Flashcards in Chapter 11- Fire Resistive Construction Deck (28)
The problems that fire departments face regarding concrete construction can be divided into three distinct areas:
-Collapse during construction with no fire
-Fire during construction
-Fire in completed, occupied buildings
For any unit area, steel has __ times the compressive strength of concrete. Steel is, however, more costly.
Autoclaved Aerated Concrete Units (AAC) may be formed into panels, blocks, and floor slabs. It can be cut easily, thereby obtaining the desired dimensions. In terms of fire protection, the material has held up well when tested in an American Society for Testing and Materials (ASTM) E-119 furnace, achieving a __ hour rating with an __ inch thick block wall.
A major advantage of __ __ is that the floors can be thinner. Thinner floors will allow several more rentable floors in a tall building.
There is an economic limit to the height of an ordinary brick bearing wall building. This exists because of the requirement that the walls increase in thickness as the building's height increases. The limit is generally about __ stories, but there are brick bearing wall buildings as tall as __ stories.
In recent years, it has become possible to build brick bearing wall buildings __ or more stories in height, with no wall thicker than __ inches.
Concrete poured at __ degrees F will develop __ more pressure than at __ degrees F.
Sometimes workers burn scrap wood in steel barrels or use kerosene heaters to keep warm. By far the most dangerous, and perhaps most common heating method is the use of __.
Liquefied petroleum gas (LPG)
__ __ structures include bridges and parking garages. Post tensioned concrete presents a greater catastrophic collapse hazard during a fire than does conventional __ concrete.
Fireproofing of steel is classified as __ or __.
__ fireproofing provides protection for each piece of steel.
__ fireproofing does not protect individual members. In one method, wire lath and cement plaster are used. In another method, the fireproofing of the floor is accomplished by a rated floor--ceiling assembly.
The disadvantage of concrete is it __. In the effort to reduce dead weight of a building, and thus its cost, fireproofing is often a tempting target.
One of the fire protection advantages of concrete construction is that it lacks __ voids.
The concrete in fire resistive construction serves two purposes;
-It resists compressive stresses.
-It protects the tensile strength of steel from fire.
A cast in place, __ concrete building is resistant to collapse.
Problems with a reinforced concrete column or floor are not so obvious during a fire. It is equally important to anticipate collapse based upon conditions such as:
-Knowledge of problematic existing building conditions (poor fireproofing, vulnerable connections, etc).
-Dangerous loads (concentrated, heavy, etc.).
-Cutting tensioned cables.
-Heavy fire conditions over an extended period of time; such fire conditions will ultimately cause any building (or portion of a building) to collapse, regardless of construction type.
At a fire, it is impossible for the company officer to know if he is dealing with normal strength concrete (NSC), or high strength concrete (HSC). NSC loses about __ percent of its compressive strength at about __ degrees F and __ percent of its compressive strength at about __ degrees F.
575 degrees F
11007 degrees F
__ loses much more strength than NSC in the same temperature ranges.
Small devices designed to keep the rods up off the surface of the form so concrete will flow underneath.
Thicker section of floor on top of columns to assist in resisting the natural tendency of the floor to shear off at the column.
Cast in place floor in which there are no beams supported by columns; the floor plate itself rests directly on the columns.
Flat plate structural system
Tile unit composed of vertical hollow cells, utilized in early efforts to lighten concrete floors.
Steel pipes filled with concrete to increase their load carrying capacity.
Planks on which formwork shores rest.
Tapered extension at the tops of columns that assists in the transfer of loads from floor to column.
Shores that are put back into concrete to help carry the load of the still curing concrete.