Weld Metal Tests Stir Steel Building Concerns

Obscured beneath eye-pleasing finishings, the material is a weld metal that fuses thick beams, columns and plates of structural steel. Walk through most any steel building from San Diego to Seattle and it surrounds you.

For more than 20 years, builders have used the weld metal, known as "120" or "E70T-4," with confidence. The assumption has been that the welds help make the steel structures flexible and sturdy enough to withstand even a major earthquake.

But an array of university test results--the first of which were shared with steel construction insiders within months of the January 1994 Northridge earthquake--show the assumptions were based on a faulty premise:

Welds made with E70T-4, it turns out, are not capable of performing as had been expected.

Leading researchers now say that the West's most widely used weld metal is so prone to brittle fracturing that it should be banned from structural uses. Their tests show that E70T-4 has just one-fourth the resistance to fracturing of other available materials.

Consistent with its performance in the Northridge earthquake--when thick, welded connections of steel fractured--the metal has failed in laboratory tests at stress levels far below what would be expected in a major seismic event.

"You should never use this kind of material," said John W. Fisher, a professor of civil engineering at Lehigh University, in Bethlehem, Pa., whose research has been supported by grants from the federal government and by the steel industry. "We should ban its use . . . I think that there's great risk that it's going to cause fracture."

Michael D. Engelhardt, an engineer at the University of Texas at Austin, confirmed in May 1994 that the weld metal fractured under only moderate stress.

"There's just a consistent picture here of real poor performance," he said in an interview. ". . . we now realize how important it is to have high-toughness weld metal in these connections . . . once you see it, it's fairly obvious."

Yet what appears obvious on campus has not gained easy acceptance elsewhere. With the encouragement of the leading distributor of E70T-4, authorities have proved reluctant to prohibit the material.

L.A. Bans Material

Building officials in Los Angeles finally banned use of E70T-4 and other metals with low fracture resistance in July for new construction. And the distributor, Lincoln Electric Co., began advising customers as of June that weld metals it sells with higher resistance than E70T-4 "should be considered" for "seismic applications."

But E70T-4 remains legal to use elsewhere in California and throughout the earthquake-prone West. Even in Los Angeles, officials have no plan to force the retrofitting of the hundreds of buildings that are believed to be dependent on the fracture-prone weld material. Most of these structures, well away from the Northridge epicenter, have not been subjected to mandatory, quake-related inspections.

Richard Holguin, chief of the city's engineering bureau, said he is now convinced that E70T-4 "fractures very, very abruptly."

The city's new policy bars the use of E70T-4 and other fracture-prone metals in major connections. The materials were earlier banned for use in earthquake repairs.

Citing the costs involved, Holguin said it would be impractical to require buttressing of the connections welded with E70T-4 that were not necessarily damaged by the earthquake. Holguin said he assumes most of the 1,500 steel structures in the city have been welded with E70T-4.

At Lincoln Electric, representatives said the Cleveland-based company has acted responsibly and has sought only fair treatment of its entire "Innershield" line of welding metals, including E70T-4. They said that further research is still needed to determine the extent to which the weld metal itself, or other factors, caused damage to the connections.

"There is still not a unanimous opinion within the engineering community," said the company's welding design engineer, Duane K. Miller, adding: "Until it's better defined, we're accepting the fact that [new] requirements should be adhered to."

Quick Application

Because E70T-4 can be applied faster and at higher volumes than other available weld metals, major steel fabrication firms have preferred using it. The weld metals that are more fracture-resistant are not as conducive to rapid production, due to their narrower diameters and the lower temperatures at which they are applied.

An executive of Herrick Corp.--the West's largest fabricator of steel--acknowledged that E70T-4 has been the firm's material of choice for the past 15 years.

This fast, "high deposition" welding metal lowers costs by boosting welders' productivity--a crucial consideration for fabricators and for building owners.