INTERMEDIATE BASE ISOLATION STRUCTURE UTILIZING FLAT INVERSE BEAM

PROBLEM TO BE SOLVED: To provide a base isolation structure in which a base isolation layer and lower floors can be efficiently utilized by combining a flat inverse beam to an intermediate base isolation structure and accommodating a base isolation device smartly while suppressing a height of the base isolation layer in addition to structural advantages.SOLUTION: A flat inverse beam 2 which is used also as a pedestal is used as a beam of an outer peripheral part of a base isolation layer slab 3 forming a base isolation layer M of an intermediate base isolation structure, and a base isolation device 5 is installed on the flat inverse beam 2. An upper part of the flat inverse beam 2 is projected on an upper surface of the outer peripheral part of the base isolation layer slab 3 and forms a shallow recessed part inside and that portion is used as a piping pit. An underground pit portion is used as a piping pit hfor a first floor entrance e. An erected wall 6 is provided in an outer terminal portion of an outer peripheral chamber of the flat inverse beam 2, and each expansion spacing is formed under a lower surface of a veranda 18 of an upper floor and under a lower surface of an outside corridor 19. In such a state, weathering is facilitated while allowing horizontal movement in the base isolation layer M.