Pre-stressed Box Culvert Segmentation for Long Spans
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional concrete box culverts face limitations in span length and logistical challenges due to high bending moments and soil bearing capacity issues, particularly in applications requiring larger spans or angled installations, which increase costs and complexity.
Innovation Solution
The design of a pre-stressed concrete box culvert with a parallelogram-shaped top slab and orthogonal sidewalls, featuring male and female connectors and post-tensioning ducts, allows for increased span lengths and flexible installation configurations, including angled or curved arrangements, by dividing the culvert into three-sided sections for easier assembly and transportation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the span of a three-sided box culvert is increased beyond 35 feet, then the bending moment in the top slab becomes prohibitively large, but the maximum span is limited to 30-35 feet
Solution Approach 1:
The culvert is divided into multiple precast segments that are assembled in the field. Each segment has a manageable span (30-35 feet) while the overall structure achieves longer spans. The segments are connected using coupling members that transfer loads between segments, effectively distributing the bending moment across multiple shorter spans rather than one long span.
2Strength
If a four-sided box culvert with large span (40 feet) is used to spread load across the bottom slab, then soil bearing capacity requirements are reduced, but fabrication, transportation, and installation become logistically challenging
Solution Approach 1:
The four-sided box culvert is segmented into multiple smaller precast units that can be fabricated and transported using standard equipment. These segments are assembled in the field to form the complete long-span structure. The coupling members connect the segments both longitudinally and laterally, creating a rigid frame that distributes loads across the bottom slab while maintaining manufacturability and transportability of individual segments.
3Length of stationary object
If the design height of the box culvert is increased to 10 feet or more for large span applications, then the span capability is improved, but fabrication and transportation difficulties increase
Solution Approach 1:
The high culvert structure is divided into segments with reduced heights that are easier to fabricate and transport. Each segment maintains the necessary structural depth for its local span requirements but is small enough to be handled by standard equipment. The coupling members and inter-segment connections restore the overall structural integrity and achieve the desired total height and span when segments are assembled in the field.
4Adaptability or versatility
If the span of culvert segments is increased to accommodate angled installations, then the ability to intersect rivers or roadways at angles is improved, but the cost and complexity increase
Solution Approach 1:
The culvert is constructed from multiple standard-angle segments (e.g., 30-degree or 45-degree angles from perpendicular) that can be assembled to create various overall configurations including angled and curved alignments. This modular approach allows flexible adaptation to different site conditions and intersection angles while maintaining standardized segment dimensions and fabrication processes, thereby controlling cost and complexity.
Solution Approach 2:
Instead of creating custom angled segments, the design uses segments with standard angles that can be arranged in different spatial configurations. By changing the arrangement and orientation of segments in the horizontal plane, the culvert can accommodate various intersection angles with rivers or roadways without requiring custom fabrication for each angle, thus reducing complexity 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
This solution enables spans up to 60 feet or more, reduces fabrication and transportation difficulties, and accommodates varied site conditions, including low-bearing capacity soils and angled installations, while maintaining structural integrity and cost-effectiveness.
Implementation Method 1
The pre-stressed top slab has a first plurality of steel tendons extending between the first end and the second end thereby imparting a compressive force to the pre-stressed top slab
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.