Advertisement

Experts' Tests Uncover Coliseum Weld Defects

Safety: Repairs will be needed if further study confirms flaws, specialists say in report to be presented today.

July 03, 1996|DAVID WILLMAN | TIMES STAFF WRITER

Specialists retained by the Los Angeles Coliseum Commission to examine the stadium's new overhanging press box have found a number of defective welds that they say will require repair if further investigation confirms the abnormalities.

The specialists' findings and recommendations are to be presented publicly today at a meeting of the commission. The examination was ordered after a May 5 Times article disclosed numerous welding problems that occurred during construction of the press box last year.

The testing and engineering documents released late Tuesday by the commission do not indicate how quickly additional testing will be done, or who would pay for repairs--contractors or taxpayers.

According to the findings, abnormalities were identified in 12 of 47--or 26%--of the welded connections that were tested.

"This is a far cry from the clean bill of health that was given to this press box at the [May 8] Coliseum Commission meeting," said County Supervisor Zev Yaroslavsky, who is a commission member.

Yaroslavsky said he wants the engineer responsible for the construction of the press box, who also drafted the report assessing the weld defects, to answer questions at today's meeting. The press box is suspended over hundreds of spectator seats at midfield.

According to the new testing documentation, many of the defects were found in so-called wing plates, which are critical connection points for the cantilevered press box. The Times reported in May that repeated problems were experienced during a San Bernardino welding shop's fabrication of the plates.

Nabih Youssef, the structural engineer whose firm designed and oversaw the construction, could not be reached for comment Tuesday night.

In a sparely worded report, Youssef's firm said that flaws were found in six of the press box's 21 wing plate connections.

The report shows that the recent testing omitted some other crucial welds:

Only 18 of the 44 welded connections that attach horizontal beams to vertical columns were tested, with one abnormality found. Just eight of the 14 so-called web cover plates were tested--and weld flaws were found in five of those locations.

The report's narrative makes no mention of three of the press box's vertical steel columns that were rejected by construction inspectors last year because of defects, but later accepted without an engineer's recommended repair being made. The repair was recommended by Youssef's firm--but the recommendation was not shared with the inspectors who oversaw the fabrication of the columns, according to inspectors quoted in a Times article last Friday.

In its report to be formally unveiled today, Youssef's firm defends the adequacy of its own design and states that the size of any of the imperfections is less than 1% of the total size of the weld.

The engineers, however, recommended that core samples be taken of welds identified as defective by the recent ultrasound testing, "to further confirm the exact nature of the imperfections."

If the examination of the core samples upholds the accuracy of the ultrasound findings, Youssef's firm said it recommends "appropriate measures" be taken to "assure compliance" with original contract requirements.

That point was expanded upon in a companion "peer review" by another Los Angeles structural engineer retained by the commission, John A. Martin Jr. In a 10-paragraph memorandum, Martin endorsed the Youssef firm's recommendations.

"We recommend that all rejectable weld imperfections, if [confirmed by the subsequent core samplings], be repaired . . . or mitigated in a manner that is acceptable to the structural engineer of record and the city of Los Angeles Building Department," Martin wrote.

Martin has not returned calls placed to his office over the past several days.

Neither the Martin nor the Youssef firm's report describes what the anomalies are, except to say that the recent ultrasound testing did not find cracks in the welds.

In an earlier interview, Youssef said that the weld defects could be "inclusions" of slag. Some of the flaws, he said, also could be incomplete fusion between the weld material and adjoining steel surfaces.

Either defect can be structurally significant. Slag inclusions, according to experts, can provide starting points for cracks. A lack of fusion also could undermine performance in an earthquake.

After publication of the May 5 Times article, the city building department verified that Youssef's firm had not certified that the press box was built in conformance with design. The city has since allowed use of the structure on an "event by event" basis.

The Youssef firm did not directly state an opinion on the overall safety of the structure in its report, which is dated June 27. Martin, in his brief review, said he saw no danger.

"We do not have any concerns for the physical safety of the structure," Martin said.

Advertisement
Los Angeles Times Articles
|
|
|