Free Bachelor of Civil Engineering Structural Analysis Questions and Answers — Questions and Answers

Question 1: Which one of the subsequent structural loads is not frequently applied to a building?

Rain load (Correct answer)
Dead load
Live load
Environmental load

Correct answer: Rain load

While rain can contribute to live loads on roofs (e.g., ponding water), a distinct 'rain load' is not typically classified as a primary, frequently applied structural load category in the same way as dead, live, or environmental loads (like wind or seismic). Its effects are usually accounted for within the general live load provisions or through proper drainage design, rather than as a separate, major load case for general building structures.

Question 2: What is the maximum permissible decrease percent in the case of a structural member supporting more than one level with a load above 100psf?

10
15
25
20 (Correct answer)

Correct answer: 20

Building codes allow for live load reductions on structural members supporting large tributary areas or multiple floors, as the probability of the entire area experiencing the full design live load simultaneously is low. However, for members supporting more than one level with a significant load (above 100 psf), a maximum permissible reduction is often capped. This 20% limit ensures a conservative design, preventing excessive reduction that could compromise safety even if the standard reduction formula might yield a higher value.

Question 3: Which of the following structures is statically determined?

Fixed beam
Two hinged arch
Continuous beam
Double overhanging (Correct answer)

Correct answer: Double overhanging

A statically determinate structure is one where all unknown reactions and internal forces can be determined solely using the equations of static equilibrium. A double overhanging beam, when supported by two simple supports, has exactly three unknown reactions (two vertical reactions and one horizontal reaction if applicable), which can be solved using the three equilibrium equations (sum of forces in x, y, and sum of moments). In contrast, fixed beams, two-hinged arches, and continuous beams typically have more unknowns than equilibrium equations, making them statically indeterminate.

Question 4: What is the load factor for H in the equation U-0.9D + 1.6W + 1.6H if H's structural action cancels out W's or E's?

0 (Correct answer)
0.1
0.05
0.005

Correct answer: 0

In Load and Resistance Factor Design (LRFD), load factors are applied to nominal loads. If a load (H) has a structural action that counteracts or reduces the effect of other primary loads (like wind W or earthquake E), it is considered a beneficial load in that specific load combination. To ensure a conservative design, the load factor for such beneficial loads is typically taken as 0, meaning its positive contribution is ignored to design for the worst-case scenario.

Question 5: If the hospital is constructed of structural steel frames, what will be the value of Vmax in the previous question?

.03813gw
.02813gw (Correct answer)
.04813gw
.01813gw

Correct answer: .02813gw

The value Vmax represents the maximum base shear in seismic design, which is the total lateral force at the base of a structure due to an earthquake. For a hospital, classified as an essential facility, and constructed with structural steel frames, specific seismic design parameters and formulas from building codes (e.g., ASCE 7) are used. The coefficient 0.02813 would be derived from factors like the seismic response coefficient, importance factor, and structural system response modification factor, specific to such a building type and location, when multiplied by the total effective seismic weight (gw).

Question 6: How many unknowns would there be in a structural system if we used link support?

0
1 (Correct answer)
2
4

Correct answer: 1

A link support, also known as a short link or a two-force member, is a structural support that can only transmit force along its axis. It provides a single reaction force, which is always directed along the line connecting its two pins. Therefore, it introduces only one unknown reaction component into the structural system, simplifying the analysis compared to other support types.

Question 7: Which of the following is not a component of trusses?

Channel
Metal bars
Concrete (Correct answer)
Wooden struts

Correct answer: Concrete

Trusses are typically frameworks composed of slender members connected at their ends, primarily designed to carry axial forces (tension or compression). These members are commonly made from materials like steel (e.g., metal bars, channels, angles) or wood (e.g., wooden struts). Concrete, while a fundamental structural material, is generally used for beams, columns, slabs, and foundations, and is not a typical component for the individual members within a standard truss framework due to its weight and less efficient performance in pure tension without extensive reinforcement.

Question 8: Why do short roof trusses have a base plate?

For stability
For rigidity
To transmit load effectively
As provision for temperature related expansion/contraction (Correct answer)

Correct answer: As provision for temperature related expansion/contraction

Base plates for roof trusses, especially for longer spans or in areas with significant temperature fluctuations, are often designed to accommodate thermal expansion and contraction. By allowing for movement (e.g., through slotted holes or roller supports at one end), the base plate prevents the buildup of excessive stresses in the truss or the supporting structure due to changes in temperature. This ensures the long-term integrity and stability of the roof system.

Question 9: Which building will fare best in an earthquake?

Statically determinate
Statically indeterminate (Correct answer)
Depends upon magnitude of earthquake
Statically determinate and indeterminate

Correct answer: Statically indeterminate

Statically indeterminate structures are generally preferred in seismic zones because they offer redundancy and ductility. If one member or connection experiences damage during an earthquake, the load can be redistributed to other parts of the structure, preventing immediate catastrophic collapse. This ability to redistribute loads and deform without sudden failure provides a safer and more resilient response to seismic events compared to statically determinate structures.

Question 10: Which building would require fewer materials overall?

Statically determinate
Depends upon loading
Both will cost equally
Statically indeterminate (Correct answer)

Correct answer: Statically indeterminate

Statically indeterminate structures, while more complex to analyze, often require fewer materials overall compared to statically determinate structures for the same loading conditions. Their inherent redundancy allows for a more efficient distribution of stresses throughout the structure. This means individual members can be designed for lower forces, potentially leading to smaller cross-sections and optimized material usage, ultimately reducing the total material quantity needed.

Question 11: What is carried by the members of a truss?

shear load
axial load (Correct answer)
flexural load
bending load

Correct answer: axial load

Trusses are structural frameworks designed such that their members are primarily subjected to axial forces, meaning forces acting along the longitudinal axis of the member. The connections in an ideal truss are assumed to be pinned, which means they do not transfer bending moments. This design principle ensures that members efficiently carry loads in either tension or compression, making trusses highly efficient for spanning large distances.

Question 12: The moment necessary to rotate a structural member of a uniform section so that it produces a unit slope is known as ____ when it applies to only one end of the member.

Resistance of member
Potential of member
Capacity of member
Stiffness of member (Correct answer)

Correct answer: Stiffness of member

The stiffness of a structural member is its resistance to deformation under load. Specifically, rotational stiffness (or flexural stiffness) is defined as the moment required to produce a unit rotation (or unit slope) at a particular point, such as one end of a beam or column. This property is crucial in structural analysis for determining deflections and internal forces in indeterminate structures.

Question 13: If consecutive structures in an internal beam are identical to one another, then the tributary area is:

Trapezium
Acute triangle
Obtuse triangle
Right angled triangle (Correct answer)

Correct answer: Right angled triangle

In a two-way slab system, where the slab is supported by beams on all four sides, the load from the slab is distributed to the supporting beams. For a beam segment located at a corner of a slab panel, the tributary area of the slab contributing load to that segment can be idealized as a triangle, often a right-angled triangle, leading to a triangular load distribution on the beam. This occurs due to the assumption that loads are transferred to beams along lines drawn at 45 degrees from the corners of the slab panel.

Question 14: If the total gravity load is x and 10% of it is placed to the 10th level of a structure, what will the static lateral force there be?

0.1x
0.001x (Correct answer)
0.01x
x

Correct answer: 0.001x

This question pertains to the distribution of static lateral forces, typically seismic forces, in a multi-story building. While the exact calculation of lateral force at a specific level (Fx) depends on the total base shear (V), the weight at that level (wx), and its height (hx), the value 0.001x indicates that the lateral force at the 10th level is a very small fraction (0.1%) of the total gravity load. This magnitude is plausible for seismic forces at a single floor in a multi-story structure, reflecting the complex distribution of base shear over height.

Question 15: What should be the bare minimum number of joints necessary for the stability of an equilibrium equation if a structure has a total of 10 joints?

7
8
9
10 (Correct answer)

Correct answer: 10

For a structure to be in stable equilibrium, every part of it, including each joint, must satisfy the conditions of equilibrium. This means that the sum of forces in all directions and the sum of moments must be zero at every joint. Therefore, if a structure has 10 joints, all 10 joints must be considered in the equilibrium equations to ensure the overall stability of the system.

Question 16: If a structure has 2j - r members, it will be as follows:

stable
unstable
depends upon structure (Correct answer)
depends upon magnitude of load

Correct answer: depends upon structure

The formula m = 2j - r is a necessary condition for static determinacy and stability of a planar truss, where 'm' is the number of members, 'j' is the number of joints, and 'r' is the number of external reactions. If m = 2j - r, the truss is statically determinate. However, this condition alone is not sufficient to guarantee stability; a structure can satisfy this equation but still be unstable due to improper arrangement of members (e.g., forming a mechanism) or inadequate support conditions. Therefore, its stability ultimately 'depends upon the structure's' specific geometry and support configuration.

Free Bachelor of Civil Engineering Structural Analysis Questions and Answers

Which one of the subsequent structural loads is not frequently applied to a building?