Dr. Ali I. Tayeh First Semester LRFD-Steel Design Dr. Ali I. Tayeh First Semester 1

Steel Design Dr. Ali I. Tayeh Introduction

Objectives To understand basic principles and methods for Steel Design. To practice problem for Designing and checking Trusses, Columns , Beams (shear-Moments-Torsion…) , Beam-columns, Bolts (Geometry-Distribution..), Supports ,Welded connection. To make congruent between the selected section and all applied force ,taking in consideration economic and availability. 3

Trusses and Frames 4

Grading Mid Exam 30% Homework and Quizzes 30% Final Exam 40% 5

Text book LRFD STEEL DESIGN Third edition WILLIAM T. SEGUI.

Introduction Structural Engineering: Design of different structures (Buildings, bridges, dams, ships, stadiums, etc.): Satisfy needs or functions Support its own loads Support external loads Steel Design: Selection of structural form . Determination of external loads. Calculation of stresses and deformations. Determination of size of individual members.

Introduction -Materials Strength of a material: ability to resist Stress (tension and compression) without Fracturing Steel Concrete Strength to weight Ratio: very important for design consideration Wood Alloys Deformation: change in shape due to loading Flexibility Elasticity Brittleness Ductility Stress-Strain diagram

Introduction Type of steel and composition

Introduction Advantages of steel as a construction material High load resisting High ductility Easy control for steel structure No formed as in a concrete structure Elastic properties

Introduction Disadvantages of steel as a construction material No ability to resist the fire No ability to resist the corrosion High cost Engineering properties of steel

Introduction -Loads Static Loads: applied slowly that the structure remains at rest during loading Walls Dynamic Loads: applied rapidly to cause the structure to accelerate as a consequence of inertia forces Cars Earthquakes Dead Loads: magnitude and position remains constant Beams, columns, slabs, walls Live Loads: magnitude and position changes Humans Snow Wind

Introduction –Structural steel The most interest test for steel engineering characteristics is Tensile Test If specimen is subjected to an axial load (P)

Introduction –Structural steel The applied load leads to a strain , stress f - axial tensile stress. P- axial load A – cross-sectional area.  - Axial strain. L - length of specimen CL-change in length of specimen.

Stress–Strain Diagram Failure Stress Strain Elastic Plastic Ultimate Strength Yield Strength 1 2 3 4 Lower Yield Strength 4 Upper Yield Strength 3 Elastic limit 2 Proportional limit 1

Introduction -Steel Design The relationship between stress and strain is linear up to the proportional limit, the material is said to follow Hook’s law Where: E- Modulus of elasticity.

Introduction -Steel Design Where: e - Elongation (expressed as percent). Lf -Length of specimen at fracture. Lo -Original length.

Introduction -Steel Design Standard cross-sectional shapes Cross-sections of some of the more commonly used hot-rolled shapes : W- shape OR Wide –flange Shape. For example :(w 18×50) W-type of shape. 18 section depth in inches . 50 section weight in pounds per foot .

Introduction -Steel Design Standard cross-sectional shapes S- shape OR American standard S For example :(S 18×70) S-type of shape 18 -section depth in inches . 70 section weight in pounds per foot .

Introduction -Steel Design Standard cross-sectional shapes L- shape OR Angle shape . For example : (L6× L6× ¾’’) (L6× L3× 5/8’’) SEE FIGURE

Introduction -Steel Design Standard cross-sectional shapes C- shape . For example : (C18× 70) SEE FIGURE

Introduction -Steel Design Standard cross-sectional shapes C- shape OR-American standard channel. For example : (C9× 20) SEE FIGURE C9×20

Introduction -Steel Design Standard cross-sectional shapes T- shape OR- standard Tee . For example : (WT18× 115) SEE FIGURE Note This section produced by cutting an I-shape member at middepth (WT18× 115) (W36× 230)

Introduction -Steel Design There are many shapes as : Round Shafting Honed Shafting

Introduction -Steel Design There are many shapes as : Flat Bares Square Bares Round Bares Hexagon Bares Square Tubing

Introduction -Steel Design Examples : 1.5-1. 1.5-3. Home work: 1.5-2. 1.5-4. End