This article deals with the dynamic analysis in pad concrete foundation containing Silica nanoparticles (SiO2) subject to seismic load. The foundation is covered by a piezoelectric layer for smart ...control of the structure. The weight of the building by a column on the foundation is assumed with an external force at the middle of the structure. The foundation is located in soil medium which is modeled by spring elements. The Mori–Tanaka low is utilized for calculating the equivalent material characteristics of the concrete foundation. The structural damping of the structure is considered based on Kelvin–Voigt model. The concrete structure is modeled by thick plate and the governing equations are derived based on first order shear deformation theory (FSDT) utilizing Hamilton’s principle. Applying differential quadrature method (DQM) and Newmark method, the dynamic deflection is obtained. The effects of applied voltage to smart layer, volume percent and agglomeration of SiO2 nanoparticles, structural damping, soil medium and geometrical parameters of structure are shown on the dynamic deflection. Results indicate that with applying negative voltage, the dynamic deflection is reduced significantly. In addition, the SiO2 nanoparticles decreases the dynamic deflection of the concrete foundation.
•Mathematical modeling of pad concrete foundation.•The pad concrete foundation is covered with a smart layer.•The pad concrete foundation is reinforced by SiO2 nanoparticles.•The structural damping of the structure is considered based on Kevin-Voigt model.•Applying DQM and Newmark method, the dynamic deflection is obtained.
The paper presents the exothermic reaction monitoring method used in solving the thermal conductivity problems as well as in the process of solidifying the concrete foundation. The finite element ...method was applied. The problem was solved in a three-dimensional model taking into consideration the thermal characteristics dependence during the process of concrete hardening. The unsteady temperature field of the foundation block was calculated taking into account the forced pipe cooling. The given methodology is implemented in software and used for performing the three-dimensional unsteady temperature calculations. The software "Temper-3D" having a compliance certificate was developed according to the mentioned methodology. The program was registered in the Computer Software Register.
Abstract
In this paper, the hydrodynamic characteristics of a large concrete foundation oil storage platform under wave action are simulated by using the three dimensional wave sink IHFOAM developed ...by OpenFOAM. It mainly simulates the wave high,the envelope diagram of the maximum pressure value, and the force characteristics of the platform such as the combined force and bending moment under two working conditions. And draw relevant conclusions, provide optimization suggestions for the design layout scheme, and provide reference for other similar structure calculations.
Tower foundations have been used as grounding electrodes to reduce the area of the grounding devices. However, it is difficult to calculate the grounding resistance due to the complex structure of ...the reinforced concrete foundation. A method for calculating grounding resistance of reinforced concrete foundations is proposed in this paper. The method equates the complex foundation structure into a cylindrical conductor and then calculates the grounding resistance with the help of the method of moments, which simplifies establishment of the simulation model and reduces the extensive computation. In addition, the applicability of the equal cross-sectional area method and the equal cross-sectional perimeter method is analyzed. It shows that both methods are applicable only when the concrete resistivity is close to the soil resistivity. The equal cross-sectional area method is applicable when the concrete resistivity is within twice the soil resistivity, while the equal cross-sectional perimeter method is applicable when the concrete resistivity is approximately same or less than the resistivity of the soil.
This study shows that there is a need to improving ac power supply grounding systems with the help of reinforced-concrete supports and foundations as natural ground sources. An equivalent circuit for ...wet concrete is presented that takes into account the transverse filling of air pores. The dependence of the specific resistivity of the catenary system’s reinforced concrete pores and foundations on the structural moisture and temperature is shown. The moisture relation of electrical breakdown voltage is calculated for the catenary system’s reinforced-concrete supports and foundations.
This paper presents an innovative type of mountain wind turbine foundation, namely, the cone-shaped hollow flexible reinforced concrete foundation (CHFRF). It consists of a top plate, a base plate ...and a side wall that are made of reinforced concrete. The cavity of the CHFRF is filled with rubble and soil directly from the excavation for the CHFRF, which means that it can absorb the spoil. A rubber layer is placed beneath the CHFRF to increase the foundation flexibility to resist cyclic and dynamic loadings and to increase the bearing capacity. The great advantages of the CHFRF are the reduction in the usage of concrete and steel and the protection of the vegetation around the wind turbine, compared with conventional mountain wind turbine foundations that are solid structures. It is verified through model tests and a numerical simulation that the CHFRF can provide higher lateral bearing capacity in comparison to the regular circular gravity-based foundation under the same foundation diameter and height, and that the bearing capacity is increased by approximately 33.5% accordingly. It is also found that the rubber layer can effectively reduce the accumulated rotation of the CHFRF under cyclic loading. The accumulated rotation of the CHFRF with a rubber layer having a thickness of 4 mm is decreased by about 50% compared to that of the CHFRF with a rubber layer having a thickness of 2 mm. In addition, the volume of concrete used for the CHFRF is only one-fifth of that used for the circular gravity-based foundation. Therefore, the CHFRF outperforms regular mountain wind turbine foundations.
To reduce the thickness of reinforced concrete foundation members used in construction and structural applications, a previous study developed and tested a strut–tie retrofit system installed in the ...foundations. This study proposes the optimum retrofit details of a steel-tie retrofit system for foundation members with reduced thickness via a finite element simulation-based load-bearing capacity assessment. The retrofit parameters (structural steel type, plate thickness, and number of strut frames) that significantly affected the load-bearing capacities were optimized by comparing the maximum effective stress and code-defined allowable stress limits. The optimum retrofit details were compared with those computed using a code-defined strut–tie model. Based on the load-bearing capacity assessment for the design of loading combinations, the optimum retrofit details can be reduced in transverse (by 55%) and longitudinal (by 87%) directions compared with those designed using the strut–tie model approach.
Summary
Damage in the precast concrete piles occurs mostly during installation. The wave propagation‐based nondestructive testing (NDT) is commonly used to estimate the effective length of the pile ...after installation and to detect pile damage. However, information extracted from this type of diagnosis is limited and subjective. Whereas, the vibration‐based NDT could provide a comprehensive automatic pile health diagnosis tool. In this paper, a new higher order vibration‐based health diagnosis technology, which utilizes a shaker to generate sweep‐sine excitation and an adaptive nonlinear non‐stationary higher order spectral analysis, is introduced for foundation piles. This research describes two different diagnostic technologies, namely, the advanced nonlinear non‐stationary chirp Fourier bicoherence (CFB) technology and the novel nonlinear non‐stationary frequency response function of the CFB (FRF‐CFB) technology. The CFB is a technology which is capable of quantifying the amplitude and phase coupling between harmonics of pile resonance oscillations caused by a damage. However, in practices, the amplitude and phase coupling between harmonics of pile resonance oscillations may be caused also due to the phase‐coupled harmonics of an interference imposed by an excitation source (e.g., shaker). Therefore, the novel diagnosis technology, FRF‐CFB, which detects nonlinearity caused solely by a structural damage, is proposed and implemented for real‐scale precast concrete piles. It is found that the FRF‐CFB technology successfully identifies the damaged piles. Finally, the diagnosis based on the conventional pile integrity testing, conducted on the same piles, is presented for comparisons with the FRF‐CFB technology and with the CFB technology.
This research work aims to optimize a concrete foundation designed to support a high-capacity motor-driven compressor. The structure has plane dimensions of approximately 15 m × 11 m and a height of ...1.5 m. The concrete block is to be supported by 20 concrete piles approximately 8.5 m in length and 0.5 m in diameter. The investigated structural system is subjected to deterministic dynamic loadings due to the nature of the equipment supported by the concrete foundation. The main objective of the optimization is to reduce the structural volume through the analysis of its dynamic response, in order to minimize the cost of the concrete volume. In this research work, Genetic Algorithms (GAs) are used through an appropriate interface between ANSYS and MATLAB software. The results of this study show that through the GAs it is possible to achieve a considerable volume reduction with respect to the original volume of concrete used in the design of the foundations structural system.
•We examine the effects of a multi-hazard loading scenario using cyclic wind loads and earthquakes on concrete foundations as a case study.•The damage from such loads acting concurrently will be ...significant.•A reliability model for this analysis is developed and tested.•A finite element model is developed in ANSYS® and also used for the analysis.•The results point to an increase in the probability of failure of the foundation.
In order to assess the vulnerability of structural systems to multiple hazards occurring simultaneously, it is necessary to carry out a multi-hazard analysis of the system. Over time, and under continuous, albeit varying cyclic loading from wind forces, there may be a reduction in the structural integrity of structural systems due to fatigue that increases their vulnerability to additional non-typical loads such as seismic and impact. This results in multi-hazard loading scenario not typically considered in current design. This paper aims to present research directed towards numerically estimating the possible effect of a seismic load (earthquake) on a wind turbine foundation that has undergone fatigue over time from constant exposure to wind forces. Although the practical effect of wind induced fatigue on foundations may be relatively small, its cumulative behavior over time reduces the foundation’s capacity making it more susceptible to high impact loads such as seismic events. The analysis is done by considering the two loading events in a fault tree analytical procedure with each event taken as independent and combined together in series. Reliability analysis utilizing the computational tools MATLAB and finite element analysis (using ANSYS) is carried out to understand the behavior of the structure under each specific and combined load effects. The resulting analyses carried out using reliability analysis methods such as first order second moment reliability method and Monte Carlo simulations show a definite decrease in the foundation’s performance and a concurrent increase in its probability of failure within the structure’s design life. The results of this study will help understand the behavior of a simplified structure under the combined effect of these load types thus leading to a more accurate depiction of the actual behavior of structures.
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