To allow the practical use of high the cement including ground granulated blast furnace slag (GGBFS) content by weight of 60% to 70%, it is effective to increase the amount of sulfur trioxide (SO₃) by adding anhydrous gypsum for the purpose of increasing early age compressive strength, suppressing shrinkage cracking due to autogeneous shrinkage, and reducing drying shrinkage. On the other hand, the influence of increased amounts of SO₃ on fire resistance characteristics remains unclear in many respects. In this study, we investigated fire resistance of concrete using the cement including high amount of ground GGBFS. Three experiments were conducted to investigate the fire resistance of the concrete specimens with high volume of GGBFS and to clarify the mechanism involved.
 In the first experiment, a fire resistance test simulating a fire up to 900°C was carried out on concrete specimens with SO₃ content ranging between 2% to 8% as the test factor. The experimental results showed that explosive spalling does not occur if the amount of SO₃ is 4% or less, whereas it tends to occur if the amount of 5% or more.
 In the second experiment, the change of temperature inside the concrete during the fire resistance test was recorded using small RC prism specimens. The time period in which explosive spalling occurred was 5 to 12 minutes after the start of heating and the temperature range at the concrete cover depth of 10mm to 30mm was estimated to be 100°C to 200°C.
 In the third final experiment, thermogravimetric analysis (TG) was carried out for the cement including high amount of ground GGBFS, with SO₃ content ranging between 2% to 8%. The measurement results indicated that the amount of SO₃ degree correlated with ettringite (3CaO·Al₂O₃·3CaSO₄·32H₂O) content obtained by the Rietveld analysis using XRD measurements. This suggested the higher tendency for explosive spalling of concrete using the cement including high amount of ground GGBFS with a high amount of SO₃ is caused by the increased amount of dehydration of hydrates arising from the increased amount of generated ettringite hydration products.
 Based on the above, it was estimated that dehydration of ettringite hydrate product in the temperature range of 100°C to 140°C greatly increase the vapor pressure inside the concrete, and that the greater the amount of SO₃, the lower the resistance to explosive spalling under fire. Designing the cement including high amount of ground GGBFS with SO₃ content of 4% or less is considered to maintain performance for the explosive spalling resistance of concrete.

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 This paper describes with experimental study on properties of recovered fine aggregate and mortar using recovered fine aggregate. Recovered aggregate is take a recycle-aggregate from ready-mixed concrete that go back to concrete batching plant from construction site. And it can be used for ready-mixed concrete since JIS A 5308(Ready mixed concrete) was revised in 2014. From the angle of the environment-friendliness, the reuse of recovered aggregate is desirable.
 However, the accumulation of research data of the properties of recovered fine aggregate and mortar using recovered fine aggregate isn't enough yet. When recovered aggregate is used for concrete, it's necessary to understand properties of recovered aggregate and concrete using recovered aggregate. In the past technical report on recovered aggregate, density of recovered fine aggregate lower than that of original fine aggregate. And water absorption of recovered fine aggregate higher than these of original fine aggregate. Therefore, properties of recovered fine aggregate and mortar using recovered fine aggregate were investigated. As a result, the following were found:

 (1) Within the range of the present tests, density of recovered fine aggregate lower than that of original fine aggregate. And water absorption and finesse modulus of recovered fine aggregate higher than these of original fine aggregate.
 (2) Within the range of the present tests, mortar-flow and air content of mortar using recovered fine aggregate higher than that of mortar using original fine aggregate.
 (3) Within the range of the present tests, compressive strength of mortar using recovered fine aggregate lower than compressive strength of mortar using original fine aggregate. However, when recovered fine aggregate use in the specified value of JIS A 5308, the strength reduction is not greater.
 (4) The causes of the strength reduction when mortar using recovered fine aggregate are increase of air content of mortar caused by change in grading of fine aggregate and a decrease of fine powder of fine aggregate.

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 In order to conduct flow analysis of cement paste, mortar and concrete, it is important to obtain rheological constants representing the flow characteristics of the material. In this study, we measured cement paste's rheological constants by using rotational viscometer. Here, it was measured in consideration of flow history on cement paste. Furthermore, in this study, we derived the flow constitutive equation of the cement paste and proposed a marker particle visco-plastic finite element method. Using this marker particle visco-plastic finite element method, simulation of flow test of cement paste was attempted.
 The results obtained from the experimental study and analytical study of this research can be summarized as follows.
 Using a rotational viscometer, the flow curve of cement paste was measured for various shear conditions. It was confirmed that the flow curves of all cement paste samples can be approximated by the Bingham model under all shear conditions. And the obtained flow curve was approximated by the Bingham model, and the rheological constants (yield value and plastic viscosity) of the paste sample was determined. Thixotropy was confirmed in the flow characteristics of the cement paste sample from the obtained flow curves and rheological constants.
 The cement paste was regarded as a visco-plastic fluid and derived the flow constitutive equation of visco-plastic fluid using overstress theory. The obtained flow constitutive equation considers non-Bingham characteristic, flow history, and pressure dependency of yield value. It was confirmed that the flow curves of cement pastes differing depending on shear conditions can be expressed by the proposed flow constitutive equation.
 Marker particle visco-plastic finite element method was used to analyze the flow test of cement pastes. The results obtained by the analysis agreed well with the experimental results. Therefore, the marker particle visco-plastic finite element method and the rheological constants are effective.

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 This paper describes the dynamic behavior of the six story seismically isolated building constructed on soil with inclined bedrock, based on strong motion records along with an evaluation of pile stress. The ground under the building has a two-layer structure composed of bedrock and deposit soil, where the bedrock depth is inclined toward the east-west direction. The foundation system is composite of a spread foundation and cast-in-place concrete piles with variable lengths according to the inclination of bedrock. The strong motion records are observed at the center and edges on the upper and lower floors of the seismic isolation layer.
 First, the seismic motions in deposit soil overlying the inclined bedrock are evaluated with a combination of SH and SV analyses using two-dimensional (2-D) FEM. Seismic response analyses are performed using a three-dimensional (3-D) full frame model consisting of the superstructure, seismic isolation devices and piles. The 3-D model is validated by comparison with strong motion records from the first floor and the basement. Then, the dynamic behavior of the seismic responses of the superstructure and pile stresses are evaluated and discussed. The conclusions of this study are summarized as follows:
 1. The displacement of the piles and surrounding soil increases as the depth of the bedrock increases. However, the displacement of the piles tends to be smaller in the longitudinal direction than the displacement of the soil, because the pile head was constrained by the mat slab.
 2. The bending moment and shear force at the spread foundation is larger than any other piles regardless of the direction of the inclination. The bending moment of the piles in the longitudinal direction is larger at the pile head due to the constraining effect of the mat slab, and in the middle section of the piles due to the kinematic effect of the soil seismic response.
 3. In the structural design scheme for pile stress evaluation, the 1-D model assumes a horizontally flat layer for each pile location. The bending moment and shear in the 1-D model were overestimated in comparison with those of the 2-D model.

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 It is important to evaluate the modal correlation coefficient when the responses to be combined are from modes with closely spaced frequencies. In these cases, the complete quadratic combination (CQC) rule is used instead of the square root of the sum of the squares(SRSS). To evaluate the value of the modal correlation coefficient, it was evaluated as a CQC factor. However, an exception to this approach arises when the modal correlation coefficient in secondary systems is evaluated. When the modal correlation coefficient in secondary systems was evaluated, it was found that the tendency of the modal correlation coefficient in the primary and secondary systems analyzed by time history response was different, with the latter being greater than the former for the modal correlation coefficient when the natural period in the primary system is longer than that in secondary system. Other studies have proposed formulas for the modal correlation coefficient in a primary system. This study aims to propose a formula for the modal correlation coefficient in secondary systems based on primary system formulas reported in these previous studies. Furthermore, the modal correlation coefficient in the secondary system was examined based on our proposed formula.
 The conclusions of this study are summarized as follows:
 1) Comparing of the modal correlation coefficient in secondary systems in single degree of freedom with that in multi-degrees-of-freedom, the tendencies were found to be different. Moreover, they were particularly different from the secondary and tertiary natural periods in multi-degrees-of-freedom.
 2) The modal correlation coefficient in multi-degrees-of-freedom is expressed as the sum of the products of a participation vector of primary systems, the Fourier amplitude of ground motion and a factor of the modal correlation coefficient in single-degree-of-freedom primary systems. Additionally, the modal correlation coefficient in the secondary systems calculated by Eq. 10 can be evaluated by adding components around three-order modes.
 3) It is confirmed that CQC factors to combine peak values nearly correspond to correlation coefficient not only in primary systems but also in secondary systems.

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 We proposed the method for estimating inhomogeneous attenuation structures by dividing the propagation path regions from the source to sites. In the proposed method, it is not necessary to assume the divided region in advance. On the basis of the statistical test, the divided region is estimated. Once statistically significance level is satisfied in each block under the minimum block size are assumed, we can estimate inhomogeneous attenuation structure with the resolution according to the number of data. We applied the proposed method to the source region of the 2008 Iwate-Miyagi Nairiku Earthquake. The obtained results are summarized as follows.

 1) Estimated inhomogeneous attenuation structure shows low-Q on the block including Mt. Kurikoma, which is an active volcano, and the west side of the volcanic region. The short-period level of the main shock source spectrum estimated from the proposed method corresponds to the average level estimated from the empirical formula by Dan et al. (2001).
 2) Compared with the conventional method which assume homogeneous attenuation structure, site amplification factors were estimated to be large at the site where volcanos are in the vicinity such as the IWTH25, and the short-period level of source spectra was estimated to be small.
 3) Interpretation of small source spectra and large site amplification factors is as follows. In the source region, several sites are located in the high attenuation zone. This means that by appropriately evaluating the influence of high attenuation zone, amplitude of seismic bedrock motions at the observation point near the source region are evaluated to be small, resulting in large site amplification factors in comparison with conventional method. At these sites, since the influence of the Q value is not dominant because the distance is short, source spectra are estimated to be small. Site amplification factors of east side of target region did not change regardless of methods. Q value of east side according to proposed method tends to be larger than the conventional method. This large Q also contributes to estimating small source spectra.
 4) It is concluded that inhomogeneous modeling of the propagation path is important especially in the volcanic area, such as the source region of Iwate-Miyagi Nairiku Earthquake, when separating the observation records into the source, path, and site effects.

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 A sequence of two strike-slip earthquakes occurred on April 14 and 16 (namely, the foreshock and the main shock), 2016 in Kumamoto Prefecture, Japan, and caused heavily damage to more than 7,000 wooden houses and residential buildings mainly in a central district of Mashiki town. The heavily damaged area of wooden houses was concentrated in a 0.3 km narrow belt that lies along the east-west direction (Fig. 1), where the belt is situated on a plain formed by several rivers and its geological setting could be a sedimentary deposit. This suggests that the concentration of building damage might be due to the local site effects in the area. There are two strong motion observation stations in Mashiki town. One is the KiK-net KMMH16, on the ground surface which is located north from the damage concentrated area. The other is the local government's intensity seismometer collaborated with JMA, called MTO in this paper, on the first floor of a building at Mashiki town office, which is located nearby the damage concentrated area and may be affected by soil-structure interaction (SSI) effects. In order to evaluate the local site effects on the seismic records, SSI effects on that should be clarified. Therefore, dynamic response analyses of the building at Mashiki town office are conducted for the earthquakes, considering SSI effects with nonlinearity based on geophysical and geotechnical surveys.
 Mashiki town office is a three-story reinforced concrete building supported by pre-stressed concrete (PC) piles constructed in 1980 and has been retrofitted by out-flame in a longitudinal direction (Fig. 2). According to the visual inspections in post-earthquake damage evaluation, heavily damaged piles and some gaps caused between structure and soil were shown after the earthquakes (Photo1). The pseudo velocity response spectral value of acceleration records at the MTO is larger than that at the KMMH16 in a period range over 1 s during the main shock (Fig. 3, 4). In order to evaluate both effects of the local site and the SSI quantitatively, site investigations (i.e., borehole surveys, microtremor explorations and soil tests) were conducted (Fig. 5-9, Table1).
 Then, the seismic responses of ground at the MTO are estimated by using the nonlinear seismic response analyses from the acceleration records on the ground surface at the KMMH16 (Fig. 10, 11). It is found from the analysis result that the acceleration response on the ground surface at the MTO is almost the same when compared to that at the KMMH16 (Fig. 12).
 Dynamic response analyses are conducted by using nonlinear time history analyses to the SSI analysis model of the building (Fig. 13-15, Table1-2). A gap caused between pile and soil is modeled as slip behavior in a hysteresis rule of a soil spring at a shallower position. The foreshock and the main shock are continuously imposed on the analysis model. The SSI analyses have resulted in good agreement with the strong motion records observed at base foundation of the building during the earthquakes (Fig. 16). Furthermore, SSI effects include some nonlinearities of a pile-soil system at a shallower position, which is a gap caused between pile and soil and damage to pile head (Fig. 17).
 The parametric studies indicate that the seismic response at the base foundation to the main shock which has a strong component in a period of 1 s is increased by a gap caused between pile and soil due to the foreshock or strength deterioration of pile head due to damage of PC pile, which contributes to a stiffness reduction of a pile-soil system and an increase in a base foundation response to an oscillation in the period of 1 s during the main shock (Table3, Fig. 18-20).

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 Simulation analysis is an effective method for assessing building safety after an earthquake. This kind of analysis is effective for evaluating foundations or piles, whose safety cannot be confirmed by a visual check.
 During such analyses, the input motion should be set to reproduce observed waves at observed points. In these cases, the modal iterative error correction (MIEC) method can be used to set the input motion even if the analysis model exhibits a nonlinear behavior. However, how to choose the mode for correction is difficult. Using a selection method by a singular value calculated by singular value decomposition, the previous paper presented a case, where the convergence calculation did not stabilize, and led to a divergence.
 This study proposes a new mode selection method to stabilize the convergence calculation. The outline and details of the method are described, and the results of the experiments performed to confirm the method precision are presented.

 The findings of this study are as follows:
 (1) This study proposed two mode selection methods. One is the method of selecting modes by “the norm ratio of the residual vector.” This method selects the modes until the main shape of the residual vector can be represented. The second method is the method using the “norm of incremental input vector,” in which modes are selected until the norm of incremental input vector reaches a threshold for avoiding excessive input increment.

 (2) The proposed methods were applied to a sample problem to confirm their accuracy. As a result, both methods can stabilize the convergence calculation through the MIEC. However, from the viewpoint of avoiding the unnecessary high-frequency component in the identified input motion, the method using “the norm ratio of the residual vector” is superior to that using the “norm of incremental input vector.”

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 The objective of this study is to examine the improvement method with hollow part of SC pile in order to improve the deformation performance of SC pile. In the pile foundation structure, the improvement of design is prompted assuming large earthquake. However, study on the deformation performance of precast concrete pile is not sufficiently advanced. Therefore, the test data accumulation is not enough to discuss the deformation performance of pile.
 In the previous study, we confirmed that filling the hollow part of the SC pile with reinforcement was effective for improving the deformation performance. However, there were some issues on the terms of construction when it use the SC piles filled with reinforcement for the hollow parts. Therefore, we studied an improvement method that left the hollow part for preparing flexibility in terms of construction. We examined two improvement methods. Two improvement methods were 1) to increase the thickness of the pile body concrete, 2) to install an inside steel pipe in the hollow part of SC pile. We confirmed the effectiveness of the improvement method by simple beam bending test and cantilever beam bending shear test.
 We analyzed the relations between the displacement of vertical and the angle of member, relations between the load and the displacement, and relations between the bending moment and the curvature. Furthermore, we proposed an analytical method to evaluate the deformation performance of piles and compared the analytical values with the experimental values.
 The knowledge obtained from this study are shown below.

 1) By increasing the thickness of the pile body concrete, it is difficult to suppress the large decrease in bending strength and axial displacement after confirming the maximum proof stress. However, the effect of improving deformation performance can be expected.

 2) The effect of improving the deformation performance by increasing the thickness of the pile body concrete is inferior to reinforcement using concrete for filling material. However, it is same to reinforcement using soil cement for filling material.

 3) By making the pile a double steel pipe, axial displacement due to repeated bending stress can be suppressed, and improvement effect on bending deformation performance can be expected.

 4) The effect of improving the deformation performance by making the pile a double steel pipe is same to reinforcement using soil cement for filling material.

 5) We proposed an analytical method considering the influence of the outer outside steel pipe and the pile hollow part. The relationship between the bending moment of the pile and the curvature can be evaluated by the proposed analysis method. However, the result of the proposed analysis method is underestimated when the hollow part is improved with multiple materials (inside steel pipe and mortar).

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 In recent years, the adoption of the rectangular ETFE cushion as a roof cladding element has become widespread. It is anticipated that this trend will continue and that the size and shape of the panels made of ETFE will become more diverse. But characteristics of ETFE give rise to concern that the local deformation as a result of ponding can increase progressively over time, as additional loading accumulating snow/water causes further deformation of the cushion. In addition, the behavior of the cushion structure exceeding the 1st yield point hasn't been studied and investigated yet.
 In this paper, the behavior of ETFE sealed air cushion under partially distributed loading was examined and the phenomenon of progressive ponding was studied under water/snow loading.
 As a result of comparative studies using experiments and numerical analyses taking into account membrane contact, it was confirmed that there was a trend that both upper and lower membranes deformed almost equally keeping the initial cushion depth until inversion occurs under full positive. Membrane displacement under partially distributed loading was greater than loading over 100% of the area and as the aspect ratio of the cushion panel becomes larger, the increment of internal air pressure reduced. The minimum inversion load under partially distributed loading reduced for panels with larger aspect ratios. The loading area which created maximum displacement was different depending on the aspect ratio. It was confirmed that collapse due to progressive ponding phenomenon did not occur under the parameters within the scope of this study.

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 The important structural elements of traditional timber structures in Japan are rotational resistances of column-beam joints. The restoring force characteristics of their structures depend on the rotational resistances of the joints. Therefore, the elasto-plastic restoring force characteristics of embedment of joints are the most significant in order to evaluate the seismic performances of traditional timber structures.
 The authors have already made clear the embedment mechanism of crosspiece joint which is the most basic and whose rotational center is easily understood, and formulated the elasto-plastic restoring force characteristics of embedment of joints by using Elasto-plastic Pasternak Model (abbreviated to EPM).
 In the previous paper³⁾, as for the T-type joints, the authors researched the rotational center by T-type joint loading tests, focusing on the movement of the center of the joints and the rotational centers. They assumed the rotational center on the surface of Nuki and under the edge of Sashikamoi. Then, the restoring force characteristics were formulated based on the EPM, and parameters were determined in order to trace the restoring force characteristics of the test results.
 In this paper, the loading tests of T-type joints are carried out, using wooden loading blocks instead of the steel column. The test setup is shown in Fig. 2. The test specimens of Nuki and Sashikamoi are made of Japanese Cypress. Nuki specimens consist of T, TF, TK, TKF, TL and TLK and Sashikamoi are SL and SLK as shown in Fig. 3 and Table1. TF and TKF are the specimens with Teflon sheet for friction reduction. TK, TKF, TLK and SLK are those with a cotter in the joint.
 The test results of joints are shown in Photo1～Photo4. Rotational characteristics of joints are shown in Fig. 4～Fig. 11 and reactions of the cotter are shown in Fig. 12 and Fig. 13. The rotational center C is searched from the geometrical relation between the joint centers and the rotational centers. Distribution of the rotational centers C is plotted in Fig. 17. As a result, the rotational centers C mostly situate on the surface for Nuki, and under the point V for Sashikamoi, which are almost the same as the previous paper. Thus, the EPM formulations of the Nuki and Sashikamoi are confirmed similarly to the previous paper in equations from (4) to (35). The restoring force characteristics of test results are simulated based on the EPM formulation and obtained the EPM parameters as shown in Table2 and some examples of simulated results are drawn in Fig. 20～Fig. 26.
 The friction reduction was also confirmed and the reactions of cotters were obtained. Thus, the effects of friction and cotters on the restoring force characteristics were made clear.
 However, in the tests of Sashikamoi, the loading blocks moved due to large reaction of the point V. Thus the test results of Sashikamoi were excluded for the evaluation of EPM parameters for lack of reliability.
 As a conclusion, the simulated results of M-θ relations agree fairly well with the test results and the proposed formulations are confirmed to be adequate.

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The objective of this study is to make it possible to evaluate restoring force characteristics of Amida-shaped frames regardless of material (wood and polycarbonate) of horizontal members. To improve the deformability of Amida-shaped frames, we use polycarbonate which is transparent with high deformability as horizontal members. First, we conduct static loading tests of Amida-shaped frames composed of polycarbonate, then grasp the mechanical characteristics focusing on the difference between wood and polycarbonate. Next, we construct analysis models to express the embedment at joints. Finally, we verify the precision of analysis models by simulating experiments.

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Hybrid glulam timber beam reinforced with deformed steel bar (rebar) and epoxy resin adhesive is reported on followings:
1. Review of works of the hybrid timber beam, importance of increasing bending stiffness under short-term loading by 3-4 times of those of conventional glulam timber beam, and target of this study are described.
2. The hybrid timber beam adopted a large amount of rebar was tested by short-term loading.
3. Equations for allowable moment, bending strength, moment-curvature of the hybrid timber bam are proposed.
4. Equations for shear deformation of the hybrid timber beam are also proposed.

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 Recently, from view-point of Global Environment, timber, i.e., one of nature-cycle materials, has been tried to be utilized as structural members of large timber buildings in Europe and North America. A representative timber of the members is Cross-laminated timber (CLT), however, CLT structural system very often restricts planning of building because of CLT being plate member. High-stiffness-strength-timber slender beam and column are significantly desired.
 This study focuses a hybrid glulam timber with steel deformed bar (rebar) and Epoxy resin adhesive. Hybrid timber beams such as this study technique has been researched as we can recognize at several references^6)-17). No research, however, on duration of load factor of hybrid timber beam has been conducted.
 Aim of this study is to reveal duration of load (DOL) factor of the hybrid timber beam under bending load. We conducted short-term loading test and long-term loading test. The short-loading test was conducted to identify maximum loading capacity necessary for stress level in long-term loading test.
 The result of short-term loading test and its discussion are summarized as follows:
 (i) The number of specimens of hybrid timber beam and timber beam, which each have same cross-section, was ten. Standard deviation (σhy) of maximum bending capacity of the hybrid timber beams was 41% of that (σw) of the timber beams. Mechanism of the deviation reduction by rebar is worth to be researched furthermore;
 (ii) Standard deviation of bending moment at rebar yielding of hybrid timber beam is extremely small because same production rebars are used and property of the rebar is stable, whereas that of bending moment capacity of the timber beam is comparatively large because bending strength of timber is more variable;
 (iii) Bending moment－curvature curve of the hybrid timber beam can be precisely predicted by calculation using Bernoulli-Euler hypothesis and appropriate stress- strain curve of rebar and timber.
 The result of long-term loading test and its discussion are summarized as follows:
 (iv) Nearly all of the data of DOL factors of the hybrid timber beams tested were more than value of Madison curve and conventional timber beam, and DOL factor after 50 years of the hybrid timber beam is predicted to exceed DOL factor, i.e. 55%, required by Japan's Building Standards Act;
 (v) Equation (5) to predict DOL factor curve of the hybrid timber beam has been proposed, which is based on assumption: DOL factor of timber is calculated by Madison curve; all rebars have yielded in fracture of the beam, and; maximum bending moment capacity of the beam is equal to sum of its timber bending moment and its rebar bending moment. The equation predicted approximately experiment data of DOL factor of the hybrid timber beam: the all experiment data ranged within standard deviation (± σhy) of bending moment capacity of the beam in short-term loading to curve by Equation (5) as seen in Fig. 11 (b);
 (vi) Design methods of check to prevent bond failure around rebar and shear failure of web in the hybrid timber beam are described in order to ensure to fail under bending load. By the method, hybrid timber beam specimen of this experiment has been evaluated not to collapse by the bond failure and the shear failure after 50 years, and DOL factor after 50 years, which is predicted by Equation (5), has been evaluated to demonstrate its ability.

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 Structural engineers are encouraged to design reinforced concrete (RC) structures so that flexural yielding of RC members occurs first, to prevent shear failure that leads to sudden strength deterioration. In order to allow flexural yielding without exceeding the safety limit deformation of RC members, the deformation capacity has to be accurately assessed. Few methods are available to evaluate this deformation capacity since the failure mechanism of RC members after flexural yielding is still not well understood. The current AIJ Design Guidelines, Design Guidelines for Earthquake Resistant Reinforced Concrete Buildings Based on Inelastic Displacement Concept published by the Architectural Institute of Japan, provides a method to obtain deformation capacity using a compressive strut model with deteriorating strength as the plastic hinge rotates. This study considers a new failure mechanism for RC members failing in shear after flexural yielding due to concrete cracking and proposes a new method to evaluate the safety limit deformation.
 We conducted cyclic loading tests of three RC beams designed to fail in shear after flexural yielding and one RC column to fail in shear. The proportions of the bending to shear deformation were measured by image analysis using grid points drawn on the surface of the specimens. The results revealed that the proportion of shear deformation suddenly increased after the strength deterioration, which was defined as 90% of the maximum strength of RC member in this paper, occurred. Also, compressive strut failure was not observed in the tests. Based on the experiment results, the following failure process was considered: (1) concrete flexural cracks propagate near the critical section, (2) main reinforcements start yielding and bending-shear cracks propagate, (3) main bar yielding area extends and lateral reinforcements start yielding, and (4) crack width widens until the member strength deteriorates as the crack width is wide enough that the concrete aggregates cannot maintain the stress transmission mechanism.
 Then, we proposed a method to evaluate the safety limit deformation where the strength deterioration occurs. The proposed safety limit deformation was assumed to consist of three deformations: (a) flexural deformations in elastic area, (b) plastic deformation estimated based on the main reinforcement elongation, and (c) elastic shear deformation. The deformation (b) computed by the proposed method and the experimental deformation estimated by the photos of specimens were compared. The proposed method showed good agreement with the experimental results and the assumptions to estimate the plastic deformation was validated.
 To investigate the accuracy of the proposed evaluation method, the method was applied to 54 specimen data collected from previous experimental studies. Then, the method in the AIJ Design Guidelines was used for the data and compared to the new method. The results showed that the proposed evaluation method can better evaluate the safety limit deformation.
 The new method provides better estimations than previous methods, however, the estimations still have some scatterings mainly because of the variation of the strain hardening point. We investigated the appropriate assumption of the strain hardening point by parametric studies. As a result, we obtained factors of 6 or 7 for the strain hardening point to the yield strain for the safe side estimation, when the data is not provided. The estimation may improve with sufficient data of average and variation of the strain hardening points.

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 Generally, the bolting and welding are adopted as joint components in steel framed structures. In perspective, a connection of steel structures is divided into the rigid connection, the semi-rigid connection, and the pin connection by the fixation of the joints. However, these connection methods have some problems of workability on the construction site. Herein, a fitting type joint is adopted to the connection of the steel frames which requires the disassembling properties and any other purpose. In this study, a new type of connection technique for steel square tube is proposed (see Fig. 1). This proposed joint has fitting connector by embedding mechanism not using bolt or welding, and a pin is inserted as a fail-safe mechanism against the uplift. Here, we aim to control the ultimate state of the steel member with this connection considering the moment diagram. So this study investigates its resistant mechanism and restoring force characteristics subjected to bending. Furthermore, the analytical study by FEM analysis is performed to study the mechanical characteristics in detail. From these studies, the analytical model of this connection is proposed.
 First, the static cyclic loading tests are conducted as parameters with the position of embedded connection, the length and the steel grades of connector (see Figs. 4 and 5, Table 2). From the test results, the following ultimate states are observed; 1) plastic hinge formation, 2) out of plane deformation (see Fig. 9, Table 3), and the appearance of these ultimate states are influenced with the combinations of the embedded positon, the size and steel grade of the members. And also, it is confirmed that the test specimen with the longer connector shows the high rigidity and bending strength (see Figs. 6 and 7, Table 3). Furthermore, the test specimen with the longer connector presents the small slip and pinching behavior during cyclic loading.
 According to the ultimate state 2), it is predicted that the contact force is generated at the embedded parts. However, it is difficult to clarify the resistant mechanism related to the plate failure mode in detail. Herein, the FEM analysis is performed to investigate the mechanical characteristics with the yield line on the plate (see Fig. 11). From the comparison of the test results and FEM analysis, it shows the good agreements each other (see Figs. 12 and 13). So then, the contact force and the friction force between each members are presented (see Fig. 14). From these results, it is observed that these forces contribute the appearance of the bending moment on the connection (see Fig. 15).
 From these observations, the analysis model subjected to the bending on this connection is assumed for each ultimate states (see Figs. 16, 17, 19, 20). However, in the case of the failure mode with out of plane deformation, it is difficult to determine the yield line on the plate theoretically. Herein, the 3D modeling method is adopted to visualize the ultimate state (see Fig. 18). From the 3D model, it can help to make the plastic analysis model (see Fig. 20). And by comparison of analytical results and test results, it can predict the restoring force characteristics well (see Table 4). Furthermore, it can help to control the ultimate state of the member with this connections using the proposed analysis models (see Fig. 21).

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 Lattice damping wall system using torsional steel tube dampers at the crossing position is proposed. As indicated in the Fig. 1, this system composed of vertical steel bars, horizontal steel bars, and circular steel tubes. In this study, the formula for evaluating elastic stiffness of damping wall system considered stiffness of lattice bars is introduced. Then, validity of the formula for evaluating elastic stiffness is verified by FEM analysis and experiment of pure shear partial model arranged 4 steel tubes.
 The model considered the calculation of the stiffness of damping wall system represents damping wall system installed in center-to-center of column-beam frame. It is shown in Fig. 2. The deformation of damping wall system consists of deformation of circular steel tubes and one of lattice bars, as shown in the Fig. 3. Torsional deformation causes in circular steel tubes, and bending shear deformation causes in lattice bars. The model to compare FEM analysis with calculated value is the same. The model of FEM analysis consists of beam element. As indicated in the Fig. 5, the calculated stiffness and full plastic shear strength correspond to the analysis result.
 The test specimens are partial model arranged 4 steel tubes. It is shown in Fig. 6. The parameters of test specimens are thickness of steel tubes, length of steel tubes, thickness of lattice bars, and width of lattice bars. In this experiment, pure shear type loading device was used for cyclic loading, as shown in the Fig. 7. In the cyclic program, all test specimens showed steady hysteresis behavior.
 From the results of test and analysis, the following findings were obtained.
 (1) The formula for evaluating elastic stiffness of the damping wall system correspond to the result of FEM analysis. The model of FEM analysis consists of beam-element. The full plastic strength calculated the formula driven also correspond to the result of FEM analysis.
 (2) The ratio _eK/_cK (experimental values/calculated values using the formula introduced) of elastic stiffness of the damping wall system introduced to one of the test result is 0.91 to 1.06.
 (3) The ratio _eQ_p/_cQ_p (experimental values/calculated values using the formula introduced) of full plastic strength of the damping wall system introduced to the test result is 0.82 to 0.87. There is some possibility of an effect of welding heat.
 (4) In this experiment, equal torsional deformation caused in the four steel tubes in the elastic region. Because, in the elastic region, shear strains calculated from the values of tri-axial strain gauges passed on in side of them showed equal values. In the plastic region, the shear strains of steel tubes aren't equal. However, the four steel tube dampers share torque equally.

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 In recent years, since steel plate reinforced concrete structure (hereinafter abbreviated as SC Structure) is expected to contribute to shortened work periods and less impact on environment compared to conventional reinforced concrete structure, it is applied in shear walls in nuclear power related facilities and turbine pedestals in addition to ordinary buildings. Because the thickness of the floor can be several meters when applying SC Structure to horizontal member such as floor slabs in nuclear power related facilities, gaps appear in the back of upper steel plates due to concrete contraction or settlement after casting (as in Fig. 2). Therefore, it may result in degrading the slip preventing performance of headed stud. However, the effect exerted by the presence or absence of gaps to mechanical properties of SC structure has yet to be elucidated. Authors conducted a push-out shear test of stud with gaps as a first step in order to grasp the effect exerted by gap caused in the back surfaces of steel plates to mechanical properties of SC structure after casting. The test results have proven the tendency that the maximum bearing force decreased with increasing the thickness of gaps and the displacement at the maximum bearing force increased. In addition, the evaluation formula of the stud sheer strength considering gaps was proposed. In this paper, loading test of SC structure beam member simulating gaps caused in the back surfaces of steel plates was conducted and impact on the slip preventing performance of studs by gaps was assessed. The following knowledge was obtained from the results.
 According to the measurement results of relative displacement (referred to as slip displacement) in interface between steel plates and concrete, vertical slip displacement is minute compared to horizontal slip displacement and horizontal component is dominant. Furthermore, the relationship between the horizontal slip displacement and the axial strain of steel plates was confirmed by the experiments. In regard to the relationship between the stud sheer forces considering gaps and the slip displacement (Q-S relationship), the calculating method of the slip displacement (S_y) at the yield point was proposed. Q-S relationship model of sheer strength and S_y as a parameter was also constructed. From the comparison of past test results and analysis results by model, the applicability was determined and indicated S_y is substantially constant regardless of thickness of gaps. Based on the equilibrium of force in interface between steel plates and concrete, the equation related to horizontal slip displacement was derived. The steel plate strain and the stud slip displacement calculated by this equation mostly expressed test results. From the test and analysis results, it is confirmed that the load-displacement relation of the beam member with gaps is almost the same as the relationship of the member without gaps if the stud slip displacement is S_y or less. Although the test case is limited, it is found that the stud slip displacement under S_y is important in order to maintain the structural performance on part concerned in generation of gaps.

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 The research used the seismic synthesis angle to consider the effectiveness of ground improvement work against overturning and sliding during seismic conditions on test specimens that had ground improvement implemented on the back face of the L-type retaining wall (L/H = 0.7). A comparison was made between a conventional L-type retaining wall with no ground improvement and three test specimens with different ground improvement profiles. The main items discovered in this research were as follows.
 1) The trend in the safety factor for overturning on test specimens with ground improvement was that the highest values were on the [θ = 30°] test specimen followed in order by the [θ = 15°] and [θ = 0°] specimens. Furthermore, as the base angle increased (θ1 = 0° to 15°), the safety factor for overturning decreased on all three test specimens and the safety factor when there is slip line occurrence showed almost the same value (1.6 to 1.7).
 2) The safety factor for sliding on test specimens with ground improvement was [θ = 30°] > [θ = 15°] > [θ = 0°], in the same order as the safety factor for overturning. Furthermore, the safety factor trended below that for overturning on all of the test specimens and the safety factor when there is slip line occurrence was around 1.0 on all three test specimens.
 3) The angle ω_T formed between the earth surface and the slip line on test specimens with ground improvement was close to the Mononobe-Okabe theoretical value ω and showed just a slightly smaller value on all of those specimens.
 4) The lateral seismic factor k_h when there is slip line occurrence was greater than the ultimate limit state lateral seismic factor k_h=0.25 on all of the test specimens.
 5) The lateral seismic factor k_h when there is slip line occurrence on the test specimens with ground improvement was the largest on the [θ = 30°] test specimen followed in order by the [θ = 15°] and [θ = 0°] specimens. In the same way, the k_h on the [θ = 30°] test specimen was higher than on the [L/H = 0.7] test specimen and the values for the [θ = 0°] and [θ = 15°] test specimens were smaller than for [L/H = 0.7].

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