Laminated rubber bearing pad (LRBP) is widely used in small to medium-span highway bridges. They are directly placed between piers and girders to allow the bridge span to have horizontal movement and to transfer the gravity loads from decks to piers. Although LRBPs are not designed for seismic loads, their application can partially isolate the superstructure from the substructure keeping the piers intact during earthquake events. However, recent investigations indicate that large relative displacement between superstructure and substructure caused by sliding between girders and LRBPs can cause expansion joint or bridge span failure. As such, suitable restrainers should be implemented to control the potential large displacement. Among all types of restrainers, passive energy devices such as viscous dampers have shown a remarkable capacity in dissipating the earthquakes energy. This study aims at investigating the effectiveness of VD-LRBPs system, viscous dampers in conjunction with LRBPs, in controlling the large displacement between decks and piers. Accordingly, a 3D Nonlinear Time History Analysis (NTHA) was conducted on a case study RC bridge model under several earthquakes. OpenSees, an open sources finite element software, was used for the analysis. The relative displacements between decks and piers as well as the force in the piers, were recorded for two cases: 1- with only LRBPs and 2- with viscous dampers and LRBPs (VD-LRBP system). The results indicate that adding viscous dampers can reduce the relative displacement up to 60 percent. Also, it can reduce the potential residual displacement post-earthquakes to near zero.
With the increase in population, surface transportation has significantly increased, highlighting the need to maintain reliable and safe civil infrastructures. Bridges can be considered the most critical element in transportation infrastructure. Accordingly, they require periodic inspection to prevent any failure caused by aging and environmental impacts. Over the years, visual inspection has been practiced the most due to its simplicity. However, detection of small and internal cracks and defects requires more advanced techniques. To address this, various non-destructive testing (NDT) methods have been developed and implemented in recent decades. With the advance of technology, opportunities for developing more advanced and effective NDT methods have been created. To achieve the development of such advanced techniques, the knowledge of available methods and their future trends becomes necessary. This paper gathers in one place all the relevant information regarding existing non-destructive testing for steel bridges. Furthermore, the future direction and recent innovations in this field, including the application of robots, sensors, and drones for fast and efficient evaluation of steel bridges are discussed. The parameters for selecting the most appropriate NDT method for specific cases are explored. The methodology, and pros and cons of each technique are also presented. It is expected that the results of this study pave the way for development of new methods and improvement of currently practiced NDT techniques for steel bridges.
The use of fiber reinforced polymer (FRP) materials has been on the rise in bridge construction industry. They have been mostly utilized for strengthening purposes, especially as externally bonded reinforcement for columns, slabs, and beams. Their lightweight, flexibility and ease of installation, and higher strength offer an ideal solution for increasing the axial, bending, and shear resistance of existing concrete elements, as well as restoration and retrofitting of damaged members. FRP bars have also been used as internal reinforcement for concrete structural elements, providing corrosion-resistant alternatives to conventional steel reinforcements. Although the application of FRP for concrete members has offered many advantages, there have been issues and concerns associated with their long-term performance including their debonding from a concrete surface or within a concrete element. Accordingly, despite their durability, concrete elements strengthened/reinforced with FRP materials need to be inspected periodically to detect potential issues and hence prevent any premature failures. This study investigates Non-Destructive Testing (NDT) methods applicable to inspection of in-service FRP reinforced/strengthened concrete (FRP-RSC) bridge elements. Accordingly, this study first introduces damages and anomalies attributed to FRP reinforced/strengthened concrete bridge elements, and causes are discussed. The study includes a review of some promising NDT methods for the detection of these damages. The results of this study are expected to provide the inspection community more clarity in the application of NDT to FRP reinforced/strengthened concrete.
This paper investigates the use of non-contact laser vibrometers for continuous or periodic bridge monitoring and damage detection through the detection of changes in the bridge's natural frequencies. For this purpose, the vibrations of a full-depth precast-prestressed voided slab bridge and a steel girder bridge were measured under normal traffic using a laser vibrometer. Detailed finite element (FE) models were developed to study the bridge dynamic behavior for various damage scenarios, including longitudinal joint damages in a concrete bridge deck and a full-depth girder fracture in a steel girder bridge. In the concrete bridge deck, longitudinal reflective cracking on the deck surface and leakage had hinted at some level of damage at the joints. The bridge dynamic analysis showed that modal parameters in bridges with precast deck panels are sufficiently sensitive to changes in the state of the panel joints and, therefore, can be used for identifying joint damage. The results clearly confirmed the visible evidence of the damage. For the steel-girder bridge, the results of the dynamic analysis also indicated a noticeable frequency change in the bridge's natural frequencies after a fracture at a level that can be effectively detected with bridge frequency monitoring. Moreover, the proposed approach proved to be more cost-effective and less disruptive than standard monitoring approaches and, at the same time, capable of predicting damages from relatively small vibration amplitudes. This approach can be used to warn of potential damages between planned inspection intervals and to detect damages otherwise hidden from the eye during routine inspections.
There is a higher necessity for a safe and intelligent railway transportation system as an important foundation for the smart city concept. The need to develop real-time condition monitoring technology for limited access parts of high-speed trains, such as wheels, is an important challenge. This paper develops an Internet of Things (IoT) based nondestructive evaluation (NDE 4.0) platform for autonomous inspection of in-service train wheels. The proposed NDE 4.0 platform consists of a wireless transmission module (WTM) which is used to remotely transfer power from the bogie to its surrounded wheels and also to receive back the data from sensors installed on the axle box of the wheels. The WTM’s circuits were designed and simulated in LTSpice software. This paper reveals the great potential of using cyber-physical systems to intelligently manage big data and autonomously control National Railway Networks (NRN).
Motivated by previous successes in the development of two-dimensional (2D) based electronic nose, we investigate the potential application of metal-decorated phosphorene-based sensor for detection of formaldehyde using density functional theory (DFT) and nonequilibrium Green’s function (NEGF) methods. The most stable adsorption configurations, adsorption sites, adsorption energies, charge transfer, and electronic properties of formaldehyde on the pristine and Pd-decorated phosphorene are studied. Our results indicate that formaldehyde is chemisorbed on Pd-decorated phosphorene via strong covalent bonds, and quick recovery time (3.58 sec) under UV exposure and at the temperature of 350 K, suggesting its potential application for gas sensors. The results reveal that Pd-decorated phosphorene can detect formaldehyde with high sensitivity of 3.8 times greater than pristine phosphorene. Our results demonstrate the potential application of phosphorene for detection of formaldehyde as an important lung cancer biomarker.
The application of accelerated bridge construction (ABC) methods is becoming more widespread owing to their many advantages. In this construction method, prefabricated bridge elements are assembled on-site by establishing in-situ joints to minimize on-site construction time. Despite the improved life-cycle performance and cost benefits of ABC bridges, some concerns exist about the degrading environmental effects on the joints and invisible internal damages. In this study, the long-term performance of an ABC bridge that had been in service for more than 50 years was investigated utilizing machine-learning processes. Observation of reflective cracking on the deck surface and leakage through the joints in this bridge indicated some damage to the bridge longitudinal joints. Damages to the joints are not always visible, nor their extent is known. Therefore, a new damage detection approach is proposed that uses the results of a series of load tests as input in machine-learning techniques with the ultimate aim of detecting the location and severity of joint damages with a high level of certainty. The proposed approach uses the bridge responses obtained from a detailed finite element (FE) model under the assumption of various damage scenarios and predicts the potential damages using the training process of machine-learning algorithms and the actual bridge responses. The results show that the supervised learning algorithm successfully estimated the location and amount of damage in the bridge joints.
In this paper, an auxetic design is proposed for the flexible membrane of a piezoelectric pulse sensor and computationally analyzed for a high-sensitivity vibration sensing in micro electro-mechanical system (MEMS). Auxetics are metamaterial structures with negative Poisson’s ratio which enables sensor’s flexible diaphragm to be expanded in both longitudinal and transverse directions easily. The sensitivity of a pulse sensor with an auxetic membrane was studied and compared to an equivalent plain membrane when the substrate was under harmonic bending. The sensing response was determined for the both models using detailed Finite Element Model (FEM) simulations. The sensor with the auxetic membrane demonstrated excellent sensitivity output over a harmonic pressure input which shows its strong potential for high-sensitive MEMS sensing applications. A detailed fabrication process is also discussed.
The Surface Response to Excitation (SuRE) method is a guided-wave based Structural Health Monitoring (SHM) technique. Up to date, no analytical model has been developed and validated for the SuRE method. This paper experimentally and analytically investigates the delamination between two plates using the SuRE method in conjunction with the COMSOL Multiphysics software. Simulation results are validated by experimental results. The results showed that the findings from the analytical approach correspond with the experimental results and can be effectively used for studying delamination. This approach can be utilized for different types of structures with similar conditions.
Low reliability and high maintenance cost of using power and data cables are two main reasons motivating the application of the self-powered wireless sensors for structural health monitoring (SHM) systems in bridge structures. On the other hand, energy harvesting systems have been introduced as a solution for the current limitations of the batterypowered wireless sensors associated with the finite life-span of batteries and their replacements. The objective in this paper is to propose a new optimized nonlinear energy harvesting concept, namely Bistable Energy Harvesting (BEH) system, for smart SHM of bridge structures. In this study, a dynamic analysis of the energy harvesting system for cablesupported bridges subject to wind-induced vibration is carried out and the feasibility of the energy harvesting device is investigated. This paper presents efficient linear and nonlinear energy harvesting systems for wireless monitoring of long-span cable-supported bridges. It is shown that level of the extracted energy from such energy harvesting system is quite sufficient to supply energy for self-powered sensors of a bridge health monitoring system. This study is to promote the recent line of research on self-powered sensor networks for smart bridge monitoring being performed at the Florida International University.
Composite is one of the most widely used industrial materials because of high strength, low weight, and high corrosion resistance properties. Different parts of composite structures are normally joined using adhesives or fasteners that are prone to defects and damages. A reliable method for prediction of the defect location is needed for an efficient structural health monitoring (SHM) process. Heterodyne effect is recently utilized for damage detection in the bonding zone of composite structures where debonding is expected to change the linear characteristics of the system into nonlinear characteristics. This paper briefly introduces this novel defect locating approach in composite plates using the heterodyne effect. For the first time, an Artificial Neural Network methodology is utilized with heterodyne effect method to find the defect location in composite plates. The main objective of this article is to develop a neural network based methodology for prediction of damage location, particularly for the bond inspection of composite plates.
In this paper, a new concept for damage detection and long- term health monitoring of structures is presented. The Precursor Transformation Method (PTM) is based on determining the causes (precursors) of change in the measured state of the structure under non-variable loading conditions (e.g. dead loads in bridges). The PTM concept addresses the inability of the current structural monitoring methods to discriminate, in structural behavior terms, the meaning of voluminous measured sensor data on a timely and cost effective basis. This method offers advantages in sensitivity and cost efficiency when compared to conventional vibration-based or parameter estimation methods. PTM was developed as part of a research project sponsored by the Federal Highway Administration on bridge stay cable condition assessment. Measured changes in the state of a structure (displacements, strains, internal forces) can be related to precursors through a transformation matrix. This matrix is formed by determining the patterns of change in the state of structure associated with externally imposed strains (temperatures) or displacements representing possible damage scenarios. A finite element model of the undamaged structure is used to calculate these patterns. The use of an undamaged model of the structure in determining damage patterns simplifies the calculation process significantly, while introducing some approximation in results. Theoretical derivations and special case studies indicate that these approximations are limited to second order effects, and in many cases well within measurement and calculation accuracies. Examples using simulated damages on two truss structures and a cable-stayed bridge are also presented.
In this paper, results of a research project sponsored by the Federal Highway Administration (FHWA) on a non-destructive method for measurement of stay cable forces in cable-stayed bridges are presented. This project included development and verification of specific analytical and experimental procedures for measurement of stay cable forces. In one set of procedures, a single laser vibrometer is used to measure low- level cable vibrations due to ambient (wind and traffic) excitation. The laser device allows rapid measurement of cable vibrations at distances of up to several hundred feet. Procedures are also developed for utilization of accelerometers attached to cables. Contact sensors are more appropriate when long-term remote monitoring is desired. Measured natural frequencies of vibration are related to cable tension through a mathematical formulation developed during the course of this study. This formulation includes the effects of cable sag-extensibility, bending stiffness, various boundary conditions, intermediate springs or dampers, etc. This method can also be used during construction in lieu of the 'lift off' method. The accuracy and effectiveness of this methodology was tested in the laboratory on a scaled model of a cable, and on two cable-stayed bridges. This ability to rapidly measure stay cable forces provides an opportunity for global condition assessment of these major structures.
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