reprinted from Engineering News-Record, Feb. 20, 1995
Doug Copp crawled through 50 buildings during a rescue mission and assessed the
work awaiting the Japanese. But reconstruction is temporarily on hold.
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In the heat of a debate on the adequacy of Japan's construction codes, the
City of Kobe has halted replacement work on buildings taller than two stories
that were damaged in the area's Jan. 17 earthquake. The two-month-minimum moratorium
will give a 28-member multidisciplinary committee time to consider the best
ways to construct or reconstruct permanent structures. Meanwhile, workers are
rushing to erect temporary housing for the 240,000 residents made homeless by
the magnitude 7.2 temblor.
Regarding the moratorium, "it is important to take this opportunity to
upgrade the level of city planning," says a spokesman for the city's disaster
office. National government bodies, too, have formed groups to study earthquake
countermeasures.
Already, there are big differences of opinion about whether building codes
need attention. "There is a gap [in understanding] between engineers and
ordinary people," says Shunsuke Otani, a University of Tokyo architectural
engineering professor.
That gap extends to the government. Tokyo Metropolitan Government officials
have announced they are going to consider stricter regulations for structures.
The Ministry of Construction has set up a panel to recommend building code changes.
And Transport Minister Shizuka Kamei said recently that railway and port facilities
should be made quake-resistant at any cost.
Dramatic difference: Workers have finished clearing the stretch of
the Hanshin Expressway that had tipped over.
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But engineers disagree, pointing to recent damage surveys. For example, Osaka-based
Obayashi Corp. checked 223 major buildings it built in the area. Of those completed
before key code changes took effect in 1971, 36% were judged unsafe to enter
due to quake damage. For buildings built from 1971 to 1980, a year before another
round of code changes, 11% were too badly damaged to enter. But of the newer
buildings built to the current code, only 6% were judged dangerous.
Surveys by other construction companies and such organizations as the Architectural
Institute of Japan corroborate Obayashi's findings. So while public officials
are going in one direction, engineers are concluding that while detailed studies
of damage may produce some changes in detailing practices, "it is quite
clear that the upgrading of the codes has [already] resulted in safer structures,"
says Masanobu Shinozuka, professor of civil engineering at Princeton University
who also heads a Tokyo-based seismic risk consulting firm.
Performed. Makoto Watabe, a senior director of Shimizu Corp., Tokyo,
adds that even those post-198l buildings that were damaged performed as designed,
sustaining unusually strong shaking without collapsing.
The philosophy in Japan and in the U.S. is to design buildings to withstand
smaller frequent quakes without damage. But it would be economically unreasonable
to design all buildings for the level of quake that might occur only once in
500 years, say engineers. Instead, the intent is for buildings to remain standing
in order to protect human life. "I think that purpose was largely fulfilled
[in Kobe]," Watabe maintains.
One example of a 15-year-old complex that survived standing but not unscathed
is Ashiyama Seaside Village, just outside Kobe. Reports indicate that 21 of
52 residential high-rises were damaged. And though, on a recent site visit,
a group of American engineers noted scaffolding on several buildings, the complex,
with its exposed steel framing, is still inhabited.
There, the basic framing is a system of supertrusses, oriented horizontally
and vertically. The supertruss is formed from top and bottom-chord "box
columns" connected by diagonals. It appears that the quake cracked open
the box column faces at lower levels.
Truss buildings are damaged but habitable. |
Clear. On other fronts, downed sections of the Hanshin Expressway are
cleared, and electricity, telephone and most water service is restored. But
70% of gas customers are without service. Also, only 2,000 of an eventual 40,000
temporary prefab housing units are up.
And while local firms are getting most of that work, the Japan office of Chicago-based
Schal Bovis Inc. appears set to win a $10-million-plus contract for 500 prefab
houses, says John Dickison, senior vice president. Douglas F. Copp, a
vice president in the Alameda, Calif., office of Demolition Environment Management
Co., says Americans are unlikely to get other local work. As chief of the volunteer
American Rescue Team that went to Kobe, Copp crawled inside at least
50 damaged buildings. So he knows first-hand how much there is left to do.
By Dennis Normile with David B. Rosenbaum in Kobe
