Ancient Secrets Of Dougong Brackets: How 2,500-Year-Old Buildings Could Survive Earthquakes

Ellen Lloyd - AncientPages.com - There is still much to be learned from our ancestors who were familiar with several types of advanced technologies.

Dougong brackets were used a very long time ago to construct buildings that could survive earthquakes.

About 2,500 years ago, ancient people designed and engineered a solution that prevented buildings from falling apart during earthquakes. The ancient builders created a series of brackets known as dougong.

Various types of dougong brackets. 

The earliest evidence of dougong brackets comes from China and dates to 1100 B.C. Ancient builders in Persia and India were also familiar with dougong brackets in their simplest form. A bracket set is a group of wood blocks (dou) and short beam-arms (gong) cut so they interlock and form a unit when stacked up together.

Timber traditionally comprises the main structure in Chinese architecture, while walls, doors, and windows are not load-bearing, sometimes made of latticework, mud or other delicate material.

Colorful dougong supporting a structure at Sagami-ji, Japan. Image credit: 663highland

In such a timber structure, with columns as the lower part and beams as the upper part, a middle part between columns and beams which helps eaves stretching out is extremely important. This is the special part of dougong, a unique structural element of interlocking wooden brackets. Interlocking bracket sets are formed by placing a large wooden block (dou) on a column to provide a solid base for the bow-shaped brackets (gong) that support the beam or another gong above it.

Ancient scientists discovered that when dougong brackets were interlocked together could transfer the incredibly heavyweight of a temple roof to the supporting columns, and they contained so many redundancies that they could not be shaken apart.

When interlocked together, these could transfer the incredibly heavyweight of a temple roof to the supporting columns, and they contained so many redundancies that they could not be shaken apart.  Dougong brackets were a superb solution because they connected with friction and gravity.

According to Richard S. Wiborg who has studied ancient Chinese and Japanese architecture “From 200 B.C. to 600 A.D., Chinese builder-architects adapted brackets to function perpendicular to the wall-plane as cantilever beams. They sometimes added a cross-yoke onto a perpendicular arm.

Now a bracket set could support a wall and a small roof eave. At this point, the bracket set became a three-dimensional cluster of parts.

During the Tang, Liao, and Sung dynasties (600-1200 A.D.), the art of bracketing reached its zenith. Builders wanted to erect bigger structures. They enlarged the elements (columns, beams, rafters) while preserving the same proportions. The basic building format, i.e., a rectangular plan wider than deep enclosing a single space, did not change. The roof and roof-overhang (eaves) needed to be proportionally larger, though.

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Builders had to figure out how to construct a wider eave. So they invented a larger bracket system that could cantilever farther out from the wall-plane and they added a new structural member—the eave-purlin—to carry rafters beyond the wall purlin.”

Dougong brackets solved four problems that arise as buildings get bigger. They helped architects to reduce beam spans, to brace wall sections above columns, how to support a wide eave, and to strengthen the frame.

By spreading the dougong brackets’ tolerances over multiple joints, builders could achieve a measure of flexibility that prevented the brackets from cracking and splitting. In regions where earthquakes occurred frequently, the use of dougong brackets saved many lives and money.

It’s truly remarkable to see that more than 2,000 years ago, ancient people knew how to construct timber building that could withstand devastating earthquakes.

While ancient Chinese used dougong brackets to keep their buildings from falling apart, ancient Romans discovered a way to construct piers that survived continuous battering of the ocean waves for more than 2,000 years.

Modern concrete seawalls embedded with steel crumble within decades, but ancient water-based structures became stronger over time. Scientists may have solved the mystery of ancient Roman concrete that still stands strong.

Written by Ellen Lloyd – AncientPages.com

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