Long-Term Performance Evaluation Of NUdeck In Kearney East Bypass

The Kearney East Bypass bridge is the first project that implements the newly developed precast concrete deck system (known as 2nd generation NUDECK). The new system consists of full-depth full-width precast prestressed concrete deck panels that are 12 ft (3.66 m) long each. The panels have covered shear pockets at 4 ft (1.22 m) spacing on each girder line to host clustered shear connectors that are adjustable in height. Narrow unreinforced transverse joints are used to eliminate the need for deck overlay. Also, deck panels are post-tensioned in the longitudinal direction using a new post-tensioning system that eliminates the need for post- tensioning ducts, strand threading, and grouting operations. The project has twin bridges: a southbound bridge with cast-in-place (CIP) concrete deck, and northbound bridge with the new precast concrete (PC) deck system. The two bridges were completed in the fall of 2015 and opened to traffic in the fall of 2016. Due to the unique features of the new PC deck system, this research project was initiated to monitor short-term performance using live load test and long-term performance under traffic loads to evaluate the system performance. Both CIP concrete deck and PC deck bridges were instrumented and tested during the summer of 2016 to compare the performance of their superstructures. Also, finite element analysis (FEA) was conducted to predict the performance of the new PC deck system. The results of both analytical and experimental investigations indicated that the PC deck system performs as predicted and very comparable to the conventional CIP concrete deck

Infrared Thermography for Weld Inspection: Feasibility and Application

Traditional ultrasonic testing (UT) techniques have been widely used to detect surface and sub-surface defects of welds. UT inspection is a contact method which burdens the manufacturer by storing hot specimens for inspection when the material is cool. Additionally, UT is only valid for 5 mm specimens or thicker and requires a highly skilled operator to perform the inspections and interpret the signals. Infrared thermography (IRT) has the potential to be implemented for weld inspections due to its non-contact nature. In this study, the feasibility of using IRT to overcome the limitations of UT inspection is investigated to detect inclusion, porosity, cracking, and lack of fusion in 38 weld specimens with thicknesses of 3, 8 and 13 mm. UT inspection was also performed to locate regions containing defects in the 8 mm and 13 mm specimens. Results showed that regions diagnosed with defects by the UT inspection lost heat faster than the sound weld. The IRT method was applied to six 3 mm specimens to detect their defects and successfully detected lack of fusion in one of them. All specimens were cut at the locations indicated by UT and IRT methods which proved the presence of a defect in 86% of the specimens. Despite the agreement with the UT inspection, the proposed IRT method had limited success in locating the defects in the 8 mm specimens. To fully implement in-line IRT-based weld inspections more investigations are required

Benchmarking Image Processing Algorithms for Unmanned Aerial System-Assisted Crack Detection in Concrete Structures

This paper summarizes the results of traditional image processing algorithms for detection of defects in concrete using images taken by Unmanned Aerial Systems (UASs). Such algorithms are useful for improving the accuracy of crack detection during autonomous inspection of bridges and other structures, and they have yet to be compared and evaluated on a dataset of concrete images taken by UAS. The authors created a generic image processing algorithm for crack detection, which included the major steps of filter design, edge detection, image enhancement, and segmentation, designed to uniformly compare dierent edge detectors. Edge detection was carried out by six filters in the spatial (Roberts, Prewitt, Sobel, and Laplacian of Gaussian) and frequency (Butterworth and Gaussian) domains. These algorithms were applied to fifty images each of defected and sound concrete. Performances of the six filters were compared in terms of accuracy, precision, minimum detectable crack width, computational time, and noise-to-signal ratio. In general, frequency domain techniques were slower than spatial domain methods because of the computational intensity of the Fourier and inverse Fourier transformations used to move between spatial and frequency domains. Frequency domain methods also produced noisier images than spatial domain methods. Crack detection in the spatial domain using the Laplacian of Gaussian filter proved to be the fastest, most accurate, and most precise method, and it resulted in the finest detectable crack width. The Laplacian of Gaussian filter in spatial domain is recommended for future applications of real-time crack detection using UAS

Long-Term Performance Evaluation Of NUdeck In Kearney East Bypass

The Kearney East Bypass bridge is the first project that implements the newly developed precast concrete deck system (known as 2nd generation NUDECK). The new system consists of full-depth full-width precast prestressed concrete deck panels that are 12 ft (3.66 m) long each. The panels have covered shear pockets at 4 ft (1.22 m) spacing on each girder line to host clustered shear connectors that are adjustable in height. Narrow unreinforced transverse joints are used to eliminate the need for deck overlay. Also, deck panels are post-tensioned in the longitudinal direction using a new post-tensioning system that eliminates the need for post- tensioning ducts, strand threading, and grouting operations. The project has twin bridges: a southbound bridge with cast-in-place (CIP) concrete deck, and northbound bridge with the new precast concrete (PC) deck system. The two bridges were completed in the fall of 2015 and opened to traffic in the fall of 2016. Due to the unique features of the new PC deck system, this research project was initiated to monitor short-term performance using live load test and long-term performance under traffic loads to evaluate the system performance. Both CIP concrete deck and PC deck bridges were instrumented and tested during the summer of 2016 to compare the performance of their superstructures. Also, finite element analysis (FEA) was conducted to predict the performance of the new PC deck system. The results of both analytical and experimental investigations indicated that the PC deck system performs as predicted and very comparable to the conventional CIP concrete deck

Bridge Inspection: Human Performance, Unmanned Aerial Systems and Automation

Unmanned aerial systems (UASs) have become of considerable private and commercial interest for a variety of jobs and entertainment in the past 10 years. This paper is a literature review of the state of practice for the United States bridge inspection programs and outlines how automated and unmanned bridge inspections can be made suitable for present and future needs. At its best, current technology limits UAS use to an assistive tool for the inspector to perform a bridge inspection faster, safer, and without traffic closure. The major challenges for UASs are satisfying restrictive Federal Aviation Administration regulations, control issues in a GPS-denied environment, pilot expenses and availability, time and cost allocated to tuning, maintenance, post-processing time, and acceptance of the collected data by bridge owners. Using UASs with self-navigation abilities and improving image-processing algorithms to provide results near real-time could revolutionize the bridge inspection industry by providing accurate, multi-use, autonomous three-dimensional models and damage identification

Thermal Bowing Testing of Precast Concrete Sandwich Wall Panels

Thermal bowing is out-of-plane wall deflection, which is a common issue on sandwich panel walls caused by a temperature differential between a building interior temperature and the environmental conditions. This report aims to better understand thermal load response of concrete sandwich wall panels. Full-scale testing was performed to verify the assumptions regarding thermal gradient, temperature variation at the cross-section level and thermal conductivity of the connectors. It was found out that carbon fiber reinforced polymer nor glass fiber reinforced polymer connectors transfer a significate amount of heat from one wythe to the other, hence, the temperature in one wythe remained constant while the other was heated. Thermal bowing was measured, and it was found that following a rapid increase in temperature the out-of-plane deflection resulted in a relatively linear relationship between the temperature gradient and bowing

Tilt-Up Partially Composite Insulated Wall Panels

This research project was initiated to investigate the behavior of load-bearing concrete insulated wall panels for use in tilt-up construction. The primary objective was to understand the inelastic behavior of these panels so that engineers could perform a proper second-order analysis for combined axial and out-of-plane loading. Toward this aim, the Tilt-up Concrete Institute (TCA) and wythe connector suppliers Innstruct, Thermomass, HK Composites, Dayton Superior, and IconX, funded this study. This report contains information related to testing of solid and partially composite insulated wall panels that integrated proprietary wythe connection systems. Using the information from these tests, a method to predict out-of-plane moments and deflection suitable for second-order slender wall analysis was proposed for insulated walls. Additionally, the shear flow approach, was found to be inaccurate and a new method for predicting horizontal shear failure was introduced. The new methods are demonstrated and compared to testing data and found to be accurate and conservative. Since tilt-up panel testing of similar scope had not been done since the 1980s on panels of lower height, there were several goals for this testing. This represented an opportunity to validate the current ACI code alternate slender wall analysis method and provide a set of control panels for testing solid tilt-up panel behavior. Testing solid panels and CIPs of 40 ft span, a length typical of contemporary construction, was critical so that such slenderness ratios could be observed and significant second-order panel behavior could be identified. As part of this, the research team created a modified version of the slender wall design method to predict second-order load and deflection behavior in the post-cracking range in CIPs. For solid panels, the 1980s testing program popularized the “slender wall design method” outlined in ACI 551 and the goal of this newer methodologies is to do the same for CIPs. Additionally, horizontal shear failure analysis methods were investigated to enable design against such failures. Solid panel deflections and strength were as expected and matched very well the tilt-up Slender Wall Design method. Furthermore, cracking stresses were observed close to the (2/3)fr stipulated by the Slender Wall Method. For the CIPs, the two primary failure modes were observed: flexural reinforcement yielding and horizontal shear failure. The Group A panels performed very similarly to solid walls, even matching closely an unmodified version of the Slender Wall Design Method. This behavior was likely due to the reduced and solid regions noted in the Group A panels that would be similar to their in-service construction. The Group B, C, D, and E panels all experienced both flexural and shear failures in different specimens and required the use of a separate set of analysis methods that would also be applicable to Group A panels. The following describes the methods recommended for all panel types tested herein. Using the unique experimental information herein, The Shear Flow method and a new method termed The Shear Slip Method were evaluated to estimate horizontal shear failure. The Shear Flow method, when used properly, results in perhaps an overlyconservative prediction of horizontal shear strength but did not match the observed data well. The Shear Slip Method relies on an assumption of the failure slip mechanism (as observed from these and other experiments) and the double shear data to determine a maximum horizontal shear strength while incorporating the ductility of the connectors. This method was found to predict horizontal shear failure both accurately and conservatively. A Modified Slender Wall Method was developed that estimates the contribution of connector slip to the shear deformations in a straightforward way. When using this method to predict the deformations at failure for panels that experienced flexural failure it produced accurate and conservative results. For panels that are controlled by horizontal shear failure, this method can be overly conservative for flexural deformations because it is intentionally simplified. Another method termed the K123 method was demonstrated that can better predict panel deflections and horizontal shear failures using matrix analysis or other methods. This method is not recommended without further validation but does demonstrate panel load and deformation behavior well. 399 page

Review of the Utah Snow Load Study

Proper consideration of snow loads in building design can be a delicate balancing act: Underestimates lead to structure failure Overestimates lead to increased construction cost

Automatic Surface Crack Detection in Concrete Structures Using OTSU Thresholding and Morphological Operations

Concrete cracking is a ubiquitous phenomenon, present in all types of concrete structures. Identifying and tracking the amount and severity of cracking is paramount to evaluating the current condition and predicting the future service life of a concrete asset. Concrete cracks can indicate reinforcement corrosion, the development of spalls or changing support conditions. Therefore, monitoring cracks during the life span of concrete structures has been an effective technique to evaluate the level of safety and preparing plans for future appropriate rehabilitation. One growing technique are unmanned inspections using Unmanned Aerial Vehicles (UAV). UAVs are drones equipped with cameras, sensors, GPS, etc. RGB images (color images in Red, Green and Blue color space) are obtained from a camera mounted on a UAV flying around the structure, to detect cracks and other defects. Each image captured by UAV needs to be evaluated to track the crack formations. To save time, this task can be done by applying image processing techniques to automatically detect and report cracks rather than using a human to identify them. In addition, processing RGB images with sufficient information, such as the distance of camera to surface for each picture, will provide the dimension of the cracks (length and width). The report consists of the following sections: A literature review of image processing techniques used in structural health monitoring and other fields of interest is provided in chapter 2. The Proposed method to identify cracks is demonstrated in Chapter 3. Experimental results, conclusion and future work are presented in Chapter 4. Appendix A includes the processed images using the proposed method and Appendix B includes the comparison between Talab’s method and the proposed method. In Appendix C, a “readme” file is given to run the program, and finally Appendix D shows the Matlab Code

Infrared Thermography for Weld Inspection: Feasibility and Application

Traditional ultrasonic testing (UT) techniques have been widely used to detect surface and sub-surface defects of welds. UT inspection is a contact method which burdens the manufacturer by storing hot specimens for inspection when the material is cool. Additionally, UT is only valid for 5 mm specimens or thicker and requires a highly skilled operator to perform the inspections and interpret the signals. Infrared thermography (IRT) has the potential to be implemented for weld inspections due to its non-contact nature. In this study, the feasibility of using IRT to overcome the limitations of UT inspection is investigated to detect inclusion, porosity, cracking, and lack of fusion in 38 weld specimens with thicknesses of 3, 8 and 13 mm. UT inspection was also performed to locate regions containing defects in the 8 mm and 13 mm specimens. Results showed that regions diagnosed with defects by the UT inspection lost heat faster than the sound weld. The IRT method was applied to six 3 mm specimens to detect their defects and successfully detected lack of fusion in one of them. All specimens were cut at the locations indicated by UT and IRT methods which proved the presence of a defect in 86% of the specimens. Despite the agreement with the UT inspection, the proposed IRT method had limited success in locating the defects in the 8 mm specimens. To fully implement in-line IRT-based weld inspections more investigations are required