Inspection of bridges in the United States has been regulated by the federal government since 1968, when a national bridge inspection program was established that recognized the need for periodic and consistent bridge inspections. The first National Bridge Inspection Standards (NBIS) were developed in 1971. Since then, inspection standards, policies, and procedures have continued to evolve. This paper describes some of the recent changes and trends with bridge inspection practices in the United States.

More than 30 years have passed since the steel plate bonding technique was applied for the first time to reinforced concrete (RC) slabs of road bridges in Japan as a strengthening measure against fatigue damage. Debonding of the steel plates as well as damage in concrete are often found as a dull sound during hammer tests. Efforts are being made for more frequent inspections; however, visual observation has a limitation in detecting damage in the concrete of the repaired slabs which are covered with steel plates at the bottom. Although the presence and extent of debonding can be roughly known from the change in sound during hammer tests, there are no decisive methods to detect or evaluate the internal damage of the concrete. The purpose of this study is to establish a method to evaluate damage in concrete of steel plate-bonded RC slabs on road bridges in service, with the focus placed on the temporary set anchors in the repaired slabs which had been used to hold the steel plates until settlement of adhesive agent for secure bonding. The proposed technique utilizes the anchor bolts as ultrasonic probes.

RC bridge deck replacement will be taking more than half of budget in intensive renovation program of road investment in Japan. Prolong life-time measures such as improvement of the materials and effective repair methods to sustain a long life span are thus studying rigorously. Those countermeasures are implemented when the damage or deterioration becomes remarkable as to be observed by naked eyes, and therefore these activities can be regarded as a corrective maintenance activity, contrary to proactive maintenance. As for the proactive maintenance overall health evaluation for the infrastructures even in the early damage/ deterioration stage would be vital. Acoustic emission is an elastic wave generated due to cracks occurrence, growth and nucleation, and these AEs are referred to as primary AE activity while the emissions due to existent cracks’ reversible motion induced by internal stress distributions are referred to as secondary AE activity. In general the further deterioration proceeds, the more intensive AE activity are obtained. While as for the elastic wave velocities within the objective, smaller velocities imply more deteriorated condition than that of large velocities. Accordingly, it can be appeared that small velocity with remarkable AE occurrence could suggest serious deterioration condition; however careful examinations of AE activity in combination with wave velocity in seriously fatigue-damage RC deck questions this fact, e.g., serious damage areas, assumed both from elastic wave velocity and developed cracks on the surface, generates less emissions than of miner damage. This study details those findings with on-site AE monitoring and AE tomography results.

POST-TENSIONING GROUT PROBLEMS Bonded post-tensioned structures are at increased risk of corrosion and failure of the tendons when there are defects in the installed grout. The most common grout problems (defects) include: • Voids: Voids are common at high points of tendon ducts as a result of grout bleeding and inadequate grouting. Standard cement/water grout has typically produced grout with 3 to 5% bleed. • Chloride contaminated grout: Chloride contamination may result from the use of chloride contaminated grout or mixing water or the long-term exposure of the structure to marine environments or de-icing salts. • Soft grout: Soft grout may be created if excessive water is added during grout mixing, and wick induced bleeding causes localized grout with high water-cement ratio. THE SOLUTION The Post-Tech PTI Impregnation system has been developed to mitigate corrosion caused by these problems. The system utilizes the interstitial spaces between the wires of each strand in a multi-strand tendon to deliver (transfer) a unique corrosion inhibiting, impregnation material along the length of the cable. The impregnation material seeps between the wires of the strands to impregnate the surrounding grout or concrete. The impregnation material is designed to form a corrosion-resistant film on any exposed steel surfaces such as steel strands which are exposed in grout voids, and to make the grout more corrosion and moisture resistant. Laboratory Confirmation Laboratory confirmation was completed on tendon specimens provided by one DOT and grouted “lollipop” samples. The tendon specimens provided to Vector were sections of external tendons which had been removed from an existing bridge. Lolipop samples comprised a single strand section which was centrally grouted in a cylindrical block of prepackaged PT grout. Laboratory testing confirmed the ability of the impregnation material to travel along the length of the specimen, to soak into the grout surroundingthe strands and to pass from strand to strand across the cross-section of a grouted tendon. Accelerated laboratory testing also confirmed the ability of the impregnation process to reduce corrosion by over 90%. Field Demonstration and case study The demonstration project was completed on external tendons in a box girder bridge in Jacksonville, FL (I-95 / I-295 Interchange). The demonstration project verified the capability of impregnating the full length of 256’ and 205’ grouted tendons from end anchorage locations, the capability of impregnating up to 100’ in each direction from a mid-point location, and the capability of the impregnation material to penetrate the grout adjacent to the strand. FDOT has implemented PTI Impregnation on the tendons of I-4 Connector in which soft grout was found. All selected tendons were successfully impregnated. Free water/moisture was pushed out of the tendons during the impregnating process. CONCLUSIONS Laboratory testing confirmed the ability of the impregnation material to travel along the length of the specimen, to soak into the grout surrounding a strand and to reduce corrosion by over 90% when exposed in an accelerated corrosion cell. Field demonstration at the I-95/295 Interchange in Jacksonville, Florida and Implementation on I-4 Connector in Tampa, Florida has demonstrated the following: • All strands of 256’ long grouted tendons can be impregnated full-length from an end anchorage location, • Impregnation material can flow up to 100’ in each direction from a mid-point location,. • Impregnation material can penetrate grout adjacent to a grouted strand, and • Free water/moisture can be pushed out of the tendons during the impregnation process.

While the period of high growth of Japanese economy, infrastructures were actively constructed. Now the structures are aged and its evaluation of integrity is one of significant topics to keep its serviceability and safety in Japan. Although the authors have been studied on tomographic techniques that are on the basis of elastic wave propagation for the evaluation, elastic wave difficultly propagate inside of structures if the structures are covered by stiff materials, e.g. steel reinforcement, and evaluation of integrity of the structures is difficult as consequence. Further, electromagnetic waves have been widely used for the inspection of concrete structures as well. However, dissipation rate of the electromagnetic waves is generally high in metals, and it is also difficult to penetrate inside of the structures. On the other hand, neutron beam is known as a radioactive ray which permeability is high and it would be applicable for the inspection of inside of the concrete structures. Thus, in this study, permeability of neutron beams to concrete specimens is discussed as preliminary study for establishing the inspection technique of concrete structures with neutron beam.

Main infrastructures in Korea are maintained according to the result from periodical in-depth inspection. The process is based on the ‘Special Act on the Safety Control of Public Structures’ and accompanied specific guide. The Act has mainly focused on the physical condition and safety of structures up to now. Recently we are faced with the threats coming from aging of structures and climate change. These interior/exterior changes are strong challenges to maintain expected performance of structures. What is more, convenience for people and functionality are came to the fore as important indices. In these circumstances, the government of the Republic of Korea is preparing for a paradigm shift to performance-based maintenance system which can evaluate integral condition of structures with regard to the various performances. In this study, performance indices, detailed inspection items and following inspection techniques are defined. The grade assigning method using the results from inspection and integral evaluation procedure are suggested. This can be used for establishing a improved and long-term maintenance strategy toward an appropriate goal considering various performance characteristics.

The article presents an evaluation of geotechnical state on the project construction site and an evaluation of deep excavation impact on the current site development. It also provides an optimal design for the deep excavation, an impact analysis of horizontal shifts in the shoring of excavation, an assessment of bending moments in the shoring and the forces in thebracing structures. The numerical modeling was carried out for developing variants of the deep excavation as well as a preliminary assessment of the impact that the projectedunderground structure produces on the surrounding buildings and constructions. Some recommendations on choosing a reliable variant of the undergroundstructural arrangement and the engineering operational technology are suggested.

In this study, strain properties of high strength concrete (HSC) have been evaluated at elevated temperature. To evaluate the strain behaviour of HSC at elevated temperatures, ø100 × 200 mm cylindrical specimens of HSC with compressive strengths of 80, 130 and 180 MPa concrete were heated to 700 °C at a rate of 1 °C/min. As a results, Total strain of HSC was showing shrinkage with compressive strength increasing.

Recently, a possibility of the surface treatment material is expected as an integrated control method for various degradations of concrete structure. However, as experimental results, although water permeability of the concrete could be improved due to the surface treatment material, the scaling of surface layer was accelerated under freezing and thawing cycles. Furthermore, the mechanism of scaling acceleration has not been clarified yet. Therefore, in order to clarify the mechanism accelerating the scaling of the treated concrete, the behavior of variations in the moisture and ice contents in the concrete were investigated especially based on a simulation analysis using a simultaneous heat and moisture transfer equation for a three-phase system. The analysis simulated the freezing-thawing process in the RILEM CIF/CDF test. And the mechanism accelerating the scaling is discussed based on the differences of the freezing behavior due to the infiltration depth of the surface treatment material. As the results, in the case of the smaller infiltration depth, it has been clarified that the reason to accelerate the scaling is the increasing of the ice content at the boundary between the treated and untreated regions.

Recently, localized rainfalls and torrential typhoons due to the abnormal climate have increased in Korea and the damage situation caused by debris flow at Umyeon Mountain has especially take place a big social issue. However, the standardized damage investigation does not yet exist and the systematic analysis of the data has not also been carried out. In this regard, this study developed assessment factors to conduct standardized damage investigation for debris flow. To achieve this, preliminary assessment factors were derived from analysis of literature review and the Delphi method through 12 experts who work at fields of facility, academia and industry. As a result, 29 rational check lists of 6 groups were determined.

Four shear-deficient reinforced concrete (RC) beam specimens with different shear span ratios were tested using a well-instrumented drop-weight impact machine to gain a better understanding of the effect of shear span ratio on impact behavior of RC beams strengthened with carbon fibre reinforced polymer (CFRP). The results demonstrated that the shear span ratio could change the failure modes for strengthened specimens and also affect the impact resistance.