BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the construction of arched structures and, in particular, to a formwork for use in the construction of arched structures and a method of constructing arched structures.
2. Description of the Related Art
It is known to use arched structures in bridges, culverts, sewers and tunnels among other things. Traditionally, arched structures were constructed by successively setting voussiors until a central voussior or keystone can be set. The arched structure then becomes complete and self-supporting. Compressive forces hold the voussiors together in a state of equilibrium and, in theory, may provide the arched structure with an indefinite lifespan. Arched structures constructed during the time of the Roman Empire still stand today. There are however significant limitations to traditional methods of constructing arched structures, the foremost being the time consuming processes of setting the voussiors and moving a formwork forward to lengthen the arched structure.
Following the development of modern hydraulic cement, and the increased use of concrete in construction, arched structures are now typically constructed by casting concrete on arch shaped linings. This allows for the rapid construction of arched structures of varying lengths. However, concrete cast arched structures often required reinforcement bars to resist forces other than compressive forces. This limits the lifespan of concrete cast arched structures as even epoxy coated, galvanized and stainless steel reinforcement bars eventually corrode. Corrosion of the reinforcement bars may lead to the cracking, spalling and ultimately structural failure of the arched structure.
There is accordingly a need for an improved system and method of constructing arched structures.
SUMMARY OF THE INVENTION
There is provided a formwork for constructing an arched structure. The formwork comprises a first end, a second end, and a plurality of longitudinal members extending between the first end of the formwork and the second end of the formwork. The longitudinal members are arranged in an arched formation and the longitudinal members slope between the first end of the formwork and the second end of the formwork. The first end and second end of the formwork may each include an end panel with an arcuate peripheral edge.
The formwork may have rollers mounted along the longitudinal members. There may be a longitudinal base member extending between the first end of the formwork and the second end of the formwork. The longitudinal base member may be releasably connected to second end of the formwork, and a slope of at least one of the longitudinal members may be adjusted by repositioning the longitudinal base member relative the second end of the formwork.
The formwork may also have an actuator or vibrator for imparting movement to a least one of the longitudinal members. There may be a plurality of radially extending struts at a first end of the formwork. Each of the longitudinal members may be coupled to a corresponding one of the radially extending struts. The actuator may couple at least one of the longitudinal members to a corresponding one of the radially extending struts. The actuator may move the said at least one longitudinal member relative to the said corresponding one of the radially extending struts.
An alternative embodiment of the formwork comprises a first end, a second end, and an arched surface extending between the first end of the formwork and the second end of the formwork. The arched surface slopes between the first end of the formwork and the second end of the formwork. The formwork may include a longitudinal base member extending between the first end of the formwork and the second end of the formwork. The longitudinal base member may be releasably connected to the second end of the formwork, and a slope of the arched surface may be adjusted by repositioning the longitudinal base member relative to the second end of the formwork.
There is also provided a method of constructing an arched structure comprising:
- a) providing a formwork having a first end, a second end, and longitudinal member extending between the first end of the formwork and the second end of the formwork, wherein the longitudinal member slopes downwardly from the first end of the formwork to the second end of the formwork;
- b) using the formwork to support placing a plurality of interlocking voussiors and keystones during the constructing of a portion of the arched structure; and
- c) pulling the formwork out of the portion of the arched structure after the interlocking voussiors and keystones are placed, wherein the formwork is pulled out of the portion of the arched by the first end of the formwork to cause the voussiors to move inward and the keystones downward and thereby causing the voussiors and the keystones to interlock.
The formwork may be provided with an actuator or vibrator. The actuator or vibrator may be used to impart movement to the longitudinal member to cause offset voussiors to be set. Tension straps may be extended along an extrados of the arched structure to prevent outward movement of the voussiors. Tensions straps may also or alternatively be extended along an intrados of the arched structure to prevent inward movement of the voussiors. The arched structure may be provided with a lining and, in one embodiment, the extrados of the arched structure may be provided with an epoxy lining.
BRIEF DESCRIPTIONS OF DRAWINGS
The invention will be more readily understood from the following description of the embodiments thereof given, by way of example only, with reference to the accompanying drawings, in which:
FIG. 1 is a perspective view showing a first embodiment of an improved formwork for use in the construction of an arched structure;
FIG. 2 is an elevation view showing the formwork of FIG. 1 mounted on a vehicle;
FIG. 3 is a perspective view showing the formwork of FIG. 1 mounted on the vehicle and a partially constructed arched structure;
FIG. 4 is a side elevation view of the embodiment of FIG. 3;
FIG. 5 is a top plan view of the embodiment of FIG. 3;
FIG. 6 is another perspective view showing the formwork of FIG. 1 and a partially constructed arched structure;
FIG. 7 is a side elevation view of the embodiment of FIG. 6;
FIG. 8 is a top plan view of the embodiment of FIG. 6;
FIG. 9 is a yet another perspective view showing the formwork of FIG. 1 and a partially constructed arched structure;
FIG. 10 is a perspective view showing an arched structure constructed using the formwork of FIG. 1;
FIG. 11 is a perspective view showing an arched structure constructed using the formwork of FIG. 1 with the addition of ground filler over the structure;
FIG. 12 is a perspective view showing a second embodiment of an improved formwork for use in the construction of an arched structure and a partially constructed arched structure;
FIG. 13 is front elevation view of the partially constructed arched structure of FIG. 12 showing a lining coating the arched structure; and
FIG. 14 is a perspective view showing a third embodiment of an improved formwork for use in the construction of an arched structure and a partially constructed arched structure.
DESCRIPTIONS OF THE PREFERRED EMBODIMENTS
Referring to the drawings and first to FIG. 1, a first embodiment of an improved formwork 10 for use in the construction of an arched structure is shown. The formwork 10 includes a plurality of longitudinal members, for example longitudinal members 12a, 12b and 12c, which extend between end panels 14 and 16. The longitudinal members are substantially similar in structure and function. Accordingly, only one of the longitudinal members 12a is described in detail herein with the understanding that the remaining longitudinal members have a substantially similar structure and function in a substantially similar manner. The longitudinal member 12a has a plurality of spaced apart rollers, for example rollers 18a, 18b, 18c and 18d, disposed along a length thereof. In this example, the rollers are mounted as opposed pairs. Roller 18a is mounted on a first side 20 of the longitudinal member 12a opposite roller 18b which is mounted on a second side 22 of the longitudinal member 12a. Likewise roller 18c is mounted on the first side 20 of the longitudinal member 12a opposite roller 18d which is mounted on the second side 22 of the longitudinal member 12a. The longitudinal member 12a is secured to each of the end panels 14 and 16 by a corresponding bolt 24 and 26. This allows the longitudinal member 12a to be easily removed or replaced.
The end panels 14 and 16 are generally semicircular with the longitudinal members 12a, 12b and 12c being secured to the end panels 14 and 16 near respective arched peripheral edges 28 and 30 thereof. The longitudinal members 12a, 12b and 12c are thereby arranged in a generally arcuate formation providing the formwork 10 with an arcuate profile. Referring now to FIG. 2, the end panels 14 and 16 are vertically offset such that a front one of the end panels 14 has a higher profile than a rear one of the end panels 16. This provides the formwork 10 with a slope θ running downwardly from the front end panel 14 to the rear end panel 16. The slope θ may be adjusted by repositioning where a longitudinal base member 32 is secured to the rear end panel 16. This may readily be done by removing bolt 34 to allow the longitudinal base member 32 to be repositioned and then reinserting bolt 34 to secure the repositioned longitudinal base member 32 to the rear end panel 16. It will be understood by a person skilled in the art that a second longitudinal base member (not shown in FIG. 2), which is coplanar with the longitudinal base member 32 shown in FIG. 2, must also be similarly repositioned.
In use the formwork 10 is typically mounted on a vehicle 36 and, as shown in FIGS. 3 to 5, the arcuate profile of formwork 10 supports a plurality of voussiors, for example voussiors 38a, 38b, 38c and 38d, and keystones, for example keystones 40a and 40b, during the construction of an arched structure 42. Any suitable type of interlocking voussiors and keystones may be used although, in this example, the voussiors and keystones are similar to the type disclosed in U.S. Pat. No. 6,391,797 which issued to Drew on Aug. 23, 2005 and the full disclosure of which is incorporated herein by reference. The voussiors and keystones are substantially similar in structure and function. Accordingly, only one of the voussiors 38a and one of the keystones 40a is described in detail herein with the understanding that the remaining voussiors and keystones have a substantially similar structure and function in a substantially similar manner.
The voussior 38a includes recesses 37a and protrusions 39a. In this example the recesses and protrusions are cross shaped. The recesses 37a of the voussior 38a receive corresponding protrusions 39b and 39c of adjacent voussiors 38a and 38b. One of the protrusions 39a of the voussiors 38a is shown in greater detail in FIG. 5. The protrusions 39a of the voussior 38a engage a corresponding recess 41a of the keystone 40a, as best shown in FIG. 3. This allows the voussiors and keystones to interlock, thereby preventing slippage and stabilizing the arched structure 42. The arched structure 42 also includes a plurality of imposts 44a and 44b which are not supported by the formwork 10 but also function to support the voussiors as is known in the art. The imposts 44a and 44b are provided with similar recesses and protrusions (not shown) to allow for interlocking with other imposts and the voussiors.
The arched structure 42 is further constructed, as shown in FIGS. 6 to 8, by setting additional voussiors, for example voussiors 38e, 38f, 38g and 38h, and keystones, for example keystones 40c and 40d, towards the front panel 12 of the formwork 10. Completed portions of the arched structure 42 may be reinforced with tension straps 44 extending along an extrados of the arched structure 42 to prevent outward movement of the voussiors. The tension straps 44 may extend through connectors 46 in the voussiors which, in this example, are lugs formed of metal embedded in the concrete at the time the voussiors are cast. The arched structure 42 may also be provided with a radial opening 48 at a top thereof.
As best shown in FIG. 6, when the keystones 40c and 40d are set towards the front panel 16 of the formwork 10, there are gaps 50 and 52 between the keystones 40c and 40d and their engaging voussiors 38e, 38f, 38g and 38h. The gaps 50 and 52 allow the keystones 40c and 40d to be set between opposing voussiors despite the protrusions (not shown in detail in FIG. 6) on the voussiors. As shown in FIG. 9, as the formwork 10 is moved forward by the vehicle 36 in the direction generally indicated by arrow 100, the keystones 40c and 40d interlock with the voussiors 38e, 38f, 38g and 38h. This is a function of the slope θ, shown in FIG. 2, of the formwork 10.
A front portion 54 of the formwork 10 pushes the voussiors 38e, 38f, 38g and 38h outward to allow the keystones 40c and 40d to be set. However, since the formwork 10 slopes downwardly towards a rear portion 56 thereof, as the vehicle 36 moves in the direction of arrow 100 the voussiors move inward due to gravity and the keystones 40c and 40d move downward due gravity. This allows voussiors and keystones to interlock. Accordingly, as the formwork 10 is moved forward in the direction of arrow 100, the relative positions of the voussiors 38e, 38f, 38g and 38h is shifted from the front portion 54 of the formwork 10, as shown in FIG. 6, to the rear portion 56 of the formwork 10, as shown in FIG. 9, thereby allowing the voussiors and keystones to interlock and the arched structure to be completed. Mounting the formwork 10 on a vehicle 36 allows the formwork to be readily moved forward. Mounting the formwork 10 on the vehicle 34 also allows a length of the arched structure 40 to be easily extended by simply moving the vehicle forward and setting additional voussiors on the then exposed formwork 10.
FIG. 10 shows the completed arched structure 42 which may further be reinforced with tension straps 58 extending along an intrados of the arched structure 42 to prevent inward movement of the voussiors. FIG. 11 shows the completed arched structure 42 buried under ground filler 62. The radial opening 48 allows access to the arched structure 42 upon removal of a cover 64 which is provided for safety reasons.
Referring now to FIG. 12, a second embodiment of an improved formwork 70 for use in the construction of an arched structure 72 is shown. The second embodiment of the formwork 70 is generally similar to the first embodiment of the formwork 10. The second embodiment of the formwork 70 however has a plurality of radial struts, for example radial strut 74, extending from the end panel 76. The radial struts are substantially similar in structure and function. Accordingly, only one radial strut 74 is described in detail herein with the understanding that the remaining radial struts have a substantially similar structure and function in a substantially similar manner. The radial strut 74 is coupled to a corresponding longitudinal member 78 which is similar to the longitudinal member 12a shown in FIG. 1. In particular, and as shown in FIG. 12, an actuator 80 couples the radial strut 74 to the longitudinal member 78. This allows motion to be imparted to individual ones of the longitudinal members, and thereby to the arched structure 72 to cause offset voussiors to be set. In this example, the actuator is a hydraulic actuator 80 with a hydraulic cylinder 82 secured to the radial strut 74 and a piston rod 84 coupled to the longitudinal member 78. In other examples, other types of actuators or vibrators may be used.
Completed portions of the arched structure 72 may be reinforced with flattened tension strips 86 extending along an extrados of the arched structure 72 to prevent outward movement of the voussiors. The flattened tension strips 86 may extend through connectors 88 in the voussiors which, in this example, are flattened lugs formed of metal embedded in the concrete at the time the voussiors are cast. The use of flattened tension strips and flattened lugs allow the extrados of the arched structure 72 to be coated with a lining 73 as shown in FIG. 13. The lining 73 may be an epoxy lining that may be sprayed-on, coated-on, or rolled-on using self-adhesive pads. The lining 73 may provide seismic resistance, exterior support, and waterproofing.
Referring now to FIG. 14, a third embodiment of an improved formwork 90 for use in the construction of an arched structure is shown. The third embodiment of the formwork 90 is generally similar to the first embodiment of the formwork 10. The third embodiment of the formwork 90 however does not have a plurality of longitudinal members extending between the end panels. Instead the third embodiment of the formwork 90 has a single longitudinal member in the form of a sloped arched surface 92 formed from a slippery composite material extending between the end panels.
It will be understood by a person skilled in the art that terms “front”, rear”, “higher”, “lower”, “forward” and “downward” are used herein are used only in relation to the position and orientation of the formwork as shown in the drawings.
It will also be understood by a person skilled in the art that many of the details provided above are by way of example only, and are not intended to limit the scope of the invention which is to be determined with reference to the following claims.
Patent Application
20120233934
