Preserving mankind's past from mother nature's quakes

土木工程师正在不断寻找无损的测量技术，这些技术可以帮助估计结构状况。Leica Geosystems的高清测量（HDS）或激光扫描满足了这一需求。

A joint research team comprised of members from UC Berkeley’s Structures Laboratory (a research lab specialising in full-scale structural testing and numerical analysis), Miyamoto International (an earthquake and structural engineering firm in the USA), Smart Scanning Solutions, LLC (a 3D scanning and modelling service provider in Uzbekistan) and BNZ (Leica Geosystems’ representative in Uzbekistan) has been deploying HDS reality management technology at heritage monuments along the historic Silk Road within Uzbekistan. Multiple monuments have been captured and analysed for earthquake susceptibility.

The beginning: assessment of natural decline

As a representative example of the many heritage monuments, the Registan Square ensemble in Samarkand, Uzbekistan was selected. The ensemble includes the Ulugh Beg Madrasah, 1417-1420, the Sher-Dor Madrasah, 1619-1636, the Tilya-Kori Madrasah and Mosque, 1646-1660, and the 18th century Chorsu domed market.

Earthquakes, extreme seasonal temperatures, normal depreciation of the buildings and the economic crises of the 18th and 19th centuries have left the ensemble in a ruined condition. Structural repairs and straightening of the minarets had been conducted in 1923 and 1932; however, major restoration works were undertaken in recent years.

The ensemble was scanned from more than 70 stations with a Leica ScanStation. In addition to the global dimensions of all monuments located within the ensemble, the scans captured all details of the monuments: tile shape and dimensions, their overall locations in the monuments, any imperfections and the overall geometric shapes of the portals and facades. To achieve this level of detail in point density, all scans were conducted with a density of 2 mm by 2 mm.

The scan data produced extremely valuable results to be used in the decision making of further restoration strategies for the monument located in this earthquake-prone area of Central Asia. In generation of finite element models from the point cloud, Leica Cyclone software was used for surfaces with complex geometry.

“With the ScanStation's ability to achieve ultrahigh scan speeds, we were able to quickly collect the data needed for a thorough investigation of the monuments,” said Liliya Myagkova, Smart Scanning Solutions CEO. “And气旋’s simple registration enabled the team to process the point clouds for fast analysis.”

其中一个倾斜的尖塔的点云为有关结构中倾斜度的问题提供了答案。基于对点云的分析，获得了4.6％的倾斜度估计值。尖塔的原始锥度估计为2.3％。

激光扫描的新探险和监视

The laser scanning expeditions were expanded into new cities. An extensive list of historic structures included many cities of Uzbekistan: Bukhara, Shakhrisybaz and Tashkent. In addition to that, more historic structures in Samarkand were scanned.

Shakhrisyabz is located in southern Uzbekistan approximately 80 km south of Samarkand, Uzbekistan. Once a major city of Central Asia, it is primarily known today as the birthplace of 14th century Turco-Mongol conqueror Timur. The scanned monument, the Kuk Gumbaz (Blue Dome) Mosque, is from the Timurid Dynasty era and it is on the UNESCO World Heritage List. The monument was built in 1437 and over the centuries has undergone several restorations and reinforcement efforts.

The historic monument was scanned from 13 stations with aLeica ScanStation C10。数据注册以旋风进行，对于最终注册中使用的所有扫描，误差不超过3 mm。纪念碑从外部，主厅内和楼梯内部进行扫描，门户和主结构之间有大裂缝。

“借助乌兹别克斯坦极端的大陆气候，研究团队需要确保它可以依靠这些工具。由于C10可以在-20至+50摄氏度的温度下工作，因此这是该项目的理想选择。” BNZ总监Brian Quigley说。“整个360°x 270°视场还确保扫描纪念碑的复杂表面将捕获所有功能，并使研究人员更简单。”

The monument’s point cloud was investigated for anomalies. The main portal was investigated for its inclination from a vertical plane passing through the bottom of both piers. The portal’s inclination increases from south to north with the maximum differential displacement of 0.6 m at the top north corner. To ensure this degree of inclination of the portal is not progressing, a periodic monitoring by laser scanning was recommended to be carried out. It was also advised to proceed with the installation of laser targets to increase accuracy of monitoring. The permanently installed targets provide a consistent comparison between point clouds collected at different times.

有限元模型的几何形状是从点云生成的。所有主要的缺陷和现有的增援都包含在模型的几何形状中。在专业软件SAP2000中进行了数值建模和后续分析。

Since there is a very large variability in the material properties of masonry walls, material tests were conducted on a brick recovered from the site. The material properties were used within the software for accurate modelling.

The minaret was scanned at different times to check if the inclination is progressing over time. The first scans were conducted by theScanStation C10第二点云是由P系列扫描仪收集的。第一次扫描已在旋风中进行了第二次扫描。在每个高程中，倾斜度估计为矢量，并具有方向性和价值。后一个结果使用了高清激光扫描的主要优势，该扫描捕获了表面的多个点，而其他方式无法通过其他方式获得。

进一步保护的未来研究

The test projects won interest from, and collaboration with, the Uzbekistan authorities dealing with heritage buildings. This provided permissions for the additional heritage scanning along Uzbekistan's active seismic zones in Samarkand, Bukhara, Tashkent and Shakhrisyabz.

通过HDS扫描与材料测试相结​​合，产生了先进的校准模型，考虑了砖，当前状况和以前的结构增强。正在制定长期监测，并根据研究数据提供保护建议，包括对具有多个结构性关注的活跃清真寺的抑郁设备进行调查。

“Laser scanning helps us to capture structural anomalies of historical artefacts so we can help protect them for future generations,” said Amir Gilani, Miyamoto International, Manager of Earthquake Engineering Department. “Without this advanced technology, it would be challenging to get the as-found geometry of historic structures with accuracy of few millimetres that is essential for structural analysis.”

In recognition of the team’s effort and value of the collected data, the point clouds were accepted into the CyArk 500 Challenge database, an international effort to catalogue and archive endangered cultural heritage.