Though the segregation resistivity is a critical property for high-fluidity concrete, it has not been evaluated quantitatively. The degree of segregation between coarse aggregate and mortar is evaluated by observation only, and the quality control method for segregation is not established. In the experimental study, the flowing segregation test of matrix mortar was carried out, and the flowing segregation resistance of mortar was examined quantitatively on the basis of rheology as a viscoplastic property, expressed with softness and viscosity. The availability of the evaluation method and the influencing factors of segregation resistance were also discussed. The experimental study reveals that, compared with average specific resistance method, the plastic viscosity and the yield value of flowing segregation are in closer relationship with the segregation property of matrix mortar. The yield value is associated with the cohesion toughness of matrix mortar, and the plastic viscosity with the viscosity. Segregation degree is comparable with the results of the cylidrical penetration test.
This paper describes cracking in full scale window opening walls made of several types of concrete. Five types of concrete walls were constructed; concrete walls made of, normal strength concrete(about 30MPa), steel fiber reinforced concrete, high-strength concrete(about 60MPa), high-strength concrete with silica fume(about 70MPa) and normal strength concrete with reinforcing bars placed at the corners of the window opening. The effect of the concrete strength, steel fiber and reinforcing bar on arresting the crack propagation in concrete walls was investigated experimentally. The results showed that steel fiber and reinforcing bars were effective in arresting the crack propagation in concrete walls, on the other hand, the high strength concrete was not effective. This may indicate that the ductility performance of concrete strongly affects the crack propagation.
The influence of loading speed on the fracture properties of fiber reinforced mortar was investigated. Three-point bending tests on pre-notched beam specimen were performed under the four different loading speed conditions. Fracture parameters of specimen were analyzed based on the poly-linear approximation analysis of tension softening diagram by using the data of a load-load point displacement curve. The fracture energy of specimen was significantly improved by mixing short cut fibers in mortar matrix. The fracture energy and the maximum load increase at the high loading speed condition and this is conspicuous in the case of the fiber reinforced mortar. The reason of this loading effect is considered that the high loading speed causes the increase of crack resistance in the fracture process zone of specimen.
This paper presents an analytical method for simulating the transportation of air born chloride-ions near coastal area. The initial condition for analyzing the convective diffusion equation is obtained by using the measurements of air born chloride-ions at four points located at sea-shore in Okinawa. Then, the convective diffusion equation is solved by the finite element method with the initial condition mentioned above and the boundary conditions. The analytical solutions are compared with the field data at 8 different locations and this gives very close agreement. From these results one can confirm that the proposed method is effective and applicable in evaluating the durability of reinforced concrete buildings near coastal area.
To prevent staining and efflorescence thought to be caused by the migration of water containing staining agents and soluble salts in stone, it was considered that the migration of the water in the stone must be controlled. It was believed that this could be achieved by treating stone surfaces with a barrier penetrant which has water repellency. Experiments testing five parameters were carried out. Although the scope of this research covered short term observation of the effect of barrier penetrant treatment and long term stain prevention was not confirmed, on granite the silicone type acrylic derivative polymer barrier penetrant and the alkyl-alkoxy silane type barrier penetrant were seen to prevent changes in appearance and to prevent efflores- cence. Staining and efflorescence of stone for buildings occurs frequently and a solution to these is urgent for stone work quality assurance. Knowledge obtained in this research is essential information.
Applications of carbon fiber reinforced concrete (CFRC) to various building materials have been progressed because of its excellent mechanical characteristics. The conventional CFRC made of mortar with no coarse aggregate has some defects such as large drying shrinkage and low modulus of elasticity, which will be reduced by substituting concrete-mix including coarse aggregate for the mortar. In this study, in order to develop the CFRC using concrete-mix, experimental investigations were conducted concerning evaluations of an optimum mix proportion and various mechanical characteristics of the CFRC. As the results, it was shown that the CFRC of concrete-mix was superior in modulus of elasticity, flexural and fracture toughnesses to that of the mortar-mix and the mechanical characteristics of the former was, if anything, similar to those of steel fiber reinforced concrete.
The purpose of this study is to consider the validity of the visual judgement of slipperiness of floors for the purpose of prevention of accident such as tumble. First, we carried out sensory tests using samples, on which surface substances exist as a whole or partially or not. Next, we made sensory scales of visual judgement of slipperiness of floors and of existence of substances adhered to floors, and measured coefficient of slip resistance named C.S.R (Coefficient of Slip Resistance) by means of slip meter named "0-Y-PSM". Then, we showed that visual judgement of slipperiness of floors wasn't proper . As a result, we showed that it is suitable method to adopt roughness to floor surfaces and to keep floors clean, for the purpose of prevention of accidents.
The objective of this study is to understand physical mechanism of the effects of corner modification on aerodynamic characteristics of a type of square cylinder. Especially, we focus on dependency on the following parameters : the shape of corners, the characteristics of approaching flows and dimension of the model. We carried out wind tunnel tests for the measurements of the aerodynamic forces, such as averaged and fluctuating components of lift and drag forces, which act on a 2D or a 3D square cylinder with chamfered or rounded corners in smooth or homogeneous turbulent flow. Also, in order to confirm the flow structures under above condition, 3D numerical simulations are performed for a 2D cylinder in smooth flow.
Behaviors of structures during an earthquake are dominated by the accumulation and rate of input energy in frequency domain as well as in time domain. However, such energy parameters have not been related to time-frequency characteristics of earthquake ground motions. This paper proposes a wavelet analysis as a tool to clarify the relationships between time-frequency characteristics of earthquake motions and behaviors of structures. First, the relationships between wavelet coefficients deduced from wavelet transform and time history of energy input are derived. Then, the proposed time-frequency analysis is applied to the motions recorded during the 1995 Hyogoken-nanbu Earthquake, which reveals the relationships between epicentral distance and input energy both in frequency and time domains.
The seismic risk of multi-degree-of-freedom (MDOF) structures was evaluated. The factors which represent the non-linear response of MDOF structures are evaluated by non-linear response analyses using simulated ground motions which take into account the variation of response spectra. The non-linear response is affected by the magnitude of the earthquakes and ground conditions. The factors are incorporated into attenuation equations of earthquake response spectra and the probability of damage of seven structures was evaluated. The variations of damage evaluation equations are almost the same as those of the attenuation equations of response spectra. The seismic risk analysis of structures considering earthquake occurrences around a construction site, ground conditions of the site, and the relationship between non-linear response and input motions is possible by this method.
Modified k-ε model Aerodynamic properties of rectangular cylinders having infinite spanwise length with various breadth/depth ratio ranging from B/D=0.6 to 8.0 were investigated numerically by two-layer k-ε model with modification on k-production term. Although present numerical approach is two-dimensional, a physically reasonable smooth periodic vortex shedding was obtained even in the range of high Reynolds number, which can not be simulated by the ordinary simple 2D analysis which is not incorporated with any turbulence model. Various typical aerodynamic features were successfully obtained particularly including discontinuity in Strouhal number at critical section of B/D=2.8 and 6.0. Also, for various B/D ratios, drag coefficients and mean surface pressure distribution were in good agreement with experiments and three-dimensional analysis. However, for the prediction of fluctuation in pressure and forces, since the periodic component can only be taken into account by RANS model and due to lack of its ability to assess the stochastic component, total fluctuation in surface pressure and aerodynamic lift force were considerably underestimated in some cases compared with experiments and 3D analysis.
This paper investigates the characteristics of the wind-induced responses of high-rise buildings with the eccentricity. A wind tunnel experiment has been conducted on 6-mass-point aeroelastic models of a high-rise building with a side span ratio of 2 and an aspect ratio of 5. The experimental results are compared with analytical results by a modal spectrum analysis using the wind force obtained from a dynamic balance over the applicable range of the analytical method without the motion-induced wind force. The aerodynamic damping during vibration from the auto correlation function of the response acceleration for the primary and tertiarymode, where across-wind vibration and torsional vibration is dominant respectively, are also obtained.
This paper describes a dynamical analytic study concerning soil-structure interaction problems in case of structure embedded in an soil ground. The analysis is performed on basis of two-dimensional wave propagation theory inwatersaturatedsoilground. In this paper are derived the sets of governing equations of soil-structure interaction system subjected to base rock excitation. The following conclusion may be drawn from the present numerical examples: (1)The interaction effect between water saturated soil ground and the structure increases with lower permeability in aggregate body. (2)When the structure is subjected tobase rock motion, the dynamic earth pressure depends on excitation frequancy. (3)If the structure with smallaspect ratio is pertinently buried insoil ground, the rotational response of it could be been minimum. (4)The effect of embedment is to increase the soil resistance to motion of the structure.
The authors present a method to evaluate ground motions at a site which is based upon the site specific experimental spectral amplitude and phase characteristics for horizontal and vertical ground motions based on records at the observed site. The time domain characteristics are now given by the site specific phase spectra rather than a standardized envelop curve in time domain which has been a common practice to obtain time history. The recorded motions in Japan are used to obtain the synthesized Green's functions and predicted waves by summing this Green's functions were compared well with the recorded motions including 1995 Hyougo-Ken-Nanbu earthquake. The method is expected to expand the ability of estimation of strong ground motions to vertical motions to improve the phase characteristics.
Experimental system for seismic response control is described. This system consists of a full-scale steel frame, shakers of active mass type and measurement system. An earthquake response generator system using shakers is explored to realize earthquake responses on the full-scale structure as if it were subjected earthquakes. On the basis of the modal control theory, an algorithm to control the shakers is formulated. After confirming the validity of the algorithm for generating earthquake responses by simulation analysis, this earthquake response generator system is applied into vibration tests of the full-scale structure. Observed acceleration responses of the full-scale structure in these tests are compared with calculated responses under the earthquakes. Results demonstrate the accuracy and validity of the earthquake response generator system. It is emphasized that by making use of this experimental system, the control performance of seismic response control on full-scale structures can be examined like shaking table tests.
We estimate strong ground motions in Kobe during the Hyogo-ken Nanbu earthquake of 1995 by using a three-dimensional (3-D) basin structure. A 3-D finite difference method with fourth ordered staggered-grid scheme developed by Graves (1996) is used. We first calculate bedrock motions generated by the inverted source model of Wald (1996) to see how well it can reproduce the observed bedrock motions. A realistic 3-D basin model is then constructed based on the exploration data and is used to calculate synthetic motions. We found that Wald's source model reproduces observed waveforms only in the long-period range, where the basin-edge effect does not contribute much. To make the input motion more realistic we convolve the synthetic bedrock motion with the bedrock motion inverted from the observed record at JMA. The resultant synthetic waveforms on the surface of the 3-D basin are very similar to the observed and the contribution of the edge effect becomes almost the same order as that of the direct S-wave. It means that both the deep 3-D basin structure and the detailed rupture process of the fault have to be taken into account to simulate the strong ground motions quantitatively.
The effects of lateral irregularities of interface between layers on surface ground motions are investigated using the finite element analysis. The equivalent wave velocities and 1/Q values identified under the assumption of a stratified layer are evaluated in the case of sine-shaped and stochastic undulated interface models. The convex interface increases equivalent wave velocity and 1/Q value, but the concave interface shows the opposite effects. These effects depend on the average and bounds of the depth of a layer, and the lateral wavelength of a sine-shaped interface. The equivalent wave velocities and 1/Q values are approximately normally distributed and depend on mean and variance of the depth of layer for stochastic interface model. If artificial neural networks inputting the normalized depths in the vicinity of an estimated point learn the analytical results, the equivalent wave velocities and 1/Q values are evaluated automatically. The distribution of influenced horizontal range of lateral interface irregularities is considerably different between the equivalent wave velocities and 1/Q values.
Active mass damper (AMD) systems have been used in actual buildings to reduce vibrations of buildings during strong winds. The AMD systems have a feasibility of controlling buildings even during severe earthquakes. To develop algorithms that can control the AMD within its stroke limitation is an important problem in order to apply the AMD system to seismic response control for severe earthquakes. The algorithm with variable control gain formulated in this paper is based on a pole assignment. In the algorithm, a damping factor of the assigned pole is given as a parameter of the control performance. The parameter is adjusted according to an index associated with activity of the AMD so as to prevent its excessive behavior. A full-scale five-story test structure equipped with an AMD system and an earthquake response generator system was employed. This study demonstrates experimentally the effectiveness of the proposed algorithm in reducing the structural responses and in controlling the AMD within its stroke limitation.
Many pile foundations were severely damaged by soil liquefaction at the Port Island during the Hyogo-ken Nanbu Earthquake, January 17, 1995. The objective of this study is to investigate the responses of a pile foundation in the liquefied soil by the difference of input earthquake motions. Earthquake response analyses of a structure on pile foundation are conducted using the numerical model that takes into account the effect of excess pore water pressure. Two earthquake waveforms, which have the different cyclic characteristics, are employed as an input motion. These analytical results indicate that bending moments of pile are affected by the difference of liquefaction process due to the cyclic characteristics of input earthquake motion.
Excavation in soft ground may cause notable deflection of an earth retaining wall, reaching to a considerable depth. This mode of lateral load distribution can not be predicted by the conventional design technique. This paper compiles the forty cases of deflection of earth retaining wall as observed in soft ground, and seeks inversely for the load distribution to explain the observed mode. Regarding the first stage of excavation, for example, it was found out that the depth of maximum lateral load must be taken two or three times as deep as the excavation bottom to explain the observed data.
Concern about kinematic instability in tension structure is imperative. This kind of structure contains one or more infinitesimal mechanisms, and external loads cannot be supported without geometrical changes. For this reason, geometrically linear analysis cannot be applicable. This paper proposes the concept of a virtual spring which is equivalent to the stiffness in the infinitesimal mechanism direction due to the prestressing in the structure. And, the systematic techniques for appending the virtual spring into the kinematically unstable structure is developed. Virtual spring can remove the kinematic instability of the structures, and geometrically linear solutions (e.g. eigen values) can be obtained.
Buckling of axially compressed cylinders is studied using a fully nonlinear Ritz solution procedure. An axisymmetric geometric initial imperfection mode is chosen as to be of the inverse mode to the linear axisymmetric deflection mode, and is shown to increase the buckling load carrying capacity. Adopting non-axisymmetric imperfections, the loss of load carrying capacity and membrane energy occurs. The relationship between these nonlinear results and a reduced stiffness criterion is discussed.
If we joint two glued laminated timbers using finger joint as the fiber lines of these members being parallel, we have a lot of experimental data on mechanical property of these members with finger joints. But, the mechanical property is not yet clarified when the fiber lines of two members are not parallel. We conducted some experiments on moment resisting finger joint of glued laminated timber, and examined the mechanical property of the latter.
In order to control maximum response displacement of a structure under earthquake ground motions, the structure is required to have proper strength and cyclic deterioration capacity. In the previous paper, EIV which was defined as energy input velocity under stationary vibration was formulated. EIV was represented as a function of strength(Py) and maximum response displacement (δ max). In this paper, a procedure to determine the strength(Py) and the cyclic deterioration capacity which were required to control maximum response displacement was presented based on the concept of EIV. It was confirmed that EIV was almost equal to actual energy input velocity (ΔE /Te)max of inelastic response. Strength(Py) required to control maximum displacement was obtained by solving the relationship, EIV=(ΔE /Te)max. The strength(Py) was represented as a function of design maximum displacement (δ_D), total input energy(E_D) and actual energy input velocity (ΔE /Te)max. The procedure to determine the strength(Py) was validated from inelastic response analysis. In order to control maximum displacement, it is necessary to secure not only proper strength but also enough cyclic deterioration capacity. The capacity was defined based on EIV and its characteristics were discussed.
We have examined the characteristics of welded joint part in order to improve the toughness of HAZ. The probe samples used in this study are the steel plates produced by EAF-Plate mill process bearing Titanium for building. The remarkable improvement of toughness in HAZ is confirmed in the case of ultra large heat input weld condition. It is proved that sufficient HAZ characteristics can be attained by adjust the prompt analysis condition even in large heat input weld condition with 60-90kJ/mm.
Full scale shaking table tests of exposed type column bases are carried out. Parameter of the specimen is thickness of the base plate. Hysteresis rule of the column base with thick base plate, weak anchor bolt type column base, is expected to be of slip-type, since its plastic deformation is brought by monotonic tensile deformation of the anchor bolts. There are many research works of weak anchor bolt type column bases by static experiments. One of the purpose of this shaking table experiment is to prove the applicability of the statical research works to predict the dynamic responses of exposed type column bases. On the other hand, the hysteresis rule of column base with thin base plate, weak base plate type column base, is expected to be spindle shape due to the plastic deformation of the base plate under repeated bending. Evaluating the hysteretic behavior of weak base plate type column base is another purpose of this experiment. From experimental results, following conclusions were obtained. 1. The research works of weak anchor bolt type column bases obtained by the static experiments are applicable to the dynamic behaviors. 2. The energy absorbing capacity of weak base plate type column base can be greater than that of weak anchor bolt type column base.
Theoretical and experimental studies are presented on the compressive strength of a composite long column. In the analysis, the critical conditions for the maximum load are given explicitly and general solutions of strength of composite long columns with arbitrary cross sections and constitutive relations are obtained. The governing equations are given in an analytical form for elastic perfectly-plastic composite columns, and obtained numerically for arbitrary constitutive relations. In the experimental study, total 12 specimens with 4 types of slenderness are tested for concentric and eccentric loading. Buildup wide-flange H-62×60×6×6 and 90 reinforcing bars are encased in 12cm×l2cm concrete cross section. Computed results show good agreements with exact numerical solutions and experiments.
A total of three beam-to-column joints for composite structural systems consisting of reinforced concrete columns and steel beams, which are referred to as "composite RCS systems", was tested to investigate the structural performance and the stress transferring mechanisms. The joint details examined are "through column type" of which the joints are reinforced by cover plates and horizontal stiffeners without beam flanges. This paper indicates that using thicker cover plates and arranging extended face bearing plates are effective to enhance the structural performance of the joints. Stress transferring mechanisms in the joints are also discussed using three macro-models.
Hybrid structures (RCS) consisting of reinforced concrete columns and steel beams have been developed in Japan. Many studies have been conducted on the behavior of cross-shaped beam-column joints; however, there have been few experimental and analytical studies on the behavior of RCS frames. In this research, a nonlinear three-dimensional finite element analysis of an RCS frame specimen with through-beam type beam-column joints has been conducted. From the analytical results, the following conclusions were obtained. (1) The analytical results showed good agreement with the experimental results for the load-deformation relationships. (2) A compressive strut was formed from the outer concrete to the inner concrete in the joint area divided by transverse beams. (3) The torsional deformation component between the outer panel and the inner panel occupied a large rate in the panel deformation of the beam-column joints. (4) The ratio of the components which were assumed in the proposed equations of the shear capacity for the cross-shaped beam-column joints were different from the ratio which was obtained from the analytical results.