Fernando Moreu

Dynamic Assessment of Timber Railroad Bridges Using Displacements

Abstract Infrastructure spending is such a large component of a railroad budget that it must be prioritized to meet the concurrent safety and line capacity requirements. Current bridge inspection and rating practices recommend observing bridge movements under a live load to help assess bridge conditions. However, measuring bridge movements under trains in the field is a challenging task. Even when they are measured, the relationships between bridge displacements and different loads/speeds are generally unknown. The research reported herein shows the effects of known train loadings, speeds, and traffic directions on the magnitude and frequency of displacements as measured on timber pile bents of a Class I railroad bridge. Researchers collected both vertical and transverse (lateral) displacements under revenue service traffic and work trains using LVDTs with a sampling frequency of 100 Hz. To investigate the effect of traffic on timber railroad bridges, displacements were measured under crossing events at d...

Reference-Free Displacements for Condition Assessment of Timber Railroad Bridges

Current railroad bridge inspection and rating practices include observing bridge movement under live loads to help assess bridge conditions. Recent research has shown that transverse displacements of timber trestle bridges can capture critical changes in bridge serviceability (the ability to safely carry out railroad operations) as a function of railroad loading, speed, and direction. Measuring bridge movement under trains in the field is difficult and expensive because a fixed reference point is not normally available, thus creating the need to erect independent scaffolding to create good reference points near a timber bridge. This research demonstrates the potential of using reference-free accelerations collected with wireless smart sensors to estimate railroad bridge transverse displacements under live train loads. Focus is placed on timber trestle bridges, which comprise approximately 24% of the total inventory length of railroad bridges in the United States. The results show that wireless smart sensors can estimate transverse displacements of timber railroad trestles and could become an effective tool for campaign monitoring of railroad bridges (with applications toward helping overall bridge assessment).

Consequence-based management of railroad bridge networks

Abstract To increase profitability, add capacity and comply with new federal regulations on bridge safety, North American railroads are exploring means to improve the management of their bridge networks. Current maintenance, repair and replacement (MRR) decisions are informed by bridge inspections and ratings, which recommend observing the response of bridges under trains. However, an objective relationship between bridge responses and the associated impact to railroad operations has yet to be established. If the consequences of MRR decisions could be better determined, then the railroads could more effectively allocate their limited resources. Chief bridge engineers from different Class I railroads provided the values of displacements and assessment used to develop this paper. Researchers monitored displacements from over 50 train crossing events and related them to decisions on operations and maintenance. This paper develops an approach for consequence-based management of bridge networks for making network MRR decisions, employing fragility curves to relate service condition limit states to transverse displacement. The operational costs associated with these service conditions can estimate the total costs of a given MRR policy. In this way, optimum MRR decisions can minimise the total network costs. This framework provides a consistent approach for the prioritisation of railroad bridge MRR decisions.

Structural Health Monitoring of Railroad Bridges - Research Needs and Preliminary Results

The initial content of this paper presents results of a survey-based study that identified simplified displacement monitoring of railroad bridges under trains as the main research interest of railroad bridge structural engineers. The second part of this publication describes a railroad bridge classification towards structural health monitoring (SHM) applications, based on current structural engineering problems and challenges identified by the railroad industry for each railroad bridge type. Finally, this paper briefly describes ongoing research related to attempting to monitor railroad bridge deflections by means of using simplified wireless sensors, and preliminary field experimentation and proof of concept validations.

Use of wireless sensors for timber trestle railroad bridges health monitoring assessment

This presentation discusses the possibilities associated between the existing available applied research in wireless sensors and the always increasing need to identify/address existing railroad bridges performance under actual traffic. In one hand, universities and research centers today are developing the advance theory and framework for the use of wireless sensors in structures health monitoring .To implement wireless sensors in the areas where quantitative / objective data is required. Timber trestle bridges are carrying most of the main line traffic in the US, especially in the South Regions, and a significant number of those are in need of maintenance and or replacement. The maintenance and/or replacement of timber bridges is based on visual/direct and individual inspections, which can not assess objective/quantitative data of the bridge performance under loading. Different bridge inspectors will not be able to determine objective parameters for different bridges, and even more, different loading conditions. The dynamic response of the timber trestle bridge continues to be an isolated parameter that can not be compared with the existing maintenance/inspection program. The authors gathered data obtained by connecting wireless sensors to existing timber trestle bridges which were identified to show excessive longitudinal and transversal displacement under regular traffic loading. The paper includes the description on the implementation process of wireless sensors under real on-site conditions, critique to the results and their validity, and proposed improvements in the entire data acquisition, comprised in concrete proposals. It finally summarizes recommendations for future/potential use in the railroad timber trestle railroad bridge maintenance, inspection and assessment.

Reference-free dynamic displacements of railroad bridges using low-cost sensors

Displacements of railroad bridges under service loads are important parameters in assessing bridge conditions and risk of train derailment, according to railroad bridge managers. Measuring bridge responses in the field is often expensive and challenging due to the high costs of sensing equipment. Consequently, railroad bridge managers typically rent or subcontract field measurements to others or choose not to collect dynamic data in the field and make visual inspections. This article studies the use of a low-cost data acquisition platform to measure reference-free dynamic displacements of railroad bridges by combining low-cost microcontrollers and accelerometers. Researchers used off-the-shelf systems to measure accelerations and reconstructed reference-free displacements from several railroad bridge crossing events by running trains with different levels of serviceability in the laboratory. The results obtained from the proposed low-cost sensors were compared with those of commercial sensing equipment. The results show that low-cost sensors and commercial sensing systems have comparable accuracy. The results of this study show that the proposed platform estimates reference-free displacements with a peak error between 20% and 30% and a root mean square error between 10% and 20%, which is similar to commercial structural health monitoring systems. The proposed low-cost system is approximately 300 times less expensive than the commercial sensing equipment. The ultimate goal of this research is to increase the intelligent assessment of bridges by training owners and inspectors to collect dynamic data of their interest with their own resources.

Building US Railroad Bridges within Hours a.k.a. “Railroad Bridge Change-outs”

This paper describes the replacement and upgrading of railroad bridges in the United States (US), through specific “change-outs” case examples, identifying the different factors which make them the keystone of railroad bridge maintenance, repair and replacement nowadays. It also covers advancements in the railroad industry related to railroad bridge upgrades which minimize railroad traffic interruptions. Finally, it identifies potential areas of development and expansion from these lessons learned on railroad engineering which might be useful for other structural engineers involved with infrastructure design, construction and maintenance.

Direct Reference-Free Dynamic Deflection Measurement of Railroad Bridge under Service Load

Today, railroads carry 40% of the US freight tonnage and this demand will double in 20 years. North American railroad infrastructure includes approximately 100,000 bridges spanning over 140,000 miles of tracks. Half of those bridges are over 100 years old. Measuring deflection time history of railroad bridges under train load can assist in quantifying the reliability and increasing the safety of railroad operations throughout the network. However, obtaining bridge deflection is often difficult to collect in the field due to the lack of fixed reference points from where to measure. Although reference-free acceleration can be used to estimate the dynamic deflection through double integration, the algorithms are difficult to develop and apply because of the complicated integration constants selected for the data post-processing. This research studies the reference-free dynamic deflection (vertical displacement) acquisition approaches, a sensing system composed of one passive-servo electro-magnetic-induction (PSEMI) velocity sensor and one built-in hardware integrator unit. This research has presented two promising reference-free dynamic deflection acquisition approaches, direct reference-free displacement measurement from a sensing system composed of one passive-servo electro-magnetic-induction (PSEMI) velocity sensor and one built-in hardware integrator unit, and a reference-free displacement estimation from accelerometer by Lee-Method, that can be used for evaluating the performance and safety of railroad bridges under service load. Using the passive-servo feedback electrical control technology, the PSEMI velocity sensor provides a low-frequency direct reference-free measurement performance with its small size and light weight. Using a finite impulse response (FIR) filtering instead of double integrating, the displacement can be estimated from acceleration without the integration errors from unknown integration constants and boundary conditions. Researchers used an ASCE steel truss bridge model and an MTS actuator to quantify the accuracy of the PSEMI sensing system. The actuator replicated various harmonic motions and real bridge vertical displacements under train-crossing events measured in the field. The direct dynamic reference-free displacements measured by PSEMI sensing system and the indirect dynamic reference-free displacements estimated by acceleration using Lee-Method were compared to reference displacements measured by LVDT. The experimental results show that the direct reference-free dynamic displacement sensing system and indirect reference-free displacement estimation method from acceleration are two promising alternatives to railroad bridge deflection under train loading, without the need to a fixed reference frame.

Real-Time Low-Cost Wireless Reference-Free Displacement Sensing of Railroad Bridges

The U.S. freight rail network moves about 40 tons of freight per person over 225,000 km (140,000 miles) of rail track every year. The railroad infrastructure contains more than 100,000 bridges, which correspond to one bridge for every 2.25 km (1.4 miles) of track. Railroad resources and funds are limited. Consequently, railroads’ maintenance, repair, and replacement (MRR) decisions should be optimized. An objective prioritization of MRR decisions requires quantitative data that informs the structural integrity. Lateral displacement measurement of bridges is an objective and quantitative performance indicator. Traditional wired displacement measurement systems are costly, labor-intensive, and are difficult to apply on bridges due to the need of stationary reference points. This paper proposes an Arduino-based low-cost wireless sensing system to estimate bridge displacements from acceleration data. The system uses a low-cost MMA8451 accelerometer and implements a FIR-filter to convert the measurements to displacement. The data is transmitted to the base station using a XBee Series 1 module in real-time. Each sensor platform is estimated to cost about

Technical Specifications of Structural Health Monitoring for Highway Bridges: New Chinese Structural Health Monitoring Code

75. To evaluate the feasibility of the proposed system, a set of laboratory experiments are conducted by placing the sensor platform on a shake table and simulating bridge displacements measured on the field during train crossing events. The proposed measurement system can have impact on many applications that need real-time displacement information including, but not limited to aerospace engineering, mechanical engineering, and wind engineering.