Fire suppression systems, specifically for fully sprinklered buildings, have dramatically decreased the number of fire-related deaths over the years. Fire containment and suppression by sprinkler systems limit the spread of fire and increase evacuation time available for building occupants.
Sprinkler and standpipe systems are often combined, although the extent of piping used for sprinkler systems is far greater than piping used for standpipes. Sprinkler coverage requires that vertical riser piping and branch piping extend to all areas of each building floor.
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Continuing last articles about concrete construction, the rest of it are brisance and limited ductility. Cement-based materials exhibit a relatively low tensile strength, compression strength. When subjected to high pressures, concrete is susceptible to brisance, disintegration of the concrete.
Reinforced concrete structures can exhibit tremendous ductility or virtually none at all. The ductility resides in the details of reinforcement. Therefore, concrete structures may be susceptible to non-ductile modes of failure due to abnormal loads. Assessment of concrete structures should include a review of the details such as the arrangement of reinforcement in joints, at splices, and at anchorage points. Any improvement in detailing similar to those used in seismic design guides will enhance
building performance under abnormal loads.
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Three aspects of concrete construction are often vulnerable to failure and should be carefully evaluated shear failure, brisance, and limited ductility. Shear failure will occur when the shear force exceeds the shear strength of a member. Steel ties, stirrups, and spirals are used to reinforce concrete columns and beams, providing additional strength to supplement the relatively weak concrete shear strength.
Like the concrete shear strength, the concrete tensile strength or resistance to tension or pulling is also weak. Therefore, concrete elements are susceptible to a brisance failure from the effects of blast or impact. Furthermore, concrete is an inherently brittle material. Without steel or composite fiber reinforcement, the concrete will not sustain deformations typical of more ductile materials such as steel and iron. In general, concrete is used in construction because it is an inexpensive and readily available material with good compressive strength. Shear failure, brisance, and ductility are less dependent upon compressive strength and must be prevented from dominating the behavior.
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In addition of previous articles discussing on building resistance, structure redundancy is also need to be consider on designing a building. Structural systems must be capable of transferring load to supports or the ground. For a structure to be stable, at least one load path capable of carrying loads must exist within the structure.
The load path must satisfy strength demands and static equilibrium. The structure must be restrained from moving as a rigid body or linkage. If the load path is interrupted, due to the effects of a bomb or blast, then the structure will collapse if no alternate load path is available. Redundancy in load paths allows redirection of loads to alternative load paths. This maintains structural integrity, should one load path fail.
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Building risk assessment is important in order to know all aspect that could measure the load or capacity of the building itself. Abnormal loads on buildings may be caused by vehicular impact, blast loads from accidental or purposeful explosions, or local failure due to fire. Once the threat is defined, the structure must perform to a level consistent with established performance criteria, such as preventing structural collapse of part or all of the building.
Protection against abnormal loads incurs cost. To maximize the benefit of protection expense, the first step is determining where protection is needed. This is based on the assets housed in a building and the structural capabilities required for asset protection.
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