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History of construction – a backdrop for the innovations of the past century

The history of building is marked by a number of trends. One is the increasing durability of the materials used. Early building materials were perishable, such as leaves, branches, and animal hides.

Later, more durable natural materials such as clay, stone, and timber, and, finally, synthetic materials, such as brick, concrete, metals, and plastics were used.

Another is a quest for buildings of ever greater height and span; this was made possible by the development of stronger materials and by knowledge of how materials behave and how to exploit them to greater advantage.

A third major trend involves the degree of control exercised over the interior environment of buildings: increasingly precise regulation of air temperature, light and sound levels, humidity, odors, air speed, and other factors that affect human comfort has been possible.

Yet another trend is the change in energy available to the construction process, starting with human muscle power and developing toward the powerful machinery used today.

Why reinforced concrete matters so much

Reinforced Concrete played an important part in building America and It’s Industry

Concrete and steel in useful, economic quantities were first developed in the 1800s.

Joseph Monier obtained his second patent related to reinforced concrete in 1877. He used it in the making of flowerpots. Specifically, before concrete is poured into a form, rebar is added inside the form where the resulting structure would experience tensile forces. The rebar is a twisted spiral rod so that the concrete can “grip” it better after it sets. (Other types of reinforced concrete that use other tension resistant materials are being developed, but steel is still the most typical companion material.)

Steel and concrete have similar coefficients of thermal expansion so internal stresses remain low as the temperature of the reinforced concrete changes. The concrete must be mixed correctly to make sure the steel does not rust. Rust expands, and it will crack the concrete.

When the Delaware,viaduct Lackawanna & Western Railroad built a 28.5-mile cutoff between 1908 and 1911, it used reinforced concrete for all of its structures.

The Paulinskill Viaduct was 115 ft tall and, at the time it was built, the world’s largest reinforced concrete structure.

“When the timbers start talkin, the miners start walkin”

Abandoned coal mines tell a story.

When you enter one of these derelict mines you often see these sections of trees that are referred to as timbers or props.

Contrary to popular mine timbersbelief these timbers offered little or no roof support.

Instead, these timbers were used as a warning, “when the timbers start talkin, the miners start walkin”.

If a section of the roof began to sag, the wieght would press down on these timbers, they would begin cracking, popping, and sweating as the pressure squeezed the sap out.

When these warning signs were observed, the area was hopefully evacuated until the section of roof fell in a controlled or uncontrolled manner. Wedged at the top, tapered and set on the bottom, they were set very snug to prevent kicking out if pressure was applied.