CSE30310 Lecture .pdf thehongkongpolytechnicuniversity
- 1. Lecture 1: Introduction CSE 30310 Design of Concrete Structures Dr Muhammad Riaz Ahmad mriazahmad@poly.edu.hk Department of Civil and Environmental Engineering The Hong Kong Polytechnic University 1
- 3. Prof Yuner Huang (Subject Lecturer) 3 Work Experience Associate Professor (2025-present), PolyU, Hong Kong Honorary Lecturer (2025-present), University of Edinburgh, UK Senior Lecturer (2022-2024), University of Edinburgh, UK Lecturer (2015-2022), University of Edinburgh, UK Education BEng & Ph.D. in Civil Engineering (2009, 2013), University of Hong Kong Professional Membership Member, Institution of Civil Engineers (CEng MICE) Member, American Society of Mechanical Engineers (MASME) Fellow, Higher Education Academy (FHEA) Hometown Foshan - hometown of ceramic art, Cantonese opera, and martial arts Yuner.huang@polyu.edu.hk, ZS931
- 4. Dr. Riaz (Subject Lecturer) 4 Work Experience Research Assistant Professor (2023-present), PolyU, Hong Kong Visiting Researcher (2022-2023), University of Tokyo, Japan Post-Doctorate Fellow (2021-2023), PolyU, Hong Kong Education Ph.D, Civil Engineering (2021), Shanghai Jiao Tong University, BSc & MSc in Civil Engineering (2013, 2017), UET Lahore, Contact Information: Z407A, (mriaz.ahmad@polyu.edu.hk) More information at
- 5. 5 Contact information for Tutors Mr Chen WU (Tutorials in Week 7 & 9; Assignment 2) Dr Qiuyun LI (Tutorials in Week 11 & 13; Assignment 2) Miss Peilin LI (Tutorials in Week 3 & 5; Assignment 1) peilin.li@connect.polyu.hk 24093915r@connect.polyu.hk qiuyun.li@polyu.edu.hk Dr Yazan ALREFAEI (Laboratory) yazan.alrefaei@polyu.edu.hk
- 6. 6 1. Acquire basic knowledge on the design concepts and detailing techniques of the slabs, beams, columns, walls & foundations of reinforced concrete structures; 2. Understand the basic design principles of prestressed concrete beams; 3. Carry out practical design of concrete elements according to code requirement & communicate logically and lucidly through construction drawings and calculations; Learning outcomes
- 7. 7 4. Appreciate the performance of concrete structures through design calculations and lab tests and understand the limitations of design assumptions through the lab tests; 5. Recognize the need for, and to engage in life-long learning Learning outcomes (Cont.)
- 8. 8 1. Course work 30% including • Assignments (10%) • Quiz and Mid-term test (10%) • Lab Report (5%) • Seminar Report (5%) 2. Examination (Final examination 70%) Note: Student must attain at least Grade D in both course work and examination in order to pass the course as a whole. Late submission is not allowed. Assessment methods
- 9. 9 Teaching Activities Detailed timetable can be found in Teaching Plan (Read carefully! Note the Public Holiday arrangement in W11 & 13)
- 11. 11 Teaching Activities Attending lectures, tutorials & labs are CRUCIAL for getting good scores in this course. Directly impact your course enrolment in Design Project for Civil Engineering in year 4 as part of pre-requisites, and thus your graduation. We will take attendance in lectures & tutorials (submit handwritten worksheets in person during tutorial).
- 12. 12 1. Introduction 2. Structural Systems 3. Loads in Structural systems 4. Properties of Reinforced Concrete 5. Types of Concrete
- 14. 14 Introduction Construction Materials Various substances or products used in the building and construction industry to create structures and infrastructure. Concrete is the most widely used construction material globally. Worldwide cement production (2016)
- 16. 16 Introduction Plain Cement Concrete (PCC) Mixture of cement , sand and coarse aggregate without any reinforcement is known as PCC. PCC is strong in compression and week in tension. Its tensile strength is so small that it can be neglected in design. No Steel Reinforcement in PCC
- 17. 17 Introduction Reinforced Cement Concrete (RCC) Mixture of cement , sand and coarse aggregate with reinforcement is known as RCC. (Tensile strength is improved) Steel Reinforcement in RCC
- 18. 18 Introduction Supplementary Cementitious Materials (SCMs): SCMs are materials used as a partial replacement of portland cement to improve both fresh and hardened concrete properties. SCMs SCMs can be from natural sources or industrial byproducts and have lower environmental impact than Portland cement. Types of SCMs • Fly ash • Slag • Calcined Clay • Silica Fume
- 19. 19 Introduction Why we need Reinforcement in concrete? Plain cement concrete is strong in compression and weak in tension. This means that while it can withstand heavy loads pressing down on it, it is not as effective at resisting forces that try to pull it apart or bend it.
- 20. 20 Introduction Why we need Reinforced cement concrete? Plane cement concrete is weak in tension 1. Tensile Strength 2. Crack Control 3. Ductility 4. Load Distribution 5. Durability 6. Structural Integrity Advantages of reinforcement Reinforced cement concrete is provide additional tensile strength
- 21. 21 Introduction
- 22. 22 Easa, S.M.; Yan, W.Y. Performance-Based Analysis in Civil Engineering: Overview of Applications. Infrastructures 2019, 4, 28. https://doi.org/10.3390/infrastructures4020028 Introduction (Civil Engineering Infrastructures) Buildings Bridges Dams
- 23. 23 Easa, S.M.; Yan, W.Y. Performance-Based Analysis in Civil Engineering: Overview of Applications. Infrastructures 2019, 4, 28. https://doi.org/10.3390/infrastructures4020028 Introduction (Civil Engineering Infrastructures) Tunnels Roads/Pavements
- 24. Concrete structures are the foundation of modern civilization. They are extensively used in buildings, bridges, roads, dams, floating structure, and tunnels. Burj Khalifa, 828 m Three Gorges Dam, 181 m Hong Kong-Zhuhai-Macao Bridge US Highway 1 Floating Ports and Villas The Lærdal Tunnel (a) Buildings (b) Bridges (c) Road/highways (d) Dams (e) Floating structures (f) Tunnels 24 Introduction (Civil Engineering Infrastructures)
- 25. 25 Introduction (Failure in RCC structures) Collapse of a bridge Building collapse
- 26. 26 Failure of Beam-Column Joints Collapse of whole buildings Introduction (Failure in RCC structures) Corrosion in buildings
- 27. 27 Si-Chuan Earthquake (2008), 150 B USD, Casualities (88,708) Turkey Earthquake (2023) (34 B USD, Casualities 59,259) Tohoku Earthquake (2023), 360 B USD, Casualities 19,759 ) Pakistan Flood (2010) 50 B USD , Casualities 2,000, 33 m people effected Introduction (Natural Disaster)
- 28. 28 Building Collapse（Hong Kong） (29-01-2010） Introduction
- 29. 29 What are the reasons for RCC structure failures? Introduction
- 30. 30 How to achieve a safe design of RC structures? What are the reasons for RCC structure failures? Introduction 1. Design Errors 2. Poor Construction Practices 3. Material Deficiencies 4. Corrosion of Reinforcement 5. Overloading 6. Environmental Factors 7. Lack of Maintenance 8. Foundation Issues 9. Fatigue and Wear
- 31. 31 2. Overview of structural systems
- 32. 32 Reinforced concrete building elements Basic structural systems Primary functions of building systems is to support gravity loads for strength and serviceability during: 1. Normal use (service) conditions; (regular occupancy and use of the structure on day-to-day basis) 2. Maximum considered use condition; (during events such as concerts or gatherings e.g, stadiums) 3. Environmental loading of varying intensities. (wind, snow, seismic activity)
- 33. 33 Load Transfer mechanism Basic structural systems Function of structure is to transfer all the loads safely to ground. A particular structural member transfers load to other structural member.
- 34. Vertical deflection (sag) Lateral deflection (sway) Dead, imposed etc. Wind, earthquake 34 Deflections Basic structural systems
- 35. 35 Beam element Defn: Members subject to bending and shear V V L E,I,A M M Basic structural systems Column element Defn: Members subject to bending, shear, and axial V V L E,I,A M M F F
- 36. 36 Slab/plate element Defn: Members subject to bi-directional bending & shear Basic structural systems One-way Slab Two-way Slab
- 37. 37 Wall/diaphragm element Defn: Members subject to shear Basic structural systems Shear wall subjected to lateral loads German Cast In Situ Technology, precast technology Hyderabad - Janapriya.com
- 38. 38 Floor system: Flat plate Flat slab (w/ drop panels and/or capitals) One-way joist system Two-way waffle system Lateral load system: • Flat plate (& slab)-column (w and w/o drop panels and/or capitals) frame systems • Beam-column frame systems • Shear wall systems (building frame and bearing wall) • Dual systems (frame and shear walls) Structural systems Basic structural systems
- 39. 39 Flat Plate Floor System Flat Plate w/Spandrel Beam Floor System Basic structural systems Floor systems Beam-slab system
- 40. 40 One way-joist floor system Flat slab floor system Elevation Plan Basic structural systems
- 41. 41 Waffle slab floor system Basic structural systems Waffle slab floor system, PolyU
- 42. 42 Frame: Coplanar or a non-coplanar system of beam (or slab) and column elements dominated by flexural deformation Gravity Load Lateral Loading Basic structural systems
- 43. 43 Basic structural systems One-way slab system two-way slab system
- 44. 44 Frame lateral load systems Basic structural systems Flat plate systems are normally less effective in resisting the lateral load system. A wider slab provides additional stiffness and rigidity to the system, which can enhance its resistance to lateral load and also increase torsional resistance of structure.
- 45. 45 Shear wall lateral load systems Basic structural systems Dual lateral load systems In frame lateral load systems, the lateral load resistance can be enhanced by configuring elevator shaft or by providing shear walls within the structure. They provide additional stiffness and strength to resist lateral forces and can enhance the lateral resistance of the lateral load system.
- 46. 46 4. Loads in structural systems
- 47. 47 Gravity: 1. Dead; 2. Imposed; 3. Impact; 4. Snow; 5. Ice; 6. Rain/floods. ……. Lateral: 1. Wind; 2. Earthquake; 3. Soil lateral pressure; 4. Thermal; 5. Centrifugal. …… Types of loads Loads in structural systems
- 48. 48 Loads in structural systems Loads
- 49. 49 Definition of characteristic load Loads in structural systems ‘Characteristic load’ means that load which has a 95% probability of not being exceeded, during the life of the structure. Using Characteristic Load in Design 1. Determining the Characteristic Load: 2. Applying Load Factors: 3. Calculating the Design Load: 4. Structural Analysis and Design:
- 50. 50 5. Properties of Reinforced Concrete
- 51. 51 Properties of concrete •The first portion of curve, to about 40% of the ultimate strength fc’, can be considered linear fc’ 0.85fc’ Stress Strain Crushing 0.0028 to 0.0045, generally 0.0035 0.4 fc’ Stress Strain Curve of Concrete
- 52. 52 EC = (1.25Ecq -19) kN/mm2 Properties of concrete Modulus of Elasticity Concrete is not an elastic material therefore it does not have a fixed value of modulus of elasticity Strain Tangent and Secant Moduli of Concrete Stress Secant or static Modulus (Ec) Tangent Modulus Initial tangent Modulus (Ecq)
- 53. 53 Properties of concrete Characteristic strength of concrete Characteristic strength is defined as that level of strength below which a specified proportion of all valid test results is expected to fail. Unless otherwise stated, this proportion is taken to be 5%.
- 54. 54 Properties of concrete Development of concrete strength
- 55. 55 Reinforcing steel bars Properties of steel Steel bars are: Plain Deformed (currently in use) Deformed bars have longitudinal and transverse ribs. Ribs provide a good bond between steel and concrete. If this bond fails steel becomes in effective. The most important properties for reinforcing steel are: Young's modulus, E Yield strength, fy Ultimate strength, fu Size and diameter of bar
- 56. 56 Reinforcing steel characteristics Stress-strain curves for reinforcing steel 0.002 Strain Stress Proof stress Strain Stress Yield stress (a) Hot rolled steel (Mild steel) (b) Cold worked steel (High-yield steel) Properties of steel The characteristics of steel are 1. Mild steel behaves as an elastic material, with the strain proportional to the stress up to the yield, at which point there is a sudden increase in strain with no change in stress. After the yield point, this becomes a plastic material, and the strain increases rapidly up to the ultimate value. 2. High yield steel may behave in a similar manner or may, on the other hand, not have such a definite yield point but may show a more gradual change from elastic to plastic behaviour and reduced ductility depending on the manufacturing process. All materials have a similar slope of the elastic region with elastic modulus Es=200 kN/mm2 approximately. Amount of stress that will result in a plastic strain of 0.2%
- 57. 57 Short-term design stress-strain curve for steel reinforcement (HK2013) Properties of steel Strain Grade 250 Grade 500 Stre ss For hot rolled steel bars
- 58. 58 Properties of reinforced concrete (Shrinkage) Excessive shrinkage can be avoided by proper curing during first 28 days because half of the total shrinkage takes place during this period. Shrinkage is reduction in volume of concrete due to loss of water
- 59. 59 Properties of reinforced concrete (Shrinkage) Calculate Shrinkage Stresses in Concrete for (a) Restrained by reinforcement only (b) Fully Restrained
- 60. 60 Reinforcement restrains shrinkage movement and generate tension in concrete Properties of concrete Concrete creep and shrinkage calculator - Strusoft When cracking occurs, the uncracked lengths of concrete try to contract so that the embedded steel between cracks is in compression while the steel across the cracks is in tension. This feature is accompanied by localised bond breakdown, adjacent to each crack.
- 61. 61 Development of creep deformation with time affects deflections and crack widths Properties of concrete “Creep is the continuous deformation of material over considerable lengths of time at constant stress or load” The characteristics of creep are 1. The final deformation of the member can be three to four times the short-term elastic deformation. 2. The deformation is roughly proportional to the load intensity and to the inverse of concrete strength. 3. If the load is removed, only the elastic deformation will recover – the plastic deformation will not. 4. There is a redistribution of load between the concrete and any steel present
- 62. 62 6. Advantages and Disadvantages of Reinforced Concrete
- 63. 63 Suitability of material for architectural and structural function ◦ Concrete place in plastic condition - desired shape & texture can be obtained with forms and finishing techniques. ◦ Designer can choose shape and size. Fire Resistance: Concrete building have 1-3 hour fire rating with no fire proofing (steel and timber require fireproofing to obtain this rating) Rigidity: Greater stiffness & mass reduces oscillations (wind), floor vibrations (walking) Low Maintenance Availability of Materials: Sand, gravel, cement, water & concrete mixing facilities widely available; Reinforcement - easy to transport as compared to structural steel Good bonding between the steel and concrete Less chance of buckling Advantages of Reinforced Concrete
- 64. 64 Low tensile strength -0.1 fc; cracking if not properly reinforced. Forms and Shoring (additional steps). ◦ Construction of forms; Removal of forms; Prepping (or shoring) the new concrete to support weight until strength is adequate; Labor/Materials cost not required for other types of materials. Strength per unit volume is relatively low. ◦ fc ~ (5-10% of steel); greater volume required. Time-dependent volume changes. ◦ Concrete undergoes drying shrinkage, which may cause deflections and cracking. ◦ Creep of concrete under sustained loads causes an increase in deflection with time. Increased self weight large cross-section is required only to resist self weight, making structure costly Disadvantages of Reinforced Concrete
- 65. 65 7. Types of Concrete
- 66. 66 • Ready-mixed concrete • High-performance concrete • Self-compacting concrete • Roller-compacted concrete • Structural lightweight concrete • Fiber-reinforced concrete • Engineering cementitious composites • Polymer concrete • Shotcrete • Internal curing concrete • Self healing concrete • Self cleaning concrete • Recycled concrete • Autoclaved cellular concrete • Geopolymer • Seawater sea-sand concrete • 3D printing concrete Types of concrete
- 67. 67 ✓ SCC is a highly workable concrete that can flow through densely reinforced and complex structural elements under its own weight and adequately fill all voids without segregation, excessive bleeding, excessive air migration, and the need for vibration or other mechanical consolidation. ✓ The highly flowable nature of SCC is due to very careful mix proportioning, usually replacing much of the coarse aggregate with fines and cement, and adding chemical admixtures. https://youtu.be/M38gamAlxt0 Self-compacting concrete (SCC)
- 68. 68 ✓ Fibres are added to concrete to control cracking caused by plastic shrinkage and drying shrinkage. ✓ The addition of small closely spaced and uniformly dispersed fibres will act as crack arresters and enhance the tensile, fatigue, impact, and abrasion resistance of concrete. They also reduce the permeability of concrete. ✓ Though the flexural strength may increase marginally, fibres cannot totally replace flexural steel reinforcement. Fiber-reinforced concrete
- 69. 69 ✓ ECC are a special type of high-performance fiber reinforcement cementitious composites (HPFRCC) that has been micro-structurally tailored based on micro-mechanics. ✓ ECC is systematically engineered to achieve high ductility under tensile and shear loading. ✓ By employing material design based on micro-mechanics, it can achieve maximum ductility in excess of three per cent under uniaxial tensile loading with only two per cent fibre content by volume. Engineered cementitious composites
- 70. 70 3D printing concrete 3D printing is revolutionary technology, that allows for the faster fabrication of custom- designed and complex concrete structures. The process of concrete printing is completed layer-by-layer and controlled by the blueprints or digital models from a computer.