Two 32-ton "skywalks" that collapsed and killed 113 at the Kansas City Hyatt Regency Hotel in July violated city building codes and barely supported their own weight, a government study concluded yesterday.

The National Bureau of Standards said its investigation of the tragedy determined that a change in the original design of the walkways during construction compounded the problem, but that even the original design would have provided for a load tolerance less than that required by city building codes.

Two of the three hotel walkways, all suspended by steel rods that hung from beams in the hotel ceiling, collapsed July 17 during one of the hotel's popular "tea dances." Investigators said the fourth-floor walkway, loaded with dancers, gave way when the hanging rods pulled through box beams in the walkway's bottom, then fell on the second-floor walkway, causing both to plunge to the floor.

The report said that a decision during construction to change the design "further aggravated an already critical situation." The original design had both walkways suspended from the hotel roof by a common set of rods. The design change had the fourth-floor walkway suspended by one set of rods and the second-floor walkway suspended from the walkway above it by another set.

The design change left the walkways capable of bearing only 21,400 pounds, rather than the 68,000 pounds required under the building code, according to the report.

The support structure thus had "barely enough capacity" to support the weight of the walkway, "and very little additional capacity to resist the loads imposed by people," said Edward Pfrang, who headed the investigation.

The investigation did not assess responsibility for the insufficient load capacity, but its findings are expected to be used in billions of dollars in pending lawsuits.

Mayor Richard L. Berkley said in Kansas City that the report "does clearly point out that these things did not live up to the building code, and that's a very serious matter."

The accident, which also injured at least 212, forced engineers and architects across the nation to review the safety of similar designs.

The report said neither dancing nor defects in materials were to blame. "Neither the quality of workmanship nor the materials used in the walkway system played a significant role in initiating the collapse," it said.

Researchers simulated collapses and subjected debris from the walkways to hundreds of tests in the investigation.

"The change in hanger rod arrangement from a continuous rod to interrupted rods essentially doubled the load to be transferred by the fourth-floor box-beam hanger rod connections," the report said.

Pfrang said that while the original design "provided a capacity far below the capacity that would have been required" to satisfy the building code, "it would have comfortably supported what we estimated to have been on it at the time of the collapse."

Kansas City, which is expecting a report on the performance of its public works department in mid-March, has been requiring biweekly reports on design changes from builders of structures of "exotic design." But some builders complain that the reports are unnecessary and increase construction costs.

"I don't think that's the proper role of the city, to see that an architect does his homework properly," builder Jim Senter said. "You'd have the entire City Hall filled with people checking designs."