This study examines the relationship between shear force and horizontal relative displacement of L-shape shear connector by means of beam type test method. An equation for maximum shear force of the specimen which takes into account the effects of size of the shear connector and the concrete strength was proposed. It was found that shear force-horizontal relative displacement relationship can be represented by a unique enveloped curve by normalizing shear force by maximum shear force and horizontal relative displacement by the height of the shear connector. The predicted maximum shear forces and shear force-horizontal relative displacement relationships were found to agree with the experimental results.

View full abstract

  This paper describes static tests and numerical simulations of radial gates under hydrostatic and hydrodynamic loads resulting from strong earthquakes. The tests were conducted using 1/4 scale models and revealed that failure modes are weak axis buckling of the strut arms. The result of the tests and the simulations were summarized as an ultimate strength evaluation method focused on the buckling of the strut arms. The method includes evaluation procedures, key points and accuracy, which are classified into three categories: design strength of compressive buckling members, finite element elastoplastic analyses and model loading tests.

View full abstract

  In the authors' previous study, to investigate the corrosion behavior for the steel members in boundary with concrete, accelerated exposure tests were carried out on the model specimens. In addition, the method of numerical simulations using referential spatial statistics was proposed to predict the time-dependent corroded surfaces corresponding to the service period in structures. Moreover, fatigue tests were carried out to investigate the fatigue behavior of corroded members. In this research, FE stress analyses were also performed to clarify the stress concentration factor at the various conditions of the corroded surface. From the experimental and analytical results, quantitative evaluation and prediction methods for time-dependent stress concentration factor and fatigue life of the corroded members were proposed.

View full abstract

  This paper proposes a new analysis method for a stochastic model of non-linear continuum, in order to predict surface fault behavior. Compared with Monte-Carlo simulation, the proposed method is capable of carrying out the numerical analysis of the stochastic model more efficiently. It is shown that the simulation that uses the proposed method reproduces the formation of Riedel shears for a lateral problem. The convergence of the numerical solution is examined, and the validity of the proposed method is discussed

View full abstract

  The effect of steel strength used for specimens, martensite transformation start (Ms) temperature of weld metals, and applied force to specimens after welding to residual stress is examined with joint specimens. FEM analysis, X-ray diffraction residual stress measurement, and loading test were conducted to investigate the basic behavior of residual stress condition, which is formed by residual stress controlling fatigue improvement methods. It is confirmed that Ms 250°C welding material forms large compression stress, but also Ms 350°C welding material can form compression stress. And the residual stress condition formed by low temperature transformation electronode near weld toe is not so changed even by nominal 130MPa applied force.

View full abstract

  The concepts of the degrees of indeterminacy and instability, which are the important mechanical properties of frame structure, are described from the general point of view. Each member is assumed to be totally rigid but has the deformable ends to calculate compression, shear and bending algebraically and hence the symmetrical relationship between the equations of equilibrium and compatibility appears without using the differentials of deformation. It is interesting to find that the unique equation is derived among the numbers of member force, the degree of freedom, the degree of indeterminacy and the degree of instability. Particularly it is remarked that the geometrical configuration of frame should be considered to count the the degrees of indeterminacy and instability as well.

View full abstract

  Slope failure occurred in an embankment of the Tomei expressway during the 2009 Suruga Bay Earthquake. Therefore, evaluation at this site with high resolution of the strong seismic motion is very important to clarify the landslide mechanism. In this study, seismic waveform at this site was estimated based on empirical site amplification and phase effects. The estimated seismic waveform is consistent with the behavior of tombstone nearby the site.

View full abstract

  This study evaluates the effectiveness of fiber sheet reinforcement on the explosive-resistant performance of concrete plates. Carbon fiber sheets or aramid fiber sheets have been employed to reinforce concrete plates. Explosion tests have been conducted to examine failure modes of concrete plates subjected to contact explosion, and formulae proposed by McVay and Morishita et al. have been applied to estimate these failure modes taken in the tests. To examine the reinforcing effect by fiber sheets on the local damage and fragmentation of concrete plates, contact explosion tests have been conducted. The local damage of concrete plates reinforced by carbon or aramid fiber sheets have been extremely reduced as compared with that of concrete plates without fiber sheet reinforcement. These fiber sheets are also effective to prevented concrete plates from fragmentation.

View full abstract

  Accuracy of the approximate differentiation in the SPH method and the MPS method is discussed, and we show that accuracy decreasing on a boundary of analytical area in SPH method is due to the original approximate differentiation formula. In order to solve the accuracy problem of the traditional particle methods, in this paper, we propose the multidimensional moving least squares method with constraint conditions. The proposed method has physically meaningful unknown parameters, for example rotations, strains and curvatures. Therefore, by implementing this method into particle methods, we can directly obtain the physical values as particle values. Through some numerical examples, we directly show an accuracy problem of the traditional particle methods and the effectiveness of the proposed method.

View full abstract

  Monte Carlo simulation is conducted in order to study the traffic live load for a cable-stayed bridge in an urban expressway. A probabilistic model of the traffic live load is developed by the traffic survey data. The study shows that the difference between the simulation and the conventional design method results from the differnce between the dominant and opposite influence line area. A new design traffic live load is proposed from this study. It turns out that the proposed design metod is more reasonable than the conventional one from the comparison of the safety index among structural members.

View full abstract

  The weathering steel has a unique property of preventing rust by rust, and using unpainted weathering steel is important to reduce the life cycle cost of infrastructure. The following condition for unpainted weathering steel should be satised to prevent layer-like detachable rust on the surface of the steel : maximum amount of airborne salts density is less than 0.05mdd (mg/dm²/day) between girders. However a state of corrosion is different in the part of the bridge. Furthermore airborne salt density between girders cannot obtained by observation until completion of bridge. Accordingly, evaluation for quantity of airborne salt by numerical simulation is needed at each part of the bridge. This paper discusses the estimation of airborne salt around section of the bridge by comparison between numerical result and observation of airborne salt near the girder.

View full abstract

  In this paper, a rubbing damper device, generating frictional force in proportion to absolute rubbing displacement, is proposed in order to aid passive vibration control of frame structures. The proposed rubbing damper device is composed of a rubbing pair of concave bar and convex bar which is connected to a supported beam (which is usually fixed to object) by U-type leaf springs. Two parallel ascent interfaces and a descent interface of the rubbing pair increase assembled height of the rubbing pair in proportion to the absolute rubbing displacement of the rubbing damper device respectively. The U-type leaf springs are compressed by the rubbing pair and the supported beam, and apply compression force to the rubbing pair. Therefore, the rubbing damper device generates frictional force as damping force on the two parallel ascent interfaces or the desent interface due to the above compression force. Firstly, a basic function of the rubbing damper device and its mechanical principle are described theoretically. Then force versus displacement hysteretic curves of the rubbing damper device and a simple rigid test frame with the rubbing damper device are obtained. Finally, the hysteretic curves of the rubbing damper device and the simple rigid test frame are investigated experimentally.

View full abstract

  The evaluation of strong seismic motions in high resolution is very important to clarify the mechanism of earthquake damage. In this study, seismic waveform evaluation process at numerous sites along line structure based on empirical site amplification and phase effects was proposed. The proposed method was applied to the slope failure sites of the Noto Tollroad in the 2007 Noto Hanto Earthquake. And, as an application of the proposed method, fragility curves were generated based on the estimated waveforms. Thus, the proposed method is useful in the detailed study of earthquake damages.

View full abstract

  CFT columns used as bridge piers have high strength and ductility, compared with hollow columns. However, up to the present, no sufficient research has been conducted on an accurate analysis of concrete-filled stiffened rectangular steel columns under cyclic load. Herein, based on ABAQUS, an accurate and numerically stable 3-D FE model is proposed with considering the geometric and material nonlinearity as well as the interface action between in-filled concrete and steel tube. The validity of the computed hysteretic behavior of CFT columns is confirmed by existing experimental results. Based on the proposed FE model, the local buckling restraining effect, the distribution of confining pressure from steel tube, the enhancement in axial compressive strength of in-filled concrete and the metal fracture of steel tube are discussed in detail.

View full abstract

  The weld repair requires no additional member such as splice plates, therefore it will be more cost efficient and shorten the work period comparing with the conventional bolted repair method. However, the weld repair has possibility to introduce weld defects or residual deformation which may reduce the fatigue strength of the repaired joints. Besides, even though fatigue cracked joints are restored to the initial condition with sound weld repairs, the fatigue crack will reoccur in the repaired joint, because the fatigue strength of cracked joints is low in most of the cases.
  In this study, a new welding material named low temperature transformation (LTT) welding material, which enables to introduce compressive residual stress in the vicinity of the weld bead and reduce weld deformation, was applied to the weld repair. The applicability of the LTT welding material to the weld repair was investigated by the fatigue tests with compact tension specimens and a steel girder specimen.

View full abstract

  In this paper, we propose the hierarchical 3D-shell elements that regulate the same displacement field as several shear deformation theory in the displacement function of a hierarchical solid element. These elements are identical with the hierarchical plane-shell elements having the in-plane and bending stiffnesses, but those have the same three-dimensional shape as the hierarchical solid elements. Therefore, there is no modeling contradiction such that the middle-surface of the elements combines with a solid element in the case of plate/shell elements, and application of these elements to plates with variable thickness is easy. By applying the Mindlin and Reissner elements based on first-order shear deformation theory and the high-order elements based on high-order shear deformation theory to thick plate analysis, the accuracy and applicability of these elements are demonstrated.

View full abstract

  The seismic intensity is announced by Japan Meteorological Agency based on the value of the instrumental seismic intensity. The instrumental seismic intensity is determined by using a special filter, whose amplification characteristics are similar to those of the frequency response function determining the relative velocity response of a single-degree-of-freedom (SDOF) system subjected to earthquake ground motion. Accordingly, new seismic intensity can be proposed on the basis of the velocity response of a SDOF system under seismic excitation. In the present study, this new seismic intensity is called by “velocity response seismic intensity” (I_VR).
  The correspondence between the velocity response seismic intensity and the instrumental seismic intensity was recognized by comparing two kinds of seismic intensity calculated from 515 strong ground motion records of the seismographs of K-NET and KiK-net by National Research Institute for Earth Science and Disaster Prevention.
  By changing the natural frequency f_n (originally 0.7 Hz) of a SDOF system, the short-period velocity response seismic intensity I_VRS (f_n=3.333 Hz) and the long-period velocity response seismic intensity I_VRL (f_n=0.1666 Hz) can be defined to know the characteristics of the strong earthquake ground motion in other frequency ranges. It was found that the befalling of earthquake-induced sediment disasters has a relation to the value of I_VRS. The I_VRL value was found to relate to the occurrence of the earthquake damage of oil storage tanks.

View full abstract

  Measurements of corrosion pits of galvanized bridge wires were conducted. It is found that severer corrosion produces deeper pits in more condenced areas. Fatigue tests with three different artificial pit shapes were then performed. Wires with a round pit shape have higher fatigue strength, and the fatigue strength of the wires with a triangle pit shape is lower than that with a round shape. The wires with nothched triangles have the lowest fatigue strength because of high stress concentration. The fatigue tests results with artificial pits corresponded to those of actual corroded wires, which shows that the main factor of reduction of fatigue strength is the surface roughness caused by corrosion.

View full abstract

  In Japan, most of the riveted girders in steel railway bridges are ageing more than 70 years. In these bridges a lot of loosed rivets are found and it becomes a problem in maintenance of steel railway bridges. In these cases to replace the loosed rivets with high-strength bolts is generally adopted. Because the corroded plates have not smooth surface to contact with washer adequately, however, there is a possibility that the repaired joint cannot secure to have expected performance. In this paper, high-strength bolts with resin layer under washer replaced from rivet were developed and creep tests were carried out to investigate the decrement of axial force of high-strength bolt. By combining steel shot balls with the resin, an expected performance was achieved.

View full abstract

  Local strong wind phenomena are becoming major concerns in risk management of transportation. Tornado detection by mobile platform sensing is studied for reduction of damage by emergent operational management, such as emergent braking. Rankine vortex is employed for theoretical modelling of tornados, and prediction method for maximum wind velocity and its occurrence time is constructed based on mathematical analysis of relative position of the mobile platform and tornado center. The method is also applied to measured wind velocity data during tornado, and its applicability is investigated.

View full abstract

  For the CFRP bonded to butted steel plates, higher stiffness of CFRP plates is required to reduce the shear stress in adhesive at butt end. However, as the stiffness of CFRP plates becomes high, shear stress in adhesive at the ends of CFRP plates becomes also high. Therefore, it can be presumed that the shear stresses in adhesive at butt end as well as at CFRP plate ends become small by bonding CFRP plates with stepped ends. In this study, CFRP step-bonded to butted steel plates is theoretically analysed. Then, the conditions to minimize the shear stress in adhesive for CFRP step-bonded to butted steel plates are given.

View full abstract