Civil Engineering Theory of Structure Flashcards
7 cards from real Civil Engineering PE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Civil Engineering Theory of Structure flashcards as text
For a cable carrying a uniformly distributed horizontal load w over span L with a central sag d, the horizontal tension H at the supports is:
Answer: wL²/8d
For a parabolic cable with UDL, the horizontal component of cable tension is H = wL²/(8d), derived from moment equilibrium at midspan.
The upper bound (kinematic) theorem of plasticity states that a load computed by:
Answer: Assuming a valid mechanism is an upper bound on collapse load
The kinematic (upper bound) theorem states that a collapse load calculated from any assumed valid mechanism is greater than or equal to the true collapse load.
For a beam-column subjected to combined axial load P and moment M, the interaction equation used in design checks the condition that:
Answer: P/P_n + M/M_n ≤ 1.0
The linear interaction equation P/P_n + M/M_n ≤ 1.0 ensures combined axial and bending demands remain within the member's capacity.
The theorem of three moments assumes that the slope of the elastic curve is continuous at:
Answer: Each intermediate support
The three-moment equation enforces compatibility by requiring the slope of the deflection curve to be continuous (equal from both sides) at each intermediate support.
Which of the following correctly describes the stiffness of a member with a pin at the far end versus a fixed far end?
Answer: Far-end pinned stiffness = (3/4) × far-end fixed stiffness
For a prismatic member, releasing the far-end fixity to a pin reduces the near-end rotational stiffness from 4EI/L to 3EI/L, which is 3/4 of the fixed-far-end value.
A propped cantilever of span L with UDL w has its prop removed. The released structure is a cantilever. Using compatibility, the prop reaction R is found to satisfy:
Answer: Deflection at prop due to R plus deflection at prop due to w equals zero
The compatibility condition is that the net deflection at the prop location is zero: δ_w (downward from UDL) + δ_R (upward from prop reaction) = 0.
In a space truss, the condition for static determinacy is:
Answer: m + r = 3j
For a space (3D) truss, equilibrium at each joint provides 3 equations, so static determinacy requires m + r = 3j.