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In the present study, the passive control of closely spaced base isolated buildings is investigated under the effects of earthquakes and blast induced vibrations. The study advocates the installation of fluid viscous dampers to protect the closely spaced buildings against seismic and blast excitations. The performance of base isolated connected buildings is also evaluated under the selected dynamic loadings. The lead rubber isolators are designed and idealized as the Bouc Wen model. The base is dense and the rigidity of the soil, as well as the outflow of energy into the soil, is neglected. A parametric study is also conducted to determine the optimum damper properties for the base isolated connected buildings with viscous dampers. Results exhibit the efficiency of viscous dampers in reducing the structural responses of base isolated buildings. The effectiveness of the passive control technique using fluid viscous dampers in mitigating the bearing displacements of base isolated structures subjected to seismic and blast induced vibrations is also reported. [ABSTRACT FROM AUTHOR]

Material science advancements have resulted in the development of high-strength concrete and steel reinforcement, allowing more efficient and stable buildings against natural and manmade disasters. Increasing security concerns and the potential threat from terrorist activities have led to the safety and resilience of structures against blast loads in modern construction. The present study investigates the performance of reinforced concrete shear walls in mitigating blast-induced vibrations. The study examines four different reinforced concrete buildings based on their shapes, namely square, rectangular, C-shaped, and L-shaped, to understand the blast behaviours with and without shear walls. The study presents a methodology to protect the regular and irregular buildings equipped with shear walls against blast loads at varying standoff distances of 100 m, 200 m, 300 m, and 400 m, respectively. The study also compares the efficiency of passive control dampers and shear walls in enhancing the buildings' performance against blast vibrations. The best placement of the shear walls is also evaluated for all the selected buildings. The study also considers the effect of shear wall thickness in mitigating blast-induced vibrations in multi-storey buildings. The study also discusses the design guidelines and reinforcement detailing of shear walls to protect buildings against detrimental blast effects. [ABSTRACT FROM AUTHOR]

In order to balance the blast protective performance and lightweight property, sandwich panels with various geometries of core are being employed in the military armours and modern-day combat vehicles. Owing to the superior energy absorption capacity of auxetic-reentrant cellular structures, hybridizing auxetic cells with the regular hexagonal cells in the honeycomb core for the purpose of blast protection could be a promising method. Therefore, novel honeycomb cores with combined auxetic and hexagonal cells (AuxHex and Star-Reentrant) are designed for blast protection panel with an aim to enhance the blast performance by improving the energy absorption and minimizing the dynamic deflection of the back plate. Initially, the dynamic response of honeycomb sandwich panels with various regular geometrical cores is analysed and validated with the experimental results from the literature. Further, air blast analysis has been performed on AuxHex and Star-Reentrant honeycomb cored sandwich panel having same relative density as that of hexagonal honeycomb core under exactly same conditions. In addition to that, the study is extended for varying charges of TNT and at different stand-off distances. It has been revealed that the sandwich panel with AuxHex and Star-Reentrant core of same relative density as that of hexagonal honeycomb core absorbs 28% and 19.2% more amount of energy and experiences 17% and 8% less deflection, respectively, than those with regular hexagonal honeycomb core. [ABSTRACT FROM AUTHOR]

Blasting demolition plays an important role in building demolition, and numerical-simulation methods can facilitate the optimization of blasting-demolition schemes. To study the influence of the delay-time differences between columns on the blasting and demolition effect of small-aspect-ratio reinforced concrete structures, a separated common node model of small-aspect-ratio structures was established through the finite element numerical simulation software ANSYS/LS-DYNA. The results showed that the delay-time differences between columns influenced the position of the plastic hinge of the structure, and the plastic hinge was located at the end of the back span beam when the delay-time difference was 0.1~0.3 s. The plastic hinge moves to the top of the back row of the columns of the first floor at 0.4~0.8 s and to the end of each span of the beams at 0.9 s. When the plastic hinge is at the end of the beam, the orientation axis is located at the bottom of the back row of the columns of the first floor. Moreover, when the plastic hinge is at the top of the back row of the columns of the first floor, the orientation axis is at the same position as the plastic hinge. The delay-time difference also affects the recoil distance of the structure as well as the height of the burst pile. To ensure that the structure can be successfully collapsed under the preconditions of disintegration, for a small height-to-width ratio structure, the appropriate intercolumn delay-time difference is 0.4~0.5 s. [ABSTRACT FROM AUTHOR]

It is known that bomb-laden vehicles target many buildings as a result of terrorist activities. The effects of such attacks must be reduced and structures must be protected against blast effects. In high seismic hazard regions, buildings are designed to be earthquake resistant. One of the methods used to dampen earthquake effects on structures is base isolation. Base isolation is effective in distributing blast loads to the structure, similar to seismic loading. In this study, the effects of this distribution on the structure will be evaluated. The scope of the study encompasses the numerical estimation of explosive loads at different distances according to the explosive material carrying capacity of various vehicles and their effects on structures. Linear and nonlinear analysis methods were used to compare the dynamic behaviour of school buildings designed with and without base isolators. The Turkish Building Earthquake Code (2018), which includes the maximum seismic loads, was used in the design of the isolators. Numerical analysis was performed using SAP2000 software based on the finite element method. The blast loads were applied to the floors of the building using the direct integration method in the time domain. FEMA standards were used to determine the blast loads and the performance was evaluated in comparison with the numerical analysis results. As a result of the study, it was concluded that structures with base isolators are efficient in reducing the effects of an explosion at certain distances and these distances will affect the design of the shelter walls. [ABSTRACT FROM AUTHOR]

In the present study, actual three-dimensional structures are converted into a stick model of multi degree of-freedom (MDOF) systems for understanding the macro-behavior of structures. The study investigates the performance of three closely spaced, adjacent G+10, fixed-base MDOF systems with the mass aligned at the same levels and subjected to accidental underground blast loading. The acceleration time history of underground blast loading is generated based on past empirical relationships. The blast charge weight varies from 10 to 75 t while keeping the charge distance constant (R=100 m). The entire formulation is solved with the MATLAB solver, using the state space form solution. Three cases are considered, based on changing the position of the three stick systems. The first case considered left building rigid, middle building moderate rigid, and right building flexible. The second assumed left building flexible, middle building rigid, and right building moderate rigid. The third examined the left building as moderate rigid, the middle building as flexible, and the right building rigid. An analysis of the results shows that the arrangement with low stiffness, high stiffness, and moderately stiff buildings placed to the left, middle, and right side, respectively, yields minimum structural response when compared to the other two combinations. [ABSTRACT FROM AUTHOR]

The response reduction efficiency of passive control viscous dampers installed between adjacent structures subjected to blast-induced vibrations was investigated. The blast-induced vibrations studied were mainly due to mining activities along with the accidental explosions in underground storage chambers. Equations of motion formulated by different researchers in examining the performance of damper-connected structures were reviewed. Two different types of structures (similar and dissimilar buildings) were selected to analyse the effectiveness of damper-connected buildings. A parametric study was also conducted to determine the optimum damper placement locations along with optimum damper properties for the similar buildings connected with viscous dampers. The results showed the efficiency of viscous dampers for the case of similar buildings. For dissimilar buildings, the peak responses were found to be almost equivalent for both connected and unconnected structures. Therefore, the root mean square responses were evaluated to compare the effect of blast vibrations beyond the initial impulse for the case of connected dissimilar buildings. In addition, the performance of similar structures connected with the same damping was compared with the responses obtained from different damping conditions to minimise the damping coefficient of dampers. [ABSTRACT FROM AUTHOR]

The last few decades have shown a dramatic increase in the number of man-made disaster activities resulting in extensive life loss and structural failures. The explosive devices used in these heinous acts result in blast wave loading. Therefore, the present structural engineers require comprehensive expertise to analyze and design blast-resistant structures. The present study aims to develop blast load time history based on the previous research works and demonstrates the effectiveness of base isolation technique such as lead rubber bearings in mitigating the structural responses under the effect of blast loading. Two base-isolated building models systems are analyzed to examine the role of structural control strategies subjected to blast loading. Various isolation parameters are also incorporated in the present investigation in improving the structural performance subjected to this extreme dynamic loading. The study concludes that base isolation is an efficient technique in reducing structural output parameters such as peak storey displacement, storey drift and root mean square absolute acceleration values due to post-blast effects. Energy-based equations are also examined in the study to evaluate the hysteretic energy dissipated by the system subjected to blast loading. [ABSTRACT FROM AUTHOR]