A History of Research and a Review of Recent Developments
A History of Research and a Review of Recent Developments
A History of Research and a Review of Recent Developments
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Civil bridges 191<br />
externally a distance <strong>of</strong> 10 ft from the wall would not seriously damage it. It<br />
should be noted that these early experiments were made with no venting to<br />
reduce the degree <strong>of</strong> confinement.<br />
Glass <strong>and</strong> light sheeting in buildings are very damage-prone under the action<br />
<strong>of</strong> blast loads or penetrators. Unless treated on the surface by the addition <strong>of</strong><br />
film or mesh, glass will rapidly shatter <strong>and</strong> be transformed into high-speed<br />
splintered fragments. Light sheeting will tear <strong>and</strong> distort if made from ductile<br />
materials, or shatter like glass if made from brittle materials. The loading will<br />
be not unlike that calculated for similar areas <strong>of</strong> brickwork, but the effects <strong>of</strong><br />
the blast will be felt over larger areas.<br />
Damage from terrorist bombs in the commercial areas <strong>of</strong> cities can be<br />
widespread <strong>and</strong> expensive to repair. Readers will have seen photographs <strong>of</strong><br />
the distortion <strong>and</strong> tearing <strong>of</strong> cladding on high rise <strong>of</strong>fices <strong>and</strong> the shattering <strong>of</strong><br />
glass in the windows <strong>of</strong> shops <strong>and</strong> public buildings. In analysing the results <strong>of</strong><br />
this form <strong>of</strong> blast loading, it is usually assumed that the instantaneous pressures,<br />
<strong>and</strong> the pressure decay, are similar to those experienced by flat areas <strong>of</strong> masonry,<br />
brickwork or reinforced concrete.<br />
8.2 CIVIL BRIDGES<br />
Explosive damage to civil bridges has occurred in the past as a result <strong>of</strong> military<br />
operations, either in an attacking mode when for tactical reasons it has been<br />
necessary to demolish bridges by bombing, artillery shells, rockets or cruise missiles;<br />
or in a defensive situation where the demolition <strong>of</strong> a bridge prevented the enemy<br />
from advancing along a planned route. Defensive demolition was normally carried<br />
out by the emplacement <strong>of</strong> cutting charges on selected bridge members.<br />
Bridge damage can also occur from non-military disasters such as vapour<br />
cloud explosions, tanker explosions following collisions, fuel explosions<br />
following the crashing <strong>of</strong> aircraft, or fuel explosions following earthquakes.<br />
Instances have been recorded <strong>of</strong> damage due to terrorist activities, mainly<br />
relatively slight damage to decks <strong>and</strong> truss members.<br />
One <strong>of</strong> the most informative investigations into bomb damage (from aerial<br />
bombs) on large civil bridges was made by a UK Ministry <strong>of</strong> Home Security<br />
team in 1944 for the British Bombing <strong>Research</strong> Mission. When the Allied armies<br />
were fighting in Norm<strong>and</strong>y after D-day heavy air attacks were made on road<br />
<strong>and</strong> rail bridges over the River Seine to prevent supplies reaching the German<br />
divisions. After the Allied advance over the Seine <strong>and</strong> on to the Rhine <strong>and</strong> its<br />
tributaries in September 1944, there was a chance to investigate the levels <strong>of</strong><br />
damage to the Seine bridges. Many <strong>of</strong> the bridges (<strong>and</strong> the majority were rail<br />
bridges) were damaged three times during the Second World War; firstly when<br />
the French authorities demolished parts <strong>of</strong> bridges in 1940, secondly by the<br />
very severe bombing in mid-1944, <strong>and</strong> thirdly by the German army during the<br />
retreat from Norm<strong>and</strong>y <strong>and</strong> Northern France in the autumn <strong>of</strong> 1944. The reports<br />
<strong>of</strong> the team <strong>of</strong> structural experts, originally secret, are now unclassified, <strong>and</strong> air