This paper is focused on sensitivity analysis of the behavior of subsoil foundation systems by considering the variant properties of a fiber concrete slab that result in different relative stiffness of the whole cooperating system. The character of the slab and its properties are very important for the character of external load transfer. However, the character of the subsoil also cannot be neglected because it determines the stress-strain behavior of the entire system and, consequently, the bearing capacity of the structure. The sensitivity analysis was carried out based on experimental results, which included both the stress values in the soil below the foundation structure and settlements of the structure that are characterized by different quantities of fibers in it. Flat GEOKON dynamometers were used for the stress measurements below the observed slab, the strains inside the slab were registered by tensometers, and the settlements were monitored geodetically. This paper is focused on the comparison of soil stresses below the slab for different quantities of fibers in the structure. Results obtained from the experimental stand can contribute to more objective knowledge of the soil-slab interaction, the evaluation of real carrying capacity of the slab, the calibration of corresponding numerical models, the optimization of quantity of fibers in the slab and finally, contribute to higher safety and more economical designs of slabs.
This article is focused on the analysis of the use of distributed fibre-optic technology for security monitoring of road tunnel and motorway tunnel structural load. The authors focused on the measurements of deformation utilizing Brillouin Time Domain Reflectometry (BOTDR). The principle is based on the measurement of stimulated Brillouin scattering. The article describes and analyses real measurements within a period of 5 months, which were carried out during the tunnelling and the whole process of building a new tunnel inŽilina, Slovakia. The performed experimental measurements were carried out using a standard optic telecommunication cable with water-absorbing aramid yarns and a jacket with a diameter of 4.2 mm. The contribution of this article lies in the introductory analysis of the implementation and use of the fibre-optic technology for security monitoring of road tunnel and motorway tunnel structural load.K e y w o r d s: Brillouin time domain reflectometry (BOTDR), fibre-optic sensor
New possibilities of vibration monitoring can be found in completely different physical approaches, where all measuring technology is currently based on sensors in the electrical domain. This paper presents two different promising alternative approaches to vibration measurement, specifically in the field of fiber-optics and pneumatic sensors. The proposed solution uses a Michelson fiber-optic interferometer designed without polarization fading and with operationally passive demodulation technique using three mutually phase-shifted optical outputs. Experimentally developed sensor systems for the registration of anthropogenic seismic phenomena were complemented by standard instrumentation for measuring seismicity used as a standard. The measurement was performed under simplified conditions using a calibrated stroke as a source of dynamic loading. In addition to alternative systems, the paper also presents the results of recalculation of the measured values in a time domain and basic relationships for the conversion to basic units derived from the SI (International System of Units) system and used internationally in the field of seismic engineering. The results presented demonstrate that even systems operating on a different physical principle have great potential to replace the existing seismic devices. The correlation coefficients for both sensory devices were high (above 0.9) and the average deviations from the measured values of the amplitude of the oscillation velocity did not exceed the value of 0.02, neither with the fiber-optic or pneumatic sensor.
Shape and material optimization of building structures, including reducing the amount of concrete used, are very important aspects in sustainable construction. Numerical modelling is currently used very effectively to design optimized and sustainable structures, including their interaction with the surrounding rock environment. This paper is focused on the three selected factors of numerical modelling of fibre concrete slab and subsoil interaction: (1) the constitutive model of fibre concrete slab, (2) deformational and strength characteristics of subsoil, (3) effect of interface elements. The specialized geotechnical software Midas GTS NX, based on the finite element method, was used for the modelling of this task. Numerical results were compared with the experimental measurement of vertical displacements on the upper surface of slab. In the presented study, three constitutive models of slab recommended in MIDAS GTS NX code for modelling concrete behaviour (elastic, Mohr-Coulomb and Drucker-Prager) were applied. In addition, the sensitivity analysis with respect to the deformational and strength characteristics of subsoil was performed. The numerical study also presents the effect of the interface elements application on the slab behaviour. The numerical results of maximum vertical displacements based on the Drucker-Prager and elastic model underestimated both the experimental results and numerical results based on the Mohr-Coulomb model. From the qualitative point of view (shape of deflection curve), the numerical simulation showed the better agreement of the Mohr-Coulomb constitutive model with the experimental measurements in comparison with the other two investigated constitutive models. The performed parametric study documented that reduction of the strength and deformational characteristics of subsoil leads to the increase of maximum vertical displacements in the centre of slab, but the experimentally measured deflection curve, including uplift of slab and gapping occurrence between the slab and subsoil, was not achieved without the interface application.
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