Journal of Structural Engineering & Applied Mechanics

Senthil Kasilingam Muskaan Sethi Loizos Pelecanos

The tunneling system has become an important part of the present infrastructure system in all over the world. Therefore, it has become important to ensure the safety of the tunnels against any type of man-made blasting activities or other accidental blasting occurrence. In order to evaluate the performance of the tunnels against blast loading, a detailed review is carried out. Based on the review in the last couple of decades, the various parameters such as tunnel lining materials, tunnel shapes, tunnel lining thickness, tunnel burial depth, charge weight and standoff distance are high influences on the performance of underground tunnels against blast loading. It was observed that the tunnel roof and the tunnel wall center are most vulnerable to the blast loads. Also, it was found that more of the tunnel lining thickness results in lesser deformation at the tunnel roof and the tunnel wall center. The increase in the burial depth of the tunnel would reduce the extent of damage to the tunnel caused by effects of surface blast loading. The stiffness and strength of the ground media may be enhanced against the effects of blast loading by grouting measures. The studies revealed that the lining materials possessing blast waves absorbing properties can be best suited to be used in tunnel linings. Further, it was observed that more damage was caused to the tunnels due to the magnitude of the charge weight. An increase in the blast load causes a significant increase in the fracture area, residual stress and lateral displacement caused to the tunnel by the action of blast load. The standoff distance of the blast load from the tunnel also plays a significant role in the damage of the tunnel. More is the distance between the charge and the tunnel, lesser damage caused to the tunnels. In addition to that, the lining thickness was predicted and the trend was calibrated and fitted logarithmically with the available results. Based on the observation from the literature, it is concluded that the use of a single lining material in the tunnel against blast loading was studied predominantly in the couple of decades. Further, the performance of the tunnels in combination of different tunnel lining materials against blast loading was found limited. The influence of barriers to save the underground tunnels against blast loading was found limited.

https://doi.org/10.31462/jseam.2021.01001017

Mustafa Ergün Şevket Ateş

The aim in this study is to numerically present some characteristic features of the rectangular finite element using the matrix displacement method and to show the utility of this element in plane stress problems compared to the finite element method. The paper consisted of three parts. In the first part, all of the finite element formulation steps from choosing the convenient coordinate system to creating element stiffness matrix are presented respectively. In the second part of the study, a static finite element analysis of the shear wall is also made by ANSYS Mechanical APDL. In the final part, the results (displacements, strains and stresses) obtained from the previous parts are compared with each other by the help of tables and graphics. The results show that this method is effective and preferable for the stress analysis of shell structures. Further studies should be conducted in order to indicate the efficiency of the matrix displacement method for the solution of different types of plane stress problems using different finite elements.

https://doi.org/10.31462/jseam.2021.01018027

Ahmet Can Altunışık Fatma Önalan Fezayil Sunca

Structural damage caused by terrorist attacks or explosions resulting from accidents is an essential crucial issue for civil engineering structures. After the explosion, heavy damage and total collapse occur in the structural carrier system, and these destructions can cause significant loss of life and property. This study aimed to determine the structural behavior of brick walls exposed to blast loading with different explosive weights using analytical, numerical, and experimental methods. The masonry brick walls were selected for the application and constructed in the allowed quarry area for experimental studies. 40g, 150g, and 290g of TNT, which are placed inner base center of brick walls, were used respectively to observe the progressive damage. The analytical blast responses, such as maximum pressure values etc., were calculated and predicted empirical formulas. The numerical blast responses were determined with Ansys Workbench and Autodyn software. At the end of the study, damage situations, pressures, displacement values, and energies are presented comparatively. It is observed from both experimental and numerical methods that 40g and 150g TNT explosives caused several damages on the wall. The wall collapsed on supporting points in 290g TNT explosives. It can be seen that the mean values of pressures and displacements increase respectively by three and six times, with the TNT explosive weight increasing from 40g to 290g. A good agreement is also found between the finite element results and empirical formulas proposed by Henrych and Sadovsky. However, inconsistent blasting responses are obtained with empirical formulas depending on the scaled distance.

https://doi.org/10.31462/jseam.2021.01028045

Çağlar Yalçınkaya

Ultra-high-performance concrete (UHPC) is an innovative cementitious composite containing steel fiber reinforcement that can improve the behavior of structural elements thanks to its high strength and improved ductility properties. The mix design that provides these superior properties of UHPC also makes it a high-cost material. For this reason, the use of UHPC in parts where it contributes more significantly to the performance of the structural elements will lower down the costs and reduce the negative environmental effects caused by high cement content. In this preliminary study, the production of normal concrete (NC)-UHPC reinforced concrete (RC) composite beams by wet-on-wet casting was investigated by producing mini-RC beams. In the production of mini-RC beams, normal mortar (NM) and self-compacting mortar (SCM) mixtures were used to represent an NC. The results showed that in the production of NC-UHPC composite beams, the mixtures should have different rheological properties depending on the order of the layers. Increasing the total thickness of the UHPC layer enhanced the initial and yield stiffnesses as well as the peak loads. UHPC layer with thicknesses of 15 mm in tension zone, 30 mm in tension zone, and 15+15 mm in tension+compression zone led to the load-carrying capacity increment ratios of 20%, 34.6%, and 24.3%, respectively. However, increasing the thickness of the UHPC layer in the composite beams, especially more than 15 mm, reduced the ductility ratio and energy absorption capacity. Optimizing the tensile reinforcement ratio in UHPC layers can overcome the drawbacks in the ductility.

https://doi.org/10.31462/jseam.2021.01046056