This paper reports the results of accelerated test (20°C, 40°C, 60°C and 80°C, moist condition) on the rate of corrosion of reinforcing bar in concrete which contains chloride ion. The factor of experiment are sodium chloride content (0-1.0％/sand), water-cement ratio (50-65％), and thickness of concrete cover (10, 30mm). It is concluded as follows, The corrosion loss of reinforcing bar in accelerated test increases in proportion to square root of test period. Rate of corrosion of reinforcing bar in carbonated concrete containing sodium chloride is larger than the rate of corrosion of reinforcing bar in un-carbonated concrete containing sodium chloride. The estimation equation of the rate of corrosion of reinforcing bar in concrete are proposed by sodium chloride content and water-cement ratio.

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It is strongly needed to predict and reduce the amount of concrete shrinkage. Prediction of hardened cement paste needs the information of specific surface area, volumetric water, and bulk modulus when it is based on the theory of hydration pressure. For this purpose, it is important to evaluate the water vapor BET surface area and find the way to predict this value. In this study, the specific surface area of various cement paste was determined by water vapor adsorption isotherm and B.E.T theory and chemically bound water of hardened cement of those was determined by thermal gravity analysis. Based on these data, the unique relationship between chemically bound water at the state of 11%RH condition and BET specific surface is found regardless of cement types.

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In this study, paste with a strength of over 200 MPa made using low-heat portland cement and silica fume was subjected to thermal histories with different maximum temperatures to confirm the development properties of strength, autogenous shrinkage, and pore structure. By clarifying changes in the pore structure under different thermal histories, the authors considered the effect of pore structure and evaporable-water on the strength and deformability. Furthermore, the function of micro-pores inaccessible to nitrogen or helium molecules and “unbound water” present in such micro-pores was considered.

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Powder coating has not yet been popularized in the present Japanese buildings. However, it has been popularized in overseas and over 10 years has been already passed from building completion. Durability of building materials has to be discussed in order to popularize in the Japanese construction industry field. Therefore, investigation into the actual conditions in overseas buildings has been executed. In this paper, the data is analyzed and the durability is discussed.
A main fruit of analysis is as follows. Chalking rate and gloss retention depend on the meteorological and the coating factors. And also, the powder coating durability in the Japanese building exterior is estimated.

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The purpose of this study is to develop an efficientmethod for estimating the first excursion probability in non-stationary response process of an elastic multi-degrees-of-freedom (MDOF) system. A simplified definition for the envelope process of the MDOF system together with the half-period sampling approach is introduced and enables to derive the multivariate probability density function (PDF) of the envelope process. The integral of the PDF is carried out with the Monte Carlo integration method and gives the first excursion probability. The effectiveness of the presentedmethod is investigated through some numerical examples.

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It has been recognized that the isolated building is the effective against seismic force. To estimate accurately the response about not only the horizontal but also the vertical direction are very important when the isolated building is designed. In this paper, the horizontal and vertical response characteristics of the high-rise and the middle-rise isolated buildings are investigated by using the observed data. On the basis of these investigation results, two types of three-dimensional analysis models are prepared for each isolated building and the accuracies of both analysis models are demonstrated by comparing with the earthquake-induced response obtained from the observed data.

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Many control techniques are used for shaking table tests to reproduce the target wave on the table. These controllers are basically designed in frequency domain by referencing a transfer function of a system to be controlled and the controllers are greatly influenced by the linearity of the system. If the system has a severe nonlinearity, these controllers have difficulty following the nonlinearity and the accuracy of the control decrease largely. To control the systems having severe nonlinearities accurately, control methods in the time domain may be more adequate than conventional methods in the frequency domain. This paper proposes a nonlinear control method in the time domain improving Minimal Control Synthesis (MCS) and it does not need any transfer functions or dynamic properties of plant to construct the controller, although original MCS is based on the reference model of the system to be controlled. In this paper, the efficiency of the proposed method is verified numerically and experimentally comparing with the conventional method such as H^∞ method.

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The purpose of this study is to gain an understanding of the lateral stiffness of laminated rubber bearings subjected to end rotation, and design stress of member to install in end of laminated rubber bearings. To understand the mechanical properties of laminated rubber bearings subjected to end rotation, the mechanical properties of laminated rubber bearings concatenated the rotational spring are evaluated. In addition, the degree of fluctuation in lateral stiffness and bending moment are evaluated by using the analytical model assuming a base isolated building with inclination of pile top.

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In this paper, the traction method is applied to shape optimization of frame structures. The traction method was proposed by Azegami, but in the present method, the sensitivity analysis is different from Azegami's one. The compliance of structure is chosen for objective function, and the coordinates of all nodes of beam elements are chosen for design variables. The method of sensitivity analysis is similar to a method used in topology optimization, but in this case the sensitivity of coordinate transformation matrix and length of elements is necessary. The effectiveness of the present method is verified by comparing with methods using SLP or CONLIN. Several numerical examples of 2-D frame structures are shown to demonstrate the effectiveness of the present method.

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Experiments on traditional wooden structures with devices to improve earthquake performance are performed. Devised points are as follows. 1) Kashira-nuki and Nageshi are improved and employed as structural elements. 2) Boards of wooden siding wall, in which are Chikara-nuki and Chikara-ita arranged by turns, is developed. Following things become to be clear as results. 1) The larger the column axial-force becomes to be, strength and stiffeness of Kashira-nuki increase. 2) Nageshi increases strength of structure by 1.5 times in the case with no Nageshi. 3) Wooden siding wall increases strength of structure by 3 times in the case without one.

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Impact hammer tests and analyses by finite element method were conducted to demonstrate the effects of support condition and uneven distributed load on the vertical dynamic characteristics of light frame joist floors with 3.64m-long-span and from 0.91m to 7.82m-wide joist floor consisted of 2" by 8" dimension lumbers and 15 mm-thick plywood subfloor.
The results indicate, i) Support condition slightly affects the natural frequencies when the width/span ratios exceed 2; ii) In addition to the mass-ratio of human-load, both the placement and the stand position of persons onto the joist floor give influence on the damping factor of 1st natural frequency; iii) The joist subjected to uneven distributed load generates locally deformed vibrational mode and also determines the 1st natural frequency of the joist floor; iv) Finite element analysis employed the appropriate models is effective to predict the natural frequencies and mode shapes of joist floor subjected to uneven distributed load.

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RC beams without stirrups on couplers were tested to investigate the shear performance. Seventeen specimens were designed and constructed with different structural details such as existence of coupler, coupler length, location of coupler, and existence of stirrups on coupler. In particular, the existence of standard couplers did not significantly affect on beam shear strengths unless stirrups located at the ends of couplers yielded. Moreover, a method to consider the specific details of this kind of structure in the AIJ design equations was presented to evaluate the shear strengths. Its applicability was examined through the test results.

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Recently, it has become increasingly important to instigate more widespread seismic retrofitting for seismically weak structures in Japan, which is frequently subject to massive earthquakes. Generally, post-installed anchors are used to connect the seismic retrofitting members to existing members. However, no computational models of post-installed anchors have yet been proposed in previous studies to evaluate stress-displacement relationships. Accordingly, we developed a new mechanical model for postinstalled anchors. In this model, the kinking behavior of anchor bolts, bearing behavior of concrete, and tensile behavior of anchor bolts are considered. The proposed model can reasonably simulate the mechanical behaviors of the previous test results.

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Buckling-restrained braces are used to a seismic retrofit of RC buildings. A connection between outer buckling-restrained braces and RC buildings is important for the seismic retrofit to be reliable. It is required for the connection to minimize shear displacements. The connection receives cyclic loads while the buckling-restrained brace absorbs seismic energy. Due to the suffering cyclic loads, an unexpected deterioration on the connection would proceed. The authors conducted cyclic loading tests of the connection. Basic information for the designing has been provided.

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Nonlinear dynamic analyses on the seismic response of reinforced concrete chimneys are carried out. An existing and a new design methods are applied to the design of the model structures. An existing design is equivalent to the current seismic standards in Japan, which is based on the allowable stress design, whereas the new design adopts capacity design concept where two plastic hinges are assumed at the mid-height and the bottom of the structure to protect RC chimneys from a collapse subjected to extremely strong ground motions. It is revealed that the extent of plasticity and location of yielding sections are varying drastically by the natural periods of the chimney and the predominant periods of the ground motions if the existing design are applied. So ductile detailing is necessary for all the region along the height. It is also revealed that the discontinuity of flexural strength is quite critical and sometimes results in unintended concentration of nonlinear deformations. On the other hand, the new design based on capacity design approach is found to have advantages in reducing the uncertainty of the non-linear responses and reducing maximum moment in the most part of the chimney, which ensure elastic response except the two potential plastic hinge zones. It may result in bringing the reduction of longitudinal reinforcements as well as eliminating the necessity of ductile detailing in the other elastic response region.

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We propose a new type of exposed steel column base with a base plate reinforced from underneath by rib plates embedded in the base concrete. A series of cyclic loading tests on actual-sized square tube column base specimens show that the combination of a short square stub column and rib plates arranged radially outside the stub column can effectively reinforce the base plate from underneath. Local behavior of the column base is estimated through plastic and finite element analyses; the findings of these analyses can be used for preventing local collapse and fracture of reinforced column bases.

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This paper presents results of full-scale loading tests of welded moment connections subjected to variable amplitude cyclic loadings. The tests were conducted by two types of loading protocols, i.e. the two different constant amplitudes and the random amplitudes. The deformation capacity of specimens are compared with predicted deformation capacity based on the relationships between crack propagation and number of cycles obtained from the constant amplitude cyclic loading tests. The predicted deformation capacity well corresponds to experimental results by the two different constant amplitude loadings, but for the random amplitude loadings, the modification to consider loadings in the elastic range is needed.

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This paper presents results of loading tests of H-SA700 high strength steel structures in which beams and columns are made by undermatched welds and constructed by knee brace dampers. The feasibility of high strength bolted joints of high strength steel members with knee brace dampers and mechanical performance of the beam-column subassemblages are verified by loading tests. The advantage of high strength steel is verified by examples of the design of structures and the results of time history response analyses comparing with the structures made by usual mild steel.

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Recently aluminum braces are used for seismic retrofit of reinforced concrete buildings. Aluminum braces reaches their maximum strength at similar story drift angle as reinforced concrete frames and have a priority to steel tube brace, which buckles where RC frames reaches their maximum strength. However, their cyclic performances after buckling are not confirmed yet. If they cause local buckling after overall buckling, they are expected to be fracture. In this paper, cyclic loading experiments on aluminum braces with pin-end connections are carried out until their fracture, and their performance after buckling is confirmed. Also applying the method for steel tube braces, easy fracture prediction method for aluminum braces is proposed and their validity is discussed.

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Concrete Encased Steel (CES) structural system consisting of steel and fiber reinforced concrete (FRC) is a new proposed composite structural system. The aim of this research program is to evaluate the deformability under seismic actions of the CES columns with encased-steel of H-shaped section. In existing studies by the authors the influence of the axial force ratio, the H-shaped steel ratio and the shear span ratio on the deformation capacity were presented. Also a formulation for the evaluation of the column deformation capacity was proposed. In this study the influence of the concrete fiber contents ratio (percentage of fiber volume to concrete volume), and the flange width of H-shaped steel on the deformation capacity is examined Using the above five parameters, a new formulation was proposed and its validity was verified by comparing it with the test results in this paper.

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In order to investigate shear and bending behavior in fire of I-shaped prestressed precast concrete (PCaPC) beams with high-strength rebars and multiple large openings, three specimens for PCaPC beams were tested. The fire resistance time, temperature of cross section and deformation of PCaPC beams were confirmed from the test results. The evaluation method for bending and shear strength of PCaPC beams at high temperature, as well as the results of the fire experiment will be presented. In this analytical method of bending and shear strength, two modes of resistance mechanism of PCaPC beam are proposed. In one mode, RC beam is supposed to be the resistance mechanism, and in the other, structure of upper and lower beams. The fire resistance time calculated by this proposed method, taking into account the temprature and bond strength of longitudinal and shear rebar and concrete, is shorter than experimental results by 14 to 45 minutes.

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The fictitious crack model proposed by Hillerborg is applied to estimate the splitting strength of wood in this article. This new method might be useful method for timber engineering. However we could see some points not to understand its theoretical concept. I hope the authors to explain the details.

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The authors wish to thank dr. Wataru Kambe for the discussion. The answer to his questions is shown.

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Experimental and analytical achievements on the initial stiffness and ultimate slip of timber joint with drift pins in the above paper are discussed about the following items. 1) The statistical model to evaluate the initial stiffness is incorrect, because the gap between hole and fastener cannot be represented by a normal distribution ranging to negative values. 2) The assumption of splitting forces that act in inter-hole and end margin is erroneous, because it contradicts the experimental observation. 3) Application of different Weibull distributions to the ultimate slips of single- and multi-fastener joints is theoretically mistaken, because the Weibull distribution is an asymptote of the weakest link problem for infinite number of elements.

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The authors wish to thank Prof. Hitoshi Kuwamura for the discussion. The answer to his questions is as follows:
1) We corrected some mistakes in this article owing to Kuwamura's discussion. 2) Assumption of splitting force ware re described 3) Kuwamura's misunderstanding of Weibull distribution are discussed

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