Mohammed Zein Elshafie

Accuracy of Distributed Optical Fiber Temperature Sensing for Use in Leak Detection of Subsea Pipelines

AbstractAccurate and rapid detection of leaks is important for subsea oil pipelines to minimize environmental risks and operational/repair costs. Temperature-sensing optical fiber cables can provide economic, near real-time sensing of leaks in subsea oil pipeline networks. By employing optical time domain reflectometry and detecting the Brillouin scattered components from a laser source, the temperature gradients can be detected at any location along an optical fiber cable attached to the oil pipeline. The feasibility of such technology has been established in the literature along with a case study on a land-based pipeline. In this paper the accuracy of an optical fiber-based temperature sensing system is investigated. A mathematical model that simulates the process of temperature sensing is developed and the results are presented. An experimental investigation is carried out with two different laboratory setups to establish the spatial resolution and accuracy of the optical fiber cable detection system, ...

CFRP SHEAR STRENGTHENING OF REINFORCED CONCRETE T-BEAMS WITH CORRODED SHEAR LINKS

AbstractThis paper investigates the structural behavior of uncorroded as well as corroded RC T-beams strengthened in shear with either externally bonded (EB) carbon fiber–reinforced polymer (CFRP) sheets or embedded CFRP rods. Nine tests were carried out on RC T-beams having an effective depth of 295 mm and a shear span to effective depth ratio of 3.05. The investigated parameters are the shear link corrosion level (uncorroded, 7% corroded, or 12% corroded) and type of CFRP strengthening system (EB CFRP sheets or embedded CFRP rods). The unstrengthened beams with shear link corrosion levels of 7 and 12% had shear strengths that were 11 and 14%, respectively, less than the shear strength of the uncorroded unstrengthened beam. Both the embedded CFRP rods and EB CFRP sheets were effective in enhancing the shear strength of tested beams but the effectiveness of both strengthening systems decreased with increasing shear link corrosion level. The shear strength enhancement provided by the embedded CFRP rods and...

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))

Benefits of Global Standards on the Use of Optical Fiber Sensing Systems for the Impact of Construction of New Utilities and Tunnels on Existing Utilities

Distributed Optical Fiber Sensing is a mature technology given its strong record of over 20 years. Nevertheless, underground utilities are yet to embrace it as an everyday tool despite its enormous capability. One dimensional long buried utilities and tunnels offer the best application for the use of this technology. Research studies around the world offer the promise of this technology in monitoring the impact of ground movements on underground utilities and tunnels. No application standards existed that governed the use of this technology within any jurisdiction in the world in September 2012. A global task group on optical fiber sensing systems (OFSS) was born to become a unique pool of talent and experience on the subject with over 40 leading experts from 17 countries, which went on to author two companion standards American Society for Testing and Materials (ASTM) F3079-14 and F3092-14, within ASTM Technical Committee F36. This paper provides a brief overview of how OFSS work, what is in these standards, why OFSS is poised to become the most versatile innovation among all measurement tools for field monitoring, what problems the task group faced during the development of the standards and how the members of the task group resolved these problems, what the benefits are of such global standards and the future plans for the global OFSS task group. The most paramount goal of the authors is to share the lessons they learned during the development of the standards with the delegates of this conference.

Centrifuge Modeling of Deep Excavations and Their Interaction With Adjacent Buildings

Major cities in the world are experiencing a rapid growth in population while becoming increasingly overcrowded and congested. In recent years, this has created a huge demand for underground infrastructure, which often involves the design of major mass transit tunnel systems; these tunnel systems (underground tunnels and metro stations) are becoming increasingly necessary to construct in very close proximity to existing buildings. The prediction of excavation-induced deformations, therefore, becomes a key issue in the planning and design process for these schemes. However, current design approaches are conservative and often lead to unnecessary concern and expenditure in the design and provision of protective measures. A better understanding of the mechanisms involved in the excavation soil–structure interaction could reduce costs and help avoid potential problems. A series of small-scale model tests was carried out in the geotechnical centrifuge at Cambridge University to investigate the interaction between excavations and model buildings. Excavations (simulated by adopting a novel two-fluid technique) in a “free field” were also undertaken to assess the difference between free-field ground movements and those affected by a stiff model building. A detailed description of the centrifuge models and test procedures is presented in this paper, followed by the presentation of test results that demonstrate the effect of the stiffness of the model building on the excavation-induced displacements.

Fiber-Optic Underground Sensor Networks

Abstract The main motives driving the trend toward increased implementation of structural monitoring systems are the need for structural health monitoring of existing and ageing structures and the desire for a better understanding of increasingly complex designs through performance monitoring of new structures. This drive is sustained by rapid progress in research and technology development on sensors and communications. This chapter presents three case studies focusing on the monitoring of tunnels using distributed fiber-optic sensing. The first case study presents the results of strain development in the sprayed concrete lining (SCL) of a new Crossrail station tunnel during excavation of a cross-passage. The second case study focuses on the short term monitoring of a century old cast iron tunnel during the proximity construction of a large platform tunnel for the Crossrail project. The final case study describes the early stage implementation of a long-term structural health monitoring program to assess the integrity of tunnels at CERN. For all these projects Brillouin-based time domain techniques were used. A brief description of the basic principles of the method and the fiber-optic systems used is presented before the case studies. The variety of optical fibers available today combined with the number of fibre devices, with improved characteristics, recently developed provides a countless potential sensor configurations for environmental monitoring. In this chapter, a background of the use of fiber optic sensor networks in environmental applications are discussed focus in the optical detection for gas leakage sensing, water contamination sensing, soil contamination sensing and mapping with distributed fiber-optic sensors for environment.

Tunnelling close beneath an existing tunnel in clay – perpendicular undercrossing

A series of centrifuge model tests in clay was carried out to investigate the response of an existing tunnel at different clear distances to new tunnelling. A three-dimensional (3D) staged tunnelling model was adopted to simulate a wide range of tail void volume losses for the new tunnel construction while monitoring detailed 3D soil surface settlements and tunnelling-induced strains in the existing tunnel lining. This paper also presents a detailed case study of a similar scenario in the London Underground redevelopment of Bond Street station; various state-of-the-art instrumentation methods, including fibre optic Brillouin optical time domain reflectometry, instrumented tunnel bolts and photogrammetry, were deployed to monitor the response of the existing Royal Mail tunnel due to the new tunnelling works close beneath. The combination of field and centrifuge modelling data provides important new insights into the deformation mechanisms encountered in such complex tunnelling scenarios.

Real-time statistical modelling of data generated from self-sensing bridges

Instrumentation of infrastructure is changing the way engineers design, construct, monitor and maintain structures such as roads, bridges and underground structures. Data gathered from these instru...

Field observations of settlements during circular shaft excavation in London

Field observations of ground surface settlement during circular shaft construction in London

Development of an FBG-Sensed Miniature Pressure Transducer and Its Applications to Geotechnical Centrifuge Modelling

Because of the elevated gravity and dimensional constraints, miniaturized sensors are required to measure pore pressure within soil specimens in geotechnical centrifuge testing. Electrical sensors have been used for the purpose. The small dimensions and their mechanical configurations made the available electrical pore pressure sensors fragile. They can be easily damaged in specimen preparation and testing. The electrical sensors tend to have a nonlinear and non-repeatable behavior in negative pressure range. Taking advantage of the optical fiber Bragg grating (FBG), the authors developed an FBG based miniature pore pressure sensor. The FBG sensors are immune to moisture and electromagnetic interference. The readings are linear in both positive and negative pressure range. A specially made FBG readout unit capable of taking readings at 10 kHz was used to monitor the pore pressure within the soil specimen in dynamic centrifuge tests. The paper describes and design of the miniature FBG pore pressure transducer system and its applications in static and dynamic physical model tests at the Cambridge University and National Central University geotechnical centrifugal testing facilities.