Resilient Bridge Column Inspired by Limbs

Innovation: Academia

Texas A&M University

2020

Image: ID 995645 / Pixabay / CC BY - Creative Commons Attribution alone

Prevent Buckling

When a living system undergoes compression to the extent that it causes structural damage, it results in buckling. For example, if a person pushes down on the top or the side of a paper cup, the cup’s wall will eventually give way, or buckle. Although a living system could add material to strengthen a structure, this requires expending precious energy. Instead, it must use energy and materials conservatively to avoid buckling, strengthening structures through careful placement of materials to resist, absorb, or deflect compressive forces. For example, instead of one long, tubular stem, some plants like bamboo have stronger nodes scattered along their stems. When compressed, these nodes keep the round stems from taking on an oval shape that weakens the structure and could result in buckling.

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Prevent Deformation

When a living system undergoes compression, tension, shear, bending, or twisting, its internal inter-molecular forces can often resist these forces and even change shape temporarily, returning to the original shape when the forces stop. However, if the force is too strong or lasts too long, permanent deformation or structural failure can occur, resulting in death. Therefore, living systems have strategies to resist deformation or help ensure limited deformation. For example, bones have thin crystals and proteinaceous fibers that provide strength and flexibility, protecting them from forces that would otherwise cause deformation on a daily basis.

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Prevent Fracture/Rupture

High force impact or stress can cause materials that comprise living systems to separate into two or more pieces (called fracturing) or to break or burst suddenly (called rupturing). For example, a scallop prevents structural failure from fracture because its shell is comprised of two materials of varying stiffness. When a crack moves from the scallop’s stiff material to the less stiff one, the latter reduces the force at the tip of the crack, thereby stopping it from spreading farther.

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The hybrid sliding-rocking bridge from Texas A&M University has flexible joints that help reduce impact and damage to the overall structure.

Benefits

Sustainable
Resilient
Increased performance

Applications

Bridge design
Building design

UN Sustainable Development Goals Addressed

Goal 9: Industry Innovation & Infrastructure

The Challenge

Bridges are oftentimes made of concrete- a stiff, hard, inflexible material. When an earthquake or other natural disaster hits, the components may be forced to move, but because they are unable to, the structure ends up cracking and breaking. If structural damage occurs, the repairs can be costly, or could lead to catastrophic failure of the overall structure.

Innovation Details

The hybrid sliding-rocking bridge is made of columns with joints and segments inspired by limbs. The column is made of precast concrete with steel rebar inside. The steel is post-tensioned, a method where lengthened steel cables are placed before the concrete is poured. The column is connected to the rest of the structure with rocking and sliding joints. In the event of a major catastrophe such as an earthquake, the joints absorb some of the energy while the segments slide over one another, rather than bending or cracking. The columns exhibited little damage when exposed to high-intensity shock similar to what would be delivered by earthquakes, and the damage that did occur could be repaired quickly with grout and carbon fibers.

Biological Model

A joint is where two bones meet in the body. Different joints allow for different types of movement. Cartilaginous joints are connected by cartilage, and allow for small types of movement, for example the vertebrae in the spine. Synovial joints are more freely moving and can move in many directions, such as hip or shoulder joints. These joints are filled with fluid that acts like a lubricant, helping the joints to move more easily.

See Related Strategy

Biological Strategy

Shoulder Joint Manages Stress

Humans

Rotator cuff in humans manages force via an extra pliable region

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