This paper describes the adaptability of Hillerborg fictitious crack model to timber. Using the regression line between the cumulative loss of the potential energy and the fictitious splitting length from the test data, the fracture process zone length was defined the length between the origin and x-intercept of the regression line, and the fracture energy was defined the slope of the regression line. The strength calculated by the fracture mechanical model on the specimen assuming initial splitting length equal to the fracture process zone length were agreement with the experimental results. However, the strength calculated by the fracture mechanical model using the conventional assuming initial splitting length equal to zero, was dangerously overestimated with the experimental results.

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It is well known that pseudo-velocity under-estimates the seismic response velocity if a long period structure is subjected to a ground motion with high frequency components. Whereas a velocity-dependent damper such as an oil-damper is affected by this effect, frequency dependency of the damper can be eliminated by generating the damping force relative to displacement by using a semi-active damper.
In this paper, a displacement dependent regulator for the semi-active damper is modeled by complex stiffness and the comparisons of the seismic responses of the base-isolation systems with the velocity- and displacement-dependent dampers illustrate the effectiveness of the displacement-dependent damper.

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The probability distribution of residual displacement of a perfectly elastic-perfectly plastic single-degree-offreedom system is discussed in this paper. By assuming that each plastic deformation during an earthquake is a constant and that the direction of the plastic deformation is completely at random, one can suppose that the probability distribution of the residual displacement would f ollow the binomial distribution, and the standard deviation would be proportional to the reciprocal of the square root of the number of the plastic deformations. The validity of the supposition is investigated through dynamic analysis using a number of pseudo and real ground motions.

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The global damage of pile foundations is detected using multi-step system identification technique. Penzien-type lumped mass model is used as the mathematical model of superstructure-pile-soil coupled system to separate piles from the surrounding soil. Unbounded and bounded field models are constructed for detecting pile damage. A limited numbers of acceleration sensors are placed on the roof and base of superstructure, ground surface and supporting soil layer. Experimental data of shaking table tests are used to verify the damage detection scheme. The change in pile stiffness due to damage is identified as damage measure for different combinations of damage states of pile foundation and inertia effects from the superstructure.

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A rule to predict translational and torsional seismic responses of highly damped structure is proposed. The structure is non-proportionally damped, because flexible and weak frames are provided with large dampers mitigating torsion. Steady-state theory is adopted to reduce the structure to a single-degree-of-freedom system. Peak values of the two responses of the system are obtained as a product of Ritz Vector and the peak generalized displacement estimated from linear response spectrum. Ritz Vector consists of complex values to account for phase difference. The rule considers both linear and non-linear systems based on equivalent linearization technique. Accuracy of the method is demonstrated via numerous time history simulations of single-story models developing both translational and torsional motions.

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In this paper, seismic performance of existing reinforced concrete (RC) asymmetric building and existing RC asymmetric building rehabilitated by steel braces is evaluated based on the equivalent single-degree-of-freedom (SDOF) system reduced from multi-degree-of-freedom system. In the procedure discussed in this paper, the direction of seismic input is assumed to coincide with the principal direction of the first modal response. Based on this assumption, the amplitude of seismic input, which produces the peak response corresponding to the ultimate stage of building, is evaluated from response of equivalent SDOF system. The results show that the amplitude of seismic input corresponding to the ultimate stage of existing buildings is satisfactorily evaluated by the proposed procedure. The influence of the direction of seismic input to the response of existing buildings is also discussed.

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The goal in this study is to propose a method that evaluates a design earthquake ground motion by using a velocity spectrum (S_V-spectrum) which represents the maximum response of a structure, an energy spectrum (V_E-spectrum) which reflects the input energy into a structure, and an f-value (Akiyama,Kitamura,2006) as the ratio of an average S_V-spectrum and an average V_E-spectrum. The proposed method has the advantage of being able to adjust the input energy at each site easily by the V_E-spectrum without changing the maximum response. In this paper, as the first-step in this study, we evaluated the characteristics of an f-value. First, we analyzed the values of an average S_V-spectrum, an average V_E-spectrum, and an f-value for every divided range of periods (0.1-1s, 1-2s, 2-3s, 3-10s) by using the observed ground motion records of the 2011 off the Pacific coast of Tohoku Earthquake and the 2003 Tokachi-Oki Earthquake. Next, we evaluated the relationship between the f-value and the fault distance, the magnitude of the earthquake, or the site characteristics. Finally, we have shown that the f-value tends to depend on the fault distance and the magnitude of the earthquake in the short-period range, and to vary with the site characteristics in the long-period range.

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Added mass on vibrating membrane roof in the air is investigated analytically and experimentally, including parameters such as various vibration modes and aspect ratio of flat plate. Finite Element Method (FEM) is applied to estimate added mass based on the theory of velocity potential. A series of free vibration tests on aluminum beams with various aspect ratios are conducted in the normal air and a vacuum chamber. The natural frequency difference between both environment conditions is used to evaluate added mass of air. Numerically-obtained added mass coefficients and experimental ones are almost identical. Based on these results, modal added mass coefficient of flat plate is formulated empirically as a function of aspect ratio and vibration mode.

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The present paper proposes a simple and efficient procedure to evaluate seismic fragility and risk of spatial structures and studies on seismic loss of a dome structure. As an example for calculating the seismic risk, a numerical investigation is performed for a single layer lattice dome supported by a substructure implemented with ductile braces as buckling restrained braces. The analysis of seismic loss is based on a simple rule for judging the damage to both of the structural and non-structural elements. The effectiveness and feasibility of the study is discussed and necessity of some kind of energy absorbing devices is suggested for more damage reduction through several examples with different yield base shear coefficient.

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Earthquake input energies have been discussed in considering seismic resistant capacities of structures. In the literature, it had been pointed out by the author et al. that potential energies due to self-weight and dead loads would be necessary to be taken into account in order to estimate the seismic resistance capacity in a good accuracy especially for beam type structures. The author presented an estimation method of ultimate seismic resistance capacity with the static absorbed energies considering potential energies. The method presented utilizes the two strain energies at an initial yield and a limit state, and a pseudo velocity response spectrum of seismic waves. Although it is based on an extrapolation method, it shows a good accuracy in the estimation of maximum input acceleration of seismic waves. The method includes a modification equation to improve the accuracy, considering the properties of elastic and plastic strain energies of structures during a pushover analysis. Then in this paper, the effect of static safety factors is investigated to make clear the meanings of coefficient in the modification equation, for lattice beams of two types, cross web type and warren type. As the results, a further modified estimation method is presented to predict the dynamic collapse level under excessive seismic motions with the information of pushover and free vibration analyses.

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The aim of this work is to propose making use of three-term method, as one of the standard direct minimization approaches, in searches of solutions in various static problems of structures. In the first part of this work, two simple recursive methods, namely two-term and three-term methods are presented as standard iterative direct minimization approaches. The dual estimate is presented as a powerful means of involving equally constraint conditions into direct minimization approaches. In addition, it is argued that while the two-term method is of no use at times, the three-term method always provides remarkable global convergence efficiency. In the second part, the gradient vectors that are appeared in the first part are generalized in natural ways and then the scope of the three-term method is extended for generalized minimization problems. The simultaneous equations that are solved in non-linear finite element methods are typical examples of such generalized problems. Various numerical examples are illustrated to indicate the wide applicability of the three-term method.

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The structural system with the rotational foundation enables to control the response of the super structure. A lot of studies on such rotational foundation have been done from the latter half of 20th Century. However, the number of buildings which have been constructed by adopting this structure system is extremely small.
The purpose of this study is to evaluate fundamental seismic behavior of the buildings with the rotational foundation due to uplift pile heads and to establish the seismic design of them.
The results of the dynamic analyses of simplified models showed that the response of this structural system is significantly small and the response evaluation can be possible if the equivalent damping ratios and potential energy due to uplift are properly considered.

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Bottom end of columns in the first story yields not only in the weak story mechanism but also in the overall sway mechanism. In order to evaluate ultimate earthquake resistance of building structures, it is necessary to clarify ultimate behavior of columns under random cyclic loading. In this study, based on the database of cyclic loading test results, hysteresis model of RHS columns including deteriorating range governed by local buckling is established.

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In this study, experimental investigations were conducted regarding blast resistance of reinforced concrete (RC) slabs with back surfaces strengthened with continuous fiber reinforcements. The main results obtained are as follows: 1) for preventing spall damage, the reinforcements are required to catch hold of the concrete fragments launched from the inside of the RC slab; 2) strengthening using continuous fibers is an alternative method which can prevent spall damage completely or cannot prevent at all; and 3) the damage of the slabs strengthened with continuous fiber sheets is lightened by increasing both fracture energy of the sheet and the modified-scaled concrete thickness of the slab.

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Construction photo-editing has prevailed among the Japanese construction industries as digitalization of photography becomes popular. Some of these “photo-editing” are made on as-needed basis in construction management process, while some are found to be the forgery of construction record. In this paper, categorization of “photo-editing” methods are firstly made based on the case survey in construction industries. Secondly, technical requirements of construction photo-editing detection method is summarized with particular consideration for editing needs in construction management processes. Thirdly, we have proposed a newly developed photo-editing detection method called “ROI expected-noise method”, and examined the performance using simulated samples of edited construction photography. The method has shown high detection performance and fulfilled the above mentioned requirements.

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Vibration systems with sliding friction are analyzed by using the Linear Accelerated Method based upon a new analytical logic which can study in detail the state of sliding motion within the constant time step. The logic was applied to linear single-mass systems with and without external force. The obtained numerical values are compared with the theoretical one and also the one without this logic. Then it was proved that the computing time is shortened greatly. In other words, much shorter time step is demanded, if the same computing accuracy is expected without the new logic.
It is also shown that the new logic is applicable to linear two-mass systems and non-linear vibration systems in which the upper part is a non-linear structure and the lower part is a sliding friction.

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Experimental and analytical achievements on the strength of wood beam with two holes in the above paper are discussed about the following items. 1) The plan of two holes is mismanaged in terms of spacing and diameter, because two holes overlap in some specimens. 2) The mechanical model for calculating shear stress in the inter-hole part due to bending moment seems illogical. 3) The cracking modes due to shear and bending are mode-I and mode-II, respectively, but the same fracture energy is employed. 4) The statement that the calculated strength shows the lower bound of experimental results is inadequate, because the actual properties of the tested timber are not used in the calculation.

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The authors wish to thank Prof. Hitoshi Kuwamura for the discussion. The answer to his questions is described in this article.

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