Volume 5, Number 1, June 2007
This issue of Panel Update Volume 3 Number 1 marks the beginning of our fifth year of circulating ourbimonthly eNewsletter to share Panel activities with its members. Our June issues highlight the Panel’s
recently conducted technical site visits. These site visits followed the Panel’s three day Technical Meetingsof 14-16 May 2007 in Tsukuba. Proceedings of the Panel on Wind and Seismic Effects will be published in
the fall and circulated to all Panel members and manuscript authors.

HIGHLIGHTS - TECHNICAL SITE VISITS
39TH MEETING OF THE US-JAPAN PANEL ON WINDAND SEISMIC EFFECTS 17-19 MAY 2007
1.
Tokyo Metropolitan Expressway Route
The Metropolitan Expressway Company Limited, a privatized organization in 2005, is responsible fordesign, construction and management of Tokyo’s Metropolitan Expressway. The delegation was briefed oninvestigation and techniques used to repair fatigue cracks in expressway steel bridge piers and orthotropicsteel decks. Fatigue cracks are detected by magnetic particle testing procedure. Of 2011 piers tested, 566
had fatigue cracks. As temporary measure, holes are drilled at each end of the crack to prevent propagationof cracks that allowed traffic flow until permanent repairs. Monitoring is performed following a five year
inspection plan. When visual inspection identifies serious cracks, annual inspections are performed for
those selected fatigue cracks.
Modern Tokyo transportation relies on multiple highways that overlay the extinct canals and waterwaysystems of near the end of the Edo period (1603 – 1868). The delegation visited the Ohashi Junction of theCentral Circular Shinjuku Route under construction designed to allow vehicles to pass through the central
part of Tokyo by avoiding surface traffic congestion. A double loop reinforced concrete spiral ramp system isbeing constructed to connect the underground expressways with elevated highways. Completion of thisCentral Route is expected to reduce about half of the congestion on the expressways and expected tosignificantly reduce carbon dioxide emissions. The construction cost of the junction is $200 million.

Figure 1: Group photo of members of the Panel Delegation at construction site of the Ohashi Junction of theCentral Circular Shinjuku Route, Tokyo Metropolitan Expressway

2.
Seismic Retrofit Project of Lower Murayama-Shimo Reservoir Dam (Tokyo Metropolitan
Government Bureau of Waterworks).
This reservoir along with the nearby Yamaguchi and Murayama-Kami Reservoirs were built between 1916and 1934. The dam for the Murayama-Shimo Reservoir is 587 m long and is an earthfilled dam (33 m high)made by compacting materials such as clay and sand. After the Great Hanshin-Awaji Earthquake in 1995,
the dam was checked for seismic stability. Since heavily populated residential areas are downstream andthe reservoir is able to gravity feed several purification plants, it was determined to be critical to the Tokyoarea. Therefore a detailed seismic study was done and strengthening was determined to be necessary.
The dam consists of a shell, core, bomb shield and a counter weight fill. The strengthening consisted ofadding drainage, reinforcing the counter weight fill with geogrid and covering the crest of the dam with acement-stabilized soil layer. The geogrid prevents sliding of the counter weight. The cover on the crest of
the dam is to prevent failure of the top of dam during overtopping.
As part of the project, the reservoir was drained a minimum level so that strengthening could be done. Aminimum level was maintained in order to sustain local wildlife. The project is to be completed by March2009 at an estimated cost of $90 million.

Cement-stabilized soil

10.0

Existing dam
.5
1:1

15.0

Geogrid

Shell

0
1.

Shell

Core.610
1 3.

Counter- weight fill

1 2

drain
Figure 2: Dam strengthening (Courtesy, Tokyo Metropolitan Government Bureau of Waterworks)

3.
Building Vibration Control System (Obayashi Corporation).
The delegation visited the thirty two story Shinagawa Intercity Tower A. The building is equipped with twounique Hybrid Mass Damper systems designed by the Technical Research Institute of Obayashi
Corporation. The structure is 144.15 m tall with three basements, thirty stories and one penthouse.
The Hybrid Mass Damper (HMD) system is composed of three major components; 1) the Active Mass
Damper (AMD), 2) the Tuned Mass Damper (TMD) and 3) the Multi-Layer Laminated Rubber Bearings. In
this application the HMD is secured above the AMD which is set on the passive mass of the TMD,
supported with the Multi-Layer Laminated Rubber Bearing. The Multi-Layer Laminated Rubber Bearing
has no frictional drag, and thus the TMD can move smoothly from a small external force level. The design
also makes possible shifting smoothly from TMD to HMD according to the response level of the building.
The applied active control systems also make it possible to control multi-vibration modes including torsionalmodes of the building. The 200 ton TMD was tuned to the 1st natural frequency of the building. Methods
were developed that allowed for a smooth transition between dampers based on the response of thebuilding.

Figure 3: Members of the Panel Delegation are inspecting the Hybrid Mass Damper System in theShinagawa Intercity Tower A Building

4.
Karematsuzawa Bridge (Tohoku Regional Development Bureau).
The delegation visited the Karematsuzawa Bridge on the Sanriku National Highway under management ofthe Tohoku Regional Development Bureau near Kamaishi City, Iwate Prefecture. This 310 m long steelarch bridge, one of the longest arch bridges in Japan, was constructed over the gorge to straighten the 15km section of a winding highway on steep topographic conditions. The bridge eliminated 46 sharp curves,and reduced a stretch of highway having a 9.6% grade to a 4% grade. The realigned highway and bridge
significantly reduced vehicle accidents and driving time. The cost of this 15 km highway construction was$700 million.
The bridge’s steel members were fabricated using weathering steel to reduce bridge maintenance. An
issue that may exist is possible environmentally detrimental releases from steel’s surface treatment or its
interaction with adjoining materials. The delegation was briefed on the method (the cable erection method)used to construct the bridge over an 80 m deep gorge.

Figure 4: Overview of the Karematsuzawa Bridge (left) and group photo of members of thePanel Delegation at the site (right)

5.
Kamaishi Port Tsunami Breakwater
The Pacific Ocean coast of Iwate Prefecture in northeast Honshu has a long history of tsunami attacks thathave killed thousands of citizens and destroyed various coastal villages. The delegation visited Kamaishi
Port to discuss the recently completed deep breakwater structure at the mouth of Kamaishi Bay with therepresentatives of the Kamaishi Port Office of the Port and Airport Department of Tohoku RegionalDevelopment Bureau. The planning of the breakwater started in 1978 and was completed in spring 2007.
The breakwater consists of two dikes with a central opening for large ships. The dikes are comprised oftrapezoidal and rectangular caissons. The total length of the breakwater system is 2260 m long. A second
smaller breakwater (seawall) closer to the port harbor deflects remaining waves. The breakwater is thelargest in Japan constructed in 63 m of water (the deepest water site in the world) with a 30 m high caisson
designed with parallel slits to reduce wave force. Its 700 million ton base rock rubble foundation with armorstone layer on the outside face acts as a seismic countermeasure.