平島 岳夫

Three-dimensional elastoplastic finite element (FE) analysis models considering a damage zone and cleavage were developed, including plastic behavior of embedment tests parallel and perpendicular to the grain at ambient and high temperatures, in order to study the embedment behavior of timber. In a numerical analysis of compression tests to define material properties of timber, the post-yield behavior of the X-axis in the axial direction was larger than the test values when the post-yield slope of the test result were set to the plastic modulus. The reason was that the stress on the Y-axis and Z-axis increased after the yield point; thus, the equivalent yield stress decreased. In the numerical analysis of the embedment tests, the effect of the damage zone must be considered in the analytical models because the initial stiffness of the numerical results in compression parallel to the grain was considerably higher than that of the test results when the damage zone was not considered. In the numerical analysis of the embedment tests in compression perpendicular to the grain, the two models reproduced the stiffness and behavior after the yield point of the test results. The model that considered cleaving showed the stress distribution after cleavage.

Purpose This paper aims to investigate the fire performance of composite beams when considering the hogging moment resistance of the fin-plate beam-to-girder joints including the effect of continuity of reinforcements. Design/methodology/approach Experiments on composite beams with fin-plate joints protected only at the beam ends are conducted. The test parameter is the specification of reinforcement, which affects the rotational restraint of the beam ends. In addition, a simple method for predicting the failure time of the beam using an evaluation model based on the bending moment resistance of the beam considering the hogging moment resistance of the fin-plate joint and the reinforcement is also presented. Findings The test results indicate that the failure time of the beam is extended by the hogging moment resistance of the joints. This is particularly noticeable when using a reinforcing bar with a large plastic deformation capability. The predicted failure times based on the evaluation method corresponded well with the test results. Originality/value Recent studies have proposed large deformation analysis methods using FEM that can be used for fire-resistant design of beams including joints, but these cannot always be applicable in practice due to the cost and its complexity. Our method can consider the hogging moment resistance of the joint and the temperature distribution in the axial direction using a simple method without requirement of FEM.

<p> Regarding the load-bearing capacity of timber elements subjected to fire heating, knowledge of not only the charring behavior but also the mechanical properties at elevated temperature are required because the temperature of the non-charring area gradually increases during the cooling decay phases in fire. Therefore, in order to predict the fire resistance of timber elements, it is necessary to grasp the changes in strength and elastic modulus of the timber materials with temperature rise.</p><p> In this study, elevated temperature compression tests of structural glulam timbers made of Japanese cedar and larch were carried out for the purpose of understanding the influence of moisture in the timber on the compressive behavior at elevated temperature. The tests parameters were tree species, furnace temperature condition below 200 °C, and heating time. Influences of moisture in the specimens on the compressive behavior were discussed from the test results on the relationships of heating time and weight changing. Another purpose was to obtain a numerical model of stress- strain curves at elevated temperature to analysis the fire resistance of timber elements.</p><p> Main findings of this study were summarized as follows:</p><p> (1) Compressive strength at elevated temperature decreased significantly from the start of heating to 1 hour, and became the minimum during 1 to 2 hours. After that, the strength recovered with drying, and finally, it returned to the strength at ambient temperature.</p><p> (2) The reason why the compressive strength decreased significantly from the start of heating up to 1 hour was that the steam softening and the change of water content due to migration of the moisture had a great influence¹²⁾.</p><p> (3) Compressive strength of both Japanese cedar and larch decreased significantly when the internal temperature of the timber increased from ambient temperature to 70°C, and the lower values of the results up to around 100°C were close to the strength ratio of Eurocode5.</p><p> (4) The modulus of elasticity at elevated temperature decreased significantly from the start of heating to 1 hour, and became the minimum during 1 to 2 hours, similar to change of the compressive strength.</p><p> (5) Results of the load-displacement relationships indicated that the decrease of the rigidity and the maximum load in the initial stage of heating depended on the temperature rising rate.</p><p> (6) The stress-strain curve for compression within 1% strain was approximated by Richard's equation.</p>

コンクリート床板と鉄骨小梁による合成梁において，梁端のみに耐火被覆を施し，ボルト接合部の温度を一定程度以下に抑えて火災時における梁端回転拘束効果を保持できれば，小梁の耐火被覆を省略できる可能性がある。本研究では，梁端のみ被覆された合成梁の温度分布予測手法を検討するため，差分法による三次元熱伝導解析を行い，実験との比較検討を行った。床板仕様による上フランジ上面の熱的境界条件の違い，接合部における熱容量の増加および材軸方向の熱伝導を考慮した解析モデルによる計算結果は，実験結果とよい一致を示した。さらに，各部位における入熱量分析に基づき，各種の伝熱成分が各部位の温度に及ぼす影響を明らかにし，影響の大きい伝熱成分のみを考慮した一次元熱伝導モデルによる簡易計算手法を提案した。

本研究では，様々な水分条件を有するコンクリート試験体の重量減少測定実験を実施し，800°Cまでの温度上昇時におけるセメント水和物の水分損失について考察を行った。まず，気乾および封かん試験体では，100°Cを超えると水分の蒸発による重量減少が顕著になった。100°Cから200°Cにおける蒸発速度は，試験体の含水率に比例して増加した。また，C-S-Hのゲル水の脱水は500°C程度まで継続した。250～500°Cにおけるゲル水の脱水速度は，試験体のゲル水量に比例して増加した。そして，骨材の結晶水の影響を検討した結果，1.5°C/分の加熱条件では，600°Cから800°Cにおけるセメント水和物の分解に伴う水分放出は極めて少ないと考えられる。

<p> Timber elements have a problem in that the load bearing capacity decreases due to self-burning during cooling phase. In the case of timber columns exposed to fire, it is possible to fail with buckling because the cross-sectional secondary moment decrease considerably. Buckling failure of columns in fire may induce collapse of building, and it involve in the lives of fireman. However, there was a few load bearing fire test data to research the buckling behavior and failure time of the glued laminated timber columns exposed to fire heating for more than one hour. Therefore, method for predicting the failure time of structural glued laminated timber columns exposed to fire has not been established yet.</p><p> This paper reports on results of load-bearing fire test of structural glued laminated timber columns with Japanese cedar and larch during not only heating phase but also cooling phase. The purpose of the tests was to confirm the properties of charring, the temperature distribution in the cross-section, the deformation behavior and the failure time. Influences of tree type (Japanese cedar, Japanese larch), cross-sectional dimension (300 mm square, 450 mm square), heating time (30min, 60min, 90min), and load ratio (1, 2/3, 1/3: the permanent allowable design load) on the load bearing capacity in fire were discussed. The failure time from the test result was compared with that of the calculated result by the buckling strength on the basis of tangent modulus theory and mechanical properties at high temperature in accordance with Eurocode5. The follow conclusions could be indicated from this research.</p><p> </p><p> (1) Failure time of cedar columns was shorter than that of larch columns because the cross-sectional reduction of cedar columns during cooling phase were larger and the internal temperature in cross-section of cedar columns were higher.</p><p> (2) Under the same heating time and the load ratio conditions, the failure time of the 450mm square cross-section was 2 to 3 times longer than that of the 300 mm square cross-section.</p><p> (3) All specimens which exceeded a slenderness ratio at the time of failure by 51 resulted in buckling failure. The residual rate of cross-sectional secondary moment was considerably lower than that of cross-sectional area, so it was indicated that the columns were more likely to buckling in fire.</p><p> (4) It was indicated that the failure time which calculated by buckling strength using tangent modulus theory and mechanical characteristics in high temperature based on Eurocode 5 was equal to or a little shorter than that of the test result.</p>

<p> This paper presents results of high temperature compression tests of steel fiber reinforced concrete. The influence of steel fiber on the mechanical properties at high temperature was investigated from the difference of the test results between steel fiber reinforced concrete and plain concrete. Although research on prevention of concrete spalling by means of mixing steel fibers has been conducted, there is no report on mechanical properties of steel fiber reinforced concrete at high temperature in Japan, and there are few such reports in foreign countries.</p><p> In this study, high temperature compression tests were performed using two types of concrete, i. e. steel fiber reinforced concrete (SF) and plain concrete (P). The tests consisted two kind of tests. One was load increasing tests under steady state at constant high temperatures (steady state tests, ST tests). Other was temperature increasing tests under constant stress (transient tests, TR tests) . In case of ST tests, the parameter was specimen temperatures ranging from ambient temperature to 800 °C. While concrete was heated to the target temperature, heating rate was controlled at 1.5 °C/minute. While stress or strain of concrete increased, the concrete temperature was kept the target temperature. From ST test results, stress-strain relationship, compressive strength, Young's modulus and absorbed energy were compared between SF and P. In case of TR tests, the parameter was level of the constant compressive stress ranging from 0 to 0.7.After applying the target stress, specimen was heated and the relative displacement was measured. From TR test, the thermal strain and total strain were obtained.</p><p> Main findings of this paper were summarized as follows:</p><p> (1) Compressive strength ranging from 200 °C to 400 °C was higher for SF than for P, meanwhile both the compressive strengths were approximately same above 500 °C. There was no significant difference in Young's modulus at high temperatures due to the presence or absence of steel fibers.</p><p> (2) The absorbed energy of SF was larger than that of P between 100 °C and 500 °C, and the difference was the largest at 500 °C. On the other hand, the difference above 600 °C was relatively low.</p><p> (3) The thermal strain ranging from 600 °C to 800 °C was lower for SF than for P.</p><p> (4) Under stress level of 0.7 in TR tests, SF supported the load up to 477 °C, meanwhile P fractured at 78 °C. Under high load condition, the effect of steel fiber may be considerable.</p>

<p> In the case of steel-concrete composite beams pinned with steel girders, and the beam ends are rotationally restrained by the girders, reinforcing bars in the concrete slab work effectively so that the hogging moment resistance at the pin joints can be exerted considerably. Considering this effect, there is a possibility that fire protections of the steel beams can be omitted or reduced when the load level is low. However, the hogging moment resistance at pin joints considering rebars and the influence of the rebar specification on it have not been clarified.</p><p> This paper presents the results of load-bearing fire tests of composite beams protected only at the beam end with continuous floor slab conducted to clarify the hogging moment resistance at pin joints considering rebars and the influence of the rebar specification on it. 3 specimens (Pure steel beam, Composite beam using composite slab, Composite beam using RC slab) were tested, and the main test parameter was the specifications of the rebars in the concrete slab (the amount of main rebar, the type of rebar, the fixing method). The load level was 40% of the long-term allowable moment, and the heating was in accordance with ISO 834 standard curve. In this study, the hogging moment resistance of the joints and steel temperature of composite beam in fire were discussed.</p><p> The main conclusions from the test results were as follows:</p><p> 1) In the case of the cross section of the steel beam used in this tests, it was confirmed that the temperature of the joints during heating for 1 hour remained at about 600 ℃ by protecting at the joints using the fire resistive materials for 1 hour.</p><p> 2) The pin joints have sufficient rotational ability at elevated temperature without fracture of the bolts even in bending collapse.</p><p> 3) The pure steel beam with protected pin joints had the same ultimate strength as that of unprotected fixed end.</p><p> 4) In the case of composite beam using RC slab, the calculated value by the evaluation model of the hogging moment resistance at pin joints considering the rebars shown in Fig. 17(d) corresponded with the experimental values well.</p><p> 5) In the case of composite beam using composite slab, the rebars did not contribute to the hogging moment resistance at pin joints because the rebars were fractured at the initial stage of heating. It is necessary to evaluate the hogging moment resistance at the beam ends as simple steel beam without the effect of rebar when the rebars are fractured prematurely.</p>

<p> To investigate stress and deformation behavior of steel structure in fire, it is important to consider behavior of friction type high strength bolted joints during not only heating phase but also cooling phase. The purpose of this study is to clarify stress and deformation behavior of the joints during cooling phase in fire. Failure of the joints may occur due to tensile forces of the connected beam under cooling phase during decay period in fire. Furthermore, strength degradation of the high strength bolt steel which experienced high temperature cause the bolt in shear failure in fire. However, there was few research with the test which focused on the deformation behavior of the joint during cooling phase.</p><p> This paper reports on results of tensile tests of friction type high strength bolted joints during cooling phase and the numerical analysis on the basis of component based model. Post-fire-heating tensile tests were carried out in order to obtain the maximum strength of the joint after fire. This test was carried out on 6 specimens of the joint. The main test parameters were steel temperature and main plate thickness. Cooling-phase restraint tests, which simulated the development of tensile force during cooling phase, were carried out on 2 specimens of the joint. In addition, finite element analysis on the basis of component based model were carried out to discuss the behavior of the joint during cooling phase. The follow conclusions could be indicated from this research.</p><p> 1) Result of post-fire-heating tensile tests indicated that failure mode of the friction type high strength bolted joint could be changed from plate tear-out failure to bolt in shear failure. This is caused that strength of the bolt decrease considerably after fire heating. Maximum tensile resistance of the tests approximately agreed with the calculated result on the basis of the tensile tests of the employed steel plate and bolt.</p><p> 2) In case of the specimen which designed to investigate the behavior of plate tear-out failure, the sufficient deformation capacity was confirmed because of the ductility of the plates with a bolt hole. To prevent failure of the joint during cooling phase in fire, the tear-out failure of the steel plate is better than the bolt in shear failure.</p><p> 3) In case of the specimen which has much thickness of the main plate, the specimen failed with bolt in shear failure due to development of the tensile force at the joint during cooling phase. Damage of the bolt at high temperature affected maximum strength of the joint during cooling phase.</p><p> 4) The numerical analysis result of the joint with plate tear-out failure approximately agreed with the test result on increasement of the tensile force due to shrinkage of steel and restraint of axial displacement at both ends during cooling phase.</p><p> 5) Influence of shear deformation of the bolt at elevated temperature on the resistance of the joint during cooling phase was indicated by the numerical analysis results of the joint with bolt in shear failure.</p>

&nbsp;In the current fire safety design of steel structures in Japan, joints between steel beam ends and steel girders using friction type high strength bolts (this joint type is referred to as &ldquo;pin joint&rdquo;) are designed as pinned, therefore the fire resistance of the steel beams is determined only by the sagging moment resistance at the mid-span. On the other hand, research activities in Europe show that hogging moment resistance at pin joints of steel beams may be somewhat expected at elevated temperature. Moreover, in the case of steel - concrete composite beams, the reinforcing bars fixed in the concrete slab on the steel girders with headed studs work effectively so that the hogging moment resistance at the pin joints may be further improved. Furthermore, the sagging moment resistance at the mid-span is improved by the composite effect with concrete with small temperature rise. Considering these effects, there is a possibility that fire protections of the steel beams can be omitted or reduced.<br>&nbsp;This paper presents results of load-bearing fire tests of unprotected fully composite beams pinned with steel girders conducted for the purpose of clarifying the deflection behavior and the fire resistance. 3 specimens were used, and the main test parameters were end boundary conditions (simply supported, pinned with the girders) and joint specifications (number of bolts, fire protection of joints). (Simply supported beam and beam pinned with girders are referred to as &ldquo;simple-beam&rdquo; and &ldquo;pin-joint-beam&rdquo; respectively.) The load level was a third of the yield moment, and the heating was in accordance with ISO 834 standard curve.<br>&nbsp;The main conclusions from the test results were as follows:<br>&nbsp;1) The bending stiffness of the pin-joint-beams at ambient temperature was close to that of the simple-beam. On the other hand, the deflection was largely suppressed by the restraining effect against rotation at the pin joint at elevated temperature. This effect was exerted because the rebar worked effectively by tying the steel girder and the concrete slab with the headed stud. As a result, the time to reach ISO limiting deflection of the simple-beam No. 1 was 24 min, whereas that of the pin-joint-beam No. 2 and No. 3 were 61 min and 57.5 min respectively, the fire resistance was greatly improved.<br>&nbsp;2) Bending collapse was not observed for the pin-joint-beams. On the other hand, shear buckling of the web and local buckling of the lower flange occurred at the ends of the beam, but it is inferred that the load-bearing capacity was not lost immediately after the shear yield of the web.<br>&nbsp;3) No significant damage (such as bolt failure and plate tear-out failure) and no deformation (such as shear deformation of the bolt and bearing deformation of plate) at the pin joints were observed during heating and cooling process. On the other hand, immediately after stopping heating, as the ends of the concrete slab was damaged due to cooling shrinkage of the unprotected steel beam, the deflection sharply increased temporarily.<br>&nbsp;4) The full-plastic moment calculated using the strength obtained by the coupon test was able to accurately evaluate the sagging moment resistance for fully composite beam where the temperature of the lower flange reached 800 &deg;C.<br>&nbsp;5) The moment resistance of the pin-joint-beam was discussed by using the hogging moment resistance at pin joint considering the rebar inside the slab calculated by the equation (4). As a result, the effect on the total moment resistance was dominated by the sagging moment resistance at the mid-span at ambient temperature, whereas the influence of the hogging moment resistance at pin joint tended to increase at elevated temperature.

<sec> <title content-type="abstract-subheading">Purpose</title> This paper aims to discuss the fire performance of glulam timber beams based on their deflection behavior and load-bearing period, which were obtained from load-bearing fire tests under constant load conditions. </sec> <sec> <title content-type="abstract-subheading">Design/methodology/approach</title> In this report, the fire performance, primarily deflection behavior and load-bearing period of glued laminated (glulam) timber beams will be discussed from the standpoint of load-bearing fire tests conducted during the cooling phase under constant load conditions. Then, based on the charring depth and the per section temperature transformation obtained from loading test results, the load-bearing capacity of the glulam timber beams will be discussed using the effective section method and the strength reduction factor, which will be calculated in accordance with the European standards for the design of timber structures (Eurocode 5). </sec> <sec> <title content-type="abstract-subheading">Findings</title> In the cooling phase, the charring rate is decreases. However, as the temperature in the cross section rises, the deflection is increases. The failure mode was bending failure because of tensile failure of the lamina at the bottom of the beam. Moreover, a gap caused by shear failure in a growth ring in the beam cross-section in the vicinity of the centroid axis was observed. Shear failure was observed up until 1 to 3 h before end of heating. The calculated shear strength far exceeded the test results. Shear strength for elevated temperature of glued laminated timber is likely to decrease than the shear strength in Eurocode 5. </sec> <sec> <title content-type="abstract-subheading">Originality/value</title> Unlike other elements, a characteristic problem of timber elements is that their load-bearing capacity decreases as they are consumed in a fire, and their bearing capacities may continue to degrade even after the fuel in the room has been exhausted. Therefore, the structural fire performance of timber elements should be clarified during not only the heating phase but also the subsequent cooling phase. However, there are few reports on the load-bearing capacity of timber elements that take the cooling phase after a fire into consideration. </sec>

Purpose This paper aims to discuss the fire performance of glulam timber beams based on their deflection behavior and load-bearing period, which were obtained from load-bearing fire tests under constant load conditions.Design/methodology/approach In this report, the fire performance, primarily deflection behavior and load-bearing period of glued laminated (glulam) timber beams will be discussed from the standpoint of load-bearing fire tests conducted during the cooling phase under constant load conditions. Then, based on the charring depth and the per section temperature transformation obtained from loading test results, the load-bearing capacity of the glulam timber beams will be discussed using the effective section method and the strength reduction factor, which will be calculated in accordance with the European standards for the design of timber structures (Eurocode 5).Findings In the cooling phase, the charring rate is decreases. However, as the temperature in the cross section rises, the deflection is increases. The failure mode was bending failure because of tensile failure of the lamina at the bottom of the beam. Moreover, a gap caused by shear failure in a growth ring in the beam cross-section in the vicinity of the centroid axis was observed. Shear failure was observed up until 1 to 3 h before end of heating. The calculated shear strength far exceeded the test results. Shear strength for elevated temperature of glued laminated timber is likely to decrease than the shear strength in Eurocode 5.Originality/value Unlike other elements, a characteristic problem of timber elements is that their load-bearing capacity decreases as they are consumed in a fire, and their bearing capacities may continue to degrade even after the fuel in the room has been exhausted. Therefore, the structural fire performance of timber elements should be clarified during not only the heating phase but also the subsequent cooling phase. However, there are few reports on the load-bearing capacity of timber elements that take the cooling phase after a fire into consideration.

&nbsp;In case of fire, in addition to the stress due to permanent load, the thermal stress caused by the thermal expansion occurs in a steel frame. Therefore, if the deformation caused by the thermal stress at fire condition is concentrated at a connection, there is a possibility that the connection will be failed before the steel frame reaches its ultimate state. Considering such a phenomenon, in order to investigate the failure behavior of the steel structure connections exposed to fire in detail, it is necessary to analyze the stress and deformation of a heated steel frame in fire condition using thermal stress analysis. In the meantime, the analytical model that could represent the deformation behavior of the connection in fire is also necessary.<br>&nbsp;Due to the severe high-temperature strength reduction of high-strength bolts, there is a possibility that the friction type high strength bolted splice connection (bolted connection) might be the weakest point of the whole frame in fire condition. In Europe, for a model of the bolted connection using in the frame analysis, the component-based model have been proposed. This model is a model in which each connection component (beam, splice plate and bolt) was defined independently and its characteristics (stiffness and strength) were determined by means of nonlinear load deformation curves. The component-based model is possible to consider both the shear deformation behavior of high-strength bolt and bearing deformation behavior of the bolt hole.<br>&nbsp;This paper discusses a model of bolted connection on the basis of a component-based model. Connection type of a steel structure being used in Japan is different to that in Europe. And the component-based model of friction type bolted splice connection is less researched. Therefore, in order to investigate the deformation behavior of a bolted connection at elevated temperature, high temperature tensile experiments of two-sided friction bolted connections were performed. In this paper, firstly, component-based model outline is introduced. Afterwards, the analysis model based on the high temperature tensile test results of the bolted connection is derived, and is included to thermal stress analysis program. Finally, the suitability of this analytical model is shown by comparing the analysis results using this model with the previous experimental results.<br>&nbsp;The results of this study are shown below.<br>&nbsp;1) By conducting an analytical study of bearing deformation behavior of steel plate used in a bolted connection at elevated temperature, the curve fit coefficients &Omega; (reference to the previous studies) were modified as corresponding to the load-deformation relationship of friction type high strength bolted splice connection according to the results of steady temperature tests.<br>&nbsp;2) The numerical analysis results approximately agreed with deformation behaviors and critical temperatures of elevated temperature tests of the bolted connection under constant load. Also, this analysis method could predict the deformation of each component in bolted splice connection and the failure type of bolted splice connections approximately.<br>&nbsp;3) The numerical analysis results approximately agreed with the deflection behavior of both ends fixed steel beams with the bolted connection under constant load in fire condition. Moreover, this analytical method could approximate the damage level of each component (beam, splice plate and bolt) at the bolted connection.

&nbsp;When concrete is heated under a sustained load, a large amount of shrinkage occurs to compensate for thermal for expansion. This shrinkage was termed the load-induced thermal strain (LITS), and must be considered when performing a deformation analysis of reinforced concrete structures that are subjected to fire. In the constitutive strain models used in such analyses, the LITS is a function of the concrete temperature. However, the relationship between the LITS and temperature is influenced by the water of the concrete, making it difficult to apply these models to concrete with different water conditions. In the present study, the influence of the curing conditions (air-dried, oven-dried and sealed curing) and water/cement ratios (40%, 50% and 65%) on the LITS was investigated based on results obtained from the transient tests for measuring total thermal strain of concrete specimens. The relationship between the LITS and specimen weight loss was also evaluated in order to develop a comprehensive model for the LITS that is appreciable to concrete with different curing conditions and water/cement ratios.<br>&nbsp;In the transient tests for measuring total thermal strain, specimens ware heated at a constant rate of 1.5&deg;C/min. up to 800&deg;C under constant load. The ratio of the constant load to compressive strength of air-dried specimens at room temperature was settled between 0.1 and 0.7. The LITS was calculated by subtracting value of the free thermal strain from the total thermal strain. The heating rate in the transient tests for measuring the weight loss was same as the tests of the total thermal strain.<br>&nbsp;The main results obtained from the present study are as follows:<br>&nbsp;(1) The influence of the water evaporation on the LITS was evident between 100&deg;C and 200&deg;C.<br>&nbsp;(2) The influence of the dehydration and decomposition of the cement hydrate on the LITS was evident above 200&deg;C.<br>&nbsp;(3) The LITS due to dehydration and decomposition was larger than that due to water evaporation.<br>&nbsp;(4) The relationship between the LITS and load level was seen to be linear, regardless of the curing conditions or water/cement ratio.<br>&nbsp;(5) The numerical model for the LITS was proposed as a function of the weight loss of the specimens. And, it was indicated that the proposed model could be appreciable to concrete with different curing conditions and water/cement ratios.

&nbsp;Timber elements, which are different from other structural elements, have a characteristic problem in that the load bearing capacity decreases due to self-burning in the case of a fire, and this self-burning may continue after other fuel in the room has been exhausted. Therefore, the structural fire performance of timber elements should be clarified during not only the heating phase, but also the cooling phase. In the present paper, deflection behaviour and failure mode of larch glued laminated timber beams exposed to fire heating and natural cooling is discussed based on load-bearing fire tests in which load level is the test parameter.<br><br>&nbsp;The present paper described the fire performance, including the cooling phase, of structural glued laminated timber beams whose section was 210mm (width) x 420mm (height). The main conclusions were:<br><br>&nbsp;(1) Failure time was 79 minutes, for the long-term allowable load was loading. It was satisfied the Quasi-fire resistance of 1 hour.<br><br>&nbsp;(2) In the cooling phase, it may continue to support the load, when loaded below 0.4 times of long-term allowable load.<br><br>&nbsp;(3) On the other hand, in the cooling phase after 1 hour heating, it was confirmed that the deflection is increased. Compared with the deflection just after heating for 1 hour. LF-0.4 (1) in the cooling after 7 hours, deflection than during the just after 1 hour heating was about 6.7 times. LF-0.2 In the cooling After 24 hours, deflection than during the just after 1 hour heating was about 7.2 times.<br><br>&nbsp;(4) In the case of bending failure, strength of cooling 7 hours and 24 hours was about the same as the strength of the cooling 3 hours of previous report.<br><br>&nbsp;(5) The failure mode, bending failure and due to the laminar layer tensile breaking of the beam bottom, the shear failure due to the slip in the growth ring centroid axis near of the beam cross section was observed. Shear failure was seen in up to 1 to 3 hours from after heating.<br><br>&nbsp;(6) Bending strength in the cooling phase of the residual cross-sectional area, calculated value that gave the strength reduction rate due to Eurocode 5 is roughly agreement with the experimental value. On the other hand, the calculated value for the shear strength was significantly higher than the experimental values.<br><br>&nbsp;In the future, investigate the relationship between the strength of evaporation and the timber of water from the high-temperature material testing, it is expected to further consider the strength reduction in the cooling phase.

In the present study, the influence of the curing conditions and water cement ratios on the load induced thermal strain (LITS) was considered from the results of the transient tests for measuring the total thermal strain and weight loss of the specimens. The specimens (water/cement ratios were 40-65%) were cured with 3 methods. The results of the tests indicate that the LITS due to dehydration is much larger than that due to water evaporation. Moreover, the numerical model for the modeling of the LITS is proposed as a function of the weight loss of the specimens.

This paper reports on the behavior of structural glued laminated (glulam) timber beams under the constant load during and after fire conditions. Previous tests have indicated that the resistance of a beam exposed to standard fire for one hour declined by approximately 30% compared to that of a beam in ambient conditions. Additionally, it was reported that the strength of a beam exposed to heat in a furnace for one hour, followed by three hours of natural cooling, declined by approximately 14%. In this report, the fire performance of glulam timber beams is discussed based on their deflection behavior and load-bearing-period, which were obtained from load-bearing fire tests under constant load conditions.

The resistance of bolted splice connections is calculated on the basis of tensile strength obtained from high temperature tensile tests (coupon tests) of steel plates and bolt materials. The strengths of both steel plates and bolt materials over 500 degrees C are greatly affected by the strain rate applied in the high temperature coupon test. This paper investigates the effect of strain rate applied in high temperature coupon tests on the ultimate tensile strength of steel plates and bolt materials by comparing the test and analysis results of 20 cases. These strain rates eventually have a remarkable relation to the behaviour of the connections in elevated temperatures. Numerical analysis results on the basis of a component-based model using the strengths from high temperature coupon tests under high-strain-rate approximately agreed with the critical temperatures of bolted splice connections obtained from elevated temperature tests.

大断面集成材の火災時断面内温度に関するデータは近年増えている。しかし，加熱後放冷過程における耐力の低下および回復に着目して断面内温度を分析した報告は少ない。本研究では，火災加熱後放冷過程における木質構造梁の耐力低下を分析するための基礎データを得ることを目的として，1時間標準火災加熱を受けたカラマツ集成材梁の放冷過程における炭化性状および断面内温度を取得した。そして，加熱終了後の炉内空気供給量および載荷条件が放冷過程における炭化性状と断面内温度に及ぼす影響を考察した結果を報告する。

&nbsp;In this paper, the influences of the curing conditions and water cement ratios on the mechanical properties at high temperatures were considered from the results of the compressive tests. The water cement ratios of specimens were 65% ～ 40%. The specimens were cured with 3 methods: air-dried, oven-dried and sealed. The results obtained in this study are as follows:<br>&nbsp;(1) The influence of curing conditions on the compressive strength is clear at 100&deg;C.<br>&nbsp;(2) The strength of sealed specimens dropped sharply between 400&deg;C and 500&deg;C<br>&nbsp;(3) The influence of water cement ratio is clear between 400&deg;C and 600&deg;C.

Purpose: Based on heating tests and load-bearing fire tests, this paper aims to discuss the charring rate, the temperature distribution in the section and the load-bearing capacity of structural glued laminated timber beams not only during the heating phase during a1-h standard fire in accordance with ISO 834-1 but also during the cooling phase. Design/methodology/approach: Heating tests were carried out to confirm the charring rate and the temperature distribution in the cross-section of the beams. Loading tests under fire conditions were carried outto obtain the load-deformation behavior (i.e. the stiffness, maximum load and ductility) ofthe beam. Findings: The temperature at the centroid reached approximately 30°C after 1 h and then increased gradually until reaching 110-200°C after 4 h, during the cooling phase. The maximum load of the specimen exposed to a 1-h standard fire was reduced to approximately 30 per cent of that of the specimen at ambient temperature. The maximum load of the specimen exposed to a 1-h standard fire and 3 h of natural cooling in the furnace was reduced to approximately 14 per cent. In case of taking into consideration of the strength reduction at elevated temperature, the reduction ratio of the calculated bending resistance agreed with that of the test results during not only heating phase but also cooling phase. Originality/value: The results of this study state that it is possible to study on strength reduction in cooling phase for end of heating, timber structural which has not been clarified. It is believed that it is possible to appropriately evaluate the fire performance, including the cooling phase of the timber structural.