Assuming linear elastic bending with small deformations and planes perpendicular to the neutral axis remain plane after bending, then for a rectangular beam:
Moment = (Yield Stress)*(Second Moment of Area)/(Distance of surface to Neutral Axis)
For Ultimate Bending Moment, assume stress is uniform throughout the beam, and acting through half the distance from surface to neutral axis, then:
Moment = Stress * (Area/2)*(h/4 + h/4)
For a better visualization check out Popov's textbook, Engineering Mechanics of Solids, Chapter 6, Section 6.10
Steel I beams
Allowable stress would normally refer to design using Allowable Strength Design, also known as working strength design. In this the allowable stress is usually a fraction of the yield strength and can be different for uniform tension and bending. Typically mild steel has a yield strength of about fy=250MPa with allowable stresses in Tension, 0.6fy=150MPa Bending, 0.66fy=165MPa
The "W" in steel I-beam designations refers to wide-flanged beams. Most wide-flanged beams are symmetric about both the vertical and horizontal axes.
Elevator!
you may have 2 kinds of failures. there is the buckling and the bending. in the bending there is compression and tension, while in the buckling there i torsion and shear. if the beam is restrained but not stiffened you may have Lateral Torsional Buckling, but if it is restrained and stiffened throughout, then you will have Tension Field Action and this would result in a higher load durability.
The moment of inertia of a steel section depends on its shape and dimensions. It is a measure of its resistance to bending. It is often calculated using specific formulas for common geometric shapes like rectangles, circles, or I-beams. The moment of inertia is an important parameter in structural engineering for analyzing the bending behavior of steel beams and columns.
Curtailment is optimizing steel w.r.t changes in Bending moment over a section
to prevent the beam from failing immediately when a crack occurs. If the ultimate resisting moment is less than the crcking moment the beam wold fail, but by putting a minimum percentage of steel i the concrete this can be avoided.
Beams are structural elements used to support loads and transfer them to supports. They resist bending and torsional forces to maintain the stability and strength of a structure. Beams can be made of various materials such as wood, steel, or concrete to suit different applications.
Steel I beams
Steel is stronger than concrete. By adding some reinforcement in the compression zone of a beam, it's bending strength can be increased without increasing the size of the beam. The steel increases the compression strength, while the concrete prevents the slender steel bars from buckling.
The formula to calculate the minimum bending radius for steel is: Minimum Bending Radius = (T * Width) / (2 * K), where T is the thickness of the steel, Width is the overall width of the bend, and K is a factor based on the steel's tensile strength and type of steel.
I searched for properties of 1" x 3" 11 gauge rectangular steel tubing, but that is an odd size. We will have to calculate the section modulus (excluding corner radius): S = bd^3 - b1d1^3/6d b = 1" d = 3" b1 = 1 - 2x0.091 = 0.818 d1 = 3 - 2x0.091 = 2.818 S = [(1 x 3^3) - (0.818 x 2.818^3)] / (6 x 3) = 0.483 in^3 M (maximum bending moment) = [P (point load) x l (length)] / 4 Solving for P: P = 4M/l M = s x S Where: s (allowable bending stress) = .55 x yield strength of steel To be conservative we will assume that the steel you have is 30,000 psi M = .55 x 30,000 x 0.483 = 7,969 in-lb P = 4 x 7,969 / 72 in = 442#
bar cranking is the process of bending up the bottom steel bars in upward direction. it is mainly to prevent upward bending moment near the joint. also useful for attaching stirrup bar efectivly. cranking is also used in two way slabs
composite deck
Steel beams used in construction. Steel kitchen knives.
Allowable stress would normally refer to design using Allowable Strength Design, also known as working strength design. In this the allowable stress is usually a fraction of the yield strength and can be different for uniform tension and bending. Typically mild steel has a yield strength of about fy=250MPa with allowable stresses in Tension, 0.6fy=150MPa Bending, 0.66fy=165MPa