11. Look at this diagram and read the passage.

Let's look closely at this drawing of a structure. It's an example of an arcuated struc­ture and it's called a segmental arch. It's given that name because it's shaped like the segment of a circle. Now arcuated structures have one big advantage: they can be used to span openings with components smaller in size than the width of the open­ing. As you can see, bricks are used as the components for this arch and each one is a lot smaller than the width of the opening. The bricks have been formed into a wedge shape. This is done so that their weight is distributed downwards along the curve of the arch. In this way, the bricks support each other over the opening. When the arch is constructed, the last bricks placed in position are the keybricks. They're located at the top or crown of the arch and they lock the other bricks in position. The joints, here, here, and so on, are between the bricks at right angles to the curve of the arch. They are filled with mortar made of cement and sand. Now mortar is strong in compression but weak in tension. However, all the forces in an arch must be compressive, so that the mortar does not take any tensile forces. An earthquake may move the arch and cause tensile forces in it. If this happened then the arch would fall down. Because of this, I suggest you don't walk under an arch during an earthquake.

Now copy and complete these notes:

Name of structure	… arch
Reason for name	shaped like … of …
Advantage of structure	can use components … than … of opening
Shape of components	…
Reason for shape	bricks … each other
Name of last brick	…
Position of joints	between … at … to curve
Material of mortar	… and …
Type of forces in arch	…
If tensile forces	arch will … …

Chapter 11. The design mistakes

1. Look and read.

All buildings enclose space. Buildings always/invariably enclose space. Nearly all people live in houses. People nearly always live in houses. Most buildings have windows. Buildings usually/generally have windows. Many architects work in a design team. Architects often/frequently work in a design team. Some buildings have air conditioning. Buildings sometimes have air conditioning. Few people build their own houses. People occasionally build their own houses. Few people live in very cold climates. People rarely/seldom live in very cold climates. Very few buildings are portable. Buildings are very rarely/seldom portable. No building last forever. Buildings never last forever.

Now complete these statements by starting with one of the following:

all, nearly all, most many, some, a few, few, very few, no.

1. Architects have studied architecture at university.

2. Buildings have entrances on the ground floor.

3. Bridges are built of concrete.

4. Buildings have doors.

5. People live in cities.

6. Blocks of flats are over 50 meters high.

7. Architects are self-employed.

8. Houses are prefabricated.

9. Shops are accessible by car.

10. Buildings are built on rock foundations.

11. People are taller than 1-8 meters.

12. Factories have solid walls.

13. Buildings are designed to keep out the weather.

14. Hotels are completely fireproof.

15. Buildings are two dimensional.