If the floor is supported at or near the bottom but top chords of a bridge is not braced, then the bridge is called

Solution(By Examveda Team)

In the design of steel bridges, the term "through type" refers to a bridge where the floor is supported at or near the bottom, but the top chords of the bridge are not braced. In other words, the traffic or load-carrying portion of the bridge passes through the structure formed by the trusses or girders without any obstruction or bracing at the top.

This configuration provides an unobstructed path for traffic, allowing vehicles to pass through the bridge without any interference from structural members above. Through-type bridges are commonly used for spanning longer distances, such as over rivers or valleys, where a clear span is desirable to accommodate navigation or other considerations.

Options A, C, and D are incorrect because:
Option A: "Deck type" bridges have their traffic-carrying surface (deck) placed on top of, and typically supported by, the main girders or trusses of the bridge.
Option C: "Half through type" bridges have characteristics that are intermediate between through-type and deck-type bridges, with the floor supported at or near the bottom and partial bracing at the top.
Option D: "Double deck type" bridges have two levels of traffic-carrying surfaces, one above the other, with each level typically supported by its own set of girders or trusses.

Therefore, the correct type of bridge described in the question is Option B: Through type.