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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192<br />
The effects <strong>of</strong> explosive loading<br />
photographs <strong>of</strong> the destruction have been released by the UK Public Record<br />
Office <strong>and</strong> reproduced by Her Majesty’s Stationery Office. The report on the<br />
Seine bridges [8.19] was in four parts <strong>and</strong> one <strong>of</strong> the authors was Dr Frances<br />
Walley. Dr Walley, as a young scientist <strong>and</strong> engineer, carried out many research<br />
projects during the Second World War in support <strong>of</strong> the <strong>Research</strong> <strong>and</strong> Experiments<br />
Department <strong>of</strong> the UK Ministry <strong>of</strong> Home Security. Much <strong>of</strong> his outst<strong>and</strong>ing<br />
work is still relevant, <strong>and</strong> he has recently published a valuable paper on the<br />
wartime efforts by himself <strong>and</strong> others in support <strong>of</strong> the need to underst<strong>and</strong> the<br />
fundamentals <strong>of</strong> the effect <strong>of</strong> explosive forces on structures [8.20].<br />
The Seine bridges report makes the general point that continuous girder<br />
bridges are very resistant to collapse by bombing, <strong>and</strong> that in many positions<br />
the main girders <strong>of</strong> such bridges can be severed without concomitant collapse<br />
<strong>of</strong> the entire structure. There is a usually generous allowance in design to<br />
cover redistribution <strong>of</strong> forces <strong>and</strong> moments due to cuts under dead load<br />
conditions only. To guarantee collapse it was usually necessary to cut two<br />
main booms in the same bay. It was also clear from the survey that the most<br />
vulnerable components <strong>of</strong> heavy girder bridges were the piers. Masonry arches<br />
were found to suffer greater local damage from single hits, but the spans were<br />
less <strong>and</strong> temporary repairs were more readily carried out. The number <strong>of</strong> hits<br />
was very low on the Seine bridges. For every 100 bombs released in all types<br />
<strong>of</strong> attack (high level <strong>and</strong> low level) three direct hits were scored, two on the<br />
superstructure, one on the supports.<br />
The study concluded that for railway girder bridges the most efficient general<br />
purpose bombs were 2000 lb in total weight, <strong>and</strong> for road girder bridges 1000<br />
lb bombs were more appropriate. For masonry arch bridges the effectiveness<br />
<strong>of</strong> the bombs varied with span, from 1000 lb bombs (0 to 50 ft), to 2000 lb<br />
(50 to 100 ft). Although there were instances <strong>of</strong> 500 lb bombs being effective<br />
between 0 <strong>and</strong> 50 ft span, the use <strong>of</strong> 1000 lb bombs was thought to be preferable.<br />
High-level attack with instantaneous fusing <strong>of</strong> the bombs was recommended<br />
for girder bridges, <strong>and</strong> low-level attack with delayed fusing for masonry arches.<br />
The Bombing <strong>Research</strong> Mission ascertained the effect <strong>of</strong> bombs <strong>of</strong> known<br />
weight across the Seine between Paris <strong>and</strong> Rouen. Ten railway girder bridges,<br />
nine railway arches, five road girders <strong>and</strong> three road arches were examined.<br />
In terms <strong>of</strong> residual strength, rapid repair <strong>and</strong> speedy re-use, some <strong>of</strong> the<br />
bridges examined provide useful information. We will look at these in turn:<br />
(a) d’Eauplet bridge (railway) at Rouen, Figure 8.2.<br />
The bombing history was as follows:<br />
7 May 1944 70×1000 GP bombs No damage<br />
25 May 1994 54×500 GP bombs No damage<br />
25 May 1944 8×500 GP bombs No damage<br />
27 May 1944 45×1000 GP bombs Pier 3 severely shaken<br />
28 May 1944 46×1000 GP bombs Pier 3 hit again, causing complete<br />
20×500 GP bombs destruction.