Engineering the Olympics: Pole Vault

Much research is dedicated to enhancing Olympic athletic performance. Understanding equipment behavior can lead to product improvements that will also help improve overall performance.

Pole vaulting is a fascinating sport owing to the discipline and prowess of the athlete and the structural behavior of the pole: both are essential for success. From an engineering standpoint, the kinetic energy, generated by the speed of the vaulter, is stored by the pole and released in the form of potential energy. This helps the vaulter convert his momentum to the required height to clear the bar.

The pole is storing and releasing energy. When coupled with the vaulter's skill level, you have the two primary elements involved in performance.

Some of the pole characteristics essential in determining its ability to store energy are its mass, flex number, height rating, and material. The flex number is a measure of pole deflection under a standard weight: the higher the flex number, the softer the pole. The vaulter's hand grip, body position, and a number of other factors ultimately determine how well a pole vaulter performs, but the pole matters.

Running a finite element analysis helps us understand how the different pole characteristics affect its ability to store and release energy.

Pole Vault Performance

The performance of the modern pole used for vaulting has significantly improved since the inception of the sport in the mid-1800s. Much of this improvement is associated with the development of various material types. The transition to more pliable materials, such as carbon fiber composites, from rigid materials, such as hardwood and bamboo, enabled increased pole flex that helped propel vaulters to greater heights. It is no coincidence that the development of glass fiber poles in the 1960s coupled with improvements in athleticism led to the dramatic increase in heights cleared after that period.

Poles are usually hollow tubes made of composite materials such as glass-fiber or carbon-fiber reinforced plastic. Composite materials have multiple layers of fiber (reinforcement) and resin (plastic matrix) that give a pole its strong yet light quality.

When these poles flex they undergo various modes of shape change: one side of the pole stretches along its length, and the other side compresses, creating an oval shape. These shape changes could lead to the failure of the pole by either damaging the resin matrix or the fiber in tension or compression. Hence, a big factor in pole design is the material properties of the composite.

For instance, the fiber imparts the tensile strength to the composite, so the plastic resins need to elongate as much as the fiber to take advantage of the fibers' strength. The fibers could also be finely tuned to the balance between stiffness and strength by controlling the quantity and orientation of the fiber in each layer of the composite.

Why 'Nonlinear Dynamic' Analysis

This seemingly complex term can be broken into two words: nonlinear and dynamics. Owing to the linearity of a majority of materials, the way they deform can be studied to a certain degree of accuracy using elasticity constants that aren't affected by

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