CIVL2240 Civil Engineering Materials Lecture 22 PDF

COLLEGE OF ENGINEERING, SCIENCE AND ENVIRONMENT CIVL2240 Civil Engineering Materials Lecture 22 Masonry (Fundamentals and Uses) Lecturer: Igor Chaves PhD (StructEng), MScEng (StructEng), BE (Civil)(Hons1), CMatP, TPC (ISOPE), AEditor (ASCE) Discipline of Civil, Surveying & Environmental Engineeri...

COLLEGE OF ENGINEERING, SCIENCE AND ENVIRONMENT CIVL2240 Civil Engineering Materials Lecture 22 Masonry (Fundamentals and Uses) Lecturer: Igor Chaves PhD (StructEng), MScEng (StructEng), BE (Civil)(Hons1), CMatP, TPC (ISOPE), AEditor (ASCE) Discipline of Civil, Surveying & Environmental Engineering EA 111 | T: 4921 2006 | e: [email protected]  History of Masonry Use Ancient Uses of Masonry Earliest Applications Uses of masonry (stone and sun-dried earth) date from the beginning of recorded history in Egypt, Mesopotamia and the Indus valley (ca 8,000 BCE); The earliest known use of kiln-fired bricks dates from about 5,000 BC. Mud Brick Palace and Arch at Ctesiphon, Iraq (Circa 550 AD) Roman Aqueduct, Segovia, Spain 2 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  History of Masonry Use Ancient Uses of Masonry Ancient Brick Construction Single structure providing: Strength + Water-tightness + Thermal protection. Wall Construction – Roman Forum Roman Colosseum 3 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  History of Masonry Use Modern Fired Clay Brick Masonry is Extremely versatile First Fleet brought some bricks; Convict bricks: hand-moulded wet clay whilst using clamp kilns (wood fired); Elizabeth Farm (Parramatta) – oldest existing brick building. Heritage Brick Veneer – Adelaide, SA Modern Concrete Masonry Units 4 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  History of Masonry Use Modern Fired Clay Brick Masonry is Extremely versatile Uses include: Bridges, Vaults, Arched doorways, Retaining walls, Tunnels, Buildings, etc. Cellar Vaults Supporting Heavily Loaded Floors Railway Tunnel – Blue Mountains, NSW 5 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  History of Masonry Use Modern Fired Clay Brick Gravity Masonry Structures Massive walls predominated until the 19th century; Where arches and domes spanned openings and walls relied on gravity for stability, hence, no tensile stresses were present. The last great example was the Monadnock Building in Chicago, USA. Built in 1891, it has 16 storeys with walls up to 1800 mm thick at the base 6 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  History of Masonry Use Modern Developments and Structural Solutions Cellular Masonry Structures Introduced in the 20th century, the structural concept utilises the high compressive and shear strengths and the finite tensile strength of the masonry. Cellular design of shear wall structures revolutionised the use of masonry. Other developments Reinforced masonry; Prestressed masonry; Diaphragm walls; Prefabricated Masonry. 7 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Manufacture of Masonry Units Fired Clay Masonry Units Manufacturing Process The standard 76mm x 110mm x 230mm (AS4455 Part 1) Fired Brick is exemplified. 8 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Manufacture of Masonry Units Fired Clay Masonry Units Raw Materials Step 1 – Raw Material Processing Primarily clays and shales but other materials can be added to control properties. The particular blend should match the moulding and firing processes and the properties of the desired finished product. Materials are mixed and ground to a fine particle size, then water is added to give the required plasticity. 9 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Manufacture of Masonry Units Step 1 – Raw Material Processing Raw Material Excavation and Stockpile Bulldozers rip material and stockpile in layers. Stockpile is built up in layers like a sandwich, to achieve the desired proportions. Typical Clay Pit – Austral Bricks Improved quality of the finished product is obtained through consistency of raw materials. 10 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Manufacture of Masonry Units Step 1 – Raw Material Processing Raw Material Crushing and Screening (Sieving) There are usually two size reduction stages, followed by screening to ensure quality. 11 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Manufacture of Masonry Units Step 2 - Shaping 12 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Manufacture of Masonry Units Step 2 - Shaping Shaping - Extrusion Moisture content 18% to 25% Soft extrusion and stiff extrusion. Clay is fed by an auger and a vacuum chamber removes any entrained air. Cores in the die produce perforations in the brick. The extruded column of clay is cut into bricks with a wire after any surface treatment is added. 13 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Manufacture of Masonry Units Step 2 - Shaping Shaping – Pressing Dry-pressed and semi-dry-pressed. Moisture content 10% to 12% Typically have sharp arises and a frog Stiff-plastic pressed Higher moisture content (14% to 17%) Two-stage process of moulding and pressing. 14 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Manufacture of Masonry Units Step 2 - Shaping Shaping – Deboer A rare process (now-a-days) Simulates hand-made mud/sandstock bricks Clots of clay are ‘thrown’ into moulds by the machine. 15 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Manufacture of Masonry Units Step 3 - Drying Controlled Forced Drying Stacked or loaded on racks for drying. Forced drying process must be carefully controlled for uniformity. It is necessary to avoid moisture gradients that lead to quality issues. 16 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Manufacture of Masonry Units Step 4 - Firing 17 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Manufacture of Masonry Units Step 4 - Firing Modern Kiln Tunnel and Gas Burners A computer room monitors every compartment of the kiln, as precision is paramount and requires careful control to follow the exact firing curve to suit raw materials. 18 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Manufacture of Masonry Units Step 5 - Packing 19 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  5 Minute Break Other Fired Clay Products (Terracotta Tiles; Rib & Block Slabs): 20 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Masonry Properties General Properties and Variability Masonry Properties Depend on: Variability in Properties: Properties of the masonry units; Natural variation in materials; Properties of the mortar; Variation in the manufacturing process; Compatibility of the units and mortar; Variations in site workmanship; Bonding pattern; Difficulty of controlling site-batched mortar; Workmanship and supervision Variation in porosity, moisture content etc; during construction; Typical CV is 0.15 for compression and 0.30 for flexural tension; 21 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Masonry Properties General Properties and Variability Behaviour in Compression The mortar joints induce tensile stresses in the units because of their lower elastic modulus. Failure is by tensile splitting of the units. Masonry strength is always less than the compressive strength of the units alone. Masonry strength is reduced by: Weaker units (lower tensile strength); Greater thickness of joints & Weaker mortar (i.e. lower stiffness). 22 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Masonry Properties General Properties and Variability Compressive Strength Test An unconfined strength based on height-to-thickness of five is used (as for masonry units). For hollow units, the face shell thickness is used and prism tests must use face-shell loading; Tabulated values (f 'mb) in AS3700 are based on unit strength and mortar class. Higher strengths from tests can be used but the masonry is then Special Masonry and must be tested during construction. 23 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Masonry Properties General Properties and Variability AS 3700 Compressive Strength of Masonry 24 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Masonry Properties General Properties and Variability Adjustment for Unit Height / Joint Thickness Ratio As the joint thickness increases for a given unit height, the compressive 1.4 strength reduces. 1.2 Compressive Strength Factor 1.0 Adjustment is made for joint thickness by a factor based on the ratio of unit 0.8 height to joint thickness - resulting in 0.6 a masonry strength f 'm 0.4 0.2 The factor is 1.0 for traditional 76mm 0.0 bricks and 10mm joints (i.e. ratio 7.6). 0 5 10 15 20 25 Unit Height/Joint Thickness 25 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Masonry Properties General Properties and Variability Tensile Strength for Design Testing is usually by the bond wrench method. Default characteristic value (without testing) is 0.2 MPa across the bed joints. A value up to 1.0 MPa can be used for Special Masonry, subject to testing. 26 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Masonry Properties General Properties and Variability Masonry Flexural Behaviour Masonry is anisotropic because of the bed and perpend joints. Three types of flexure: Vertical bending (tensile stress normal to the bed joints) Horizontal bending (tensile stress parallel to the bed joints) Two-way bending (principal tensile stress at an angle to the bed joints). 27 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Masonry Properties General Properties and Variability Vertical Bending The action is illustrated by a simple strip of masonry spanning between top and bottom supports (The weakest link analogy applies if all joints are subjected to the same bending). The joints usually have various levels of bending stress, which makes analysis more difficult. This effect is currently ignored in the AS 3700 design rules for bending. 28 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Masonry Properties General Properties and Variability Horizontal Bending Two modes of failure: Through bed and perpend joints (staggered failure line): When units are strong relative to bond. Through perpend joints and units (straight failure line): When bond is strong relative to the units 29 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Masonry Properties General Properties and Variability Horizontal Bending Test Load 30 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Masonry Properties General Properties and Variability Shear in Masonry There are three types of Shear Action: In-Plane - for example in a bracing wall Out-of-plane - for example in an out-of-plane laterally loaded wall Vertical shear - for example at wall intersections. 31 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Masonry Properties General Properties and Variability Shear Wall Behaviour 32 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Masonry Properties General Properties and Variability Masonry Shear Strength Tests Shear resistance comes from a combination of shear strength and shear friction. Friction is calculated using a shear factor and the compressive force. Shear strength f 'ms is related to bond at the unit-mortar interface and is usually proportional to f 'mt Where f 'ms is determined by extrapolating back to the axis intercept. The friction factor is the slope of the line. 33 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Masonry Properties General Properties and Variability Elastic Modulus of Masonry Values of E are required for calculation of deflections and relative movement. AS 3700 gives values for short-term and long-term loading, where values are proportional to f 'm and range from 500 f 'm to 1000 f 'm for short-term loading. It is important to note that the effect of creep, which is mostly in the mortar, causes the long-term modulus of elasticity to be approximately 1/2 to 2/3 of the short-term modulus. Other Masonry Properties Density: In the absence of more accurate data, the Australian loading code gives values, for example 0.19 kN/m2 for each 10 mm thickness of clay brickwork. Permeability: In the absence of an Australian standard test for water permeability, the ASTM test E514 can be used to evaluate a wall construction as there are no established performance criteria. 34 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Discussion Have any questions?! 35 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR