5 April 2002
Source: http://www.unesco.org/webworld/archives/sro_citra/ER4.html

Expert Report 4: Military Engineering and Building Hardening

Major Martin Morris, Royal Engineers, UK

Introduction

In the event of armed conflict infrastructure will probably be either disrupted, non-existent or poor; buildings will vary from large centres of population to simply constructed rural dwellings. It is therefore not possible to produce comprehensive guidelines which will cover all situations.

The Threat

It is assumed that any requirement to protect archives would be during or following conventional armed conflict. Typical weaponry could include:

• Small arms from 5.56mm to 7.62mm.
• Artillery fire from 122mm to 155mm.
• Mortar fire to 81mm.

These threats are not exhaustive but represent a typical, most likely scenario. It must be remembered that damage from munitions will usually be followed by a fire. Water should be stored not only for drinking and cooking but also for fire fighting.

Physical Protection

In the event of attack the primary aim must be to save life. A second priority would be to preserve vital supplies such as water and food. A third priority might be to protect key assets such as communication facilities. The protection of archives may not be allocated a high priority and therefore would often not be allocated significant resources. It is vital that best use is made of commonly available materials.

Within buildings or complexes, designated refuge areas for personnel should be created in structurally stronger parts of the structure. Examples could include:

Cellars.

Adjacent to lift shafts.

Next to chimney breasts in smaller structures.

 

Particularly valuable or sensitive archival material could be stored in such areas.

Strengthening and Hardening

Strengthening can be defined as measures to increase the overall strength and stability of a structure whereas hardening is concerned with minimising damage to a particular part of a structure.

Expedient Strengthening

Most industrial and domestic framed buildings are remarkably resilient to blast damage. Simple measures to increase survivability of both framed and non framed buildings include:

Prop ceilings and roofs using proprietary propping systems or improvised steel or timber props and folding wedges. When using timber and where the ceiling is not more than three metres from the floor the props should be 120mm square or 120mm diameter, or larger. They should be spaced not more than 1.5m apart. Wooden wedges will be needed to ensure that the props are a tight fit when installed. In addition, timber spreaders must be used, as illustrated, to ensure that the load is properly transmitted from ceiling to floor and to avoid point loading which overstresses the ceiling.

Adding more stability to structures by adding diagonal, raking members to support corner pillars.

Expedient Hardening

General

The sandbag is most useful. Sandbags filled with locally won material may be used to harden walls and roofs. As a general rule 1m of soil will stop most fragments. If roofs are flat at least 350mm of sandbags (i.e. three thick) should be provided. Care should be taken to ensure the roof is not dangerously overloaded.

• Windows

  Windows are generally the weakest part of a structure and are particularly vulnerable to fragments and from aimed direct fire weapons. Simple hardening measures could include:

• Block up (brick, block, board or sandbag) all unnecessary windows,
• Reduce the size of those considered essential by partially boarding up.
• Remove the glass from windows; flying glass is a major cause of injury.

If time and resources are available consider:

• Replacement of glass with perspex or similar
• Application of purpose made anti shatter film.

• Doors and Entrances

  Personnel are particularly vulnerable to small arms fire when entering or leaving a building. Opening a door may give an attacker line of sight into a building. Simple hardening measures could include:

• Block up unnecessary exits and entries, but remember the fire risk!
• Keep doors closed when not in use. Consider using horizontal removable beams to increase blast resistance.
• Add material to the outside of the door to increase ballistic resistance. Wood or metal plates could be used.
• Simple cover from view structures in front of doors. These could be of masonry or even earth, but could be light textiles on a suitable frame. The aim is to obscure line of sight.
• Rehang the door to open outwards to increase blast resistance.
• Reinforce the door jambs to reduce the span of the door.

• Walls

  A concrete wall generally provides good ballistic and blast resistance. Blockwork walls may be hardened by:

• Mounding up earth outside the building. It is only necessary to provide protection to about 1m height to give adequate protection for personnel. It is assumed that personnel will lie down if under bombardment. This material could be loose but would preferably be in wire mesh baskets such as those used in flood relief and prevention of river bank erosion.
• Tea chests or any reasonably solid boxes could be used.
• A 1m thickness of earth gives very good protection against fragments from air delivered weapons. Care should be taken to provide adequate foundation material and to avoid overloading.
  

Building protected by sandbags and gabions US base- Bosnia - Nov 97 Photo by DERA Chertsey Prop tree trunks against the outside of the wall. Wood is particularly good at stopping fragments. Fabric could be glued to the inside of the wall. A geofabric such as those used in road construction or even a heavy woven fabric such as a carpet increases blast resistance. Decreasing the span of wall sections by improvised pillars or pilasters.

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