Lecture 3: Structure & Architecture PDF

## STRUCTURE & ARCHITECTURE EA33 THEORIES OF ARCHITECTURE 2 Lecture 3 Associate Prof. Mona Naguib The structure is present in order to do its mundane job of supporting the building envelope. In this kind of architecture structural engineers act as facilitators - the people who make the building...

## STRUCTURE & ARCHITECTURE EA33 THEORIES OF ARCHITECTURE 2 Lecture 3 Associate Prof. Mona Naguib The structure is present in order to do its mundane job of supporting the building envelope. In this kind of architecture structural engineers act as facilitators - the people who make the building stand up. It was the structural techniques which were developed in the twentieth century which made free form architecture possible, and which gave architects the freedom to exploit geometries which in previous centuries would have been impossible to realize. ## STRUCTURE SYSTEMS (DETERMINING THE STRUCTURE FORM) The structure system is defined by 3 system components each effecting the other: - **Forces:** - Dynamic system of load transfer and control of forces. - **Geometry:** - Descriptive system of structural form and path of forces. - **Material:** - Material system for control of forces and effectuation of geometry. (steel, reinforced concrete, masonry, timber) ## 1. STRUCTURE TYPES - **Post and beams** (load bearing walls / Skeleton structure) - **Framed Structure** (The portal frame / Space Frame trusses) - **Vaults and Domes** - **Shell structure** (It also insludes geodesic Dome & Voronoi grid shell Structure) - **Tents and Cables network** ## A) Post-and-beam structures Post-and-beam structures are either loadbearing wall structures, Skeleton or frame structures. ### Loadbearing wall structures: - A series of horizontal elements is supported on vertical walls. - The buildings usually consists of two sets of walls: loadbearing walls and bracing walls to provide stability of the building. - The loadbearing walls, which carry the weights of the floors and roof, are usually positioned more or less parallel to one another at approximately equally spaced. - Roofs supported with vertical elements subjects of compression. - The walls can be either timber or masonry. - The floors and roofs are normally of timber or reinforced concrete. - Reinforced concrete floors are also capable of larger spans than are timber floors. - Maximum span is 5.80 m - Minimum thickness of exterior walls in one-story buildings shall be 25.4 cm and internal walls not less than 20.3 cm. **Advantages:** - The structures are straightforward and economical to construct. **Disadvantages:** - Restrictions on the freedom of the designer to plan the form of the building. - None of the spaces is very large. - In multi-storey buildings, a plan which is more or less the same at every level. - Limitations for openings in walls. ### Post-and-beam structures (Skeleton) - The skeletal structure consisting of beams supported by columns, with some form of slab floor and roof. - The walls are usually non-structural and are supported entirely by the beam-column system. - The total volume which is occupied by the structure is less than with loadbearing walls. - The beams can be reinforced concrete, timber, I-section beam steel or trusses steel. - The columns can be reinforced concrete, timber or I-section beam steel. **Advantages:** - Large interior spaces can be achieved / large openings - Variations in floor plans between different levels in multi-storey buildings. **Disadvantages:** - Higher construction cost than the load bearing wall ### Post-and-beam structures (Skeleton) - The maximum span in residential buildings is 7.5m - In commercial buildings, it can be up to 10m - The calculation of the beam depth and width for 5m span - Width of beam = Depth/1.5 (width of beam should not be less than 200 mm). - Span of simply supported beam = 5000mm - Effective depth of beam d = 5000/20=250mm - Total depth of beam = effective depth + diameter of bar/2 + clear cover size. - Assume clear cover size = 25mm - Diameter of bar = 16mm - Total depth D = 250mm +16/2mm +25mm - Total depth D= 283mm, It should be taken as 300mm = 30cm #### Reinforced Concrete - For 9m span need 50cm depth of beam - For 10m span need 60 cm depth of beam ### Post-and-beam structures (waffle slab) - Slab depth is typically 7.5 cm to 13 cm thick. As a rule of thumb, the depth should be 1/24 of the span. - The width of the ribs is typically 13 cm to 15 cm, and ribs usually have steel rod reinforcements. - The distance between ribs is typically 9.15 cm. - The height of the ribs and beams should be 1/25 of the span between columns. - The width of the solid area around the column should be 1/8 of the span between columns. Its height should be the same as the ribs. ### Post-and-beam structures (Fat slab) - Flat slab - Span from 6 to 9 m - Minimum Slab thickness 12.5 cm #### Uses of Flat Slab - These slabs are primarily useful for parking garages, ramps, highrise buildings, hotels, and industrial structures. - These slabs are also suitable where the use of beams is restricted. Since flat slabs don't need beams, floor height can be minimized, reducing the building height. Also, reduce the load on the foundation. - It can save approx 10% of the vertical member. - Since the beams are absent in the flat slab, it is easier to install sprinklers and pipes for other use. ## B) Frame structure They may be chosen if the shape of the building can not be supported by simple post-and-beam structure. **Advantages:** - Achieve greater efficiency than a post-and-beam structure, because a long span is involved. - Frames economically achieve spans of up to 50 m. ### Frame structure The stadium comprises two parts that were built separately: the woven steel structure and the interior concrete grandstands. The primary structure of the steel frame is formed by 24 portal girders welded together into a single unit. The secondary structure, which consists of irregularly arranged columns and struts, which serve as braces, supports this structure. ## B) Frame structure ### Space Frame Trusses A space frame or space structure is a truss-like, lightweight rigid structure constructed from interlocking struts in a geometric pattern. Space frames can be used to span large areas with few interior supports. Like the truss, a space frame is strong because of the inherent rigidity of the triangle; flexing loads (bending moments) are transmitted as tension and compression loads along the length of each strut. ### Space Frame Trusses The space frame (also called 3D truss or a space structure) is a rigid structure with truss-like composition that consists of several struts that are interlocked in a geometric pattern. Polycarbonate sheets, fiberglass reinforced plastic sheets or glazing used for covering, to provide aesthetically beautiful sky light systems. However, colour-coated steel sheets, aluminium sheets and asbestos sheets are also used. - Space frames may cover very large spans (10-150 m) and they are usually used for big buildings and big stores . - Space frames are built of steel bars and connections. ### Space Frame Trusses - It is light weight structure - Long span and cantilevers - The units of space frames are usually mass produced in the factory. - Units are often of standard size and can be easily transported and rapidly assembled on site by semi-skilled labour. - It can be built at a lower cost. Applications: Malls, Food courts, Transport terminals, Schools, Pools, Arenas, Entertainment, Hospitals, Hotels, Corporate & Commercial Buildings, Convention centers ## C) Vaults and Domes A structure forming the curved, pointed, or flat upper edge of an open space and supporting the weight above it, as in a bridge or doorway in the case of vaults and domes, this internal force is compressive also in mosques and churches. - They are therefore normally constructed in materials which perform well in compression, such as : - masonry or - concrete. - wood - As with domes and vaults they are used in situations in which high structural efficiency is desirable, such as for long spans or where a lightweight structure is required. ## C) Vaults and Domes In the pre-industrial age the structural form which was used for the widest spans was the masonry vault or the dome. - Large-span interiors can be created in masonry only by the use of domed or vaulted structures. This was the principal reason for the use of this type of arrangement prior to the invention of modern materials such as steel and reinforced concrete which allow large spans to be achieved with post-and-beam forms due to their ability to resist bending effectively. - The development of reinforced concrete in the late nineteenth century allowed the extension of the maximum span which was possible with the compressive form-active type of structure. - Its cross-section must be sufficiently thick to prevent the tensile bending stress from exceeding the compressive axial stress which is also present. ## C) Vaults and Domes For the Palazzetto dello Sport, Rome, Italy, 1960; Pier Luigi Nervi, architect/engineer. - Influenced by the geometry-based domes of ancient Roman architecture and combined it with reinforced concrete and radical-for-the-era prefabrication techniques. - The structure was a ribbed concrete dome, more than 60 meters in diameter and supported on the exterior of the building by Y-shaped concrete buttresses. It was cast in prefabricated sections and snapped together in just 40 days. ## D) Shell structure Shells belong to the family of vaults and domes - The most popular type of thin shell structure are: - Concrete shell structures, often cast as a monolithic dome or stressed ribbon bridge or saddle roof - Lattice shell structures, also called grid shell structures, often in the form of a geodesic dome or a hyperboloid structure - Membrane structures, which include fabric structures and other tensile structures, cable domes, and pneumatic structures. ## D) Shell structure Shells belong to the family of vaults and domes - They have geometries which are more complicated than post-and-beam or semi-form-active types and they produce buildings which have distinctive shapes. The shown example: (Brynmawr Rubber Factory, Brynmawr, UK, 1952) - Its nine great, low domes of 80mm-thick reinforced shell concrete, each 25 by 19m, were the work of structural engineer Ove Arup and colleagues, employing patents newly 'liberated' from Germany. Punctured by circular roof lights and wrapped by clerestory glazing, they ensured a flood of light to the 6,000sq m main floor below, interrupted only by four V-shaped supports. ## D) Shell structure TWA Terminal, Idlewild (now Kennedy) Airport, New York, USA, 1962; Eero Saarinen, architect. ## D) Shell structure Opera House, Sydney, Australia, 1957-65; Jorn Utzon, architect; Ove Arup & Partners, structural engineers. - The upper drawing here shows the original competition- winning proposal for the building which proved impossible to build. - The lower drawing is the final scheme, though technically ingenious, is considered by many to be much less satisfactory visually. ## D) Shell structure Opera House, Sydney, Australia, 1957-65; Jorn Utzon, architect; Ove Arup & Partners, structural engineers. - Ove Arup & Partners undertook extensive engineering research and calculations over four years, including 'tens of thousands of man-and-computer-hours' at their London office. - They proposed over a dozen different geometries for the shells and different ways of studying them, starting with parabolic surfaces, moving to ellipsoid schemes and then on to circular arc rib proposals. ## D) Shell structure SYDNEY OPERA HOUSE: SYSTEM SPANS AND EFFECTIVE SPANS: - THE "SHELLS" WERE PERCEIVED AS A SERIES OF PARABOLAS SUPPORTED BY PRECAST CONCRETE RIBS. THE FORMWORK FOR USING IN-SITU CONCRETE WOULD HAVE BEEN PROHIBITIVELY EXPENSIVE, BUT, BECAUSE THERE WAS NO REPETITION IN ANY OF THE ROOF FORMS, THE CONSTRUCTION OF PRE-CAST CONCRETE FOR EACH INDIVIDUAL SECTION WOULD POSSIBLY HAVE BEEN EVEN MORE EXPENSIVE. - THE DESIGN TEAM WENT THROUGH AT LEAST 12 ITERATIONS OF THE FORM OF THE SHELLS TRYING TO FIND AN ECONOMICALLY ACCEPTABLE FORM (INCLUDING SCHEMES WITH PARABOLAS, CIRCULAR RIBS AND ELLIPSOIDS) BEFORE A WORKABLE SOLUTION WAS COMPLETED. IN MID-1961, THE DESIGN TEAM FOUND A SOLUTION TO THE PROBLEM: THE SHELLS ALL BEING CREATED AS SECTIONS FROM A SPHERE. THIS SOLUTION ALLOWS ARCHES OF VARYING LENGTH TO BE CAST IN A COMMON MOULD, AND A NUMBER OF ARCH SEGMENTS OF COMMON LENGTH TO BE PLACED ADJACENT TO ONE ANOTHER, TO FORM A SPHERICAL SECTION. ## D) Shell structure SYDNEY OPERA HOUSE: FINISHES: - ACTUAL CLAY, BRICK, AND STONE VENEER - GRANITE OR MARBLE CLADDING - EXPOSED AGGREGATE FINISH - SAND BLASTED FINISH - FORM LINER PATTERNS - THE SYDNEY OPERA HOUSE USES WHITE GLAZED GRANITE TILES. 1,056,000 TILES WERE USED TO COVER THE MASSIVE STRUCTURE. ## D) Shell structure SYDNEY OPERA HOUSE: CONSTRUCTION: ## D) Shell structure Residential house ## D) Shell structure A geodesic dome - Is a hemispherical thin-shell structure (lattice-shell) based on a geodesic polyhedron. The triangular elements of the dome are structurally rigid and distribute the structural stress throughout the structure, making geodesic domes able to withstand very heavy loads for their size. - Every dome has 6 pentagons - the shape made of 5 struts, 1 at the top and 5 around the sides. To find the frequency of the geodesic pattern, simply count the number of struts between the centers of two adjacent pentagon patterns. The following figure, for instance, find a pentagon (highlighted in the figure) and the next pentagon. Then add up the number of struts between the centers of these two pentagons. The number is the geodesic dome frequency. We call the figure below a 4-frequency dome and 5-frequency dome. The frequency is commonly abbreviated as "V", so a 4-frequency dome is called 4V, 5-frequency is 5V, and so on. ## F) Veronoi Structure Water Cube | Beijing National Aquatics Center - Fig. 1. Delaunay Triangulation and Voronoi Diagram - divisions also represent a dual graph relative to each other; a creating the Voronoi Diagram based on the Delaunay triangular grid divisions; b - Delaunay triangulation and Voronoi diagram for a given group of points set of given points - Delaunay triangulation for given points - determination of the center of the circle of the triangle - Voronoi diagrams for given points - centers of the circles determine the vertices of a convex polygon - Voronoi diagram - dual graph ## E) Tensile and cable Network Tents and cable networks are tensile equivalents of domes and vaults. The internal forces which occur in these structures are those of axial tension it is highly efficient in resisting load. - It is used when long spans or where a lightweight structure is required. ## E) Tensile and cable Network Two important types of tensile structure - Membranes, - Masted structure ### Membranes Structure - Mesh of steel cables which are either drawn up from above using external masts ) صاري( or proposed up by internal masts from below. - A structural and weather membrane is attached (Teflon and coated glass fiber) - Membrane can adopt the form of shells 50-150 m. ## E) Tensile and cable Network Two important types of tensile structure - Membranes, - Masted structure ### Masted Structure - Internal or externally supported with span 50mto 500m - Masted structures can also be of the grand stand type (single cantilevered structure) from metal or reinforced concrete. ## E) Tensile and cable structure Olympic Stadium, Munich, Germany, 1968-72. Behnisch & Partner, architects, with Frei Otto. - The struc- ture of this canopy consists of a network of steel wires (the very fine square mesh) supported on a system of masts and cables. The pattern of heavy rectangular lines results from the flexible joints between the cladding panels. Highly efficient structure types such as this are required where long spans are involved. ## Selection of Structural Material Architect must be fully aware of the nature of the relationship between technical and aesthetic issues: - **Steel** This is a high strength material (the strongest). Steel is used for the tallest buildings and the longest spans: skeleton frames, portal frames, horizontal or curved trussos, space frames and tonsile structures. - **Reinforced Concrete** Reinforced concrete is used for load-bearing walls (blocks), skeleton frames (beams and columns), arches, vaults, domes, folded roofs, and shells. - **Masonry (brick)** Masonry is used for small and medium spans in the form of load-bearing walls (vertical elements) and for arches, vaults and domes (horizontal elements). - **Timber (wood)** Timber has been used as horizontal elements (floors or roofs) of post and beam structures when vertical elements are made out of masonry or timber framing. As sloping roofs by using systems of rafters as well as systems of truss and purlins of different shapes. As skeleton frames, and for large spans as portal frames, domes, vaults, folded roofs, and shell forms. ## References - **TIME SAVER STANDARD FOR BUILDING TYPES** - FREE PDF: https://ia801303.us.archive.org/5/items/TimeSaverStandardsForBuildingTypes/Time-saver%20Standards%20for%20Building%20Types.pdf - **Andrew Charleson, 20145, Structure As Architecture, A Source Book for Architects and Structural Engineers, Routledge** - **https://www.slideshare.net/aaqibiqbal940/structural-systems-notes** - **https://www.slideshare.net/ymahgoub/architectural-design-1-lectures-by-dr-yasser-mahgoub-lecture-8-structure** - **https://www.slideshare.net/SusmitaPaul12/shell-structure** - **https://www.civillead.com/flat-slab/** - **https://civilsir.com/beam-depth-for-5m-6m-7m-8m-9m-and-10m-span-formula/**