Angle skew, or skew angle, is a fundamental concept in bridge design and structural engineering.
The term angle of skew or skew angle is fundamentally the angle between a normal/perpendicular to the alignment/centerline of the bridge and the centerline of the pier.
Understanding Skew Angle
To fully grasp what skew angle means, let's break down the components:
- Bridge Alignment/Centerline: This is the main direction or path that the bridge follows.
- Normal/Perpendicular to the Bridge Alignment: Imagine a line drawn straight across the bridge's path at a 90-degree angle. This is the perpendicular line.
- Pier Centerline: This is the main direction or path that the bridge pier (the vertical support) follows.
The skew angle is the measurement of how much the pier's centerline deviates from being perfectly perpendicular to the bridge's direction.
Why Skew Matters
When a bridge crosses an obstacle (like a river, road, or railway) at an angle other than 90 degrees, its supports (like piers or abutments) often need to be built at an angle to match the obstruction or site constraints. This angle is where skew comes into play.
- A bridge with supports perfectly perpendicular to its alignment has a skew angle of 0 degrees.
- A bridge with supports built at an angle to the perpendicular line has a skew angle greater than 0 degrees.
Skew Angle on Straight Bridges
As the provided reference notes: "on a straight bridge, the skew angle at all supports would normally be the same and the term skew angle can be applied to the bridge as a whole." This means for a bridge that doesn't curve, the angle between the pier and the perpendicular line is consistent along its length, allowing the entire structure to be described as having a specific skew angle.
Key Aspects of Skew Angle
- Measurement: Measured in degrees.
- Location: Typically refers to the angle at the bridge supports (piers and abutments).
- Impact: Influences structural design, load distribution, deck geometry, and construction complexity.
Understanding angle skew is crucial in bridge design to ensure structural integrity, proper drainage, and efficient use of materials, while also accommodating site-specific conditions like the angle at which the bridge crosses a feature.
