How to Design Buildings Against Terrorist Attacks

• Vehicle weapon
• Hand-delivered weapon Airborne Chemical, Biological, and Radiological Threats:
• Large-scale, external, air-borne release
• External release targeting building
• Internal release

• Provide a continuous line of defense around the site as far from the building as practical.
• Place vehicular access points away from oncoming streets.
• Limit the number of vehicular entrances through the secured perimeter line
• Use a series of landscape features to create an obstacle course between the building and the perimeter. This approach is most effective if used in areas where there is ample setback.
• Design planters for the design-level impact to displace the planter a distance less than the setback.
• Use anti-ram barriers along curbs, particularly on sides of the building that have a small setback and in areas where high-velocity impact is possible.
• Use operable anti-ram barriers at vehicular access points. Select barriers rated to provide the desired level of protection against the design impact.

• Use simple geometries without sharp re-entrant corners.
• Use lightweight nonstructural elements to reduce flying debris hazards.
• Place the building on the site as far from the perimeter as practical.
• Place unsecured areas exterior to the main structure or along the exterior of the building.
• Separate unsecured and secured areas horizontally and vertically using buffer zones and/or hardening of walls and floors.
• Provide sufficient queuing areas at lobby and delivery entrances.
• Limit nonstructural elements such as false ceilings and metal blinds on the interior.
• Mechanically fasten light fixtures to the floor system above.
• Place desks and conference tables as far from exterior windows as practical.
• Orient desks with computer monitors to face away from windows so the chair back faces the window, not the monitor.

• Incorporate measures to prevent progressive collapse.
• Design floor systems for uplift in unsecured areas and in exterior bays that may pose a hazard to occupants.
• Limit column spacing.
• Avoid transfer girders.
• Use two-way floor and roof systems.
• Use fully grouted, heavily reinforced CMU block walls that are properly anchored in order to separate unsecured areas from critical functions and occupied secured areas.
• Use dynamic nonlinear analysis methods for design of critical structural components.

The following is the Building Envelope check list.

Cladding

• Use the thinnest panel thickness that is acceptable for conventional loads.
• Design cladding supports and the supporting structure to resist the ultimate lateral resistance of the panel.
• Design cladding connections to have as direct a load transmission path into the main structure as practical. A good transmission path minimizes shear and torsional response.
• Avoid framing cladding into columns and other primary vertical load-carrying members. Instead frame into floor diaphragms.

Windows

• Use the thinnest glass section that is acceptable for conventional loads.
• Design window systems so that the frame anchorage and the supporting wall are capable of resisting the breaking pressure of the window glass.
• Use laminated annealed glass (for insulated panels, only the interior panel needs to be laminated).
• Design window frames with a minimum of a ½-inch bite.
• Use a minimum of a ¼-inch silicone sealant around the inside glass perimeter, with a minimum tensile strength of 20 psi.

• Place all emergency functions away from high-risk areas in protected locations with restricted access.
• Provide redundant and separated emergency functions.
• Harden and/or provide physical buffer zones for the enclosures around emergency equipment, controls, and wiring.
• For egress routes, provide battery packs for exit signs, use non-slip phosphorescent treads, and double doors for mass evacuation.
• Avoid using glass along primary egress routes or stairwells.
• Place emergency functions away from structurally vulnerable areas such as transfer girders.
• Place a transformer interior to building, if possible.
• Provide access to the fire control center from the building exterior.

• Place air intakes servicing occupied areas as high as practically possible (minimum 12 feet above ground). GSA may require locating at fourth floor or above when applicable.
• Restrict access to critical equipment.
• Isolate separate HVAC zones and return air systems.
• Isolate HVAC supply and return systems in unsecured areas.
• Physically isolate unsecured areas from secured areas.
• Use positive pressurization of primary egress routes, safe havens, and/or other critical areas.
• Commission building throughout construction and prior to taking ownership.
• Provide redundant, easily accessible shutdown capabilities.
• For higher levels of protection, consider using contaminant-specific filtration and detection systems.
• Incorporate fast-acting, low-leaking dampers.
• Filter both return air and outdoor air for publicly accessible buildings.
• Select filter efficiencies based upon contaminant size. Use reputable filter media installed into tight-fitting, gasketed, and secure filter racks.
• For higher threat areas (mail room, receiving, reception/screening lobby):
  • Preferably locate these areas outside the main building footprint.
  • Provide separate HVAC, with isolated returns capable of 100% exhaust.
  • Operate these areas at negative pressure relative to secure portion of the building.
  • Use air-tight construction, vestibules, and air locks if there is high traffic flow.
  • Consider installation of an emergency exhaust fan to be activated upon suspected internal CBR release.
• Lock, secure, access-log, and control mechanical rooms.
• In public access areas, use air diffusers and return air grills that are secure or under security observation.
• Zone the building communication system so that it is capable of delivering explicit instructions, and has back-up power.
• Create safe zones using enhanced filtration, tight construction, emergency power, dedicated communication systems, and appropriate supplies (food, water, first aide, and personal-protective equipment).