**1. Introduction**

Building monolithic movement, a kind of procedure to relocate the position or direction of an existing building whilst maintaining its integrity and availability, has attracted much interest due to its resource-saving, environmentally friendly and low-cost advantages [1]. Since 1998, a series of related protection statutes and regulations with an emphasis on the protection of preserved historical buildings have been published in mainland China, aiming at materializing historical influences and differences [2]. The corresponding monolithic movement technology is also considered as a new resolution to conserve historical buildings whilst adapting them to new conditions and uses [3].

Compared with traditional demolition and reconstruction, the monolithic movement of historical buildings has the particular advantage of maintaining the original humanistic value and the overall structural integrity. The embryonic form of modern movementengineering technology can be traced back to 1983, when a school building with a masonry structure (weighing 8000 kN) was moved a distance of 15 m in the city of Warrington, England [4]. With the advancement in technology, the monolithic movement techniques of historical buildings are being developed and implemented worldwide [5]. For example, Kossakowski et al. [6] described the case of the relocation of the Rogatka Grochowska building, which was carried out in Warsaw. The related work and projects in China came late to developed countries. Shan et al. [7] implemented a complex monolithic movement of the Ci-yuan temple with a brick-wooden structure, which was built in the Tang Dynasty and was located in Anyang City in China. Moreover, the documented application projects,

**Citation:** Shen, L.; Yang, B.; Yang, Y.; Yang, X.; Zhu, W.; Wang, Q. Real-Time Monitoring for Monolithic Movement of a Heritage Curtilage Using Wireless Sensor Networks. *Buildings* **2022**, *12*, 1785. https:// doi.org/10.3390/buildings12111785

Academic Editor: Jurgita Antucheviciene

Received: 27 September 2022 Accepted: 20 October 2022 Published: 25 October 2022

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including Jinlun Guild Hall (Qing Dynasty), Shanghai Concert Hall (1930), and Centennial Minli high school of Shanghai (1920), were also realized through historic building moving [8,9]. The existing cases signify that three general routes, including moving with rolling bars, moving with a slide layer, and moving by trailer transportation, have been performed successfully as monolithic movement applications of historical buildings in China. To date, due to the buildings' intrinsic rarity and structural aging, only limited paperwork has been disclosed, and few practical applications of the monolithic movement technology of an overall heritage curtilage courtyard have been carried out; however, this technology is slowly becoming more widespread and pervasive in modern civil infrastructure.

During the monolithic movement procedure, it is well known that prioritizing the protection of the historical building, with its intrinsic cracks and cavities, against destructive loads is essential. A program of non-invasive monitoring needs to be undertaken to inform about the ongoing structural status [10–12]. As the moving of historical building means there are some risk factors, the traditional inspection methods for structural cracks, deterioration, and damage tend to be inconvenient and dangerous. With the progress of wireless communication and sensor miniaturization, the wireless sensor network (WSN) system—with a series of smart sensors in a self-organizing and multi-hop manner for monitoring structural deformation—has been developed in recent years [13,14]. Compared with a customary wired network, the WSN boasts easy deployment, a dramatically lower cost of installation and maintenance, and it provides a flexible and manageable approach to monitoring remotely in real time [15,16]. Dong et al. [17] compared the WSN system with the wired sensing system for the performance of a 2-story, 2-bay concrete frame building, and they found that the WSN achieved the same quality of data as that of the wired system. Furthermore, the existing research has proved that the WSN-based approaches could identify the existence and location of damage for long- and short-term monitoring to achieve structural health and safety assessments of historic buildings whilst maintaining their structural integrity and functionalities [18,19]. For example, Wu et al. [20] introduced a dedicated WSN into Torre Aquila, built in the 13th century and located in the city of Trento, Italy, to evaluate its static and dynamic state by utilizing accelerometers and deformation sensors. They also found that the collected data are in agreement with the prediction from the three-dimensional finite element (FE) results. Samuels et al. [21] developed a WSN for monitoring the tilt in the walls of the St. Paul Lutheran church, an historic masonry church with a timber-framed roof, under rehabilitation. Potenza et al. [22] undertook the deployment, test, and management of a WSN for the structural monitoring of the Basilica S. Maria di Collemaggio with masonry structure, which is designed for seismic and dynamic response analyses via acceleration, crack opening, and wall inclination measurements. Mesquita et al. [23] adopted temperature, relative humidity, and displacement sensors to perform a one-year monitoring of the Foz Côa Church (in Portugal), a damaged historic structure from the 16th century based on the WSN system. Barsocchi et al. [24] presented an application of the WSN technology on the Matilde Tower in Livorno (Italy), an historic masonry tower built in the Livorno harbor, to monitor the structural health over the long term and detect potential damages in real time. However, given the uniqueness and the preservation of each historical building, real-time monitoring applications based on the WSN system for the case of its monolithic movement are still very challenging, and few related works have yet been documented.

Therefore, this paper aims to explore the real-time monitoring ability of the WSN in a monolithic movement project for a heritage curtilage with a masonry–timber structure. Considering the age and the poor structural integrity of the heritage curtilage, four kinds of smart sensors were adopted with the aid of practical engineering experiences and FE simulation to real-time monitor the structural deformation and deterioration. Then, the acquisition system receives the processed data and transmits them to a cloud platform via wireless remote communication (3G/4G/GPRS). Finally, all the data can be accessed directly at the preferred time with wireless communication in locations where internet access is available. This paper not only develops a comprehensive scheme for monolithic

movement monitoring of a heritage curtilage, but also provides an in-depth understanding of the structural deformation and deterioration during monolithic movement.
