1What is the primary function of a truss in engineering structures?
Introduction to trusses
Easy
A.To carry loads primarily by bending
B.To act as a fluid reservoir
C.To resist torsion
D.To carry loads primarily by axial forces
Correct Answer: To carry loads primarily by axial forces
Explanation:
A truss is designed to carry loads primarily through axial forces (tension and compression) in its members.
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2How are the members of an ideal truss connected?
Definition of trusses
Easy
A.By continuous beams
B.By rigid joints
C.By welding
D.By frictionless pins or hinges
Correct Answer: By frictionless pins or hinges
Explanation:
In an ideal truss, all members are assumed to be connected at their ends by frictionless pins or hinges.
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3Where are loads applied in an ideal truss?
Definition of trusses
Easy
A.Only at the joints (nodes)
B.Randomly along the structure
C.At the middle of the members
D.Distributed along the members
Correct Answer: Only at the joints (nodes)
Explanation:
To ensure members only carry axial loads, external loads are assumed to be applied only at the joints.
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4What is the basic geometric shape used to construct a simple truss?
Simple trusses
Easy
A.Pentagon
B.Triangle
C.Square
D.Rectangle
Correct Answer: Triangle
Explanation:
The triangle is the basic geometric unit of a simple truss because it is a rigid shape that cannot be deformed without changing the length of its sides.
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5What happens if a basic square framework is subjected to a shear force?
Simple trusses
Easy
A.It collapses or deforms into a rhombus
B.It becomes a triangle
C.It resists the force perfectly
D.It remains rigid
Correct Answer: It collapses or deforms into a rhombus
Explanation:
A square framework is not inherently rigid; under shear force, the angles can change, causing it to collapse into a rhombus. Adding a diagonal makes it two rigid triangles.
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6Which equation represents the condition for a perfect (statically determinate) 2D simple truss?
Simple trusses
Easy
A.
B.
C.
D.
Correct Answer:
Explanation:
For a simple 2D truss to be perfect and statically determinate, the number of members and joints must satisfy .
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7What type of forces are present in the members of a truss?
Definition of trusses
Easy
A.Torsion and bending
B.Tension and compression
C.Bending and shear
D.Only shear
Correct Answer: Tension and compression
Explanation:
Because loads are applied at the joints and members are pin-connected, the members of a truss carry only axial forces: tension or compression.
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8In the method of joints, the entire truss is in equilibrium, which implies that:
Analysis of truss by method of joint
Easy
A.Equilibrium does not apply
B.Only the supports are in equilibrium
C.Only the members are in equilibrium
D.Each individual joint is also in equilibrium
Correct Answer: Each individual joint is also in equilibrium
Explanation:
If a whole structure is in equilibrium, every part of it, including each individual joint, must also be in equilibrium.
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9How many independent equations of equilibrium are available at each joint for a 2D (coplanar) truss?
Analysis of truss by method of joint
Easy
A.1
B.3
C.6
D.2
Correct Answer: 2
Explanation:
At each joint in a 2D truss, the forces form a concurrent force system. Therefore, only two equilibrium equations are available: and .
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10To start analyzing a truss using the method of joints, you should select a joint that has:
Analysis of truss by method of joint
Easy
A.Exactly 4 unknown forces
B.At least 3 unknown forces
C.No known forces
D.No more than 2 unknown forces
Correct Answer: No more than 2 unknown forces
Explanation:
Since there are only two equilibrium equations available at each joint in a 2D truss, you can solve for a maximum of two unknown member forces at a time.
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11What is a 'zero-force member' in a truss?
Analysis of truss by method of joint
Easy
A.A member that carries no axial load under the given loading conditions
B.A support reaction
C.A member that breaks easily
D.A member that only carries bending moments
Correct Answer: A member that carries no axial load under the given loading conditions
Explanation:
A zero-force member is a member in a truss that, for a particular loading condition, carries no tension or compression.
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12If two non-collinear members meet at an unloaded joint, what are the forces in those members?
Analysis of truss by method of joint
Easy
A.One is tension, one is compression
B.Both are in tension
C.Both are zero
D.Both are in compression
Correct Answer: Both are zero
Explanation:
If only two non-collinear members meet at a joint with no external load or support reaction, both members must be zero-force members to satisfy equilibrium.
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13What is the primary advantage of the method of sections over the method of joints?
Analysis of truss by method of section
Easy
A.It requires fewer equilibrium equations
B.It allows finding forces in all members simultaneously
C.It changes a truss into a beam
D.It allows finding the force in a specific member without solving the entire truss
Correct Answer: It allows finding the force in a specific member without solving the entire truss
Explanation:
The method of sections is highly efficient when you only need to find the forces in a few specific members, as you can 'cut' through them and solve directly.
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14How many independent equilibrium equations are available when considering a section (a free body of a cut portion) of a 2D truss?
Analysis of truss by method of section
Easy
A.1
B.3
C.2
D.4
Correct Answer: 3
Explanation:
For a section of a 2D truss, the forces form a non-concurrent, coplanar system. Thus, three equations are available: , , and .
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15When using the method of sections, through how many unknown members should you ideally pass a cut?
Analysis of truss by method of section
Easy
A.Exactly 1
B.As many as possible
C.No more than 3
D.Exactly 4
Correct Answer: No more than 3
Explanation:
Because there are only three equilibrium equations available for a 2D section, cutting through more than three unknown members will generally result in an unsolvable system.
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16Which of the following structures is a common application of trusses?
Introduction to trusses
Easy
A.Bridge or roof framework
B.Hydraulic cylinder
C.Solid concrete slab
D.Arch dam
Correct Answer: Bridge or roof framework
Explanation:
Trusses are widely used in structures like bridges, roofs, and towers to span large distances efficiently.
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17If for a truss, the truss is classified as:
Simple trusses
Easy
A.Deficient (unstable)
B.Perfect
C.Statically indeterminate
D.Redundant
Correct Answer: Deficient (unstable)
Explanation:
If a truss has fewer members than required by the equation , it lacks the necessary rigidity and is called a deficient or unstable truss.
When there are more members than necessary for basic rigidity (), the truss is over-stiffened and is known as redundant or statically indeterminate.
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19In the method of sections, what is done after calculating the support reactions?
Analysis of truss by method of section
Easy
A.Apply a moment at every joint
B.Cut the truss into two portions through the members of interest
C.Assume all members are zero
D.Analyze every joint one by one
Correct Answer: Cut the truss into two portions through the members of interest
Explanation:
After finding the reactions, an imaginary section is passed through the truss, cutting the members whose forces are required, and splitting it into two separate free bodies.
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20By convention, how is a tensile force in a truss member usually represented at a joint?
Analysis of truss by method of joint
Easy
A.An arrow pointing away from the joint
B.No arrow is used
C.An arrow pointing towards the joint
D.A curved arrow around the joint
Correct Answer: An arrow pointing away from the joint
Explanation:
A tensile force pulls on the joint, so it is conventionally represented by a vector arrow pointing away from the joint in a free body diagram.
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21An ideal truss is defined by several assumptions. Which of the following is NOT an assumption made in the ideal truss analysis?
Definition of trusses
Medium
A.Members are connected by frictionless pins.
B.Loads are applied only at the joints.
C.The members carry only axial forces (tension or compression).
D.The weight of the members is assumed to be concentrated at the center of the member.
Correct Answer: The weight of the members is assumed to be concentrated at the center of the member.
Explanation:
In an ideal truss, the weight of the members is either neglected or assumed to be divided equally and applied at the joints, not at the center of the member, to prevent bending moments.
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22A planar truss has joints and members. Which condition correctly identifies the truss as a statically determinate and rigid (perfect) truss?
Introduction to trusses
Medium
A.
B.
C.
D.
Correct Answer:
Explanation:
For a perfect planar truss, the number of members must equal . This ensures it is both rigid and statically determinate internally.
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23A certain planar truss consists of 6 joints and 10 members. Based on the standard truss classification equation, this truss is considered to be:
Introduction to trusses
Medium
A.A deficient (unstable) truss
B.A space truss
C.A redundant (statically indeterminate) truss
D.A perfect truss
Correct Answer: A redundant (statically indeterminate) truss
Explanation:
Using the formula , for 6 joints, the required members for a perfect truss is . Since it has 10 members (), it is a redundant truss.
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24Why do the members of an ideal truss carry only axial forces and no bending moments?
Definition of trusses
Medium
A.Because they are always arranged in a triangular pattern.
B.Because they are made of perfectly rigid materials.
C.Because the external loads are always horizontal.
D.Because they are pinned at the ends and loads are only applied at the joints.
Correct Answer: Because they are pinned at the ends and loads are only applied at the joints.
Explanation:
Frictionless pin connections cannot transfer moments, and applying loads only at the joints prevents transverse loading on the members, resulting in purely axial internal forces.
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25In a simple truss, if a joint connects exactly two non-collinear members and there is no external load or support reaction at that joint, what can be concluded about the internal forces in these members?
Simple trusses
Medium
A.Both members are in tension.
B.The force in both members is zero.
C.Both members carry equal but opposite forces.
D.One member is in tension and the other is in compression.
Correct Answer: The force in both members is zero.
Explanation:
By applying and at an unloaded joint with two non-collinear members, both forces must independently be zero to satisfy equilibrium.
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26At a specific joint in a truss, three members meet. Two of the members are collinear. If no external load or support reaction acts on this joint, what is the force in the third (non-collinear) member?
Simple trusses
Medium
A.Cannot be determined without knowing the angles.
B.Equal to half the force in the collinear members.
C.Zero.
D.Equal to the sum of the forces in the collinear members.
Correct Answer: Zero.
Explanation:
Summing forces perpendicular to the two collinear members yields only the component of the third member. For equilibrium (), the force in the third member must be zero.
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27When beginning the analysis of a truss using the method of joints, which of the following joints should be selected first?
Analysis of truss by method of joint
Medium
A.The joint with the maximum number of connected members.
B.Any joint connected to a support.
C.A joint with at least one known external force and no more than two unknown member forces.
D.A joint with three unknown forces where two are collinear.
Correct Answer: A joint with at least one known external force and no more than two unknown member forces.
Explanation:
Because each joint in a planar truss provides exactly two independent equilibrium equations ( and ), you can only solve for a maximum of two unknowns at a time.
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28If an assumed direction of internal force (e.g., tension pointing away from the joint) yields a negative numerical result during calculation, this indicates that:
Analysis of truss by method of joint
Medium
A.The truss is unstable.
B.The member is a zero-force member.
C.The member is in compression.
D.A calculation error has occurred.
Correct Answer: The member is in compression.
Explanation:
A negative result simply means the actual direction of the force is opposite to the assumed direction. If tension (pulling away) was assumed, the member is actually in compression (pushing toward the joint).
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29When applying the method of sections to analyze a planar truss, what is the maximum number of members with unknown forces that should generally be cut by the section line?
Analysis of truss by method of section
Medium
A.Three
B.Four
C.Two
D.Five
Correct Answer: Three
Explanation:
The method of sections isolates a portion of the truss, which acts as a rigid body. There are exactly three equilibrium equations available (, , ), so a maximum of three unknowns can be directly solved.
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30In the method of sections, to find the force in a specific cut member with minimal calculation, one should take the sum of moments about which point?
Analysis of truss by method of section
Medium
A.Any support joint on the truss.
B.The center of gravity of the section.
C.The point of intersection of the lines of action of the other two cut members.
D.The joint where the largest external load is applied.
Correct Answer: The point of intersection of the lines of action of the other two cut members.
Explanation:
Taking moments about the intersection of the other two unknown forces eliminates them from the moment equation (since their moment arms are zero), allowing you to solve directly for the desired member's force.
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31In a truss analysis using the method of joints, a joint connects two members at a angle. An external force acts directly along the axis of one of the members. What is the force in the other member?
Analysis of truss by method of joint
Medium
A.
B.Zero
C.
D.
Correct Answer: Zero
Explanation:
Setting up a coordinate system aligned with the members, the sum of forces perpendicular to the load involves only the second member. Thus, its force must be zero to satisfy equilibrium.
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32Which of the following geometric shapes forms the basic building block of a simple, stable truss?
Simple trusses
Medium
A.Triangle
B.Hexagon
C.Square
D.Rectangle
Correct Answer: Triangle
Explanation:
The triangle is the simplest geometric figure that will not change shape when the lengths of its sides are fixed, making it the fundamental rigid building block for simple trusses.
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33Under what condition is the method of sections vastly preferred over the method of joints?
Analysis of truss by method of section
Medium
A.When the truss is statically indeterminate.
B.When the forces in all members of the truss are required.
C.When the force in only a few specific, centrally located members is required.
D.When the truss contains many zero-force members.
Correct Answer: When the force in only a few specific, centrally located members is required.
Explanation:
The method of sections allows you to cut directly through the members of interest and solve for their forces using the rigid body equilibrium equations, bypassing the need to analyze every joint starting from the supports.
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34A truss joint has four members. Members A and B are collinear on the x-axis, and members C and D are collinear on the y-axis. If there is no external load at the joint, what is the relationship between the member forces?
Analysis of truss by method of joint
Medium
A. and
B.
C. and
D. and
Correct Answer: and
Explanation:
Assuming tension is positive (pulling away), . Similarly, . (Note: based on standard free body diagrams, they carry the same magnitude and type of internal force).
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35What is the primary function of a gusset plate in steel truss construction?
Introduction to trusses
Medium
A.To connect members intersecting at a joint while approximating a pin connection.
B.To act as a friction-increasing mechanism between members.
C.To counteract the self-weight of the tension members.
D.To provide bending resistance at the center of the span.
Correct Answer: To connect members intersecting at a joint while approximating a pin connection.
Explanation:
In actual construction, truss members are often riveted, bolted, or welded to a gusset plate. If the centerlines of the members intersect at a single point on the plate, it closely mimics an ideal pinned joint with purely axial forces.
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36When solving for support reactions before applying the method of joints, the entire truss is treated as:
Analysis of truss by method of joint
Medium
A.A statically indeterminate structure.
B.A collection of particles.
C.A rigid body.
D.A deformable body.
Correct Answer: A rigid body.
Explanation:
To find the global support reactions, the internal members are ignored, and the entire truss framework is treated as a single rigid body subjected to external loads and support reactions.
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37When cutting a truss for the method of sections, it is sometimes necessary to cut through four members. In such a case, how can the problem still be solved using standard statics?
Analysis of truss by method of section
Medium
A.If a specific point can be found where the lines of action of three of the cut members intersect, allowing the fourth to be found via moment equation.
B.By assuming one member is a zero-force member regardless of the geometry.
C.It is impossible; a section must never cut more than three members.
D.If the lines of action of all four members intersect at a single point.
Correct Answer: If a specific point can be found where the lines of action of three of the cut members intersect, allowing the fourth to be found via moment equation.
Explanation:
Even if four members are cut, if three of them intersect at a common point, summing moments about that point will yield an equation with only one unknown (the force in the fourth member).
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38How is a simple truss systematically constructed to ensure stability?
Simple trusses
Medium
A.By overlapping multiple identical triangles from a central hub.
B.By starting with a base triangle of three members and adding two new members for each new joint.
C.By connecting four members with pinned joints to form a square, then adding a diagonal.
D.By arranging parallel top and bottom chords and filling them with vertical members.
Correct Answer: By starting with a base triangle of three members and adding two new members for each new joint.
Explanation:
The mathematical definition of a simple truss is one that can be constructed starting with a rigid triangle and adding two new members meeting at a single new node for every subsequent extension.
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39At a support joint (e.g., a pin support), the external support reactions must be included in the free body diagram of the joint. How many unknowns can the internal members connected to a pin support have, to allow solving the joint directly without prior rigid-body analysis?
Analysis of truss by method of joint
Medium
A.One
B.Three
C.Zero
D.Two
Correct Answer: Zero
Explanation:
A pin support has two unknown reactions (, ). Since a joint provides exactly two equilibrium equations, you cannot solve for any unknown member forces at that joint unless the support reactions are already found via whole-truss analysis.
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40A horizontal section cut passes through a vertical member and two diagonal members of a truss. To find the force in the vertical member, which equilibrium equation is most direct?
Analysis of truss by method of section
Medium
A. about an intersection point of the diagonals.
B.
C.
D. about the center of the vertical member.
Correct Answer: about an intersection point of the diagonals.
Explanation:
Taking the sum of moments about the point where the two diagonal members intersect eliminates their unknown forces, leaving an equation that directly solves for the vertical member.
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41Which of the following conditions is theoretically sufficient but NOT always practically necessary for a planar truss to be internally statically determinate and rigid?
Simple trusses
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
The condition is a necessary condition for internal static determinacy, but for the truss to be stable, the members must also be properly arranged. It is sufficient if built from a basic triangle, but geometry (like collinear joints) can make it unstable despite satisfying the equation.
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42In a complex truss where more than two unknown members meet at every joint initially, which of the following approaches is required if the method of joints is strictly applied?
Analysis of truss by method of joint
Hard
A.Applying the method of sections first to find one member
B.Starting from a support with three unknown reactions
C.Setting up and solving a system of simultaneous linear equations for the entire structure
D.It is impossible to solve using method of joints
Correct Answer: Setting up and solving a system of simultaneous linear equations for the entire structure
Explanation:
If no joint has two or fewer unknowns, the method of joints can still be used by writing out the equilibrium equations for all joints and solving the system simultaneously.
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43A planar truss is subjected to an external load applied directly to the midpoint of one of its members. How does this violate the fundamental assumptions of an ideal truss, and what is the resulting internal force state?
Definition of trusses
Hard
A.It violates the massless member assumption, creating instability.
B.It violates the pin-connected assumption, creating torsion in the member.
C.It violates the rigid body assumption, causing the truss to become a mechanism.
D.It violates the assumption of loads at joints only, creating bending moments and shear forces in the member.
Correct Answer: It violates the assumption of loads at joints only, creating bending moments and shear forces in the member.
Explanation:
Ideal trusses assume loads are applied only at joints. A load on the member itself introduces bending moments and shear forces, meaning the member no longer acts as a pure two-force member.
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44When applying the method of sections, what is the theoretical maximum number of members a cutting plane can pass through if the forces in all cut members must be determined solely from the equilibrium of one of the separated portions?
Analysis of truss by method of section
Hard
A.5
B.2
C.3
D.4
Correct Answer: 3
Explanation:
Because there are only three independent equations of equilibrium (, , ) for a planar rigid body, the cutting plane should generally pass through no more than three members with unknown forces.
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45A section cut passes through four members. Under what specific geometric condition can the force in one of these four cut members still be directly found using a single equilibrium equation?
Analysis of truss by method of section
Hard
A.If two of the members are collinear.
B.If the lines of action of three of the cut members intersect at a single point.
C.If the member to be found is perpendicular to the applied loads.
D.If all four members are parallel.
Correct Answer: If the lines of action of three of the cut members intersect at a single point.
Explanation:
By taking moments about the point of intersection of the three members, their moment contributions become zero, allowing the force in the fourth member to be calculated directly.
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46Consider a joint in a truss where four members meet. Two are collinear, and the other two are collinear but perpendicular to the first two. If there is no external load at the joint, what can be deduced about the forces in the members?
Analysis of truss by method of joint
Hard
A.Forces in opposite collinear members are equal and opposite in magnitude and sense.
B.All four members are zero-force members.
C.Forces in opposite collinear members are equal in magnitude and of the same nature (both tension or both compression).
D.The joint is unstable.
Correct Answer: Forces in opposite collinear members are equal in magnitude and of the same nature (both tension or both compression).
Explanation:
Summing forces along each collinear axis shows that the force in one member equals the force in the opposite member in order to maintain equilibrium. Therefore, they must carry the same type of load (tension or compression) with equal magnitude.
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47A space truss is formed by connecting basic tetrahedral elements. What is the relation between the number of members and joints for internal static determinacy?
Simple trusses
Hard
A.
B.
C.
D.
Correct Answer:
Explanation:
For a space truss, starting with a base triangle (3 members, 3 joints) and adding 3 members for every new joint, the general formula for a statically determinate space truss is .
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48Why is the assumption of 'frictionless pins' at the joints of an ideal truss justifiable in practical riveted or welded trusses?
Introduction to trusses
Hard
A.Because the bending moments induced by joint rigidity are typically small compared to axial forces and can be neglected in primary analysis.
B.Because friction cancels out symmetrically across the truss.
C.Because rivets and welds possess negligible shear strength.
D.Because materials used in trusses exhibit infinite stiffness.
Correct Answer: Because the bending moments induced by joint rigidity are typically small compared to axial forces and can be neglected in primary analysis.
Explanation:
In actual trusses, joints are often riveted or welded, providing rigidity. However, the members are usually long and slender, so the secondary bending moments are small and primary axial forces dominate, making the pin-joint assumption valid.
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49At a joint, three members meet. Two are collinear. If an external force acts at the joint in a direction perpendicular to the collinear members, what is the force in the third member?
Analysis of truss by method of joint
Hard
A.Exactly equal to
B.Zero
C.Cannot be determined without knowing forces in the collinear members
D.Equal to , where is the angle it makes with
Correct Answer: Equal to , where is the angle it makes with
Explanation:
By summing forces perpendicular to the collinear members, the collinear members have no component. Thus, the component of the third member's force along 's line of action must balance , yielding or .
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50When analyzing a K-truss by the method of sections, a standard straight vertical section cuts through four members. What technique is required to solve for the forces in the horizontal chords?
Analysis of truss by method of section
Hard
A.First solve for the vertical members using the method of joints.
B.Take moments about the joint where the two diagonal members intersect.
C.Method of sections cannot be used for K-trusses.
D.Use a curved section that cuts only three members.
Correct Answer: Take moments about the joint where the two diagonal members intersect.
Explanation:
In a K-truss, a vertical cut passes through four members. To find the force in a horizontal chord, moments can be taken about the intersection point of the two diagonal members, eliminating them from the equation.
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51A structure consists of interconnected members, but one member is subjected to a distributed self-weight that cannot be neglected. How must this be handled to still analyze it approximately as an ideal truss?
Definition of trusses
Hard
A.Allocate half of the member's total weight to each of the two joints it connects.
B.Ignore the weight as it acts uniformly.
C.Treat the member as a beam-column and apply superposition.
D.Apply the full weight at the center of gravity of the truss.
Correct Answer: Allocate half of the member's total weight to each of the two joints it connects.
Explanation:
To maintain the ideal truss assumption (loads at joints only), the self-weight of a member is typically idealized by splitting it in half and applying each half as a point load at the adjacent connecting joints.
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52A planar truss satisfies but is internally unstable (a mechanism). Which of the following must be true?
Simple trusses
Hard
A.There is at least one redundant member and at least one unbraced panel (e.g., a rectangular quadrilateral without a diagonal).
B.All joints lie on a single straight line.
C.The truss lacks sufficient external supports.
D.The truss has fewer members than joints.
Correct Answer: There is at least one redundant member and at least one unbraced panel (e.g., a rectangular quadrilateral without a diagonal).
Explanation:
If is satisfied but the truss is a mechanism, it means the members are improperly arranged. There must be an area lacking triangulation (a mechanism) and another area with too many members (redundant).
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53In identifying zero-force members by inspection, under which condition is a member guaranteed to carry zero force?
Analysis of truss by method of joint
Hard
A.It is parallel to the applied external load.
B.It is the only diagonal member in a square panel.
C.It connects a support joint to the top chord.
D.It is one of two non-collinear members meeting at a joint with no external load or support reaction.
Correct Answer: It is one of two non-collinear members meeting at a joint with no external load or support reaction.
Explanation:
If a joint has only two non-collinear members and no external load or support reaction, summing forces along directions perpendicular to each member proves that both members must have zero force.
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54A truss with non-parallel chords is cut by a section passing through top chord , diagonal , and bottom chord . To find the force in the diagonal , what is the most direct mathematical operation?
Analysis of truss by method of section
Hard
A.Summing forces in the Y-direction.
B.Summing forces in the X-direction.
C.Taking moments about the point of intersection of the extended lines of action of and .
D.Taking moments about joint .
Correct Answer: Taking moments about the point of intersection of the extended lines of action of and .
Explanation:
Because the top and bottom chords are not parallel, their lines of action will intersect at a point (say, ). Taking moments about eliminates both chord forces, allowing direct calculation of the force in the diagonal .
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55What distinguishes a 'complex truss' from a 'simple truss' or a 'compound truss'?
Introduction to trusses
Hard
A.It requires three-dimensional analysis.
B.It is formed by connecting two or more simple trusses.
C.It cannot be reduced to simple triangles and cannot be classified as simple or compound.
D.It has a degree of indeterminacy greater than 3.
Correct Answer: It cannot be reduced to simple triangles and cannot be classified as simple or compound.
Explanation:
A complex truss is defined by its geometry; it does not fall into the categories of simple (built from basic triangles) or compound (combinations of simple trusses), and usually requires simultaneous equations for analysis.
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56A joint connects members , , and . Members and form an angle of . Member lies in the same plane. If the joint is under no external loads, what relates the force in () to the forces in and (, )?
Analysis of truss by method of joint
Hard
A. cannot be determined without angles
B.
C. necessarily
D.
Correct Answer:
Explanation:
Assuming equilibrium, the vector sum of , , and is zero. Since and are perpendicular, the magnitude of their resultant is . For equilibrium, must balance this resultant.
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57In the context of idealized trusses, what is the consequence of a member experiencing a slight temperature increase relative to the rest of a statically determinate truss?
Definition of trusses
Hard
A.The truss deforms, but no thermal stresses are developed.
B.The member induces forces in all other members.
C.The truss becomes a mechanism.
D.Internal thermal stresses are developed in the member.
Correct Answer: The truss deforms, but no thermal stresses are developed.
Explanation:
In a statically determinate structure, members can freely expand or contract without restraint from redundancy. Therefore, a temperature change causes geometric deformation but no internal forces (thermal stresses).
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58You make a section cut through a truss that isolates a portion of it. The external forces acting on this isolated portion form a force couple. What must be true about the internal forces in the cut members?
Analysis of truss by method of section
Hard
A.They must form an equal and opposite couple to maintain equilibrium.
B.The assumption of the truss being statically determinate is violated.
C.They must all be in tension.
D.They must all be zero.
Correct Answer: They must form an equal and opposite couple to maintain equilibrium.
Explanation:
For any isolated free-body diagram to be in equilibrium, the sum of moments must be zero. If external forces form a couple, the internal member forces exposed by the cut must provide an equal and opposite balancing moment (couple).
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59Which of the following describes a 'compound truss'?
Simple trusses
Hard
A.A space truss consisting of interconnected tetrahedrons.
B.A truss constructed by adding redundant members to a simple truss.
C.A truss formed by interconnecting two or more simple trusses together.
D.A truss where .
Correct Answer: A truss formed by interconnecting two or more simple trusses together.
Explanation:
A compound truss is defined as a structure formed by rigidly connecting two or more basic simple trusses, often used for longer spans.
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60While solving a truss using the method of joints, you find a calculated member force has a negative sign. What does this rigorously imply about the physical state of the member if your initial assumption was that all forces act away from the joint?
Analysis of truss by method of joint
Hard
A.The member is in compression.
B.The member is in tension.
C.The member is a zero-force member.
D.The external load exceeds the critical buckling load.
Correct Answer: The member is in compression.
Explanation:
Assuming forces act away from the joint defines tension as positive. A negative result means the force acts towards the joint, which indicates the member is pushing against the joint and is therefore in compression.