What is a bascule type bridge?

Bascule bridges have spans that pivot upward utilizing gears, motors and counterweights. Unlike vertical lift bridges, when opened, there is no vertical obstacle to river traffic. The Broadway Bridge is an important example of a Rall-type, double-leaf bascule bridge.

What is a bascule bridge used for?

A bascule bridge (also referred to as a drawbridge or a lifting bridge) is a moveable bridge with a counterweight that continuously balances a span, or leaf, throughout its upward swing to provide clearance for boat traffic. It may be single- or double-leafed.

What is a trunnion bridge?

A trunnion is the axle at the top of each tower of the Interstate Bridge that supports the weight of the bridge and counterweights to help raise and lower the lift span. One of the reasons is that a lower river = more “headroom” for ships to fit under the bridge while we replace the bridge lift system.

What are the parts of a bascule bridge?

Besides the leaves and the counterweights, the other primary elements of a bascule bridge are the trunnion and the lift mechanism.

What are the disadvantages of bascule bridge?

Disadvantages of Bascule Bridge

  • Bascule bridge is subjected to considerable wind load especially when it is opened.
  • The machinery used to control bascule bridge should be crucially strong and robust compared to the case where wind load is not present.

What is the advantage of a draw bridge?

The bridge’s structure changes the flow of water into a direct current and can provide a great spawning location. There aren’t many positive environmental impacts, but drawbridges allow for a bridge that has minimal impact on bodies of water.

What is bridge freeboard?

Bridge freeboard is the clearance between the lower limit of the bridge superstructure or the bottom of the culvert top slab and the Freeboard High Water surface elevation. An appropriate amount of freeboard allows for the safe passage of ice and debris through the structure (not typically required for culverts).

What holds up a bridge?

Pile: A pile is a vertical support structure that’s used, in part, to hold up a bridge. It can be made of wood, concrete, or steel. Superstructure: The superstructure is the part of the bridge that absorbs the live load. (The abutment, piers, and other support elements are referred to as the substructure.)

How long is the bascule bridge?

1 Bascule bridge. The free span of 80 m and a total width of 42 m render the bascule bridge the world’s largest (Figure 17.24 and 17.25). The total length of the flaps (54.5 m each) is divided by the axis of rotation into two cantilevers of 42.8 m and 11.7 m.

What kind of bridge is a bascule bridge?

This animation shows the movement of a double-leaf bascule. A bascule bridge (sometimes referred to as a drawbridge) is a moveable bridge with a counterweight that continuously balances a span, or “leaf”, throughout its upward swing to provide clearance for boat traffic. It may be single- or double-leafed.

Where are counterweights located on a bascule bridge?

There are three types of bascule bridge designs, and counterweights required to balance a bascule’s span may be located either above or below the bridge deck. The fixed-trunnion (sometimes a “Chicago” bascule) rotates around a large axle that raises the span(s).

What kind of bridge is a Parker truss?

The design was well suited to a variety of highway bridge applications and was very popular until about 1930. A Parker truss is a Pratt truss with a polygonal top chord.

How are the arms of a cantilever bridge different?

Many cantilever spans have cantilever arms that, rather than extending all the way to meet an opposing cantilever arm, stop short of the center so as to hold a suspended span in place. Bridge arrangements refer to the position of the deck (roadway) relative to the superstructure of the bridge. Not all bridge types make use of this nomenclature.