The increase in the number of terrorist attacks especially in the recent years has shown that the effect of blast loads on buildings is a matter that should be taken into consideration in the design process. Although these kinds of attacks are exceptional cases, man-made disasters; blast loads are in fact dynamic loads that need to be carefully calculated just like earthquake and wind loads.
Planning And Layout
During the planning stage of a new building , potential threats and the associated risks of injury and damage can be reduced. The risk of a terrorist attack, necessity of blast protection for structural and non-structural members, adequate placing of shelter areas within a building should be considered for instance.
Structural Form and Internal Layout
Structural form is a parameter that greatly affects the blast loads on the building. Arches and domes are the types of structural forms that reduce the blast effects on the building compared with a cubicle form. The plan-shape of a building also has a significant influence on the magnitude of the blast load it is likely to experience. Complex shapes that cause multiple reflections of the blast wave should be discouraged. Projecting roofs or floors, and buildings that are U-shaped on plan are undesirable for this reason. Single story buildings are more blast resistant compared with multi-story buildings if applicable.
Partially or fully embed buildings are quite blast resistant. These kinds of structures take the advantage of the shock absorbing property of the soil covered by. The soil provides protection in case of a nuclear explosion as well.
The internal layout of the building is another parameter that should be considered. Foyer areas should be protected with reinforced concrete walls; double-dooring should be used and the doors should be arranged eccentrically within a corridor to prevent the blast pressure entering the internals of the building. Entrance to the building should be controlled and be separated from other parts of the building by robust construction for greater physical protection. An underpass beneath or car parking below or within the building should be avoided unless access to it can be effectively controlled.
Bomb Shelter Areas
The bomb shelter areas are specially designated within the building where vulnerability from the effects of the explosion is at a minimum and where personnel can retire in the event of a bomb threat warning. . For modern-framed buildings, shelter areas should be located away from windows, external doors, external walls and the top floors if the roof is weak.
Areas surrounded by full-height concrete walls should be selected and underground car parks, gas storage tanks, areas light weight partition walls, e.g. internal corridors, toilet areas, or conference should be avoided while locating the shelter areas. Basements can sometimes be useful shelter areas, but it is important to ensure that the building does not collapse on top of them. The functional aspects of a bomb shelter area should accommodate all the occupants of the building; provide adequate communication with outside; provide sufficient ventilation and sanitation; limit the blast pressure to less than the ear drum rupture pressure and provide alternative means of escape.
Gas, water, steam installations, electrical connections, elevators and water storage systems should be planned to resist any explosion affects. Installation connections are critical points to be considered and should be avoided to use in high-risk deformation areas. Areas with high damage receiving potential e.g. external walls, ceilings, roof slabs, car parking spaces and lobbies also should be avoided to locate the electrical and other installations. The main control units and installation feeding points should be protected from direct attacks. A reserve installation system should be provided for a potential explosion and should be located remote from the main installation system.