Structure for Architects - I PDF Lecture Notes

Structure for Architects - I COURSE CODE: CE-251 © Muhammad Saad Ifrahim (NED University of Engineering and INSTRUCTOR INTRODU...

Structure for Architects - I COURSE CODE: CE-251 © Muhammad Saad Ifrahim (NED University of Engineering and INSTRUCTOR INTRODUCTION Name: Engr. Muhammad Saad Ifrahim Education: BE (CIVIL), ME (STRUCTURE) Teaching/Research Experience: 3+ Years Email: [email protected] “Welcome to our Structure for Architects course! I'm thrilled to have you join us as we explore the principles of structural behavior and the role of architects in designing and collaborating on building projects” © Muhammad Saad Ifrahim (NED University of Engineering and 2  cogito, ergo sum (I think, therefore I am) René Descartes © Muhammad Saad Ifrahim (NED University of Engineering and © Muhammad Saad Ifrahim (NED University of Engineering and Recommended Books © Muhammad Saad Ifrahim (NED University of Engineering and 5 Evaluation & Assessment Sessional (40) Final Paper (60) Assignment 04/05 Questions Mid-Term Test Covering all Quizzes Class Learning Outcomes © Muhammad Saad Ifrahim (NED University of Engineering and 6 © Muhammad Saad Ifrahim (NED University of Engineering and The design of this rocket and gantry structure requires the basic knowledge of statics and dynamics © Muhammad Saad Ifrahim (NED University of Engineering and Why do students of architecture study structures? Architects should be capable of designing simple structural members (e.g., timber joists for floors) with basic training. On larger projects, architects work in interdisciplinary teams that usually include structural engineers, making it important to understand their role, language, and terms. Always ask yourself the question: ‘How will my building standup?’ Remember – if you have difficulty in getting your model to stand up, it is unlikely that the real thing will stand up either! © Muhammad Saad Ifrahim (NED University of Engineering and 9 Structural understanding Any structure must satisfy the following criteria: The basic function of a structure is to transmit Aesthetics loads from the position of application of the load to the point of support and thus to the foundations in the ground. Economical Ease of Maintenance Durability Fire resistance © Muhammad Saad Ifrahim (NED University of Engineering and 10 Safety and serviceability There are two main requirements of any structure: it must be safe A structure must carry the expected loads without collapsing it must be serviceable. A structure must be designed in such a way that it doesn’t deflect or crack unduly in use. © Muhammad Saad Ifrahim (NED University of Engineering and 11 BASIC CONCEPTS States of stress Tension Compression Shear Torsion Bending Strength, Stiffness & Stability © Muhammad Saad Ifrahim (NED University of Engineering and 12 What is stress & strain? We use the terms stress and strain in everyday life in circumstances unconnected with structures. Stressful situation Reaction It’s the same principle in structural engineering. © Muhammad Saad Ifrahim (NED University of Engineering and 13 What is stress & strain? Forces are trying to compress, or squash, the column The column will react to this ‘squashing’ stress by allowing itself to be reduced in length. This reduction in length (as a proportion of the column’s original length) is the strain. © Muhammad Saad Ifrahim (NED University of Engineering and 14 What is stress & strain? © Muhammad Saad Ifrahim (NED University of Engineering and 15 What is stress & strain? © Muhammad Saad Ifrahim (NED University of Engineering and 16 Quantifying normal stresses 1. Our calculations are based on the assumption that a structure is in equilibrium 2. That also means every part of the structure is in equilibrium 3. Cut sections and apply the equilibrium equation(s): 𝜮𝑭𝒙=𝟎; 𝜮𝑭y=𝟎 4. Once the object is in equilibrium, find out the stress using the formula: 𝜎 = 𝑃/𝐴 © Muhammad Saad Ifrahim (NED University of Engineering and 17 Relationship between stress and strain A steel tie in a space frame roof structure is originally 2 metres long. If the tie is a solid bar of diameter 40 mm, calculate the extension of the steel bar that would be expected if a tensile force of 150 kN is applied to the bar. The Young’s Modulus of steel is 205 kN/mm2. If the extension was unacceptably large, what steps could you take to reduce it? © Muhammad Saad Ifrahim (NED University of Engineering and 18 Who was Mr Hooke? Robert Hooke was also an He assisted Sir Christopher Wren on the rebuilding of architect !!! London’s St Paul’s Cathedral after the Great Fire of 1666. © Muhammad Saad Ifrahim (NED University of Engineering and 19 Shear stress You wouldn’t be able to slice a piece of bread without holding the loaf in place with your other hand (which provides the opposing force) at the same time. © Muhammad Saad Ifrahim (NED University of Engineering and 20 Shear stress © Muhammad Saad Ifrahim (NED University of Engineering and 21 Torsion Torsion is referred to twisting of an element. Twisting is a result of Torque. Twisting is different from Bending which is caused by Moment. © Muhammad Saad Ifrahim (NED University of Engineering and 22 Torsion Torsion Axial Normal Stress τ =Gγ τ is the shear stress G is the Shear Modulus/Modulus of Rigidity γ is the Shear strain © Muhammad Saad Ifrahim (NED University of Engineering and 23 Torsion © Muhammad Saad Ifrahim (NED University of Engineering and 24 Torsion © Muhammad Saad Ifrahim (NED University of Engineering and 25 Torsion – Examples The shaft shown is supported by two bearings and is subjected to three torques. Determine the shear stress developed at points A and B, located at section a-a of the shaft. © Muhammad Saad Ifrahim (NED University of Engineering and 26 Torsion – Examples 42.5-30-T=0 T=12.5 kip-in © Muhammad Saad Ifrahim (NED University of Engineering and 27 Bending © Muhammad Saad Ifrahim (NED University of Engineering and 28 Bending © Muhammad Saad Ifrahim (NED University of Engineering and 29 Strength X-ray of a broken bone © Muhammad Saad Ifrahim (NED University of Engineering and 30 Strength There is a limit to the stress any particular material can take. This stress is known as the permissible stress or the strength of the material. Timber is typically in the range 4–7 N/mm2 The strength of concrete is typically in the range 25–40 N/mm2 The strength of the steel type normally used in structural steelwork construction is 275 N/mm2 © Muhammad Saad Ifrahim (NED University of Engineering and 31 Strength – Examples If the cylinder shown is made of steel (Strength= 40 ksi), the diameter of the cylinder is 2 inches, and the load applied, P= 100 kips determine (a) Whether the cylinder material has failed or not (b) What is the minimum load required for the material failure of the cylinder. © Muhammad Saad Ifrahim (NED University of Engineering and 32 Stiffness “Stiffness, or rigidity, is not to be confused with strength” Some strong materials are not stiff (e.g. rope) and some stiff materials are not particularly strong (e.g. glass). The stiffer a material, the less it will deflect. The stiffness of a material is proportional to its Young’s Modulus value © Muhammad Saad Ifrahim (NED University of Engineering and 33 Stability of structure All structures must be stable, otherwise they may collapse. Being strong is not sufficient. Internal Hinge © Muhammad Saad Ifrahim (NED University of Engineering and 34 Stability of structure © Muhammad Saad Ifrahim (NED University of Engineering and 35 Stability of structure © Muhammad Saad Ifrahim (NED University of Engineering and 36 Stability of structure In practice, the stability of a structure is assured in one of three ways: Shear walls/stiff core. Cross-bracing. Rigid joints. © Muhammad Saad Ifrahim (NED University of Engineering and 37  Stability of structure We could design each individual column to resist the wind forces, but for various reasons this is not the way it is normally done. Instead, shear walls are used. These walls are designed to be stiff and strong enough to resist all the lateral forces on the building. Location Staircase Lift Shaft It is obviously important that the building doesn’t Corner of building collapse in the manner of a ‘house of cards’ under the effects of this horizontal wind force. © Muhammad Saad Ifrahim (NED University of Engineering and 38 Stability of structure © Muhammad Saad Ifrahim (NED University of Engineering and 39 Stability of structure One way of ensuring stability is to stop the ‘squares’ in the building elevation from becoming trapeziums Diagonal cross-bracing is used to ensure stability © Muhammad Saad Ifrahim (NED University of Engineering and 40 Stability of structure A third method of providing lateral stability is simply to make the joints strong and stiff enough that movement of the beams relative to the columns is not possible. © Muhammad Saad Ifrahim (NED University of Engineering and 41  meow !!! © Muhammad Saad Ifrahim (NED University of Engineering and 42 Loading on structure In structures, there are the following different types of loading: Types of loading Dead load Live load Wind load Earth pressure Other load Water pressure Earthquake © Muhammad Saad Ifrahim (NED University of Engineering and 43  Loading on structure: Dead load 2018 International Building Code | Chapter 2 Section 202: Formal Definition of Dead Loads | Chapter 16 Section 1606: Dead Loads American Society of Civil Engineers (ASCE) Standard 7-10 | Minimum Design Loads for Buildings and Other Structures: Table C3-1, Table C3-2 Eurocode (EN) 1991-1-1:2002 | Actions on Structures: Section 5: Self-Weight of Construction Works | Annex A These items – and their weights – are obviously always there, 24 hours a day, 365 days a year. © Muhammad Saad Ifrahim (NED University of Engineering and 44 Loading on structure: Live load Live loads, unlike dead loads, are variable. Examples of live load include people and 300-seat cinema auditorium would be full of people furniture. Other examples include snow loads on a Saturday evening if a major new blockbuster on roofs. movie was being shown, but it might be only a quarter full on a weekday afternoon. © Muhammad Saad Ifrahim (NED University of Engineering and 45 Loading on structure: Wind load Wind loads vary across the country and across the world and their effects vary according to the type of physical environment and the height of the building. © Muhammad Saad Ifrahim (NED University of Engineering and 46 Loading on structure: Wind load Uplift can develop when wind blows across a roof. © Muhammad Saad Ifrahim (NED University of Engineering and 47 Can you identify loadings in this view from Nathiagali? © Muhammad Saad Ifrahim (NED University of Engineering and 48 Nature of load © Muhammad Saad Ifrahim (NED University of Engineering and 49 Types of Beams (Based on Supports) © Muhammad Saad Ifrahim (NED University of Engineering and 50 Types of Beams (Based on Cross-section and Material) © Muhammad Saad Ifrahim (NED University of Engineering and 51 Statically Determinate and Indeterminate Beams © Muhammad Saad Ifrahim (NED University of Engineering and 52 Sectional Properties of Beam © Muhammad Saad Ifrahim (NED University of Engineering and 53 Sectional Properties of Beam © Muhammad Saad Ifrahim (NED University of Engineering and 54 Sectional Properties of Beam After Applying Parallel Axis Theorem © Muhammad Saad Ifrahim (NED University of Engineering and 55 Sectional Properties of Beam © Muhammad Saad Ifrahim (NED University of Engineering and 56 Theory of Simple Bending © Muhammad Saad Ifrahim (NED University of Engineering and 57 Theory of Simple Bending © Muhammad Saad Ifrahim (NED University of Engineering and 58 Theory of Simple Bending Assumptions of Bending Theory: 1. The material is linearly elastic 2. Young’s Modulus (E) is the same in compression and tension. 3. Material is homogeneous (i.e. the same throughout). 4. Plane sections remain plane after bending © Muhammad Saad Ifrahim (NED University of Engineering and 59 Example © Muhammad Saad Ifrahim (NED University of Engineering and 60 Deformation in Beams © Muhammad Saad Ifrahim (NED University of Engineering and 61 Analysis of Structure: Finding Reactions © Muhammad Saad Ifrahim (NED University of Engineering and 62 Analysis of Structure: Bending Moment and Shear force Diagram 1 2 3 1 2 3 © Muhammad Saad Ifrahim (NED University of Engineering and 63 How bending failure looks like? © Muhammad Saad Ifrahim (NED University of Engineering and 64 How shear failure looks like? © Muhammad Saad Ifrahim (NED University of Engineering and 65 Analysis of Structure: Bending Moment and Shear force Diagram 1 2 3 1 2 3 © Muhammad Saad Ifrahim (NED University of Engineering and 66 Analysis of Structure: Bending Moment & Shear force Diagram © Muhammad Saad Ifrahim (NED University of Engineering and 67 Cantilever beams The cantilever allows a café area on an upper level to overhang. Note how the depth of the supporting beam reduces towards the ‘free’ (i.e. unsupported) end. o This is because the bending moment in the beam also reduces towards the free end cantilever in a shopping center in Germany. © Muhammad Saad Ifrahim (NED University of Engineering and 68 Class Activity Draw a shear force diagram and bending moment diagram for the following beam, along with its deflected shape. © Muhammad Saad Ifrahim (NED University of Engineering and 69 How to conduct research using modern day tools? © Muhammad Saad Ifrahim (NED University of Engineering and 70 How to conduct research using modern day tools? © Muhammad Saad Ifrahim (NED University of Engineering and 71 How to conduct research using modern day tools? © Muhammad Saad Ifrahim (NED University of Engineering and 72 How to conduct research using modern day tools? © Muhammad Saad Ifrahim (NED University of Engineering and 73 How to conduct research using modern day tools? © Muhammad Saad Ifrahim (NED University of Engineering and 74 Approximate analysis of statically indeterminate structures © Muhammad Saad Ifrahim (NED University of Engineering and 75 Approximate analysis of statically indeterminate structures © Muhammad Saad Ifrahim (NED University of Engineering and 76  Concrete Constituents Cement is essential for concrete as it transforms a non-cohesive mixture into a solid mass – It’s a binder. The reactions leading to hardening are known as hydration. Key compounds from cement hydration: - Calcium silicate hydrates (C-S-H) provide main strength. - Calcium hydroxides (CH). Smaller amounts of: - Calcium aluminate hydrates (C-A-H). - Calcium aluminium sulphates (ettringite). W/C ratio plays an integral part in deciding the strength of concrete © Muhammad Saad Ifrahim (NED University of Engineering and 77 Concrete Close up view: Heterogenous Material Cement Matrix Coarse Agg Fine Agg © Muhammad Saad Ifrahim (NED University of Engineering and 78 Behaviour of Concrete under Compression and Tension Concrete is strong in compression while weak in tension Increase in Shortening length in length 79 Impact of W/C ratio and curing on concrete Concrete gains strength with time subjected to proper curing W/C ratio impacts on strength of concrete © Muhammad Saad Ifrahim (NED University of Engineering and 80 Phases of Microcracking and Deformation in Concrete Phase 1 (≤30% ultimate strength): Stable microcracking, linear stress-strain. Phase 2 (30-50% ultimate strength): New and growing cracks, existing cracks increase in length and width, non-linear deformation. Phase 3 (50-75% ultimate strength): Significant cracks in mortar and transition zone. Final Phase (75-80%+ ultimate strength): Unstable cracks, potential specimen failure. © Muhammad Saad Ifrahim (NED University of Engineering and 81 Mechanical Properties of steel reinforcement bars © Muhammad Saad Ifrahim (NED University of Engineering and 82 Stress – Strain behaviour of steel rebar © Muhammad Saad Ifrahim (NED University of Engineering and 83 Why concrete needs reinforcement? © Muhammad Saad Ifrahim (NED University of Engineering and 84 How Reinforced Concrete invented? Joseph Monier (1823-1906): French gardener. Problem: Faced issues with traditional garden pots and tubs, which were prone to breaking. Innovation: Experimented with embedding iron mesh into concrete to improve its strength and durability. © Muhammad Saad Ifrahim (NED University of Engineering and 85 Reinforced Concrete Rebar + Concrete Great Team Bond transfers stresses from concrete to steel Rebar takes loads after cracking Concrete protects steel from corrosion Concrete is Alkaline Concrete provides cover to rebar © Muhammad Saad Ifrahim (NED University of Engineering and 86 General Behaviour of RC beam © Muhammad Saad Ifrahim (NED University of Engineering and 87