鉄筋コンクリート造集合住宅における火災によるコンクリートの強度低下に関する研究

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  • STUDY ON STRENGTH REDUCTION OF CONCRETE IN REINFORCED CONCRETE APARTMENT BUILDINGS BY FIRE-DAMAGED
  • テッキン コンクリートゾウ シュウゴウ ジュウタク ニ オケル カサイ ニ ヨル コンクリート ノ キョウド テイカ ニ カンスル ケンキュウ

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<p> If a fire occurs, the building will be damaged. And most of them remain in a state where they have been damaged to some extent by structural members.</p><p> In apartment buildings, it is required that the main structural part is a fireproof structure, and the type of structure is often reinforced concrete or steel-frame reinforced concrete.</p><p> In order to reuse a damaged building after a fire, it is necessary to grasp the damage range and depth of the damaged part concrete and secure the same performance as before the damage for the damaged area, the property of the building It is important in terms of value.</p><p> In this study, the core is drilled from the heating surface of concrete after single-sided heating using a gas furnace, in order to grasp the strength reduction and damage depth of the damaged part concrete in the ceiling slab of RC apartment house, The relationship between the maximum temperature of the concrete heating surface and the compressive strength was determined.</p><p> In addition, the small size core was used to capture the change in strength between the surface side and the inner side of the heated and cooled concrete. Furthermore, with the sliced specimen cut and shaped in the depth direction from the heating surface of the concrete after heating and cooling, the flexural strength for each depth was confirmed from the heating surface side inward, and the damage depth was estimated. The findings obtained in this study are summarized below.</p><p> (1) Compressive strength by core</p><p> The compressive strength residual ratio of the core collected from the surface heated by concrete decreased as the maximum temperature reached by the heated surface increased (concrete fire duration time lengthened). In addition, from the relationship between the color change of the concrete and the presence or absence of cracks and the compressive strength residual ratio of the core, during the fire damage investigation, by observing the presence or absence of color change or cracks of the surface of the affected area concrete, It is possible to estimate the compressive strength residual ratio.</p><p> (2) Compressive strength by small size core</p><p> When the compressive strength in the depth direction of the damaged concrete was compared using the small diameter core, a difference occurred between the heated surface side and the inner side. In addition, a correlation was found between the maximum temperature and the compressive strength of the small diameter core collected.</p><p> From these things, it is possible to estimate the degree of damage if the heat receiving temperature of the affected area concrete and the fire duration time are known in the fire damage investigation.</p><p> (3) Flexural strength by core slice test piece</p><p> The damage depth was grasped by finding the flexural strength continuously from the heating surface to the inside with the core collected from the damaged concrete. From this result, at the time of fire damage investigation, it is possible to obtain the damage depth of the damaged concrete and indicate the depth at which it is judged that the repair is necessary.</p><p> By this study, although it is limited, the tendency of the compressive strength from the core or small diameter size core to observe the color change of the heated surface of the damaged concrete in the fire damage investigation of RC apartment buildings and the presence or absence of cracks etc. We have shown the possibility of clarifying the damage area and depth of damaged concrete structural members by capturing It is thought that it is possible to estimate the repair range and depth of a concrete structural member by this.</p>

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