CENG 106A Introduction to Steel Structures PDF

26/09/2024 CENG 106A PCS 2- Structural Engineering (Design of Steel Structures) Engr. Rachel June D. Samarita, MSCE-SE, M.ASEP College of Engineering and...

26/09/2024 CENG 106A PCS 2- Structural Engineering (Design of Steel Structures) Engr. Rachel June D. Samarita, MSCE-SE, M.ASEP College of Engineering and Instructor Information Technology Learning Outcomes After the completion of the lecture, students will be able to: 1. Identify the practical use of steel to different structures 2. Understand the codes, specifications and philosophies in designing steel structures 3. Use ASD and LRFD design methods in steel design College of Engineering and Information Technology  26/09/2024 What is Steel Structure?  A steel structure is an assemblage of a group of members (elements) expected to sustain their share of applied force and transfer them safely to the ground.  Depending on the orientation of the member in structure and its structural use, the member is subjected to forces either axial, bending or torsion, or a combination thereof.  Axial load can be either tensile or compressive, and accordingly the members are called tension member or compression member. College of Engineering and Information Technology Categories of Steel Structures  Framed Structures College of Engineering and Information Technology  26/09/2024 Common Steel Structures Crane Girders (Columns, Beams) College of Engineering and Information Technology Common Steel Structures Plate Girders College of Engineering and Information Technology  26/09/2024 Common Steel Structures Transmission Towers College of Engineering and Information Technology Common Steel Structures Shell-type Structures College of Engineering and Information Technology  26/09/2024 Common Steel Structures Truss Bridge College of Engineering and Information Technology Common Steel Structures Suspension Bridge College of Engineering and Information Technology  26/09/2024 Common Steel Structures Cable Stayed Bridge College of Engineering and Information Technology Advantages of Steel Structures  Ability to resist high loads  Lighter in weight  High ductility (ability to deform substantially in either tension or compression before failure)  Better quality control since they are executed in workshops/ fabrication yard  No need for formwork  Faster construction College of Engineering and Information Technology  26/09/2024 Disadvantages of Steel Structures  Cost of maintenance – Steel structure exposed to air and water, such as bridges are susceptible to corrosion and needs regular maintenance.  Tendency to buckling  The strength of steel reduced substantially when heated at temperature commonly observed in building fires, hence need fire resistance treatment.  Construction of steel structure requires skilled persons and high accuracy requires during fabrications. College of Engineering and Information Technology Stress – Strain Curve Ultimate Stress Breaking Stress yield Point Strain Hardening Region Necking Region Yielding Elastic (Plastic Range) Limit College of Engineering and Information Technology  26/09/2024 Stress – Strain Curve College of Engineering and Information Technology Design Basis (NSCP C101-15)  The design of members and connections shall be consistent with the intended behavior of the framing system and the assumptions made in the structural analysis. Unless restricted by the code, lateral load resistance and stability may be provided by any combination of members and connections.  Designs shall be made according to the provisions for Load and Resistance Factor Design (LRFD) or to the provisions for Allowable Strength Design (ASD).  Design shall be based on the principle that no applicable strength or serviceability limit state shall be exceeded when the structure is subjected to all appropriate load combinations. College of Engineering and Information Technology  26/09/2024 Limit States  What is limit state? The term “limit state” is used to describe a condition at which a structure or part of a structure ceases to perform its intended function.  Two categories of limit states are: 1. Strength limit state 2. Serviceability limit state College of Engineering and Information Technology Limit States  Strength Limit States Excessive yielding Fracture due to fatigue Buckling  Serviceability Limit States Deflection Vibration Deterioration – Corrosion on steel Fire hazards on structure College of Engineering and Information Technology  26/09/2024 Design Philosophies  Load and Resistance Factor Design (LRFD) Design according to the provisions for LRFD satisfies the requirements of NSCP Chapter 5 (Structural Steel) when the design strength of each structural component equals or exceeds the required strength determined on the basis of the LRFD load combinations. Design shall be in accordance with NSCP Eq. 502.3-1: Ru ≤  Rn Where: Ru = required strength (LRFD) Rn = nominal strength  = resistance factor  Rn = design strength College of Engineering and Information Technology Design Philosophies  Allowable Strength Design (ASD) Design according to the provisions for ASD satisfies the requirements of NSCP Chapter 5 (Structural Steel) when the allowable strength of each structural component equals or exceeds the required strength determined on the basis of the ASD load combinations.. Design shall be in accordance with NSCP Eq. 502.3-2: Ra ≤ Rn /  Where: Ra = required strength (ASD) Rn = nominal strength  = safety factor Rn /  = allowable strength College of Engineering and Information Technology  26/09/2024 Load Combinations  Allowable Strength Design (ASD) College of Engineering and Information Technology Load Combinations  Load and Resistance Factor Design (LRFD) College of Engineering and Information Technology  26/09/2024 Structural Loads and Load Paths College of Engineering and Information Technology Structural Loads Dead Load Floor Live Load Live Loads Gravity Loads Roof Live Load Rain Load Structural Loads Snow/ Ice Load Wind Load Earth Pressure Earthquake Lateral Loads Load Water Pressure Other Lateral Loads Blast & Impact Loads Thermal Load College of Engineering and Information Technology  26/09/2024 Gravity Loads  Dead Loads Consist of the weight of all materials of construction incorporated into the building or other structure, including but not limited to walls, floors, roofs, ceilings, stairways, built-in partitions, finishes, cladding, and other similarly incorporated architectural and structural items, and fixed service equipment, including the weight of cranes. (See NSCP Table 204-1 & 204-2) College of Engineering and Information Technology Gravity Loads  Live Loads Loads produced by the use and occupancy of the building or other structure and do not include dead load, construction, or environment loads. (See NSCP Table 205-1, 205-2 and 205-3) College of Engineering and Information Technology  26/09/2024 Lateral Loads  Wind Load An external pressure or force that the wind exerts on a building or structure. (See NSCP Section 207) College of Engineering and Information Technology Lateral Loads  Earthquake Load An inertial force produced in the building or structure caused by seismic excitation. (See NSCP Section 208) College of Engineering and Information Technology  26/09/2024 Load Path Fundamentals  A load path is the chain of structural elements that a load follows to get to the foundations which is normally where the assessment of load path stops.  “Tracing” or “chasing” the loads  Each structural element must be designed for all loads that pass through it College of Engineering and Information Technology Load Path Fundamentals Area load Slab to Beams Beam to Girders College of Engineering and Information Technology  26/09/2024 Load Path Fundamentals Girders to Columns Columns to Foundation College of Engineering and Information Technology End of Presentation Thank You! College of Engineering and Information Technology