Concrete bridge beams

Concrete Bridge Beams

Welded Wire Reinforcement is used in more applications for beam stirrups in bridge beams every day. Where repetitious use of small rebar can be expensive to place, and tight tolerances difficult to maintain, WWR stirrups can save both time and money. A natural solution to the problem of placing steel in congested areas, WWR by Ivy Steel & Wire incorporates large wire sizes to replace # 5 and # 6 rebar and can space them at virtually any dimension to satisfy the steel requirements.

Most of the stirrups are bent on a mesh bender before being placed in the beam forms. The mesh bender is capable of bending a sheet of mesh with many individual wires. Each wire is bent at the same time with exactly the same bend.

The consistency of the bending operation allows these stirrups to meet tight tolerance requirements. Bending can be done at the mesh plant and shipped to the precast plant or the job site. Another method is to have the bender in the precaster’s plant or at the job site. This eliminates the risk of damage during shipping and reduces the amount of storage space required.

The design of stirrups is usually a U-Shaped sheet with the vertical steel on each face of the beam providing the required steel for the shear requirements. The longitudinal steel in the U-Shaped stirrup is not required to be lapped, and consists of two wires on each leg at the open end at least two inches apart for anchorage. In addition there is usually a minimum of two wires near the upper part of the stirrup to support additional steel.

When the web is too narrow, the mesh stirrups are made of two individual sheets instead of one U- Shaped sheet.

Box beams for railroad bridges or highways can be fabricated in much less time and with tighter placing tolerances using WWR stirrups. Prestressing lines can be turned faster and thus money saved, due to the speed of placing bent sheets of stirrups compared to tying individual rebar.

Box beams of rectangular, trapezoidal or U-Shaped configuration may have their stirrups consisting of two or more pieces of mesh that are assembled to form a closed shape.

The design of the stirrups account for the greater amount of vertical steel required at the end of the beam. These sheets of WWR are usually made in lengths of four to eight feet and called End Pieces. There is very little waste involved in this method regardless of the lengths of the beams because the longitudinal wires do not have to lap. You simply cut the small longitudinal wires giving you the proper size piece to fill out the beam and use the remainder of the piece in the next beam.