平島 岳夫

The braced structure is composed of the comparatively smaller members than the rigid structure. So, it is necessary to confirm the stability of the braced structures exposed to fire. The subjects of the steel braced structure without a fire protection are followings. 1) Load bearing capacity of columns in fire, 2) Influence on members surrounding the fire compartment. In this paper, numerical analysis of thermal stresses and deflections is carried out to indicate the stability of steel braced structure considering the influence of upper extended compartment fire. The result of analysis indicates that the local collapse of core part causes the collapse of the whole structure.

本研究は,Fc80～Fc100の超高強度コンクリートを用いた鉄筋コンクリート柱の耐火性について解析的に検討したものである。解析は,コンクリートの爆裂を考慮した熱伝導解析により得られる断面内の温度時刻歴を用いて,コンクリートと鉄筋の応力歪,熱膨張歪,クリープ歪およびコンクリートの過渡歪を考慮した熱応力変形解析である。縮小模型柱の載荷加熱実験結果から本解析手法の妥当性を検証し,実大断面柱の長期荷重下における高温軸圧縮性状について解析的に検討した。その結果,超高強度コンクリートを用いた実大断面柱は3時間をはるかに上回る耐火性能を有するものと考えられる。

The Large-scale fire test is carried out in a 4-story type car park at the deepest part of the ground floor. This experimental results indicate that car fire spreads one after another, the steel temperature of the beam located above the combusted vehicle reaches near to 700°C and the frame stability is maintained [1]. This paper presents the two-dimensional structural analysis of the thermal stresses and deflections about this experiment. Copyright © International Association for Fire Safety Science.

Recently, a lot of multi-story car parks of steel structure without a fire protection are constructed and many of them are braced structures. It is indicated that the rigid steel structure is satisfied with load bearing capacity up to about 600℃ in accordance with the seismic design standard in Japan. Because the braced structure is composed of the comparatively smaller members than the rigid structure, it is necessary to confirm the stability of the braced structures exposed to fire. In this paper, the analysis of thermal stresses and deflections is carried out to indicate the stability of steel braced structure in fire. When the fire develops in the braced portion, the large compressive strain yields at the columns exposed to fire. It is expected that local collapse of core part extend to the collapse of the whole structure.

Large-scale fire tests of 4-storey car park were carried out and this tests had proved that fire spread to neighboring cars one after another. This paper presents thermal stress analysis of the frame exposed to car fire at the ground floor about large-scale tests. The results are summarized as follows: 1) The frame did not collapse the same as large-scale fire tests. 2) Outer columns are subjected to severe thermal stress and large deformation and it is possible to remain after a fire. 3) The frame displacements values calculated by the thermal stress analysis corresponded closely to the tests results. But this two-dimensional analysis could not adjust the experimental deflection of partial beams exposed to fire.

The concept of transient strain was introduced in order that the behavior of RC structure in fire cannot be made clear only by thermal expansion, stress strain and creep strain. Although it is reported that transient strain account for a big rate to total strain, the experimental study on transient strain is few in Japan. Especially, It is important for forecast the deformation of RC structural member in fire to evaluate transient strain accurately . Therefore as main purpose, experiments carried out to set quantification of transient strain of concrete.This paper presents basic data of compressive strength and creep strain characteristic of concrete at elevated temperature.

Tension tests of friction type high strength bolted joints at elevated temperature were conducted for the fire engineering design of steel structures. The results are summarized as follows: 1) Friction type becomes bearing one in high tension bolted joint beyond 500℃ because of slip load reducing under a half of allowable shear strength for sustained loading. 2) The shear strength of high tension bolt becomes lower than the allowable shear strength for sustained loading near to 600℃. 3) The maximum shear strength of friction type high tension bolted joints can be approximately evaluated from the tensile strength of the bolt materials.

This paper presents three kinds of experiments, stub column tests, bending tests and beam column tests, with wide flange shapes and square steel pipes made of conventional structural steels at elevated temperature and their numerical analysis. Experiments were conducted to obtain strength-deformation relations including local buckling of steel members at elevated temperature. Their numerical analysis were based on models of stress-strain curves including local buckling. As a result, the residual steel member strength due to local buckling could be obtained numerically and the calculated values corresponded closely to the experimental results.

The braced structure is often used for a case of open deck car park and its columns are under high axial force. When they are exposed to fire, its columns and beams are subjected to severe thermal stress and large deformation and the development of local buckling is expected. In this study, thermal deformation analysis is carried out and fire behavior of braced structure is investigated.

The beams and columns exposed to compartment fire are subjected to severe thermal stress and large deformation and the development of local buckling is expected. Especially the beams and columns are subjected to large bending deformation. In this paper, experimental results of pure compression test and pure bending test at elevated temperature are reported. Experiments are carried out about H and channel shaped members made of fire resistance steel. And experimental results are compared with the results obtained by numerical analysis.

The beams and columns exposed to compartment fire are subjected to severe thermal stress and large deformation and the development of local buckling is expected. Especially, the outer column is subjected to large bending deformation and the inner column is subjected to small bending deformation. To investigate the column deformation capacity at elevated temperature, experiments are carried out about H and box shaped columns made of fire resistance steel. This experiment is forcused in the bending deformation and load bearing capacity of outer columns.

In analyzing thermal stress and deformation of high rise steel structLlrere exposed to a compartment fire, it is convenient to divide the structure into three substructures. In the local substructure which is directly exposed to fire, thermal stress and deformation are normally in elasto-plastic range and local bucklings are developed. In this study, numerical analysis is carried out, considering the influence of the local buckling. The result of analysis indicates the development of local substructure collapse.