CIVL2240 Civil Engineering Materials Lecture PDF

COLLEGE OF ENGINEERING, SCIENCE AND ENVIRONMENT CIVL2240 Civil Engineering Materials Lecture 23 Masonry (Commercial Masonry) Lecturer: Igor Chaves PhD (StructEng), MScEng (StructEng), BE (Civil)(Hons1), CMatP, TPC (ISOPE), AEditor (ASCE) Discipline of Civil, Surveying & Environmental Engineering...

COLLEGE OF ENGINEERING, SCIENCE AND ENVIRONMENT CIVL2240 Civil Engineering Materials Lecture 23 Masonry (Commercial Masonry) 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]  Components and Terminology Masonry Unit Types Masonry Units are made of: Clay: Usually cored (extruded) or solid (pressed). Commonly 230x110x76 mm. Concrete: Usually hollow and mould vibrated. Commonly 390x190x190 mm. Calcium silicate: Also known as sand-lime. Autoclaved aerated concrete (AAC). Stone. NOTE: Relationship between the three dimensions is important for bonding and for building corners. 2 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Components and Terminology Masonry Unit Types Masonry Terminology: 3 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Components and Terminology Masonry Walls Wall Construction Terminology: Stretcher: A brick laid along the wall Header: A brick laid through the wall Soldier: A brick laid on end Closer: A brick, less than full size, used to bring the end of a wall to a vertical face. Pig in a wall: A situation where, for a given height at each end of a wall, there is a different number of courses. 4 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Components and Terminology Masonry Walls Wall Construction Terminology: Bedding type, Joint Finishes; Bond Types. Full bedding Face Shell bedding 5 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Components and Terminology Masonry Walls Arch Terminology: 6 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Mortar, Grout and Reinforcement Mortar Properties Mortar Function and Constituents Spreads the load, takes up irregularities in the units and bonds with the units to give tensile strength. Usually consists of cement, lime, sand and water (and sometimes additives). Ingredients, traditionally, are batched by volume: Common mix ratio: 1:1:6 (Cement : Lime : Sand). Specifications to AS3700 Classified M1, M2, M3, M4 in order of increasing strength and durability. NOTE: It is important to specify the cement type and check the bag on the construction site. 7 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Mortar, Grout and Reinforcement Mortar Properties Mortar Additives Plasticizer (entrained air). Example: Bycol (do not overdose!). Enhances workability, especially for sands with low clay content. Water thickener (methyl cellulose). Example: Dynex Retains water against the suction of the unit Useful for sharp sands and is recommended for concrete and calcium silicate units. Others types: Pigments. Set retarders (no sugar drinks!). Bonding polymers. 8 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Mortar, Grout and Reinforcement Grout and Reinforcement Properties Grout Filled Reinforced Masonry For filling cores and cavities in reinforced masonry. Should be matched to the masonry unit strength but not less than 12 MPa. Specially designed grout mixes of pouring consistency should be used. Mixing a slurry from mortar is not suitable. 9 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Masonry Ties and Accessories Ties and Connectors Wall Ties and Accessories Must comply with AS2699 and AS3700. Corrosion protection is required in accordance with the exposure conditions. All ties and connectors must be designed for the imposed loads according to procedures in AS3700. 10 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Masonry Durability Deterioration Mechanisms Salt Attack Dissolved salts enter the masonry. Drying out causes crystallisation just below the surface. Expansion of salt crystals causes spalling. Attack can be to the masonry units, the mortar, or both. 11 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Masonry Durability Deterioration Mechanisms Efflorescence A white powdery deposit caused by dissolved salts from the units themselves. Common on new construction but generally passes with time. Concrete units are more susceptible than clay. A test method is available to measure potential to effloresce but it is a research tool, not a routine means of evaluation. 12 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Masonry Durability Deterioration Mechanisms Staining from Weep Holes Staining can be caused by water draining from weep holes. Salts in concrete and mortar can cause unsightly stains. This is not a deficiency in the masonry unit properties. This is not efflorescence. 13 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Masonry Durability Deterioration Mechanisms Dimensional Changes All masonry units undergo some long-term movements (heat/fire/humidity/creep). If not provided for, expansion and shrinkage can cause severe building distress. Clay units expand over a long time, while Concrete and calcium silicate units shrink over a relatively short time comparatively. The relevant unit property is expressed as a coefficient of expansion or contraction. Movements are accommodated by control Over-sailing and Spalling Caused by joints, spaced according to the masonry Brick Expansion properties. 14 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Masonry Durability Deterioration Mechanisms Distress caused by brick expansion Control Joint Closure by Brick Expansion 15 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  5 Minute Break ‘Paper Bag’ Building – Sydney (Frank Gehry) 16 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Structural Masonry Design Properties of Structural Masonry Design for Compression The diagram shows a cross-section of a typical load-bearing masonry building, with floor slabs framing into masonry walls. A frame analysis can be carried out, assuming pinned ends one level away from the wall being analysed. If wall/slab junctions are assumed to be rigid, then the result of the frame analysis gives moments in the walls, which are converted to equivalent eccentricities. Walls can be bent in either single or double curvature. 17 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Structural Masonry Design Properties of Structural Masonry Design for Compression Comp. Load capacity depends on: Wall slenderness, Effective eccentricity at the ends, Characteristic compressive strength, Cross-sectional area (Bond Type), NOTE: Effective eccentricity is derived from simultaneous compressive load and bending moments. 18 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Structural Masonry Design Properties of Structural Masonry Design for Flexure Lateral load governs for most masonry walls in Australian buildings (i.e. it will fail by flexure before any other mode). Design methods have been an issue worldwide for at least 30 years since behaviour is still not completely understood. Should design so that capacity of the wall (resistance) is higher than the potential bending stresses (either vertical, or horizontal, or both). Resistance to flexure depends mainly on: f’mt = The characteristic flexural tensile strength; Zd = The section modulus of the bedded area; and fd = The compressive stress due to vertical load. 19 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Structural Masonry Design Properties of Structural Masonry Design for Flexure Vertical Bending: Horizontal Bending: Simple spanning between top and bottom Sections of wall supported only at the sides supports results in elastic brittle behaviour resist lateral load by horizontal bending. The stress-strain relationship is linear until failure. A typical load-deflection plot shows distinct Dangerous Failure Mode as – failure then takes changes of slope as cracks develop in the place suddenly. perpend joints (somewhat easy to see). 20 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Structural Masonry Design Properties of Structural Masonry Design for Shear Overturning; Overall sliding or Local failure can all lead to Shear failure within the wall caused by principal tensile stresses causing cracking. In addition, Compression at the toe causes crushing and spalling. Remember that shear capacity is a combination of shear bond strength and shear friction strength (which in turn is directly proportional to a shear factor). 21 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Structural Masonry Design Properties of Structural Masonry Design for Shear Shear Factors. Slippage (over the damp proof courses or flashing) can occur readily under earthquake loading and helps to dissipate energy 22 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Construction and Compliance Considerations and Standard Practice Common Types of Wall Construction Brick – Veneer: Non-structural cladding relies on the frame for support. The frame transfers overall building forces to the footings. Wall ties transfer forces to the supporting frame. Masonry veneer and connections must resist local out-of-plane wind and earthquake loads. 23 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Construction and Compliance Considerations and Standard Practice Common Types of Wall Construction Cavity Wall: Two leaves with typically 50mm drained cavity to exclude water from the building. Good thermal and strength properties with no need for an external coating. Resistance to lateral load relies on interaction between the leaves through the wall ties. 24 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Construction and Compliance Considerations and Standard Practice Joints Bedding must be as specified (full or face-shell). Joint thickness is usually 10 mm but some variation is acceptable (+- 1mm). Vertical joints (perpends) must be filled unless otherwise specified. Joints must be finished as specified - tooling is highly beneficial in improving durability. Control joints must be kept clean and back-filled with sealant as specified. 25 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Construction and Compliance Considerations and Standard Practice Damp Proof Courses (DPC) and Flashing DPC should preferably be embedded in a mortar joint, not laid directly on the units. Joints must be lapped to a length equal to the leaf thickness, taking care not to puncture the DPC or flashing. DPC must project from the wall and be turned down or cut off flush to avoid passage of moisture. The insert in the middle photo is both a flashing and damp-proof course. On the left, it is not lapped correctly at the corner, leading to dampness problems. On the right, it is correctly located, extending beyond the face of the brickwork. 26 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Construction and Compliance Considerations and Standard Practice General Recommendations for Compliance Wall ties and accessories must be built-in as the work proceeds, not inserted later! Set horizontal or sloping outwards to prevent water transfer across the cavity (but not more than 10 mm). Rate of construction must be controlled to suit the conditions! Too rapid construction can lead to masonry slumping. Excessively hot and dry or freezing conditions should be avoided. Cavities and weep-holes must be kept free of mortar and other materials. 27 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Construction and Compliance Considerations and Standard Practice Cleaning Cleaning is essential and is best carried out each day during construction with water and a stiff brush. High pressure cleaners can damage joints and masonry units and must be used with care. Clay smears can be removed with household detergent or will eventually fade. 28 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Construction and Compliance Considerations and Standard Practice Typical Details: Masonry Veneer Walls Base: Roof: 29 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Construction and Compliance Considerations and Standard Practice Typical Details: Cavity Walls Base: Roof: 30 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Construction and Compliance Considerations and Standard Practice Common Faults – Poorly filled Joints 31 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Construction and Compliance Considerations and Standard Practice Common Faults – Poor Bonding at Joints Common Faults – Clogged Weephole and Control Joint 32 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Construction and Compliance Considerations and Standard Practice Common Faults – Excessive Cavity and Inadequate Embedment 33 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Construction and Compliance Considerations and Standard Practice Common Faults – Mortar on Wall Ties Common Faults – Ties Bent Up and Not Engaged 34 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Construction and Compliance Considerations and Standard Practice Master Level of Craftsmanship - Malbork Castle (Poland) The castle is a classic example of a medieval fortress, and is the world’s largest brick gothic castle. 35 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR  Discussion Have any questions?! 36 | CIVL2240 Civil Engineering Materials | The University of Newcastle www.newcastle.edu.au/CIPAR