What is the purpose of analyzing a three-hinged arch by disassembling it at its hinges, as shown in Fig. 5-9?

Correct answer: To solve for the six unknown reactions using six available equilibrium equations.

Explanation

A three-hinged arch is statically determinate. By conceptually disassembling the arch into its two main components at the hinges, we create free-body diagrams for which we can write a total of six equilibrium equations (three for each component). This is sufficient to solve for the six unknown reaction components (two at each of the two supports and two at the crown hinge).

Other questions

Question 1

When deriving the relations between the force in a cable and its slope, what two key assumptions are made about the cable's properties?

Question 2

What form does a cable take when it supports several concentrated loads and has negligible weight?

Question 3

According to the analysis in Section 5.3, what is the shape of a cable subjected to a uniform horizontally distributed vertical load, w0?

Question 4

In the analysis of a cable under a uniform distributed load, what does the term FH represent?

Question 5

In Example 5.2, a cable supports a girder weighing 850 lb/ft over a 100 ft span. The supports A and C are at different elevations, 40 ft and 20 ft respectively, above the lowest point B. What is the calculated horizontal distance, x', from the lowest point B to the support C?

Question 6

What is a funicular arch?

Question 7

Which type of arch described in Section 5.4 is statically determinate and not affected by settlement or temperature changes?

Question 8

In the analysis of the three-hinged arch in Example 5.4, which supports a uniform load of 500 lb/ft over a 100 ft span with a 25 ft rise, what is the vertical support reaction at C (Cy)?

Question 9

What is the primary function of a tie rod in a tied arch?

Question 10

For the parabolic three-hinged arch in Example 5.4, what are the calculated values for the internal shear (VD) and moment (MD) at point D, located at x = 25 ft?

Question 11

In the analysis of the three-hinged tied arch in Example 5.5, what is the calculated tension force in the main tie member FAE?

Question 12

What is the primary difference between a fixed arch and a two-hinged arch in terms of static indeterminacy?

Question 13

In Example 5.3, a suspension bridge is analyzed. What is the value of the constant horizontal component of cable tension, FH, determined from the analysis?

Question 14

Why is it necessary to have a ninth equation, often related to cable geometry, to solve for the unknowns in a cable system with several concentrated loads as described in Section 5.2?

Question 15

What is the equation for a parabolic cable with its origin at the lowest point, as given by Equation 5-9 in Section 5.3?

Question 16

In Example 5.1, what is the calculated tension in cable segment BC (T_BC)?

Question 17

Where does the maximum tension in a cable supporting a uniform horizontally distributed load occur?

Question 19

In Example 5.6, a three-hinged trussed arch with a 40 ft total span and 15 ft center height is designed to have a funicular (parabolic) shape for a symmetric loading. What is the required height, h1, of the joints B and D, which are 10 ft horizontally from the center?

Question 20

If a cable supports its own weight and no other loads, what is the specific name for the curve it forms?

Question 21

In Example 5.2, what is the calculated tension in the cable at its lowest point, B (TB)?

Question 22

What are the components of the three-hinged arch shown in Figure 5-7?

Question 23

In the tied arch of Example 5.5, what is the compressive force in member CB (FCB)?

Question 24

If a girder in a suspension bridge has an internal pin at some intermediate point, what effect does this have on the structural analysis?

Question 25

In Example 5.1, what is the final calculated vertical dimension h?

Question 26

Why is the parabolic approximation for a cable's shape under its own weight often acceptable in structural applications?

Question 27

In the context of the three-hinged arch in Figure 5-9, once the support and hinge reactions are found, how are the internal loadings (normal force, shear, moment) at an arbitrary point D determined?

Question 28

Based on Example 5.4, how does the maximum bending moment in a parabolic arch under a uniform load compare to that in a simply supported beam with the same span and load?

Question 29

What type of internal force is primarily resisted by an arch, making it essentially an 'inverted cable'?

Question 30

What is the consequence of using a roller support instead of a hinge for one of the supports of a two-hinged arch?

Question 31

In Example 5.3, the maximum tension in the cable, Tmax, is calculated using Equation 5-11. What is this calculated maximum tension?

Question 32

For the three-hinged trussed arch in Example 5.6, what happens to the top cord and diagonal members when the arch has a funicular shape for the symmetric loading?

Question 33

What is the relationship between the slope of a cable (dy/dx) and the tension components T and FH at any point?

Question 34

Referring to Example 5.5, what are the vertical support reactions Ay and Ey for the three-hinged tied arch?

Question 35

According to Figure 5-8, which type of arch is indeterminate to the first degree?

Question 36

What is the reason a cable offers no resistance to shear or bending?

Question 37

In Equation 5-8, FH = w0*L^2 / (2h), what do the variables L and h represent?

Question 38

In the open-spandrel arch bridge shown in Example 5.4, the load is assumed to be uniformly transmitted to the arch ribs. What is the total resultant load on the entire 100 ft span?

Question 39

Why must the load in each hanger of a suspension bridge be the same to ensure the cable maintains a parabolic shape?

Question 40

In Example 5.1, the equilibrium of point B is analyzed. The equation `TBA sin(theta_BA) - 4.82 kN sin(32.3) - 3 kN = 0` is used. What does the 3 kN term represent?

Question 41

What does the term 'springline' refer to in the context of an arch as shown in Figure 5-7?

Question 42

In the analysis of the tied arch in Example 5.5, the dashed member GF is intended to carry no force. What type of member is GF?

Question 43

What is the primary reason for analyzing a three-hinged arch in two separate parts, sectioned at the crown hinge?

Question 44

In the derivation for a cable under uniform load, what does integrating the equation d(T sin(theta))/dx = w0 yield?

Question 45

What distinguishes a 'tied arch' from other two-hinged or three-hinged arches?

Question 46

In the context of the cable system in Example 5.1, how many unknown external reactions and unknown cable tensions are there in total?

Question 47

For the three-hinged arch in Example 5.4, why is the vertical component of the reaction at hinge B (By) equal to zero?

Question 48

What is the term for the part of an arch between the crown and the springline, as labeled in Figure 5-7?

Question 49

In the suspension bridge analysis in Example 5.3, how is the equivalent uniform load w0 determined?

Question 50

What is the force in the vertical member FGC in the tied arch of Example 5.5?