R Kromanis, P Kripakaran, Univ of Exeter, W Harvey, Bill Harvey Assoc, Exeter, UK
Many bridges in the Netherlands have been built during the 1970’s and as such were not designed for today’s traffic. As a consequence the Dutch Ministry of Infrastructure and the Environment has initiated a program in which existing bridges are inspected and re-examined and in selected cases the load-capacity is assessed by performing numerical analyses. One such bridge is the Heteren Viaduct. The concrete structure is a 17-span double-box girder Rhine Bridge with a length of 974 meters and width of 16.85 meters. During inspection of this viaduct shear cracks were observed in the webs. This bridge has subsequently been analysed using a newly developed “Stiffness Adaptation” method in the DIANA Finite Element program. The method allows the calculation of crack patterns, crack widths and onset of reinforcement yielding. A new and efficient modelling and analysis strategy has also been developed for the assessment. In this strategy a 3D solid model is generated, based on a CAD-model of the bridge. Automatic mesh generating procedures are used so that all details can be modelled in a reasonable time. This paper shows a new approach for both designing and re-assessment of structures using a 3D finite element analysis to perform non-linear analysis using the Stiffness Adaptation method. It can be seen this can be used for very detailed models while significantly reducing run times with improved confidence in the results therefrom.
1272
DEVELOPMENT OF BRIDGE INSPECTION TECHNOLOGY WITH SUPER HIGH RESOLUTION DIGITAL IMAGE AND IMAGE PROCESSING TECHNOLOGY FOR CRACK DETECTION
T Yamamoto, Y Maeda, Y Fukunaga, T Matsui & M Ohara, West Nippon Expressway Co. Ltd, Osaka, Japan
The importance of inspections is getting increased in maintenance of concrete structures of expressways, as the amount of aged structures is increased. In order to increase accuracy and reliability of general structure condition assessments, we, NEXCO-West, one of the operators of expressways in Japan, developed an innovative inspection method using super high resolution digital image and image processing technology to obtain qualitative data of cracks on concrete surface, location, width and length. With this method, we can acquire a super high resolution digital image for each span of bridges, and detect cracks. The data are provided to engineers for their subsequent structural diagnosis and rehabilitation planning. A historical record of cracks for use in monitoring crack propagation over time can also be acquired. It is expected that with this technology, the reliability of inspection is increased and the decision making of owners becomes more effective. This paper reports the outline, status and perspectives of development of the technology.
1177
APPLICATION OF ACOUSTIC EMISSION MEASUREMENTS IN THE EVALUATION OF PRESTRESSED CAST IN-BETWEEN DECKS
P van Hemert, SAAM Fennis, DA Hordijk, TU Delft, The Netherlands
A large number of concrete structures, that is built in the sixties and seventies of the twentieth century, need to be re-evaluated. It should be judged whether their capacity is still sufficient for the increased traffic loads. Acoustic emission (AE) is a non-destructive technique that can possibly be used to get a better insight in the structural state of these concrete structures. However, interpretation the AE measurements is challenging and is even more difficult when the concrete is cracked by for example alkali–silica reaction. Due to the existing cracks the wave attenuation affects the acoustic emission measurements. For an investigation into the capacity of pre-stressed cast in-between decks a 1:2 scale bridge was loaded in the Stevin laboratory of Delft University of Technology under two-way shear. In this preliminary research it was investigated whether AE-measurements can be used to get an idea about the structural condition of a structure, or more precise, to what extent the ultimate capacity is reached. For testing the concrete in-between decks a cyclic loading procedure is applied. It appeared that cyclic loading resulted in a lower capacity in comparison with the previously performed static loading experiments. There was no AE indication of early failure due to cyclic loading. Usually applied parameters, like ‘Kaiser Effect’ and ‘Calm Ratio’ are investigated. Furthermore, it was investigated whether the location of cracks could be determined by the emitted sound during the fracture process and applying a relatively large numbers of AE-sensors (so-called source location). In this article the performed AE measurements are reported and results discussed.
1227
IMPACT ELASTIC-WAVE METHODS FOR DETECTION OF GROUTING CONDITION IN POST-TENSIONING TENDON DUCTS OF PC MEMBERS USING ADAPTIVE NOISE CANCELLER
S Hattori, T Kamada, Osaka Univ, S Uchida, Ritsumeikan Univ, Japan
Recently, non-destructive testing methods of pre-stressed concrete (PC) structure with post-tensioning steel are considered to be highly important, because the corrosion of steel components, such as steel bars or steel strands, finally, will possibly cause degradation of a whole bridge. Though the grouting of duct inside sheaths prevents corrosion, it was reported that serious corrosion actually happened in many PC bridges in service. Thus, precise and quantitative non-destructive evaluation methods are highly required for effective repair or strengthening work of them.
Feasibility of impact-elastic wave method using adaptive noise canceller has been investigated for this purpose. In this method, simultaneous multi-point responses activated by a single-shot impact is used. Generally, surface wave propagates dominantly on the surface of concrete and prevents receiving the reflection between concrete surface and ducts. For receiving the signal of grouting condition, transfer functions between the measured points are processed and tuned adaptively to cancel the surface wave. Consequently, each of extracted waves reflected from the ducts is piled and accumulated to form grouting condition visibly. Evaluation of this method was carried out by three reinforced concrete specimens where both grouting portion and non-grouting portion were artificially set in tendon ducts.
As a result of the collapse of a composite steel bridge on a major highway in Egypt, an investigation was launched to determine the main cause of the collapse. Prior to this investigation, there was no available data about traffic volume and truck gross weights. From early investigation, it was argued that the main cause of the collapse was a result of illegal heavy trucks. Others argued that the bridge collapsed as a result of fatigue. To determine which argument is closer to reality, it was decided to develop a new system for Bridge Weigh-In-Motion (BWIM), for the first time in Egypt. With the hope that the information gathered from this study, on an existing bridge on the same highway at which the bridge collapsed, could help in determining the main cause of the collapse.
To develop the new system for BWIM, a preliminary finite element analysis was performed to provide guidance for instrumentation plan. For axle detection, it is important to select a location which has the largest sensitivity to axle presence. Four concentrated loads were applied to the bridge model and the analysis was performed for this simple case of loading. Searching through all straining actions developed in the steel girder as a result of this simple case of loading, it was clear that as the axle load is transferred from the deck slab to the steel girder, vertical axial stresses in the girder web are developed. Another case of loading was applied to the finite element model: two concentrated loads near support representing a vehicle axle. As it is expected, the maximum shear stress occurs at the composite section center of gravity. In this method, instead of measuring the shear strain, the diagonal tensile strain, oriented 45o from the pure shear plane, is measured. The conclusion from the preliminary finite element analysis is to instrument the web at midway between transverse stiffeners by placing the strain gauges oriented vertically near the top flange at a distance equals 15% of the web height. With regard to vehicle axle load and detection, the web is instrumented with a strain gauge oriented 45o at the composite section center of gravity near the bridge support. From this study, a new system for BWIM emerged. It is called Bridge-Weigh-In-Motion Web Axle Detector (BWIM-WAD). All the information required are gathered through instrumenting the girder web at two different locations along the girder span. This new system is simple, yet accurate, and provides all necessary information; axle load and spacing, vehicle speed and gross weight.
Concrete Bridge Investigation & Repair
1340
EMERGENCY FOUNDATION REPAIRS TO THE LEO FRIGO MEMORIAL BRIDGE: QA/QC CHALLENGES AND SOLUTIONS
B Hertlein, GEI Consultants Inc, Libertyville, IL, J Dohlby, URS Corp, Milwaukee, WI & T Buchholz, Wisconsin DoT, Green Bay, WI, USA
The Leo Frigo Memorial Bridge carries Interstate Highway 43 over the Fox River near its mouth into Lake Michigan’s Green Bay, just north of the city of the same name, in Wisconsin, USA. Construction started in 1977, and the bridge opened to traffic in 1980. On September 25, 2013, motorists reported to authorities that a section of the bridge appeared to have sunk a foot or more. Immediate investigation revealed that a pier within a 400-foot long portion of the bridge had indeed settled more than 2 feet, and the bridge was immediately closed to traffic.
The bridge is a critical link in both a major urban arterial route for the city of Green Bay, and the Midwest interstate highway network, so the economic consequences of closure were significant to both the city of Green Bay, and the States of Wisconsin and Michigan. The Wisconsin Department of Transportation responded with an emergency assessment and repair plan that involved the construction of a total of 20 drilled shafts adjacent to the original foundations of the five piers in the affected part of the bridge, with a very tight construction schedule that required work shifts around the clock. Adverse ground, access and weather conditions along with 24-hour shifts created a highly challenging environment in which to construct the new foundations, and the QA/QC program for the new foundations was a critical component in meeting the accelerated construction schedule.
The outcome of the project was that the bridge was reopened to traffic 102 days after it was closed. This paper focuses on the challenges met and overcome by both the foundation contractor and by the testing team that was tasked with verifying the quality of the new foundations under such challenging conditions, and recommending repairs for the surprisingly few construction issues that were uncovered by the QC program.
1277
SEISMIC VULNERABILITY OF BRIDGES OF ITALIAN MOTORWAY NETWORKS
G Pasqualato, C Bafaro, Sineco S.p.A., Milan, P Crespi, Politecnico di Milano, N Giordano, N Longarini, M Zucca, CIS-E Consortium, Milan, Italy
In recent years, Italian technical-scientific community has increased its interest on the evaluation of the seismic vulnerability of existing structures. Among this wide range of structures, motorway viaducts stand out for their strategic relevance and technical complexity. Most of these structures were built between ’60 and ’70 years, according to design procedures which ignored nowadays knowledge in seismic engineering.
Thus, the necessity to evaluate the real strength capacity of these structures with modern analysis techniques has become essential, leading to the determination of their safety level in case of an earthquake. For the assessment of several bridges of a motorway network, a multi-modal pushover analysis approach has been considered. This analysis technique allows considering the nonlinear behaviour and the complex dynamic response of such a structures without exceeding in high computational costs.
Some basic rules were defined (constitutive laws of materials, finite element type, plastic hinge models, etc.) for the modelling of viaducts in a commercial FEM software, in order to guarantee homogeneous comparable results among the large number of bridges of a network. Furthermore, a specific software routine was implemented. This routine starts from the pushover results of a FEM commercial software and executes the modal combinations and the safety verifications, reducing the time cost and the possibility of errors, following in the evaluation of the seismic vulnerability indexes.
These risk indexes are then reported in seismic vulnerability forms collected by the Italian Hazard Management Agency (Italian Civil Protection) for risk management purposes.
1285
EXPERIMENTAL EVALUATION OF AS-BUILT & RETROFITTED TWO-COLUMN BRIDGE BENTS UNDER VEHICULAR COLLISION FORCE AT THE BENT COLUMN
N Wehbe, South Dakota State Univ, Brookings, SD, B Tigges, Raker Rhodes Engineering, Des Moines, IA USA
Current AASHTO-LRFD Bridge Design Specifications require a bridge column to be designed for a collision load of 600 kips (2680 kN) applied laterally at 5 ft (1525 mm) above ground. This requirement is set to prevent bridge collapse under the extreme event of a semi tractor-trailer collision with the bridge column. The majority of overpass bridges on the interstate system and other major highways in the United States were designed and constructed prior to the development of the collision load design requirements. In non-seismic regions where the lateral seismic loads on bridge columns are negligible, and in the absence of other significant lateral load requirements such as ice or collision loads on bridge piers, bridge columns were designed for low lateral load demands that did not govern the design of the columns. Therefore, the confinement/shear reinforcement in such columns was kept to the minimum transverse steel requirements specified in the prevailing codes at the time. In the case of a heavy truck collision incident, columns that lack sufficient shear strength and ductility capacity due to inadequate transverse reinforcement would be vulnerable to catastrophic failure and may consequently lead to bridge collapse. A companion study on collision hazard risk analysis in South Dakota identified a two-column bridge bent type to be economically critical and vulnerable to collapse. This paper presents an experimental evaluation of the structural performance of the vulnerable two-column bridge bent type when subjected to the AASHTO’s collision load. Two one-third scale bridge bents were tested in the laboratory. One specimen represented the vulnerable prototype bent. The other specimen was retrofitted with a “crash strut” that the State of Minnesota is implementing to prevent bridge collapse under collision loads. In this paper, the test results are analyzed and the effectiveness of the crash strut is evaluated.
1328
REPAIR & STRUCTURAL STRENGTHENING OF OVERHEAD R.C. BRIDGES FOR PETROLEUM PRODUCTS CONDUITS
Prof A Shilin & Dr D Kartuzov, ZAO “Triada-Holding”, Moscow, Russia
A new approach is analyzed to repair of overhead bridges for petroleum products conduits, reinforced concrete structures of which are subject to negative impact from leakages. The approach combines refurbishment of structural damage and subsequent strengthening of the repaired structures with CFRP products.
The core element of the strengthening system is a high-adhesion polymer cement matrix which, on one hand, protects structural reinforcement from further corrosion and, on the other hand, provides strong bond between composite products and structural concrete.
The repair was done without interruption of petroleum conduit functioning. As a result, structural service life was extended substantially.
1365
INSPECTION AND CONDITION EVALUATION OF GREEK OLD CONCRETE RIVER ROAD
I Papayianni, E Anastasiou & M Papachristoforou, Aristotle Univ of Thessaloniki, P Panetsos, Egnatia Odos S.A, Thermi, Greece
A great number of river bridges in Greece were constructed after the Second World War. Nowadays, their age exceeds 40 years and they are still in operation. The Laboratory of Building Materials at the Aristotle University of Thessaloniki in cooperation with Department of Bridge Maintenance of Egnatia Odos S.A. and relevant sectors of the local Prefecture has undertaken a survey of concrete members of the bridge structural system. This survey includes:
- A systematic visual observation of concrete members.
- The production or update of the geometry of the bridge structure “as designed”.
- The pathology maps concerning cracks, spalling/swelling, efflorescence pop-outs, calcium leaching, surface water abrasion and locations of reinforcement exposition and corrosion.
- The identification of the actual mechanical characteristics of the bridge (elastic modulus of elasticity etc), based on the evaluation of site material and laboratory tests and on other inspection findings that are used to reconstruct the analytical static model of the bridge. Non-destructive methods and drilled cores have been used for this puprpose.
- The determination of porosity, PH, carbonation depth of concrete, as well as chloride and other salt content. Microstructural observation with stereoscopic methods was also used to complete or help with the recognition of the deterioration mechanism.
The results from three surveyed bridges are presented and commented. The topography of damage and the mechanisms of corrosion or any other concrete deterioration have been recognized. In addition, comparing our results with those of the archives of Egnatia Odos S.A., it seems that there are some areas in bridges which are more prone to damage. These areas could be protected more in order to prolong the service life of concrete bridges. Technical faults associated with the drainage system cause failures and premature corrosion repeatedly. Although most of the concrete bridges are near the sea (at a distance of 1 km) the concrete does not show relatively high content of chlorides, while carbonation depth is generally low. Taking into account the results and remarks from the survey, the repair of bridges (materials and techniques) is expected to be more effective.
1278
EVALUATION OF STRUCTURAL BEHAVIOR OF CORROSION DAMAGED REINFORCEMENT CONCRETE BRIDGES
J Nepal & H P Chen, Univ of Greenwich, Chatham, UK
Corrosion of reinforcement is one of the major causes of deterioration of reinforced concrete (RC) structures exposed to aggressive environments, such as highway bridges. The serviceability and durability of the RC bridges are often challenged by reinforcement corrosion. As a result, they cannot serve for the full service life as they are designed for. The increasing number of aging and deteriorating RC bridges has caused great loss in infrastructure management industry. Therefore deterioration of the corrosion affected RC bridges is of greater challenge both technically and economically. The damage caused by corrosion occurs in the form of cracking, eventual spalling of concrete cover and reduction in cross-section of reinforcement bars. If the corrosion continues it affects the bond mechanism between the reinforcement and concrete which consequently influences the overall behaviour of the structures in terms of both ultimate and serviceability limit states. Assessment of structural behaviour of corrosion damaged RC bridges is essential to estimate the residual capacity of the structure which ultimately aids in making decisions for reliable and cost effective infrastructure management. Conventional design methods do not provide procedures to predict the structural behaviour of corrosion damaged RC structures. This paper investigates the different types of defects caused by reinforcement corrosion and its impact on the structural behaviour of these corrosion damaged RC structures.
