EI Structural Analysis & Design 3

Question 1

According to ASCE 7, which load combination governs for a building subjected to dead load (D) and live load (L) using strength design (LRFD)?

Accepted Answer

1.2D + 1.6L

Answer

The ASCE 7 LRFD combination 1.2D + 1.6L is typically the controlling factored load combination for gravity loads.

Question 2

The degree of static indeterminacy of a structure is defined as:

Accepted Answer

The number of unknowns minus the number of independent equilibrium equations

Answer

Degree of indeterminacy = (number of unknowns) − (number of available equilibrium equations); it tells how many extra equations are needed.

Question 3

In reinforced concrete design, the Whitney stress block depth 'a' used in ACI 318 is related to the neutral axis depth 'c' by:

Accepted Answer

a = β₁ × c

Answer

ACI 318 uses a rectangular stress block of depth a = β₁c, where β₁ depends on concrete compressive strength.

Question 4

For a steel W-shape beam in AISC LRFD, the design flexural strength is φMn, where φ equals:

Accepted Answer

0.90

Answer

For flexure in steel design per AISC 360, the resistance factor φb = 0.90.

Question 5

An influence line for a structure shows how a response quantity (e.g., reaction, shear, or moment) varies as:

Accepted Answer

A unit load moves across the span

Answer

An influence line is a diagram showing the variation of a structural response at a specific point as a unit load traverses the structure.

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