stressed concrete box culvert includes a three-sided culvert bottom section having a pre-stressed bottom slab and a third sidewall and a fourth sidewall. The third and the fourth sidewalls extend orthogonally from opposite ends of the pre-stressed bottom slab, and the third and the fourth sidewalls each include a free end that has at least one male or female connector to mate with the at least one corresponding male or female connector arranged at one of the respective free ends of the first and the second sidewalls.