Steel Timber Design CIEN 20043 PDF

# STEEL TIMBER DESIGN ## CIEN 20043 **Prepared By:** JESECO A. MALOLOS, RCE, TPICQS **Date:** September 2024 ## Term Guides * **Orientation & Introduction** * Course Orientation * Grading System * Requirements * Relevance of the Course * Reading List: Student Handbook * **P...

# STEEL TIMBER DESIGN ## CIEN 20043 **Prepared By:** JESECO A. MALOLOS, RCE, TPICQS **Date:** September 2024 ## Term Guides * **Orientation & Introduction** * Course Orientation * Grading System * Requirements * Relevance of the Course * Reading List: Student Handbook * **Part 1: Introduction and Pre-requisite Topics** * Introduction and prerequisite of the subject * **Part 2: Properties of Steel and Timber** * Advantages and Disadvantages of using Steel as Construction Materials * Advantages and Disadvantages of using Timber as Construction Materials * Types of Structural Steel * Commonly Used Structural Timber * **Part 3: Design and Analysis of Structural Members Using Timber** * Citing NSCP Code Provisions * Application of NSCP Code Provision * Midterm Examination * **Part 4: Design and Analysis of Structural Members Using Steel** * Citing NSCP Code Provisions * Application of NSCP Code Provision * Final Examination ## Rationale This course aims to provide architecture students the basic knowledge, design code provisions, and application of Steel and Timber Design concepts, principles, and theories in order to appreciate its role on their chosen field of specialization. The course shall tackle both design and analysis of structural elements made up of steel and timber. ## Contact Hours: * 3 Units lecture * 3 Hours a week ## Grading Assessment: * Midterm / Final Exams - 50% * Quiz / Assignment / Seatwork - 35% * Reports / Attendance - 15% ## Classroom Management: * 15% ## Introduction Timber and steel structural design may be defined as a mixture of art and science, combining the experienced engineer's intuitive feeling for the behavior of a structure with a sound knowledge of the principles of statics, dynamics, mechanics of materials, and structural analysis, to produce a safe, economical structure that will serve its intended purpose. Until about 1850, structural design was largely an art relying on intuition to determine the size and arrangement of the structural elements. Early man-made structures essentially conformed to those which could also be observed in nature, such as beams and arches. As the principles governing the behavior of structures and structural materials have become better understood, design procedures have become more scientific. Computations involving scientific principles should serve as a guide to decision-making and not be followed blindly. Intuitive ability of the experienced engineer is utilized to make the decisions, guided by the computational results. ## Design Principle Design is a process by which an optimum solution is obtained, concerning the design of structures in particular, steel and timber structures. In any design, certain criteria must be established to evaluate whether or not an optimum has been achieved. For a structure, typical criteria may be: * Minimum cost * Minimum weight * Minimum construction time * Minimum labor cost * Maximum life efficiency Usually several criteria are involved, each of which may require weighing. Observing the above possible criteria, it may be apparent that setting clearly measurable criteria (such as weight and cost) for establishing as optimum frequently will be difficult, and perhaps impossible. In most practical situations, the evaluation must be qualitative and optimization is may be employed to obtain a maximum or minimum function. ## Design Procedure The design procedure may be considered to be composed of two parts: 1. Functional design 2. Structural framework design ### Functional Design Functional design ensures that intended results are achieved, such as**: * Adequate working areas and clearances * Proper ventilation and/or air conditioning * Adequate transportation facilities, such as elevators, stairways, and cranes or materials handling equipment * Adequate lighting * Aesthetics ### Structural Framework Design The structural framework design is the selection of the arrangement and sizes of structural elements so that service loads may be safely carried, and displacements are within acceptable limits. ## Design Procedure (cont.) The iterative design maybe outlined as follows: 1. **Planning:** establishment of the functions which the structure must serve. 2. **Set criteria:** against which to measure the resulting design for being an optimum (optimum means favorable outcome) 3. **Preliminary structural configuration:** Arrangement of the elements to serve the functions in step 1. 4. **Establishment of the loads to be carried.** 5. **Preliminary member selection:** Based on the decisions of steps 1, 2, and 3, selection of the member sizes to satisfy an objective criterion, such as least weight or cost. 6. **Analysis:** Structural analysis involving modeling the loads and the structural framework to obtain internal forces and any desired deflections. 7. **Evaluation:** Are all strength and serviceability requirements satisfied and is the result optimal? Compare the result with predetermined criteria. 8. **Redesign:** Repetition of any part of the sequence 1 through 6 found necessary or desirable as a result of evaluation **(Steps 1 through 6 represent an iterative process. Usually in this text only steps 3 through 6 will be subject to this iteration, since the structural con- figuration and external loading will be prescribed.)** 9. **Final decision:** The determination of whether or not an optimum design has been achieved. 10. **Review of Prerequisites:** * **Module 1:** * *Behavior and Design of Structures* * Physics - Engineering Mechanics Statics * Strength of Materials * Theory of Structures * *Steel and Timber Design* ## Behavior and Design of Structures **Structures:** something made up of interdependent parts in a definite pattern of organization. **Structural Design:** assessing and meeting structural requirements of parts and the whole. **Architectural Structure:** is a man-made construction simultaneously that responds to engineering requirements and aesthetic considerations. **Statics:** Physics of forces and reactions on bodies and system. Deals with the equilibrium of bodies, that is, those that are either at rest or move with a constant velocity. ## Unit of Measurements * **Length:** is used to locate the position of a point in space and thereby describe the size of a physical system. * **Mass** is a measure of a quantity of matter that is used to compare the action of one body with that of another. This property manifests itself as a gravitational attraction between two bodies and provides a measure of the resistance of matter to a change in velocity. * **Force** is considered as a "push" or "pull" exerted by one body on another. This interaction can occur when there is direct contact between the bodies, such as a person pushing on a wall, or it can occur through a distance when the bodies are physically separated. **Concentrated Force:** Represents the effect of a loading which is assumed to act at a point on a body. We can represent a load by a concentrated force, provided the area over which the load is applied is very small compared to the overall size of the body. **Pressure:** The pressure load value (P) is defined in units of force per unit of surface area, thus the total applied force depends on the total area of the face or surface. **Pascal:** Is the unit of pressure or stress. Specifically, a pascal measures the pressure applied by 1 N of force applied on an area of 1 m² at a right angle. **Stress:** The force across a small boundary per unit area of that boundary, the internal forces that neighbouring particle of a continuous material exert on each other. **Gravitational Force:** The pull of a particle or rigid bodies towards the center of the earth with a force proportional to the mass of the object. **Magnitude of Forces:** The number that represents the strength of the force. **Direction of Forces:** Refers to the path or direction along which a force is applied acting along specific line or acting in a specific direction. **Moment of Forces:** A measure of its tendency to cause the object to rotate about a specific point or axis, and is the product of the force and its distance from the point or axis. **Equilibrium:** When all forces or moments acting upon it are balanced. This means that each and every force acting upon a body, or part of the body, is resisted by either another equal and opposite force or set of forces whose net result is zero. ## Mechanics of Materials and Theory of Structures ### Load * **Definition:** * Applied externally, or an inherent part of the structure itself (self-weight). * Is a force, deformation, or acceleration applied to structural elements. * A load causes stress, deformation, and displacement in a structure. * Structural analysis, a discipline in engineering, analyzes the effects of loads on structures and structural elements. * Excess load may cause structural failure, so this should be considered and controlled during the design of a structure. * **Types of Loads:** * Dead Loads * Live Loads * Dynamic Loads (e.g., trains, equipment) * Wind Loads * Earthquake Loads * Thermal Loads * Settlement Loads ### Dead Loads * Weight of the structure itself (floors, beams, roofs, decks, beams/stringers, superstructure) * Loads that are "not moving" ### Live Loads * People, furniture, equipment * Loads that may move or change mass or weight * Minimum design loadings are usually specified in the building code ### Dynamic Loads * Moving loads (e.g., traffic) * Impact loads * Gusts of wind ### Earthquake Loads * Structure loaded when base is shaken * Response of structure is dependent on the frequency of motion * When frequencies match with natural frequency of structure - resonance ## Load Examples ### Earthquake Load ### Live Load in Ballroom ### Water in a Dam ## What are the common causes of Swimming Pool's Architectural and Structural Failures? ## Structural Supports ### Types of Connections * **Cable:** One unknown. The reaction is a tension force which acts away from the member in the direction of the cable. * **Weightless Link:** One unknown. The reaction is a force which acts along the axis of the link. * **Roller:** One unknown. The reaction is a force which acts perpendicular to the surface at the point of contact. * **Rocker:** One unknown. The reaction is a force which acts perpendicular to the surface at the point of contact. ### Number of Unknowns * **Smooth Contacting Surface:** One unknown. The reaction is a force which acts perpendicular to the surface at the point of contact. * **Roller or Pin in Confined Smooth Slot:** One unknown. The reaction is a force which acts perpendicular to the slot. * **Member Pin Connected to Collar on Smooth Rod:** One unknown. The reaction is a force which acts perpendicular to the rod. * **Smooth Pin or Hinge:** Two unknowns. The reactions are two components of force, or the magnitude and direction & of the resultant force. Note that & and @ are not necessarily equal (usually not, unless the rod shown is a link as in (2)). * **Member Fixed Connected to Collar on Smooth Rod:** Two unknowns. The reactions are the couple moment and the force which acts perpendicular to the rod. * **Fixed Support:** Three unknowns. The reactions are the couple moment and the two force components, or the couple moment and the magnitude and direction & of the resultant force. ## Steel Design ### Module Two * Steel Properties and Specification * Steel Advantage and Disadvantages * Properties of Steel Sections * Design and Analysis of Structural Members ## Standard Specification of Steel * AISC * Specification for Structural Steel Building * Steel Construction Manual * ASTM * A6/A6M-14: Standard Specification for General Requirements for Rolled Structural Steel Bars, Plates, Shapes, and Sheet Piling * A36/A36M-14: Standard Specification for Carbon Structural Steel * A53/A53M-12: Standard Specification for Pipe, Steel, Black and Hot-Dipped, Zinc-Coated, Welded and Seamless * A193/A193M-15: Standard Specification for Alloy-Steel and Stainless Steel Bolting Materials for High Temperature or High Pressure Service and Other Special Purpose Applications * A194/A194M-15: Standard Specification for Carbon Steel, Alloy Steel, and Stainless Steel Nuts for Bolts for High Pressure or High Temperature Service, or both * ACI * The Connection of Structural Steel to Concrete Elements ## Steel General Properties and Specification ### Rebars/RSB | PNS 49 Grade | Equivalent Category | Color Code | Grade | Yield Strength | Tensile Strength | Ts/Ys Ratio | Diameters (mm) | Length (meters) | |---|---|---|---|---|---|---|---|---| | Grade 230 | Grade 33 | Regular | White | 230 MPa | 390 MPa | 1.25 min | - | - | | Grade 280 | Grade 40 | Regular | Yellow | 280 MPa | 420 MPa | 1.25 min | - | 6 | | Grade 420 | Grade 60 | Regular | Orange | 420 MPa | 620 MPa | 1.25 min | 10 | 7.5 | | Grade 520 | Grade 75 | Regular | Green | 520 MPa | 690 MPa | 1.25 min | 12 | 9 | | Grade 520 | Grade 75 | Weldable | Green & Red | 420 MPa | 620 MPa | 1.25 min | 16 | 10.5 | | Grade 550 | Grade 80 | Regular | Blue | 550 MPa | 725 MPa | 1.25 min | 20 | 12 | | Grade 550 | Grade 80 | Weldable | Blue & Red | 280 MPa | 420 MPa | 1.25 min | 25 | 13.5 | | -- | -- | Weldable | Yellow & Red | 280 MPa | 420 MPa | 1.25 min | 28 | 15 | | -- | -- | -- | -- | -- | -- | -- | 32 | -- | | -- | -- | -- | -- | -- | -- | -- | 36 | -- | | -- | -- | -- | -- | -- | -- | -- | 40 | -- | | -- | -- | -- | -- | -- | -- | -- | 50 | -- | **Note:** * Yield Strength, max = 540 MPa max * Yield Strength, max = 675 MPa, max ### Structural Steel **Cold Rolled** * Cold Rolled Steel refers to processes done at or near room temperature. Cold worked steels are typically harder and stronger than standard hot rolled steels. * Cold rolled steel is essentially hot rolled steel that has been through further processing. Once hot rolled steel has cooled, it is then re-rolled at room temperature to achieve more exact dimensions and better surface qualities. * Cold rolled steels are typically harder and stronger than standard hot rolled steels. As the metal is shaped at the lower temperatures, the steel's hardness, resistance against tension breaking, and resistance against deformation are all increased due to work hardening. * Cold rolled steel can often be identified by the following characteristics: * Better, more finished surfaces with closer tolerances * Smooth surfaces that are often oily to the touch * Bars are true and square, and often have well-defined edges and corners * Tubes have better concentric uniformity and straightness **Hot Rolled** * Hot Rolled Steel refers to processes done with heat. * Roll-pressed at very high temperatures over 1,700°F, which is above the re-crystallization temperature for most steels. This makes the steel easier to form, and resulting in products that are easier to work with. * Hot rolled steel is often used in applications where minutely specific dimensions aren't crucial. Railroad tracks and construction projects often use hot rolled steel. * Hot rolled steel can often be identified by the following characteristics: * A scaled surface- a remnant of cooling from extreme temperatures * Slightly rounded edges and corners for bar and plate products (due to shrinkage and less precise finishing) * Slight distortions, where cooling may result in slightly trapezoidal forms, as opposed to perfectly squared angles. * Also called "Mild Steel" in BS EN codes ## Steel Properties * **High strength to weight ratio** * **Elastic limit - yield (Fy) - 415mPa** * **Inelastic - Plastic** * **Ultimate Strength (Fu) -** * **Ductile** * **Strength sensitive to temperature** * **Can corrode** * **Fatigue** * **Standard rolled shapes (W, C, L, T)** * **Open web joists** * **Plate girders** * **Decking** ## Steel Advantage and Disadvantages ### Advantages of Steel as a Structural Material * **High Strength:** The high strength of steel per unit of weight means that the weight of structures will be small. This fact is of great importance for long-span bridges, tall buildings, and structures situated on poor foundations. * **Uniformity:** The properties of steel do not change appreciably with time, as do those of a reinforced-concrete structure. * **Elasticity:** Steel behaves closer to design assumptions than most materials because it follows Hooke's law up to fairly high stresses. The moments of inertia of a steel structure can be accurately calculated, while the values obtained for a reinforced-concrete structure are rather indefinite. * **Permanence:** Steel frames that are properly maintained will last indefinitely. Research on some of the newer steels indicates that under certain conditions no painting maintenance what- soever will be required. * **Ductility:** The property of a material by which it can withstand extensive deformation without failure under high tensile stresses is its ductility. When a mild or low-carbon structural steel member is being tested in tension, a considerable reduction in cross section and a large amount of elongation will occur at the point of failure before the actual fracture occurs. A material that does not have this property is generally unacceptable and is probably hard and brittle, and it might break if subjected to a sudden shock. * **Toughness:** Structural steels are tough, they have both strength and ductility. A steel member loaded until it has large deformations will still be able to withstand large forces. This is a very important characteristic, because it means that steel members can be subjected ### Disadvantages of Steel as a Structural Material * **Corrosion:** Most steels are susceptible to corrosion when freely exposed to air and water, and therefore must be painted periodically. The use of weathering steels, however, unsuitable applications tends to eliminate this cost. Though, weathering steels can be quite effective in certain situations for limiting corrosion, there are many cases where their use is not feasible. In some of these situations, corrosion may be a real problem. * **Fireproofing Costs:** Although structural members are incombustible, their strength is tremendously reduced at temperatures commonly reached in fires when the other materials in a building burn. Many disastrous fires have occurred in empty buildings where the only fuel for the fires was the buildings themselves. Furthermore, steel is an excellent heat conductor non-fireproofed steel members may transmit enough heat from a burning section or compartment of a building to ignite materials with which they are in contact in adjoining sections of the building. * **Susceptibility to Buckling:** As the length and slenderness of a compression member is increased, its danger of buck- ling increases. For most structures, the use of steel columns is very economical because of their high strength-to-weight ratios. Occasionally, however, some additional steel is needed to stiffen them so they will not buckle. This tends to reduce their economy. * **Fatigue:** Another undesirable property of steel is that its strength may be reduced if it is sub- jected to a large number of stress reversals or even to a large number of variations of tensile stress. (Fatigue problems occur only when tension is involved.) The present practice is to reduce the estimations of strength of such members if it is anticipated that they will have more than a prescribed number of cycles of stress variation. * **Brittle Fracture:** Under certain conditions steel may lose its ductility, and brittle fracture may occur at places of stress concentration. Fatigue-type loadings and very low temperatures aggravate the situation. Triaxial stress conditions can also lead to brittle fracture. ## Properties of Steel Sections ### Structural Steel * **I, T, and C shapes** * **W sections:** a W section approximately 44 inches deep, weighing 335 lb/ft. ## Steel Stress - Strain Curve ## Steel General Properties and Specification * **Stress (σ):** the force per unit cross sectional area applied to an object * **Strain (8):** the extension (or compression) per unit length resulting from an applied stress. * **Elasticity (E):** called as "Young's Modulus of Elasticity. when elastic objects are subject to a tensile or compressive force. The ratio of stress and strain of an object or steel. Only applies when an object is undergoing elastic deformation NOT plastic deformation. ## Design and Analysis of Structural Members ### LFRD vs ASD * Both are two different methods used to ensure the safety and reliability of structures * **LRFD** uses resistance factors to account for uncertainties in material properties and loads, while * **ASD** uses safety factors to provide a margin of safety. * Historical Development: * ASD has been used for over a century and is based on the concept of allowable stress, which is a fraction of the material's yield strength. * LRFD, on the other hand, is a more recent development that takes into account the variability in loads and material properties. * **Design Loads:** * **LRFD**: design loads are calculated using load factors that increase the nominal loads to account for uncertainties. * **ASD**: design loads are calculated using service loads, which are the actual loads expected to be applied to the structure. * **Structural Analysis:** Both LRFD and ASD use the same methods of structural analysis, meaning that the behavior of a structure is independent of the design method used. * **Service Loads:** Service loads, or working loads, are the expected values of individual loads such as dead loads, live loads, wind loads, and snow loads. These loads are estimated in the same manner for both LRFD and ASD. * **Load Combinations:** In both LRFD and ASD, various combinations of loads that may occur simultaneously are considered in the design process. The largest load group or the largest linear combination of loads is used for analysis and design. ### Methods for Designing Structural Members and their Connections * Load and Resistance Factor Design (LRFD); * Allowable Strength Design (ASD). ### Principles * Limit States: The concept of "limit state" is used to define when a structure or part of it ceases to perform its intended function. There are two categories of limit states: strength and serviceability. * Strength Limit States: These define load-carrying capacity, including excessive yielding, fracture, buckling, fatigue, and gross rigid body motion. * Serviceability Limit States: These define performance, including deflection, cracking, slipping, vibration, and deterioration. * Uncertainty in Loads and Resistance: Structural engineers recognize the inherent uncertainty in both the magnitude of loads acting on a structure and the ability of the structure to carry those loads. These uncertainties can be addressed using mathematical probability density functions.