Zainah Ibrahim

Numerical investigation of the vortex-induced vibration of an elastically mounted circular cylinder at high Reynolds number (Re = 104) and low mass ratio using the RANS code

This study numerically investigates the vortex-induced vibration (VIV) of an elastically mounted rigid cylinder by using Reynolds-averaged Navier–Stokes (RANS) equations with computational fluid dynamic (CFD) tools. CFD analysis is performed for a fixed-cylinder case with Reynolds number (Re) = 104 and for a cylinder that is free to oscillate in the transverse direction and possesses a low mass-damping ratio and Re = 104. Previously, similar studies have been performed with 3-dimensional and comparatively expensive turbulent models. In the current study, the capability and accuracy of the RANS model are validated, and the results of this model are compared with those of detached eddy simulation, direct numerical simulation, and large eddy simulation models. All three response branches and the maximum amplitude are well captured. The 2-dimensional case with the RANS shear–stress transport k-w model, which involves minimal computational cost, is reliable and appropriate for analyzing the characteristics of VIV.

Optimization of the Geometries of Biconical Tapered Fiber Sensors for Monitoring the Early-Age Curing Temperatures of Concrete Specimens

Structural health monitoring has received significant attention in research and involves the integration of sensor techniques, smart materials, data interrogation and transmission, computational power and processing ability inside the structures. A geometrical optimization procedure using biconical tapered fiber sensors is proposed for monitoring the early-age curing temperatures of concrete specimens in this article. The geometries of the sensors are theoretically optimized by the ray-tracing theory. The results of the theoretical analysis show that the performance of the sensors is heavily influenced by Evanescent Waves, which are due to the tunneling rays and are fully escaped by tapering the fiber. The effects of the geometrical parameters, which include the taper ratios, taper lengths, and ray launch angles, as well as the surrounding temperatures, on the behavior of the sensors are studied numerically. The numerical results demonstrate that higher performance of the proposed optimized sensors can be achieved by a longer taper length and smaller taper ratio combined with an initial ray launching angle of 0.01 rad. The findings in this article prove that the proposed sensor has the ability to determine the setting time of concrete since the setting process is accompanied by a temperature change in the concrete.

Approach to Reduce the Limitations of Modal Identification in Damage Detection Using Limited Field Data for Nondestructive Structural Health Monitoring of a Cable-Stayed Concrete Bridge

The objective of the study was to propose a technique to reduce the limitations of modal identification in damage detection using reduced field data for nondestructive structural health monitoring of a cable-stayed concrete bridge. Simply supported bridge models were constructed with predetermined damage at the midspan of the bridge. The technique necessitated the performance of linear and eigen analyses on the control beam and nonlinear analysis on the bridge with damage. Residuals from regression of the mode shape using the Chebyshev rational series on the modal frequencies and transformation and application into the fourth-order centered finite-divided-difference formula were shown. The use of the regressed-mode shapes for the RC bridge model showed very large residuals around the areas of the damage. The results showed that the method was successful in assisting to reduce the limitations of modal identification in locating damage on a bridge model with limited field data and was comparable to other techniques proposed by other researchers in terms of its simplicity.

Numerical investigation of vortex-induced vibration of an elastically mounted circular cylinder with One-degree of freedom at high Reynolds number using different turbulent models

This study presents numerical investigation for flow around cylinder at Reynolds number = 104 using different turbulent models. Numerical simulations have been conducted for fixed cylinder case at Reynolds number = 104 and for cylinder free to oscillate in cross-flow direction, at Reynolds number O (104), mass–damping ratio = 0.011 and range of frequency ratio wt = 0.4–1.4 using two-dimensional Reynolds-averaged Navier–Stokes equations. In the literature, the study has been conducted using detached eddy simulation, large eddy simulation and direct numerical simulation which are comparatively expensive in terms of computational cost. This study utilizes the Reynolds-averaged Navier–Stokes shear stress transport k-ω and realizable k-ε models to investigate the flow around fixed cylinder and flow around cylinder constrained to oscillate in cross-flow direction only. Hydrodynamic coefficients, vortex mode shape and maximum amplitude (Ay/D) extracted from this study are compared with detached eddy simulation, large eddy simulation and direct numerical simulation results. Results obtained using two-dimensional Reynolds-averaged Navier–Stokes shear stress transport k-ω model are encouraging, while realizable k-ε model is unable to capture the entire response branches. In addition, broad range of “lock-in” region is observed due to delay in capturing the transition from upper to lower branch during two-dimensional realizable k-ε analyses.

Analysis of influential factors for predicting the shear strength of a V-shaped angle shear connector in composite beams using an adaptive neuro-fuzzy technique

The V-shaped angle shear connector is recognized as to expand certain mechanical properties to the shear connectors, contains adequate ductility, elevate resistance, power degradation resistance under cyclic charging, and high shear transmission, more economical than other shear connectors, for instance, the L-shaped and C-shaped shear connectors. The performance of this shear connector had been investigated by previous researchers (Shariati et al. in Mater Struct 49(9):1–18, 2015), but the strength prediction was not clearly explained. In this investigation, the shear strength prediction of this connector was analyzed based on several factors. The ultimate purpose was to investigate the variations of different factors that were affecting the shear strength of this connector. To achieve this aim, the data (concrete compression strength, thickness, length, height, slope of inclination, and shear strength) were collected from the parametric studies using finite element analysis results for this purpose were input using the ANFIS method (neuro-fuzzy inference system). The finite element analysis results were verified by experimental test results. All variables from the predominant factors that were affected the shear strength of the shear connector (V-shaped angle) were also selected by using the ANFIS process. The results exhibited that the proposed shear connector (V-shaped angle) contained the potentiality to be used practically after several improvements. One option might be the improvement of the testing process for different predictive models with more input variables that will improve the predictive power of the created models.

Numerical investigation of flow around cylinder at Reynolds number = 3900 with large eddy simulation technique: Effect of spanwise length and mesh resolution:

Flow around a cylinder at a Reynolds number of 3900 was studied using large eddy simulation with ICEM CFD and Fluent tools for meshing and analysis, respectively. Although this issue has been explored by numerous researchers, a discrepancy still exists in the results, particularly in calculating the angle of separation, recirculation length, and statistics in the wake region behind the cylinder. In addition, the effect of spanwise grid and near-field grid resolution on the wake region needs to be addressed. This study reviews previous work and performs analyses according to the literature recommendations. The effect of spanwise length (4D, 8D, and 16D), mesh resolution in the spanwise direction (1, 10, 20, 40, 60, 80, and 160 elements), and near-field grid on calculating recirculation length, angle of separation, and wake characteristics is investigated. Hydrodynamic values and pressure distribution around the cylinder are analyzed. The wake behind the cylinder is investigated within 10 diameters. This study concluded that compared with spanwise length, mesh resolution in the spanwise direction and near-field grid are more important factors for good-quality results.

Use of Tapered Optical Fiber Sensors in Study of the Hydration Process of Cement Paste

In this paper, the tapered multimode plastic optical fiber sensor is used for the experimental study of the early-age hydration process of cement paste. A high reactive power is mixed as a specimen, in which a tapered fiber sensor is embedded to measure the liberated heat (temperature). The sensor characteristics are determined and calibrated by an embedded thermocouple, which have a sensitivity of 0.0293 mV/°C and resolution of ±0.34°C. The experimental studies are carried out for the host specimen with different sizes, various water/cement (w/c) ratios, as well as different ambient temperatures. From the experimental results, the curing temperature and setting time are determined by monitoring the curing temperature curves as the curing progressed. The curing temperature rose with increasing mould sizes, increasing w/c ratio, and increasing ambient temperature. The setting time could be shortened by a smaller size of a specimen, lower w/c ratio, and higher ambient temperature.

P-Δ and End Rotation Effects on the Influence of Mechanical Properties of Elastomeric Isolation Bearings

AbstractSeismic isolation systems constitute an accepted and simple technique for earthquake protection of structural systems and sensitive components. This approach has considerable potential in preventing the structures and their equipment from earthquake destruction. For predicting the behavior of an isolation bearing, Haringx’s theory is usually employed. According to this theory, the mechanical properties of an elastomeric isolation bearing can be predicted and described. Many investigators have proposed a nonlinear, mechanical model for multilayer elastomeric bearings. However, in previous theoretical and experimental studies, the effects of initial rotation at the ends of the bearings have been neglected. In this study, Haringx’s theory is extended and an analytical method is presented by considering the initial rotations of the upper and lower ends of multilayer rubber bearings as new boundary conditions. Three boundary conditions have been considered for modeling the elastomeric isolation bearing...

Flexural Behaviour of Concrete Beams Bonded with Wire Mesh-Epoxy Composite

This paper investigates the flexural performance of plain concrete beams bonded with wire mesh-epoxy composite. A total of four beam specimens were prepared and tested. Three specimens were bonded with same amount of wire mesh-epoxy composite with varying composite width and one plain concrete specimen was used as a control. The effect of wire mesh-epoxy composite on enhancing the flexural behaviour of concrete beams as well as the effect of different configurations of composite was studied. Test results showedthat the wire mesh-epoxy composite increased the flexural strength of concrete beams. The increase in energy absorption of bonded beams was remarkable. In addition, specimen with large composite width showed better behaviour with respect to energy absorption capability.

Monitoring of Curing Temperature of Early-Age Cement Paste Using Biconical Tapered Fiber Sensor

In this paper, a biconical tapered fiber sensor is applied to monitor the temperature of cement paste during curing process. A simple sensing principle of the proposed sensor is presented by analyzing the V-number of leaky rays. An experimental is carried out by tapering the plastic multi-mode step-index fiber to measure the temperature of the cement paste. The numerical result shows that the V-number of leaky ray is increasing with the raised in temperature. The experimental results are in agreement with the results from the theoretical analysis.