Advantages of arch bridges:

• Inexpensive, with local building materials such as stone and brick being used in the past. Today concrete is more likely to be used.
• Wider distances can be spanned by building more arches.

Disadvantages of arch bridges:

• Uses a lot of material, even on short spans

ARCH SYSTEM

Ancient arch bridges date back to Etruscan and Roman times. Arch Bridges are some of the oldest bridges in our region of Southeastern Pennsylvania dating to the 1700's and 1800's.

They have great natural strength and are built so that the weight of the bridge is pushed out through the arches to the supports at the end. The supports are called abutments. They carry the weight of the bridge and keep the ends of the bridge from spreading out.

Materials used:

Most older arch bridges in our school district are from the late 1800's and early 1900's and are made of stone and cement. The most common materials used today in the making of arch bridges is steel and pre-stressed concrete; these materials allow the builder to make long elegant arches.

Constructing:

The constructing of arch bridges can be tricky because the structure is completely unstable until the two arches meet in the middle. Traditionally, the workers built a scaffolding or "centering" below the spans to support the two sides until they meet.

One of the newer methods is to support the spans by cables anchored on both sides of the bridge. This method sometimes helps the builders without disrupting traffic or people in areas where there is water or a road underneath. The place where the stone from the arch touches the ground can either be in the water or on a pier. Most of the time arch bridges are on piers.

Tohickon Bridge (next to Stover-Myers Mill) - between Bedminster and Tinicum Townships

Stream: Tohickon Creek

Built: 1906

This narrow bridge is located on the edge of our school district.		Note the buttresses on the side of the bridge.

Township Bridge - East Rockhill Road - East Rockhill, PA

Built: 1901

This bridge is a double arch bridge typical of many arch bridges found on country roads in our area over minor streams.		Note the machined stone voussoirs (wedge shaped pieces) that form the arch and the irregular field stones used for the majority of the bridge.

Without looking at the materials that this bridge is made of, due to its width, one can tell that it was made for less traffic in earlier times.		This bridge is a triple arch bridge made of stone.
Evidence of recent repairs in 2000 can be seen with the new cement on the tops and sides of the bridge.		This bridge had been damaged from flood debris.