平島 岳夫

 In the fire safety design of steel structures, failure of friction type high strength bolted joints is concerned. This paper discusses maximum tensile resistance of friction type high strength bolted joints exposed to fire on the basis of two tensile tests (steady state tests and transient state tests) of the joint. High temperature transient state tests under constant load and increase temperature were conducted in order to investigate the influence of displacement rate on their maximum strength. In case of the transient state tests, the specimen was subjected to the load which was maximum load from the steady state test or from calculation result based on AIJ Recommendation. Load bearing capacity of the joints has been kept over expected critical temperature in case of the transient state tests.

 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. However, in examining the load bearing capacity of timber elements in a fire, few studies have considered the cooling phase. In the present paper, the fire performance of glued, laminated timber beams is discussed based on load-bearing fire tests that take the cooling phase into consideration.

In order to analyze the redundancy of steel frames in fire, it is important that the load-deformation behaviour of friction type high strength bolted joints at elevated temperature is clarified. In this paper, influences of plate thickness, end distance, fastening of bolts and steel temperature on the deformation behaviour of the bolted joints are discussed on the basis of the elevated temperature tensile test results. In case the plate is thin and the failure mode is tear-out, the ductility of the joints increases. However, if the failure mode is changed from tear-out to bolt in share due to increase of temperature or end distance, the ductility of the joints decreases. Fastening of bolts slightly affect the load-deformation behaviour of the bolted joints at elevated temperature.

This paper discusses, on the basis of experimental results, structural fire behaviour of a rigid steel frame with fully-moment-resisting beam-to-beam connections with splice plates and high strength bolts, and beam-to-column connections with full penetration welds. The test results indicated that the moment-resisting connections in the rigid steel frame have sufficient load-carrying capacity, but failure may occur in the connected beam due to inadequate shear resistance of the beam web in fire. The critical temperature of the steel beam could be approximated on the basis of its inherent resistance at elevated temperature and initial effects, because the thermal stress disappeared at the fire limit stage. In this study, the safety factor of structural fire safety design was also discussed on the basis of the result of these load-bearing fire tests.

Mixed structures composed of R/C (Reinforced Concrete) columns and steel beams can accommodate larger building spaces, whereas the R/C columns may be subjected to severe thermal stresses due to the thermal elongation of long span steel beams in a fire. In previous paper, results of load-bearing fire tests of sub-frames of the mixed structure indicated that the fire resistance of R/C columns is reduced by covered concrete spalling and forced horizontal displacement at the top of the columns due to thermal elongation of steel beam. In this paper, results of thermal stress analysis of these tests are presented and the influence of the concrete spalling and the action from the beam on the fire resistance of R/C columns is discussed.

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

Mixed structures composed of reinforced concrete columns and steel beams can realize larger building spaces, whereas reinforced concrete columns are subjected to thermal stresses due to thermal elongation of long span steel beams in case of fire. It is very important to clarify the load carrying capacity of the complicated beam-column connections in fire. This paper presents the results of the sub-frame fire tests of a mixed structure composed of up-and-down RC column, steel beam and the connection. The test results indicate the non-fire-protected connection covered with thin steel plate has load carrying capacity during 3 hours of standard fire temperature curve. In this paper, fire performance of the beam-column connections is discussed.

In order to investigate shear and bending behavior of prestressed precast concrete (PCaPC) beams with high-strength rebars and multiple large openings, three specimens for PCaPC beams were tested. Test parameters are the level of vertical loading and the quantity of shear reinforcement. It was confirmed from the test results that PCaPC beams are able to resist the allowable permanent during 3 hours standard fire. The evaluation method for bending and shear strength of PCaPC beams at high temperature, as well as the results of the fire experiment will be presented. In this analytical method of shear strength, the truss mechanism across openings in addition to at opening and between openings was considered. This new shear strength mechanism is proposed to calculate with a good accuracy taking into account of the temperature of longitudinal and shear rebars.

This study narrows the application temperature field of aluminum alloy to 350 °C or less, and examines the strength of web-bolted moment joints within that temperature range. Bending strength of web-bolted moment joints of aluminum alloy exposed to fire is investigated experimentally and analytically. It is observed that if splice plate length and the beam section are designed appropriately, it is possible that maximum bending strength is fully realized with the web-bolted moment joints. The transmission mechanism of the bending moments is thought to be based on prying action between the flanges and splice plate side edge. The effect of prying action contributes to the maximum bending strength. Maximum bending strength ratio is 90-60 %. © 2011 INTERNATIONAL ASSOCIATION FOR FIRE SAFETY SCIENCE.

Precast prestressed concrete (PCaPC) beams with high-strength rebars and multiple large openings have tremendous potential in architectural applications. They are high in quality, and can realize larger building spaces providing smaller and lighterbeams. In Japan, under the current Building Standard Law of Japan aside from conventional prescription-based fire safety regulations, it is now possible for designers to test and to apply new materials and new members on projects if their fire resistance performances are confirmed by tests. Their performances can be evaluated based on fuel loads and fire scenarios calculated room by room. In this regard, the fire test for new pre-stressed precast beams was conducted by the authors for extracting their performances. This paper is intended to provide a summary of the findings obtained from the fire experiment. Three specimens for precast prestressed beams were tested. Test parameters are the level of vertical loading and the quantity of shear reinforcement. All specimens are made of high strength concrete mixed with organic fibers for the prevention of explosive spalling. It was confirmed from the results that PCaPC beams are able to resist the allowable permanent during 3 hours standard fire. In the paper, evaluation method for bending and shear strength of PCaPC beams at high temperature, as well as the results of the fire experiment will be presented. The analytical results showed that the truss analogy model underestimates the shear strength of the beam at opening. It was clarified that not only truss model but also the arch analogy should be considered for evaluating the shear strength of the beam.

Fire resistance of structures depends on the structural stability during a fire.<br>If a fire occurs in a building after an earthquake, structural members would lose their stability earlier than the nominal fire resistance time because the fire protection would be damaged by the earthquake. This paper shows the deformation behavior of the fire protections which comprise covering with sprayed rock wool, calcium silicate board, heat-resisting rock wool blanket, and heat-resistance coating sheet in shaking table tests on a full-scale steel structure. As a result of the tests, the fire protections were little damaged about efficiency of fire resistive performance.

The effects of high temperature on the mechanical properties of 100N/mm² high strength concrete have been studied experimentally at various temperatures ranging from room temperature to 700&deg;C. Test results indicated that transient strain accounts for a big rate to total strain, and the effect of transient strain of high strength concrete is bigger than that of moderate strength concrete. We tried to formulate transient strain on the basis of Anderberg's model and obtained transient strain coefficient k₂=5.56. Displacement constraint condition tests at elevated temperature were carried out and the constitutive model of high strength concrete was verified by thermal stress analysis. The results indicated that taking into account transient strain improved the analytical estimation of the variation in thermal stress of high strength concrete exposed to fire.

This paper presents a experimental study on the structural behavior of H-shaped steel beams with high strength bolted joints in case of fire. Load bearing fire tests were carried out under rotational restraint conditions at the both ends of the beam in order to investigate the temperature distribution of steel beams, the rotational performance of the friction type high strength bolted joints at high temperature, and the relation of critical temperature of steel beams with joints to permanent loads. Their critical temperatures of steel beams with joints are approximated by applying the strength of joints to the simple plastic theory because the rotational capacity of beam joints is remarkably improved at elevated temperature.

This study indicates the influence of the prying action on Web bolted moment joints of aluminum alloy beams and splice plates. In this joints, the gap can be rather narrow between the beam flange and the splice plate side edge because of aluminum extrusion. Web bolted moment joint can transmit the bending moment by bearing of the bolts and the prying action between the beam flange and the splice plate side edge. The bending moment of prying action is neglected usually. In this paper, it is clarified experimentally and analytically that the bending strength ratio of prying action reaches to 60%-90% for the maximum bending strength. After each experiment, the phenomenon of tensile or punching shear fracture has been observed at web or flange portion of beam in a specimen.

Bending tests of friction type high strength bolted joints at elevated temperature are conducted in order to obtain the relationship between bending moment and rotational angle of joints. Steel beam joints fastened by high strength bolts have rotational capacity under elevated temperature, because high strength bolts do not fracture at temperature above 500&deg;C while shear deformation of bolts are less than the diameter of bolts. Bending deflection behavior of steel beam joints is approximated by the relationship between shear force and shear deformation about high strength bolts.

By using tempered glass as a quake-resistant wall, a loading test was conducted with respect to a tempered glass wall that receives horizontal force and the following findings were obtained: 1. Tempered glass wall that is larger than a size of width 1800 mm x height 1800 mm x thickness 10 mm can support a horizontal load exceeding 100 kN. The maximum horizontal load was 196.7 kN when the thickness of the tempered glass was 12 mm. 2. The load bearing capacity of the tempered glass wall is determined by the buckling of the glass in the case where only the corners are restrained. On the other hand, in the case where all four sides are constrained, the load bearing capacity is determined not by the buckling of the glass but by the rigidity and the strength of the setting blocks that are used on each corner or the locally concentrated stress on the glass. 3. This experiment confirmed that tempered glass has sufficient horizontal load bearing capacity to be used as a quake-resistant wall. It is considered that tempered glass can be practically used as quake-resistant wall by further investigation the construction technique including a sash window frame and setting blocks that are used on the cross section of the tempered glass.

It took up a larch as the tree species of the laminated timber which has an influence on the Self-Extinguishing property from the gotten knowledge from the research in the past about the Self-Extinguishing phenomenon which is the characteristic of this structure in the present report. It reports a result of confirming a difference with internal temperature and Self-Extinguishing by the heating experiment about the existence or non-existence of steel and the sample under test with different section size mainly in the measurement of the crack about the temperature dater inside the laminated timber and the char layer after experiment.

Creep tests were performed at constant high temperatures for super high strength concrete.Then,for some of the specimens, the temperatures were maintained and compression tests were performed. Results of these tests revealed following.1)The effect of water-binder ratio on creep strain is minimal. 2)Creep strain of super high strength concrete is higher than normal concrete- at the same stress levels. 3)Increased creep strain is dependent upon elevated temperature but these increases are not uniform. 4)Creep strain is proportional to stress in the range 100℃ to 400℃. 5)Results of these tests can be simply formularized by Anderberg' s methoP.6)Increased strength and stiffness are observed for the sepecimens after creep tests.

The effects of high temperature on the mechanical properties of high strength concrete (HSC) have been studied experimentally at various temperatures that covered the 20&deg;C and the 100 to 800&deg;C temperature range at 100&deg;C increments. Concrete specimens of HSC were tested under compression at ages about 3, 6 and 12 months. The stress-strain curve of HSC under compression test exhibits brittle properties below 500&deg;C, and ductile properties above 500&deg;C. The compressive strength decreases to about 60-70% of the strength of room temperature at 100&deg;C, increases up to about 80-90% of the strength of the room temperature at 200&deg;C and gradually decreases with further increase of temperature. From these test results (including Ref.9 test results), mathematical expressions of the compressive strength, the strain at compressive strength, the stress-strain relationship and the modulus of elasticity were proposed. The comparatively good correlation between predicted and experimental results indicates the adequacy of the expression of stress-strain relationship.

This paper reports about the experimental bending capacity of the web moment connection between double-web H shaped beams and splice plates, which are made from aluminum alloy at elevated temperature. The bending moment capacity in 4 connection types at each temperature is from 70% to 100% of one of specimens without connection. Bending moment capacity is more improved by increment of web thickness of double

By an experiment and analysis, a comparison was made of the temperature of a total of 6 specimens of aluminum alloy member, which were 3 kinds of cross-section ( □-shaped and + -shaped pillars and II-shaped beam of double Web)covered with two kinds of Japanese cedar board (25mm and 35 mm thick), in a standard fire test. Experimental result shows fire endurance time of 40 min.〜 45 min. with 25mm thickness of cedar board and 50 min. 〜60 min. with 35 mm one, if limit temperature of aluminum alloy in structure is 350℃. The analysis result well followed the experiment result of the relation between temperature and time, and could suggest possibility of qualitative prediction of inside temperature in a fire.

Tension tests of friction type high strength bolted joints at elevated temperature were conducted in order to obtain the relationship between shear force and shear deformation of high strength bolts. High strength bolts do not fracture at temperature above 500℃ while shear deformation of bolts are less than the diameter of bolts. On the basis of these experimental results, we propose a formulation for the relationship between shear force and shear deformation in consideration of the residual post-peak shear strength. With this formulation, we can analysis the structural fire behavior of steel frame having high strength bolted joint.

This paper deals with the experimental study of the eartuquake resisting wall using toughened glass. Load bearing tests were conducted to determine the ultimate horizontal strength and deformation capacity. The result shows the wall using toughened glass has enough strength as the earthquake resisting wall for wooden house.

Fundamental studies on load bearing capacity of structural tempered glass members are carried out. This paper presents buckling tests of a glass column with reflecting reality specification in the high temperature atmosphere. The results are summarized as follows: 1) Buckling load of glass column in the high temperature atmosphere slightly decrease to 90percent in contrast to normal temperature. 2) Buckling load of laminated glass column in the high temperature atmosphere largely decrease to 60percent in contrast to normal temperature. 3) Decrease of an coefficient of Elasticity of buffer material doesn't influence buckling load.

It is reported in this paper that the bending capacity experiment of aluminum alloy H shaped beams at elevated temperature with bolted moment connection of web only and flange separated. The bending moment capacity from room temperature to 250℃ is about 70% of one without the bolted moment connection and nearly equal at 300℃ and 350℃. Bending moment capacity is expected to improve clearly by increasement of web thichness of H shaped beam because web thickness is 8 mm comparing with 60 mm of total splice plate thickness. In addition, deformation capacity is more than 2 times of the criterion of ISO 834

Buildings are designed and constructed under the assumption that a fire can break out. In this paper, the numerical results acquired by three-dimensional thermal stress analysis which takes the influence of a concrete floor slab into consideration, three-dimensional analysis which doesn't do that and planar analysis, are compared with the experimental values for a large-scale steel car parking exposed to fire. The influence of a concrete floor slab on fire-resistant performance of steel frames has been discussed by examining of the results based on three analytical methods described above. It is demonstrated that the bimetal effect caused by the temperature gradient within a concrete floor slab exposed to fire could reflect a significant impact upon structural members which support the floor slab.

Development of recent fire engineering has made it possible to estimate fire resistance capacity of structures including aluminum alloy structures. It was proposed simple evaluate method for steel structure at elevated temperature. It is expected that fire resistance of the Aluminum structure can be evaluated by the same method of the steel structure. At applying the simple method to aluminum structure, it is necessary to consider the difference of both mechanical properties. This paper presents particular mechanical properties of aluminum alloy at elevated temperature. As the results of comparison between steel and aluminum properties, by modifying the model of aluminum mechanical properties, it is recognized that fire resistance evaluation for the aluminum structure is possible by the simple method.

Fundamental studies on load bearing capacity of structural tempered glass members are carried out. This paper presents pure compression tests of a glass column with constraint at the longer edge and with reflecting reality specification. The results are summarized as follows: 1) Buckling load of glass column with constraint at the longer edge is obtained by theory equation. 2) Buckling load of glass column with constraint at the longer edge by seal is inverse proportionate to the ratio of glass spring to seal spring.

Fundamental studies on load bearing capacity of structural tempered glass members are carried out. This paper presents lateral buckling tests of a glass column with reflecting reality specification. The results are summarized as follows: 1) Lateral buckling load of glass column is proportionate to moment of inertia. 2) Lateral buckling load of glass column is invers proportionate to glass length. 3) Lateral buckling load of glass column with constraint at the center of longer edge by rod is obtained by theory equation.

Succeeding to the unit dividing structure analysis method for the problem of increased nodes which occurs in three-dimensional analysis of a building structure, this study shows the practical method of coordinate transformations of bar members considering the member movement and substitution method to cross beam from concrete slab. The method presented in this paper is shown to be available for three-dimensional analysis of a building structure exposed to compartment fire, based on some examples.

We carried out loaded heat tests about normal strength concrete made of clashed limestone coarse aggregate. Properties of the concrete at high teperatures have been tested previously. In this paper, the results are shown about the test with constant rate of heating and cooling. The rate is 1 ℃/min, 3 ℃/min and 6 ℃/min. Result of these tests has less shrinkage strain than the previous test. But the influence of rate of heating does not appear clearly. Using properties of the concrete at high temperatures tested previously, We try to calculate a strain of concrete at high temperatures with the constitutive model suggested by Anderberg and Thelandersson. In this model, the influence of creep strain at high temperatures is considered. Calculated strain is differ from result of the test shown in this paper in details. The influence of rate of heating on calculated strain is appeaed slightly.

When a compartment fire occurs in a building of steel structure, large bending deformations are produced at the ends of columns and beams, inducing local buckling at these points. In this study, the load-bearing capacity of H-shaped steel columns under local buckling is clarified from pure compression tests and bending compression tests at constant temperatures ranging from room temperature to 600°C. On the basis of the tests, we propose, in relation to the fire resistance of H-shape steel stub columns, a relation between safety usable steel temperature and constant axial load ratio. Copyright © 2005 International Association for Fire Safety Science.

Under fire attack, temperature of the concrete will become over 300℃. Creep of concrete is accelerated by effect of the high temperature. This paper shows short time creep of cylindrical test specimens and some infomations about creep recovery and time failure of them, by the tests under constant temperature conditions up to 700℃. The concrete was usual strength concrete made of coarse aggregate of limestone. At the tests, six compressive stress level variations were applied. Stress-strength ratio was 0.89 at the maximum. Result of the tests is expressed with creep coeficient. And, according to the creep-time relationship expressed with power function, we suggest a simple mathematical model. This model will be applied for analizations of concrete structures under fire attack with stress-strain relationship at high temperature. Stress-strain relationship at high temperature is avalable in some other investigations.

Compressive tests are carried out about mechanical properties of super high strength concrete exposed to fire as a part of experimental study. This paper presents basic data of thermal strain and total strain of super high strength concrete (water-binder ratio 18%, 24%, 35%) under constant stress and varying temperatures. The following results are obtained by this compressive tests. 1) An effect of water-binder ratio on thermal strain and total strain is little. 2) Super high strength concrete under constant stress and under varying temperatures shrinks more than normal concrete. 3) During a heating phase, increases of total compressive strain due to quantity of a constant stress on the specimen. On the other hands, during a cooling phase, variation of total strain is equal to decrement of thermal strain.

Fundamental study on load bearing capacity of structural tempered glass members was made a trial. This paper presents pure compression tests of a glass column with reflecting reality specification. The results are summarized as follows: 1) Flexural rigidity of a laminated glass is influenced by temperature. 2) The coefficient of buckling length is inverse proportionate to insert length into the support box. 3) The coefficient of buckling length is proportionate to glass thickness in case of same insert length.

Compressive tests are carried out about mechanical properties of super high strength concrete exposed to fire as a part of experimental study. This paper presents basic data of stress-strain curve, compressive strength, strain at compressive strength and modulus of elasticity of super high strength concrete (water cement ratio 18%, 24%, 35%) at constant high temperatures. Compressive strength ratio at high temperature by one at room temperature and strain at compressive strength are formularized as a function of temperature.