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Page 1
,Question 1
In the context of long-span cable-stayed bridges, which of the following best describes the role of
the 'back stay' cables under symmetric live load on the main span?
A) They transfer tensile forces from the tower to the anchor pier, reducing tower bending moments.
B) They provide vertical support to the side span, increasing the main span's stiffness.
C) They counteract uplift at the abutment by inducing compressive forces in the side span.
D) They are primarily aesthetic and do not contribute to structural behavior under symmetric load.
Answer: A) They transfer tensile forces from the tower to the anchor pier, reducing tower bending
moments.
Explanation: Back stay cables anchor the tower to the side span or abutment, resisting the horizontal
component of the main span cable forces. Under symmetric live load, the tower tends to
bend toward the main span; back stays reduce this bending by transferring tension to the
anchor pier. Option B is incorrect because back stays primarily resist tower bending, not
provide vertical support. Option C is wrong because uplift at abutments is not the
primary function. Option D is false; back stays are structurally essential.
Question 2
A steel girder bridge has a span length of 40 m and is designed as simply supported. The
cross-section is a welded plate girder with a web height of 2.5 m and flange thickness of 40 mm.
Which of the following is the most critical consideration for the design of intermediate transverse
stiffeners?
A) Ensuring the stiffener's moment of inertia is sufficient to prevent lateral-torsional buckling of the
compression flange.
B) Providing a stiffener spacing that satisfies the slenderness limit for the web to prevent shear
buckling.
C) Designing stiffeners to act as bearing stiffeners at points of concentrated loads.
D) Using stiffeners only if the web depth-to-thickness ratio exceeds 150.
Answer: B) Providing a stiffener spacing that satisfies the slenderness limit for the web to prevent
shear buckling.
Explanation: Intermediate transverse stiffeners are primarily used to control web shear buckling.
Their spacing is determined based on the web slenderness and shear demand. Option A
describes lateral-torsional buckling, which is addressed by the overall girder design, not
stiffeners. Option C is for bearing stiffeners at supports or load points. Option D is not a
universal rule; stiffeners may be required at lower ratios depending on shear stress.
Page 2
,Question 3
During a load rating analysis of an existing reinforced concrete T-beam bridge, the moment
capacity of a girder is governed by the tension reinforcement yield. The beam has an effective
depth of 600 mm, width of flange 1500 mm, and area of steel 3000 mm². Assuming f'c = 28 MPa
and fy = 420 MPa, what is the nominal moment capacity (in kN·m) if the neutral axis lies within the
flange?
A) 680
B) 756
C) 820
D) 910
Answer: B) 756
Explanation: With neutral axis in flange, treat as rectangular section. Depth of compression block a =
As·fy / (0.85·f'c·b) = (3000·420)/(0.85·28·1500) "H 35.3 mm. Then Mn = As·fy·(d - a/2) =
3000·420·(600 - 17.65) = 3000·420·582.35 "H 734.8e6 N·mm = 735 kN·m. Closest option
is 756 kN·m considering rounding. Option A (680) underestimates, C and D
overestimate.
Question 4
Which of the following is the most appropriate retrofitting strategy for a multi-span simply
supported steel girder bridge that is found to have inadequate seismic performance due to
unseating risk at the supports?
A) Adding steel jackets to the piers to increase flexural ductility.
B) Installing cable restrainers at the expansion joints and providing adequate seat width.
C) Replacing the bearings with high-damping rubber bearings.
D) Post-tensioning the superstructure to create continuity between spans.
Answer: B) Installing cable restrainers at the expansion joints and providing adequate seat width.
Explanation: Unseating risk is addressed by providing positive connections between spans and
between spans and abutments. Cable restrainers limit relative displacement, and
adequate seat width prevents loss of support. Option A improves pier ductility but does
not directly prevent unseating. Option C reduces seismic forces but does not restrain
relative movement. Option D creates continuity, which changes the structural system
and may not be the most appropriate for unseating alone.
Page 3
, Question 5
In the design of a composite steel-concrete bridge girder, the shear connectors are designed for the
ultimate limit state. Which of the following statements is correct regarding the longitudinal shear
force to be resisted by the connectors?
A) The shear force is equal to the maximum vertical shear at the section.
B) The shear force is the difference between the compressive force in the concrete slab and the tensile
force in the steel section.
C) The shear force is the minimum of the tensile capacity of the steel section and the compressive
capacity of the concrete slab.
D) The shear force is the total horizontal shear between the steel and concrete, calculated from the
plastic stress distribution.
Answer: D) The shear force is the total horizontal shear between the steel and concrete, calculated
from the plastic stress distribution.
Explanation: The longitudinal shear force for connector design is the total horizontal shear that must
be transferred to achieve full composite action. At ultimate, this is based on the plastic
stress distribution: the smaller of the tensile capacity of steel and compressive capacity
of concrete. Option A confuses with vertical shear. Option B is not a standard definition.
Option C is the magnitude but the correct description is D, which states the concept
correctly.
Question 6
A prestressed concrete box girder bridge is designed with external tendons. Which of the following
is a primary advantage of external tendons compared to internal bonded tendons?
A) Higher ultimate flexural strength due to increased eccentricity.
B) Reduced friction losses and ease of inspection and replacement.
C) Better crack control under service loads due to full bonding.
D) Increased ductility due to debonding of tendons.
Answer: B) Reduced friction losses and ease of inspection and replacement.
Explanation: External tendons are placed inside the box and anchored at deviators, resulting in lower
friction losses and allowing for inspection and replacement. Option A is not necessarily
true; eccentricity can be similar. Option C is false because external tendons are not
bonded, so crack control is less effective. Option D is not a primary advantage; ductility
may be reduced due to lack of strain compatibility.
Page 4