Welded Wire Mesh - Reinforcing India
By Mahendra Mukim Ji
Weldmesh Reinforcement – Introduction
Welded Wire Fabric (WWF), commonly Welded Mesh, is a prefabricated reinforcement consisting of parallel series of wires having a very high yield (Fe-480). The wires are cold drawn or cold-rolled, welded together in square or rectangular grids. Each wire intersection is electrically resistant – welded continuously by an automatic welding machine. Welded Wire Mesh is bonded to concrete by a positive mechanical anchorage at each intersection.
Benefits of Welded Wire Fabric:
I. Controlled Manufacture Weldmesh is manufactured from hard drawn steel wire and thus has a tensile strength not less than 580 N/mm2 while the tar steel used in traditional construction maybe as low as 250 N/mm2
II. Proper Distribution of Steel Weldmesh provides equal distribution of steel reinforcement within the concrete slabs, affecting the strength. The number of small diameter wires spread across the cross section help in arranging the concrete slabs according to the specification.
III. Better Anchorage/Bond Since the HYSD bars are tied with barbed wire at the intersection, they tend to be loose and shifty whereas a weldmesh sheet is strong in its intersection and rarely falls apart.
IV. Better Crack Resistance
o Research into crack width and the width prediction formulae adopted by the building cost show the maximum widths are propotional to the distance from the surface to the closest reinforcement i.e. to bar spacing and concrete cover and the inter reinforcement spacing.
o Weldmesh is much superior in restricting the crack width to acceptable limits in concrete slabs because of smaller diameter of wire used, closer and with uniform spacing.
o Thinner wire with closer spacing is efficient in ensuring more homogenous 2-way stress distribution throughout the concrete volume thereby controlling crack propagation as well as the crack width.
V. Easily Handled and Placed Being welded automatically at joints, little labor is required for placing and fixing. When properly supported it remains fixated in its position during concretization.
VI. Adaptable For Forming And Shaping Weldmesh possesses the right degree of ductility to allow it to be bent, shaped or fashioned readily on the job, yet it is sufficiently rigid to maintain its shape after bending.
VII. Higher Characteristic Strength Use of Weldmesh with Fe-480 grade results in savings in steel area or steel weight required to the tune of 15% vis-à-vis HYSD bars of Fe-415 grade and to the tune of 47.92% vis-a-visplain mild steel bars of Fe-250 grade.
Buiilding Codes: For Welded Wire Mesh in Reinforcement
IS:4948-1974 (Re-affirmed 1992)
This standard covers Welded Wire Mesh for the general use, such as fencing, window grill crates and other such uses for the concrete reinforcement. The chemical composition of the steel wire to be used for the manufacture of Welded Wire Mesh shall conform to S:226 – – 1969
IS:1556-1982 (Re-affirmed 1989)
This standard covers the requirement for hard-drawn Steel fabric consisting
of Hard – drawn steel wire with cross-wires electrically welded to them for use as a concrete reinforcement.
The wires used in the manufacture of weldmesh shall be hard-drawn steel wire conforming in all respect, to the requirements of IS:432 (Part II) – 1982 and suitable for welding.