Shimizu Construction Co., Ltd., under the leadership of President Kazuyuki Inoue, jointly with Gifu Kogyo Co., Ltd., has developed the floor slab renewal method "Graving Erector Method" to efficiently remove the detached aged viaduct floor slabs and install new floor slabs in one device, aiming to improve the productivity of urgent high-speed highway renewal construction projects. The core of this method, the floor slab renewal device, is self-propelled. It moves to the designated construction site, repeating the process of removing the existing floor slabs and installing new ones. Going forward, the device's functionality will be demonstrated and deployed to viaduct floor renewal sites.

The development of Japan's expressway network began during the period of high economic growth. While various regions have been connected by expressway networks, over the years, road deterioration has progressed, and now, construction orders for renovations are intensifying throughout the country. In urban areas with heavy traffic, renovations are planned using the "half-section construction" method, where one side of the road is closed to general traffic to reduce the load on vehicles. The Graving Erector Method was developed to target the renewal projects of viaduct floor slabs where half-section construction is performed.

The floor slab renewal device consists of an H-shaped steel frame section and a floor slab gripping mechanism that removes existing floor slabs and installs new ones. The frame section is constructed with two 19m running frames, two 4m transverse members connecting the frame ends, and six 4m height adjustable columns with stretching and running functions. The floor slab gripping mechanism consists of a driving unit (grip carriage) traveling on the running frame, a gripping device extending from the driving unit to the floor slab surface, and each gripping device is composed of a base floor slab installation device and a detachable detachment device. The gripping method for the floor slab is bolted joints. Bolt holes are provided during manufacturing for new floor slabs, while workers punch bolt holes in the old floor slabs, and during removal / installation of the floor slab, workers bolt the floor slab to the gripping device.

The size of the new floor slabs varies depending on the construction conditions, but generally ranges from 5-6m in width, 2-2.5m in depth, and weighs 8-10 tons per piece. The floor slab renewal device is installed to cover the installation locations of five new floor slabs, after removing the pre-cut members of the existing floor slabs. It then moves to the next location after installing one new slab at a time, totaling five slabs. The device can move forward, backward, left, and right in the direction of the road, and can be moved to any location on-site. The gripping device is controlled in three dimensions, ensuring that the held floor slab does not sway and allowing precise alignment during floor slab installation without manual intervention, thereby improving work safety.

The number of floor slab replacements planned per day using the Graving Erector Method is five slabs. In the future, our company will base bids for high-speed highway viaduct floor renewal projects on this method and strive to secure contracts. Furthermore, in the joint development, Gifu Kogyo Co., Ltd. served as the base for the floor slab gripping and installation mechanism, setting the standards and specifications for the device.