Showing papers in "Doboku Gakkai Ronbunshu in 1985"
TL;DR: In this paper, the use of spatial variability in the material properties of concrete in a finite element analysis (FEA) was investigated, and the following methods are implemented and have been assessed on their performance: • Covariance Matrix Decomposition method (CMD) • Fast Fourier Transform method (FFT) • Local Avarage Subdivision method (LAS) • Expansion Optimal Linear Estimation method (EOLE)
Abstract: With more advanced methods and increasing computational power, the simulation of reinforced concrete in a Finite Element Analysis (FEA) has become more and more realistic. In a nonlinear analysis of reinforced concrete, cracking behaviour and the maximum load-capacity can be determined. Such analyses sometimes suffer from unstable behaviour, especially when large parts of the structure crack at the same time. It is expected that spatially varying concrete material properties will affect crack initialization, crack patterns and the stability of the analysis. In this report, the use of spatial variability in the material properties of concrete in a Finite Element Analysis (FEA) was investigated. To incorporate spatial variation in the Finite Element method (FEM), discretized random fields are used which are assigned to elements or integration points in the Finite Element (FE) model. In this research the following methods are implemented and have been assessed on their performance: • Covariance Matrix Decomposition method (CMD) • Fast Fourier Transform method (FFT) • Local Avarage Subdivision method (LAS) • Expansion Optimal Linear Estimation method (EOLE) To be appropriate for the implementation in a general purpose FEM program the method has to be efficient with respect to computation time, accurate in representing the statistical characteristics of concrete and easy to implement in the program. In a literature review, a large variation was found in the used values for the statistical characteristics which are involved in the modelling of the spatial variation of concrete properties. In the assessment of the random field generators this range of values was used as input. From literature and the assessment it was found that the CMD method is easy to implement and is the most accurate in representing the statistical characteristics of concrete. With respect to efficiency, the method performs poorly when the number of nodes increases. This is the case for random fields in multiple dimensions and/or for random fields with a small correlation length. The FFT method is slightly less accurate but performs very well with respect to efficiency when the number of nodes increase. The derivation of the one sided Spectral Density Function (SDF), which is needed in the FFT method, is however quite difficult. The threshold value in the correlation function and the distribution type have the largest influence on the accuracy of the random field. If the threshold value increases, and a log-normal distribution type with a high coefficient of variation (COV) is selected, the accuracy of the different methods decreases. The FFT method is slightly more accurate in representing the statistical characteristics in that case. With a large correlation length and a threshold value, the values in the random field are strongly correlated. It was found that in such a case the assumption of ergodicity does not hold any more.
36 citations
Abstract: Multiple regression analyses of duration of earthquake ground acceleration are presented Duration is defind as the time interval between the time when accleration amplitude firstly exceeds a times (0
23 citations
TL;DR: In this article, a series of laboratory model tests and two different types of finite element analyses were performed to obtain basic data served to the field measurements and the design methods of sandy ground tunnels, and the use of joint elements was found to be more effective than of usual elasto-plastic elements to describe the discontinuous movements occured in sandy ground due to tunneling.
Abstract: To obtain basic data served to the field measurements and the design methods of sandy ground tunnels, a series of laboratory model tests and two different types of finite element analyses were performed. In the case of shallow overburden, large displacement took place even at the ground surface, while the larger displacement zone reduced its size when the overburden became deeper. The use of joint elements in the analyses was found to be more effective than of usual elasto-plastic elements to describe the discontinuous movements occured in sandy ground due to tunneling.
22 citations
TL;DR: In this article, the unstable failure of specimens was discussed from viewpoint of catastrophic theory, and a new system to measure automatically the load-displacement curves having falling branch was proposed.
Abstract: A stiff testing machine is generally used to measure load-displacement curves having falling branch of concrete specimens. However, when the failure of specimens is unstable (uncontrollable), the stiff testing machine is insufficient to measure the load-displacement curves having falling branch. In this paper, the unstable failure of specimens was discussed from viewpoint of catastrophic theory, and a new system to measure automatically the load-displacement curves having falling branch was proposed. The load-displacement curves of compressive specimens (∅10×20cm) of high strength concrete and high strength light-weight concrete were measured by the new system.
22 citations
TL;DR: In this article, the ultimate strength of thin-walled box stub-columns with the longitudinal stiffeners subjected to compression and bending was evaluated under the conditions of uniaxial and eccentrical compressions.
Abstract: This paper presents the experimental study on the ultimate strength of thin-walled box stub-columns with the longitudinal stiffeners subjected to compression and bending. Eight columns were tested up to failure under the conditions of uniaxial and eccentrical compressions. These results were arranged from various point of views and the ultimate strength was plotted as the interaction curves of compression and bending. By introducing a plate slenderness for the stiffened box stub-columns, an empirical formula for evaluating their ultimate strength was proposed herein.
17 citations
16 citations
TL;DR: In this paper, the deformation behavior of thin-walled welded box beams under cyclic bending was studied and two simple models were introduced to predict analytically the cyclic moment-curvature curves of the beams.
Abstract: This paper presents a study on the deformation behavior of thin-walled welded box beams under cyclic bending. The specimens are tested under two-point load bending to have a uniform moment occur in the central segment of the beam. Two different simple models are introduced to predict analytically the cyclic moment-curvature curves of the beams. The numerically obtained stress versus strain curves of plate elements are utilized to calculate the moment-curvature curves.
16 citations
TL;DR: In this article, the authors report the test results of twelve curved model girders subjected to the combined loads of bending and shear by changing radii of curvature, aspect ratio and slenderness ratio of web plates as well as stiffness of longitudinal stiffeners.
Abstract: This paper reports the test results of twelve curved model girders subjected to the combined loads of bending and shear by changing radii of curvature, aspect ratio and slenderness ratio of web plates as well as stiffness of longitudinal stiffeners. Through the collapse tests. buckling and ultimate strength of curved girders are investigated as the interaction curves of bending and shear. For the ultimate strength. two interaction curves are proposed, i. e. one is a theoretical curve taking accounts of the reduction of ultimate strength for bending due to warping stresses on the curved flange plates and the other is experimental one based upon our past test researches on pure bending and pure shear.
14 citations
TL;DR: In this article, a theoretical study on the ultimate strength of thin-walled box stub-columns subjected to compression and bending is performed by using a finite element method (F. E. M.) on the basis of the elastoplastic large deflection theory in order to develop an interaction curve at the ultimate state.
Abstract: A theoretical study on the ultimate strength of thin-walled box stub-columns subjected to compression and bending is performed by using a finite element method (F. E. M.) on the basis of the elasto-plastic large deflection theory in order to develop an interaction curve at the ultimate state. A modified column method to calculate the ultimate strength of thin-walled box columns considering the local bucking of Plate elements is proposed by using the interaction curve of stub-column. Through numerous calculations by the modified column method, an approximate formula for predicting the ultimate strength of thin-walled box columns is given in this paper.
13 citations
TL;DR: In this paper, the effect of in-plane shear stress on the fatigue strength of a thin-walled plate girder is investigated and it is shown that fatigue cracks may form along the web boundaries in regions where the tension field is anchored.
Abstract: When a thin-walled plate girder is subjected to repeated shear, it is possible that fatigue cracks may be initiated along the web boundaries in regions where the tension field is anchored. They are caused by the secondary bending stress which is produced by out-of-plane deformation of the web. In this paper, first, the out-of-plane deformation and the secondary bending stress of a rectangular plate under in-plane shear are examined by the finite element analysis. Secondly, using the relation between in-plane shear stress and secondary bending stress, the fatigue strength is expressed in terms of the in-plane shear stress as a function of the web slenderness ratio. And the influence of various factors on the fatigue strength is discussed.
13 citations
TL;DR: In this paper, a simplified simulation model for predicting two-dimentional beach transformation was developed based on the recent results of research works on wave transformation, near bottom velocity and sediment transport.
Abstract: A simplified simulation model for predicting two-dimentional beach transformation was developed based on the recent results of research works on wave transformation, near bottom velocity and sediment transport. The wave field was calculated by the energy flux method based on either cnoidal or linear wave theory in the offshore zone, and by Mizuguchi's energy dissipation model in the surf zone. The velocity field was calculated by the approximate method of Koyama and Iwata using the cnoidal wave profile or by linear wave theory. The sediment transport formula of Shibayama and Horikawa, which includes the effect of suspended sediment caused by vortices created in the vicinity of ripples, was used to calculate transport rates. The model was found to give reasonable results. The results were compared with various laboratory data and the feasibility of the model was discussed.
TL;DR: In this paper, a model for estimation of basin-wide snow water equivalent using snow covered area is presented, and the results of the application of the model to five basins are in good agreement with observed data.
Abstract: In this paper a model for estimation of basin-wide snow water equivalent using snow covered area is presented. At first the relation between percent snow cover and snow water equivalent is made clear using topographical characteristics of some Upper-Tone basins and the snow distribution obtained by surveying the Takaragawa basin. The dependence of snow water equivalent to altitudinal distribution of a basin is determined using snow covered area and hydrological data. The results of the application of the model to five basins are in good agreement with observed data.
TL;DR: In this article, the ultimate strength of steel plate elements in the concrete filled square steel tubular columns is analyzed by using the F. E. M. based on the elastoplastic and large displacement theory, and it is found through numerous parametric analyses that the influence of restrictions due to the concrete core upon the boundary conditions concerning the inplane displacement of the steel plate element along the unloaded edges is tought to be negligible in an ordinary composite column.
Abstract: In this paper, the ultimate strength of steel plate elements in the concrete filled square steel tubular columns is analyzed by using the F. E. M. based on the elastoplastic and large displacement theory. It is found through numerous parametric analyses that the influence of restrictions due to the concrete core upon the boundary conditions concerning the in-plane displacement of the steel plate element along the unloaded edges is tought to be negligible in an ordinary composite column. Furthermore, it is difficult to prevent the local buckling of steel plate elements by the shear connectors, even when they are sufficiently welded on the plate elements and anchored into the concrete core. A tentative design method is proposed by adopting a simplified ultimate strength curve and a column model approach using an effective stiffener which consists of a plate element and a longitudinal stiffener for unstiffend and stiffened steel plate elements, respectively.
TL;DR: In this paper, two earthquake motion prediction models are developed, one (EMP-IB Model), a prediction model for given magnitude and epicentral distance, and the other (EMPIIB Model), an advanced model which deals with the effect of successive faulting and relative site locations on ground motion characteristics.
Abstract: Nonstationary earthquake motion prediction models are proposed on the basis of rock surface-ground motion dataset. Ground motions on rock surface with the shear velocity of 600-700m/sec are dealt with. The ninety-one components of acceleration time histories on rock surface level are arranged, which consist of (i) rock surface-ground motions estimated from the accelerograms recorded on alluvial and diluvial sites, (ii) rock surface-ground motions modified from bed rock ground motions, and (iii) ground motions recorded on rock surface. On the basis of this dataset, two earthquake motion prediction models are developed, one (EMP-IB Model), a prediction model for given magnitude and epicentral distance, and the other (EMP-IIB Model), an advanced model which deals with the effect of successive faulting and relative site locations on ground motion characteristics.
TL;DR: In this paper, the authors have carried out experimental and theoretical studies to clarify the above problems, and give how to design the demolition works with the agent and how to estimate the amount of the expansive pressure acting on the inner surface of the holes and mechanism of fracture of materials demolished.
Abstract: Recently in Japan, some chemical expansive materials have a tendency to be used for demolition of rock-like materials, old concrete structures etc. Those are called as “expansive demolition agent”. With the agent. demolition work can be done in safety without sound. vibration and any other pollution. since high expansive pressure is obtained gradually by only mixing the agents with water and pouring the sully into bored holes. In order to estimate the time for demolition works, it is necessary to clarify the amount of the expansive pressure acting on the inner surface of the holes and mechanism of fracture of materials demolished. The authorsi carried out experimental and theoretical studies to clarify the above problems, and give how to design the demolition works with the agent.
TL;DR: In this paper, a method for predicting surface failures which occur during heavy rainfall on granite mountain slopes is proposed by using the digital land form model that is obtained by reading altitude on a topographical map at 10m grid point space.
Abstract: A method for predicting surface failures which occur during heavy rainfall on granite mountain slopes is proposed by using the digital land form model that is obtained by reading altitude on a topographical map at 10m grid point space. A depth of a potential failure layer is assumed at each grid point. In the layer, an infiltrated water movement from cell to cell is modeled in the study (cell is a square of the grid). Infiltrated ground water levels which show the three dimensional effects of a topographical factor in an area can be hourly calculated at every cell by the model. The safety factor of every cell is also calculated every hour by the infinite slope stability analysis method with the obtained infiltrated ground water level.Failure potential delineation is defined here as the time when the safety factor becomes less than unity under the assumptions that the depth of the layer is 1.2m and effective rainfall, 20mm/hr, continues 50 hours. More hazardous cells are found to appear at the sites where mountain slope failures occurred in the past time.
TL;DR: In this paper, the authors evaluate the road roughness, its influence on riding comfort and point out possible methods for understanding a correlation between roughness and the resulting vehicle dynamics, and apply regression analysis to investigate a linear relationship between the road profile elevation spectral density and the equivalent acceleration excitation to a vehicle.
Abstract: The purpose of this paper is to evaluate the road roughness, its influence on riding comfort and to point out possible methods for understanding a correlation between road roughness and the resulting vehicle dynamics. First, statistical measurements of actual road roughness in summer and that in winter are carried out and its effect on riding comfort is discussed in comparison with ISO standard 2631. Based on the measurements, the road roughness characteristics can be represented by road roughness model functions. Second, regression analysis is used to investigate a linear relationship between the road profile elevation spectral density and the equivalent acceleration excitation to a vehichle. In addition, vibration source contribution method is applied to the prediction of the vibratory response of the vehicle from road roughness. As a result, significant results are obtained.
TL;DR: In this paper, a finite displacement theory of naturally curved and twisted rods undergoing finite rotations is developed, where the twist and curvatures after deformation are expressed in terms of four parameters without using small-strain assumptions.
Abstract: The object of this paper is to develop a finite displacement theory of naturally curved and twisted rods undergoing finite rotations. Particular attention is paid to investigate the coupling of finite rotations in space under the Bernoulli-Euler hypothesis. A finite rotation vector is employed to derive the displacement field available for finite rotations. A new variable is introduced as a fourth parameter associated with rotations of cross sections. Then the twist and curvatures after the deformation are expressed in terms of four parameters without using small-strain assumptions. The equilibrium equations and the associated boundary conditions, in which second order terms with respect to displacement components are fully taken into account, are derived from the principle of virtual work. The accuracy of the present equilibrium equations are confirmed through comparisons with those obtained by the equilibrium method.
TL;DR: In this paper, the effect of free surface plays an important role on the flow structure in open channel flow, where secondary flow consists of the free-surface vortex which includes the horizontal flow from the side wall to the center of channel and the bed-wall vortex which pairs with the free surface vortex.
Abstract: In actual open channel flow, secondary flow is always generated near the side wall even in straight channel and this seems to influence the flow structure. In this study. secondary flow and turbulent structure in a rectangular open channel flow were investigated experimentally. As the results. secondary flow consists of the free-surface vortex which includes the horizontal flow from the side wall to the center of channel and the bed-wall vortex which pairs with the free surface vortex. These vortices interact with the primary flow and dominate three dimensional flow structure. The differences between open and closed channel flows are remarkable and therefore the effect of free surface plays an important role on the flow structure in open channel flow.
TL;DR: In this article, the authors describe the way to find key blocks in the systems of joint networks and to support them by bolting or other suppoting methods, and propose an idea of a key block existing space which contains all key blocks.
Abstract: A number of analytical tools are available for engineering calculations involving excavations. These include numerical methods, physical model techniques and limit equilibrium analysis. Block theory is new and it uses the stereographic projection. It can be applied to analyze the three dimensional system of joints and other rock discontinuities to find the critical blocks of the rock mass when excavated along defined surfaces. This paper describes the way to find key blocks in the systems of joint networks and to support them by bolting or other suppoting methods. For a severly jointed rock mass, an idea of a key block existing space which contains all key blocks in the excavated rock surface is proposed and it is used for determining the optimum support forces which stabilize such jointed rock mass.
TL;DR: In this paper, a new formulation of the governing equations for the finite displacement beam theory is presented, which considerably simplifies the derivations through the principle of virtual work, and can be easily obtained even for the exact theory under beam assumptions.
Abstract: The governing equations for the finite displacement beam theory are often formulated through the principle of virtual work by introducing the pertinent kinematic field with displacement components defined in terms of the coordinates fixed in space. However, this formulation can hardly be applied for the theory of space beam without any restrictions on the magnitude of displacements, since the kinematic field becomes highly nonlinear largely due to the finite rotations in space.This paper presents a new formulation which considerably simplifies the derivations through the principle of virtual work. By the formulation, the governing equations can be easily obtained even for the exact theory under beam assumptions.
TL;DR: In this article, an analytical study on the ultimate strength of intermediate transverse stiffener in the web plate of horizontally curved girders is presented, based on the theory of shallow shell and collapse model.
Abstract: This paper presents an analytical study on the ultimate strength of intermediate transverse stiffener in the web plate of horizontally curved girders. Firstly, the shear buckling strength is analyzed by the theory of shallow shell. Secondly, the ultimate shear strength is also inquired through the collapse model. Based upon these analyses and some experimental data, the behaviors of the transverse stiffener are discussed. Finally, a beam-column model for evaluating the strength of the transverse stiffeners is proposed and a design recomendation to determine the strength and corresponding rigidity of the transverse stiffeners of curved girders in the ultimate state is given by this paper.
TL;DR: In this paper, the live loads for fatigue design and maintenance of highway bridges are studied based on computer simulations, where the type of vehicle, the vehicle weight and the array and headway of vehicles are cosidered as random variables.
Abstract: The live loads for fatigue design and maintenance of highway bridges are studied based on computer simulations. Simulations of traffic live loads are carried out under various traffic volumes and constitutions of vehicle types. The type of vehicle, the vehicle weight and the array and headway of vehicles are cosidered as random variables. Bending moment responses of simply-supported one-lane girders of various lengths are calculated under usual traffic conditions. Moment ranges are analysed by using the rain flow method. For the evaluation of fatigue damage, the equivalent moment range and the reduced number of L-20 or T-20 live load are presented.
TL;DR: In this article, the ultimate strength of stub-columns with initial imperfections and residual stresses is investigated using a finite element method (F. E. M.) based on elasto-plastic large deflection theory.
Abstract: This paper concerns the ultimate strength of thin-walled box stub-columns designed to fail by interactive plate buckling between the plate elements rather than by overall column buckling. An experimental study is described, conducted using nine stub-column specimens. The ultimate strength of stub-columns with initial imperfections and residual stresses is investigated using a finite element method (F. E. M.) based on elasto-plastic large deflection theory. Finally, two simplified design methods are proposed for evaluating the ultimate strength of stub-columns.
TL;DR: In this paper, a model for estimation of snowmelt distribution using insolation, air temperature and precipitation is presented, which includes net radiation, degree hour approach and condensation and convection in a rainy day.
Abstract: In this paper a model for estimation of snowmelt distribution using insolation, air temperature and precipitation is presented. This model includes net radiation, degreehour approach and condensation and convection in a rainy day. At first the model is determined at the observational base. And it is applied to the slopes and the forested area. The results of the application of the model to the base, the slopes and the forested area are in good agreement with observed data.
TL;DR: In this article, multiple regression analyses for vertical peak ground motions (peak ground acceleration, peak ground velocity and peak ground displacement) and absolute acceleration response spectra with damping ratio of 5% of critical are presented.
Abstract: Multiple regression analyses for vertical peak ground motions (peak ground acceleration, peak ground velocity and peak ground displacement) and absolute acceleration response spectra with damping ratio of 5% of critical are presented. Employed were 119 sets of vertical strong motion acceleration records obtained at 53 free field sites in Japan. Empirical formulae of these characteristics in terms of earthquake magnitude and epicentral distance are proposed for three subsoil conditions. Peak ground motions and absolute acceleration response spectra of vertical components were compared with those of horizontal components, and characteristics of vertical components were discussed in comparison with the characteristics of horizontal components.