MS7.10 - Dynamic Soil-Structure Interaction and Wave Propagation

Title: Identification of a Coupled Ground-Building Seismic Response Analysis Model Based on Measured Data In recent years, unexpected large earthquakes have caused much damage, and it has become very important to know the vibration characteristics of buildings. In particular, medium- and low-rise buildings are often seen throughout the world. It is especially necessary to properly evaluate this effect for structural design, because these buildings in general are strongly affected by the dynamic interaction effect between the ground and the building. On the other hand, it is not always the case that the building after completion of construction or the ground at the point of construction will have the dynamic characteristics assumed in the design. In order to verify their consistency and provide basic information during design, inverse analysis based on observation records is helpful. For this purpose, it is desirable to identify not only the natural period and damping constants, but also the components of the dynamic analysis model, such as the stiffness of each floor for the lumped mass analysis model. However, most of the previous studies have focused on building models with fixed foundations, and there have been few cases of identification for coupled ground-building systems. In addition, most of these studies have been conducted on shaking table experiments, but there are also few studies on actual buildings, where observation points are limited. In this paper, we apply the Modal Iterative Error Correction method (MIEC method) to the earthquake records of the foreshocks of the 2011 off the Pacific coast of Tohoku earthquake to identify the coupled superstructure-foundation-soil system in a real building with a small number of observation points. The analysis was performed on an eight-story SRC building. Observations were made on the first, second, fifth, and eighth floors, and this data was used for the identification. In this earthquake, the response of each part of the building is within a linear range. The advantages of using the MIEC method include the following; 1) A large number of parameters can be identified at the same time. 2) It is not prone to locally stable solutions. As an identification method, multiple parameters are identified in two steps by dividing them into each building model. First, the stiffness of the superstructure is identified as a parameter in the fixed-foundation model. Next, an SR model was created using the stiffness of the superstructure as the initial value, and the identification was performed with the ground spring as a parameter. The identification results for a real building with a limited number of observation points including soil springs in a linear range showed good correspondence with the observed values, and the identification was performed appropriately.

Trains will generate vibrations in the ground that will propagate to the buildings and radiated noise inside lodgings. Less known is the fact that the free surface will act as an infinite baffle radiating noise. This contribution is here studied. In order to quantify this effect, an existing 2.5D FEM/BEM model is completed. The free surface velocity field is used by means of a Rayleigh integration to compute the sound pressure levels radiated above ground. It uses the Green function above an infinite horizontal plane. The presence of buildings can be introduced by deriving an appropriate Green function based on a geometrical approach. A practical case has been used to compare predicted noise levels near an existing railway track and shows that the model recovers the low frequency emergence measured below 125 Hz. According to the calculations, the estimated ground-borne sound radiated is dominant at low frequencies and otherwise rather negligible compared to the sound directly emitted by the train/track system. Moreover, a small parametric study performed using a 2D source (vehicle and tracks) model coupled to the same ground model shows that the ground-borne sound radiated is ground dependent. The transmission of the noise component through windows has been compared to ground borne noise and found to be dominant, again, at low frequencies. Therefore, the ground should be considered as a separate sound source when dealing with railway sound and should be added to the other known sources (track and vehicle components).

The shock wave resulting from the explosion process is the main burden on the technical infrastructure facilities or people in contact with the epicenter of the explosive explosion (MW). The article presents the tests of EN C45 steel pipe of 10 mm thickness buried beneath the earth as a result of the impulse load of the detonation wave of the explosive charge. This process was modelled in two ways using Abaqus Explicit code software using a 75 g Tri-Nitro-Toluene (TNT) position 30 mm above the steel pipe and exactly within the pipe. As a result of detonation, the samples were not fragmented, but visibly deformed displaying faster travelling of the explosion wave in air than in the soil. The main purpose of the work was to verify the impact resistance of EN C45 steel, which is commonly used in technical facilities. The numerical model results on the impact of the shock wave on the steel tested material in the areas subjected to dynamic deformation are presented. The method used in this work is Coupled Eulerian-Lagrangian Method (CEL). Keywords: shock load, shock wave, microscopic analysis, explosion modeling, steel C45