Colored concrete is concrete that is colored by adding pigment to the concrete mix. In recent years, such concrete has come into wide use for non-structural member like a curtain-wall and a slab. However, colored concrete technology has spread only for ordinary strength concrete. There are almost no studies regarding the application of a concrete with low water binder ratio like a high strength concrete.

 Colored concrete is originally defined as a mixture of cement, pigment, coarse aggregate, fine aggregate, and water. However, in the examination of surface color, it isn't always necessary to mix coarse aggregate in cementitious material. Thus, in this study, properties of colored mortar included low water binder ratio was investigated.

 In experiment, the compressive strength and color changes of mortar to which pigment was added were investigated. In all, four colors, namely pigment-free white, as well as pigmented blue, green, and yellow, were used. The dosage of pigment was that recommended by the manufacturer. The water-binder ratio of mortar was set to four levels: 0.2, 0.3, 0.4, and 0.5. Mixing was carried out in a room with temperature of 20±3℃. Using a Hobart type mixer, 4 liters of each batch were mixed. Once each type of mortar was mixed, a series of test values was measured to check flowability. After measurement, the mortar was poured in formwork measuring Φ50×100 mm for the compressive strength test and formwork of 145×105×15 mm for color measurement. Next, the specimens for the compressive strength test underwent sealed curing in a curing room at 20℃, and the specimens for color measurement were stored in a curing chamber at the temperature of 20℃ and humidity of 60%. As a result, the following were found:

 (1) Even for the colored mortar specimens with pigment added, high compressive strength of around 140 MPa could be obtained with the water-binder ratio of 0.2.

 (2) Regardless of the water-binder ratio, at the age of 1 day immediately after demolding, specimens of the same color all had about the same L*a*b* value.

 (3) Regarding the relationship between the measured L^*a^*b^* values, as time passed, the L^* value increased drastically between the ages of 1 day and 2 days. The color of colored mortar changes as the result of drying after demolding. And this tendency is pronounced the colored mortar with high water binder ratio.

 (4) It's possible to grasp the tendency of the (2) and (3) by RGB meter.

 Humans need to take various actions during and after earthquake. Prediction of human injury due to hitting to wall or falling due to shaking is considered to be important to develop strategies for prevention of human injury. Seismic analysis model of human body is useful to predict the human injury during an earthquake. In the previous study, we had developed the seismic response analysis model of human body based on shaking table test with human subject. The model was constructed by cart-type single inverted pendulum. The relative displacement between shaking table and the center of pressure (CoP) of human evaluated by the model agreed well with that of the human subject. However, the relative velocity between shaking table and head of human evaluated by the model was underestimated. This was because the model was constructed by single inverted pendulum.

 In this study, we constructed the seismic response analysis model of human body by cart-type double inverted pendulum model to overcome the problem of single inverted pendulum. Two types of model were considered; the double inverted pendulum without feedback control of hip (Type I), and that with feedback control of hip (Type II). Bending of the hip of the human subject during shaking table test is considered important to improve accuracy of the model. Type II could reproduce the bending posture, while Type I could not. Thus, the relative displacement and relative velocity of head of Type II agreed well with the motion of human subject during shaking table tests.

 Finally, the validity of the model was confirmed by the simulation analysis with other input motions. The maximum displacement of CoP and head and relative velocity of head could be well reproduced by using Type II model.

 Newly developed low-cost micro-electro-mechanical systems (MEMS)-based acceleration sensors exhibit enough accuracy and stability to monitor the shaking of structures caused by an earthquake and analyze damage to a facility after a powerful earthquake event. We have developed a practical shaking monitoring system using the MEMS-based acceleration sensors and a 920-MHz multi-hop radio communication method that can offer reliable radio wave communication even in large-scale facilities. An acceleration sensor unit must be installed on each floor of a building to accurately evaluate earthquake damage to an entire structure. In this kind of system, the base clock of each sensor unit must be highly synchronized to the master clock to minimize the acceleration-induced phase synchronization error. In the proposed system, such error among multiple sensor units can be limited to three milliseconds based on our patent-pending technology.

 In this paper, time synchronization, measurement accuracy, and communication performance for the newly developed acceleration measurement system were studied, and the following important conclusions were obtained.

 1) In actual buildings, communication between sensors can be performed without being affected by a concrete slab with a thickness of upto approximately 640 mm when using a long distance communication antenna and about 520 mm when using a film antenna.

 2) Due to the time synchronization error among the sensors being within ±3 ms, the accuracy of time synchronization could be sufficiently secured for application to structural health monitoring.

 3) Regarding the acceleration measurement accuracy of each sensor, the measurement error was only 2.9% at the maximum compared with a commercially available acceleration sensor, and the system displayed a measurement accuracy that can be applied to structural health monitoring.

 4) As a result of conducting the demonstration test of the acceleration measurement system in a real building, it was confirmed that stable data measurement was possible.

 Based on the above findings, the wireless acceleration measurement system developed can be used for buildings of various structural types such as reinforced concrete buildings, steel buildings, and high-rise buildings because inter-floor communication is possible.

 In the design of joints and peripheral members of shear panel dampers, sectional design corresponding to the increase in the strength of the shear panel is required. Therefore, if a shear panel damper with a small increase in proof stress can be achieved, the reasonable design of the joint and peripheral member can be done.

 In this study, the feasibility of the load-displacement relationship control of the shear panel was analytically examined by adjusting the web imperfection shape. First, a method for searching a web imperfection shape to reproduce a target load displacement relationship was proposed. The method searches for a web imperfection shape using example problems.

 The findings of this study are as follows:

 (1) A method for searching a web imperfection shape to reproduce a target load displacement relationship was proposed. In this method, the web imperfection shape was expressed as convolution of some mode shapes. Subsequently, each mode coefficient was changed using the modal iterative error correction method to fit the target load displacement relationship.

 (2) The proposed method was applied to the sample problems to verify the feasibility of the load-displacement relationship control of the shear panel by adjusting the web imperfection shape. The results indicate that the web imperfection shape that matched the target load displacement relationship could be searched by the proposed method. In addition, the sensitivity to the variation of the amount of web imperfection was also examined. It was confirmed that the load displacement relationship of the shear panel damper can be controlled by the web imperfection shape.

 (3) The present examination is limited to the analytical examination, and the feasibility of the production of the actual member has not been examined. A future study should verify if the actual member of the shear panel damper with web imperfection shape, searched by the proposed method, shows the target load displacement relationship.

 TMD (Tuned Mass Damper) has the advantage that the damping effect can be obtained by the mass of 1 to 3% of structure. In addition, TMD is fit for the vibration control of spatial structures because it is possible to install TMD by a single supporting point. Therefore, there are many studies on spatial structures with TMDs. In almost these studies, installing direction of TMDs is downward in order to control the vertical responses subjected to input wave. It is expected that the response reduction effect will be affected by the vibration direction of TMD. However, there is no study that the installing direction of TMDs with higher response reduction effects is examined. From these backgrounds, the purpose of this study is investigation of seismic response control effects by plural TMDs which have various installing direction for cylindrical lattice shell roofs with various magnifications of out-of-plane stiffness of roof. In addition, the robustness of response reduction effects for deviation of installing angles of TMDs and the relationships between the natural period ratio R_T and the installing direction of TMDs with the highest response reduction effect will be investigated.

 The object structures are the cylindrical lattice shell roofs with supporting substructure with the size of gymnasium. The magnifications of out-of-plane stiffness of roof are varied to 10, 50 and 100 times based on the shell roof with proportioned sections by allowable stress design for temporary loading with safety factor of members ν=2.5 under dead load. The treated types of TMD are Double TMD and Quadruple TMD. Frequency ratios and damping ratios of TMDs are calculated by using the equations for optimum condition. The installing directions of TMDs are vertical, horizontal, normal, tangential and mode directions. The mode direction is the direction determined by eigen vectors at the positions for installing the TMDs. The methods of analyses are a natural vibration analysis, a modal analysis and a time history response analysis which takes the geometric nonlinearity into account.

 From the numerical results, it is concluded as follows.

 1) The response reduction effects are the highest when installing directions of TMDs are determined by the ratios of the horizontal x direction component and the vertical z direction component of the eigen vectors at installation points of controlled modes (the mode direction), regardless of the half open angle and magnifications of out-of-plane stiffness of roof.

 2) In the case of TMDs installed in a direction other than the mode direction, the direction with higher response reduction effects varies according to the natural period ratio R_T. When the natural period ratio R_T is smaller than 1.0 or 1.3, the direction with higher response reduction effects is normal direction. On the other hand, when the R_T is larger than 1.0 or 1.3, the direction is the horizontal direction.

 3) If the average of angular deviation from installing angles of the mode direction, which is the vibration direction with maximum response reduction effect, Σ_K^θ is within about 15 degrees, there is no influence on the response reduction effect.

 4) Regardless of half open angle, the installing angles of the mode direction are in a linear relationship with R_T. That angle differs depending on shape of the controlled vibration mode. And if the installing point and substructure move in the same direction, that angle can be obtained by the defined equation (26), if the installing point and substructure move in the opposite direction, that angle can be obtained by the defined equation (27).

 A braced shear wall is an important shear resistant element in post and beam construction in Japan. Braced shear walls have better work-ability than nailed plywood shear walls and easier to install ventilation holes and piping holes. Also, it has advantages such as high wall magnification can be obtained by using in combination with plywood, it is widely used in wooden houses.

 Though many studies have been done on the static structural performance of braced shear walls, it was difficult to predict the load- story displacement relationship of the braced shear wall on tensile direction. In this study, focused on the braced shear wall using L-shaped brace connectors that connect the ends of a brace and columns, which have become popular in recent years, static shear loading tests of the single-braced shear wall specimens were conducted. Variables of the specimens were the wall length, the thickness of the L-shaped brace connector, the number and the length of screws.

 Then, an analysis model of the braced shear wall with the L-shaped brace connectors was proposed and static pushover analyses were conducted. The analysis result showed close to the load-displacement relationship of the experiment up to about 1/50 rad.

 From the static shear loading tests and the pushover analyses, following findings were obtained.

 a) As the thickness of the L-shaped brace connector increases, the shear strength of the braced shear wall increases and the ultimate displacement decreases.

 b) Effect of the number of the screws on the column on the shear strength of the braced shear wall is small in the case of 910mm of wall length. However, in the case of 1365mm and 1820mm of wall length, since a ratio of the horizontal component of the axial tensile force of the brace to the vertical component of the one increases, it affects the shear strength.

 c) With long screws on the column, the maximum shear strength of the braced shear wall increases. However, there is possibilities of pulling-through the screw from the connector or splitting failure of the column. Therefore, the higher pull-out strength of the long screw may not affect the maximum strength.

 d) Even if the number of screws on the brace side increases, the influence on the shear strength of the braced shear wall is small due to cracks on the end of the brace. If the cracks on the brace do not occur, the maximum shear strength of the braced shear wall is considered to increase.

 The use of timber for public buildings is being promoted in Japan. Various efforts were made to realize medium and large scale wooden buildings from these background. However, in timber structure, the analytical environment has not been established yet compared to other structural material. This paper focuses on the friction characteristics between wood and steel, which is used to boundary condition of joints where stress is not uniform. According to the theory of adhesion, friction between wood and steel can be deal with sum of adhesion force, which is shear force in proportion to contact area between steel and wood, and the effect digging up the wood surface by steel. In this study, friction tests and measurement of wood surface were carried out, and investigating these correspondence based on theory of adhesion. The friction tests were conducted in the wide range of 0.5 to 11 MPa for previous research. Wood surface were measured three stages after compressive load and after friction tests. The main findings are as follows.

 ・When the pressure of contacted surface was higher than 1 MPa, the deformation of wood was confirmed. The influence was observed that two peaks were shown in time history of friction coefficient. In this study, the coefficient of static friction was evaluated from the second peak time by the reason why the time shows only sliding movement.

 ・The coefficient of static friction of the wood surface is about 0.3 to 0.4 on average, but the variation due to the test piece is large, and it is about 0.07 for sliding T direction and 0.1 for sliding R direction against the average.

 ・Without the lowest pressure of contacted surface of 0.55 MPa, the coefficient of static friction increased with repeated friction, which can be explained from the waviness component of wood surface.

 ・When the pressure of contacted surface is 2.2 MPa, the highest coefficient of static friction is obtained by conducted tests. The area where the pressure of contacted surface is lower than this can be explained only by the adhesion force. On the other hands, the factor that the coefficient of static friction decreases when the pressure of contacted surface is higher than 2.2 MPa is estimated by the effect of digging up. Since the deformation within the range of 1 mm from contact surface is allowed in this research, we plan to continue investigation in order to verify the inference in future.

 Conventional test program for timber shear walls in Japan uses a loading protocol consisting of monotonic loading following reverse cyclic loading up to 1/50rad. While repeated cyclic loading is thought to decrease force and deformation capacity due to the fatigue behavior, specimens based on the conventional test program might not sustain enough cycles at large deformation range. Although timber shear walls had better have large deformation capacity, it is not always empirically confirmed. Recently, buildings are required to protect not only the safety but the property after a major earthquake, and passive control techniques for timber structures have been developed in order to enhance the seismic performance. Therefore, evaluation of timber shear walls' fatigue behavior have become an important issue.

 Several experiment-based studies on timber shear walls' fatigue behavior can be found, and some of them have proposed hysteresis model for time history analysis. However, time history analysis are rarely used for seismic design of timber detached houses owing to time and effort. Response spectrum method, which is approximated calculation method for maximum earthquake response, is alternate seismic design rule in order to specify the performance. In response spectrum method, characteristic of building is determined by two parameters: equivalent stiffness and equivalent damping ratio. Fatigue behavior should be taken into account as deterioration of the two parameters.

 In this study, the final goal is to develop a response spectrum method considering fatigue behavior of timber shear walls. Part 1 deals with evaluation of strength and energy dissipation of two typical timber shear walls subjected to various deformation history. Chapter 2 introduces static loading tests. Various loading protocol were applied. Chapter 3 introduces shaking table tests. Two types of earthquake motions having same spectrum shape and different duration time were applied. Chapter 4 introduces evaluation formulae for strength and equivalent damping ratio. The followings are findings of this research.

 1) Envelope curve of force-deformation angle relation has dependency on loading protocol. The envelope curve in monotonic loading is the upper limit, and the others go down as the number of cycles becomes large.

 2) Plywood type shear walls are vulnerable to repeated loading rather than brace type shear walls, which is likely to be related to the failure mode. As for plywood type shear walls, when the number of cycles was small like monotonic loading, failure mode of nail joint was punching out. However, when the number of cycles was large, nail joint was fractured by bending.

 3) When two earthquakes having the same response spectrum shape and different duration time were repeatedly applied, the one having longer duration time rapidly brought deformation increase. It is likely to be related to fatigue behavior owing to repeated loading similar to the above finding 1).

 4) Both brace type and plywood type specimens kept seismic performance against repeated earthquake motions if the maximum deformation response was less than one third of the ultimate deformation.

 5) Evaluation formulae for strength and equivalent damping ratio considering fatigue behavior were proposed. The formula for strength has a unique parameter controlling damage effect when the deformation amplitude is expanded. The formula for equivalent damping ratio is empirically derived based on the fact that equivalent damping ratio has strong dependency on the already experienced maximum deformation rather than the number of cycles. They showed acceptable agreement with results of static random loading tests and shaking table tests.

 Wooden roof frame is required to have angle braces and intertruss bracings based on the current specification code. In the past natural disasters except for strong wind by typhoons, wooden roof frames have rarely suffered severe damages. The current code has been thought to work well. However, traditional-type wooden roof frame does not satisfy the current code. In addition, the roof frame is boarding diaphragm consisting of narrow boards fastened by nails, which is thought to have low shear stiffness and strength unlike plywood sheathing floor diaphragm.

 A roof frame works as horizontal diaphragm transmitting lateral force to shear walls. In the current allowable stress design, stress distribution of a floor diaphragm is calculated using continuous shear beam. The allowable strength is determined by referring to test results of elements such as roof frame covered by wooden boards and beam frame with angle braces. Since the design method is originally applied to modern wooden roof frame, the applicability to traditional-type wooden roof frame should be investigated.

 In this paper, shear performance of gable roof, which is one of the typical roof systems, subjected to lateral force in the longitudinal direction is discussed. Although previous studies often consider pure shear condition, equally distributed forces with two specific boundary conditions are applied to roof frame in order to simulate earthquake force or wind force. Following the full-scale experiment, the behavior is simulated by two-dimensional framing analysis model whose characteristics is determined by referring to results of element tests. Parameter study with various specifications of each element is also conducted, and the effect of the stiffness balance on the shear behavior of roof frame is investigated. Finally, the framing model is converted to simplified model which is capable of expressing mathematical relation of each parameter.

 The followings are findings of this research.

 1) In cantilevered roof frame, shear force-deformation angle relations of roof frame and beam frame could be simply added.

 2) In roof frame specimen, shear force was sustained by roof frame while moment was sustained by beam frame. It is likely to be assured by rotational resistance of transverse walls.

 3) Average shear stress along the span controls the behavior of roof frame, and it is reasonable to suppose that the average shear stress should be checked in each half span divided by ridge beam. Actually, flexural resistance of beam frame had an effect of making shear deformation in the roof frame more equal. However, it is difficult to be assured when connections exist in the tie beams.

 4) Two-dimensional framing analysis model was constructed based on results of element tests, and it gave close agreement with test results.

 5) Parameter studies of framing analyses showed that replacement of nuki with brace in vertical frame had little effect on performance of roof frame due to relatively large contribution of moment resistance by tenon connections.

 6) Simplified model derived from framing model could give mathematical relation of each parameter. It can provide simple formulae of whole behavior with less effort.

 Although the effect of in-plane shear stiffness on dynamic behavior of a building is not mentioned in this paper, the above 3) insists that 2-span dynamic model, which has been proposed by the authors^14)-16), can be utilized. It will be discussed in the future.

 1. Introduction

 In recent earthquakes in Japan, significant damage to RC secondary flat walls (with rectangular cross sections), which have been regarded as non-structural walls, was repeatedly observed. The previous study⁵⁾ clarified that shear failure of flat walls can cause drift concentration in RC buildings and decrease the ultimate deformability. However, advanced numerical analyses were needed to evaluate such comprehensive behavior including the shear failure of flat walls affected by passive compression under seismic loads. Therefore, the present study investigates practical methods to evaluate the passive compression on the flat walls.

 2. Analytical models

 This study designed several idealized models which consisted of beams and flat walls representing typical RC residential buildings in Japan which had 1, 3, 6, 12, and 18 stories. The flat walls were designed referring to common construction in Reference 3), while structural members were designed according to Japanese practice⁶⁾. Figure 2 illustrates the idealized models for the following analyses.

 3. Numerical methods

 The beams were modeled by line elements, which had a roller support at the outer edge and an elastic or inelastic bending spring at the inner end (Fig. 2). The flat walls were modeled using IPE model³⁾ (Fig. 3), which could well simulate the strength deterioration. Such numerical methods applied to the following analyses were justified through simulation of the authors’ preceded test (Fig. 8).

 4 and 5. Results from numerical analyses and estimation on axial compression of the flat walls

 Pushover analyses were conducted for the analytical models. High axial compression of approximately 0.4 times as the compressive strength of the flat walls was found to act on those in the first story (Figs. 10 and 14). The mechanism of such high compression passively applied to the flat walls was illustrated based on their non-linear axial elongation (Fig. 11). The upper bound of axial compression was estimated by Eq. (11) based on a simple theoretical model (Fig. 12b), which well agreed with the numerical results for high-rise models with 12 and 18 stories. In addition, the other theoretical estimation of the axial compression using iterative cross-sectional analyses (Fig. 15) was presented, which modified the estimations by Eq. (11) for lower models.

 6. Conclusions

 The present paper investigated axial compression passively applied to RC flat walls in moment-resisting frame structures under seismic loads. Numerical analyses clarified that the passive compression on the flat walls attained to approximately 0.4 times as the compressive strength and had an upper bound. A theoretical equation representing an ultimate state of the cross section could estimate the upper bound particularly for high-rise models. The other theoretical estimation procedure considering iterative bending analyses was also presented and more precisely estimated the axial compression on the flat walls for lower models.

 Generally, steel frameworks are designed based on a beam-collapse principal that ensures a beam-to-column strength ratio that in the event of an earthquake distributes damage to each floor. Beams are important earthquake resistant members that dominate the seismic response of the entire structure. It is therefore important to clarify the performance of steel beams that are subjected to the seismic forces associated with repeated loads.

 We previously proposed hysteretic models to express the response to cyclic lateral torsional buckling of H-shaped beams with a large slenderness ratio λ_b.^1),2) In addition, we proposed a monotonic loading history model under a uniform bending moment (κ = -1.0) and a one-end bending moment (κ = 0.0) for beams with a small slenderness ratio, again under lateral torsional buckling.³⁾ However, to date, no monotonic loading history models has been developed for H-shaped beams subjected to an antisymmetric bending moment (κ = 1.0), or an associated cyclic loading hysteretic model.

 Therefore, the purpose of this study was to develop hysteretic models for H-shaped beams with a small slenderness ratio under cyclic loading for lateral torsional buckling that take into account coupling between local and lateral buckling. This buckling process is investigated using the finite element method (FEM). Based on the analytical results, hysteretic models for a H-shaped steel beam with a small slenderness ratio for lateral torsional buckling were formulated. These models consider the width-to-thickness ratio, the slenderness ratio, the stationary limit amplitude, the unloading stiffness, and the stiffness change point.

 The conclusions obtained in this study are as follows:

 1) Equations (19) and (20) were proposed as hysteretic models under monotonic loading based on the analysis results for H-shaped steel beams subjected to antisymmetric bending.

 2) Based on the above model and the results of a previous study,³⁾ a hysteretic model under cyclic loading composition rule is shown in Fig. 22.

 3) The applicable range for the hysteretic model under cyclic loading was found to be approximately 0.6≤ λ_b ≤0.7 (κ = -1.0), 0.4≤ λ_b ≤0.7 (κ = 0.0), 0.5≤ λ_b ≤0.9 (κ = 1.0).

 The advantages of concrete-filled steel-tube (CFT) columns include high strength and remarkable ductility, since the steel tube provides confinement to the concrete while the concrete prevents local buckling of the steel tube. CFT column composite frame systems with steel beams have been widely used in moment-resisting frame systems for mainly office buildings. CFT columns at typical floors are short and have small ratios of buckling length to cross section depth, and those at entrances of lower floors are slender and have large ratios of buckling length to cross section depth. CFT columns from short to slender have been used in buildings. In order to verify the structural safety of CFT structures in the ultimate state against huge earthquakes, etc., a restoring force characteristic model incorporating strength reduction after ultimate strength is required. The stress states of CFT columns applied to buildings are in a state of flexural-shear stress, and the structures are designed for the predominant flexural yielding. It is thought that accurate evaluation of a shearing force-deformation relationship under axial force will lead to design of columns that have the features of CFT columns. For a restoring force characteristic model, which is the basis of the shearing force-rotation angle relationship of CFT columns from short to slender, it is important to devise a simple model incorporating a reduction of strength after ultimate strength. This paper proposes a new simplified restoring force characteristic model of a shearing force-rotation angle relationship for square CFT beam-columns to estimate the elasto-plastic flexural-shear behavior of beam-columns from short to slender. The square CFT beam-column model incorporates a reduction in strength after ultimate strength.

 The proposed simplified model is a multi-linear model having a crack strength point, a yield strength point, an ultimate strength point and strength reduction points. In the proposed model, each flexural strength is calculated by a general superposed strength method, and new multiple regression formulas for each rotation angle are proposed based on results of monotonic and cyclic loading tests from previous researches. Predictions from the proposed model of the shearing force-rotation angle are found to agree approximately with experimental results up to large rotation angles.

 Fire damage determination of buildings in Japan is often carried out based on the "Recommendation for diagnosis and repair method of fire-damaged buildings" edited by the Architectural Institute of Japan. According to the guideline, when a reinforced concrete member is subjected to fire, the fire test is carried out by performing a compression test using concrete cores sampled from the fire damaged part and the non-damaged part respectively, then comparing the compressive strength results of the two. Although the fire damage grade of the concrete of the department has been decided, currently there are not many methods to estimate the damage depth.

 Concrete exposed to fire is cracked when the heated surface is exposed to high temperature. It is known that the cracks grow as the temperature rises from the shrinkage of cement paste and the expansion behavior of aggregate, and propagate inside concrete.

 Damage caused by cracking of concrete after heating and cooling is the most severe on the heated surface side, and the less on the inside. When a core taken from the heated surface of the concrete is subjected to a compressive strength test, it is considered that the breakage occurs from the heated surface side and does not reach the inner side of the core.

 However, due to the mechanism of the compression tester, the core under pressure is restrained at both ends by the end face friction of the pressure plate, and exhibits uniform failure over the entire core, including the damaged portion.

 In this basic study, focusing on the compressive strength test of the core sampled from the fire-damaged concrete, the compressive strength test is carried out with the end face friction between the pressure plate and the core end reduced, and we tested whether the damage depth could be estimated.

 As a result, the following conclusions were reached.

 ・ The fracture pattern of the compressive splitting type is obtained by reducing the friction between the pressure plate of the tester and the upper and lower ends of the core during the compressive strength test of the core, and it gradually deforms inwardly from the upper end of the core (heated surface side) It was confirmed that the singularity was reached.

 ・ In the compressive strength test with reduced friction between the pressure plate of the tester and the upper and lower ends of the core, the damage depth of the fire damage zone can be estimated from the deformation singular point and critical stress degree of each depth in the core axial direction .