Nondestructive evaluation of FRP composite bridge componenets using infrared thermography and digital tap tesing

Aging of civil infrastructures is one of the major problems faced by the engineering industry today, with the concrete structures cracking and the steel reinforcement corroding due to exposure to deicing chemicals, resulting in shorter service life. An alternative to the degrading infrastructures made of concrete and steel is the use of Fiber Reinforced Polymer (FRP) composites, which are noncorrosive. Use of FRP as structural components such as bridge decks and retrofitting jackets can solve the problem of aging with enhanced durability in future constructions. But, proper installation of newer material in structurally important infrastructure requires a reliable method of evaluation or testing. Nondestructive Testing (NDT) or Evaluation (NDE) is a method that can detect the anomalies in the FRP structures keeping the physical properties of the structure intact. Infrared Thermography (IRT) and Digital Tap Testing (DTT) are two extensively used NDT techniques for inspection of infrastructures, because of their portability and easy-to-handle features. This problem report discusses the advanced and conventional IRT and DTT methods to detect subsurface defects in FRP composite bridge components and FRP rehabilitated concrete bridge. Advanced IRT offers high-end infrared camera and robust digital image processing abilities to locate sub-surface defects in the structures, which, in some cases, conventional IRT fails to do. In addition, this report also includes IRT based tests using a low-cost halogen lamp heater, which is compared to the heating capability of VoyageIR Pro (advanced IRT equipment). Also, Digital Tap Hammer was used for rapid evaluation of the defects in the structural members, which provides a scientific alternative to the traditional coin tap method. The extent of applicability of DTT method compared to IRT was studied using several FRP specimens in the laboratory. DTT was limited to defects at lower depth, such as debonds in thin FRP wraps and could not detect delaminations in thick FRP members. The methods were also used in field testing of concrete box beams rehabilitated with carbon FRP fabrics. The field testing enabled the detection of debonds which helped in their immediate repair

Analysis of grease contamination influence on the internal radial clearance of ball bearings by thermographic inspection

One of the most important factors influencing ball bearings service life is its internal radial clearance. However, this parameter is also very complex because it depends on applied radial load and ball bearings dimensions, surface finish, and manufacturing materials. Thermal condition of ball bearings also significantly affects internal radial clearance. Despite many researches performed in order to find out relevant facts about different aspects of ball bearings thermal behaviour, only few of them are dealing with the real working conditions, where high concentration of solid contaminant particles is present. That is why the main goal of research presented in this paper was to establish statistically significant correlation between ball bearings temperatures, their working time, and concentration of contaminant particles in their grease. Because of especially difficult working conditions, the typical conveyor idlers bearings were selected as representative test samples and appropriate solid particles from open pit coal mines were used as artificial contaminants. Applied experimental methodology included thermographic inspection, as well as usage of custom designed test rig for ball bearings service life testing. Finally, by obtained experimental data processing in advanced software, statistically significant mathematical correlation between mentioned bearings characteristics was determined and applied in commonly used internal radial clearance equation. That is the most important contribution of performed research the new equation and methodology for ball bearings internal clearance determination which could be used for eventual improvement of existing bearings service life equations

The influence of material on the operational characteristics of spur gears manufactured by the 3D printing technology

The advanced development of additive technologies over the past years led to the fact that parts made by these technologies have been increasingly used in the most diverse engineering applications. One of the most famous and the most applied additive technology is 3D printing. In this paper the influence of the material type on the operational characteristics of spur gears manufactured by the 3D printing technology is analyzed, after the experimental testing performed on a back to back gear test rig, in the predefined laboratory conditions

The influence of material on the operational characteristics of spur gears manufactured by the 3D printing technology

The advanced development of additive technologies over the past years led to the fact that parts made by these technologies have been increasingly used in the most diverse engineering applications. One of the most famous and the most applied additive technology is 3D printing. In this paper the influence of the material type on the operational characteristics of spur gears manufactured by the 3D printing technology is analyzed, after the experimental testing performed on a back to back gear test rig, in the predefined laboratory conditions

Nondestructive evaluation of concrete bridge columns rehabilitiated with fiber reinforced polymers using digital tap hammer and infrared thermography

Nondestructive Evaluation of Concrete Bridge Columns Rehabilitated With Fiber Reinforced Polymers Using Digital Tap Hammer and Infrared Thermography Andrew Wheeler In 2017, the American Society of Civil Engineers (ASCE) gave bridges in the U.S. a C+ rating. Almost four out of every ten bridges are 50 years or older. In 2016, there were on average 188 million trips across a structural deficient bridge each day. With such a large number of bridges needing replaced or repaired, transportation officials are utilizing various bridge rehabilitation techniques to provide a cost effective solution to such a widespread problem. One rehabilitation technique involves the application of Fiber Reinforced Polymer (FRP) composite wraps to strengthen various bridge components. The initial and in-service, evaluation and acceptance of such FRP systems are crucial to their overall success and serviceability. Previously, several traditional methods such as visual inspection and coin tap testing of FRP composites were accepted as common practice for inspecting the quality of material and structural components. This type of evaluation was very subjective and dependent on the inspector\u27s level of experience. More recently, nondestructive testing (NDT) techniques can identify internal or external defects without affecting the form, or function of a structure. Digital Tap Hammer testing and Infrared Thermography (IRT) are two commonly used NDT techniques for field evaluation of civil infrastructure, because these techniques are user friendly and highly mobile. This problem report reviews the recent advances on the applications of digital tap hammer testing and infrared thermography at identifying defects in various elements of infrastructure and FRP composite wraps applied to bridge columns in southern West Virginia. Additionally, this report includes information on process of repairing dilapidated reinforced concrete columns in preparation for the installation of a FRP system. All of this will serve as a demonstration of how crucial non-destructive evaluation (NDE) is to the success of FRP bridge rehabilitation. Furthermore, the conclusions indicate a need for NDE to ensure quality control of field rehabilitation projects

Improved performance of a PV integrated ventilated façade at an existing nZEB

Producción CientíficaVentilated façades are among the existing measures to reduce the energy demand in buildings. The combination of this passive heating and cooling strategy with photovoltaics (PV) can drive new buildings towards the current European targets for near or even net zero-energy buildings (nZEB). The present work aims at studying the PV integrated ventilated façade of the nZEB known as “LUCIA” at the University of Valladolid, Spain. First, the transmissivity of the PV façade is measured. Then, the monitoring of the available solar radiation is presented together with the air-dry bulb temperatures indoors, outdoors and inside the ventilated façade. The experimental results permit the validation of a mathematical model that describes the behaviour of the ventilated façade in its current operating modes. The results show that dampers should be closed during winter to let the façade act as a further insulation for outdoor temperatures below 18.4 C to improve energy efficiency. Indoor air recirculation would be helpful during 10% of the winter period.Junta de Castilla y Leon - Fondo Europeo de Desarrollo Regional (project VA272P18)VIPSKILLS (project 2016-1-PL01-KA203-026152 Erasmus +

In-field assessment of batteries and PV modules in a large photovoltaic rural electrification programme

Assuring the sustainability of quality in photovoltaic rural electrification programmes involves enhancing the reliability of the components of solar home systems as well as the characterization of the overall programme cost structure. Batteries and photovoltaic modules have a great impact on both the reliability and the cost assessment, the battery being the weakest component of the solar home system and consequently the most expensive element of the programme. The photovoltaic module, despite being the most reliable component, has a significant impact cost-wise on the initial investment, even at current market prices. This paper focuses on the in-field testing of both batteries and photovoltaic modules working under real operating conditions within a sample of 41 solar home systems belonging to a large photovoltaic rural electrification programme with more than 13,000 installed photovoltaic systems. Different reliability parameters such as lifetime have been evaluated, taking into account different factors, for example energy consumption rates, or the manufacturing quality of batteries. A degradation model has been proposed relating both loss of capacity and time of operation. The user e solar home system binomial is also analysed in order to understand the meaning of battery lifetime in rural electrification

Experimental observations on hot-spots and derived

The hot-spot phenomenon is a relatively frequent problem occurring in current photovoltaic generators. It entails both a risk for the photovoltaic module’s lifetime and a decrease in its operational efficiency. Nevertheless, there is still a lack of widely accepted procedures for dealing with them in practice. This paper presents the IES–UPM observations on 200 affected photovoltaic modules. Visual and infrared inspection, as well as electroluminescence, peak power rating and operating voltage tests have been carried out. Thermography under steady state conditions and photovoltaic module operating voltage, both at normal photovoltaic system operating conditions, are the selected methods to deal in practice with hot-spots. The temperature difference between the hot-spot and its surroundings, and the operating voltage differences between affected and non-affected photovoltaic modules are the base for establishing defective criteria, at the lights of both lifetime and operating efficiency considerations. Hot-spots temperature gradients larger than 20 °C, in any case, and larger than 10 °C when, at the same time, voltage operating losses are larger than the allowable power losses fixed at the photovoltaic module warranties, are proposed as rejecting conditions for routine inspections under contractual frameworks. The upper threshold of 20 °C is deduced for temperate climates from the basic criterion of keeping absolute hot-spot temperatures below 20 °C

Nondestructive Evaluation of Historic Hakka Rammed Earth Structures

The in-service Hakka rammed earth buildings, in the Fujian Province of China, are unique in design and performance. Their UNESCO’s inscription as World Heritage sites recognizes their artistic, cultural, social and historic significance. Sponsored by the National Science Foundation of the United States, the authors have examined the engineering values of these buildings in terms of comfortable living at low energy consumption, sustainability and durability. The objective of this study was to better understand the thermo-mechanical and aging responses of Hakka earth buildings under thermal and earthquake loads through nondestructive field evaluation, including full-scale roof truss and floor testing, laboratory testing of field samples and finite element modeling. This paper presents our observations and findings from the field nondestructive evaluations with emphasis on the integrity of the rammed earth outer walls and inner wood structures, as well as the thermal comfort of living in these buildings, while a second paper presents the results from the material characterization of field samples and the structural responses of a representative building under earthquake induced loads through finite element analysis

Detection of Buried Non-Metallic (Plastic and FRP Composite) Pipes Using GPR and IRT

This research investigated alternative strategies for making buried non-metallic pipes (CFRP, GFRP, and PVC) easily locatable using Ground Penetrating Radar (GPR). Pipe diameters up to 12 and buried with up to 4 ft. of soil cover were investigated. The findings of this study will help address the detection problem of non-metallic pipelines and speed the adoption of composite pipes by the petroleum and natural gas industry. The research also investigated the possibility of locating buried pipes transporting hot fluids using Infrared Thermography (IRT). Results from the study have shown that, using carbon fabric and aluminum tape overlay on non‑metallic pipes (GFRP or PVC for this study) before burying significantly increases the reflected GPR signal amplitude, thereby making it easier to locate such pipelines using GPR. The reflected GPR signal amplitude for pipe sections with carbon fabric or aluminum foil overlays was found to have increased by a factor of up to 4.52 times, and 2.02 times on average across all the pipe sections tested, from the baseline (unwrapped) pipe sections. The research also highlights the importance of using the correct antenna frequency for detecting buried pipes in wet soil conditions. Wet soils with high electrical conductivity and dielectric constants have higher radar signal attenuations that significantly affect the penetration depth and returned signal amplitudes from buried objects. A 200 MHz frequency antenna was found in this study to be ideal for locating the buried pipes in all soil moisture conditions. The 200 MHz antenna was able to detect buried pipes up to the maximum 4 ft. depth of soil cover that was studied experimentally. Numerical estimation using the same soil from the experiment shows that this antenna can penetrate up to a depth of at least 5.5 ft. in very wet clay soils with volumetric water content of 0.473. After evaluating the attenuation characteristics of different radar antennae, it was found that material/ohmic attenuation is constant across a range of antenna frequencies; the increase in GPR signal attenuation associated with higher antenna frequencies was found to be a result of scattering attenuation from subsurface inhomogeneity/clutter. Scattering attenuation is however usually ignored in literature, resulting in erroneous estimation of radar signal attenuation. Finally, laboratory study proved that, heat from a buried pipeline transporting hot fluid can propagate through the soil to the surface and be detected using IRT. Additionally, a 6 diameter steam pipe with a 6 minimum insulation and buried with 2.5 – 3 ft. of soil cover was easily detected in varying soil moisture conditions during different seasons throughout the year using IRT in the field environment. The successful application of IRT in detecting this pipe proves the potential for using this technique in locating buried pipes transporting hot fluids such as steam or petroleum products from production wells or refinery plants