This paper presents a numerical method, the BF-spline Ritz method, for bending analysis of rectangular Mindlin plates with clamped and free edges. The proposed method utilizes admissible functions comprising the B-spline functions multiplied by a boundary function to define the Ritz trial function for the transverse displacement and rotations of the Mindlin plates. The geometric boundary conditions of the plate at edges are automatically satisfied using boundary functions. To demonstrate the validity and accuracy of the BF-spline Ritz method, several examples are solved, and results are compared with those obtained by analytical and other numerical methods. Good convergence and accuracy are obtained by the present method. The effects of Poisson’s ratio, thickness-width ratio and aspect on the distributions of deflections, bending moments and shear forces of rectangular Mindlin plates due to distributed load are shown. The results obtained are to serve as benchmark data for future development of new numerical methods.
In Japan the use of corrugated steel webs is increasing in the construction of composite girder bridges. The corrugated plates have higher rigidity to shear forces, while have lower rigidity to axial forces and bending. Because of these, it is possible to design as a slender web without transverse and horizontal stiffeners. The paper presents the test results using four different trapezoidal corrugation configurations including a flat web. Load deformation curves and strain distributions were investigated. And the test results were compared with the numerical analysis using the finite-element program. Two failure modes of local and global shear buckling were observed depending on the depth of corrugations and the ultimate shear strength increased to the ratios of 1.8 to 2.0 for the flat web girder. Assessments of the applicability of existing design formulas for the shear buckling strength is given based on the test data.
High performance material is significant for improvement in safety, economy and life of structures, as compared with current ones. This paper focuses high tensile strength and corrosion resistance on high performance steels as the ultra steel and stainless steels, which are SUS304 and SUS304N2, respectively. At first, stress-strain relations of the materials are clarified by means of a coupon test. Secondarily, constitutive equations and their parameters are proposed, and applicability of the equations is demonstrated. Finally, proposed constitutive equations and parameters are shown to be adequate for the high performance steels as well as mild steel.
Different from Point by Point measurement technique, 3-D photogrammetry technique enables to monitor the shape and dimension measured-objects in non-contact, remotely and globally. In order to provide a rational maintenance strategy, it is important to assess current structural properties of existing structures due to long-term structural degradation, static and dynamic loads. In this paper, the applications of 3-D photogrammetry in capturing 3-D spatial coordinate of shape-complicated existing historical structures such as the Nagasaki Peace Praying Statue etc. are reported. Then, captured spatial data were converted into surface data and solid data to perform 3-D finite elements for dynamic structural analyses. The structural strengtheninng efficiency was verified through free vibration characteristics evaluation.
In Japan, it is planned to dispose high-level radioactive waste (HLW) and transuranic (TRU) waste in a stable rock mass. Since the radioactive level of those wastes is extremely high and their half-life period is exceedingly long, it is necessary to ensure that residual radioactive substances are kept from reaching the biosphere after many thousands of years, and to clarify the mechanism of rock behaviors as well. The mechanical and hydraulic properties of rock mass have strong correlations respectively. In this study, an experimental approach with associated with the coupling behaviors of water flow and deformation is conducted with the use of an artificial specimen so as to seize the coupling mechanism of the behaviors. As for a method to seize the behaviors, “matching method” which is a sort of a pattern-matching scheme in the field of image data processing is employed. Finally, the coupling mechanism of the specimen is discussed.
This paper presents an investigation of the experimental study on structural behaviors of connection, especially diaphragm connection and connection panel, between concrete-filled square shaped steel beam and concrete-filled square tubular steel reinforced column subjected to incremental loading. The analytical results are verified through comparison with results of finite element analysis and a experiment. Moreover, it is indicated that these dimensional analyses are available for evaluation of these type of connections..
In recent years, the crack damage with which fatigue is considered to be the cause by beam-to-column connection of steel pier was checked, and taking the influence of fatigue into consideration was specified to the design. However, there is not a rule of concrete design technique in beam-to-column connection of steel pier and the present conditions grasp a stress property by an experiment and FEM analysis and fatigue durability is secured. This study proposes the constant shear flow panel analysis as the practical analysis technique in a fatigue design of beam-to-column connection of steel pier. In this study, compared test calculation results in various beam-to-column connection s of this analysis by FEM analysis, and confirmed plasticity of this analysis by comparison with stress measurements in established structures. As a result of examination, this analysis technique was modeling more temporarily than FEM analysis and confirmed what evaluation of stress in the beam-to-column connection could do with precision to be higher than a constant standard.
The dynamic response of railway bridges is a problem of the resonant response of girders that occurs because bridges are excited at a constant period by running trains. In general, it is called “the speed effect of multiple-axle moving loads.” In this study, numerical analysis was performed to examine 8 continuous bridges of various structural types with different span lengths. A revision of the railway design standard was proposed as a conclusion of this study, to cope with the speed-up of trains, based on the results of the above-mentioned numerical analysis.
Many floating tracks have been used for only low-speed trains as vibration reduction system. A study was carried out on dynamic response and running quality, using various floating tracks for high-speed train. A simulation program, DIASTARS was used in this analysis. In this program, the Shinkansen vehicle is three-dimensionally modeled as having a body, two trucks, and four wheelsets connected to each other by spring and dampers. The floating tracks were modeled by three dimensional finite element methods. In this study, the wheel load variations and vehicle body accelerations were investigated by dynamic interaction analysis between vehicle and track. The parameter was the train speed and the stiffness to support track.
The introduction of performance based design concept into the design specification for the highway bridges has just being prepared. The current design codes for plate girders are expressed by the restricted type specification, so they don’t fit to the performance based design concept. Therefore it is desired that new design provisions on plate girders are defined as allowing direct estimation of limit state. In this report, several technical problems are discussed on the translation to the performance based design, that is, the course for setting of current provisions on plate girders design, a proposal for strength evaluation of plate girders, the effectiveness of proposed design method, future trend in desirable form as performance based design, etc.
Hybrid girders have a potential for rational and economical design for steel girders by the use of low strength materials for their web plates. However it seems that the development of tension field action in a web panel under shear loading has not been clearly understood. In this paper, a total of ten hybrid girders were tested experimentally and analytically under static loading with various combinations of moment and shear. Development of tension field action and the collapse mechanism for web panels under shear loading were investigated in order to gain the necessary information to prepare for the design specification. Based on the test results, equations for ultimate shear strength for hybrid girders were proposed.
A plactical design method by eigenvalue buckling analysis of frame model with thin-walled members is proposed for lateral-torsional buckling of plate girders with I-section. First, elastic buckling moment is given by the eigenvalue buckling analysis. Then, the bending strength is figured out from the elastic buckling moment. The accuracy of the eigenvalue buckling analysis is confirmed by FEM analysis with shell members. The standard load carrying given by the design method obtains the reliability by comparison with obvious experiments and analyses.
This paper studies the elasto-plastic collapse behavior of steel web plates. Fourteen web plates of the width-thickness ratio 35 to 154 are tested up to failure under the condition of cyclic shearing force with variable strain rate. Test results discuss the variation of shearing buckling wave and location of crack due to the plate slenderness and static and dynamic loading patterns. The stress-strain response by the loading with piecewise constant strain rates, unloading and relaxation demonstrates the relationship between the viscoplastic shearing overstress and strain rate.
Since large resultant forces and stress concentration can take place, the design of beam-to-column connections is important for a steel moment frame. To date, in practice, the analytical study of stress concentration due to shear lag has been a mainstay for the design of these connections exclusively. However, the validity of such a design approach in large earthquake is not understood well. In recent years, many existing connections have been found to suffer from fatigue cracks and the reinforcement by fillets has been proposed. In the present study, the effectiveness of the fillets is studied for the reinforcement of a beam-to-column connection under ordinary and large seismic loadings.
In this paper, extensions of application of newly developed scaled boundary finite element method to branched crack problems are presented. In this method, stress singularity at a crack tip can be derived analytically from its stress solution. Using SBFEM’s semi-analytical properties authors’ have presented a direct and simple SBFEM formulation to compute fracture parameters. Stress intensity factors of branched crack are computed extending the SBFEM formulation proposed by authors. Numerical examples for a range of crack sizes are analysed to examine the effectiveness of the proposed method. In addition, the application of SBFEM is extended to crack propagation simulation in 2D linear elastic problem under mixed mode condition. Since only the domain boundary is required to discretize like in boundary element method and also it has its own unique property that the side-face boundaries and near crack tip are not necessary to discretize, the burdensome remeshing required in FEM and BEM is minimized. A mixed mode problem for crack propagation analysis is simulated. The computed SIFs and crack propagation trajectories are in remarkable agreement with available values in the literatures.
In recent years, many fatigue cracks are found near welding area on orthotropic steel deck plates with trapezoidal stiffeners. In order to evaluate the life of the structure and determine the effective repairing methods, it is essential to predict the accurate crack path and estimate the crack-propagation speed. In the crack propagation of steel plate deck that penetrates the steel plate deck, there is an assumption that welding residual stress has a strong influence. In this paper, we present the simularion of fatigue crack in the deck plates with X-FEM considering the effect of residual stress, and it was shown that the simulation coincide with experiment.
In this study consists of the following two topics, one is a basic consideration on a structure of the decision making for a personal intention problems, and the other is classified to regard to the consciousness structure in general agreement formation for infrastructures construction problems. In the former study, the personal decision making scheme which have three importance pieces of concept “deciding”, “determine” and “decide”. In the latter one, in Western society, it is important to the independent for the decision making system in agreement formation. On the other hand, in the Japanese society, the continuation nature thinks are importance although it is decided as the one that decides. This paper is proposed to decide the social decision-making using from Cumulative Prospect Theory based on human impression.
Deterioration of concrete structure has been drawing a greater social attention and severe chloride damage has been observed in seaside area. In this paper the method to seek the optimum repairing level of concrete structure is proposed by evaluating the seismic capacity of concrete structure deteriorated by chloride induced damage. Since deterioration parameters and seismic parameters involve various uncertain factors, the proposed method is defined the parameters based on reliability theory. Four parameters concerning with chloride induced damage are chosen as the statistical parameter. Four parameters are the diffusion coefficient of chloride ion, thickness of cover, the limit chloride ion density of corrosion and the limit corrosion rate of surface cracking. The optimum repairing level is obtained by minimizing the total expected cost in life span.
Buckling failure of wind turbines in typhoon prone-areas is an important issue that needs to be addressed by both designers and wind farm owners. In this paper the authors propose a technical - financial approach to obtain an acceptable target probability of buckling failure that satisfies a financial criterion acceptable to the owner. To obtain the probability of buckling failure reliability analysis is used. On the other hand the cash flow of the wind farm is analyzed using stochastic capital budgeting. The criteria used to assess the cash flow values are the net present value and the internal rate of return methods.
One of most effective and traditional ways for the economic design of steel plate girders is to vary their cross-sectional dimensions along their length, in accordance to their bending moment diagram. The design guideline was published in 2000. However, in spite of the existence of practical design rules to determine the number of cross-sections and the cross-section variation points, the final decision still relies on the experience and good sense of the bridge designer. In this paper, we show the outlines of determination system that, by applying genetic algorithms, not only determines the most economic resistance moment and their respective transition points, but also gives an evaluation of the bending moment diagram, without having to perform the conventional structural analysis.
In the process of the radial basis function network (abbreviated as RBFN), two design points are added in each iteration to update the approximated surface, one is optimum design point obtained by former optimization step, and the other is the sparse design point to increase the global precision of approximated constraints surface. Naturally, it is desirable that the added design point is close to the active constraints surface. Without newly performing the structural analysis, it is difficult to find if the added design point is close or not. In this study, the support vector machine (abbreviated as SVM in the following) is tried to apply to discriminate whether the design point is close to the surface or not. SVM is currently attracting attention as a pattern classification procedure with a learning function. This SVM has excellent cognitive abilities and is currently applied in a variety of engineering fields. SVM is also characterized by the ease in which it obtains the distance from the discriminant plane. In this study, the possibility of SVM as the support system of constraint approximation in the process of structural optimization is studied with several numerical simple examples.
A questionnaire focusing on finding out the acceptable damage level of ordinary citizens against earthquake hazards is carried out. One of the distinguished features of this questionnaire was to discover the acceptable level of infrastructures in comparison to private apartment buildings. It was also attempted to find out the acceptable damage rate to the structures by asking return period for damages in indirect and manipulative ways. Major findings of this study are (1) the acceptable annual rate for large earthquake damage seems to lie between 10 to -3 to -5, (2) most of the citizens consider infrastructures should be more seismic resistant than privately owed apartment buildings in concept, however if the same question is asked in more specific ways, this order can be reversed.
The present paper deals with the evaluation formula for the punching shear load-carrying capacity of RC slabs in the highway bridge by applying the ultimate limit state design method. The testing specimens of three types were prepared on the basis of the Specifications for Highway Bridges of Japan. The theoretical model and the load-carrying capacity equation for the punching shear have been determined due to the failure modes and the strains detected on the rebars ; so, the estimated values by the proposed equation considering the ultimate limit state design method agreed well to the experimental results. Thus, the design live load can be obtained by application of the material and member factors to the estimated punching shear load-carrying capacity.
A statistical analysis on a database of pile loading test is carried out to obtain vertical spring constant for serviceability limit state design. A database of 133 vertical pile loading tests carried out in different locations in Japan is first screened for good quality tests including the ultimate load conditions. The load-displacement curves of the database after screening are then mathematically fitted to Weibull curves from which the vertical spring constant Kv0.33 is calculated (Kv0.33 is Kv at the ratio of load to ultimate load of 0.33). The best model for estimation of Kv0.33 based on the available soil and pile parameters that are regarded as significant explanatory variables is finally chosen with the uncertainties of the model.
Performance based design has been thought to be rational because it enables engineers to use variety of design and construction methods for each structure. Inelastic design considering moment redistribution is one of such design methods, and has currently been included in design specification in the United State. In this paper, the mechanism of moment redistribution is illustrated, and a design example using inelastic design procedure is presented to demonstrate how the moment redistribution is included in the design. In addition, a simple equation to calculate the inelastic rotation at the intermediate support in a two-span continuous girder due to factored load and a procedure to check the safety of rotational capacity of the section are proposed.
This paper presents a new determination method of partial safety factors for reliability design method. A structure designed by the partial safety factors obtained from FOSM method could not be satisfied with the target reliability index. Our proposal method is to prepare several partial safety factors around the ones obtained from FOSM method in advance. We check the usability of this proposal method by designing a steel pier to withstand local buckling. As a result, it is confirmed that our proposal method can provide the partial safety factors which can improve safety efficiency and economic efficiency.
The authors tried to propose a new methodology of bridge design in this paper. One of the authors had reported in the previous papers that engineering understanding of bridges could be modeled with cognitive prototypes, which were thought to be bas es of inspiration for bridge design, so that he thought that adding a new idea to a prototype of an engineer might guide him/her to a new design. Concepts of stability in the fields of bridge engineering, architecture, aeronautical engineering, naval architecture, railroad engineering, robot engineering and bioengineering were studied. A pair of the concept of dynamic and static stability in the fields of aeronautical engineering and naval architecture was chosen for adapting to bridge engineering. Based on the concept, a new methodology of bridge design was proposed, and a conceptual design for a new bridge was shown.
This study is to specify cognitive prototypes of bridges of bridge engineers using a proposed methodology based on “a Cognitive Model of a Sense of Dynamism of a Structure’s Form” which one of the authors proposed. The methodology consists of an optical psychological experiment, which was reorganaized from the previous study, and analyses with logical charts, which shows relations between obtained responses and a method to be applyed. The authors carried out psychological experiments on twenty-nine bridge engineers, who were chosen as subfects because they were supposed to have some cognitive prototypes of bridges. As a result, the authors specified several different types of prototypes for arch-type bridges.
In this study, the validity of the damage identification technique that uses Fourier amplitude ratios due to unknown excitation force was confirmed based on the vibration testing using a real bridge. The technique is based on the fact that the ratio of Fourier amplitudes at two points when they are measured simultaneously is constant regardless of the amplitude of the excitation force. The bridge was excited using a micro shaker and the excitation force is clearly known, but we did not use it as input data for the technique. Damage was modeled as a reduction in stiffness and created by reducing the section area of diagonal members of the bridge. It was shown that the damaged elements were correctly identified using the technique.
The use of horizontally curved steel multi I-girder bridges is dramatically increasing for highway bridges and interchanges during the past three decades. However, dynamic behavior of these bridges is more sophisticated and less understood than that of straight bridges. In addition, this bridge type has very small torsional stiffness so it can be easy to vibrate by external dynamic loadings. By these reasons, a series of horizontally curved steel twin I-girder bridges are carried out in detail by using FEM in this study not only to learn about the free vibration characteristics but also to improve these characteristics of this bridge type. Through these analyses, several stiffening structures are recommended.
Described in this paper are an observation and analytical verification on seismic responses of a long-span cantilever truss bridge with 980m-long. Some earthquake records have been obtained from this bridge and dynamic analyses were carried out in order to verify the natural frequencies and damping properties. It was found that natural frequencies of analyses using the three-dimensional model are good agreement with those of observations. However it can be noted the damping ratio which is normally applied in analyses may give small displacement response for the relatively long period mode. Therefore we recommend that 1% of damping ratio should be applied for such the mode. Moreover it was confirmed that the friction between I-bar and a pin at hinge portions of cantilever bridge affect the bridge response in the longitudinal direction.
The generating factor of vibration, which occurred at the circumferential environment of a highway bridge, is the impact force produced by vehicles running the level difference of expansion joint. Such vibration has affected running stability, noise, infrasound and ground vibration. This study thought that reducing the impact force, at the time when vehicles are running the level difference of expansion joint, reduced the ground vibration. In the general case of the straight bridge, right and left rear wheels run on the expansion joint at the same time. However, in the skew bridge, rear wheel of either side do not run on the expansion joint at the same time. Therefore, the half impact force acting on the skew bridge is reduced. Then, the analytical models of extended deck bridges with various skew (80, 70 and 60 degrees) were made. The changes of the sound characteristics around the bridge were estimated by the dynamic response analysis due to running vehicles on the each analytical bridge model.
A finite element analysis is developed for outdoor sound propagation with structural objects, terrains or spatial variations of air temperature. Infinite elements are applied on external boundaries of computational domains, and a conjugate gradient method based on the Element-by-Element technique is implemented to solve the finite element equation. It was found that the computation results using this FEM tool have a good agreement with those of BEM in the computation of various types of noise barrier.
The objective of this paper is how to control waveforms by means of all pass functions. Causal time functions such as earthquake records are factorized into minimum phase shift (MPS) and all pass (AP) functions, which is called factorization. This concept is applied to impulse response of SDOF to investigate effects of AP phases when they are parametrically changed. With linear AP phase shifts, waveforms of the response are unchanged but the time delays appear. With nonlinear AP phase shifts, waveforms of the response show irregular attenuation, and their maximum amplitudes are smaller than the original ones.
This study proposes a method of generating acceleration time series that fit a design response spectrum. Earthquake ground motions are modeled with a power spectrum density function and an envelope function to compute responce spectrum based on the Vanmarcke’s approach. A set of model parameters that describes the power spectrum is directly identified so that the computed response spectrum fits the shape of a design (target) response spectrum. Thus, the method can generate infinite number of acceleration time series that fit the target response spectrum with just fitting process.
This paper discusses the seismic instrumentation for the strong motion observation in the free-field. A seismometer for the free-field observation is usually mounted on a concrete block whose motion deviates from that of the free-field ground since the block has a different level of stiffness and mass from the soil. Thus, the seismometer mounted on the concrete block may not correctly observe the free-field motion. We computed the concrete block / free-field motion transfer function in the frequency domain for various possible configurations of the block. The results indicate that the instrumentation on the concrete block provides reasonable free-field motion as long as the block is totally embedded and the embedment depth is less than 1 meter. If a portion of the concrete block projects above the ground surface, the portion will contribute to the rocking motion of the block, thus, the portion should be small in dimension and as light-weight as possible.
In this study, shaking table tests of full-scale gravestone models were done in order to investigate the seismic behavior and overturning mechanism of the gravestones. Full scale Japanese-type and European-type gravestones were tested, and seismic waves with seismic intensity of 6-, 6+ and 7 were used as input ground motions. Reinforced gravestones with bonding and adhesive reinforcement were also tested and their behaviors were compared with those of un-reinforced ones. Effectiveness of reinforcement measures was discussed based on the pictures and acceleration measurements.
This paper aims at proposing the method to evaluate the seismic coefficient of caisson type and sheet pile type quay walls against the level-one earthquake ground motion. The proposed method takes the frequency characteristic and the effect of duration time of earthquake ground motion into consideration. We conducted two-dimensional earthquake response analyses and showed that the proposed method well evaluates the seismic coefficients to be applied to the design of the quay walls within the displacement range of 5 to 20 cm.
This paper aims at proposing the simple estimation method of seismic reliability indices against residual deformation for quay walls. Seismic reliability index against residual deformation was evaluated by using First-order second moment method considering the variation of the shear modulus of the soil. It is necessary to conduct the two-dimensional nonlinear earthquake response analyses at least three times in order to calculate the reliability index. On the contrary, the proposed method uses only one result of the earthquake response analysis and evaluates the reliability index on the conservative side.
The 1995 Hyogoken-Nanbu Earthquake caused severe damage to civil infrastructures, including buildings, roadways, railways, subways, port facilities and so on. The ground motions observed during the Hyogoken-Nanbu Earthquake were very strong and its intensity of ground acceleration was very large in all three components that are the North-South, East-West and Up-Down components, so that the complex spatial response of structures has been reported. It is strongly recommended that the development of the reliable seismic design methodology should be made based on the full understandings of the spatial behavior of structures subjected to 3D ground motions. A simple mass-spring-dashpot model for evaluating the response of structures subjected to bidirectional ground motions was proposed, wherein the elasto-plastic stiffness was defined based on the strength interaction curve in conjunction with basic principles of the theory of plasticity. The proposed simple model was shown to be capable of accurately predicting the bidirectional response of structures.
The present paper is concerned with the proposal of a seismic performance evaluation method for steel bridges with H-section members. A shell-element numerical model that can account for buckling behavior is first created to clarify the collapse mechanisms of the members subjected to monotonic and cyclic loading. Pushover analysis employing a beam-element numerical model is then implemented to examine the ultimate strain equations, which are necessary components of the failure criterion for strain-based evaluation method. Finally, based on the findings in the analysis, a seismic performance evaluation method for H-section steel members is proposed.
The seismic response of a hybrid stress-ribbon vehicle bridge with a span-length of 400 m was numerically analyzed in the time domain. The adjusted acceleration wave record of the Hyogoken-Nanbu Earthquake was input into the model. In this model, a bilinear stress-strain curve was assumed. The findings revealed that the maximum normal stress in the upper and lower cables was in the range of the elastic region and that the maximum stress of combined bending moment and normal force in the edge girders was also in the range of elastic region except for several segments close to the abutments where the elasto-plastic stress was induced. Also, the maximum acceleration on the deck in the direction along the bridge axis was about 1.4 times larger than that of the input motion.
Dynamic analyses are carried out for Meiko Central bridge, a long-span cable-stayed bridge, by using the assumed ground motions. Both material and geometrical nonlinearity are taken into consideration. Due modeling is used for the important members that yield in the seismic analyses. The nonlinear seismic behaviors and members’ damage sequence of the cable-stayed bridge are investigated by analyses until ultimate state. It is verified that response value of Meiko Central bridge is small and safe when subjected to Tonankai earthquake, which have longer period.
It is supposed that aftershocks and foreshocks have significant effects on the seismic performance evaluation of structure. Since the damage of structure may be closely related to the earthquake input energy, it is necessary to carry out the accumulated damage assessment by means of the energy evaluation. For the reliable design of a structure, it is very important to clarify influences of accumulated damages on the nonlinear response situation due to earthquake. In this present study, by applying the target performance due to demand strength spectra with the damage index by Park and Ang, it is examined with cumulative damages which are given by aftershocks and foreshocks for the earthquake performance evaluation of the structure. It is shown that seismic performance evaluation is closely related to accumulative damage estimation due to aftershocks and foreshocks.
The pylon piers of the Tsurumi Tsubasa Bridge are octagonal, two-cell, reinforced concrete structures framed with large steel H-sections. It has been found that these steel-framed reinforced concrete structures might fail in shear under Level 2 ground motion. In order to increase the shear strength of the steel-framed reinforced concrete pier structures, the use of the carbon fiber jacketing method is currently under study. In this study, cyclic loading tests using two 1:10-scale models, one strengthened by carbon fiber jacketing and the other not strengthened are carried out. The study has enabled the determination of design values of shear capacity of a non-strengthened steel-framed reinforced concrete pier structure and has shown that shear failure of the Tsurumi Tsubasa Bridge's pylon piers under Level 2 ground motion can be prevented by carbon fiber jacketing.
There are little execution results of seismic retrofit of large-scale bridges such as arch bridge. In a deck type arch bridge very big up-lift forces for bearing supports and section forces beyond yield stresses for many members occur during an large earthquake. Therefore, an effective seismic retrofit design should be discussed to reduce dynamic response by nonlinear dynamic analysis using fiber element. For an target arch bridge of spandrel arch bridge with 214m span length, five independent retrofit countermeasures are proposed, and three effective plans from those are extracted. Furthermore these three plans are put together to make one superior plan. In evaluation of seismic safety of each member, importance of the member and mechanism of the damage are considered.
With the rapid increase of bridge spans, research on controlling earthquake-induced vibration of long-span bridges has been a problem of great concern. The concept of varying the normal force in a frictional interface is investigated to enhance the energy dissipation from a vibrating structure and improve the seismic performance of bridge structures. A semi-active optimal control algorithm is formulated to determine the controllable clamping force of a variable friction device; this algorithm uses measurements of the absolute acceleration and device relative displacements for determining the control action to ensure that the algorithm would be implementable on a physical structure. The friction device UHYDE-fbr is designed and manufactured such that the normal force in the friction interface can be influenced with air pressure chamber, hence the normal force and friction damping can be controlled. The friction device is a controllable energy dissipation device that cannot add mechanical energy to the structural system; the proposed control strategy is fail-safe in that bounded-input, bounded-output stability of the controlled structure is guaranteed. The numerical results demonstrated that the performance of the presented control design is nearly the same as that of the active control system; and that the friction device can effectively be used to control seismically excited cable-stayed bridges with multiple-support excitations.
The seismically isolated bridge is generally designed so that the seismic isolation device would absorb total energy mainly. So the pier would behave in stationary range. However, under the huge earthquake, it would be realistic to allow the pier inelastic behavior as well and to design so that both the seismic isolation device and the pier absorb the energy.This paper presents Monte Carlo simulation reliability analysis of RC isolated bridge based on results of dynamic analysis considering uncertainty of material properties of two structural members e.g. the pier and laminated rubber bearing and earthquake waves. Then, the distribution characteristics of dynamic responses of these members were discussed. Furthermore, what the primary nonlinear and the secondary nonlinear should be discussed in term of probability. According to the evaluation, we assume that yield strength of the concrete pier could be reduced.
A number of bridges suffered extensive damage during the 1995 Kobe, Japan earthquake due to premature shear failure resulted from termination of longitudinal reinforcements with insufficient development, overestimation of shear strength of concrete and insufficient amount of ties. To study failure mechanism of such piers, four 1/7 scaled cantilevered circular pier models were built and loaded. Four loading methods were used; 1) unilateral pushover loading, 2) unilateral cyclic loading, 3) bilateral cyclic loading and 4) unilateral hybrid loading. From the experimental results, it is known that piers suffered flexural shear failure under unilateral pushover and hybrid loadings while piers suffered compression shear failure under unilateral and bilateral cyclic loadings. It is also shown that the pier under bilateral loading suffered more significant damage than the pier under unilateral loading.
Wall-type reinforced concrete piers have been broadly constructed for river crossing so far because it has various advantages for designers to comply with requirements from geological restriction and river management. If the longitudinal axis of a bridge with this type of pier intersects to the direction of river flow with some skewed angle, however, the load carrying capacity against earthquake should be evaluated appropriately as a function of the skewed angle. This paper aims to study a rational procedure of experiment as well as seismic design and reinforcement method through monotonic and cyclic loading tests for wall-type piers with skewed angle. As a result, several important findings are obtained such as; the skewed angle makes the pier rigid but no improvement in energy absorption is found, the skewed angle may cause upward reaction force at the supports and the rigidity of super structure is likely to have the influence on the load carrying capacity of the pier.