132 publications from this institution
One of the common damages in existing highway bridges is the damage at the bottom corners or edges of the reinforced concrete beams or box girders induced by an impact of trucks exceeding the allowable height clearance of the bridges. In this study, a collision protection and scarifying system is developed, and it utilizes advanced materials/structures to protect highway bridge girders. The proposed collision protection and scarifying system is in a new “I-Lam” (Impact Laminate) configuration and bolted and/or bonded to the bottom portions or edges of concrete girders. The I-Lam panels are made of a composite sandwich construction with multi-layer aluminum honeycomb core and top and bottom thin face sheets, and they are developed/designed specifically for impact damage protection of bridge girders (e.g., concrete girders). Design criteria and guideline for I-Lam are developed, and the analysis, optimal design, and quality control tests of the collision protection system are conducted. Smart piezoelectric sensors are integrated with the I-Lam panels for monitoring the performance of the collision protection system. The collision protection system is implemented in an identified bridge. The developed smart bilayer honeycomb I-Lam sandwich is capable of reducing the transferred contact force dramatically, absorbing/mitigating impact energy, protecting the underneath concrete structures by system scarifying and core crushing, and monitoring the impact incident with smart piezoelectric sensors, and it is applicable to protecting other structures (e.g., steel girders, columns) from accidental vehicle impact in the highways.
In this article, the tension–tension fatigue behavior of newly developed pultruded E-glass/polyurethane composites is characterized, and an improved model for fatigue life prediction including the effects of stress ratio, frequency, and mean stress as the testing parameters is proposed. The proposed non-dimensional analysis is in good agreement with the predictions of existing available fatigue data and present testing data. The model is consistent with the Goodman line relationship and has a clear physical meaning. The fatigue test data of E-glass/polyurethane composites are analyzed using the proposed model, and they are compared with other common E-glass fiber-reinforced plastic composites. It indicates that the E-glass/polyurethane composites are more fatigue sensitive but comparable to other fiber-reinforced plastic composites in their fatigue behaviors. The effects of stress ratio, frequency, and mean stress on fatigue life of E-glass/polyurethane composites are studied and discussed. The corresponding S–N curve and its bounds based on 95% confidence are provided for the pultruded E-glass/polyurethane composites. The present fatigue model can be used as a useful tool to characterize the effects of various parameters on the fatigue behavior of fiber-reinforced plastic composites, and it provides the fatigue life prediction for newly developed pultruded E-glass/polyurethane composites.
Foundation settlement is a common issue for bridges, which not only generates additional static stresses in continuous bridge members but also may affect the dynamic interaction between the bridge and vehicle traveling over it. In this paper, a new bridge-vehicle model with consideration of foundation settlement effect is created through the principle of virtual works to investigate the settled bridge and vehicle interaction responses. The correctness and accuracy of the model are validated with theoretical and numerical results. Based on the proposed model, numerical simulations have been conducted using the Newmark’s β method to investigate the effects of settlement mode, vehicle traveling speed, road surface roughness and boundary condition. It is shown that foundation settlement has a significant effect on impact factors of the bridge at high vehicle speeds, and road surface roughness may act together with the settlement to have a coupling effect, which needs special attentions in bridge design.
Delamination is currently a difficultly-detectable form of damage in composite laminate materials. This paper experimentally validates an innovative method that more easily detects delamination damage within composite materials through the covariance of energy change. Lamb waves were introduced and recorded through an actuator and sensors made of piezoelectric material. The data was then analyzed through the Fast Fourier Transform (FFT). Using the data from FFT, the idea of covariance of energy change was suggested to correlate with defect characteristics. By comparing the covariance of energy change in beams with different delamination sizes and depths, correlations between the covariance of energy loss and defect characteristics were developed. With these correlations, the severity of these damages was quantified.
A new method to filter the effect of camera motions through background templates is proposed in this manuscript. Moreover, the effect of template sizes and
Delamination is currently a difficult detectable form of damage in composite laminate materials. This paper presents a method to more easily detect delamination damage within composite materials using finite element analysis modeling, through the covariance of energy change. Lamb waves were introduced and recorded through an actuator and sensors made of piezoelectric material. The data were then analyzed through the fast Fourier transform (FFT). Using the data from the FFT, the idea of covariance of energy change was suggested to correlate with defect characteristics. By comparing the covariance of energy change in beams with different delamination sizes, thicknesses, and depths, correlations between the covariance of energy loss and defect characteristics were able to be developed. With these correlations, the severity of these damages was able to be quantified.
In this paper, a framework is developed for the purpose of detecting small hidden objects through weigh-inmotion data for security purposes. The 3 statistical principle is used to separate the outlier events and noises with normal traffic flow and the collected wheel loads are further used to identify the possible locations and weights of hidden objects. Correspondingly, an in-lab experiment has been conducted to validate the algorithm and excellent results have been reached. The system can be implemented at any security port and help to increase the security screening efficiencies at these locations.
: Early-age carbon dioxide curing (EACC) is one of the promising methods for carbon dioxide (CO2) sequestration and utilization in cement-based materials which, in addition to CO2 mineralization, has the potential to improve the engineering properties of construction materials. Understanding the effect of EACC on the electrochemical properties of hydrated cement provides an insight for its hydration evolution and mechanical performance. In this study, the effect of EACC on the electrical properties of cement pastes with various water contents using electrochemical impedance spectroscopy (EIS) was investigated. The conventional method for interpretation of EIS data is fitting Nyquist plots by equivalent circuits models (ECMs) however this method does not provide accurate analysis at early age hydration. Instead, the distribution of relaxation times (DRT) method for extracting parameters of electrical interfaces and time domain properties was proposed. Using the DRT analysis, two peaks are identified in the EIS data representing two interfaces in the electrochemical cell including the electrode-cement and pore structure interfaces, and the parameters of each interface were extracted. The results show that cement bulk resistance, the resistance of the electrode-cement interface, and the pore structure resistance of the cement paste profile increased with respect to CO2 curing.
Glass fiber-reinforced polymer (GFRP) reinforcements are taken as an alternative solution for the deterioration of civil infrastructures. GFRP bars have received increasing attention due to low cost compared to carbon fiber-reinforced polymer (CFRP) bars. Bond characteristic of GFRP bars in concrete is the most critical parameter for implementation of the material to the corrosion-free concrete structures. Unlike steel reinforcement, GFRP materials behave anisotropic, non-homogeneous and linear elastic properties, which may result in different force transfer mechanism between reinforcement and concrete. With the purpose of covering the most valuable contributions regarding bond mechanism in the past work, a comprehensive review focusing on the failure mode and bond strength is carried out in this paper. A database consisted of 682 pullout-test specimens was created to observe the factors affecting bond behavior. Basic relationship between bond strength/slip and factors was analyzed accordingly. In addition, the development of bond degradation under environmental conditions, such as freezing-thawing cycling, wet-dry cycling, alkaline solutions and high temperature was presented thereafter. These environmental influences need to be further investigated.
Large scale fiber reinforced polymer (FRP) composite structures have been used in highway bridge and building construction. Recent applications have demonstrated that FRP honeycomb sandwich panels can be effectively and economically applied for both new construction and rehabilitation and replacement of existing structures. This paper is concerned with impact analysis of an as-manufactured FRP honeycomb sandwich system with sinusoidal core geometry in the plane and extending vertically between face laminates. The analyses of the honeycomb structure and components including: (1) constituent materials and ply properties, (2) face laminates and core wall engineering properties, and (3) equivalent core material properties, are first introduced, and these properties for the face laminates and equivalent core are later used in dynamic analysis of sandwich beams. A higher-order impact sandwich beam theory by the authors [Yang MJ, Qiao P. Higher-order impact modeling of sandwich beams with flexible core. Int J Solids Struct 2005;42(20):5460–90] is adopted to carry out the free vibration and impact analyses of the FRP honeycomb sandwich system, from which the full elastic field (e.g., deformation and stress) under impact is predicted. The higher order vibration analysis of the FRP sandwich beams is conducted, and its accuracy is validated with the finite element Eigenvalue analysis using ABAQUS; while the predicted impact responses (e.g., contact force and central deflection) are compared with the finite element simulations by LS-DYNA. A parametric study with respect to projectile mass and velocity is performed, and the similar prediction trends with the linear solution are observed. Furthermore, the predicted stress fields are compared with the available strength data to predict the impact damage in the FRP sandwich system. The present impact analysis demonstrates the accuracy and capability of the higher order impact sandwich beam theory, and it can be used effectively in analysis, design applications and optimization of efficient FRP honeycomb composite sandwich structures for impact protection and mitigation.
Bearing capacity of cast-steel joint with branches in a tree-like column structure is important when adopted, since failure of the joint will surely lead to the collapse of its whole superstructure. In this paper, by using the means of numerical simulation and experimental verification, mechanical behavior of three-branch cast-steel joints in the tree-like column structure under eccentric load was studied. A typical full-scale cast-steel joint with three branches was first tested under eccentric loads. Numerical analysis of the cast-steel joint with three branches under eccentric load was then carried out through ANSYS and SolidWorks. Failure mechanisms of this kind of joint were analyzed and the main failure mode was summarized. Finally, the formula for predicting load-carrying capacity of the cast-steel joint with branches under eccentric forces was proposed. The results showed that the failure mode of the joint under eccentric load is the buckling failure at the end of the compression side of the main pipe, and the formula based on the main failure mode is applicable in engineering and building designs.
Safety of cable net structures has been threatened due to rising conflicts and the possibility of exposure to blast load. Pre-tensioned cable nets are geometrically nonlinear problems and the nonlinearity can be addressed by using the linearized stiffness matrix method (LSM). On the other hand, the effect of negative phase pressure of blast wave is usually ignored in practice while the research indicates its significance on the dynamic response of the system. In this paper, LSM method is used to study the effect of negative phase pressure and other factors such as charge weight, standoff distance, pretension level, and modal frequency on cable net structures. The effect of glass panel failure on the system response is also studied by removing the corresponding wave pressure acting on the failed glass panels. Accuracy of the LSM method is evaluated through comparison between the proposed numerical and closed-form solution. The results indicate the significance of the effect of negative phase pressure on the system response, which is pronounced at lower TNT weights and more flexible structures. The major effect of negative phase pressure is on the outward displacements, which exhibits up to 25% more displacements for the studied cable net when the negative phase pressure is considered. Failure of glass panels and consequent pressure release in negative phase can cause increase in the subsequent displacements. LSM method can reliably predict the system response as far as displacements are not too large. However, at very large displacements, LSM method significantly overestimates the predicted displacements.
