In order to reduce the vulnerability of especial buildings to military threats, a series of measures called Passive Defense should be executed. Maintaining the stability and minimizing the damage and casualties in especial and highly-important buildings in military, industrial, crisis management, etc. units are considered to be one of the goals of Passive Defense. For example, the control and switchgear rooms in industrial plants, to which any damage leads to a long-term hiatus and major life and financial losses, are of especial buildings that should be blast-resistant. Raising the possibility of maintaining the life safety and survival of specific structures and facilities that may come under arms and military attack are accomplished in two ways: 1) Residing in locations away from possible targets of attacks, and 2) Considering engineering preparations and strengthening of structures and facilities. The latter way, i.e. design and construction of structures resistant to direct hit or close blasts is the topic that will be dealt with in this section.
Any blast, depending on the characteristics of the bomb or the explosive materials, entails some consequences. For instance, the explosion of a nuclear bomb will entail the complications such as nuclear and thermal radiation, electromagnetic pulse, air blast, ground shock, debris and dust. Air blast and the complications related to wave blast in space are the main parameters in the calculations of designing blast-resistant structures. It is necessary to note that usually the industrial or accidental and civil blasts are basically different from military explosions, hence the details of designing for these two conditions are different.
The consequences of a blast is dependent on parameters such as range, weapon yield (which is itself dependent on the amount of explosive materials based on the pound unit of TNT), and height of burst. One crucial difference in the design of blast-resistant structures is the impact loads on the structures. In fact, in this case the structure should carry huge forces in a very short time. This fact will have a drastic effect on changing the elastic and plastic behavior of the materials and elements.
In sum, the process of designing blast-resistant structures consists of the following steps:
1- Determining the basic effects of the blast such as the pressure-time history Diagram and dynamic pressure, ground shock, etc.;
2- Loading the structure including direct loads of air blast on the structures on the ground and the indirect loads resulting from the air blast on the buried structures;
3- Determining the characteristics of structural materials and the behavior of structural elements under the blast load;
4- Choosing the structural load resisting system and performing the design calculations;
5- Dynamic analysis of the structure under the blast load (nonlinear time-history analysis).
With abundant scientific and practical experiences in design of especial structures, this company has significant technical ability in expert human resources as well as informatics tools and application software and is ready to present satisfactory and high-quality services in designing especial blast-resistant structures according to regulations of valid technical references such as ASCE Manual NO. 42, UFC 3-340-02, ASEC/SEI 59-11, etc.