Methods for mixed discrete-integer-continuous variable nonlinear optimization are reviewed for structural design applications with focus on problems having linked discrete variables. When a discrete value for such a variable is specified from an allowable set, the values for other variables linked to it must also be used in all the calculations. Optimum design of steel frames using commercially available sections is an example of this class of problems. A general formulation for this type of problems is developed. Approaches for solving such practical optimization problems are described and classified into single and multiple design variable formulations. Many approaches use two phases in their solution process before the final discrete design is obtained: In the first phase, a continuous variable optimum is usually obtained, and in the second phase, the continuous solution is somehow utilized to obtain the final discrete solution. Some of the basic optimization methods used in these approaches are also described.

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In this study, a model on the basis of artificial neural networks is developed to predict the peak horizontal acceleration. The neural network model provides an objective analysis method which requires neither specifying predictive functional forms nor the independence of the inside variables. The Joyner and Boore data set (DSSA, Vol. 71, pp. 2011-2038, 1981), was used for analysis. For comparison, one-and two-step regression procedures were also applied to the same data set. Various fitness criteria have been considered. Finally, the proposed procedure showed an agreeable capability for the required prediction of ground motion parameters.

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Ductility has been a popular damage measuring index, though it fails to account for the role played by repeated inelastic excursions of different amplitudes. A typical earthquake response time history is characterized by the repetitive cycles with different orders of peaks. In such a case, damage not only depends on the maximum response and its magnitude beyond the yield level but also on the higher order peaks. Thus, the additional parameters of interest are the total number of peaks, and the number as well as the extent of non-linear excursions. To obtain the expected damage corresponding to a response process, a model has been considered which includes the uncertainties both in terms of the amplitudes of the peaks and of their ordered occurences. Under the assumption of a narrow-banded response, the effects of the system parameters and the response duration on damage and ductility have been studied.

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Fatigue tests were carried out on 35 tensile plates with in-plane welded gussets of 200mm in length, with static tensile or compressive force applied to the gussets in horizontal direction. The specimens were tested in as-welded, stress relieved and overloaded conditions. The test results showed that the biaxial static forces had little effect on fatigue life, when the specimens were tested in as-welded condition. However, the compressive horizontal force prolonged the fatigue life of stress relieved specimens. The beneficial effect of overloads was deminished, when the tensile horizontal force was applied. These results were partly explained by stresses near the gusset ends computed by elasto-plastic mite element analysis.

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A new theory, which is based on the deflection theory and is applied to elasto-plastic analysis of suspension bridges, has been developed. It was found from the calculated results on ultimate strength of the main-cable and hanger system of simple-span suspension bridges that the safety factor of the individual members is not the same as that of the whole system, and that the system which has hangers with higher safety factors than that of maincables could improve the ultimate strength of the whole system. It is also found that the system designed by the live loads with the safety factors of 2.0 would have sufficient resistance towards large earthquakes.

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Orthotropic steel deck has been often used for long-span bridges because of its light dead weight. The Tatara Bridge, the longest cable-stayed bridge, uses orthotropic steel deck box girder. Orthotropic steel deck used for cable-stayed bridges carries live loads as a bridge deck but is an important structural member consisting main girder to which compressive force due to horizontal component of cable tension acts. In this paper, measurement of initial imperfection on an actual deck was made, then the compressive strength of continuous deck stiffened by trough ribs was analyzed by elasto-plastic finite displacement method thereby the applicability of proposed design method of column-model approach was evaluated.

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For the steel bridges and structures in the magnetic levitation (MAGLEV) guideway systems, electrically insulated connections must be used to reduce the magnetic drag forces acting on the MAGLEV cars. The objectives of this paper are to investigate the behavior of the insulated friction type connections and to establish their design method. Basic performance tests of connections with various kinds of insulating materials such as epoxy glasslaminate, inorganic zinc paint including potassium titanate and insulating sheet are carried out to choose an adequate material. Using the butt-type connections insulated by the chosen material, zero-to-tension cyclic loading tests are also carried out to certify their fatigue strength.

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We have constructed a neural network system for inferring axial force of high-strength bolts using wave-shaped data provided by a blow of automatic hammer. Using this system, we can get residual axial force of the bolts on actual bridges under service and installed axial force of the bolts on erection stage.
In this paper, we clear the relation between the property (e. g. grip length) of high-strength bolts and the inferred axial force. By adding the new information with respect to grip length of bolts into the input data of the system, the system could infer the axial force of bolts for various grip length and was tested for practical use in the case of various bolts on the joints and the secondary members.

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The present paper describes an application of Genetic Immune Recruitment Mechanism (GIRM) which is a combinatorial algorithm of Genetic Algorithm (GA) and Immune Recruitment Mechanism (IRM) founded upon the immune network model. The GIRM is applied to optimum disign problem of truss structure. As an optimization problem, diagonal member location design of truss structure with minimized weight is examined. Location of nodal points and major members, which are the upper and lower chords and the vertical members, are fixed. The problem is also solved by simple GA. From comparison of GIRM and the simple GA, effectiveness of the GIRM is shown.

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This paper presents an optimal location design of steel pipe pile foundation by using the genetic algorithm (GA). The pile diameter and thickness, the distance between each pile, number of pile column and number of each pile column are selected as the design variables, and the minimum cost is selected as the object function. The optimal design problem is formulated as the discrete optimization problem by erasing the distance between each pile from the design variables on the characteristics of the optimal solution. The GA with selecting the crossing strings is used to solve it with the specific coading for GA strings.

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High speed train imposes severe impact force on bridges. The magnitude of impact load has been analysed by modal superposition method, which indicates that. extremely high impact force occurs when the speed of train gets over 300km/hr. However, it isn't obvious whether this analysis method can apply properly in such case. In this study, boundary clement method analyses were applied in order to investigate the dynamic behavior of bridge while high speed train runs above it.

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Nonlinear dynamic response of a suspended small-sag cable driven by harmonic axial load and harmonic transverse load is presented. The basic equation of motion is solved by a Galerkin method for space co-ordinate and the averaging method for time co-ordinate. The single-degree-of-freedom approach is employed in this paper. The accuracy of the present solution is discussed at first. Then, nonlinear dynamic responses of a suspended cable are shown for various sag-to-span ratios, damping ratios and amplitudes of harmonic load.

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A nonlinear Tuned Liquid Damper (TLD) 3D-model has been developed to investigate the nonlinear characteristics of circular TLD by using the Boussinesq equation. The numerical results were compared with the experimental data obtained from shaking table experiments. The validity of the proposed model was confirmed by the results of those comparisons. The nonlinear effects of wave in circular tank to TLD fluid dynamic force were also made clear to investigate the response curves, the phase curves and the visualized photographs of the free surface deformations from the numerical results.

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Finite node-strip method is proposed for the free vibration analysis of long thin-walled structures with stiffeners and diaphragms. A node-strip element has nodal points as well as nodal lines of ordinary finite strip elements, so that it is easily to connect the element with finite elements. As a result, the versatility and capability of the strip method are particularly enhanced. Furthermore, the elements of stiffeners are formulated as off-set beams with the displacement functions of the node-strip element, and diaphragms are modelled with finite elements. The accuracy and efficiency of the present method is shown by several examples.

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Caisson slinging work using a large-sized floating crane in the Shirashima Oil Storage Terminal is difficult to conduct when the motion of the hull is strongly affected by waves. Sometimes, work must be interrupted or stopped. To solve this problem, the motion decreasing effect of the suspended load by installation of an active mass damper was investigated theoretically. To further reconfirm the effect of the damper, we carried out motion experiments in waves with a scale model about 1/40 the size of the actual floating crane. As a result, the active mass damper showed a remarkable control effect decreasing the motions of the suspended load due to waves to 1/3-1/2, verifying that theory and experiments for the active mass damper have good correlation.

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This paper presents a three dimensional dynamic analysis approach for the impact resistant design method of steel pipe check dam under the impact of huge rocks in the debris flow. First, the three dimensional elastic-plastic impact response analysis is developed by considering both local deformation and the strain-rate effect of steel pipe. Secondary, the impact resistant design procedure is developed by establishing the design criteria in which the response plastic rotation is compared with the limit plastic rotation capacity of the specified steel pipe member. Finally, this proposed design method is applied to the actual steel pipe check dam (so called B-type slit dam) and is compared with the current design method.

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Thus paper presents experimental and analytical approaches for the behavior of the model precast concrete guardfense (so called PGF) combined with PC wire and buried into the soil against a model car. First, the impact test is performed for the model PGF by using the pendulum impact apparatus. It is found from the test that the semi-fixed type PGF (especially not having footings) has the shock softening effect rather than the fixed type PGF. It is also noted that the impact energy is shared by the displacements of 5 PGF pieces around the impacted point. Second, the impact response analysis of PGF is performed by the rigid body-spring method. It is found that the analytical approach can simulate well the experimental results.

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A method is proposed to construct hysteresis models for thin walled steel bridge piers of single degree of freedom. The models have been obtained from static as well as quasi-static tests done in Nagoya University during the past several years. The developed models are first used to simulate the pseudo-dynamic test results. Then the models are applied to clarify the seismic behavior of steel bridge piers under the 1995 Hyogoken-nanbu earthquake. It has been found that the earthquake accelerogram recorded in Japan Meteorological Agency during the quake is a tremendously severe wave for short bridge piers or bridge piers with low natural periods.

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Although performance of steel structures has been fairy well due to ductile material properties, during the Hyogoken-nanbu Earthquake (M=7.2), occurred at 5:46, 17th January 1995, various types of damages were found among steel structures and the elastic-plastic dynamic buckling induced through the seismic excitations is recognized as one of the most important problems in seismic design. The purpose of this paper is to describe a method of elastic-plastic large displacement analysis for buckling analysis of shells of revolution, and to discuss about the dynamic buckling characteristics of a steel circular pier comparing the computational results with the observed phenomena in Kobe City.

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In this paper the response reduction effect of a wave impeding block (WIB) was investigated when it was build under a focused structure or near it in order to impede incoming waves induced by source vibrations. The parameter studies were conducted on the WIB width and thickness in view of the concerned wave field. The wave propagation/ impdediment were detailed in the transient response for a Ricker-wave form loading. The computation was based on the hybrid method of the FEM for the surface soil including the WIB, and the BEM for the underlain halfspace. An extended application was demonstrated for a building vibration reduction by the passive type WIB as well as by the active type WIB.

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Liquefaction occurred in most of reclaimed lands in Hanshin area during the Hyogo-Ken-Nanbu Earthquake, January 17, 1995. Such lands are made of weathered granite, “Masa-do”, which has been believed anti-liquefiable. Authors carried out many cases of shaking table tests to model ground set up in shear container with erupted “Mass-do” under horizontal and vertical excitation. Objectives of the experiments are to simulate the actual behavior of reclaimed lands for the following issues; (1) liquefaction and settlement characteristics, (2) influence of vertical excitation, (3) ground motion amplification, and finally to evaluate the ground motion in both aspects of liquefaction and seismic design code. The test results can elucidate an outline of the actual liquefaction behavior.

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This paper presents a probabilistic method for estimating the minimum power loss of secondary transmission systems in a seismic event. First, the power loss was defined. Second, a state-of-the-art study for a system switching method was described and an algorithm was proposed on the basis of Genetic Algorithm (GA) and Monte Carlo simulation. Third, it was indicated that the developed method was an effective means of seismic-reliability analysis for secondary transmission systems. Finally, this method was applied to a seismic reliability analysis of a real secondary transmission system in Kushiro, Hokkaido, Japan.

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The volcanic disaster of Mt. Fugen in Unzen erupted November 17th 1990 are prolonged and enlarged more than four years. Disaster prevention officials of lifeline systems, recognized the danger of the mountain eruption and considered a counterplan to protect their facilities. They also considered emergency and permanent restoration plans after debris flows and pyroclastic flows attacked their facilities.
In this paper, emergency counter plan, damage and both temporary and permanent restoration plans of lifeline systems to volcanic disaster of Mt. Unzen are reported and discussed. Problems which now have to be solved as well as some lessons to be learned are also explained.

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