The pace of ancient construction and repair is constantly accelerating.
  Did modern technology save ancient architecture?

  The repair and protection of ancient buildings in my country is a project that integrates cultural promotion, inheritance of skills, technical support, etc. Although scientific and technological means cannot solve all the problems of the protection and repair of ancient buildings, it is an important support for the ancient buildings to be reasonably protected and prolong their lives.

  The Imperial History Museum, located on Nanchizi Street in Beijing, was the Royal Archives during the Ming and Qing Dynasties, and it is also the only existing brick and stone archive storeroom in my country. It is divided into two houses, north and south. Due to historical reasons, the south house has become a large complex, and there are serious problems in illegal construction and private wire pulling. Recently, the illegal construction and demolition work in the hospital was officially launched, and then the National Palace Museum will restore the original appearance of the cultural relics and monuments.

  As the concept of protecting cultural heritage and promoting China's excellent traditional culture gradually penetrates into the hearts of the people, the pace of cultural relics and ancient constructions and repairs in various regions is accelerating. But how to protect and repair ancient buildings more scientifically is also worth discussing and paying attention to.

  New technology is used for early diagnosis to make later repair easier to grasp the "degree"

  Under what circumstances, the ancient buildings need to be repaired is a topic of great public concern.

  "Whether ancient buildings need to be repaired is subject to the results of structural safety performance assessment." Dr. Zhou Qian, a research librarian of the Palace Museum who has long been engaged in the research work of ancient building protection, pointed out that the current protection and maintenance standards for masonry cultural relics in China are not yet mature. However, the "Technical Specifications for the Maintenance and Reinforcement of Wooden Structures in Ancient Buildings" related to ancient wooden structures put forward clear standards for the repair of ancient buildings.

  "An ancient building is a kind of immovable cultural relic, and its repairs are divided into many types, including daily maintenance and repair, local damage repair, and rescue repair in the case of severe damage to the overall structure." Shaanxi Cultural Heritage Protection Research Zhao Qiang, the dean of the institute, pointed out that it is not possible to generalize exactly when to repair ancient buildings. At present, there is no scientific conclusion and quantitative index.

  For each specific ancient building restoration project, the actual challenges faced are different. In Zhao Qiang's view, it is difficult to have a standardized response plan. Only on the basis of rigorous and meticulous preliminary research can it be possible to master the ancient The "degree" of building restoration is truly minimal intervention when formulating a restoration plan.

  According to Zhou Qian, before the National Palace Museum carries out repairs to ancient buildings, it is necessary to carry out a survey of the status quo of the building, including investigating the damage of the building itself, drawing survey paper, assessing the current status of building safety, and proposing maintenance and protection plans.

  "A lot of solid preliminary research work is very important for scientifically formulating repair plans. Just like seeing a doctor, before confirming a diagnosis and treatment plan, you need to do a careful inspection and find the root cause of the prescription to make accurate prescriptions." Zhao Qiang said.

  With the help of scientific and technological methods, the current status of ancient buildings can be more comprehensively and effectively evaluated, just as high-tech equipment can perform more accurate results on physical examination of people. For example, Zhou Qian said that with the help of three-dimensional laser scanning equipment, the overall size of ancient buildings can be obtained more accurately; with the help of stress wave and impedance meter technology, the holes and defects inside ancient buildings can be measured; with the help of computer simulation analysis, the ancient buildings can be preliminarily analyzed Whether there are hidden safety hazards, etc.

  In the past, before the repair of ancient buildings, experienced teachers used hammers to listen to the sound to judge the damage of ancient wooden buildings. But this method can only know whether the wood has holes, and it is unclear how big the holes are, where they appear, and how rotten they are. Moreover, if the wood is inside the masonry structure, it is even more impossible to judge.

  Now, ancient architecture experts have introduced micro-drill resistance meters. Its appearance is a rectangular box with an elongated drill bit 60 cm long and only 1.5 mm in diameter. Using it to break into the heart of the wood will only leave an obscure small hole in the surface of the wood, which will hardly damage the ancient building itself. The instrument obtains a "cardiogram" with a curve through the resistance value detected by the drill bit. "If the curve falls from a peak and then rises after a period of lows, then it can be judged that there is a hole in the wood, and the size of the hole is clear at a glance.

  Last year, Qi Ying, a lecturer in the Department of Historical Building Conservation of Beijing University of Architecture, led a team to perform radar detection on the pillars of Dongyue Temple in Xi’an. The pillars of Dongyue Temple are inside the wall, and the appearance of the pillars themselves is not visible, nor is it possible to dismantle the wall to judge the internal wooden structure. With the help of the new technology of radar flaw detection, the column can be probed through the wall, and the internal conditions of ancient buildings can be relatively intuitively understood.

  "In the past, the surveying and mapping of the ancient building itself was also a complicated project, which often required several people to work continuously for several days. Now, it may be finished by scanning a machine with one person for an hour." Qi Ying said.

  New materials help repair to achieve the "least intervention principle"

  Once the safety of ancient building structures is threatened, repair work is imperative. Zhou Qian introduced that according to the relevant regulations, the maintenance of ancient buildings should abide by the principle of "not changing the original state". The so-called principle of "not changing the original condition" refers to the fact that the ancient buildings are as consistent as possible before repairs in terms of materials, structural composition, construction technology, etc.

  According to Dai Shibing, director of the Historical Building Protection Experiment Center of the School of Architecture and Urban Planning of Tongji University, in actual repairs, for various reasons, it is difficult to completely "intact". If repairs are indeed necessary, under the premise of adhering to the "minimum intervention principle", new technologies and new materials can be used to properly protect and repair ancient buildings.

  In fact, in some restoration cases, people can also capture the new material. For example, Qi Ying said that there may be some vertical cracks in the brick-wood building. If the cracks do not affect the use of the material itself, it is often strengthened by the use of carbon fiber materials to enhance the stability of the building structure.

  Not only brick-wood buildings, but also the use of carbon fiber materials in the protection and repair of some modern buildings. For example, some modern buildings on the Bund have also used carbon fiber materials for reinforcement. "The carbon fiber material itself is very light, it will not bring too much new load to the building, and it has good rigidity and adaptability." Qi Ying said.

  In addition, in the protection and repair of stone components, professionals have begun to use more new materials such as nano-lime. Dai Shibing introduced that lime is a traditional building material. Nano lime has the same composition as ordinary lime and is calcium hydroxide. However, nano-scale lime particles can penetrate deeper into the degraded areas of the stone to achieve the reinforcement effect.

  The ancient construction and repair that technology is not almighty still face many difficulties

  Although there is technology to help, it is undeniable that the ancient construction and repair are indeed facing many difficulties.

  Zhou Qian admitted frankly, first of all, from the perspective of ancient building materials, the materials of ancient buildings in China will be inevitably damaged by chemical elements in the air or rain and snow erosion for a long time. The degradation of physical and mechanical properties, and it is difficult to ensure that the repair materials of ancient buildings use their original materials completely, which is also the biggest difficulty.

  Secondly, ancient people built ancient buildings mostly with experience, and few drawings and technical schemes remain in the world. The structural characteristics and connection methods of some ancient buildings are difficult to obtain accurately, which brings difficulties to the repair and protection of ancient buildings.

  In addition, there are relatively few professionals in ancient building protection in my country, which is also one of the bottlenecks faced by ancient building repair. "Conservation and repair of ancient buildings is a professional job, and it needs professional people to do it. Now everyone's awareness of ancient construction protection has increased, but there is still a gap in professional talents." Qi Ying said.

  In fact, compared with specific repair projects, the preventive protection of ancient buildings is more important. The so-called preventive protection refers to the daily monitoring, evaluation and regulation intervention to minimize the harm of various natural environments or human factors to cultural relics, as much as possible to prevent or delay the aging and damage of cultural relics, to achieve the purpose of long-term preservation. In this regard, Zhou Qian said: "In fact, ancient buildings, like humans, also have the problems of aging and illness. They need regular medical examinations and timely repairs and maintenance in order to prolong their lives."

  Zhou Qian said that the repair and protection of ancient buildings in my country is a project that integrates cultural promotion, inheritance of skills, and support of science and technology. Although scientific and technological means cannot solve all the problems of the protection and repair of ancient buildings, it is an important support for the ancient buildings to be reasonably protected and prolong their lives.