Finite Element Analysis of Steel Fiber Reinforced Concrete (SFRC): Validation of Experimental Shear Capacities of Beams

AbstractFinite element models are analyzed and validated with the experimental shear capacities of steel fiber reinforced concrete (SFRC) as well as plain concretes. In this work, steel fibers with low aspect ratio which are commonly available in Bangladesh are used and sufficient capacity enhancements are attained. Two different aggregate types are used to make the SFRC and plain concrete beam specimens, i.e. stone and brick, and also modelled in the finite element (FE) platform of ANSYS 10.0 with SOLID65 element. The experimental plan intended to investigate the shear capacity enhancement of three different types of beam specimens, i.e. single shear, double shear and flexural shear. All the specimens are tested in the 1000kN capacity digital universal testing machine (UTM) and the strain data are obtained from digital image correlation technique (DICT) using high definition (HD) images and high speed video clips. Test results showed the increase in shear capacity of about 30% to 170% of beams made of SFRC with an indication of increase in ductility. FE models are analyzed extensively and validated with the experimental stress-strain behaviours by optimizing the Poisson's ratio, modulus of elasticity, tensile capacity and stress-strain behaviours. FE models showed the same structural response and failure modes as found in experimental investigation. This paper can contribute to the construction industry of Bangladesh about SFRC with reliable experimental data and FE analyses

Effect of structural nonlinearity on probabilistic risk assessment of offshore wind turbine including inelastic soil medium

This research intends to evaluate the influence of structural nonlinearity on the seismic risk of an offshore wind turbine with respect to linear analysis. The structural nonlinearity is presented into the structure, as materially nonlinear, by calibrating plastic hinge at the end of the elastic beam-element of the structure. To guarantee ideal circumstance for seismic analysis, this study includes inelastic soil stratum by using an equivalent linear approach. Monte Carlo simulation is performed by means of seismic vulnerability of the structural system. The research presents a study of a large amount of simulation over the nonlinear and linear structures considering the random character of basic variables of soil under selective earthquakes. The earthquakes having different source-to-site (STS) distances ranging from 7 to 145 km have consistency with the soil parameters. This rigorous implementation is done to accomplish site-specific dynamic analysis. Illustrative results obtained from nonlinear and linear dynamic analysis are compared. The overall finding shows that the nonlinear structure produces highest estimated uncertainty compared to the linear structure. Another termination can be addressed that the earthquake with less STS distance (7.29 km) causes the highest level of destruction to the structure

Time-series analysis of GPS measurements for long-span bridge movements using wavelet and model prediction techniques

This study aims at assessing the safety behavior of the Incheon long-span bridge using high rate (10 Hz) geodetic monitoring global positioning system (GPS). The time series of wavelet spectrum analysis is utilized to assess the dynamic behavior of the bridge. The coefficients and model errors of the time series autoregressive-moving average (ARMA) model are used to evaluate the movement performances of the bridge. The results show that: (i) the accuracy of GPS measurements to extract the dynamic behavior of the bridge is 97.27% when compared with the design results. (ii) the behavior of the bridge is within the safety limits of the bridge design with minimum observed changes for the historical GPS measurements in time and frequency domains, the mean deflection of bridge deck is 8.26 mm and frequency changes of bridge is 0.004 Hz compared with the design results. (iii) the time series analysis of the wavelet spectrum and ARMA model coefficients can be used to detect the significant frequency changes and study the rigidity of the bridge performance, respectively; and the both methods are found to be suitable techniques to estimate the performance changes of the GPS measurements in the time and frequency domains during the monitoring time period

Influence of soil-structure interaction on seismic responses of offshore wind turbine considering earthquake incident angle

Displacement response and corresponding maximum response energy of structures are key parameters to assess the dynamic effect or even more destructive structural damage of the structures. By employing them, this research has compared the structural responses of jacket supported offshore wind turbine (OWT) subjected to seismic excitations apprehending earthquake incidence, when (a) soil-structure interaction (SSI) has been ignored and (b) SSI has been considered. The effect of earthquakes under arbitrary angle of excitation on the OWT has been investigated by means of the energy based wavelet transformation method. Displacement based fragility analysis is then utilized to convey the probability of exceedance of the OWT at different soil site conditions. The results show that the uncertainty arises due to multi-component seismic excitations along with the diminution trend of shear wave velocity of soil and it tends to reduce the efficiency of the OWT to stand against the ground motions

GPS performance assessment of cable-stayed bridge using wavelet transform and Monte-Carlo techniques

Global Positioning System (GPS) is an emerging tool of Structural Health Monitoring (SHM) that can be used to help in understanding the nature of dynamic deformation/vibrations and explore the factors affecting the structural damage in three directions. In this study, the GPS geodetic survey techniques has been used on the Incheon Long-Span Cable-Stayed Bridge (ILSCSB) in Korea. Both of the bridge deck and pylon have been monitored using the high-rate (10 Hz) GPS measurements in lateral, longitudinal and vertical directions. The time series analysis has been carried out to evaluate the three-dimensional structural behavior of the bridge in time and frequency domains. The multi-filtering approach, wavelet transform, and Monte Carlo simulation of GPS data have been applied, including the fundamental frequency, the dominating deformation, and energy content of the bridge. The results reveal that the proposed methods based on the GPS-SHM system provide a potential technique for monitoring the dynamic characteristics of bridges with adequate performance. Furthermore, it can help in confirming the safety of a bridge under dynamic loads

Distributed plasticity approach for the nonlinear structural assessment of offshore wind turbine

This study provides an insight of the nonlinear behavior of the Offshore Wind Turbine (OWT) structure using the distributed plasticity approach. The fiber section beam-column element is applied to construct the finite element model. The accuracy of the proposed model is verified using linear analysis via the comparison of the dynamic characteristics. For collapse risk assessment of OWT, the nonlinear effects considering the earthquake Incident Angle (IA) have been evaluated first. Then, the Incremental Dynamic Analysis (IDA) has been executed using a set of 20 near-fault records. Lastly, fragility curves are developed to evaluate the vulnerability of structures for different limit states. Attained results justify the accuracy of the proposed approach for the structural response against the ground motions and other environmental loads. It indicates that effects of static wind and wave loads along with the earthquake loads should be considered during the risk assessment of the OWT structure

Multiple tuned mass damper for multi-mode vibration reduction of offshore wind turbine under seismic excitation

With the wide spreads of the wind energy production industry, the demand for the safe and feasible design of wind turbine structures is growing swiftly. The magnificent deployment of wind turbines in hostile environments with high seismic hazard, has lead engineers to consider more comprehensive way of seismic design, and control technics of a gigantic structure like jacket supported offshore wind turbine (OWT). The current research provides an overview to alleviate the dynamic structural responses of the jacket supported OWT due to the seismic loads associated with static wind and wave loads. Multiple tuned mass damper (MTMD) has been installed at the top and base of the turbine tower corresponding to the mode shapes of the structure. The MTMD parameters have been optimized based on response surface methodology (RSM). The performance of MTMD following the multi-mode control strategy seems to be prominent in suppressing the first two vibrational modes. To evaluate the proposed strategy, frequency response function (FRF), fast Fourier transforms (FFT), peak and lateral displacements of the tower, root mean square (RMS), shear and moment have been investigated through the uncontrolled and controlled structures. In addition, the practicability of the MTMD system is also compared with the single tuned mass damper (STMD)