Key historical events and technological developments in the field of structural engineering with emphasis on civil steel structures for the past 50 years are reviewed to think about the present problems from four different perspectives, such as material, analysis and measurement. The current state and future prospects of this engineering field are discussed to open up a new vista of the future.

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Theoretical analysis of dynamic responses of liquid in circular cylindrical shells with not co-axis subjected to earthquake motions was carried out by applying bipolar coordinate transform and finite difference method. The equations of motion developed by Flugge for circular cylindrical shells were used. On the other hand, model of the dual circular cylindrical shells was made of acrylic resin. The model was fixed on shaking table and was subjected to earthquake motions. Time history of response of dynamic water pressure on the tank walls was measured by water pressure gauge. Analytical results obtained by numerical calculation agree well with experimental results obtained by using shaking table.

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This paper presents a strain energy analysis of four edges simply supported rectangular plates resting on elastic foundation. The analysis is based on the three-dimensional (3-D) theory of elasticity, and the elastic foundation is described by the Winkler model. An analytical solution was exactly derived by using the double Fourier series expansions. The effects of thickness-to-length ratio, aspect ratio, non-dimensional foundation parameter and transeverse load on the strain energy and elastic energy of rectangular plates resting on elastic foundation are investigated in detail. Moreover, the validity and applicable range of the first-order shear deformation theory, called Mindlin plate theory, in comparison with 3-D analysis were also presented for bending problem of rectangular plates under transeverse load on elastic foundation.

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The design of membrane structures needs to analyze the behavior of finite displacement after the completing as well as during the construction. The paper proposes the computational method that uses a structural model replaced with line-member units without restricting the shapes of triangular elements and the Poisson's ratio. The model composed by the units keeps compression-free, so that the proposed method can more easily get equilibrium solutions than using the element with a bilinear stress-strain relation. If the analysis may neglect the bending stiffness in membrane structures, the method gives more exact solutions than the bilinear model that assumes the element to be plane and that uses expedient compressive stiffness.

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Liquid sloshing of oil storage tanks caused by Tokachi-Oki earthquake in 2003 gave severe damage to oil tanks in Tomakomai area. Up to now, we have verified the effect of sloshing damping device by conducting a shaking experiment of a real scale tank. However, the method of setting up this device and the verification of the influence on the floating roof that this device brings remain as a problem. In order to verify the setting method of sloshing damping device, we conducted a experiment of loading to sloshing damping device in static and dynamic condition and verified the influence that the rigidity of this device gave to a floating roof. Moreover, we proved this device to be an explosion-proof specification by confirming that the use of this device did not generate an excessive temperature rise.

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Seismic behavior of sheet pile quay walls with ground anchor for seismic reinforcement is not clarified enough, because few case study of seismic behavior has been conducted. In this study, shaking table tests with a scale of 1 to 17 model in 1G field were conducted to investigate seismic behavior of sheet pile quay walls with ground anchor. And effective stress analyses were conducted to simulate seismic behavior of sheet pile quay walls with ground anchor in this tests. By arrangement of the ground anchors, displacement of the quay wall was fairly constrained and effectiveness of them was confirmed by the test and the analysis.

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In this paper new buffer devices are developed, and performance of these buffer devices are observed by static tension test. Dynamic performance of one buffer device is tested by falling rock to wire-buffer device system and to falling rock protection system. Furthermore, by comparison of falling rock experiments and dynamic response analyses, performance of falling rock protection can be simulated by dynamic response analysis.

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The strain distribution behavior of the steel member during heating and cooling process in the welding of steel is very important information to know the generating process of the welding deformation. In this study, using the digital image correlation method (DICM), the measurement of strain distribution in the steel surface produced during heating and cooling process in the welding of steel was carried out. In addition, to examine the relationship between temperature and strain distribution, the temperature measurement was also performed by the infrared thermography equipment.

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Rigid framed steel bridge piers had several damages like plate buckling by the attack of the Hyogo-ken Nambu Earthquake. To update seismic design adequately evaluating strength and ductility on in-plane behavior of the pier, some analytical modeling, which can consider plate buckling, is required and is available now but not for practical business use. Then investigated in this study is an adequate modeling method when using beam-column element based on Euler-Bernoulli theory for the analysis and influences of some modeling methods on the seismic performance of the in-plane behavior of the pier.

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Tension and shear block failure is a limit state which occurs in the connection of tension steel members. The failure mechanism is a combination of tensile failure on one plane and shear failure on the perpendicular plane. Although the design strength equations for the tension and shear block failure are shown in the well known design codes, they are different in respective codes. And they provide inconsistent levels of safety when they are used in different types of connections. In this paper, we begin with overviewing the design strength equations in the various codes. Then, the pertinent strength equation to the gusset plate of steel truss bridge is selected on the basis of FEM analysis. Moreover, applicability of the strength equation for compression and shear block failure to gusset plates subjected to compressive force in steel truss bridges is examined.

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Installation of CFRP strips of high elastic modulus can be effective for improving the load carrying capacity of a superannuated existing steel I girder. Experimentally investigated in this study are some debonding prevention methods at the edges of the CFRP strips onto the lower flange plate. At the first step, the bending tests are carried out for six girder specimens with different adhesive lengths of the CFRP strips. Then, debonding prevention plates at the edges of the CFRP strips and tie plate and tie rod bridging both edges of the CFRP plates over the steel splice plate of bolted connection is proposed to prevent the debonding and the effectiveness of the methods are examined for the specimens with the debonding.

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Recently, slope disasters accompanied with localized heavy rain are frequently occurred. It is necessary to clarify the mechanism of a slope collapse. A lot of studies on sandy soil slope have been carried on. Recently, the studies on the unsaturated hydraulic properties for sandy soil have been conducted to examine the mechanism of the slope collapse in detail. However, there is little study on the unsaturated hydraulic properties of rock mass. In particular, there is little study in which the stability of a rock slope is discussed with considering the unsaturated hydraulic properties. Thus, in this study, the effects of the unsaturated hydraulic properties on the stability of a rock slope are examined. In results, it is clarified that the unsaturated hydraulic properties should be considered to evaluate the stability of the rock slope.

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This paper presents an analytical approach on shape effect of aggregate elements to the angle of repose in the distinct element method. The angles of repose were measured in experiments using three types of the gravels. The distinct element method using an aggregate element model is developed. Changing shape of the aggregate element, the angle of repose of gravel models by those elements are computed by using the proposed distinct element method. Based on comparison of the angles of repose between the experimental results and the analytical one, the shape effect of the aggregate elements on the angle of repose is discussed.

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The problem of wave propagation in pipe on foundation is very important in both civil and mechanical engineering fields. This paper presents a complex field general variational statement to study dynamic dispersion curves of waves propagating in pipe-foundation system. A semi-analytical technique is used to construct the varialtional complex wave field and a three dimensional continuous medium model is used for its general applicability. The formulation and its program are verified by comparing with the available results obtained using other methods for a freely supported solid elliptical cylinder. Numerical results show dispersion changes of varying degree in the presence of foundation and reveal significant influences of foundation on low order propagating modes and low frequency range. The results are further discussed in details for different fields of practical use and frequency ranges of engineering interest.

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This study focuses on the optimization method of bridge management system. In many conventional cases, the plan involved in the BMS has been handled with a deterministic approach using the LCC as the objective and the year of repair for each member as design variables. However, this formulation involves many combinations of design variables, and does not increase the number of bridges for which effective design solutions can be obtained. While the authors used this formulation, effective solutions were obtained for only around ten bridges at most. From such a viewpoint, the conventional formulation of occasional repairs is not considered practical. In this study, another formulation was made using the inspection intervals of each bridge and the degree of soundness of members to be repaired as design variables.

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In this study, optimization that used GA was tried about the traffic restriction method of the large-scale repair. Concretely (dangerous cost + repair cost + income decrease cost), the best restriction method of the repair assumed to be minimum was calculated. Concretely, it is a comparison of a short restriction on the weekend, a large-scale middle or long restriction, and a large-scale suspension of traffic. Moreover, the solution was compared by GA as an effectiveness verification of the constructed GA program with the round robin. Thus, it came to be able to compare the restriction method easily by using the constructed GA program for a specific route or the section in the route that was.

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The purpose of this research is to propose an early restoration for lifeline systems after earthquake disasters. Here, two issues are focused on, the first of which is such an allocation problem that which groups will restore which disaster places, and the second is such a scheduling problem what order is the best for the restoration. In order to solve the two problems simultaneously, Genetic Algorithm (GA) is applied. However, road networks after earthquake disasters have an uncertain environment. In this study, the priority of an allocation that which groups will restore which disaster places is optimized under uncertain environments. So, the restoration schedules adapting to various situations can be made by using this priority. An attempt is made to develop a decision support system of the optimal restoration scheduling by using the proposed method.

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Monte Carlo simulation is conducted in order to study the traffic live load for the continuous girder bridges 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 the continuous girder bridges.

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This paper discusses an effect of the grid shape of open type check dam structures on the probability of rocks capturing. First, it is assumed that the capturing event is a probability process, i.e., a geometric distribution in a Bernoulli sequence. The probability associated with the event that a rectangular space is stuffed by some rocks which diameters follows the log-normal distribution is estimated by using Monte-Carlo simulation. In this estimation, the random effect is examined by two random variables, i.e., 95% probability of exceedence and a coefficient of variation of rock's diameters.

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In this study, we applied the idea of the rough set to the landscape evaluation of the girder bridge. The problem of the multicollinearity and the number of samples was restricted in the theory of quantification theory had been applied by the Kansei engineering technique so far. We tried to apply the rough set to solve those problems. We compared the rough set and the quantification theory, and showed the merit and the weak point of the both hands method. The evaluation and the method of the relation with the design element were shown, and we matched and examined the reflection method to the design in the bridge landscape architecture in the future.

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In order to identify the vibrational properties of the huge structures, such as long - span bridges, high rise buildings, and chimney stacks, the operational modal analysis method is going to be widely applied. In this study, it is clarified that the natural frequencies, the eigen modes, and modal damping ratios can be obtained from the cross correlation functions of vibration responses using the general experimental modal analysis software.

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Behavior of horizontally curved I-girder bridges are complex and its interaction analysis is difficult. In this study, extended three-dimensional finite element interaction analyses were conducted parametrically. The bridge is modeled in detailed with solid and shell elements and vehicle is simulated as a nonlinear model according to HS20-44 design truck. Road roughness profiles are generated from power spectral density and cross spectral functions. By using these models, natural vibration and forced vibration analyses carried out in parametric study, are extensively investigated. The analytical results are significant and give some useful information regarding the impact factor of the studied bridge which could be much helpful for practical designer.

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Environmental vibration caused by the ground vibration and the infrasound transmitted from the highway bridge occurred at the houses near the RC hollow slab highway bridge. Examinations were carried out to investigate the vibration characteristics of the bridge due to running trucks. According to the results of the examinations, it is clear that the bridge vibration generated by the deformation of the elastic shoes was transmitted to the houses near the highway bridge as ground vibration and infrasound. Therefore, the elastic shoes were removed and the abutment was changed to the rigid frame structure as a prevention measure. The validity of the prevention measure was confirmed by comparing the monitoring data before and after the prevention measure.

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Bridge dynamic characteristic estimation method with ambient vibration has been used in public recently as a bridge health diagnosis technique. Conventional studies by the authors showed that the vehicle-induced ambient vibration give harmfule effect for estimating low order-frequencies of the bridges by using realization theories. In this study, the authors conducted futher investigation on the tendency of the problems. The wind-induced or/and running vehicle-induced vibration data of existing arch bridge were used for series of simulation to evaluate the running vehicle effects. As a result, we cocluded that wind induced ambient vibration should be used for estimating dynamic characteristics of the objective bridge.

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Using the idea of data sampling interval, a new method has been proposed to improve the estimation accuracy of dynamic characteristics with ERA method. The coarse re-sampling data of low frequency vibration is prepared by eliminating intermediate data points, and dense re-sampling data of high frequency vibration is prepared by using cubic spline interpolation. The vibration data has been filtered to generate low, medium, and high frequency vibration data. The proposed method is evaluated by numerical simulation of a stiffened arch bridge and experimental data obtained by field measurement of an existing bridge. The results obtained both from numerical simulation and experimental data demonstrate high accuracy of the proposed method. In particular, coarse re-sampling and dense re-sampling data will lead to better estimation of bridge dynamic characteristics.

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As the hybrid stress-ribbon highway bridge is flexible, we considered that it was necessary to examine the dynamic responses under moving vehicle loads. In this paper, we calculated the dynamic response of the hybrid stress-ribbon highway bridge under moving vehicle loads by the simulation methods. The span length of bridge is 400m proposed reference 1). Using the calculation results, we examined the vibration serviceability for the walkers on this bridge and the dynamic increment factor based on the bending moments of main girder and the dynamic increment factor based on the axial forces of hanger.

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In order to improve the aeroelastic stability, there is a prestressed concrete stress ribbon footbridge, which was widened at the end of the span. The serviceability of the lateral vibration of the widened bridge is not clear. Therefore this study investigates the serviceability for the lateral vibration of the PC stress ribbon footbridges due to widening at the end of the span. This study made widened stress ribbon footbridge analytical models with various widths and span lengths using finite element method. Additionally, eigen-value analysis was carried out to grasp the vibration characteristics of those bridges. The vibration serviceability subjected to pedestrians walking on those bridges was simulated using the Hivoss guidelines method.

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This paper describes a seismic risk assessment for existing trunk lines which are to be annually expanded by the subsystems consisting of a subsidiary pipeline network and the shutoff valve. The maintenance activities range from daily patrols to large-scale retrofit, while taking the deterioration effect into consideration. The discussion focuses on the probability of failure for the overall system, for various combinations of the safety level in the control valve and the pipeline network.

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In this paper, we demonstrate the effect of spatial variations of shear wave velocities of soils and predominant periods of ground on the seismic response of a site, where minor liquefaction was observed in a coastal reclaimed land during the 2001 Geiyo Earthquake. Those properties are obtained by surface wave exploration covering a 200-m line and highly dense mesurement of microtremor along the line crossing or passing by some of the liquefaction sites. Based on developed consecutive 48 models of ground along the line, one dimensional seismic response analyses are conducted. Experimental and analytical results are clearly harmonized in terms of clarifying liquefaction initiates in the most susceptible points in a spatially variant ground.

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In this study, a simple method for estimating the earthquake motion on engineering bedrock is proposed using the given motion on the ground surface by means of the attenuation relation. The regression expression for converting the PGA or PGV into PBA or PBV was proposed through series of nonlinear dynamic analysis, taking into account the configuration of soil deposit and amplitude of earthquake motion. It is confirmed that the proposed method is advantageous over traditional estimation in reproducing the observed records.

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The evaluation of strong motion with high accuracy is very important to clarify the mechanism of earthquake damage. The strong motion estimation methods which correct the difference of site effects between the reference site and its neighboring sites based on seismic observations are easy to be applied in Japan. In this article, the estimation methods were applied to the Horinouchi interchange of the Kan-etsu expressway and that circumferential strong motion station in the 2004 Mid Niigata Earthquake. We confirmed that not only the consideration of the site amplification factors but also the consideration of the site phase effects are very important.

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In this study, the effect of partial soil improvement against liquefaction by Permeable Grouting Method (called as PGM) is examined. In this proposed method, the thickness of unimproved liquefiable layer is set evenly in the whole target area. The both of model-scale and full-scale experiments were conducted in order to confirm the effects on the restraint of deformation of ground. As a result, the partial soil improvement ratio is set in the range of 70-100%, in the case that PGM is applied for countermeasure against liquefaction of the ground under runway.

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This paper described a new countermeasure against liquefaction and Tsunami for existing coastal levee using steel sheet pile. The feature of proposed method in this paper is possible to reinforce the coastal levee constructed at narrow space near various kinds of facilities. In this study, a series of shaking table tests was carried out to estimate the performance of steel sheet pile installed behind the coastal levee after liquefaction. As a result, even when the function of coastal levee is lost due to liquefaction, it was found that countermeasure against Tsunami by steel sheet pile will be possible.

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A finite element modeling, which uses water elements with degree of freedom of displacements, is investigated for the seismic response analysis to consider hydrodynamic pressure by sea water and porewater in the backfills. Hydrodynamic pressure from sea water as well as displacement of water is found to be well expressed by introducing excess reduced integration (one point integration) in building element stiffness matrix of water whereas conventional two-point integration method failed to express them. On the other hand, houglass instability becomes significant in the backfill ground when one point integration is used for both soil skeleton and porewater.

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Column confinement is an important component of the seismic design of reinforced concrete columns. The confinement of core concrete improves the overall strength and stability of the structure subjected to large seismic lateral forces. However, most existing studies of confined high-strength concrete are based on relatively small-size specimens; therefore, it is difficult to evaluate structural size and geometrical effects on compressive behavior of confined concrete. This study uses experimental data on large-scale high-strength concrete tied columns with a 450 × 450 mm square section and 500 mm in diameter to investigate the effect of specimen size on compressive fracture behavior of reinforced concrete column. Each specimen has strain gages within the column to measure the local strain. This study provides insight into the properties of confined concrete, and will contribute to the development of a more rational approach to seismic design of reinforced concrete columns.

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Wall-type reinforced concrete piers have been broadly constructed out of urban area under space limitation. If the longitudinal axis of a bridge with this type of pier intersects to the direction of river flow or railway line with some skewed angle, however, the deformation capacity against earthquake should be evaluated appropriately as a function of the skewed angle. This paper aims to study a rational procedure of seismic design through cyclic loading tests for wall-type skewed piers in consideration of the bearing restriction. As a result, several important findings are obtained such as; the skewed angle makes the buckling length of longitudinal reinforcement short, the skewed angle improves load and deformation capacity.

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It has been known that the ductility of bridge piers can be improved if they are constructed of high ductility cement, but the use of this cement is not so widespread because of cost problems. To find the most efficient use of this material for seismic strengthening of bridge piers, the authors performed a loading test using specimens with varying cover concrete thicknesses. From the experiment, it shows excellent deformation by using spiral reinforcement, and high ductility cement.

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Many old over-road steel railway bridges in the metropolitan area are built in an important part of the transportation network. However, there are no specific methods for evaluation of their earthquake-resistance. In this study, we have conducted cyclic load test of the pivot bearings which are widely used for such steel structures. We have proposed a hysteresis model of the pivot bearings and developed a method for evaluation of earthquake-resistance of the steel structures adopting the pivot bearings. In addition, we have proposed and experimented with a simple reinforcement method of pivot bearings, and the experiment result revealed the effectiveness of that method.

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A rigid-frame arch bridge named Xiaoyudong Bridge received great damage in Wenchuan Earthquake, China, 2:28 p.m. (Beijing time) on May 12^th, 2008. Based on the detailed field survey, the damage condition and the possible mechanisms of failure have been summarized. It has been found that the surface fault had an enormous influence on the damage of A1 and Span 1, while the seismic force made Span 3, Span 4 and Pier 3 failed. Further, pushover analysis has been performed to preliminarily judge the bearing capacity of it. From the result of pushover analysis, the middle span and the bottoms of both inclined legs have been found to be the crucial points of the bridge that the tensile reinforcement might yield from 0.40g horizontal load for them.

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To evaluate the wave force to the bridge by the tsunami wave, the experiment was conducted. We paid attention to the wave height and the setting position of the girder. In the case of broken wave, the horizontal force was larger than the case of non-broken wave and the maxium horizontal force was measured at the middle position against the wave height. An equation for horizontal force at some girder height was obtained from the pressure distribution at broken waves. The horizontal force which was calculated from measured wave velocity was approximately fit for the measured horizontal force in the case of broken wave.

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The three dimensional nonlinear earthquake response behavior of a steel truss bridge near a thrust fault is investigated. The input ground motions with permanent displacements due to the thrust fault with the Japan Meteorological Agency Magnitude M6.5, subjected to each supports of the bridge, are simulated using the stiffness matrix method where the kinematic source model and the horizontally layered half space are assumed. The steel truss bridge is modeled as the three dimensional nonlinear frames using the Fiber Element Method. The effects of the sedimentary layer and the depth of the upper edge of the fault upon the ground motions, and upon the behavior of inelastic response of the steel truss bridge are examined. It is found that the vertical ground motions are distinguished and they significantly affect on the inelastic response behavior of the steel truss bridge. It is also found that the thickness of sedimentary layer as well as the spatial position of the bridge strongly affect on the response behavior of the bridge.

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Seismic retrofit of an existing network arch bridge against large-scale (Level 2) earthquake ground motions was performed by modifying existing fixed steel bearings into slit-type knock-off bearings. Three-dimensional non-linear dynamic response analyses were carried out considering site-specific ground motions. It was confirmed that shear panel dampers as passive energy-dissipation were needed on both fixed-side and movable-side pier tops to avoid the potentially difficult retrofit work for the undersea pier anchors and foundations. The authors proposed slit-type knock-off bearings with the knock-off function as triggers against the Level 2 ground motions to provide isolation effect. Performance tests of the slit-type knock-off bearings were conducted to verify the required performance for the seismic retrofit design.

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In this study, cyclic loading tests were conducted to clarify the extremely low cycle fatigue crack (ductile crack) initiation and final failure mode in thick-walled steel structures with welding defects. Welding defects were installed into the butt flange joint of beam-column connection at which full penetration welding should be usually made against the earthquake motion. Five test specimens were manufactured which are simulated actual details and welding method of beam-column connection of steel pier. As a result of experiment, properties of ductile crack initiation which depend on the difference of the width of welding defects were clarified.

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For safety check of steel bridge piers in elevated girder bridges under the coupling of bi-directional horizontal seismic accelerations, an interaction surface is derived to specify the ultimate state of bridge piers. Considering the realistic conditions of girders supported by bearings at the top of piers, this ultimate interaction surface is derived in terms of bi-directional horizontal forces and bi-directional bending moments acting at the top of the piers. In the derivation of the interaction surface, bending moment components are converted to equivalent horizontal force components by introducing the concept of effective height. The accuracy and validity of the ultimate interaction surface is examined by numerical analysis when applied to the four piers that support a conventional 3-span continuous girder bridge subjected to bi-directional seismic accelerations. As a result, it is observed that the proposed ultimate interaction surface is reasonably accurate. However, it is a little conservative to check the overall instability of the bridge system by using of the ultimate interaction surfaces of the respective piers.

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The objective of this study is to examine experimentally and analytically the behavior of steel truss structures in cyclic loadings. The adequacy of a numerical model developed in the past study for analyzing truss structures under cyclic or dynamic loadings is examined in view of the test results of model truss structures. Five steel truss specimens whose panel points are rigidly connected through gusset plates by high-tension bolts were tested under constant vertical loads and monotonically or cyclically increasing horizontal loads. One truss model equipped with buckling restrained braces as diagonal members was also tested. Moreover, elastic-plastic large displacement analysis is executed with appropriate modeling of test truss structures and with initial lateral loads simulating initial imperfections. In many cases, good correlation between test and analysis is observed up to the points where local bolt hole damages appear near the lower panel points of test truss structures.

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This study focuses on the seismic behavior of Shear Panel Dampers (SPDs), which are introduced to improve the seismic performance of a benchmark steel arch bridge. Four schemes of seismic upgrading models are considered for different ground types. Then dynamic analyses are carried out with 12 patterns of Level 2 earthquake ground motions, and seismic performances of the upgrading models are compared with the original structure without dampers. The influence of repeated earthquakes is also examined by using the same ground motions repeated for three times. Based on the seismic demands of SPDs obtained from dynamic analyses, the necessary capacity values of SPDs with safety margins to against repeated earthquakes are proposed.

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Elasto-plastic characteristics of shear panel dampers (SPDs) as passive energy-dissipation and applicability of the SPDs to seismic retrofit design were investigated experimentally and analytically. Hysteresis loops of various SPDs and their failure modes were investigated through cyclic loading tests. From experimental results, elasto-plastic characteristics were discussed for optimum SPDs. A design method of the SPDs was also discussed for seismic analysis modelling. It was confirmed that the SPDs with low yield steel can be employed to achieve a rational seismic retrofit of long span bridges against large-scale (Level 2) earthquake ground motions.

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In this research, response reduction method for a mast on a railway viaduct is proposed by means of the viscous-type damper. The effectiveness of the proposed countermeasure was investigated by the shaking table tests, in which real-scale masts with and without dampers were mounted and excited by an expected motion on a hypothetical viaduct. It is confirmed that the damper could reduce the displacement at top of the mast by 70% from that without damper. It is also clarified through numerical simulations that the proposed damper has a capability to reduce response of a mast, regardless of the natural period of a viaduct.

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This paper presents performance requirements for out-of-plane bending rigidity of gusset plates connected to buckling-restrained braces (BRBs). BRBs are connected to the main structural members through gusset plates, and so it is crucial to design the gussets appropriately in order for BRBs to exhibit their maximum performances. Then, a parametric study of out-of-plane deformations of the gusset was conducted to specify the performance of simplified gusset design conditions. In the performance tests, a number of gusset-model test specimens were fabricated to which BRBs are connected, and were subjected to cyclic axial forces. Finally, this proposed strength capacity of the gusset is found to satisfy the proposed performance requirements.

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The previous study on low cycle fatigue tests of buckling-restrained braces (BRBs) showed that all the specimens had good fatigue performance, but the performance in relatively small strain amplitudes was found to be affected by the welding of bracing member end ribs. In order to upgrade furthermore the performance, nine test specimens with end rib welding toes being finished with a grinder are prepared and tested under constant and variable amplitudes. As expected, improved low-cycle fatigue performance has been obtained. Based on the test results, the low-cycle fatigue damage formulas for as-welded BRBs as well as toe-finished BRBs are recommended as the reference for the strain-based damage assessment.

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