Structural Engineering Flashcards

In steel design, the term 'compact section' means that the section can:

Answer: Develop full plastic moment capacity before local buckling

A compact section has width-to-thickness ratios small enough to allow full plastic hinge formation before local buckling occurs.

For a fixed-fixed beam with a central point load P and span L, what is the fixed-end moment at each support?

Answer: PL/8

For a fixed-fixed beam with a central point load, the fixed-end moment at each support = PL/8 by standard fixed-end moment tables.

Which of the following increases the critical buckling load of a column?

Answer: Reducing the effective length factor K

Euler's buckling load Pcr = π²EI/(KL)²; reducing K (by adding fixed end conditions) increases Pcr.

In reinforced concrete, the purpose of stirrups (shear links) in a beam is to:

Answer: Resist diagonal tension (shear) and confine the concrete core

Stirrups resist diagonal tensile stresses caused by shear and also provide confinement to the concrete, improving ductility.

The degree of static indeterminacy of a propped cantilever (fixed at one end, pinned at other, single span) is:

Answer: 1

A propped cantilever has 4 reactions (3 at fixed end + 1 vertical at pin) but only 3 equilibrium equations, making it once statically indeterminate.

What is the primary function of the neutral axis in a flexural member?

Answer: It is the axis where bending stress is zero, separating tension and compression zones

The neutral axis is where normal bending stress transitions from compression to tension (or vice versa), resulting in zero bending stress at that location.

In the context of soil-structure interaction, a 'pile foundation' is preferred over a 'shallow foundation' when:

Answer: The soil near the surface has insufficient bearing capacity to support the structural loads

Pile foundations transfer loads to deeper, stronger soil or rock when near-surface soils cannot provide adequate bearing capacity or settlement control.