It is significant to accurately grasp the pressure loss per unit length of pipeline in calculating total pressure of pipeline. The standard value of pressure loss per unit length of pipeline is shown in recommendation for practice of placing concrete by pumping methods. The standard value of pressure loss per unit length of pipeline were obtained from pumping experiment conducted around 1970. But, mix-proportion and concrete materials has changed compared to the 1970s. Especially, design strength has risen compared to the 1970s, and high-range AE water reducing agent was developed and has spread. Therefore, concrete that has been used recently can't apply the standard value of pressure loss per unit length of pipeline.
 So this study aimed to reveal influence of mix-proportions on the pressure loss per unit length of pipeline by literature survey and pumping experiment. In the first, we studied the influence of water-cement ratio on the pressure loss per unit length of pipeline. Pressure loss per unit length of a pipe tended to be roughly proportional to the square of cement-water ratio. Next, we examined pressure loss per unit length of pipeline for each slump of concrete that more than W/C 45%, and we examined pressure loss per unit length of pipeline for each unit water content of concrete that less than or equal to W/C 45%. As a result, pressure loss per unit length of pipeline tended to increase when slump decrease and unit water content is low. And we derived the relational expression between pressure loss per unit length of pipeline and true output capacity. In additions, this paper proposed standard value of pressure loss per unit length of pipeline of concrete that more than W/C 45% on the basis of literature survey results. Finally, we confirmed the validity of the relational equation obtained from literature survey by pumping experiment.
 This paper shows a result of pressure loss per unit length of pipeline of concrete with normal portland cement. Therefore, we should does experiment of test pumping with reference to result of this paper when we use concrete with cement and materials other than normal portland cement.

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 A seismic ground displacement provides us the usable information to the analysis of the seismic source mechanism, the soil characteristics, the building damage, and so on. Especially, a huge residual displacement may cause a large response of long-period structures such as tall buildings and base isolated buildings.
 The accelerogram recorded by the servo sensor is often affected by the baseline irregularity due to the tilt motion of the sensor and the low-frequency noise, causing the difficulty of the estimation of the displacement including the residual component. In such case, the displacement is obtained by following two steps: the baseline change correction and the integration. In the first step, the irregularity of the acceleration baseline is corrected by eliminating the step function component in the frequency domain. Subsequently in the second step, the displacement is computed by integration using the real part of the Fourier spectrum.
 In the above mentioned scheme, however, usage of the low-cut filter may cause the deformation of the waveform and the underestimation of the residual displacement. In this study, the seismic ground displacement is obtained from the acceleration record by using a new technique. In the new method, the low-frequency noise is canceled replacing the original spectrum by that of the appropriate trapezoidal function, instead of using the low-cut filter. The parameters of trapezoidal function used are determined by the spectral fitting.
 Applying the method to the acceleration record of the 2016 Kumamoto Earthquake, the displacement is estimated accurately including the residual component. Particularly, the convergence of the displacement waveform in the coda part improves. In addition, the distribution of the residual displacement obtained by the method is almost consistent with that from GNSS observation.

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 In construction sites, when falling of lifted objects occur and the falling objects pass through underlying slabs, severe harm may be caused to persons under the slabs. Especially, when construction sites are located above public passages such as roads or railroad tracks, harms may be caused to not only construction workers but also unrelated third parties who use such passages. Therefore, it is important to ensure a sufficient safety for workers and third parties who are under the construction site in case a lifted object falls onto a reinforced concrete (RC) slab.
 Significant studies on projectile penetrating RC slabs have been carried out. Those studies proposed some empirical formulae for penetration or perforation limit. Collision problem dealt with in this study has some different features as to the ones reported in those previous studies. Falling objects in construction sites tend to be heavier and have lower velocity than the projectiles of mentioned previous studies. Floor slabs which are treated as collision targets in this study are thinner than the slabs of those studies from the perspective of the ratio of slab thickness to diameter of projectile. Therefore, the behavior of RC floor slabs is not clear when they are subjected to impact loadings by falling objects during construction.
 In this study, full-scale drop test and numerical simulations were conducted to examine the behavior of RC slabs subjected to collision of falling objects. Test specimens were made assuming generally used slabs in steel structure buildings in Japan. The specimens have 150mm thickness and constructed on steel deck plates which were considered as non-structural formworks. A falling object was made of a square tube and its mass was about 2.3t. The analytical model was made to replicate the shape of the specimens by finite element meshing. The numerical simulation was satisfactorily and validated by the experimental results. The numerical analysis could reproduce the state of damage of the slabs and time history responses observed in the experiment.
 The experimental and analytical results showed that the falling objects could not perforate completely the slabs even when the assumed falling conditions were beyond the perforation limit predicted by the empirical formula proposed by Degen. The falling objects did not fully pass through the slabs when falling heights were 10m and 15m although the calculated perforation height limit was 8.3m considering similar condition as those of the experiment. N=0.72 was adopted in the empirical formula as the shape factor of the tip of the falling object. The diameter of the falling object was adjusted in order that the perimeter of the circle was equivalent to that of the falling object.
 The empirical formula seemed able to predict the variation in the failure mode of the slabs. When falling heights were within the perforation limit, concrete at collision points didn't fail completely. On the contrary, concrete at collision points failed completely and reinforcement bars were exposed when falling heights were beyond the perforation limit. In addition, analytical results showed that strain energy of concrete did not significantly increase relative to the increasing of falling heights when falling conditions were beyond the perforation limit. In contrast, strain energy of reinforcement bars increased proportionally to the falling heights.

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 In early days as in the 1940s, a partial cylindrical concrete shell (often referred to as long shell) was frequently used as a barrel roof structure. A simple guide was proposed as to the buckling of a long shell in the ASCE Manuals of Engineering Practice (1952), by making use of the theoretical buckling load of a circular cylinder subjected to the action of uniform axial pressure.
 It is to be noted that a strict membrane stress field is difficult to be maintained in a barrel-roof-type shell, because the number of stress unknowns is unfit for the number of available boundary conditions. Accordingly, for a long shell, use has been made of approximate membrane stress states in a “shallow” partial cylinder under external lateral pressure in not only a linear stability analysis but also a non-linear large deformation analysis.

 In a previous paper, the present author has shown that a cantilever-supported shell segment cut out from a circular cylinder with particular shapes and boundaries is able to satisfy the condition of a membrane stress field, under the action of a variety of loads; by assuming strain-displacement relations stay linear until buckling takes place, the stability of the shell segment can be analyzed as an eigenvalue problem.

 To be examined in this paper are two examples that are regarded as being typical and comprehensive. Each loading of self-weight and earthquake excitation is considered for varying thicknesses and shapes. Initiated with nonlinear equilibrium equations which are known as Love's Formulae and referred to as “general case” by Timoshenko, simplification is made by estimating non-linear terms with reference to the order of magnitude. Based on the assumption that the linearity of load-displacement relations remains valid until buckling takes place, above equations are led to equilibrium relations valid for an early post-buckling stage. These are made discrete through FEM formulation in Galerkin type weak form, being led to a system of equations in conformity with a linear eigenvalue problem. Further study is made to see how each parameter influences on partial matrices appearing in the overall FEM formulation.
 (In appendices at the end of the paper, the results of an analysis on an example of eigenvalue problem are compared with the results from the classical theory of elastic buckling, leading to perfect coincidence.)

 Linear buckling analyses are then conducted for each of the two load cases as eigenvalue problems by varying thickness and shapes as parameters. Results are shown for the load factors of buckling as contour lines in a plane of parameters; radial displacements of free edge lines are drown overlapped, representing modes of buckling for each combination of the parameters.
 It is intended to show general buckling characteristics of the shell in the form of graphics over the parameters varying widely.

 Finally, a large deformation step-by-step analysis is carried out, by converting the non-linear weak form led from the calculus of variation into a matrix form by making use of the predetermined values in the preceding step. An analysis is repeated for each load level, modifying the fore-going matrix step-by-step, until the displacement converges.
 Consequently, it is shown diagrammatically that buckling occurs at the minimum load level that the displacement does not converge but diverges, and that a large displacement appears suddenly with the same mode as that of linear buckling. Material behavior is assumed to be linearly elastic, throughout the paper.

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Numerous steel roof bearings in RC gymnasia were damaged at the 2011 Tohoku and 2016 Kumamoto Earthquake, mainly due to out-of-plane response of cantilevered RC walls. Although the authors confirmed the reduction effect for seismic response of cantilevered RC walls by friction damper bearings, the transverse response evaluation methods including the roof response are not established. In this paper, using the experimental results of a PTFE sliding bearing, a friction damper bearing, and a rubber sheet bearing, the transverse response of RC walls are analyzed by numerical simulations including effects of the roof response, followed by proposing the evaluation methods.

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 In order to grasp the relationship between bearing capacity and deformation of mud walls, full-scale tests that require considerable economical and time investments are needed. Therefore, we have studied on the estimation formula for the relationship between bearing capacity and deformation of mud walls without openings based on soil mechanics. The objective of this study is to estimate the relationship between bearing capacity and deformation of mud walls with opening by the mechanical characteristics of wall clay obtained from the results of material tests.
 In order to grasp the fracture mode of mud walls with opening, full-scale lateral loading tests for specimens with hanging walls and siding walls are conducted. As shown in Figure 1, the length and height of specimens are 3640mm and 2767.5mm, respectively. Total 4 specimens are selected to examine the effect of reinforcement at the connection of column-to-lintel. The maximum load of specimen with reinforcement is almost same as that of specimen without reinforcement. However, the deformation angle at maximum load of specimen with reinforcement is smaller than that of specimen without reinforcement owing to the effect of reinforcement at the connection of column-to-lintel. Regarding the fracture mode, the hanging walls and siding walls are collapsed with initial failure in compression or pull-out of lintel and compression.
 The mechanical model to estimate the relationship between bearing capacity and deformation of mud walls with opening is proposed based on soil mechanics. The material characteristics of wall clay is determined from the results of unconfined compression tests as shown in Figure 4. The relationship between bearing capacity and deformation of the hanging and siding wall is estimated considering two types of fracture mode with initial failure in compression and pull-out of lintel and compression. As a result, the relationship between bearing capacity and deformation of mud walls with opening is estimated considering the deformation of columns, hanging walls and siding walls as shown in Figure 10.
 The estimation results are compared with the experiment results to evaluate the accuracy of the proposed method. The estimation results are almost the same as the experiment results. However, there are some variations between estimation and experiment results owing to the simple mechanical model. The average value of the ratio of the experiment value P_eu to the estimation value P_cu is 1.08, and the variation coefficient is 0.08 as shown in Figure 18. Therefore, it is found that the proposed method is available for mud walls with opening.

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In this paper, for traditional timber buildings with large hanging walls, we reveal the effect of the seismic reinforcement by rotational restraint of column base for the purpose of strength improvement. The followings are considerations in seismic reinforcement by rotational restraint of column base. i) The reinforcement can improve strength of the structure, while it is possible to reduce deformation performance. ii) To effectively obtain strength improvement in the reinforcement, it is important to properly evaluate the decrease of rotational restraint of columns at the joints as the structure deforms and the flexural capacity reduction of columns.

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 For seismic design of high-rise RC structures, to secure safety against large-scale oceanic earthquakes and epicentral earthquakes and to enhance the damage controllability for repeated deformations over large numbers of repetitions owing to long-period ground motions, producing high-strength RC structures by using primary reinforcements with higher strength than the standard ones was considered to be effective. Furthermore, for seismic design of high-rise RC structures that are critical as social capital, in addition to examining the damage of a medium-scale earthquake and securing the safety against collapse/overturning to a large-scale earthquake, evaluating the seismic performance to a continuous input level and the performance design was required, to evaluate various performance requirements.
 On this basis, to realize high-strength RC structures, this study aimed to grasp the damage and to evaluate the skeleton curve of the high-strength RC beam and its hysteretic characteristics, such as hysteresis responses to repeated loading over several cycles, and to investigate the response of a high-strength RC beam subjected to cyclic loadings. Therefore, examinations aiming at clarifying the above-mentioned aspects were conducted using structural tests and analysis.
 First, to understand the effect of the cyclic loadings on the restoring force characteristics of the high-strength RC beams, structural tests were conducted and the effect on the restoring force characteristics was examined, such as strength deterioration owing to cyclic loadings. It could be confirmed that the maximum residual crack width after unloading- ductility factor relationship in high-strength RC members. Furthermore, examining the skeleton curve of the high-strength RC beams using high-strength primary reinforcement (USD 590, USD 685), it was found that the modified equation where a correction coefficient is multiplied by the calculation formula of rigidity lowering rate of the yield point for standard RC beams can evaluate the skeleton curve for the results of this test. Next, finite element analysis was carried out to reproduce and extend the understanding of the test results. The analysis results agree well with the test results. A parametric analysis was performed with the strength of rebar, tensile reinforcement ratio, and shear span ratio as a parameter. From the parametric study, the stiffness decreasing rate of the high-strength RC beams was examined.
 Finally, by comparing the results of the test with the hysteretic model where the changes in the restoring force characteristics are considered, for instance with slip characteristics and strength deterioration owing to the cyclic loadings, the set values of the parameters to determine hysteretic characteristics were examined.

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 Post-installed adhesive anchors are used in external seismic retrofitting joints for existing reinforced concrete buildings. As a structural characteristic of external seismic retrofitting, the existing frame and reinforcing frame are eccentric. Therefore, in addition to the shear force, there are also compression force and tensile force due to the eccentric bending moment acting on the joints, so that the joints are in a combined stress state in external seismic retrofitting. There are few studies on post-installed adhesive anchors under a combined stress state, and it is difficult to grasp in detail its mechanical behavior when subjected to combined stress. For that reason, the current design method suggests the use of reduction factors which are based on engineering judgment.
 This paper investigates the mechanical behavior of the post-installed adhesive anchors under combined stress by constructing 3D FEM model which can reproduce the experiment conducted in a previous research. A total of 13 specimens of varying parameters, i.e. anchor diameters, d_a, axial stress ratios, η and concrete strengths, F_c, are studied. Based on the analysis results, the influence of each parameter is investigated in terms of (1) shear force vs. relative horizontal displacement relationship, (2) curvature distribution of anchor bolts, (3) Mises stress distribution in anchor bolts, (4) damage states in concrete and (5) minimum principal stress distribution in concrete.
 In Chapter 2, the outline of the experiment and the details of the specimen parameters which are the subject of the analysis are introduced. In Chapter 3, the outline of the analysis model is described. The concrete, grout and anchor bolts are modeled by hexahedral elements (eight-node isoperimetric elements). The epoxy resin between the concrete and anchor bolts was modeled by joint elements (eight-node isoperimetric joint element) with thickness. Furthermore, depending on the interface properties, zero-length joint element are applied to model the bonding properties between different materials.
 The analysis results of the shear force versus relative horizontal displacement relationship show generally good agreement with the experimental results. For the specimens subjected to combined shear and tensile force, the following phenomena are observed. (1) The maximum curvature of the anchor bolt occurs at 2d_a (where d_a is the diameter of the anchor bolt) depth from the joint surface on the concrete side and 1d_a depth on the grout side. When the relative horizontal displacement reaches 2.0 mm, a total length of 5d_a is yielded in the anchor bolt: 3d_a on the concrete side and 2d_a on the grout side. (2) The Mises stress of the anchor bolt on the tensile side increases when the axial stress ratio increases. In this condition, the anchor bolt yields earlier due to the tensile stress and therefore the shear stress decreases in the cross-section of the anchor bolt. (3) In the specimens subjected to both shear and tensile force, cracks occur in the concrete due to dowel deformation and tensile stress. Meanwhile, the damage of the concrete increases when the axial stress ratio increases. (4) When the anchor diameter and the concrete strength increase, the bearing stress of the concrete also increases, and the concrete is compressed and softened in a wider range. (5) The maximum value of the minimum principal stress increases as the concrete strength and the axial stress ratio increase.

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 The AIJ published a Recommendation for Mix Design, Production and Construction Practice of Concrete with Recycled Concrete Aggregate in October 2014 to present more specific methods of using recycled aggregate concrete with recycled aggregate classes H to L for building applications. In consideration of establishing a sustainable recycling system, this study focused on recycled aggregate class L, which has the lowest quality among recycled aggregates, and investigated the load carrying capacity of reinforced concrete beams. For investigation of the load carrying capacity of the beams, focus was placed on the bond splitting strength of lap splices, which are used as basic reinforcing bar joints.
 In general, concrete with low quality recycled aggregate class L is not completely devoid of the mortar attached to the original aggregate included in the recycled aggregate. It has been reported that concrete with low quality recycled aggregate at a high substitution rate shows a higher drying shrinkage percentage and a higher number of drying shrinkage cracks. Another report revealed that normal concrete can be reinforced with vinylon fibers to have higher crack dispersibility. Based on these reports, it was decided to apply recycled aggregate concrete with the addition of vinylon fibers for the purpose of reducing drying shrinkage cracks in concrete with recycled aggregate class L, to reinforced concrete beams.
 Three series of concrete specimens were prepared. As normal concrete specimens for examination of bond splitting strength, the 00 Series was taken as reference. Specimens of normal concrete mixed with 50% low quality recycled coarse aggregate were named, the 500 Series. Those mixed with 30% low quality recycled coarse aggregate and 15% low quality recycled fine aggregate were named, the 3015 Series. For each of these two series of recycled aggregate concrete specimens, those with vinylon fibers and those without vinylon fibers were prepared. The vinylon fibers used in this study were synthetic fibers produced from polyvinyl alcohol as a raw material. Vinylon fibers with a standard length of 12 mm and a diameter of 100μm were added to the concrete at a rate of 0.2% of the total concrete volume.
 In these experiments, the following findings were obtained.
 The series with a low substitution rate of recycled coarse aggregate (3015 and 3015V Series) showed a tendency of having less drying shrinkage cracks. No significant differences in drying shrinkage cracks in the recycled aggregate concrete beams existed between with and without vinylon fibers.
 The bond splitting strength after one year was found to be higher than after five weeks because the compressive concrete strength increased. No tendency related to differences between normal concrete and concrete with recycled aggregate class L, or between with and without vinylon fibers, was identified. All these specimens showed the same bond splitting strength.
 The experimental result was divided by the calculated value of the bond splitting strength formula for lap splices to obtain the bond splitting strength ratio. The ratio for concrete beams with recycled aggregate class L was equal to or even higher than that for normal concrete beams. This indicates that the bond splitting strength formula may be also applied to beams with recycled aggregate concrete.

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 It is thought that the previous equation for the flexural ultimate strength of shear walls with an opening has enough accuracy. But, it was found that the calculation results for flexural strength ratio of shear walls with an opening to shear walls without an opening by the previous equation became often bigger than experiment and FEM analysis results. So, the flexural resistance mechanism of shear walls with an opening was investigated by FEM analysis, and the proposed method for the flexural ultimate strength for shear walls with an opening was developed.

 By experiment and FEM analysis results, the following knowledge was obtained.
 1. The flexural strength is influenced by position, width and height of door shaped opening.
 2. The loading moment ratio of the tensile region decreases, if an opening is at the compressive side edge of wall panel.

 Assumptions of the proposed method are the following.
 1. The flexural moment at leg of wall is shared by the flexural stiffness of the tensile region and compressive region, and the flexural stiffness composed of the axial stiffness of the tensile region and compressive region.
 2. If the tensile force of the tensile region becomes bigger than the axial force loading before horizontal force loading, the flexural stiffness of tensile region is decreased.
 3. The flexural cracking strength can be calculated by the moment sharing ratio proposed for calculating the flexural ultimate strength.

 It was found that the calculation results for flexural strength ratio of shear walls with an opening versus shear walls without an opening by the proposed method corresponded well with experiment and FEM analysis results.

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 The main purpose of this study is to verify the ability and the limitations of the multiplicative viscoplastic constitutive model and the finite element method for the prediction of time-dependent creep behavior of SM490 steel at elevated temperatures.
 In the previous paper¹⁾, the uniaxial multiplicative viscoplastic model was selected for the time-dependent mechanical behavior model of structural steel SM490 at elevated temperatures, and the material constants of the model were identified using only the stress-strain-strain rate data of uniaxial tensile tests under two different tensile speeds. Also, based on the comparison of calculated creep curves under constant loads from viscoplastic model and tested creep ones, it appears that one can predict the creep response under constant loads of structural steels reasonably well using the viscoplastic constitutive model.
 In this paper, the developed uniaxial viscoplastic model was implemented into a general-purpose finite element program, and the simulations of uniaxial creep tests and bending creep tests of SM490 structural steel specimens were carried out. The analysis of the behavior of viscoplastic structures under realistic conditions requires the adoption of an adequate numerical framework capable to generate approximate solutions within reasonable accuracy. In this paper the approximate solution to such problems is addressed within the context of the Finite Element Method.
 In summary, the following results were obtained from the finite element analysis:
 1) In the case of uniaxial tensile tests under two different tensile speeds, due to the calculated results with finite element method were almost identical to those of tested results, it was confirmed that the effect of strain rates on the stress-strain curves of tensile tests was expressed reasonably well with the use of the multiplicative viscoplastic model and the viscoplastic finite element procedure.
 2) In the case of uniaxial creep tests, the simulated creep curves at the highest applied stress level corresponded with the actual creep responses, and the predicted creep curves at low strain levels gave a little variation. This discrepancy suggests the necessity to develop a more appropriate mathematical form of viscoplastic model.
 3) In the case of bending creep tests, the numerical results and the experimental ones showed relatively good agreement except for the 450°C case. In this case, numerical results seemed to range from 1.2 to 1.3 times larger than the experimental ones. These discrepancies mainly depended on the lack of the materials constant data at 450°C, and suggest the necessity to develop a more appropriate mathematical form of viscoplastic model.

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 In Japanese moment resisting steel frames, H-shaped beams are rigidly connected to the box sectional columns which have high warping restraint against lateral buckling deformation of beams subjected to flexural moment. On the other hand, most of beams in frames are connected with continuous braces such as roof purlin or concrete slab which are effective to prevent the lateral buckling of beams. In this paper, the equation of the elastic lateral buckling load for H-shaped beams with warping restraint and continuous braces are developed. Elasto-plastic lateral buckling stresses of the beams and lateral stiffing force and rotational stiffing moment of continuous braces are evaluated by the energy method and numerical analyses.

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 Square steel tubular columns are widely used in moment resisting frames. The moment resisting frame system will resist the horizontal load action through the flexural manner of the columns. Therefore, the columns will subject the axial force and the bending moment simultaneously. Under the seismic action, the effect of the bending moment that is the result of the shear force subjected to the column will be significant; the structural safety of the column at the ultimate limit state (ULS) shall be guaranteed. Recommendation for Limit State Design of Steel Structures and Recommendation for Plastic Design of Steel Structures specifies the requirements for the column to guarantee sufficient strength and ductility at the ULS. However, the appropriateness of requirements for square steel tubular column is not verified clearly. The test results, where the square steel tubular columns are under compressive axial force with different moment distribution, were reported in the previous papers. In this paper, structural performance evaluation of square steel tubular column is conducted based on the existing test results. Collapse mode, maximum bending moment, plastic deformation capacity, and moment amplification factor are evaluated; comparison study between the current design recommendation is also shown.
 This study revealed the following results.
 1) The design requirement (Eq. (2)) that is specified for the column expected to form the plastic hinge provided conservative results. The gap between the collapse mode observed from the testing and that is expected in the design requirements gets larger when the moment distribution will get close to antisymmetric bending moment. In this study, Eq. (10) is shown to evaluate the collapse mode reasonably. Moreover, Eq. (10) still fulfill the required minimum plastic deformation capacity that is stipulated in the recommendations.
 2) Design strength of the column which will not fulfill the requirements for the column to form plastic hinge showed conservative results when it was computed from current recommendations. The design strength computed from the old version of the recommendation provided more reasonable results.
 3) Moment amplification factor that is used to evaluate the Pδ effects was compared with the test result. It was confirmed that some columns showed unconservative results at the ultimate limit state. The column categorized to have no Pδ effects per Eq. (14) but could not resist full plastic moment (i.e., M_pc) during the test showed large second-order effects. In this case, the maximum bending moment through the column cannot be evaluated appropriately. However, this kind of phenomenon was observed in two specimens only. A further study shall be needed for the evaluation.
 4) Large deviation was observed at the plastic deformation capacity of the column under the double curvature bending when it was compared with the formula that is proposed for one end bending moment condition. From the regression analysis, the formulae that will evaluate the plastic deformation capacity of the column were shown. The derived formulae are not including the parameter of the width-to-thickness ratio; therefore, further study shall be needed for the proposal.

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 Bearing walls in which circular steel tubes are closest-packed in column-beam frameworks have excellent characteristics as earthquake-resistant repair elements. The purpose of this paper is to present a simple model that can analyze the large deformation area with good convergence. One of the mechanisms that resists the seismic force of this wall is an out-of-plane bending deformation mechanism of the tube, and Yield Line Theory is often applied to evaluate its maximum strength.
 In consideration of rotational symmetry, the upper half of a circular tube was modeled (Fig. 2). Yield lines 20, 40, 80, 100, 140 and 160 having a hinge moment _hM are provided at positions separated from the rigid lines 0, 60, 120 and 180 by an angle η. Elements 10, 30, 50, 70, 90, 110, 130, 150 and 170 are rigid bodies and the element length is invariant. A horizontal displacement corresponding to the displacement w δ at the top of the wall is given to the nodes 60 and 120 and a condition for minimizing the sum of the absolute values of the hinge rotation angle increments of the nodes 20, 40, 80, 100, 140 and 160 is given, convergence calculation is performed , and obtains the rotation angle of the elements 10, 50, and 110. Because of the rotational symmetry, the rotation angle of the element 170 is equal to the rotation angle of the element 10.
 The total of hinge rotation angle increment of all the circular steel tubes in the wall multiplied by _hM is the increment of the inner work of the wall. The increment of internal work is set equal to the external work increment and divided by w δ increment is the wall shear force. Residual deformation occurs when unloading external force, but since the yield line has a rigid plastic rotation spring, the residual deformation is the same as before the unloading. This is called a vertical displacement free model (hereinafter referred to as a free model).
 The axial displacement of the side column is restricted by the side columns, and the hinge rotation deformation of the rigid body and the yield line given by the yield line theory can not evaluate the restraint situation of the axial displacement of the side column. The side column axial displacement restraint model (hereafter called constraint model) constructed by this paper introduces a new circumferential direction linear slider in elements 30 and 150. This slider is one given a unidirectional property which permits elongation displacement with slider resistance _sR but does not allow shrinkage displacement.
 The value of the unknown η that defines the yield line position is almost constant as 0.305, and the rotation angle of the elements 50 and 110 hardly occurs. This is presumed to make the convergence favorable.
 It is supposed that the increment of inner work multiplied by _sR in the circumferential direction displacement obtained from the coordinates of the nodes 20, 30, 140 and 160 at the time of unloading of the external force of the free model is the difference between the free model and the constraint model. The scope of application of the presented model guaranteed by the experiment conducted to verify the validity is that the steel tube diameter thickness ratio is 55 or less, the yield ratio is 0.83 or less (limited to Round-House type), the welding length ratio is 0.53 or more, the wall thickness ratio is 0.13 or more, the aspect ratio is 0.48 or less, the member angle of 9/1000 or more, and 90/1000 or less. Experimental results revealed that calculated values using presented models correspond well to experimental values.

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 It is considered that cold-formed thin-walled steel structural members, which possess large width-thickness ratio, mostly exhibit local buckling behavior at both ambient and high temperatures. To verify both load bearing and deformation capacity, various experimental approaches represented by a stub column test under compressive force have been conducted and the evaluation methods on the local buckling performance have been proposed. A concept of “effective width” based on elastic buckling strength of a plate and load-distribution capacity of the buckled plate is widely used to estimate the maximum load-bearing capacity of the thin-walled steel column at structural design of the ambient temperature. On the other hand, those evaluation methods for fire resistant design in Japan have not been established, because the design method has been proposed for the heavyweight steel structures using shape steel members and thick steel plates. It is well known that stress-strain relationships at the high temperature show strong nonlinearity within a small strain range, there is, therefore, a possibility that the concept of the effective width based on the elastic local buckling strength cannot be applied for the evaluation methods at the high temperature. Main purpose of this study is to clarify the local buckling performance at high temperatures for thin-walled steel thin square hollow section members by conducting the stub column tests and propose the evaluation methods on the maximum load bearing capacity at the high temperature by using the modified effective width formula.
 The stub column tests under a condition on constant temperature and monotonic loading were conducted. The compressive force was gradually applied for a stub column specimen after heating it by an electric furnace. The JIS SS400 steel plate (thickness: 1.6 mm) is used for the specimen. Both width-thickness ratio (B/t = 50, 65, 80) and test temperature (RT, 400, 600, 700, 800 °C) are used as experimental parameters. Loading of the compressive force at the stub column test was continued after a peak point of that was observed, because of estimating the residual strength at the post local buckling behavior. From minute investigations on the stub column test results, the following knowledge was obtained.
 The loading peak points for all the stub column test results were observed after the local buckling behavior exhibited in the specimen, it is, therefore, considered that adapting the concept of effective width to the fire resistant design is reasonable to quantify the maximum load-bearing capacity. However, all the experimental results had the lower maximum strength than the results estimated by the past effective width evaluation formula. The modified effective width evaluation formula, which respectively substitutes the stress at 0.2 % strain and a secant stiffness at that stress for Young's modulus and the yield point, was proposed. By using this modified evaluation formula, the maximum strength at the high temperature can be satisfactorily estimated. It was, furthermore, clarified that the residual strength after the peak strength for the stub column test result approximately corresponds the estimation value obtained by the existing formula, which has been proposed by the AIJ Recommendations for Fire Resistant Design of Steel Structure (AIJ, 2017).

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 If a disaster such as an earthquake occurs, buildings will suffer damages, including residential houses and public facilities. An investigation of damaged buildings is very important in disaster areas because we use such data to make decisions for the implementation of disaster management and restoration plans. However, in the event of a large-scale disaster, conducting a detailed survey has several problems. The number of buildings to be covered will increase, manpower will be insuffficient, the burden on workers will increase, restoration will take time and will be delayed. Therefore, there is a need for a quick and accurate method of investigating building damages.

 In this study, we allowed a CNN (convolutional neural network) to learn the local and aerial photographs of the 1995 Kobe earthquake and verified the possibility of assessing building damages in the CNN based on the learning curve and discrimination accuracy. The Nishinomiya Built Environment Database, which contained damage certificate data, aerial and field photographs, and their shooting points, was used for analysis. In the Nishinomiya city's damage certificate data, the damaged buildings were classified into four classes: “severe,” “moderate,” “slight,” and “undamaged.” However, in the present study, three classes—moderate, slight, and undamaged—were merged into a single class for simplicity, such that we had a two class classification problem, that is, “severe” and “others.”

 First, when we created a data set using the damage certificate data, and aerial and field photographs, and allowed the CNN to learn them, a state called over-fitting was created, which made normal learning more difficult. However, as a result of countermeasures called data incrimination, we were able to obtain a estimation accuracy of approximately 63.6% in the aerial photographs and 73.6% in the field photographs. Since the decrease in the accuracy is due to building internal damages, we should also include the possibility of such damages that could not be assessed from the appearance alone, and of the images of damaged buildings from outside the target building; therefore, we investigated and verified the damaged buildings again based on the “images of damaged buildings evaluated by visual interpretation.” Then, it became clear that the damaged buildings can be identified with an accuracy of 86.0% in the aerial photographs and 83.0% in the field photographs. Furthermore, in the field photographs, it became clear that collapsed buildings can be distinguished with a high accuracy of 98.5%.

 From the above results, it was found that it is possible to assess the condition of damaged buildings by deep learning using field and aerial photographs taken in the affected area after the earthquake; however, the damage that can be identified with the highest accuracy is limited to the photographs of collapsed buildings. In our future research, we plan to correctly identify the difference between “moderate” and “slight” damaged buildings.

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