explosion is presented in this paper. The structural response of the silos due to the blast loading imposed by the explosion was assessed using 3D laser scan. Then, the silos were modeled using three-dimensional finite element models using Abaqus explicit. The silos' damage and failure were investigated to estimate the blast magnitude and to check the silos structural response against the silos' concrete strength and additional reinforcement and concrete coating added to the silos in 2000. In addition to the effects of reinforcing the ribs between the silos as well as the soil and foundation. Therefore, these parameters were tested after estimating the blast magnitude to check the structural status of the remaining part of the Beirut port silos (if they can be reusable), the role played by the foundation and soil and if the silos' response would have changed if certain parameters were taken differently in the design. In this article, the damage and silos' displacement obtained from the numerical models were compared to the results obtained by the 3D laser scan. The results of this investigated article show that a blast magnitude of 337.5 tons TNT (938 tons of Ammonium Nitrate) best captures the silos' displacement and damage amount. The silos exhibit a tilt between 20 and 30 cm in the direction of the blast. The numerical results indicate that constructing the silos with higher compressive strength would not have affected the silos' damage. Nevertheless, adding the extra concrete coating and reinforcement layer in 2000 to the outer silos decreased the amount of damage in the silos. Moreover, reinforcing the ribs between the silos would have decreased the silos displacement and damage amount. Finally, the soil and the foundation played a positive role in the explosion by absorbing part of the released energy while the silos, in the current state, cannot be reused.

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Background: Midrise 5 to 15 storeys frame structures sitting on soft soils are susceptible to damage induced by seismic events. The level of damage is related to the interaction between the structure, foundation and soil called Soil Structure Interaction (SSI). If the level of ground acceleration is low, the wave gets amplified putting the structure at risk of collapse. Objective and Methods: Concerns about SSI have motivated several researchers to investigate the seismic behaviour of structures rested on cohesive and cohesionless soils. The objective of the work presented in this paper is to evaluate the effects of several parameters on the seismic soil structure interaction behaviour of midrise structures sitting on silty sandy soil. Using ABAQUS, reliable 3D models of 5 to 15 storeys midrise concrete frame structures rested on raft foundation were built. The effects of the structure’s number of storeys, raft size and thickness were explored for different column sizes. Fixed-based structures which capture the model adopted in seismic codes and flexible-based structures were hit at the bottom by El-Centro (1940) and Northridge (1994) earthquakes. Results and Conclusion: The results, presented in terms of storey lateral deflection, inter-storey drift, shear force, foundation rocking and response spectrum showed the important contribution of SSI effects on the behaviour of the midrise structures. The model analyses indicated that column size strongly affects the behaviour of flexible structures. Let N be the structure number of storeys and C the column size. The results showed that in terms of storey lateral deflection and levelling shear force, for column sizes C 0.5 X 0.5 m, SSI was detrimental to structures with 10 ≤ N ≤ 15 and beneficial to structures with 5 ≤ N <10. Increasing the column size to C 0.5 X 1 m showed that SSI became detrimental for structures with 10 < N ≤ 15 under El-Centro (1940) and for structures with 7≤ N ≤ 15 under Northridge (1994), and beneficial for structures with 5 ≤ N ≤ 10 under El-Centro (1940) and for structures with 5 ≤ N < 7 under Northridge (1994). The FE results showed that even though base shear increased with raft size, lateral deflections were amplified for C 0.5 X 0.5 m S15 structures and attenuated for C 0.5 X 1 m S15 structures. However, the seismic response of S15 structures was slightly affected by the variation in raft thickness under both column sizes. Finally, the paper includes a discussion and evaluation of the contribution of inertial and kinematic effects, including soil types used on the simulated numerical models’ seismic responses.

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