-the world as I see it
Although timber is rarely used as a construction material in modern-day China, history tells us that it was used extensively in the past. The Chinese used timber as roofing and flooring material and incorporated timber beams and columns in their structures. The structural system mainly relied on the timber framework as the walls were non-load bearing. This form of construction did not restrict the location of openings in the structure and hence there was more freedom to decide where the windows could be placed, without worrying too much about the safety and stability of the structure. It was deemed essential to paint the framework to prevent the onset of rot in the timber. With time, the painting of the pagodas became an integral part of the Chinese architectural style. Colours are very symbolic in Chinese architecture and are used to mark the importance and function of the structure. The colour yellow is associated with nobility and was used in royal structures. Red and green are considered colours of life.
The origin of the pagodas in China dates back to the period of the advent of Buddhism from India. The pagodas were meant to be religious monuments which preserved holy objects ranging from relics and keepsakes to sacred documents. The Chinese architects integrated the Indian style of constructing stone stupas into the traditional architectural style and came up with a suitable design. The pagodas were tall and symmetric. They were built using different materials- stone, bricks, wood, iron, glazed tiles and occasionally, even gold! They were multi-storeyed with the number of floors always being an odd number. The minimum number of floors was 3 and most of them went up to 9, or even more. At the apex, pagodas were topped with a steeple – a symbol of the power of heaven. There are some speculations as to why the pagodas always had many storeys, which I have mentioned below.
Among the religious buildings in China, I am most enchanted by their pagodas, particularly the Yingxian Pagoda which also goes by the name of Sakyamuni. This used to be the tallest wooden pagoda in the world until 2007, when the construction of the Tianning pagoda (Changzou temple) was completed. The Sakyamuni Pagoda is about 67.31m in height, while the one at Changzou is more than two times taller (153.79m).
Housed in the Fogong Temple, the Sakyamuni pagoda was constructed in 1056 A.D. during the reign of the Liao Dynasty. The pagoda is erected on a stone platform measuring 4 metres in height. The pagoda itself is built entirely out of wood obtained from the Xingan larch trees that were found in abundance in Northern China. When you look at the Sakyamuni pagoda from outside, it appears to be a 5 storeyed structure; although in reality it is 9 storeys high. This is because the four mezzanine layers are concealed within the five outer storeys. The ground floor is topped by two tiers of eaves.
The plan of the building is octagonal in shape and consists of two concentric rings of columns. The columns are not vertical, but inclined to the apex of the pagoda. The angle of inclination depends on the position of the columns in the pagoda, and hence on the load carried.
A series of tie beams connects the columns in each ring. An individual beam is connected to a column by means of a slot which forms the connection (tenon and mortise joint). The connections are comprised of only tenon and mortise joints and dou gong brackets. A dou gong bracket is composed of three components – a wooden block called ‘dou’, a lever arm called ‘ang’ and a short arm called ‘gong’.
In the Yingxian pagoda, the dugong brackets are arranged in layers so that they can transfer the loads from the roof to the subsequent storeys. There are 54 different types of dou gong brackets used in the pagoda!! The dou gong system is arranged akin to a baskets of flowers. The layered du gong bracket system symbolizes a hierarchical system and is therefore used only in buildings of importance. The number of layers of these brackets is proportional to the degree of importance of the building. In the Yingxian pagoda, they are set under the overhanging eaves of the building and between the top of each column and cross beam.
The connections between the wooden members were originally supposed to be tight fitted joints. But as it is widely known, timber undergoes shrinkage with time and dries out. Due to this the connections became loose but are still kept together by gravity loads. In the event of an earthquake, the connections are able to move and dissipate energy and hence contribute to the high seismic resistance of the Yingxian pagoda. Additional stability is derived from the relatively short columns. Records reveal that during a high intensity earthquake lasting seven days during the reign of the Yuan Dynasty, the pagoda stood firm. Even when the Yingxian County area was affected by the severe earthquakes in Xingtai and Tangshan of Hebei Province and in Helinger of Inner Mongolia, the wooden pagoda did not suffer any major damage. In 1996, this structure was listed as a UNESCO World Heritage Site.
Although this wooden pagoda has been able to withstand several earthquakes, severe winds, lightning strikes, high amounts of precipitation and wars in the past 958 years, it is highly unlikely that it is going to last for another millennium. Column heads and ridge beams are twisted and broken. Some of the interior columns have developed cracks. The tower of the pagoda leans slightly to the north-east. There is an obvious tilt in the first and second floors and the scientific community has issued warnings about the inability of the structure to withstand a violent storm or an earthquake. In 2001, the State Administration of Cultural Heritage (SAHC) called for ideas from both local and global experts.
Finally, the following repair intervention options were proposed:
However, more than a decade on, the structure is still in disrepair and its condition is deteriorating by the day. In March 2012, the local government of the county of Yingxian commissioned a project to reduce moisture-induced problems by replacing rotten tiles and fixing the cracks in the building. To a certain extent, this protects the building from problems like erosion due to rain and snow loads and leakage through the dilapidated roof.
The authorities in China say that once the pagoda makes it to UNESCO’s list of protected World Heritage relics, swift measures will be taken towards restoration as there will be enough funds to carry out the necessary measures. In a situation which involves the preservation and restoration of a structure with such a glorious heritage and something so vital to the Chinese identity, it should be of prime importance that the repair interventions be carried out as soon as possible. But with financial and bureaucratic issues, one has to wait and watch what becomes of the Yingxian Pagoda and just hope for the best.
References and further reading:
“STRUCTURAL PERFORMANCE OF DOU-GONG BRACKETS OF YINGXIAN WOOD PAGODA UNDER VERTICAL LOADING” – Enchun Zhu, Zhiyong Chen, Jinglong Pan, Frank Lam
“EXAMPLE OF TRADITIONAL TALL TIMBER BUILDINGS IN CHINA – THE YINGXIAN PAGODA” – Frank Lam, Minjuan He, Chichao Yao