Unknown Bridge Foundations Research Articles

ERT Feasibility Study to Assess Unknown Bridge Foundation Depth

ERT Feasibility Study to Assess Unknown Bridge Foundation Depth

Performance of Impulse Response Testing on Prismatic Members with Intermediate Joints

Nondestructive Testing (NDT) methods have extensively been used to assess the conditions of civil infrastructure in the recent decades. Among various NDT techniques, Impulse Response (IR) has a vast application due to its simplicity and low cost. However, factors such as reflections from changes in impedance along the investigated members can adversely influence the success of the method. Numerous numerical and experimental studies have already been performed to evaluate the effect of change in mechanical impedances such as bulging, necking and similar anomalies. In this study, the effect of the presence of joints connecting the investigated members to other members, as another source of impedance change, is demonstrated. A three-story steel-concrete composite column of a building was selected for testing and IR tests were conducted. The obtained mobility graphs were clear, and the height of the column was easily measured with an acceptable error. The results of this study show that although the joints located between the top and bottom of the tested member are sources of change in mechanical impedance, they do not result in concealing the resonant frequencies from the wave reflected from the bottom of the member. Thus, IR method seems to be applicable in determining the length of prismatic members with intermediate joints such as piles of unknown bridge foundations with bracing and columns of buried buildings.

Limitations of Sonic Echo Testing on Buried Piles of Unknown Bridge Foundations

ABSTRACT Nondestructive Sonic Echo (SE) field tests have shown that this method does not have a satisfactory performance in determining the depth of piles fully buried underneath pile caps. In the current study, we endeavored to investigate the possibility of improving SE methodology to obtain interpretable results leading to determining the depth of buried piles in such foundations. The results obtained from the investigated numerical models indicated that the location of the pile toe could be determined when the height of the pile cap is less than 1 m. However, this value is questionable since it has been concluded in the absence of surrounding soil damping. In real bridge foundations with surrounding soils, the SE method may only be able to detect the length of a pile located beneath a cap with a height significantly smaller than 1 m. In summary, our simplified models show that the SE test is not a proper method to determine the length of fully buried piles supporting caps due to the limitations and difficulties discussed in the article.

Effect of Source Application on Sonic Echo/Impulse Response Tests Applied to Steel H-Piles

AbstractThe sonic echo/impulse response (SE/IR) method is a versatile nondestructive method for evaluating the conditions of unknown bridge foundations. Previous studies have shown that the method ...

Study of the Effect of Source Application on Sonic Echo Tests in Timber Piles

The long-term effects of scour have been identified as one of the primary reasons for bridge failure. To evaluate the performance of the bridges against scour, it is essential to assess the conditions of the bridge foundation including the depth of the piles. Sonic Echo (SE) has been a favorable nondestructive method to evaluate the condition of unknown bridge foundations in the recent decades. Previous studies have shown that the results obtained from SE tests can be affected by a variety of factors such as the pile-to-soil stiffness ratio, length-to-diameter ratio of the pile, presence of defects and anomalies near the pile head, striking method, and hammer type. Although previous studies have discussed such affecting factors, there is a lack of comprehensive investigation regarding the effect of striking method and hammer tip type specific to wood piles supporting bridge decks. In the current study, the effect of striking method and hammer type on the success of SE tests conducted on wood piles has been scrutinized by investigating various options of striking methods and hammer tip types. After comparing different options, superior ones were identified and recommendations for better conducting the SE tests on unknown wood bridge foundations were presented. Numerical simulations were also performed to support some of the conclusions.

Accuracy of Parallel Seismic Test Performance on Steel H-Piles in Layered Soils

AbstractParallel Seismic (PS) method is a straightforward Nondestructive Testing (NDT) method capable of providing valuable information of unknown bridge foundations made of various common construc...

Exploratory Study of Nondestructive Parallel Seismic Testing Challenges in Estimating the Depth of Unknown Wood Bridge Foundations

AbstractNondestructive methods have been extensively used to characterize unknown bridge foundations. Among various nondestructive methods, conventional and reverse parallel seismic (PS) methods ar...

Performance of Nondestructive Sonic Echo Testing Method on Partially Dismantled Unknown Wood Bridge Foundations; A Case Study

Sonic Echo (SE) testing method is a well-known, versatile method to gather information pertaining to unknown bridge foundations. Many studies on the applicability and methodology improvement of SE tests to evaluate individual piles and foundations supporting the superstructure have been reported previously. However, there is a rare opportunity for obtaining the performance of SE tests without the bridge deck. In the current study, three piles of a dismantled unknown bridge foundation were tested. Unusual vibrations on velocity signals were found which are independent of the location of the sensors. Such signals do not contain identifiable echoes from the pile toe. Therefore, they cannot be used to determine the depth of the piles. The results and observations of this study show that there is little future application for conducting SE tests on bridges that are out of service.

Evaluation of Unknown Bridge Foundations Using Borehole-based Nondestructive Testing Methods: A Case Study in Urban Settings

There are a significant number of bridges for which information regarding the foundation is missing or incomplete. It is extremely challenging to evaluate the performance of such unknown foundation bridges (UFB), particularly against scour or when their foundations are reused. For critical UFB, it is often necessary to estimate performance by developing an appropriate working model of subsurface foundation conditions. Typically, nondestructive testing (NDT) has served as the most viable alternative due to the costs and risk associated with excavation, coring, and probing. NDT can be quite difficult to perform and their results can contain significant uncertainty in highly urban settings. The primary objective of this study was therefore to compare performance of borehole NDT methods when evaluating the depth of two in-service unknown foundations (concrete-filled steel pipe piles and H-piles) in highly urban settings. The borehole magnetic, parallel seismic, borehole sonic, and borehole radar methods were implemented to determine the foundation bottom locations. Though uncertainty was present in all measurements, the borehole magnetometer and radar results proved the most conclusive. Parallel seismic testing did not yield any evidence of foundations due to issues with background noise and lack of direct access to the foundation. Likewise, borehole sonic testing was generally inconclusive due to issues with sensor directivity and attenuation. Borehole magnetometer estimated the depth to the foundation bottom as 8.6 m and 9.2 m at the two sites. Borehole radar estimates for the depth to foundation bottom compared favorably at 9.8 m and 8.0 m for the two sites. Given the borehole construction and depth to competent rock at the sites, these results for borehole magnetometer and radar were likely a minimum estimate for the location of the foundation bottoms. Such information can help evaluate long-term performance of this system as part of rehabilitation and reuse efforts.

Performance of Nondestructive Parallel Seismic Testing Method in Determining Depth of Shallow Foundations

AbstractParallel Seismic (PS) is considered a versatile method capable of determining the specifications of unknown bridge foundations made of common materials such as wood, steel, and reinforced c...

Practical Aspects of Nondestructive Induction Field Testing in Determining the Depth of Steel and Reinforced Concrete Foundations

Characterizing unknown bridge foundations has been a great concern for the Federal Highway Administration (FHWA) and Department of Transportation (DOT) in the past decades. Among conventional NDT methods, the Induction Field is a favorable nondestructive method to determine the depth of bridge foundations made of steel or reinforced concrete. Although many studies have been reported on the applicability of the method, the practical aspects of the method including the effect of major factors influencing the success of the method has not been completely discussed. In the current study, the effect of distance, soil type and soil moisture is investigated using two testbeds. The findings were valuable and provided practical guidelines to perform Induction Field tests on steel and reinforced concrete foundations.

Comparison of Borehole Ultrasound and borehole radar in evaluating the length of two unknown bridge foundations

Foundation length is an important parameter when assessing bridge vulnerability to failures related to scour hazards. As a result, multiple non-destructive testing methods have been developed to evaluate the geometry of unknown foundations, each with their own advantages and disadvantages. Subsurface methods that rely on measurements from boreholes alongside the foundation are often the most robust when evaluating foundation length, particularly for complex foundations (e.g. footings supported on piles). In this study, such a system was developed to evaluate the length of foundations at two bridge sites in Philadelphia using ultrasound acoustic waves (i.e. P-waves). Characteristics of the foundations and the site conditions are summarised as well as the ultrasound system components. The system was lowered in a borehole alongside each foundation as 100 kHz P-waves were generated to develop a reflection image of the pile–soil interface. Foundation length was evaluated based on discontinuity of the reflected...

Electrical Resistivity and Induced Polarization Imaging for Unknown Bridge Foundations

AbstractScour is the removal of soil around bridge supports due to water flow during floods. One of the major problems with scour is in the case of unknown bridge foundations. Bridges with unknown foundations are listed in the National Bridge Inventory as having insufficient data for scour evaluation, particularly regarding foundation depth. Knowing the foundation depth is a critical component of scour risk assessment. Multiple nondestructive testing methods are currently used to determine the depth of unknown bridge foundations; however, many methods are hindered by the type of substructure. An advantage of using near-surface geophysical methods, specifically electrical resistivity (ER) and induced polarization (IP) imaging, is that the inversion processes yield subsurface images, thereby allowing the depth and, to a lesser extent, the foundation type to be seen. Unlike a majority of existing testing methods, ER and IP imaging do not physically use the structure so they are applicable to simple and compl...

Electrical resistivity imaging of unknown bridge foundations

ABSTRACTUnknown bridge foundations pose a significant safety risk due to stream scour and erosion. Records from older structures may be non‐existent, incomplete or incorrect. We evaluate 2D and 3D electrical resistivity imaging (ERI) as a means to reliably identify the depth of unknown bridge foundations. A survey procedure is described for mixed terrain/water environments in the presence of rough terrain. Some electrodes are installed on the stream banks while others are adapted for underwater use. Tests were conducted at five field sites, including three roadway bridges, a geotechnical test site and a railway bridge, containing drilled shafts and spread footings of both known and unknown depth extent. The 2D data acquisition was carried out in the dipole‐dipole configuration. The 2D ERI method resolved the shape and depth extent of the larger bridge foundations but, with less accuracy, the shape and depth extent of the smaller foundations. The 3D ERI method is time‐consuming and does not add sufficient additional value over 2D ERI to become a practical tool for unknown bridge foundation investigations. The 2D ERI method is a cost‐effective geophysical method that is relatively easy to use by bridge engineers.

Evaluation of Unknown Foundation Depth Using Different NDT Methods

Many of the older bridges in the United States have no original contract documents available, and about 26,000 bridges that are rated as scour critical have unknown foundation conditions. Thus, no information is available regarding the type, depth, geometry, or material of these scour critical bridge foundations. The unknown bridge foundations pose a significant problem to bridge owners because of safety concerns. This paper presents the determination of an unknown bridge foundation depth at Forth Worth, Texas. The bridge was supported by driven steel H-piles. Three nondestructive testing (NDT) techniques were utilized: (1) the parallel seismic (PS) method, (2) the sonic echo (SE) method, and (3) resistivity imaging (RI). The main objective of this present study was to compare the suitability of NDT techniques to determine the unknown bridge foundation depth. Based on the field test results, both PS and RI methods provided foundation depth close to actual foundation depth. However, the SE method was determined to be unsuitable for determining the unknown steel H-pile depth.

MEASUREMENT OF UNKNOWN BRIDGE FOUNDATION DEPTH BY PARALLEL SEISMIC METHOD

MEASUREMENT OF UNKNOWN BRIDGE FOUNDATION DEPTH BY PARALLEL SEISMIC METHOD

Combined Measurement of Unknown Foundation Depths and Soil Properties with Nondestructive Evaluation Methods

Simultaneously determining both the depth of unknown bridge foundations and the measurement of soil properties along the length of the unknown foundation allows for a more complete and accurate analysis of foundation capacity and scour susceptibility. Foundation depths are measured by the parallel seismic testing method, whereas soil properties are measured with a seismic cone penetrometer. The new combined technique has a great advantage over previous foundation-testing systems in that no borehole is required for either test. Instead, the transducers used to collect all of the required data are mounted together into the same cone probe and pushed into the ground hydraulically from a track-mounted mobile rig. Field testing of the new technique has been carried out and shown that the system is capable of quickly and accurately measuring foundation depths and soil properties on a variety of soil types.