This paper presents the recent development in the research and implementation of structural health monitoring systems for long span bridges in China. Following a brief review on the long span bridge projects in recent years and main deterioration and defects problems of existing bridges, the paper puts the focus on the review of the following three aspects: the implementation of structural health monitoring system for long span bridges, the advanced sensing, transmission, and system integration technologies, and the novel signal processing and condition assessment techniques. Finally, the issues on the future research and implementation of structural health monitoring system are discussed.

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A frictional force at bearing is one of the most important loads in a structural safety assessment of radial gates. But, variation of frictional coefficient during a service period of the gate has not been examined. In this paper, I perfomed a monitoring of gate arm strains of two in-service gates and estimated the frictional coefficients for each gate operation with direction changes. The estimated frictional coefficients for two gate bearings varied with coefficient of variance 0.11 and 0.18. And the frictional forces sustained till the next gate operations. According to these results, we should consider the friction variations, and coupling of the frictional force with earthquake in the structural safety assessments of the radial gates.

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Recently, structural damage detection methods using chaotic excitation have been proposed, where it has been demonstrated that response displacement shows a chaotic behavior by inputting an appropriate chaotic excitation to the structure. This study indicates that the clear difference can be confirmed in the response displacement after damage, and introduces the cross prediction error of the response displacement as a feature to structural health monitoring system using chaotic excitation. The performance and effectiveness of detecting the damage is discussed through numerical simulations. As a result, it is observed that the proposed method can make it possible to judge the structural conditions.

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This paper proposes a decision making method of the target reliability index for structual designers especially code-writers. First, two background concepts of performance based design, i.e., performance agreements and performance specification, is discussed. Conbinating these concepts, this study pointed out the target reliability index can be determined based on both user and designers decision making about their burden risks. This paper proposed a function to compute the target reliability index from the designer's burden risk determination.

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An investigation is made on how the coupling of bi-directional horizontal seismic excitations affects the ultimate behaviour of thin-walled stiffened rectangular steel columns used as bridge piers. First, an accurate bi-directional pseudo-dynamic test is conducted to examine their ultimate behaviour as well as to confirm the accuracy of the proposed nonlinear dynamic FEM shell analysis. Then, an instability criterion is derived to identify the ultimate state of columns. Finally, an extensive dynamic analysis under various bi-directional seismic excitations is carried out to confirm the accuracy of the proposed ultimate interaction curve expressed in terms of the two horizontal restoring force components.

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Detailed seismic damage analysis was conducted on a PC cable-stayed bridge damaged in the 1999 Chi-Chi Earthquake in Taiwan, using field measurement results and detailed drawings obtained from the administrator of the bridge. Through nonlinear dynamic analysis, it was found that the cause of damage to the bottom of the RC main pylon was the vibration on the high level mode. Also, it was found from the parametric study of ground motions that the earthquake response of PC cable-stayed bridges tends to become large if an earthquake dominating in a long-period component occurs.

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Specific seismic design methods of beam-to-column connections of steel rigid frame piers have not been established because the seismic performance has not been clear sufficiently. Moreover, the fatigue damage of beam-to-column connections is one of serious problems and structural details such as fillets and scallops were proposed for improving the fatigue performance. But the influence of them on the seismic performance of connections has not been obvious. In this study, experiments of beam-to-column connections were conducted in order to grasp the seismic performance of beam-to-column connections and to estimate the influence of structural details, steel grade and geometry on the seismic performance. Bucking parameters, steel grade and structural details of test specimens were decided in consideration of the survey results of actual steel rigid frame piers. From the experimental results, it was found that fillets and scallops dealt with in study have little effect on the seismic performance of beam-to-column connections and it is important to estimate the yield of web panels of beam-to-column connections adequately. Furthermore, methods for evaluating stresses on web panels of beam-to-column connections were proposed and the validity of the proposed methods was confirmed by comparing experimental results and calculations by the previous model with calculations by the proposed method.

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The object of this study is to clarify the corrosion mechanism of surface-coated steel and the deterioration progress of its surface coating in a marine environment. Taking into consideration that deterioration resulting from damaged surface coating is an issue in actual steel structures, the effect of damage in the surface coating on the progress of deterioration was investigated through marine environment exposure tests and submersion tests in the laboratory. Results: Coated steels in the splash zone, tidal zone, and submerged zone deteriorated in different manners. Defects in the surface coating had much effect on the progress of deterioration. The thickness of the surface coating and the presence of organic zinc primer also affected the deterioration rate. These results led to formulation of deterioration models of coated steel in a marine environment.

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Fast evaluation method for seismic maximum displacement response from acceleration response is constructed. The method is based on random vibration theory, and structural displacement and ground velocity, which are known to be related to structural damage and seismic intensity, are estimated. First, statistical relationship between response acceleration and response displacement is derived using random vibration theory. Then, the relationship is extended to the case that ground motion is measured in addition. The proposed method is applied to three cases: i) unknown ground motion; ii) known ground motion; and iii) known ground motion model with unknown parameters. Accuracy of the method is evaluated through numerical simulation, and its applicability is discussed.

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Aiming at lengthening the composite I-girder bridges utilizing high strength steels, positive bending tests of a composite I-girder using high strength steels were conducted. Then the failure mode and the bending resistance were investigated. After that, FE-analyses were carried out and the analytical results were verified on the basis of comparison with the test results. Moreover, based on the test results and the analytical results on parameters of steel strength and concrete strength, bending resistance reduction equations to premature crushing of the concrete deck were proposed, and the characteristics of bending resistance to composite I-girders using high strength steels allowing for yielding were clarified.

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In this paper, we develop a FEM-based method for the analysis of discrete crack growth in quasi-brittle materials, and apply it to a numerical study on the fracture behavior of concrete under mixed-mode loading. The method is based on the discrete crack model for representing the generation and propagation of fractured surfaces in conjunction with the cohesive crack model for modeling the quasi-brittle softening behavior. Also, arbitrary discontinuities are realized by a mesh-realignment technique. After formulating the problem with the cohesive crack model and presenting the techniques for representing arbitrarily evolving discontinuities, we demonstrate the capability of mesh-size independency and the applicability to deterioration problems of heterogeneous solids due to cracking. Finally, the fracture behavior of concrete is numerically studied by performing a benchmark test characterized by mixed-mode fracture, which is called Nooru-Mohamed Test.

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In order to estimate spectral site effect that is essential to prediction of strong motion for local government sites, we examined a relationship between site effect and amplification factor for PGA and JMA seismic intensity obtained at local government sites. A substitute for amplification factor for PGV was evaluated from amplification factor for PGA and JMA seismic intensity. Amplification factors for indices of earthquake ground motion at each observation site were evaluated and relationship between amplification factor and site effect was examined, these have a clear correlation. We proposed a formula in terms of amplification factor for PGA and JMA seismic intensity and clarified that the proposed method can precisely evaluate the site effect. The proposed method make it possible to evaluate the site effect of local government sites that is difficult to obtain the ground motion records and to evaluate the site effect more densely compared with that in the past.

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In the IIW Fatigue Design Recommendations, the fatigue strength evaluation method using effective notch stress has been specified in addition to the one using nominal stress and hot spot stress. Fatigue cracks are prone to occur from weld roots in load carrying type of cruciform welded joints, and fatigue crack propagation analysis is effective to evaluate fatigue strength of those joints. In this study, the fatigue strength obtained by effective notch stress conception is compared with one by fatigue crack propagation analysis, and applicability of effective notch stress conception to fatigue strength evaluation for cruciform welded joints failing from weld root has been discussed.

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Seismic performance of two interlocking spiral columns and two rectangular columns with cross ties is investigated based on the shake table test and fiber element analysis. The columns are designed based on the requirements of Japan Road Association and Caltrans criteria. Based on the shake table experiment, it is found that both types column performed satisfactorily for the design ground motion. Under the stronger than code specified ground motions, damage was slightly more significant in the rectangular columns than the interlocking spiral columns. However the moment capacities and response displacement are close between the 2 types of column.

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In this paper, we study the size effect of the macroscopic mechanical behavior of quasi-brittle materials such as concrete and mortar by applying the method of multi-scale analysis to take into account the generation and propagation of micro-cracks. For micro-scale analyses, the cohesive crack model is used to characterize the quasi-brittle softening behavior in conjunction with the discrete crack model for representing the generation and propagation of microscopic fractured surfaces. After reviewing the two-scale boundary value problems based on the homogenization method and the modeling of quasi-brittle fracture in micro-scale, we perform two numerical experiments to reveal the predominant factor of the size effect and to clarify its mechanism. One is for a comparative study to evaluate the effect of the amount of micro-crack formation on the macroscopic fracture energy. The other is to point out the importance of distinguishing between the microscopic size effect due to the micro-scale heterogeneity and the macroscopic size effect as energy balance in the overall structure.

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In the existing standard XFEM, decrement in accuracy of the numerical solution is caused by ‘blending elements (BE)’, whose nodes are partially enriched. In this paper, a modified formulation of XFEM is proposed by using the concept of approximation of PUFEM which assures the approximate accuracy in the entire analytical domain in order to solve the BE problem in the standard XFEM. The reformulated XFEM is applied to two dimensional linear fracture mechanics. The results obtained by the proposed XFEM using a basic numerical model are better than those obtained by the standard XFEM. Therefore, the proposed formulation is found to be effective to improve the versatility of the XFEM.

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This paper develops a model of finger expansion joints for seismic analysis of bridges. Expansion joints have been regarded as a minor structural component and they were disregarded in the dynamic response analysis of bridges. However expansion joints are extremely important structural component for controlling the seismic response of bridges. Two models are proposed in this paper. One is the model in which an expansion joint transfers only a small friction force after failure, and the other is the model in which rock of failed expansion joint results in transfer of a large lateral force. Dynamic response analysis which includes the proposed model shows that the effect of expansion joints is very important in evaluating bridge response, in particular comlumn plastic deformation at the plastic hinge and residual drift.

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Many existing infrastructures constructed prior to 1980 in Japan were designed for a particular seismic load which is smaller than the Level 2 ground motion caused by the maximum considered earthquake (MCE). Those existing structures must be retrofitted to comply with the seismic requirement for the level 2 ground motion to be newly designated after 1995 Hyogoken-Nanbu earthquake. For such pile-supported structures, a new seismic retrofitting approach is proposed by introducing additional reinforing piles. The effectiveness for this approach will be discussed based on the seismic performance-based design method.

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In this study, the influence of stress ratios on the fatigue strength of A6005C-T5 aluminum alloy and its friction stir welded joints is investigated based on the results of fatigue tests. With the increase in stress ratios, the minus slope in S-N curves increases and the common logarithm of fatigue resistances decreases linearly. The influence of stress ratios on the fatigue limit is considered by the Sonderberg line in the fatigue limit diagram for both of the parent material and the friction stir welded joints.

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