UNIVERSITY OF BEDFORDSHIRE TECHNICAL STUDIES f STRESS P
UNIVERSITY OF BEDFORDSHIRE: TECHNICAL STUDIES
f (STRESS) = P (force) / A (area) SUMMARY • Structural Systems in Nature • Structural Systems in Architecture • Forces in Architecture: Live and Dead Loads Equilibrium • Fundamental Principles: Newton’s Laws of Motion Forces Acting on a Body Stress Strain Elastic and Plastic Deformation Stiffness and Flexibility • Column and Beam: Origins and Architecture • Beams: • Columns: Transfer of Loads Turning Moments Bending Deflection Shear Buckling Effective Height Eccentric Loading UNITS: N/mm 2 (1 Pascal (Pa) = 1 N/m 2) STRAIN = Change in size (∆L) Original size (L) UNITS: % or decimal YOUNG’S = Stress Strain MODULUS UNITS: N/mm 2 (Pa) A stiff material has a high Young’s Modulus; a flexible material has a low Young’s Modulus Turning moment = w (force) x UNITS: Nm L (lever arm) NEWTON’S LAWS OF MOTION 1. A body remains at rest or in motion with a constant velocity in a straight line unless an external force acts on it 2. Force (Newton) = Mass (kg) x Acceleration (m/s 2) (Gravity on earth = approx. 10 m/s 2) 3. For every force acting on a body, the body exerts a force having equal magnitude in the opposite direction [INTRODUCTION TO STRUCTURAL PRINCIPLES, BEAMS AND COLUMNS : SUMMARY]
Pete Silver and Will Mc. Lean, Introduction to Architectural Technology (London: Laurence King, 2008) Francis D. K. Ching , A Visual Dictionary of Architecture (New York: Van Nostrand Reinhold, 1997) Derek Osbourn , rev. Roger Greeno, Mitchell’s: Introduction to Building, 2 nd ed. (Harlow: Longman, 1997) Jack Stroud Foster and Roger Greeno, Mitchell’s: Structure & Fabric, Part 1, 7 th ed. (Harlow: Prentice Hall, 2007) Jack Stroud Foster, Raymond Harington and Roger Greeno , Mitchell’s: Structure & Fabric, Part 2, 7 th ed. (Harlow: Pearson Prentice Hall, 2007) Alan Everett, rev. C. M. H. Barritt, Mitchell’s: Materials, 5 th ed. (Abingdon: Routledge, 2013) Peter Burberry, Mitchells: Environment and Services, 8 th ed. (Harlow: Longman, 1997) Alan Blanc, Mitchell’s: Internal Components (Harlow: Longman, 1994) Michael Mc. Evoy, Mitchell’s Building Series: External Components (Abingdon: Routledge, 2014) Yvonne Dean, Mitchell’s Building Series: Finishes, 4 th ed. (Abingdon: Routledge, 2014) Yvonne Dean, Mitchell’s: Materials Technology (Harlow: Longman, 1996) J. B. Mc. Kay, Mc. Kay’s Building Construction (Shaftesbury: Donhead, 2005); also available as separate volumes Sophie Pelsmakers, The Environment Design Pocketbook (London: RIBA, 2012) Charlotte Baden-Powell, Jonathan Hetreed and Ann Ross, Architect’s Pocket Book, 4 th ed. (Oxford: Architectural Press, 2011) Matthys Levy and Mario Salvadori, Why Buildings Stand Up: The Strength of Architecture(London: W. W. Norton, 1990) Matthys Levy and Mario Salvadori, Why Buildings Fall Down: How Structures Fail (London: W. W. Norton, 1992) Austin Williams, Shortcuts: Book 1: Structure and Fabric (London: RIBA, 2008) Austin Williams, Shortcuts: Book 2: Sustainability and Practice(London: RIBA, 2008) [RECOMMENDED READING: BOOKS]
LECTURE 1: INTRODUCTION TO STRUCTURAL PRINCIPLES, BEAMS AND COLUMNS LECTURE 2: LOAD-BEARING WALLS AND STRUCTURAL OPENINGS LECTURE 3: TRUSSES, FRAME STRUCTURES AND SLABS LECTURE 4: COMPLEX STRUCTURAL SYSTEMS LECTURE SERIES 1: STRUCTURE AND FORM
Architects’ Journal [RECOMMENDED READING: MAGAZINES / SERIES] Architects’ Working Details (Architect’s Journal/EMAP)
Detail magazine [RECOMMENDED READING: MAGAZINES / SERIES]
LOAD-BEARING WALLS Transfer of loads Crushing Eccentric Loading Buckling Overturning
f (stress) = P (force) / A (area) UNITS: N/mm 2 (1 Pascal (Pa) = 1 N/m 2) [FUNDAMENTAL PRINCIPLES: STRESS]
Compressive stress distributed Compressive stress increases towards the base Battered wall WALLS: TRANSFER OF LOADS Vertical wall
1. Closely spaced beams/loads: even distribution of loads 2. Opening in the wall: increase loading around edges of window WALLS: TRANSFER OF LOADS 3. Wider spaced beams/loads: more uneven distribution of loads, especially at head of wall 4. Very widely spaced beams/loads: very uneven distribution of loads at head and base of wall
5. Very widely spaced beams/loads: pilasters used to carry load WALLS: TRANSFER OF LOADS
• Loads should usually be concentrated in the middle third of the horizontal section of the column to prevent tensile stresses developing [COLUMNS: ECCENTRIC LOADING]
• Crushing is caused by over-stressing a material and is avoided by adequate thickness at all points to keep the stresses within the safe compressive strength of the material. WALLS: CRUSHING AND ECCENTRIC LOADING • Eccentric loading increases the compressive stress in the wall on the loaded side and decreases on the other, causing bending in the wall.
• The greater the slenderness ratio, the greater the tendency for a wall/column to buckle. WALLS: BUCKLING
[COLUMNS: BUCKLING]
The tendency for a wall to buckle relates to its stiffness. Methods to reduce buckling in a wall: - limit height - increase thickness - buttresses - intersecting walls - intersecting floors/roof - reduce loads WALLS: BUCKLING
WALLS: BUCKLING
WALLS: OVERTURNING
resultant force within area of buttresses WALLS: OVERTURNING
WALLS: OVERTURNING - BUTTRESSES
WALLS: OVERTURNING - BUTTRESSES
WALLS: OVERTURNING - BUTTRESSES
Notre Dame Cathedral, Paris, 14 th century WALLS: OVERTURNING - BUTTRESSES
STRUCTURAL OPENINGS Greek and Roman Architecture Lintels Arches
STRUCTURAL OPENINGS: GREEK AND ROMAN ARCHITECTURE
STRUCTURAL OPENINGS: LINTELS
Active force/load Transfer of load to supports Reaction STRUCTURAL OPENINGS: LINTELS Reaction
STRUCTURAL OPENINGS: ARCHES
Catenary Curve The shape assumed by a hanging chain or cable when supported only at its ends. Parabola The shape assumed by a hanging chain or cable when a vertical load is uniformly distributed across it’s width. It is almost identical to a catenary curve (but not quite) STRUCTURAL OPENINGS: ARCHES
STRUCTURAL OPENINGS: ARCHES
STRUCTURAL OPENINGS: ARCHES
STRUCTURAL OPENINGS: ARCHES
St Chapelle, Paris, 13 th century
Antoni Gaudi, Catenary Model Antoni Gaudi, Casa Mila, Barcelona, 1910
Antoni Gaudi, Catenary Model
Antoni Gaudi, La Sagrada Familia Cathedral, Barcelona, 1882 -2026 Antoni Gaudi, Catenary Model
Richard Hawkes, Arched Eco House, 2009 Grand Designs video link
Sheffield Winter Gardens, Pringle Richards Sharratt Architects and Buro Happold (Structural Engineers), 2003
SUMMARY • Load-Bearing Walls -Transfer of loads - Crushing - Eccentric loading - Buckling - Over-turning • Structural Openings -Lintels - Arches LOAD-BEARING WALLS AND STRUCTURAL OPENINGS: SUMMARY
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