Reinforced concrete bridge columns with hollow section subjected to inelastic cyclic loading during an earthquake have been reported to suffer from the damage at not only outside face but inside face, where is invisible at the bridge inspection. Therefore it is important in the seismic design to determine the acceptable limit-state for the RC hollow columns in terms of inspectability and repairability. However there are few researches on the seismic performance of the RC hollow columns, particularly with high longitudinal steel ratio and high axial loading.
 In this research, the failure mechanism of the RC hollow columns at both outside and inside faces was clarified based on the cyclic loading tests for scaled-model columns and the effect of axial load on the seismic performance of the RC hollow columns was also examined. Test results showed that the position of the neutral axis significantly affected the failure mechanism of the RC hollow columns.

View full abstract

 In this study, a corrosion accelerating test and loading tests were carried out for specimens of high strength bolted joints to clarify the relationship between corrosion and remaining strength of the corroded joints in the inner or outer surface. In the corrosion accelerating test, corrosion condition of the bolts and the inner surface of the joint, roughness and bolt axial force etc were measured. In the loading tests, slip coefficient, slip strength, yielding strength and maximum strength were obtained.
 From the results of the tests, the slip strength and the slip coefficient are increased and the bolt axial force is decreased because red and black rust are generated and increased in the inner surface of the joint. The yielding strength and the maximum strength are little changed in the tests.

View full abstract

 Deterioration or health data base of infrastructure contains various types of structures and deterioration mechanism. It is preferable to separate the data according to detailed information before estimation of regression curves. It is, however, difficult to collect all relevant data to separate them. This study proposes the method to separate data and perform regression analysis at the same time statistically by EM algorithm and information criteria. We verify the usefulness of the proposed method by numerical experiments in which hypothetical data is generated from three lines. Four regression curves are estimated from an actual bridge deterioration data base by the proposed method. The physical meaning of separated groups is interpreted to some extent. It is shown that the proposed method can be useful to separate and perform regression analysis of large scale data base.

View full abstract

 Great geo-disaster occurred during the 2008 Iwate-Miyagi Nairiku Earthquake. Reliable estimation of seismic motion at damage sites is required to clarify the mechanism of damage. In this study, accuracy of the method to estimate strong earthquake ground motions was investigated quantitatively at the observing stations in the focal area by comparing the estimated ground motions with the observed ones. The results indicates that the methods based on the aftershock observation or microtremor measurement at the damage site lead to reliable estimation of strong ground motions.

View full abstract

 The beam-to-column connections of steel rigid-frame piers are important in that they have a considerable impact on the seismic performance of the piers. The elastic design method based on the local peak stress which is produced by shear lag on the flanges of the beam-to-column connections has been applied in such connections until now.
 The purpose of the authors' research is to ascertain the performance and limit state of the fillets which are installed on beam-to-column connections in order to improve the fatigue performance, and to establish the verification method of limit state for developing the rational design method of the beam-to-column connections. To this end, loading tests and elasto-plastic finite displacement analysis were conducted on test specimens with the same structural parameters as actual structures.
 A review of the experimental and analysis results reveals the performance. Furthermore, the limit state of fillets is clarified by investigating the relation between the performance of a fillet and design load. As well, the performance verification method is proposed based on these results.

View full abstract

 The instrumental seismic intensity by JMA is used the filter of three types which consist of high cut, low cut and period function. An extended function of the low cut filter is used to evaluate the effect of long-period range on seismic intensity in the paper. An asymptotic filter processing of acceleration in the extended function is proposed to express the seismic intensity corresponding to velocity and displacement. The seismic intensity level using the running r.m.s. method is applied to clarify the effect of various frequency weighted acceleration on seismic intensity. The seismic intensity level to velocity and displacement is also discussed by comparing with spectral characteristics.

View full abstract

 The objective of this study is to obtain reinforcing effect and strength characteristic of bonding method of carbon fiber sheet with joint for steel members. Uniaxial tensile test of steel plates bonded CFRP strand sheets with joints was carried out. As a result, there were no ruptures or delamination of the sheets until reaching yield stress of SBHS700, which was a kind of high strength steel, when the length of the joint was equal to or greater than 20 mm. In test pieces whose strength were below yield stress of the steel, cohesive failure of adhesive occurred at the edge of joint, and crack propagated in the joint. Moreover, finite element analysis and semi-analytical method were conducted in order to investigate on failure mode and strength characteristic of joint.

View full abstract

 The thickness reduction due corrosion of weathering steels can be estimated by using alloy index V and local corrosive environment index Z. However, it is required to calculate Z that costly measurement of air borne salt, sulfur oxides and so on. Thus, atmospheric corrosion monitor sensor (ACM sensor) was examined as an alternative way of environmental corrosivity measurement. At first, characteristics of ACM sensor output were checked by laboratory test. Then, the measurements of environmental corrosivity with ACM sensor were conducted at exposure test sites under un-sheltered condition. ACM sensor output and corrosion behavior of weathering steels were compared to identify adequate index of ACM sensor output. As a result, followings were obtained: (1) ACM sensor's output current was not affected by temperature. Thus, temperature must be considered as an additional factor. (2) Annual electric charge Q_ACM was suited as an index of ACM sensor output because log (Q_ACM) was proportional to corrosion rate parameter B_s of Y = A_sX^B_s . (3) The estimation equation of thickness reduction due corrosion was statistically obtained as Y = (166 + 8.71/V - 0.276Q_ACM - 0.480T) X^{(0.326/V + 0.0918 log(Q_ACM - 0.0165T) - 0.154[Cr])} , where Y is thickness reduction due corrosion [μm], X is exposed period [year], T is annual averaged temperature [K] and [Cr] is mass percent of chromium in the steel. It might be said from the findings in this study that thickness reduction due corrosion of new weathering steels can be estimated more accurately by combination of one year exposure test of small samples for A_s and ACM sensor measurement for B_s.

View full abstract

 Since surfaces of the weathering steel bridges with supplemental rust controlling treatment show ununiformly-distributed weathering properties, it is difficult for inexpert engineers to judge its surface states only by known visual inspection method. In order to improve such situation, the applicability of ion transfer resistance method to surface treated weathering steel bridges is verified. It is confirmed that the method based on ion transfer resistance measurement is very useful to evaluate the degradation stages of weathering steel bridges which are coated with supplemental rust controlling film.

View full abstract

 In order to prevent serious damages of anchorages that are hard to be repaired, the seismic design code after the Kobe earthquake adopts a new capacity design concept that strengths of anchorages must exceed those of pier cross sections at the base. In case when the anchorages constructed before the Kobe earthquake are upgraded after the Kobe earthquake, a similar capacity design concept is adopted. However, more damages are allowed in these anchorages for the ease of upgrading. In the modeling of the above two types of anchorages in the seismic analysis, however, pier bases are equally assumed to be rigidly connected to concrete footings in spite of the difference of the damage level allowed to the anchorages. Herein the validity of the assumptions of rigid connection for two types of anchorages is examined under more realistic bi-directional cyclic load as well as unidirectional cyclic load. In addition, the effect of the pier-base restraint is investigated on the ultimate behavior of steel bridge piers.

View full abstract

 About 50,000 steel railway bridges are in service. More than half of them have been in service over their design lifetime. Some of these bridges have problems such as corrosion and fatigue. To improve the performances of the existing bridges without replacement of them, we proposed a method to install concrete decks on the existing steel girders. By this method, the structural system of the bridge can be changed into composite girder. To realize this technique, it is necessary to apply pre-cast concrete decks in order to enable short-time installation work. To install the pre-cast decks, connection by filler mortar is possible to be applied. Then, it is necessary to clarify the strength of the girder-deck connection and deck-deck connection using filler mortar.
 In this study, loading tests of composite girder that was fabricated using proposed method were carried out in order to evaluate the structural performance of the girder and to observe failure mode of the connection. As a result, it was found that the bending stiffness and the yielding capacity of the girder were improved comparing with steel girders. At the girder-deck connection, the failure occurred at the steel-mortar interface at the girder end. Finally, we obtained shear strength of the girder-deck connection and it was found that the proposed method is applicable to actual railway steel bridges without failure of the girder-deck connection.

View full abstract

 Under heavy traffic condition, some fatigue cracks have been found at welding joint between U-shaped ribs “trough ribs” and deckplate. In Japan, these plate thicknesses are specified in the fatigue design guideline for highway bridges, and these combination are limited. So, we conducted fixed-points fatigue tests with real scale partial specimens consisted with two trough ribs and a transverse girder, and the elastic FEM analysis for these fatigue tests. Based on these results, we studied on the characteristics of the fatigue cracks focused on plate thickness. Among these studies, we proposed “the variation of synthetic strain”, which is the synthesis of amplitude of strains in 3-deirections, as a quantitative indicator for evaluation of durability of such welding joints.

View full abstract

 During the Kobe earthquake, unexpected brittle fracture occurred in a corner of steel bridge bent. This study focuses on the local temperature rise which is caused by cyclic plastic deformations and influences the brittle fracture initiation. The temperature rise during an earthquake is accessed by the elastic-plastic finite element analysis coupling heat transfer calculation. The temperature rise at a normal steel bridge bent corner and its effect on the fracture toughness are evaluated. The analytical results indicate that, in some cases, the increase of temperature exceeds 30 degrees Celsius. It is estimated that the dynamic effect on the fracture is quite sensitive to the temperature rise; the dynamic effect change from the accelerator to inhibition factor of fracture during the temperature rise.

View full abstract

 On March 11, 2011, the Great East-Japan earthquake with M_w 9.0, the largest ever recorded in Japan, shook northeastern part of Japan and was strongly felt in the Yokohama-Bay Bridge area with the JMA seismic intensity 5- (lower 5). Yokohama-Bay Bridge with the total span length of 860m is densely instrumented with vibration sensors that record seismic excitation during the main shock and several after-shocks. These series of seismic responses create the most comprehensive set of data on the response of long-span cable-stayed bridge subjected to multiple-support excitation. This paper describes investigation of seismic records by focusing on temporal and spectral analysis of the bridge accelerations, dynamic characteristics of the bridge and their changes throughout the excitation, investigation of response non-linearity during large excitation, performance evaluation of the seismic isolation device: link-bearing connection between girder and towers, and the post-earthquake field observation. Seismic response of the bridge is dominated by transverse vibration; where the girder transverse vibration reached the maximum displacement of 62cm. Investigation shows that link-bearing connection functioned properly during the earthquake to accommodate girder longitudinal movement, while on lateral direction pounding at the wind shoe may have occurred. Changes in natural frequencies were observed during large excitation followed by the change in vertical-transverse coupling behavior of the mode shape. Despite the strong shaking, there was no significant structural damage observed on the bridge since the ground motions experienced was still far below the design and seismic retrofit ground motions.

View full abstract

 The tall noise barrier recently installed on Shinkansen structures has a low natural frequency; therefore, it may resonate with dynamic loads such as train winds which have not been a crucial condition for design. The aim of this study is to evaluate the dynamic response characteristics of the noise barrier and to propose a dynamic design method of the noise barrier on the basis of the measurement and numerical analyses. As a result of the study, it has been found out that the dynamic response of the noise barrier mainly results from the vibration of the middle slab excited by the train load when the train runs at the speed slower than 200km/h. On the other hand, more than 90% of its excitation is attributed to the train wind when the train runs at the speed faster than 200km/h, which indicates that for such high speed the design of noise barrier requires the consideration of only the train wind. The dynamic response of the noise barrier excited by the train wind consists of the resonance effect between pulse excitation of the train wind and the natural frequency of the noise barrier and overlapping effect of the tail pulse of passing train. In addition, the dynamic response of the noise barrier has been generalized and two design methods have been proposed: a precision method based on simulation and a simplified method. The range of application of 1.0kN/m² previously used as the design load has been made clear based on the natural frequency of noise barrier.

View full abstract

 Recently, many kinds of welding materials were widely used in fabrication of steel bridges. It was considered that the quality of these welding materials has been remarkably improved. However, the statistical characteristics of the material is not clarified. In this paper, we have investigated the 638 of welding materials on the basis of the mill sheet in order to clarify their quality. Investigated items were tensile strength, yield strength, Charpy-absorbed-energy, elongation and yield ratio, and these mechanical properties were shown. We also showed improvement in the quality, comparing with the conventional steel data and welding procedure tests date, which were SM490Y, SMA490W, SM570Q and SMA570W.

View full abstract

 The direction of the principal stress on gusset welded joint connected to a main girder web of a steel girder bridge changes instantaneously so that the direction of the shear stress reverses when a vehicle passes right above there. It is well-known that the fatigue crack initiates and propagates in the direction perpendicular to principal stress one, but fatigue crack propagation behavior and fatigue strength have not been made clear yet when the direction of principal stress changes. In the present study, for making the propagation behavior and the fatigue strength clear in the stress field where the direction of the principal stress changes, fatigue tests on girder specimens and fatigue crack propagation analyses have been performed.

View full abstract

 To improve the reliability of an inspection of civil structures, the expectation for health monitoring of a structure is growing. To develop a practical health monitoring system, it is necessary to build the system in which not only development of evaluation method but implementable sensor system which include AD converter. However, a monitoring system is developed on a seeds basis in many cases, it is difficult for sensor maker to grasp sensor spec the user expects. In this paper, for development of monitoring system, the required item was arranged and the feature of evaluation criteria was arranged using the actual monitoring data measured by the bridge pier of the railway bridge. Moreover, the example of specification was shown about accuracy or durability in terms of external force to assume or evaluation index. Reliable systems development is expected by the high added value with which the user and the maker were united for develop monitoring system.

View full abstract

 Many landslides occurred in a residential area on embankments in Midorigaoka, Sendai City, during the 2011 off the Pacific coast of Tohoku Earthquake. In this study, to evaluate empirical site amplification and phase effects, aftershock observation was conducted at the damage site. Using the site effects, we estimated the strong ground motions at the damage site during the 2011 main shock based on extended site-effect substitution method considering the contributions of soil nonlinearity and seismological subevents. The estimated waveform will be useful in the detailed study of the mechanism of damage.

View full abstract

 This paper deals with a human response exposed to vibration concerning bridge serviceability. Bridge serviceability test is conducted both on a existing pedestrian bridge with the fundamental frequency of about 2.1 Hz for vertical vibration and on a existing pedestrian suspension bridge with the center span of 62.4 m for lateral vibration. Based on these full scale measurements for both immovable standing position and footfall (walking), it was confirmed that pedestrians in immovable standing position might be more sensitive compared with footfall (walking). Bridge serviceability-acceleration characteristic for human response to the lateral vibration is also proposed from a bridge design viewpoint.

View full abstract

 The 2012 investigation report on the collapse of Kutai-Kartanegara Suspension Bridge in Indonesia revealed that the collapse was likely triggered by shear failure of the pins of the cable band's clamp in the middle of the center-span. It is suspected that the failure was caused by stress accumulation on the clamps that have been weakened by fatigue, initial fracture and corrosion. However, detail analysis on shear failure by fracture mechanics has not been conducted because the failed clamp that trigger the entire bridge collapse had dropped into the river and could not be recovered. In this note, the possibility of shear brittle fracture of the clamp's pin is discussed from a viewpoint of linear fracture mechanics by utilizing the measured Charpy absorbed energy. Several possible scenarios of defect sizes and stress conditions were assumed. The analysis shows that the shear brittle fracture is expected even under low shear stress level when several unfavorable conditions occur simultaneously.

View full abstract