Preserving mankind's past from mother nature's quakes

Civil engineers are in a continuous search of non-destructive measurement techniques that can help to estimate structural condition. The high definition surveying (HDS) or laser scanning, from Leica Geosystems fulfils this need.

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

作为许多遗产纪念碑的代表性例子，选出了乌兹别克斯坦撒马尔罕的雷吉斯坦广场合奏团。合奏包括1417-1420的Ulugh Beg Madrasah，Sher-Dor Madrasah，1619-1636，Tilya-Kori Madrasah和Mosque，1646-1660，以及18世纪的Chorsu Domed Market。

地震，极端的季节性温度，建筑物的正常折旧以及18世纪和19世纪的经济危机使整体处于破坏状态。1923年和1932年进行了结构维修和矫直宣礼塔；但是，近年来进行了重大的修复工作。

从70多个电视台扫描了该合奏，并带有Leica扫描仪。除了位于合奏中的所有古迹的全球尺寸外，扫描还捕获了纪念碑的所有细节：瓷砖形状和尺寸，它们在古迹中的整体位置，任何缺陷以及门廊的整体几何形状。为了达到点密度的细节，所有扫描的密度为2 mm x 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

激光扫描探险被扩展到新城市。广泛的历史结构清单包括乌兹别克斯坦的许多城市：布哈拉，沙克里斯巴兹和塔什肯特。除此之外，扫描了撒马尔罕的更多历史结构。

Shakhrisyabz位于乌兹别克斯坦撒马尔坦以南约80公里处的乌兹别克斯坦南部。它曾经是中亚的主要城市，今天主要被称为14世纪Turco-Mongol Conqueror Timur的发源地。扫描的纪念碑，库克·古巴兹（Kuk Gumbaz）（蓝色圆顶）清真寺，来自帖木儿王朝时代，在联合国教科文组织世界遗产名单上。这座纪念碑建于1437年，几个世纪以来，经历了几项修复和加强工作。

历史悠久的纪念碑在13个站点扫描Leica扫描C10. Data registration was performed in Cyclone and error did not exceed 3 mm for all scans used in the final registration. The monument was scanned from outside, inside of the main hall, and inside of a stairway with a large crack between the portal and the main structure.

“With Uzbekistan’s extreme continental climate, the research team needed to ensure it could rely on the instruments. As the C10 can work in temperatures anywhere from -20 to +50 degrees Celsius, it was ideal for this project,” said Brian Quigley, BNZ director. “The full 360° x 270° field of view also ensured scanning the complex surfaces of the monuments would capture all features and make the process simpler for the researchers.”

纪念碑的点云进行调查omalies. 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。

由于砌体壁的材料特性有很大的变化，因此在从该地点回收的砖上进行了材料测试。该材料属性在软件中用于准确的建模。

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。

Future research for more protection

测试项目的兴趣,和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。

“激光扫描有助于我们捕获历史文物的结构异常，因此我们可以为子孙后代提供保护它们，”地震工程系经理宫本国际宫（Miyamoto International）说。“没有这种先进的技术，以几毫米的准确性来获得历史结构的基础几何形状，这对于结构分析至关重要。”

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.