The mechanics of scaffolding
Mr Chan explained the mechanics of scaffolding with reference to trigonometry.
The function of bamboo scaffolding
The purpose of bamboo scaffolding is to enable the construction and renovation projects to be completed in safe and efficient ways.
Methods to build hanging scaffolds
The methods to build hanging scaffolds have changed nowadays. In the past, skilled workers used two long bamboos to be the foundation of a scaffold. The skilled workers would screw a hole on the exterior wall of a building and fix one bamboo against another forming a vertical triangular base. Nowadays, workers would use steel rods to build this base and nobody would use bamboo to build the base anymore.
The size of one grid of a bamboo scaffold is not fixed. A grid is 2 feet x 2.5 feet, which normally fits the body height of a Chinese workman from his shoulder to his bottom. Such size utilizes the elastic strength of a bamboo the best.
Bamboos for scaffolding are usually imported from Guangxi. Normally each piece is roughly of 7 metres long, an ideal length for transportation by cargo truck and boat. The diameter is normally 40 mm. A worker may cut a bamboo short or extend the length by joining two bamboos together, according to his needs.
Bamboo scaffolds and steel scaffolds
A bamboo scaffold and a steel scaffold each has its advantages and disadvantages. The former is more convenient to build and cheaper in price while the latter is stronger and requires less skill to build.
Single scaffold and double scaffold
As local legislation prohibits workers from working on a single scaffold nowadays, most single scaffolds are made for protective uses only. For example, to demolish certain structures, a single scaffold plus a safety net are set up to prevent smaller pieces of debris from falling onto sidewalk. Two single scaffolds make a double-layered scaffold. Required by law, workers are only allowed to work on a work platform, which is composed of a layer of wooden planks laying at a mid-level of a double-layered scaffold.
Double scaffold and work platform
The building of a scaffold starts from the corner. A long bamboo is set at an inclination of 45°. These inclined/tilted bamboos are formed into scaffolds horizontally first, then extended upwards. When the outer layer of a double scaffold is built, a platform is formed by laying wooden planks on a particular level. In the past, workers used to paint walls on a single scaffold. As smoothening work requires more tools, workers now prefer to work on a platform.
Single scaffold and double scaffold on the slope
In rainy seasons, there are more projects to maintain hill slopes. A single scaffold along a slope is used only for clearing grasses and conducting simple surveys. A double scaffold is needed for soil strengthening work. A slope scaffold is made with these steps: a bamboo is placed perpendicular to another bamboo; the third bamboo is placed at 45° against the vertical one to fix the structure. This bamboo at 45° is called “cheung” which is used to balance the bamboos and to fix the shape of a scaffold. The more “cheung” are used, the more stable the scaffold is.
Work platform of slope scaffolds
A single scaffold along a slope is used only for detecting problems by eye sight. A double scaffold with a work platform is necessary when actual work is to be conducted. Usually a platform is laid with wooden planks. In this photo, bamboos were used instead because it was more convenient to use bamboos in this situation. The government has published a guideline colloquially called “blue-cover book”, which requires the area of a work platform for building construction and renovation to be 0.4 meters in breadth. There is no stipulation for other types of work platform. Mr Chan recalled that a work platform had to be 4 to 5 metres in breadth for holding a large construction machine.
The mechanics of trigonometry
Mr Chan explained the mechanics of scaffolding from trigonometry.
A simple scaffold for Chinese opera performance
A scaffold for Chinese opera is different from other types of scaffold. It is a house-like structure built on a large piece of open area according to a designated design. In the whole of Hong Kong, there are only 2-3 scaffolding companies specializing in this kind of scaffold as orders only come during peak seasons. A scaffold of this type is characterized by a wide front, with two bamboos setting on the left and the right each. One is called tiger door “cheung” and the other called wolf tooth “cheung”.