Innovating as-built verification

Author: Yoshie Katagiri

In 2018, the Japanese Ministry of Land, Infrastructure and Transport (MLIT) publicly invited bids for a ‘Project to Introduce and Utilise Innovative Technology to Dramatically Improve Productivity on Construction Sites’ under its i-Construction initiative aiming to boost productivity on construction sites as part of a wider innovation strategy. Kanatsu Giken formed a consortium of four companies with Fukui Computer Co., Ltd., Leica Geosystems Co., Ltd., and Sanyo Sokki Co., Ltd., and tendered for the project. The consortium was selected in the category of ‘Techniques Using Data to Improve the Productivity of Construction in Civil Engineering Work.’

The objective of the four-company consortium was to conduct 3D laser scanning on concrete structures, such as bridge abutments and piers, and use the acquired point cloud data for as-built verification to dramatically improve the productivity of construction sites. In addition, they trialled and proposed a new method of progress management using the differences between the captured point cloud data and the coordinate values of the 3D design data (CIM).

Kanatsu Giken used Leica Geosystems’Leica Nova MS60多阶段, an instrument capable of 3D laser scanning with the surveying functions of a conventional total station.

“Current as-built verification method is time-consuming and labour intensive because much of the measurement and analysis of disparities is done manually. The reason we bought the Nova MS60 in the first place, was to make these tasks less labour intensive. Soon after the purchase, we found out about the MLIT project. We focused the expertise available across the four companies and came up with a specific method for construction management using points and surfaces. This also had the potential to enable high productivity when verifying the as-built, so we tendered for the project,”描述了Kanatsu Giken土木工程部信息技术小组的团队负责人Yoshinobu Kimura。

The consortium conducted field measurements and data analysis at five sites and based on the results, compiled and submitted recommendations to MLIT. In 2019, MLIT announced their evaluations of all submitted projects – this consortium won an ‘A’ rating, the highest evaluation.

通过测量地位桩和3D设计数据（蓝线）获得的点云数据之间的比较

平面（粗糙度）对点云数据的比较评估，通过测量与3D设计数据的地位桩的构建

通过测量基础和设计数据（蓝线）获得的点云数据之间的比较

平面(粗糙度)点的比较评价cloud data obtained by measuring the as-built of a footing against the 3D design data

By conventional techniques, it takes a total of three people - a pair taking measurements and a photographer - to measure the as-built of the cast-in-place pile.

With the trial techniques, one person can operate the Nova MS60 to perform measurement and photography。试验技术将测量现场桩的测量所需的工时减少了一半以上。

The footing is a reinforced concrete foundation with shock-absorbing function. As it is chamfered, reading of accurate corner points can be an issue.

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Manhours for measurement work halved

对于码头，由于要求在高度和狭窄的空间中进行测量, planar evaluations using 3D point cloud data is very useful.

The trial was run for the as-built measurement and verification during the construction works on two bridge abutments and two bridge piers of the outer and lower portions of the Ohguni Viaduct in Japan. The results from the trial were divided into cast-in-place piles, footings, and housings.

为了能够有效地对整个顶部进行准确进行准确的验证，这是试验技术的最大优势之一。

“与传统方法,当我们测量the standard height of the top of the pile, we used a stepladder or something similar to climb over the reinforcements that protrude from the pile and had a surveyor stand in the centre. The pile diameters were measured by teams of two, taking measurements in two directions - one along the axis of the bridge, and the other, perpendicular to this. This work was repeated again and again until all the piles were measured. Another worker was needed to take photos of the as-built verification process.

使用Nova MS60，您可以从钢筋外部进行测量。不再需要成对成对工作以用胶带测量测量桩芯和桩直径，然后计算中心点，因为这些可以通过数据分析来准确地确定，”explains Kimura.

多阶段将测量工作所需的经费减少到不到一半。工人的停机时间从传统技术从83.3个小时减少到37.27小时。

In addition, because the data captured by the Nova MS60 is uploaded to the point cloud processing system for the as-built measurements, there is no need to take photos for as-built verification separately. This also eliminated the time involved in organising the photos after the work on site.

The footing is a foundation of reinforced concrete placed on top of the cast-in-place piles. In the trial, the scaffolding proved to be an obstacle. The piers sit on the footing and support the bridging superstructure.

对于码头和立足点，脚手架被证明是一个障碍，必须经常移动乐器。尽管如此，试验任务花费了8.5次，与30.9次的持续时间相比，与传统技术进行的40次Manours相比。

Comparison of point cloud data obtained by measuring the finished shape of the pier and the design data (blue line)

平面(粗糙度)点的比较评价cloud data obtained by measuring the as-built of a pier against the 3D design data

“For footings and piers, we only managed a manhour reduction of around 20 per cent. But in cases where there are many structures to measure, even 20 per cent represents a substantial saving. Also, if 3D laser scanning is established as a standard process, construction sites will devise workflows for building and removing scaffolding so that measurements can be performed efficiently, and this should reduce manhours even further,”says Kimura.

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Use of point cloud data boosts productivity increases accuracy and improves safety

This innovative method of as-built verification using point cloud data has a myriad of potential benefits, including higher productivity, higher accuracy, and improved safety. Furthermore:

• As-built measurement can be performed by a single worker.

• Once the data has been captured, it is possible to measure dimensions between arbitrary coordinates or view cross sections at any position.

• It is no longer necessary to take and organise as-built verification photos.

• Being able to calculate XYZ axes deviations is unprecedented and has the potential to increase the precision for maintenance and management.

Even after the construction has progressed and the piles and footings are buried underground and invisible, the status of these invisible structures can be accurately gauged and carefully managed in the future. Keeping a detailed record of the construction process improves safety and reliability and can be expected to reduce the incidence of major accidents.

此外，应用的机会可能会扩大。潜在用途包括将捕获的数据上传到CIM，以处理和组合上述技术与VR（虚拟现实），AR（增强现实）和MR（混合现实）技术以及可穿戴的终端，从而改变了建筑工作的性质。

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立即查看叠加在点云数据上的3D设计数据

与3D设计数据（CIM）合并了整个结构的量云数据。

易用性，一个总站的熟悉操作接口与高性能电动机驱动器相结合，用于高速旋转和反转以及高激光扫描速度，从而带来了完全的用户满意度。

“The greatest benefit of the Nova MS60 is that you can view 3D design data superimposed on point cloud data in real time – you simply look at the screen on the Nova MS60 on-site and see the differences immediately. If a reading is not within the standard value range, either the measurement position or something else is wrong. And so, by checking against the 3D design data as you work, you can verify the as-built without mistakes,”explains Kimura.

Kanatsu Giken conducted this trial project with the theme to ‘Make the most of technology in the field’ and brought together engineers and the construction site in pursuit of innovation.

“In this trial, we simply put a proposal into practice, showing that there is an alternative way to do things. As the requirements change due to the shift from engagement to full adoption of i-Construction, we will continue to embrace flexible thinking and creativity to improve productivity on construction sites and make the sites a more attractive place to work,”concludes Kimura.