# Experimental and Empirical Study for Prediction of Blast Loads
## 1 Introduction  
The effects of explosions were studied more extensively after World War II, mainly because many explosives were developed during this period and are still in use today. For many explosives, demands are made for high stability, safety and effectiveness. Most aromatic nitrolates and a much smaller number of nitric acid esters and nitroamines meet these criteria. The most commonly used explosive is the well-known Trinitrotoluene (tritol or TNT). To estimate or calculate the response of an object or structure to the effects of an explosion, it is necessary to know the explosion parameters. Of these parameters needed to determine the response, the most important are usually the peak overpressure, the positive phase duration and the positive phase impulse. The positive phase impulse can usually be calculated from the blast curve and is dependent on the overpressure and positive duration. Knowledge of the blast parameters then defines the basic load of buildings or structures. A variety of methods can be used to determine explosion parameters. These can be based on empirical (or analytical), semi-empirical or numerical methods. Empirical methods are essentially correlations with experimental data. Most of these approaches are limited by the range of experiments carried out. The accuracy of all empirical correlations decreases with distance to the source of the explosion. Semi-empirical methods are based on simplified models of physical phenomena. They try to use the essential physical processes in a simplified way. These methods rely on extensive experimental data. Their predictive accuracy is generally better than that of empirical methods. Numerical methods are based on mathematical equations that describe the basic laws of the phenomena being solved. These methods consider the conservation of mass, momentum and energy, or the physical behaviour of materials by means of constitutive relations. It is the empirical methods in the initial assessment of objects in the context of prevention or severe consequence assessment that can be a very useful tool. When rapid estimates of explosion parameters are needed, often for a large number of objects, these methods are essential. For a more in-depth analysis of the load of a building or to refine the initial load values of a structure, numerical methods are much more suitable. During the second half of the 20 th century, a considerable number of experimental and theoretical studies were conducted to understand the effects of blast on buildings and structures [1; 2; 3; 4; 5]. The aim was first to study the behaviour of air blast waves including the determination of their characteristics and then to investigate the dominant factors influencing the incident waves. Another objective was to investigate the response of the building structure to blast load [6; 7], based on the analysis of several experimental data, which presented the formulae to compute peak positive overpressure, positive phase duration and positive phase impulse [2; 4], and utilised both experimental and theoretical means to obtain the parameters of the blast wave such as overpressure, positive phase duration, blast wave arrival time and positive phase impulse [1]. In 1984, [PERSON] and [PERSON] presented the parameters for air burst in terms of high order polynomials [4; 8] and presented the same results as were produced by [PERSON], in terms of simplified polynomials functions. The use of empirical laws has been extensively studied and has been applied in various recommendations, mostly proposed by military authorities. In particular, the two most commonly used empirical models are based upon different but related studies of the U.S. Army Corps of Engineers (USACE): the document [9], containing the model CONWEP, and the Technical Manual TM5-1300 [10], completed by successive documents [11]. In 2013, the Joint Research Centre of the European Union produced a Technical Report [12], substantially referring to these two last documents and to another Technical Report of the U.S. Army [4].