There are only a few reports that have been studied synthetically how to decrease the amount of CO_2 effectively regarding the utilization of coal ash. The purpose of this report is to make utilization-models based on the present situation of coal ash utilization and to try to evaluate the quantity of CO_2-emissions in each model. The results are as follows.: 1) In the case of making the best use of 'Fly ash-mixed-cement', the amount of 1.44 million t-CO_2 can be reduced and is about the same as 30% CO_2-reduction effect of the 'Blast furnace slag-mixed-cement'. 2) In the case of partly replacing the fine aggregates with fly ash, the amount of 0.4 million t-CO_2 can only be cut down. 3) In the case of utilizing the artificial aggregates and slag made of fly ash, a great deal of fly ash disposed as the wastes can be reduced. 4) It is confirmed that one of the most effective ways of fly ash utilization is to use fly ash for the base-concrete of wooden houses, as compared with using it for mass concrete in the reactor building of nuclear power plants.

View full abstract

Triaxial and biaxial compressive strength of experimental specimens are understood by tensile strength of the concrete, with formation of a reverse truncated wedges which is built up symmetrically with a vertical line in the specimen. The reverse truncated wedges are formed by the shearing stress and nomal stress of "Griffith's fracture criterion". But the assumption of formation of the reverse truncated wedges has certain limitations for applying to structures such as the reinforced concrete structure. In this paper, an idea termed as "Mennodo" is introduced to better explain the triaxial and biaxial compressive strength of concrete of the specimen. The "Mennodo" is defined by the area which is calculated from direction cosine of Mohr's circle due to three dimentional principal stress.

View full abstract

Appropriate modeling of seismic load intensity is one of the critical factors for the reliability assessment of a structure. Using active fault data and attenuation formula, this paper presents an analytical method to evaluate cumulative distribution function (cdf) of n-year maximum value of ground motions and response spectra at a site efficiently considering various kinds of uncertainties including magnitude of earthquakes, recurrence periods, and accuracy of attenuation formula. Numerical examples show that the cdf of the n-year maximum value is different from site to site. The sensitivity of the cdf to the uncertainties to the probabilistic models is also investigated.

View full abstract

This paper shows LES analysis of turbulence effects on vortex-induced oscillation of a circular cylinder. First, we discuss the accuracy of the computed results of the wake flows and pressure distribution for a stationary circular cylinder in smooth and turbulent flows as a function of Reynolds numbers. Next, the present LES method is applied to the flow around a freely-oscillating circular cylinder in smooth and turbulent flows. Turbulence effects on characteristics of the response and vortex motions around an oscillating circular cylinder are examined. Consequently, we investigated the swiching of the vortex patterns and the effect of secondary vortices on rapid phase jump, concerning the vortex formation. It is recognized that only one of two vortex patterns in lock-in range is weaken by oncoming turbulence, while another is not.

View full abstract

We propose a damage identification algorithm for story stiffness and damping factors of a building. These values can be direct damage indices. The modal properties obtained by subspace identification are utilized to derive them. The proposed algorithm is basically applicable to any shear structure. In this study, a seismic isolated structure was chosen as the monitoring target. The isolation layer and superstructure are treated as separate substructures as they are distinctly different in their dynamic properties. Based on this substructure approach, damage evaluation is conducted for an isolation layer. Effectiveness of the proposed method is verified through simulations and experiments.

View full abstract

Adaptive simulated annealing method is applied to identification of frequency-dependent damping factors of soil from vertical array data. Obliquely incident S waves are considered as input motion at borehole and so three components of transverse, radial, and vertical components are used for the inversion. Based on numerical experiments it is shown that a damping factor, an incident angle and S-wave velocities are inverted very well, independent of initial random numbers used for the method. This method is applied to strong motion records and it is confirmed that all the unknown parameters are stably inverted.

View full abstract

This paper proposes a constitutive rule for the viscoelastic materials combining iso-butylene and stylene polymers. The materials exhibit an elliptical hysteresis loop under small deformation, and a bi-linear hysteresis loop under large deformation. The so-called temperature-frequency equivalency principle is found applicable to this type of co-polymer, and it is utilized for efficient analytical modeling of three distinct viscoelastic materials. The constitutive rule involves fractional time-derivatives of stress and strain, and a new algorithm is proposed for numerical integration. The model shows excellent accuracy over a wide range of temperature and frequency of the sinusoidal loading, as well as random loading that simulates the effects of different earthquakes and building vibration periods.

View full abstract

This paper deals with the material nonlinear analysis of reinforced concrete slabs considering the effect of bond slip of reinforcement. Only a small number of studies have been reported in the literature that approximately consider the effect of reinforcement bond slip in two-way reinforced concrete slabs, and almost no cases are found in which material nonlinear analysis is used to rigorously consider the effect. In this paper a potential energy functional is first derived, and then a finite element formulation of the problem is implemented. In order to verify the analytical method five numerical examples are given and the results compared with experimental results.

View full abstract

Pseudo-dynamic tests were conducted to investigate the response properties of saturated sands focusing on the pore water pressure subjected to horizontal one-directional and two-directional earthquake waves. The apparatus was simple shear test device incorporating two cyclic loaders. Firstly, the major axis direction was studied by typical strong motion records of Tail and Hachinohe, and secondly, the response properties of model soil profiles were compared subjected to two-directional and one major axis inputs by adding three earthquake waves with different frequency contents. The results show the following significant features. 1) In case of the evaluation of the liquefaction potential, the major axis direction can not evaluate by the characteristics of input earthquake motion only, but it is necessary to consider the predominant period of surface layers. 2) The maximum response values of acceleration, velocity and displacement of soils and frequency contents show little different both in the case of two-directional and one major axis inputs. 3) However, it is necessary to modify the maximum amplitude of earthquake waves in major axis in the evaluation of pore water pressure ratio.

View full abstract

Experimental study of the steel plate reinforced concrete structure (SC) having a opening was carried out. And the reduction ratio for opening which is used for reinforced concrete was proved to be good applicable to the SC wall. By the results of the analytical study of the steel plate reinforced concrete structure (SC), the evaluation method to the reinforcement for opening was proposed.

View full abstract

Hybrid single-layer lattice shell using supplementary parts is the rectangular grid shell stiffened by parts. The tension-truss system that is used as the parts, is effective for improving bending stiffness of the low-rise shell. Full scale experiments using the tension-truss dome used as an annex on the former institute building of I.I.S, the University of Tokyo, were performed to confirm the effect of the parts for improving the stiffness and the bearing load. In the paper, the results of the loading test are shown. The final failure state was brought by buckling of a compression truss member. The effect of the parts was confirmed not only by the numerical analysis, but also by the loading test.

View full abstract

The present paper discusses and proposes the estimation method of the dynamic response of a reticular dome supported by a sub-structure based on push-over analysis considering the effects of the second mode. The investigation shows that in most cases of ordinary reticular domes the sum of the effective masses for the first and second mode is greater than 90% of the total mass even if the effective mass for the first is as small as 30% of the total mass. Under such condition of small effective mass of the first mode the accuracy of the estimation is investigated through comparison between those based the present estimation and the results based on direct dynamic nonlinear response analysis, leading to a conclusion that the present estimation method is fur efficient than that previously proposed by the same authors neglecting the contribution from the second mode.

View full abstract

For the design based on the performance, the evaluation method for the earthquake resistant performance of the reinforced concrete multi-shear walls is being developed. In this paper, the evaluation method for the restoring characteristic of the multi-story shear walls, which is developed originally is described. The main characteristics of this method are following; 1) the whole deformation consists of the bending deformation and the shear deformation. 2) the evaluation method for the shear deformation is based on the truss theory which considers the normal force, the restraint effect by the outline frame and the effect by the bending yield. The calculated results by this method corresponded well to the experimental results.

View full abstract

The authers reported on the testing of some buckling-restrained braces that use different buckling restraining methods, and also discussed their performance evaluation. In consideration of the advantages and drawbacks of the results from testing and manufacturing, a new type of buckling-restrained brace is conceived through the use of new manufacturing methods. A partial frame model of the structure with the buckling-restrained brace is used as the test equipment, and static cyclic loading testing is conducted by applying increasing loads alternately in positive and negative directions. The cumulative ductility factor, the energy absorption rate, and the final facture characteristics of the newly buckling-restrained braces are analyzed.

View full abstract

The unembeded type of the column bases of Steel Reinforced Concrete buildings were severely damaged by Hyougoken Nanbu Earthquake in 1995. The anchor bolts and main reinforcing bars were often broken. This is mainly due to the lack of consideration of the tensile force caused by the overturning moment during earthquakes. In this report the strength and ductility of the unembeded type of column bases are examined. The strength of a column base can be evaluated by the sum of the strength of the components unless the bond between the concrete and reinforcing bars is deteriorated. The large amount of tensile force deteriorates the ductility of the column base. We propose the formula to predict the ductility of the column base which relates the parameter "effective tensile force ratio" considering the bond strength as well as tensile strength.

View full abstract

In order to reduce further destruction of buildings and to reduce the number of homeless people caused by the aftershocks, a quick inspection of the damaged buildings ought to be carried out. This research aims at developing an integration method by computing the response displacement from the measured acceleration. This new method provides an automatic and a quick inspection system performed by few cheap accelerometers. The errors included in the measured acceleration data can be accumulated during the double integral. The new integral method, which is based on Iwan's method and a band-pass-filter, is proposed in this paper.

View full abstract

The purpose of this paper is to propose a new stiffness design method for shear buildings subject to design earthquakes with non-monotonic displacement spectra. An objective function is introduced by a combination of the fundamental natural period representing 'cost index1 and the level of maximum displacements representing 'performance index'. This objective function is used for finding an optimum set of story stiffness under response constraints. Introduced is an enveloping design spectrum that envelops the specified design spectra. An inverse problem formulation is utilized for finding the stiffness such that the shear building would exhibit maximum interstory drifts proportional to specified ones under design earthquakes compatible with the enveloping design spectrum. Several design examples and time-history analyses are performed to demonstrate the validity and the accuracy of the proposed design method.

View full abstract