Frag Out! Magazine
Issue link: https://fragout.uberflip.com/i/1532587
One useful reference is STANAG 4623: Hard and Deeply Buried Targets, a NATO standard that categorizes fortified structures (from Category I to V) and provides guidance on how they should be protected. STANAG 4623 also offers a method for calculating the "concrete equivalent", translating different protective layers into an equivalent thickness of 35 MPa concrete. specified by the norm's table. For example, according to Table 1 of STANAG 4623, small, single-story command centers (Category II) should have an equivalent concrete thickness of 2 to 6 meters. For the sake of clarity, one needs to point out that the standard does not specify how this should be achieved - whether by a solid concrete layer, a composite protective system, or deep burial. Ground and Civil (G&C) structures require 0 to 2 meters of normative concrete protection. Based on STANAG 4623, the ceiling thickness of civil defense shelters should be up to 2 meters of concrete equivalent, while lower- tier command posts should range between 2 and 6 meters (of equivalent concrete). In practical terms, this means that a fully reinforced shelter could withstand direct hits from at least 155 mm high-explosive artillery shells, with even greater resistance for command posts. Given the lack of expertise among many designers, resistance levels (such as ceiling and wall thicknesses) should be clearly specified in tables, correlated with shelter capacity and function. This would make it possible for the designers of such facilities to employ simple, yet effective solutions, without a necessity to perform complex calculations. Category I (0-2 meters of concrete) Category II (2-6 meters of concrete) Category III (6-9 meters of concrete) Category IV (9-20 meters of concrete) Category V (>20 meters of concrete) Aircraft shelter Missile silo ICBM command shelter High security, fortified command post Top level command post IADS Shelter Air traffic control center Multi-storey command post Submarines shelter Underground production facility Storage depot Single storey command post - High level, fortified command post - Support shelter Nuclear munitions depot - Underground production facility - Civil defense shelter - - - - Table No. 3 Concrete Equivalent Thicknesses for Different Categories of Structures (STANAG 4623) ANALYSIS