Cr Middleton

Smart bridges, smart tunnels: Transforming wireless sensor networks from research prototypes into robust engineering infrastructure

We instrumented large civil engineering infrastructure items, such as bridges and tunnels, with sensors that monitor their operational performance and deterioration. In so doing we discovered that commercial offerings of wireless sensor networks (WSNs) are still geared towards research prototypes and are currently not yet mature for deployment in practical scenarios. We distill the experience gained during this 3-year interdisciplinary project into specific advice for researchers and developers. We discuss problems and solutions in a variety of areas including sensor hardware, radio propagation, node deployment, system security and data visualization. We also point out the problems that are still open and that the community needs to address to enable widespread adoption of WSNs outside the research lab.

Long-Term Wireless Structural Health Monitoring of the Ferriby Road Bridge

As part of an effective bridge management system, sensor networks can provide data to support both inspection and assessment. Wireless sensor networks (WSNs) have the potential to offer significant advantages over traditional wired monitoring systems in terms of sensor, cabling, and installation costs as well as expandability. However, there are drawbacks with WSNs relating to power, data bandwidth, and robustness. To evaluate the potential of WSNs for use in bridge management, a network of seven sensor nodes was installed on the Ferriby Road Bridge, a three-span reinforced concrete bridge. Three displacement transducer nodes were placed across cracks on the soffit of the bridge to measure the change in crack width. Three inclinometer sensor nodes were mounted on two of the elastomeric bearing pads to measure the change in inclination of the bearing pads while a final node monitored temperature in the box that contained the gateway. The installation of the WSN is discussed and data from this network is analyzed. Finally, the use of sensor networks to support inspection and assessment is discussed.

Categories of SHM Deployments: Technologies and Capabilities

AbstractThe findings of an extensive literature survey focusing on bridge structural health monitoring (SHM) deployments are presented. Conventional, maturing, and emerging technologies are reviewed as well as deployment considerations for new SHM endeavors. The lack of published calibration studies (and quantification of uncertainty studies) for new sensors is highlighted as a major concern and area for future research. There are currently very few examples of SHM systems that have clearly provided significant value to the owners of monitored structures. The results of the literature survey are used to propose a categorization system to better assess the potential outcomes of bridge SHM deployments. It is shown that SHM studies can be categorized as one (or a combination) of the following: (1) anomaly detection, (2) sensor deployment studies, (3) model validation, (4) threshold check, and (5) damage detection. The new framework aids engineers specifying monitoring systems to determine what should be meas...

FORM for discontinuous and truncated probability density functions

The common iterative FORM algorithm deals with random variables having continuous and smooth probability density functions. In some cases when the algorithm is applied to problems with discontinuous probability density functions difficulties may occur with convergence. For truncated density functions the routine may breakdown completely. Some examples illustrating these potential problems are given and the reasons described. Modifications to the standard iterative FORM algorithm are proposed.

Analysis of Structural Health Monitoring Data from Hammersmith Flyover

AbstractThere has recently been considerable research published on the applicability of monitoring systems for improving civil infrastructure management decisions. Less research has been published on the challenges in interpreting the collected data to provide useful information for engineering decision makers. This paper describes some installed monitoring systems on the Hammersmith Flyover, a major bridge located in central London (United Kingdom). The original goals of the deployments were to evaluate the performance of systems for monitoring prestressing tendon wire breaks and to assess the performance of the bearings supporting the bridge piers because visual inspections had indicated evidence of deterioration in both. This paper aims to show that value can be derived from detailed analysis of measurements from a number of different sensors, including acoustic emission monitors, strain, temperature and displacement gauges. Two structural monitoring systems are described, a wired system installed by a...

Management of structural monitoring data of bridges using BIM

Engineering and Physical Sciences Research Council, Innovate UK (CSIC Innovation and Knowledge Centre (Grant ID: EP/L010917/1))

A vibration powered wireless mote on the Forth Road Bridge

The conventional resonant-approaches to scavenge kinetic energy are typically confined to narrow and single-band frequencies. The vibration energy harvester device reported here combines both direct resonance and parametric resonance in order to enhance the power responsiveness towards more efficient harnessing of real-world ambient vibration. A packaged electromagnetic harvester designed to operate in both of these resonant regimes was tested in situ on the Forth Road Bridge. In the field-site, the harvester, with an operational volume of ~126 cm3, was capable of recovering in excess of 1 mW average raw AC power from the traffic-induced vibrations in the lateral bracing structures underneath the bridge deck. The harvester was integrated off-board with a power conditioning circuit and a wireless mote. Duty- cycled wireless transmissions from the vibration-powered mote was successfully sustained by the recovered ambient energy. This limited duration field test provides the initial validation for realising vibration-powered wireless structural health monitoring systems in real world infrastructure, where the vibration profile is both broadband and intermittent.

Innovative Bridge Design Handbook

Structural health monitoring (SHM) has the potential to transform the bridge engineering industry by providing stakeholders with additional information to inform decisions about the design, operation, and management of bridges throughout the structures’ lifespans. This chapter gives guidance on SHM for engineers who design, build, operate, and maintain bridges. There remain numerous technical challenges to overcome when deploying SHM systems; however the most important issues to consider are how to decide what information is required, and then how to develop a strategy to deliver this information in a form that is easy to interpret and can inform decision making. This chapter gives an introduction to the uses and current capabilities of SHM. Directions for future research and management of bridge SHM systems are also discussed.

STRENGTH AND BEHAVIOR IN SHEAR OF CONCRETE BEAM-AND-SLAB BRIDGES

Shear tests on four concrete beam-and-slab bridge specimens are reported. Quantities of longitudinal steel and shear stirrups were varied in an attempt to determine the strength and behavior in shear. These tests show that significant enhancement in shear strength of the beams is provided by the surrounding concrete slab. In addition, critical shear collapse mechanisms are described. These failure patterns have been used as the basis for an upper-bound plasticity approach to the problem of shear assessment of concrete beam-and-slab bridges.

Robust fibre optic sensor arrays for monitoring early-age performance of mass-produced concrete sleepers

This study investigates integrating fibre optic sensing technology into the production process of concrete railway sleepers. Robust fibre Bragg grating strain and temperature sensor arrays were developed specifically for this application and were designed for long-term monitoring of sleeper performance. The sensors were used to monitor sleeper production and to help gain a deeper understanding of their early-age behaviour which can highly influence long-term performance. In total, 12 sleepers were instrumented and strain data were collected during the entire manufacturing process including concrete casting and curing, prestressing strand detensioning and qualification testing. Following the production process, sleepers were stored temporarily and monitored for 4 months until being placed in service. The monitoring results highlight the intrinsic variability in strain development among identical sleepers, despite high levels of production quality control. Using prestress loss as a quality control indicator, the integrated sensing system demonstrated that sleepers were performing within Eurocode-based design limits prior to being placed in service. A three-dimensional nonlinear finite element model was developed to provide additional insight into the sleepers’ early-age behaviour. Based on the fibre Bragg grating–calibrated finite element model, more realistic estimates for the creep coefficient were provided and found to be 48% of the Eurocode-predicted values.