建築

(while building materials have changed dramatically.)

while building materials have changed dramatically.

(The world's architectural structures have also been devised)

The world's architectural structures have also been devised

(in relation to the objective limitations of materials.)

in relation to the objective limitations of materials.

(Structures can be analyzed in terms of how they deal with downward forces created by gravity.)

Structures can be analyzed in terms of how they deal with downward forces created by gravity.

(They are designed to withstand the forces of compression (pushing together), tension (pulling apart),)

They are designed to withstand the forces of compression (pushing together), tension (pulling apart),

(bending, or a combination of these in different parts of the structure.)

bending, or a combination of these in different parts of the structure.

(Every development in architecture has been the result of major technological changes.)

Every development in architecture has been the result of major technological changes.

(Materials and methods of construction are integral parts of the design of architectural structures.)

Materials and methods of construction are integral parts of the design of architectural structures.

(In earlier times, it was necessary to design structural systems suitable for the materials)

In earlier times, it was necessary to design structural systems suitable for the materials

(that were available, such as wood, stone, or brick.)

that were available, such as wood, stone, or brick.

(Today, technology has progressed to the point)

Today, technology has progressed to the point

(where it is possible to invent new building materials to suit the type of structure desired.)

where it is possible to invent new building materials to suit the type of structure desired.

(Enormous changes in materials and techniques of construction within the last few generations)

Enormous changes in materials and techniques of construction within the last few generations

(have made it possible to enclose space with much greater ease and speed and with a minimum of material.)

have made it possible to enclose space with much greater ease and speed and with a minimum of material.

(Progress in this area can be measured by the difference in weight between buildings built now)

Progress in this area can be measured by the difference in weight between buildings built now

(and those of comparable size built one hundred years ago.)

and those of comparable size built one hundred years ago.

(Modern architectural forms generally)

Modern architectural forms generally

(have three separate components comparable to elements of the human body:)

have three separate components comparable to elements of the human body:

(a supporting skeleton or frame, an outer skin enclosing the interior spaces,)

a supporting skeleton or frame, an outer skin enclosing the interior spaces,

(and equipment similar to the body's vital organs and systems.)

and equipment similar to the body's vital organs and systems.

(The equipment includes plumbing, electrical wiring, hot water, and air conditioning.)

The equipment includes plumbing, electrical wiring, hot water, and air conditioning.

(Of course, in early architecture, such as igloos and adobe structures, there was no such equipment,)

Of course, in early architecture, such as igloos and adobe structures, there was no such equipment,

(and the skeleton and skin were often one.)

and the skeleton and skin were often one.

(Much of the world's great architecture has been constructed of stone because of its beauty,)

Much of the world's great architecture has been constructed of stone because of its beauty,

(permanence, and availability.)

permanence, and availability.

(In the past, whole cities grew from the arduous task of cutting and piling stone upon stone.)

In the past, whole cities grew from the arduous task of cutting and piling stone upon stone.

(Some of the world's finest stone architecture can be seen)

Some of the world's finest stone architecture can be seen

(in the ruins of the ancient Inca city of Machu Picchu, high in the eastern Andes Mountains of Peru.)

in the ruins of the ancient Inca city of Machu Picchu, high in the eastern Andes Mountains of Peru.

(The doorways and windows are made possible by placing thick stone beams)

The doorways and windows are made possible by placing thick stone beams

(over the open spaces that support the weight from above.)

over the open spaces that support the weight from above.

(A structural invention had to be made before the physical limitations of stone)

A structural invention had to be made before the physical limitations of stone

(could be overcome and new architectural forms could be created.)

could be overcome and new architectural forms could be created.

(That invention was the arch, a curved structure originally made of separate stone or brick segments.)

That invention was the arch, a curved structure originally made of separate stone or brick segments.

(The arch was used chiefly for underground drains by the early cultures of the Mediterranean area,)

The arch was used chiefly for underground drains by the early cultures of the Mediterranean area,

(but it was the Romans who first developed and used the arch extensively in aboveground structures.)

but it was the Romans who first developed and used the arch extensively in aboveground structures.

(Roman builders perfected the semicircular arch made of separate blocks of stone.)

Roman builders perfected the semicircular arch made of separate blocks of stone.

(As a method of spanning space, the arch can support greater weight than a horizontal beam.)

As a method of spanning space, the arch can support greater weight than a horizontal beam.

(It works in compression to divert the weight above it out to the sides,)

It works in compression to divert the weight above it out to the sides,

(where the weight is borne by the vertical elements on either side of the arch.)

where the weight is borne by the vertical elements on either side of the arch.

(The arch is among the many important structural breakthroughs)

The arch is among the many important structural breakthroughs

(that have characterized architecture throughout the centuries.)

that have characterized architecture throughout the centuries.