# Numerical Identification of Material Model Parameters of UHPFRC Slab under Blast Loading
## 4 Material Model of Simulation  
With the development of concrete and concrete composites, there was an effort to capture their response to loading through numerical simulations. An overview of material models of concrete implemented in the software environment of solvers based on the finite \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Test Number** & **1** & **2** & **3** & **4** & **5** & **6** \\ \hline TNT mass (g) & 75 & 75 & 200 & 200 & 225 & 225 \\ Distance (mm) & 50 & 50 & 300 & 200 & 250 & 200 \\ Displacement (mm) & 2.25 & 2.20 & 3.20 & 4.66 & 4.50 & 5.10 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Experimental parametric setup with concrete specimen deflection. Figure 4: Time-displacement curve of the concrete specimen obtained during the experiment using an optoNCDT 2300 laser sensor. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Source** & **This Paper** & **[10]** & **[23]** & **[24]** & **[24]** & **[20]** & **[20]** & **[20]** & **[23]** \\ \hline Chapter, figure, table & Table 4 & Chapter 2.2 & Chapter 5, Figure 6 & Chapter 2, Table 2 & Chapter 2.1, Table 1 and 7 & Table 1,2 and 7 & Table 3 and 5 & Tables 1 and 2 \\ Specimen/ test & 6 & & & -21 & 6-1 & 2 & 2 & 1 & B \\  & 500 \(\times\) 500 & 1250 \(\times\) 1250 & 1300 \(\times\) 1000 & 660 \(\times\) 660 & 660 \(\times\) 660 & 550 \(\times\) 550 & 1000 \(\times\) 1000 & 750 \(\times\) 750 \\ Dimensions (mm) & \(\times\) 60 & \(\times\) 50 & \(\times\) 100 & \(\times\) 25 & \(\times\) 25 & \(\times\) 50 & \(\times\) 50 & \(\times\) 40 & \(\times\) 30 \\ Material & UUHPLC & RC (bars) & SPIRC & UUHFRC & UHFRC & UHFRC & HSRC & RC (bars) & RC (bars) \\ Fibre-doxoge [\%] & 2.0 & & 2.0 & (hybrid) & 1.0 & 0.5 & & \\ Standoff distance & 200.0 & 500.0 & 100.0 & 500.0 & 500.0 & 242.5 & 242.5 & 400.0 & 300.0 \\  & 1 mm) & & & & & & & & \\ Explosive & TNT & TNT & CompB & PF4 & PF4 & TNT & TNT & TNT & TNT \\ Explosive mass [g] & 225 & 640 & 500 & 200 & 200 & 244 & 244 & 200 & 190 \\ Displac, or & 5.1 & 19.0 & 9.0 & 2.2 & 1.6 & 2.0 & 5.0 & 10.0 & 26.0 \\ deflection [mm] & & & & & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Comparison of experimental measured deflection of concrete slabs under explosive load. element method provides a broad basis for solving problems of fast dynamics. With the development of software, more complex models were gradually added to the material model libraries due to the inadequacy of the existing models, which were created as an initiative of academic circles or private companies solving very specific problems. In terms of the number of implemented models suitable for concrete modelling, the LS-Dyna program environment stands out [54]. Due to the explicit integration scheme of the equation of motion used by the solver, LS-Dyna is a suitable software for simulating fast events, such as explosions, impacts or penetrations [55]. By extending it with an implicit solver, the software can also be used in combined tasks, where both static and dynamic loads occur [56]. The following pages provide an overview of the Winfrith material model used in the simulation and inverse identification in this paper. This model is suitable for solving tasks with a significant share of dynamic events, both for reasons of its complexity and range of parameters, as well as the ability to capture the loading method together with its low computational time demands due to its ability of smeared reinforced definition [57]. The Winfrith material model is a non-linear material model intended for modelling plain and reinforced concrete. The Winfrith concrete model is defined as a model of split cracks (pseudo cracks) and split reinforcement.