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STRUCTURAL RISKS : 1.4

“ The human body is capable of surviving .. pressures higher than what conventionally constructed buildings will commonly survive. It is commonly, failed building components or building debris such as walls and columns or being thrown into building interiors, that injures people.” (DOD 2013).

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STRUCTURAL RISKS : 1.4

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  1. “The human body is capable of surviving .. pressures higher than what conventionally constructed buildings will commonly survive. It is commonly, failed building components or building debris such as walls and columns or being thrown into building interiors, that injures people.” (DOD 2013) STRUCTURAL RISKS : 1.4 NATURAL DISASTERS FIRE BLASTS K. COLLATERAL DAMAGE L. RIOTS OR CIVIL UNREST WEAPON OF MASS DESTRUCTION STRUCTURAL FAILURE “..objective is to reduce the probability that the building itself becomes a hazard in an explosion Preventing cascading events due to loss of control of process….. an incident in 1 unit should not affect the continued safe operation of other units. Minimising financial losses Building containing… critical equipment ... should be protected.” (Jomyn.d.) • STUDY STRUCTURAL ACTION • REDUCE THE SEVERITY OF INJURY • FACILITATE RESCUE • EXPEDITE REPAIR • ACCELERATE RETURN TO FULL OPERATION.

  2. EXPLOSIVE REACTION : 1.4.1 • BLAST WAVES - SUPERSONIC SPEEDS • - REFLECTIONS- MAGNIFY • - DIMINUTION WITH DISTANCE

  3. AIR SHOCK WAVES INITIAL REFLECTED QUASI BLAST WAVE STRUCTURAL ACTION : 1.4.3 GROUND SHOCK WAVE SURFACE/RALEIGH WAVE GROUND COMPRESSION RADIAL SHEAR WAVE • WAVE PROPERTIES: • MULTI DIRECTIONAL • DIFFERENT MAGNITUDES • DIFFERENT FREQUENCIES • = UNPREDICTABLE • = LOAD REVERSALS • = EXTREME SHEAR PRESSURES OVER A SHORT PERIOD • INSTANTANEOUS IMPACT ON: • STRUCTURAL SYSTEM & COMPONENTS VARYING AS/PROXIMITY • FAÇADE & OTHER INSTALLATIONS • FRAGMENTATION, DISMOUNTING, THROWING AROUND

  4. “Frame buildings designed to resist gravity, wind loads and earthquake loads in the normal way have frequently been found to be deficient in 2 respects: • Failure of beam to column connections • Inability to tolerate load reversal.” • (ZeynepKoccaz 2008) STRUCTURAL REACTION : 1.4.4 COLLAPSE LIMIT DESIGN: AVOID OVERALL COLLAPSE THOUGH BUILDING CANNOT FUNCTION ANYMORE FUNCTIONALITY LIMIT DESIGN : CONTINUE FUNCTIONALITY

  5. “Addressing blast & seismic design goals may be achieved….An understanding of the differences between these 2 loading phenomenon, effects on the structure and performance requirements are essential to select and implement the appropriate choices..” (WBDG 2014) SEISMIC VS BLAST “ Progressive collapse is defined as the spread of an initial local failure from element to element, eventually resulting in the collapse of an entire structure or disproportionately large part of it. The initial failure or damage could be from a number of different causes, which might include natural or man-made hazards…” (ASCE 7, WBDG 2014)

  6. “Blast loads are dynamic loads that need to be carefully calculated, just like earthquake and wind loads” (ZeynepKoccaz 2008) • More attention to design and detailing of structural components • Must for exterior bays and lower floors of buildings • Shorten slab lengths and improve the punching shear resistance.” • Appropriate detailing of slab-column interface. • Bottom reinforcement in slabs continuous through column • Continuously tied reinforcements in both directions • Anchorage of reinforcement at edge of slab • Beam to beam connections • Beam to column connections. • Potential for direct lateral loading on face of columns • Adequate ductility and strength. • Encasing lower floor columns in steel jackets or steel belts or CFRP • Embed steel column within perimeter concrete columns or walls • For smaller loads columns and walls with spiral reinforcements. • Possibility of uplift • Columns designed for transient tensile forces. • Progressive collapse analysis • Hardening- • Several shear walls -beneficial for seismic design also. • Central shear wall with a peripheral movement resisting frame.” • (Jomyn.d.) RESILIENT STRUCTURES : 1.4.5

  7. BLAST WAVE= HEMISPHERICAL SHOCK WAVE • AMPLIFIED BY REFLECTION • MULTI DIRECTIONAL • “ DECAY AS FUNCTION OF DISTANCE FROM SOURCE. • DIMINISH WITH ANGLE OF OBLIQUITY TO SOURCE” “Designing structures to be fully blast resistant is not a realistic and economical option, however current engineering and architectural knowledge can enhance the new and existing buildings to mitigate the effects of an explosion”(Zeynep Koccaz 2008) ARCHITECTURAL DEDUCTIONS : 1.4.6 & STRATEGY : 1.4.7 • MINIMISE • CATASTROPHIC FAILURE • EFFECT ON BUILDINGS & ITS OCCUPANTS • FLYING DEBRIS • MAIN STRUCTURAL CONCERNS • FAILED BUILDING COMPONENTS • FLYING DEBRIS • OCCUPANTS AND PROPERTY BEING THROWN AROUND • MEP FAILURE DUE TO DETACHMENT FROM MOUNTING OR STRUCTURAL ATTACHMENT. • PROGRESSIVE TOTAL STRUCTURAL COLLAPSE • FIRE & SMOKE • PANIC AND STAMPEDES • COUNTER DESIGN STRATEGY • EXPLOSIVE WEIGHT • DISTANCE FROM SOURCE • STRUCTURAL FORM • STRUCTURAL HARDENING • ISOLATION OF ASSET • MATERIAL SELECTION- FAÇADE & INTERIORS

  8. “ Probability that the one or more threats will occur is based on historical data extrapolated to the future and considerable probabilistic acumen applied to the time and place of the project in question.”(Demkin n.d.) SECURITY PROGRAMMING I 1.5

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