The various functions of bracing in different forms of steel bridge construction are identified. The requirements of bracing designed to provide additional stability to potentially unstable main members is discussed and the two necessary characteristics of adequate strength and adequate stiffness identified. Particular attention is given to U-frame action, either in through girder decks or as a means of stabilising the support regions of continuous composite decks. For the latter the results of recent research suggest that bracing could often be omitted; a method of quantifying this requirement is presented. This leads to the concept of bracing-free bridges.

View full abstract

Scatter in fatigue life of various welded details is an important factor to be considered in fatigue design codes. The fatigue crack propagation life of two welded details, such as non-load-carrying fillet welded specimens and welded beams, is computed using fracture mechanics. Monte Carlo simulation technique is used to define the initial conditions, such as crack sizes, weld toe geometries, crack shapes, and blowhole sizes. The probability distributions of those parameters are obtained from the actual measurements. The analytical results are generally in good agreement with the experimental results. They are also compared with the allowable stresses given in the fatigue design codes.

View full abstract

Fatigue strength of welded details in long life region, for example over five million cycles, is essential for fatigue design of bridge components, because the stress ranges measured in service are often in this range. Constant amplitude fatigue tests on 200mm long gussets welded to tensile plates and tensile flange of beams and on 200mm long cover plates subjected to low stress ranges were carried out, and constant amplitude fatigue limits were evaluated. The test results on 200mm long gussets were compared with fatigue crack propagation life computed using the Monte Carlo simulation technique. The analytical results were generally in good agreement with the test results in the finite life region. However, the predicted fatigue limit using a threshold value of stress intensity factor range was lower than the runout level of test data.

View full abstract

Practical repairing methods for fatigue damage in cross bracing connections in steel girder bridges are studied experimentally. Fatigue cracks initiated in the welded joint between upper flange of longitudinal girder and transverse stiffener to which cross bracing is connected. Various repairing methods are examined and the increasing weld size with TIG dressing is proposed as one of the most suitable repairing method.

View full abstract

Fatigue behavior of fillet welded joints with a scallop under highway and railroad loading was studied. Variable amplitude stress fluctuations were generated by computer simulations of highway and railroad live loads. Fatigue failure occurred even if the equivalent stress range was less than the constant amplitude fatigue limit. Therefore, fatigue life evaluation assuming that stress ranges below the fatigue limit did no damage was unconservative. It was verified that the fatigue life under variable amplitude loading could be estimated accurately by applying the fracture mechanics approach with the linear damage rule.

View full abstract

The tangent stiffness equation for a planar straight beam to reflect the displacement dependency of loading is derived. The load stiffness matrices for water pressure and the center directed uniform distributive loading for circular members are obtained explicitly. Using the stiffness equation derived, planar buckling and post-buckling of elastic rings and arches subject to a variety of loading patterns have been examined. It is found from the computations that the displacement dependency of loadings significantly affects not only the buckling strength, but also, even more, the post buckling finite displacement behavior of the structures.

View full abstract

The effects due to an arbitrary location of the load point on the buckling and post-buckling behaviour of elastic thin-walled beams are investigated. The governing differential equations and the corresponding stiffness matrices are derived, based on the virtual work equation of linearized finite displacement. Numerical examples are given to investigate the behaviour of I, channel and zee shaped beams. Location of load point greatly affects the post-buckling behaviour as well as the buckling loads. Although zee and channel sections show a large reserve strength as compared with I-section, this reserve strength corresponds to fairly large stresses and displacements.

View full abstract

Buckling of an annular sector plate subjected to equal and opposite moments at the radial edges is examined. The governing differential equation of the plate is solved by a Galerkin method. Buckling moments and buckling modes are obtained for the annular sector plate with simply-supported radial edges and arbitrary boundary conditions along the circumferential edges.
Numerical results are shown for various geometrical parameters and three different boundary conditions. Moreover, the buckling properties of an annular sector plate are compared with those of a rectangular plate and a circular beam.

View full abstract

An inelastic finite displacement analysis of arbitrary thin-walled open cross sectional members, using the finite element method, is presented. For the constitutive relation, the tangent modulus approach taking into account the contribution of the St. Venant shear stress to the yielding, is employed. In order to show the efficiency and versatility of this analysis, another analysis based on Prandtl-Reuss flow theory (abbreviated J2F) is developed. It is found that there is no significant difference in the results of the illustrative examples treated by the two analyses. Besides, the J2F based analysis is improved by including the shear stresses caused by non-uiform bending and torsion into the yield condition of von Mises.

View full abstract

Fatigue cracks at runways of steel track girders for a straddle type monorail have been studied experimentally and analytically. Full-scale fatigue tests of runways showed that repeated plate-bending stresses caused fatigue cracks at single-bevel groove-welded T-ioints between top flange and web and also at fillet welds connecting the longitudinal rib to the top flange. For fatigue lives over ten million cycles, fatigue strengths of single-bevel groove-welded T-joints under out-of-plane bending were obtained using small specimens. Equations for plate-bending stresses were given by a parametric study by F. E. M. Minimum thicknesses required for the top flange to prevent cracking were proposed.

View full abstract

A stress-strain model which was highly accurate and distinct in nature was already subjected to complex repetitive loads. The model is based on one of the multi-surface plasticity theories. Material parameters introduced in the model are three functions expressing fundamental sizes of multi-surfaces and weighting functions to describe the sizes at arbitrary stress-strain phases, and one of state variables is cumulative equivalent plastic strain. Investigations of the effects of these material parameters on accuracies of stress-strain relations predicted by the model are reported.

View full abstract

The work described in this paper deals with the assessment of the duration characteristics for horizontal and vertical components of strong ground motion records obtained in Japan, U. S., Mexico and Greece. The accelerograms used correspond to a range of earthquake magnitudes, between 5.1 and 8.1, to distances to the fault between 0.08 and 484km and to local subsurface conditions ranging from rock to soft clay. A total of 326 horizontal and 116 vertical components were used in the study. The definition of the strong motion duration in this study is closely related to the part that contributes significantly to the seismic energy. The duration characteristics of the above-mentioned strong motion records, using the proposed definition have been estimated and compared with their corresponding values as given by Trifunac-Brady and McCann-Shah. Correlations have been established between strong motion duration obtained by various definitions and magnitude, distance to the fault and local subsurface conditions.

View full abstract

Damping characteristics are one of the most significant factors for seismic design of cable-stayed bridges. Among various sources of energy dissipation which results in damping of cable-stayed bridges, an effect of energy dissipation at movable supports is studied in this paper, because it can be considered one of the major factors affecting damping characteristics of cable-stayed bridge in longitudinal vibration.
Three cable-stayed bridges are idealized by discrete analytical models in which friction force developed at movable supports is modeled by the Coulomb friction. Damping characteristics are determined by computed decay of free oscillation developed by smooth release from the original deformation specified.
It is found from the analyses that damping ratio of cable-stayed bridges associated with energy dissipation at movable supports depends on mode shapes. Therefore, damping characteristics of cable-stayed bridge should be carefully evaluated considering mode shape.

View full abstract

The mechanical behavior of a particle assembly is described based on Cundall's distinct element method which uses an explicit numerical scheme. Particle interaction was detected at every contact, and particle motion modelled for each particle in an assembly.
We used Cundall's simulation method to study the mechanism of slope collapse. Based on results obtained from numerical tests, we conclude that, 1) The shape of the sliding section is wave like, and 2) Particle rotation has a major function in determining the sliding zone of a section.

View full abstract

The present paper deals with the response of pipelines subjected to liquefaction-induced permanent ground displacement and the subsequent failure of pipelines is discussed. Initially here, characteristics of permanent ground displacement are investigated based on model experiments. Next, formulae obtained by a beam theory are established and preliminary analysis is carried out in order to understand fundamental characteristics of continuous pipelines. Furthermore, response simulations are conducted for jointed pipelines by using a modified transfer matrix method. We present the influential factors determining the magnitude of the ground displacements and propose the method for evaluation of pipeline response to permanent ground displacement.

View full abstract

Caces of earthquake damage to gravity quaywalls were collected for past earthquakes, and the quantity of earthquake damage which means the residual displacement after earthquakes and the cost of damage was then analyzed. An estimation method to give this quantity of the damage (residual displacement and cost) was presented, using the empirical equation which is the function of the ratio of the corresponding seismic coefficient of the ground acceleration to the seismic coefficient which gives the safety factor of unity in the stability analysis of the design standard. An optimum seismic coefficient from an economical viewpoint and an allowable residual displacement which was defined as an expected seismic damage displacement given by such optimum seismic coefficient were then studied for the rational seismic design, on the basis of the quantitative estimation method of the cost of damage.

View full abstract

Providing people with appropriate information is an essential element to enhance their earthquake preparedness. To be effective, balance between supply and demand should be kept in dissemination of the information. To seek the balance, a cross-cultural questionnaire survey was made. Respondents were from two groups in the United States and one group in Japan. The survey revealed that, contrary to the other two groups, the Japanese group showed overdependency on government initiatives rather than taking self-help action for earthquake preparedness.

View full abstract

A general second-order perturbation technique is applied in approximating the complex eigenvectors and eigenvalues of MDOF system with moderately nonproportional viscous damping. Only the nonproportionality, not the overall level of damping itself, is assumed to be either moderate or weak. Perturbation coefficients explicitly relate the complex eigenvectors and eigenvalues to the nonproportional damping matrix of the system and the natural frequencies and mode shapes of the counterpart undamped system. Using the perturbed complex “modes”, the dynamic response is expressed in a form analogous to modal superposition for proportionally damped system, but with additional terms explicitly representing nonproportionality effect. Numerical examples are given to illustrate the accuracy of the technique. It is pointed out that once the mode shapes and natural frequencies of the counterpart undamped system are known, in the present technique there is no need for numerically solving another eigenvalue problem, which would be bigger, when the damping is to be considered. This computational advantage is even more significant when designing or else identifying the system damping; either task requires reanalysis everytime that the damping matrix is changed. As a second advantage of the method, additional physical insights into the mathematical analysis are obtained. For example, the mode shapes of the counterpart undamped system are seen to couple to form the complex eigenvectors.

View full abstract

The purpose of this paper is to present an investigation of the optimal control of structure subject to earthquake loading. The control of structure in civil engineering results in the tracking problem, so that this paper deals with the solution of the tracking problem for the descrete-time linear quadratic control. The dynamic programming is used for the solution algorithm. Several numerical examples comparing the regulator control and various approximating control methods lead to the conclusion that the structure can be efficiently controlled by the methods presented in this paper.

View full abstract

As an application of the general technique presented in a companion paper, the complex modes of nonproportionally damped close-coupled two-degree-of-freedom system are approximated through second-order perturbation. Assuming the nonproportionality to be either moderate or weak, the pseudo natural frequencies, modal damping ratios, and complex “modes” are expressed in terms of natural frequencies and mode shapes of the counterpart undamped 2DOF system, and of respective damping ratios of the two single-degree-of-freedom (SDOF) subsystems. The effects of damping nonproportionality are contained in eight nondimensional perturbation coefficients. These perturbations depend only on the ratio of masses, ratio of natural frequencies, and damping ratios of the two SDOF subsystems. The approximate explicit formulas avoid the complications of Ferrari's classical solution for the quartic characteristic equation. Parametric studies illustrate the convenient use of the present formulas as well as check their accuracy.

View full abstract

In order to investigate the uplifting behavior of large-scaled LNG, LPG and oil tanks, which has recently been said to be closely related with the earthquake damages, the authors conducted a series of static tilt tests using a very large model made of aluminum alloy with about 10m diameter and 8m height. This model is characteristic of satisfying exactly the similitude with actual large-scaled tanks, and the tilt tests made it possible to conduct such large experiments and to measure the behaviors in detail.
The subject of this paper is to introduce the static tilt tests and to discuss about the experimental results concerning a prototype LNG tank, compared with the authors' theoretical calculations.

View full abstract

The objective of this paper is to develop a consistent one-dimensional finite displacement theory of curved and twisted thin walled box girders, with emphasis on the derivation of finite displacement fields in which the profile deformation and warping displacement are fully examined. The resulting displacement fields are considered to be accurate in the sense that all the second-order terms with respect to the distortional displacement and warping displacement are taken into account.
On the basis of the displacement fields, equilibrium equations and associated boundary conditions are derived from the principle of virtual work.
The validity of the governing equilibrium equations is verified by comparison with currently accepted equilibrium equations for typical cases. In addition, attention is paid on the mode of profile deformation in view of the results of finite element method.

View full abstract

A steel plate and concrete composite slab (so-called Robinson slab) is analyzed using a collocation method based on an elastic thick plate theory. A special attention is paid to the shearing force characteristics of studs in the slabs, and the effects of the spacing of stud, the thickness of steel plate and others on them are examined. Summarizing the analytical results obtained for various bridge deck models, a formula for estimating the maximum shearing force of studs is proposed.
Model slabs are tested under a static patch load. A good agreement between the analytical results and the test results is found.

View full abstract

The requirement of the minimum length of tack welds is specified to prevent the occurrence of heel cracking from the root of fillet welds. Heel crackings in the fillet welds of many 500MPa class steels with different chemical compositions are studied experimentally by using a T-shaped cracking method with various weld lengths, leg lengths, electrodes, temperatures, restrains and plate thicknesses. The level of carbon equivalent is the governing factor for the occurrence of heel cracking and the length of welds is not a dominant factor.

View full abstract

Coupled flutter oscillation of a very long span suspension bridge is numerically investigated by complex eigenvalue analysis of 3D frame model under various wind load conditions. Conclusions are as follows:
1) Complex eigenvalue analysis for flutter problem may solve uncertainties of ordinary methods.
2) Usually selected bending and torsional modes do not always develop into the critical flutter mode.
3) Selberg's estimation always gives the lowest critical wind speed of coupled flutter, although there is difference in the appeared flutter normal mode. Therefore it can work as a conservative index of coupled flutter in the wind resistance design procedure.

View full abstract

When a long suspension bridge which has relatively small ratio of side span length and center span length is designed, friction resistance between cable and saddle becomes an important problem. An experimental investigation was performed by use of equipment which simulated condition of real bridge. As the result, the slipping behavior of cable was made clear. Furthermore, it became clear that maximum friction coefficient came to about 0.33 in the case that contact surface of saddle was as ground-off, but about 0.48 if this saddle surface was galvanized with pure zink.

View full abstract

A finite element solution procedure using displacements, the Darcy velocities and pore pressures as essential variables is proposed for the consolidation problems based on Biot's theory. Spatial discretization of the equilibrium equations, the Darcy's law and the continuity equation, respectively, leads to a set of three matrix equations. In this approach, the pore pressure can be assumed to be constant within each triangular element. The displacements and the Darcy velocities are assumed to be linear. Application of a simple time integration scheme to the matrix equations leads to the numerical method presented here. Special features of the method are that the pore pressure variables are to disappear on the boundary of objective domain and that the velocity fields at any specified time can be determined explicity. Some examples are finally illustrated in order to assess the reliability of the approach.

View full abstract

This paper deals with dynamic displacement solutions of a fluid-saturated poroelastic half-space due to a vertical point excitation in the interior of the medium. The solutions are derived by a transfer matrix method using a vector-matrix which is obtained by double Fourier transformation. As numerical examples, this paper shows results of the vertical displacement due to a vertical point excitation with nondimensional frequency changing.

View full abstract

In thin study, in order to evaluate the extreme value distribution of wind speed from each wind direction in consideration of Typhoon effect, the “Typhoon factor” was induced into the extreme wind speed expected from parent distribution characteristics obtained from usual wind speed measurement at local meteorological observatories in Japan.
Furthermore, the evaluation method of failure probability of a long span bridge due to strong wind was developed in taking the extreme distribution of directional wind speed, wind direction and its incident angle, aerostatic and aerodynamic response of the bridge into account.

View full abstract

In order to examine the fatigue performance of repairing welds and residual stress relieving for corner joint with weld defects, box section specimens of 300mm in height. 130mm in width and 3400mm in length were tested. The fatigue strength of corner joints which were repaired by using arc-gouging and welding satisfied the allowable stress range for category B. The improvement of fatigue strength by stress relieving is not so significant. Based on these results, the repairing method by using arc-gouging and welding was adopted for the fabrication of the Seto bridges in Honshu-Shikoku bridge project.

View full abstract

The purpose of this paper is to investigate the axial forces of lateral bracings and the additional stresses of main girders in skew girder bridge due to dead load and live load. 12 simply supported skew bridges with various numbers of main girders, and with various angles of skew to the abutment line, have been examined applying the 3-D space frame formulation.
In addition, an approximate method was developed to calculate the lateral bracing forces of skew bridge. And it has been cleared that the eccentric distance between support and shear center of a bridge has a influence on the lateral bracing forces.

View full abstract

Unbraced steel rigid frames are frequently used in civil engineering structures, such as main towers of suspension bridges and of cable stayed bridges, piers of bridges constructed in urban areas, and so on. Such structures must be designed considering second-order moments produced by vertical loads acting on the displaced structures, the so-called P-Δ effects. In this paper, several design methods which take into account the effects are critically reviewed to find out which method is the most adequate one. Subsequently, a design method is proposed here which is a modified version of the current Japanese specification for highway bridges.

View full abstract

This paper presents a method on determination of the optimum pile number for the steel pipe pile foundation of bridge pier using nonlinear programming. Herein, it is assumed that a fictitious wall model behaves in a similar manner as a real pile group. The sectional properties of the wall model are firstly estimated by selecting the minimum total cost as an objective function and the design criteria of pile in the specification of Japanese road bridge code as the constraints. Then, the design variables, i. e., pile diameter, thickness and pile number are determined by using the sectional properties obtained above so that the active constraints may be satisfied. Finally, all design variables are checked by the deformation method of pile analysis if the design criteria are satisfied or not. Two pile foundations are designed to illustrate the features and scope of the approach. It is confirmed that this method can determine the optimum pile number, diameter and thickness so that the total cost of pile and footing may be minimized. It is also found that this method gives more economical solution than the conventional and empirical method.

View full abstract

An experimental investigation on effect of horizontal friction plate as a method to increase friction resistance of saddle of suspension bridge was performed. As a result, it became clear that whole maximum friction resistance was less than total of maximum friction resistances on each contact surface. Furthermore, behaviors of friction between wire and steel galvanized with pure zink, between zink plates, and between wire and zink plate were made clear.

View full abstract

A study on damaged or undamaged small earth dams for irrigation in Aomori and Akita prefectures by Nihonkai-Chubu Earthquake in 1953 was carried out by distributing relevant questionnaires. A total of 1129 data on the irrigation dams were used for analysis. The irrigation dams were classified into three groups, such as heavy-damaged dams (A), light-damaged dams (B) and undamaged dams (C). The ranks of seismic damage in the dams were investigated by the Type II Quantification Analysis based on the available data, which has been frequently used in Japan for statistical analyses including not only quantitative data but also qualitative data. As the results of analysis, 8 items were selected from 27 items as the factors greatly affecting the earthquake damage of a small earth dam. Weighting factors were given to items so as to discriminate the heavydamaged group from the undamaged group including light-damaged dams as clearly as possible.

View full abstract

The survey of earthquake-undamaged structures is regarded as important for the progress of earthquake engineering as that of earthquake-damaged structures. Actually however, there are few survey of undamaged structures due to earthquakes. Through the investigation of the complete survey which contains both damaged and undamaged data, it could be understood which case is susceptible to damage for a structure and also which case is not. From this point of view, the complete survey of damaged and undamaged small earth dams for irrigation in Aomori and Akita prefectures due to Nihonkai-Chubu Earthquake in 1983 were carried out by distributing relevant questionnaires, from which a total of 1129 data on the irrigation dams were used for a series of analysis. On the basis of the data of this survey, two different damage ratios were compared in this study. One is the ratio of the number of damaged dams which could be obtained even from the survey of damaged dams, the other is, so to speak, “the damage ratio” which was obtained only from this complete survey. Two ratios were investigated in detail and the significance of such a complete survey was discussed.

View full abstract

In a dynamic response analysis of structure-ground system, we often use spring-mass model. A propagation characteristics of an earthquake force between structure and surface ground is shown in dynamic K-value. We generally obtained K-value from the results of vibration test of structure or its model. But the vibration test is very expensive and offhand.
Therefore, this paper suggests an analytical method of a dynamic K-value in a laboratory based on a hybrid experimental method. A hybrid experimental apparatus for analysis of K-value is composed of micro-computer and dynamic tester. We calculate the dynamic behavior of structure by a micro-computer and obtain an earthquake force due to the relative displacement between structure and ground by a dynamic tester.
As an analytical case, we analyzed the dynamic K-value of between surface ground and structure during an earthquake.

View full abstract

This paper presents a calculation procedure to estimate longitudinal seismic stress developed in shield tunnel linings based on seismic deformation method.
Linings of shield tunnels, which have discontinuities in the longitudinal stiffness due to a number of ring-joints, are idealized by uniform beams with the stiffness equivalent to that of segments-joints system. Axial force and bending moment in the tunnel linings subjected to ground displacement with sinusoidal distribution along the tunnel axis are mathematically evaluated considering nonlinearity of lining stiffness.
Factors dominating the seismic stress of shield tunnels are studied. Characteristics of seismic response of shield tunnels is also discussed in comparison with underground pipes with uniform stiffness in axial direction.

View full abstract

Since a region analyzed by the FEM must be finite, artificial boundaries are introduced into the model when a widely extending area such as infinite ground is analyzed. Special boundary conditions have been proposed for the artificial boundaries, such as a viscous boundary.
Although the commonly used viscous boundary has less ability to absorb energy, the boundary has many merits, for example, such as the applicability for nonlinear problem and simplicity of coding for computer programs. These merits are very important, especially for three dimensional nonlinear problems.
In this study, the viscous boundary for a full three dimensional interaction system was derived by virtual work. The effectiveness of the boundary was examined in detail, and it was found that the proposed viscous boundary showed good energy absorption, in contrast with previous formulation.

View full abstract

If the ground where a telephone pole is embedded is susceptible to liquefaction during an earthquake, the telephone pole may sink, lean, or even fall down. A series of model shaking tests were conducted to investigate the failure phenomena due to soil liquefaction, and to examine the effectiveness of four types of telephone pole stabilization techniques against liquefaction. Two types of test patterns were conducted to determine the effects of suspended cables on telephone poles during ground shaking.
After showing measured accelerations and excessive pore pressures, and observed horizontal movements and settlements, this paper describes the effectiveness of stablizing techniques. A foundation of crushed grain with net was found to be the most effective against pole damage due to soil liquefaction resistance.

View full abstract

Surface wave near a dipping layer is predicted by multiplying the proposed magnification factor with spectra of incident wave components. The magnification factor is expressed as the product of the influence coefficient of Love wave and the magnification factor in the surface layer. The influence coefficient of Love wave is formulated as an explicit form. It is found that the incident wave whose period is longer than Airy phase consist mostly of surface wave and predicted spectra of surface wave is close to the one of the surface wave separated from the observed earthquake motion.

View full abstract

A steel elevated guideway for a straddle-type monorail consists of two main track girders and several I-shaped cross beams which connect the two girders. The connection of a cross beam to the track girder is subjected to bending moment, and a number of cycles of the moment reaches a total of 2.8 millions for 70 years.
To study on the fatigue strength of the connection, fatigue tests with three-type connection models have been carried out.
The present paper reports the fatigue test results and discusses characteristics of the fatigue strength of three-type connections.

View full abstract

A fatigue test data base of bolted and riveted joints is established using a personal computer. The data base of fatigue strength of bolted and riveted joints can be used for fatigue assessment of bridges in service and establishing maintenance plan. In order to express test conditions and fatigue strength, 49 items are input and 14 others are calculated from the input data. So far, 294 fatigue test data on bolted joints and 298 data on riveted joints have been collected from various sources. The factors affecting fatigue strength of bolted and riveted joints are investigated using application programs, and the data is compared with fatigue allowable stresses of current fatigue design code.

View full abstract

Bolts and bolted connections are indispensable in most steel structures today. In civil engineering field, especially in bridge structures, bolts of large diameter are frequently used in very important portions such as shoes, expansion joints, cable anchorages and so on. Recently, accidents caused by fatigue failure of these bolts have been reported and importance of maintenance has been strongly noticed.
This research is to establish reasonable non-destructive detection method for fatigue cracks of bolts in their service conditions. Two types of ultrasonic testing method were proposed and their detection performances of fatigue crack were examined by fatigue test of bolts. From this experiment, data on fatigue crack growth and fatigue life of bolts were obtained and accuracy of fatigue crack detection by proposed ultrasonic testing was confirmed. As the results, possibility of rational supervision system for bolts in use was shown.

View full abstract

It will be significant to study the devices for increasing the structural damping of the cable-stayed bridges, because the structural damping plays an important role in the aerodynamic behaviour. It may happen that the transverse local vibrations of the cables as a partial structure system couple with the vibrations of the cable-stayed bridge as a whole structure system, for those bridges in recent years which tend to be more longer and to have the multi-cable system.
Therefore, in this brief paper, the effects of cable vibration dampers on the whole structural damping of multi-cable-stayed bridges was investigated by means of complex eigenvalue calculation. And it was shown that the structural damping of this type of bridges having the dampers in the stay cables could be increased as much as significant in aerodynamic design.

View full abstract

The method of estimating tension of bridge cables by measuring their natural frequency, so-called vibration method, is a very convenient way at the construction site of structures with cables. However in order to apply the method to estimate hanger-rope tension of a suspension bridge which has long spans, there still exist several problems to be solved as shown below because those ropes are tied with hanger clamps.
1) The vibration mode of two hanger ropes connected with a hanger clamp is needed to research beforehand.
2) The effect of hanger-clamp weight on estimated tension is necessary to investigate beforehand.
3) The accuracy of tension estimated by vibration method is necessary to compare with tension measured by a loadcell so as to get reliable estimation.
In this paper, the above mentioned problems are discussed and checked.

View full abstract