Catenary Cables and Arches Overview
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Questions and Answers

What is a characteristic of a self-anchored suspension bridge?

  • Main cables require earth anchoring.
  • Main cables may be attached to the end of the road deck. (correct)
  • Main cables do not change shape with load.
  • Main cables are attached to the ground.

    • Which design configuration resembles a harp in self-anchored bridges?

  • Fan design
  • Mono design
  • Harp design (correct)
  • Star design

    • What might occur due to uneven loading on cables in suspension bridges?

  • Destruction due to wind and vibration. (correct)
  • Increased stability of the structure.
  • Enhanced flexibility of the cables.
  • Reduction in the cable’s curvature.

    • What is one proposed method to stabilize a clothesline against wind loads?

    <p>Add weights to hold down the clothesline.</p> Signup and view all the answers

    Which method is used to stabilize cable-stayed structures?

    <p>Employ pre-tension cables with reverse curvature.</p> Signup and view all the answers

    What is a consequence of resonance in building materials?

    <p>Destruction of the material.</p> Signup and view all the answers

    How do arches primarily function in structures?

    <p>To redirect forces into axial compression.</p> Signup and view all the answers

    What kind of loads may cause cables in structures to shift shape?

    <p>Dynamic loads and vibrations.</p> Signup and view all the answers

    What is a potential destruction risk for a cable-stayed roof structure?

    <p>Tuning due to resonance.</p> Signup and view all the answers

    Which of the following is NOT a method used for stabilizing cable-stayed structures?

    <p>Employing compressive elements.</p> Signup and view all the answers

    What is the primary characteristic of a funicular arch?

    <p>It carries loads only in axial compression.</p> Signup and view all the answers

    If a load is distributed uniformly along the span of an arch, which shape does the arch resemble?

    <p>A parabola</p> Signup and view all the answers

    What happens to the shape of an arch if the loading conditions change?

    <p>It will no longer be funicular and may fail.</p> Signup and view all the answers

    Who studied the catenary forms of hanging chains in the 17th century?

    <p>Robert Hooke</p> Signup and view all the answers

    Which type of cable structure primarily spans between parallel supports and carries the deck directly?

    <p>Single-curvature structures</p> Signup and view all the answers

    What is the economic span range most suitable for a cable-stayed structure?

    <p>50 to 500 ft</p> Signup and view all the answers

    What is a well-known example of a single-curvature cable structure?

    <p>Golden Gate Bridge</p> Signup and view all the answers

    Which type of structure is primarily subject to axial compression according to the principles discussed?

    <p>Funicular arches</p> Signup and view all the answers

    What is the recommended sag to span ratio for structures?

    <p>1:10</p> Signup and view all the answers

    What is the purpose of adding stabilizing cables in double-cable structures?

    <p>Resist wind uplift</p> Signup and view all the answers

    Which materials are commonly used for making structural cables?

    <p>High strength steel and polypropylene</p> Signup and view all the answers

    Which of the following statements best describes catenary arches?

    <p>They only experience axial compression.</p> Signup and view all the answers

    What forces must the anchorage system in cable-supported structures resist?

    <p>Horizontal thrust from the main cables</p> Signup and view all the answers

    What form does a hanging chain take when forces acting on it change?

    <p>It adapts to remain in tension.</p> Signup and view all the answers

    How do double-curvature structures differ from double-cable structures?

    <p>Double-curvature structures sag similarly to single-curvature ones</p> Signup and view all the answers

    Why do arches typically experience both compression and bending forces?

    <p>Because they cannot adjust to changing loads.</p> Signup and view all the answers

    What is a significant characteristic of the materials used in cable structures?

    <p>They can be twisted or bound strands</p> Signup and view all the answers

    What type of vertical support may be used in cable-supported structures?

    <p>Various types including masts and diagonal struts</p> Signup and view all the answers

    What is the common breaking stress for steel used in cable structures?

    <p>Around 200,000 psi or more</p> Signup and view all the answers

    What is the primary function of vertical supports in a cable-supported structure?

    <p>To provide essential reactions and keep cables elevated</p> Signup and view all the answers

    What type of loads can cables resist?

    <p>Axial tensile forces</p> Signup and view all the answers

    Under what load condition do cables form a catenary shape?

    <p>Under a uniformly distributed load</p> Signup and view all the answers

    What is the primary structural design consideration influenced by the sag-to-span ratio in catenary cable structures?

    <p>The tensile force in the cable</p> Signup and view all the answers

    What is the optimum sag-to-span ratio for a uniformly loaded parabolic cable?

    <p>33%</p> Signup and view all the answers

    What does a catenary cable primarily depend upon?

    <p>The self-weight of the cable</p> Signup and view all the answers

    What happens to cable forces as the sag-to-span ratio increases?

    <p>They decrease inversely</p> Signup and view all the answers

    In which type of load does a cable under a point load form a polygon shape?

    <p>Under multiple point loads</p> Signup and view all the answers

    What is a significant difference between a catenary and a parabolic cable under loading conditions?

    <p>A parabolic shape is ideal when self-weight is insignificant compared to given loads</p> Signup and view all the answers

    What is the relationship between cable diameter and cable length in cable structures?

    <p>A greater diameter is needed as cable length decreases</p> Signup and view all the answers

    Why is it simpler to utilize a parabola for analysis when the sag-to-span ratio exceeds 5?

    <p>The shapes are nearly identical</p> Signup and view all the answers

    Study Notes

    Catenary Cables and Arches

    • Cables are efficient structural components, able to withstand high tensile forces with a small cross-section. They are a cost-effective way to span large distances.

    • Cables can only withstand axial tensile forces, not compression or bending moments. They are flexible and their shape changes under various loads to maintain equilibrium.

    • A single point load on a cable creates two straight lines meeting at the load application point.

    • A uniformly distributed load on a cable results in a catenary or parabolic shape.

    • The sag-to-span ratio of a catenary cable significantly affects cable forces. Higher ratios (generally above 5) lead to shapes nearly identical to parabolas.

    • Cable forces are inversely proportional to sag.

    • To decrease cable length, a larger cable diameter is needed, therefore, there is an impact on compressive forces in the supporting structure.

    • The optimum sag-to-span ratio for uniformly loaded parabolic cables is 33%.

    • Suspension cable structures, often involving a sag-to-span ratio between 1:8 and 1:10, are frequently used for building roofs.

    Classification of Cable Structures

    • Single-curvature: Parallel cables spanning between supports, often supporting decks directly in designs like the Dulles Airport Terminal, Akashi Kaikyo Bridge, and the Golden Gate Bridge.

    • Double-cable: Stabilizing cables below the primary suspension cables are added to resist wind uplift forces, for instance, in Utica Memorial Auditorium.

    • Double-curvature: Primary suspension cables sag between supports, and stabilizing cables run perpendicularly with opposite curvature, examples are the roof of Dorton Arena.

    Materials

    • Cable materials commonly include mild steel, high-strength steel, stainless steel, polypropylene, fiberglass, and carbon fiber.

    • High tensile strength steel is frequently used for reliability and cost-effectiveness.

    • Structural cables are a series of intertwined small strands.

    Cable-Supported Structures

    • Main components of a cable-supported structure include main cables, vertical supports (towers, masts, or piers), anchorages, and stabilizers.

    • Vertical supports support cables and provide essential reactions.

    • The horizontal thrust needs to be resisted via a suitable anchorage system. Earth-anchored systems attach the main cables to the ground; self-anchored cables attach to the deck edge of the bridge.

    • Cable connections to the bridge deck can have various forms (fan, harp, star, etc.) but should resist changes in shape due to load shifts.

    Resonance and Durability

    • Materials and structures have natural vibration frequencies. External forces matching these frequencies can cause resonance, leading to destruction.

    • Suspension bridges can be subject to destruction due to external forces such as wind.

    • Stabilizers, pre-tension cables, or other countermeasures are employed to protect the structure against damage from vibrational resonance due to loads, wind, or other factors.

    • Cable removal/replacement during the structure's life is a critical factor in maintenance.

    Arches

    • Arches are historically used to redirect forces into compression, enabling them to span openings.

    • A "funicular arch" is the compressive equivalent of an inverted catenary cable.

    • A uniformly distributed load results in a parabolic-shaped arch, whereas a uniformly distributed load creates a catenary arch.

    • During load changes or if outside forces affect the arches, bending and compression are often involved simultaneously.

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    Catenary Cables and Arches PDF

    Description

    This quiz explores the principles of catenary cables and their behavior under various loads. Learn about the efficiency of cables in structural applications, the significance of sag-to-span ratios, and how these elements affect cable forces. Perfect for students in engineering and architecture.

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