Perforated shell tube

Tubular Structural System Introduction As the building increases in height in excess of roughly 60 stories, the slender interior core and the planar frames are no longer sufficient to effectively resist the lateral forces. Therefore, the perimeter structure of a building must be activated to resist lateral forces In 1960s, the tubular principle for tall buildings were invented by the structural engineer Fazlur Khan of SOM(Skidmore, Owings & Merrill, Chicago) Introduction Lateral resistance of framed-tube: stiff moment resisting frames that form a tube around the perimeter of the building. Stiff moment resisting frame: closely spaced columns (2-4 m, 6-12 ft) jointed by deep spandrel girders . Introduction the outer shell (the walls are connected around the corner and internally braced by the rigid horizontal floor diaphragms) act as a three-dimensional hollow structure (closed box or circular beam) Introduction All the lateral loading -> tube The gravity loading -> shared between the tube and interior columns or walls. In the direction of lateral loading, the tube acts as the massive cantilever. Web frame: the perimeter frames aligned in the direction of lateral loading - resisting shear force Flange frame: the perimeter frames normal to the direction of the lateral loading - resisting moment (axial tension and compression forces in columns) Introduction [...]... Organization for tubular structure according to cross section(plan forms) Pure tubular concept Single perimeter tubes (punched, framed, or trussed) Tube- in -tube Bundled tube or modular tubes Modified tube Interior braced tubes Partial tubes Hybrid tubes Perforated shell tube – framed tube Tubes are three dimensional hollow structures internally braced by rigid horizontal diaphragms The only discipline... to the rectangular window openings A tube with small openings ( Deep spandrel tubes Opening size for typical framed steel tube: on the order of 50 % punched concrete tube: 30 - 40 % The typical exterior column spacing for framed tubes : 4 - 10 ft (1.2 - 3.0 m) The spandrel beam depth : 2 - 5 ft (0.6 - 1.5 m) Perforated shell tube – framed tube The proportions of the beam-column grid depends... exterior and be of a closed form Perforated shell tube - Unit Cantilever The entire spatial structure acts as a unit cantilever -> The moment is carried by the tube in tension and compression -> The shear is resisted primarily by the webs The effectiveness of the cantilever action of the simple perimeter tube depends on the size and shape of wall penetrations Perforated shell tube The small and round window... column spacing in steel construction requires many joints and thus tends to uneconomical > more efficient to use deep beam sections as columns rather than the conventional W14 columns Perforated shell tube – framed tube The net leasable area for the building is increased because the entire lateral load is resisted by the perimeter As a trade off, views from the interior of the building are limited... the modern glass boxes to reach true skyscraper proportions, Application of framed tube: WTC in N.Y (1972) 208 ft = 63.4 m 19 in = 0.57 m 3.33 ft = 1.10 m 78 in = 1.98 m 14 in = 0.36 m 25.96 in =0.66 cm 4.33 ft = 1.32 m 4.9.2 Framed tube behavior - The frame parallel to the lateral load act as "web" of the perforated tube, while the frames normal to the loads act as flanges - Vertical gravity forces... primary mode of action is that of vertical cantilevered tube - The columns on opposite sides of the neutral axis are subjected to tensile and compressive forces Shear Lag Phenomenon- 전단지연현상 A perfect tube for a tall building behaves as a true cantilever, resisting all the lateral forces in the exterior walls The closest structure to a perfect tube is one that consists of a system of perimeter walls... the corners of the building take more than their share of the load, while columns in between do less work than in an ideal tube A method of overcoming this problem is to stiffen the exterior frames with diagonals Braced Tube Structures The inherent weakness of the framed perimeter tube lies in the flexibility of its spandrel beams Its rigidity is substantially improved by adding sufficient diagonal members... The closest structure to a perfect tube is one that consists of a system of perimeter walls without any discontinuities Thickness of the wall is relatively small to the length of the tube -> around thickess:dimension of the tube plan = 1 : 70-100 Because of this characteristics, the structure has a tendency to behave like a thin-walled beam(박판보) Shear Lag Phenomenon- 전단지연현상 In a thin-walled beams the... windward and leeward faces may not undergo compression and tension > the structural effectiveness of the framed tube in greatly reduced by this effect Shear lag phenomenon plays a very important role in the design of tubular highrise structures Because of the shear lag phenomenon the framed tube has its limitations when used in buildings taller than 50 or 60 unless openings for windows are made relatively . webs Introduction. Basic organization for tubular structure Perforated shell tube Framed tube or Vierendeel tube Deep spandrel tube Trussed or braced tube Framed tube with belt truss Basic organization for. Bundled tube or modular tubes Modified tube Interior braced tubes Partial tubes Hybrid tubes Organization for tubular structure