The Forbidden City’s unique architecture

chapter 3

Protecting the city from the ravages of time, fire and the fury of earthquakes

June 29, 2018


Marco
Hernandez

Constructed almost entirely from wood, the Forbidden City had one enemy above all: fire. With the palace at constant risk of sabotage and accidental conflagrations, it was essential to be well prepared to tackle the peril

Burning torches were used to illuminate the palace interior, so strict rules and protocol were established throughout the city to prevent accidental fires. The main fire risk was actually due to the vulnerability of the Forbidden City’s taller buildings to lightning strikes. The Hall of Supreme Harmony caught fire after being struck by a bolt of lightning just 100 days after its inauguration [ check chapter 01 timeline ]

Palace vats

Three hundred and eight iron and copper vats storing rainwater were dotted around the Forbidden City as a precaution against fire. They were as diverse in size and style as many of the other palace artefacts. Ming dynasty vats, for example, had simple rings on the sides, while vats from the Qing period had decorative bronze rings held by elaborate animal shapes. Perhaps the most striking were the 18 copper vats which surrounded the main Imperial Palace buildings with their sumptuous gold inlays

The city moat usually froze over in winter making it necessary to take precautions to prevent the water in the vats from suffering the same fate. The vats were placed on stone blocks over small fires so there would always be water on hand if a fire broke out

Preserving the wood

In a building made mostly of wood, preservation of the structures is very important. Although the major buildings in the Forbidden City have occasionally been restored and rebuilt after being damaged by fire, conflicts and wars, as well as by the passage of time, most of the other structures have remained intact for hundreds of years

The artisans’ aesthetic designs were not purely decorative – they also sealed and protected the woodwork to help preserve the structures. Purpose-made paint was applied in layers and pieces of patterned paper were used to help safeguard the surfaces

Seismic activity

Lightning wasn’t the only force of nature to have an impact on the way the Forbidden City was constructed. It is crucial for areas with seismic activity that a building’s weight is distributed evenly. Today, architects steer clear of placing heavy objects on top of a structure, but by contrast, ancient architects were able to support top-heavy buildings using pillars, without compromising stability

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ACTIVITY IN THE REGION
Although Beijing is not in an intensely seismic region, factors such as topography, fault lines and proximity to earthquake-prone zones affect how intensely an earthquake is felt. The Forbidden City would almost certainly be affected by a major earthquake under certain conditions. For instance, in 2010 tremors were felt 500km away when a magnitude-5 earthquake was reported in eastern Canada

Earthquakes since 1960
with a magnitude over 4.5

Through time

There have been 122 earthquakes recorded in the region since 1960, including a 7.5-magnitude earthquake on 27 July, 1976, near the Tianjin-Hebei border region

Mar.
1966

Jun.
1976

Nov.
1985

Jan.
1998

Mar.
2010

Feb.
2018

7.5mw

5.5mw

5.5mw

In October 2017, a series of studies at Beijing University of Technology looked at the impact of seismic activity on traditional structures, paying particular attention to the Palace Museum buildings. Scientists used data to create virtual models of the buildings to measure how they would stand up to simulated earthquakes

Displacement behaviours

Scientists exposed a 1:5 scale model to a 9.5-magnitude simulation to test the flexibility and resistance of the buildings in the Forbidden City to extreme conditions

Part of the teaser of "Secrets of China’s Forbidden City" on Youtube
Courtesy of BBC Channel4.

The scientists concluded that flexibility was a key factor enabling the wooden buildings to remain standing. Even without the walls, the structures can withstand the forces thanks to traditional Chinese construction methods [see Chapter 2 about the dougong]

Traditional Chinese buildings absorb the weight of the roof according to the same principle as a tree’s branches connecting to the trunk. Consequently there is no need for the walls to bear the brunt of the structure’s weight

FURTHER READING
This is the third and last chapter exploring the Palace Museum’s architecture

We would like to invite readers to navigate between the chapters as they are published. Other visual narratives will investigate daily life in the palace and follow the odyssey undergone by the royal collection. We hope you enjoy immersing yourself in the project much as we did making it for you

The Palace Museum

By the South China Morning Post graphics team

The Forbidden City’s unique architecture

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