Innovating as-built verification

作者：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 MultiStation，一种具有3D激光扫描的仪器，并具有常规总站的测量功能。

“当前的近期验证方法是耗时的和劳动力密集的，因为大部分差异和分析都是手动进行的。我们首先购买Nova MS60的原因是要使这些任务减少劳动力密集。购买后不久，我们发现了MLIT项目。我们集中了这四家公司可用的专业知识，并提出了一种使用点和表面的特定方法进行建筑管理方法。这也有可能在验证该项目时能够使高生产率提高，因此我们为该项目招标了，”describes Yoshinobu Kimura, team leader of the information technology group in the civil engineering division at Kanatsu Giken.

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.

Comparison between point cloud data obtained by measuring the as-built of cast-in-place piles and 3D design data (blue lines)

Planar (roughness) comparative evaluation of point cloud data obtained by measuring the as-built of cast-in-place piles against 3D design data

Comparison between point cloud data obtained by measuring the as-built of footing and design data (blue lines)

Planar (roughness) comparative evaluation of point cloud data obtained by measuring the as-built of a footing against the 3D design data

通过常规技术，总共需要三个人（一对进行测量和摄影师）来测量现场堆的铸造堆。

With the trial techniques, one person can operate the Nova MS60 to perform measurement and photography.The trial techniques reduced the number of man-hours required for measurements of cast-in-place piles by more than half.

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

In the case of piers, due to the requirement to take measurements at height and in confined spaces，使用3D点云数据进行平面评估非常有用。

该试验是在日本Ohguni高架桥外部和下部的两个桥梁基台上和两个桥梁的施工过程中进行的测量和验证。试验的结果分为现场桩，基础和住房。

To be able to efficiently conduct accurate as-built verification of the entire top of the pile was one of the great advantages of the trial technology.

“使用常规方法，当我们测量桩顶的标准高度时，我们使用了一个梯子或类似的东西，类似于爬过堆积的增援，并在中心有一个测量师。桩直径通过两个团队测量，在两个方向上进行测量 - 一个沿着桥的轴，另一个垂直于此。一次又一次地重复这项工作，直到测量所有桩。需要另一个工人拍摄剩下的验证过程的照片。

With the Nova MS60, you can measure from outside the steel reinforcements. It’s no longer necessary for surveyors to work in pairs to measure the pile cores and pile diameters with tape measures and then calculate the central points, as these can be accurately determined later by data analysis,”explains Kimura.

The MultiStation reduced the manhours required for the measurement work to less than half. Worker downtime got reduced from 83.3 manhours with the conventional techniques to 37.27 hours.

此外，由于将NOVA MS60捕获的数据上传到点云处理系统以进行临时测量，因此无需单独拍摄照片以进行验证。这也消除了在现场工作后组织照片所涉及的时间。

基础是放置在铸件堆桩顶部的钢筋混凝土的基础。在审判中，脚手架被证明是一个障碍。码头坐在立足点上并支撑桥接的上层建筑。

For the piers and footing, scaffolding proved to be an obstacle and the instruments had to be moved frequently. In spite of this, the trial task took 8.5 manhours compared with the 11 manhours for the footing and 30.9 manhours compared with the 40 manhours taken with conventional techniques.

比较measuri获得的点云数据ng the finished shape of the pier and the design data (blue line)

Planar (roughness) comparative evaluation of point cloud data obtained by measuring the as-built of a pier against the 3D design data

“为立足点和码头,我们只有一个工时管理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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点云数据的使用提高了生产率提高了准确性并提高了安全性

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:

•可以由单个工人进行实施的测量。

•一旦捕获数据，就可以测量任意坐标之间的尺寸或在任何位置查看横截面。

•不再需要拍摄并组织验证照片。

• 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.

Moreover, the opportunities for application are likely to expand. Potential uses include uploading the captured data to CIM for processing and combining of the above techniques with VR (virtual reality), AR (augmented reality) and MR (mixed reality) technology, and wearable terminals, changing the nature of construction work.

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Immediately view 3D design data superimposed on point cloud data

Merged as-built point cloud data of the entire structure with 3D design data (CIM).

The ease of use, a familiar operating interface of a total station combined with a high-performance motor drive for high-speed rotation and inversion, and a high laser scanning speed resulted in complete user satisfaction.

“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进行了该试验项目，主题是“充分利用现场技术”，并将工程师和建筑工地汇总在一起，以追求创新。

“在这项审判中，我们只是将提案付诸实践，表明还有另一种做事的方法。随着由于从参与到全面采用I构建的转变而导致的需求变化，我们将继续采用灵活的思维和创造力，以提高建筑工地的生产力，并使站点成为更具吸引力的工作场所，”concludes Kimura.