Bascule Bridge Design

"Dual LEAF BASCULE BRIDGE"

1. OBJECTIVES:

  • Become familiar with the solid wood work.
  • Become familiar with lathe machine and drilling machine.
  • Build a straightforward pulley.

2. Advantages:

A bascule bridge (commonly referred to as a drawbridge) is a moveable bridge with a counterweight that continually balances a period, or "leaf, " throughout its upward swing action to provide clearance for vessel traffic. It might be single or two times leafed.

3. METHOD:

  • Cut out an arch with the scroll noticed from the 5-by-7-by-2-inches block of pine wood. Make the arch about 3 inches wide and 4 inches high. Make sure to trim in the longest route, so that the lower part of the arch becomes the bottom of the tower, and there is 3 in. left above the most notable of the arch.
  • Measure and mark with the pencil every 1/2 in. across the the surface of the tower, above the arch. At every other mark, slice a notch 1/2 inch deep and 1/2 inch wide with the scroll saw. These are the tower battlements.
  • Center the tower on the 5-by-10-by-1/2-inches block and nail the two pieces together through the bottom to form the tower base.
  • Lay down both 4-by-1/2-by-1/2-inches blocks parallel to one another 3 inches apart on your projects surface.
  • Lay the eight 4-by-1/2-by-1/8-inches strips across the two blocks. Attach the strips to the blocks with finishing nails. This is your drawbridge.
  • Turn in the drawbridge and touch in two finishing claws, one into each stop, as near the ends since you can without splitting the hardwood. Leave the toenails sticking out at night ends of the drawbridge, about 1/4 in. . This would be the pivot end of your gate.
  • Tap in two more finishing nails, one into each stop, about 1/2 inch from the finish opposite the pivot end of the drawbridge. Leave the fingernails or toenails sticking past the sides about 1/4 in. .
  • Lay the drawbridge, stop part down, on the tower base in front of the tower. Place an upholstery staple within the protruding nails on the pivot end and softly tap the staples into the tower base. This should contain the drawbridge in place while and can rotate readily into open and shut positions. Modify the staples and nails if needed.
  • Tap two finishing claws in to the tower, one on either side near the top of the arch. Get them to spaced 4 ins apart, as wide as the drawbridge. Position the fingernails or toenails at about 45 degrees, and leave half of each nail sticking up.
  • Attach one end of every string to the fingernails near the top of the arch. Connect the other ends to the drawbridge.
  • Stain the solid wood with the paintbrush, then allow to dried out.

4. Conversation:

  • SAMPLE DIAGRAM:
  • TERMS AND EXPLANATION:
  • PRACTICAL INFORMATION ABOUT BASCULE BRIDGES:

Almost all dual leaf bascule bridges consist of two cantilever spans projected toward each other, linked at their tips by a suitable shear lock. Other styles of two times leaf bascule are relatively unusual, such as those which form arch bridges in the sealed position, and aren't the topic of the discussion.

Double leaf bascule bridges are most likely the least practical, from a maintenance and operation standpoint, of most popular types of modern time movable bridges. They use two split moving leaves when you might do, with all the current associated charge in construction, operation, and maintenance of two totally self-employed movable bridge leaves. They also join these two moving leaves together for the support of live fill, compounding the difficulties. There are benefits to double leaf bascules: they can start and close slightly more quickly than other type of movable bridge; a dual leaf bascule is less influenced by wind lots than a solo leaf bascule spanning the same route width; they use marginally less structural metal than other types of movable bridges with the same insert ranking spanning the same width of navigation channel; double leaf bascules are less vunerable to collision with vessels navigating past them than other movable bridge types, and they're generally considered more aesthetically pleasing than other types of movable bridges. One might ask, however, whether these advantages are worthy of putting up with the additional issues, particularly in regards to stabilizing the constructions under live fill.

Double leaf bascule bridges, more so than almost every other movable bridge types, frequently have problems with seating. These problems come up from several options. The bridge may be taking live loads bigger than those created for, overstressing the support system. The bridge stabilizing devices may have suffered deterioration so that they cannot contain the forces imposed about them. The bridge stabilizing devices may be incorrectly adjusted in order that they do not perform their intended function. The entities which donate to stability of an two times leaf bascule include: live load shoes which form ceases for each and every moving leaf as it attains its sitting position; middle or shear locks forming a vertical tie between the two leaves of an two times leaf bascule bridge when in the sealed position; live weight anchors which can handle exerting a downward pressure at the rear of bridge counterweight; tail hair Which form a shear connection at or close to the rear end of the bridge counterweight, and adjustment of the balance of the moving leaf about its axis of rotation.

Bascule is French for see-saw. All modern bascule bridges contain a huge moving mass of superstructure, deck, and counterweight, that can be considered well balanced for structural purposes. The span can be considered essentially rigid for controlling purposes, as it rotates between exposed and finished positions. This can be applied whether it's a straightforward trunnion leaf, or a rolling lift of the Scherzer or Ball type. In addition, it applies to the countless variations on the articulated counterweight type, as developed by Strauss and more, with the counterweight pivoting about an axis or arc independent from the bridge leaf. An exception to this guideline are bascules with functioning struts or ropes such as many heel trunnions, some early on Scherzer rolling lifts, and more, which do not add simply to the balancing calculations, as they move in a different course than the superstructure. The operating strut could be heavy enough to have a noticeable effect on the total amount, but this usually only happens with solo leaf railroad bridges. Heel trunnion and articulated counterweight bascule bridges contain the counterweight rotating about an axis individual from the leaf itself. The counterweight is usually in a fixed position in regards to to gravitational second relative to the bascule span on these bridges, due to the parallelogram design of the pivot factors.

Double leaf bascule bridges become unstable because they're poorly designed, terribly constructed, or improperly maintained. These are more susceptible to deficiencies from these causes because they're more sensitive than other common types of movable bridges. It's very difficult to correct the faults of a poorly designed bridge, but sometimes possible to correct construction defects. It is very difficult to correct the results of poor maintenance except by changing the components affected. An adequately designed double leaf bascule bridge should be very rigid, specifically in regard to primary live load deflections.

The leaves of the two times leaf bascule should be solidly supported on very sturdy live fill shoes located adjacent to the pier sea wall membrane, as far as possible from the guts of rotation.

The balance of the double leaf bascule should be in a way that a dead weight reaction is present on the live fill shoes, when the bridge is closed down, that is substantially more than any possible negative effect, from live load or other options. The roadway areas of the dual leaf bascule should be shaped so that there surely is no misalignment at the joints, either at the heels of the leaves or at the feet. This applies to account as well as elevation - the vertical curve should be constant in one leaf to the other and from each leaf to its strategy. Tail locks should be provided as a back up to the stabilization achieved by controlling. The tail hair should firmly understand the tail end of each leaf with minimal clearances and keep it in the closed position. This will eliminate the possibility of drive machinery being damaged anticipated to live load deflection.

  • BRIDGE DESIGN IN THIRD Viewpoint OF PROJECTION:
  • CONCLUSION AND RECCOMENDATION:

Double leaf bascule bridges become unpredictable because they are poorly designed, badly constructed, or poorly maintained. They are really more vunerable to deficiencies from these causes because they are more sensitive than other common types of movable bridges. It's very difficult to improve the faults of your poorly designed bridge, but sometimes possible to correct construction defects. It's very difficult to improve the results of poor maintenance except by exchanging the components influenced. A properly designed double leaf bascule bridge should be very rigid, specifically in regards to primary live fill deflections.

The leaves of the double leaf bascule should be solidly reinforced on very sound live insert shoes located next to the pier sea wall structure, as far as possible from the guts of rotation.

The balance of the two times leaf bascule should be in a way that a dead load reaction exists on the live load shoes, when the bridge is finished, that is substantially more than any possible negative reaction, from live weight or other resources. The roadway floors of the two times leaf bascule should be created so that there is no misalignment at the joint parts, either at the heels of the leaves or at the toes. This pertains to account as well as elevation - the vertical curve should be continuous in one leaf to the other and from each leaf to its strategy. rail hair should be provided as a back up to the stabilization achieved by controlling. The tail locks should firmly understand the tail end of every leaf with minimum clearances and keep it in the closed position. This will likely eliminate the likelihood of drive machinery being harmed lue to reside load deflection.

Movable bridges have been an important part of the nation's infrastructure for years and years. They present unique difficulties to the structural engineer and require intensive coordination of the structural, mechanised, and electric powered systems to achieve a durable and operationally reliable composition.

FINAL PROJECT:

  • REFERENCES:

http://en. wikipedia. org/wiki/Bascule_bridge

http://heavymovablestructures. org/belongings/technical_papers/00525. pdf

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