This paper investigates the influence of the cylindrical charge characteristics, i.e., the length-to-diameter ratio, orientation, and initiation configuration, on the blast loads (peak overpressure and maximum impulse). Three different initiation configurations were considered, i.e., at the center, at one end, and at both ends. Numerical models were developed for the spherical and cylindrical charges. The numerical results were analyzed along the gauge lines at different azimuth angles around the cylindrical charges. Some important observations were made. Neglecting the charge shape effect, the peak overpressure (maximum impulse) in the near field generated from centrally initiated cylindrical charges can be underestimated by a factor as high as 3.0 (1.9). Therefore, the cylindrical charge shape should be explicitly modeled in the numerical simulations for the blast-resistant design of protective structures subjected to near-field detonations. It is confirmed that the shock front heals into a spherical one in the far field. Hence, the blast loads generated from the spherical charge of the same mass can be used. In addition, the influence range, beyond which the charge shape effect can be neglected, is $5.7\mathrm{m}/{\mathrm{kg}}^{1/3}$ for the impulse, which is about twice that for the overpressure ($3.2\mathrm{m}/{\mathrm{kg}}^{1/3}$ ). In general, the maximum values of blast loads resulted by the three considered initiation configurations can be sorted in descending order, i.e., $\text{at}\text{one}\text{end}>\text{at}\text{the}\text{center}>\text{at}\text{both}\text{ends}$ . The initiation configuration at one end (at the center) has the largest influence range of $3.9\mathrm{m}/{\mathrm{kg}}^{1/3}$ ($5.7\mathrm{m}/{\mathrm{kg}}^{1/3}$ ) for the overpressure (impulse) among the three considered initiation configurations.

Truss layout optimization under complex constraints has been a hot and challenging problem for decades that aims to find the optimal node locations, connection topology between nodes, and cross-sectional areas of connecting bars. Monte Carlo Tree Search (MCTS) is a reinforcement learning search technique that is competent to solve decision-making problems. Inspired by the success of AlphaGo using MCTS, the truss layout problem is formulated as a Markov Decision Process (MDP) model, and a 2-stage MCTS-based algorithm, AlphaTruss, is proposed for generating optimal truss layout considering topology, geometry, and bar size. In this MDP model, three sequential action sets of adding nodes, adding bars, and selecting sectional areas greatly expand the solution space and the reward function gives feedback to actions according to both geometric stability and structural simulation. To find the optimal sequential actions, AlphaTruss solves the MDP model and gives the best decision in each design step by searching and learning through MCTS. Compared with existing results from the literature, AlphaTruss exhibits better performance in finding the truss layout with the minimum weight under stress, displacement, and buckling constraints, which verifies the validity and efficiency of the established algorithm.

The use of protective barriers is one of the most common approaches to protect buildings and their occupants against blast and vehicle impacts. They increase the stand-off distance between the explosive source and the building. However, the protection capabilities of barriers with openings have not yet been thoroughly studied. The present paper discusses the shock wave attenuation effect of protective barriers made of steel posts with a hollow cross section. In the experiments, the steel posts are located at a distance of 5 m to the building to be protected. Prior to the experiments, numerical models were developed to predict the blast loads numerically. Overpressure-time history measurements (side-on and reflected) were made at various distances in front of and behind the barrier. The experimental data were used to, for example, validate the numerical models. The experimental and numerical results showed that barriers can reduce the blast loads relative to the scenario in which no barriers were present. Considerable reductions in peak side-on and reflected overpressure and impulse were observed behind the barriers. Furthermore, after validation, parametric studies are carried out to investigate the influence of further parameters on the overpressure reduction behind the barriers, that is, the number of posts or the spacing between posts, the cross-sectional shapes of posts, and the arrangement of posts (single-layer or multilayer, aligned or staggered). These studies showed that a barrier without openings is not always necessary to offer the desired protection because barriers with openings can also show satisfactory results. Hence, the necessary amount of material (steel in this case) and, thus, the construction cost can be considerably reduced.