AU2016202790A1

AU2016202790A1 - A silo

Info

Publication number: AU2016202790A1
Application number: AU2016202790A
Authority: AU
Inventors: Bart DEGREEF; Edouard RENNEVILLE
Original assignee: Soletanche Freyssinet SA
Current assignee: Soletanche Freyssinet SA
Priority date: 2015-04-29
Filing date: 2016-04-29
Publication date: 2016-11-17

Abstract

A silo Abstract A silo and a method of manufacturing the silo are provided. The silo comprises a base in the form of a concrete foundation slab, a round cylindrical side wall assembly 5 extending from the base, a roof extending over the side wall assembly, a roof support and a retaining edge kerb. The round cylindrical side wall assembly includes a plurality of precast concrete side wall panels, each side wall panel being formed with side edges having interengaging joint formations for engaging with adjacent side wall panels, and a plurality of post-tensioning hoop tendons located at predetermined intervals around an 10 external surface of the wall assembly. The method includes erecting the side wall panels on the foundation slab, each of the side wall panels being positioned side-by side in an interengaging configuration to form the wall assembly, externally post tensioning the wall assembly by locating the plurality of post-tensioning hoop tendons and post tensioning the hoop tendons, forming the retaining edge kerb between a lower 15 external face of the side wall assembly and the base, providing the roof support on the side wall assembly, and fitting the roof to the side wall assembly via the roof support.

Description

A silo 2016202790 29 Apr 2016

Field of the invention

This disclosure relates to a silo and to a method of manufacturing a silo.

Background of the invention 5 Silos such as grain silos are generally fabricated from steel. Steel silos are typically cylindrical in form, with the height of the cylinder being greater than its diameter. A steel roof caps the cylindrical wall, and grain enters through an opening in the apex of the roof after being dispatched through an opening at the base of the steel silo. 10 Some grain silos are also fabricated from concrete. Various solutions have been proposed depending on the characteristics of the silo and the available storage area. One type of concrete grain silo is formed from concrete wall panels which are stitched together using upper and lower ring beams. The height of this type of silo is generally limited to 6 metres. Another type of concrete silo makes use of precast reinforced 15 concrete panels which are connected together in situ by pouring vertical concrete joints. Yet another variation of concrete silo has annular concrete walls which are cast in situ, and which are generally higher than 6 metres. An internal pre-stressing system is used in the case of precast concrete wall panels or silos cast in situ, and involves the use of tendons together with the construction of buttresses to stress the tendons, and internal 20 tendon ducts to accommodate them. Such ducts are prone to misalignment.

Reference to any prior art in the specification is not an acknowledgment or suggestion that this prior art forms part of the common general knowledge in any jurisdiction or that this prior art could reasonably be expected to be understood, regarded as relevant, and/or combined with other pieces of prior art by a skilled person 25 in the art.

Summary of the invention

In one embodiment there is provided a method of manufacturing a silo comprising a base, a round cylindrical side wall assembly extending from the base and a roof extending over the side wall assembly, the method including: 1 1001439189 providing a plurality of precast concrete side wall panels, each side wall panel being formed with side edges having interengaging joint formations for engaging with adjacent side wall panels; 2016202790 29 Apr 2016 providing a base in the form of a concrete foundation slab; 5 erecting the side wall panels on the foundation slab, each of the side wall panels being positioned side-by-side in an interengaging configuration to form the wall assembly, externally post-tensioning the wall assembly by locating a plurality of posttensioning hoop tendons at predetermined intervals around an external surface 10 of the wall assembly, and post tensioning the hoop tendons, forming a retaining edge kerb between a lower external face of the side wall assembly and the base, providing a roof support on the side wall assembly, and fitting the roof to the side wall assembly via the roof support. 15 In one embodiment the side wall panels are precast with a series of interior longitudinally extending prestressing ducts for receiving pre-tensioning tendons for prestressing the panels.

The post-tensioning hoop tendons may be in the form of X-Range anchorage systems manufactured by Freyssinet, with the positioning of the hoops being determined by the 20 predicted radial loading along the height of the silo, typically using finite element analysis.

Sealing means may be provided between adjacent side wall panels for forming a sealed side wall assembly.

Kerb anchoring means may be provided for anchoring the retaining edge kerb between 25 the lower external face of the side wall assembly and the base.

The roof support may include a plurality of pre-cast capping beams which are engaged with one another to form a capping beam assembly. 2 1001439189

The method may include the step of externally post-tensioning the capping beam assembly by locating at least one post-tensioning hoop tendon around an external surface of the capping beam assembly, and post tensioning the at least one hoop tendon. 2016202790 29 Apr 2016 5 The capping beams may be formed to interengage with one another, with each capping beam spanning a plurality of side wall panels.

The capping beams may be sealingly engaged with one another and with the side wall panels.

The wall panels may be formed with apertures for accommodating kerb anchoring 10 means in the form of rebar anchors.

An outer peripheral portion of the base adjacent the external surface of the side wall assembly may be formed with apertures for receiving kerb anchoring means in the form of rebar anchors.

The invention extends to a silo manufactured in accordance with any one or more of the 15 above methods, as well as to a silo comprising: a base in the form of a concrete foundation slab a round cylindrical side wall assembly extending from the base, the round cylindrical side wall assembly including: a plurality of precast concrete side wall panels, each side wall panel being 20 formed with side edges having interengaging joint formations for engaging with adjacent side wall panels, and a plurality of post-tensioned hoop tendons located at predetermined intervals around an external surface of the wall assembly, a roof extending over the side wall assembly; 25 a roof support extending between the roof and the side wall assembly, and a retaining edge kerb formed between a lower external face of the side wall assembly and the base. 3 1001439189

The roof support may include a plurality of cast capping beams which engage with one another to form a capping beam assembly, which is post tensioned using at least one post tensioning hoop tendon system. 2016202790 29 Apr 2016

In one embodiment the foundation slab may be formed with a peripheral 5 wall-receiving recess for receiving lower edges of the side wall panels, with a sealing arrangement in the form of a rubber or elastomeric material being provided between the recess and the lower edges of the side panels for providing a seal between the side wall assembly and the foundation slab.

Sealing means in the form of rubber or elastomeric strip may be positioned 10 between adjacent side wall panels for providing a sealed configuration.

The invention extends to a grain silo installation including at least a pair of silos of the type described above, including a central tower and elevator from which a corresponding pair of conveyor trusses extend to feed grain into top openings of the silos. 15 As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to exclude further additives, components, integers or steps.

Further aspects of the present invention and further embodiments of the aspects 20 described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings.

Brief description of the drawings

Figure 1 is a side view of a grain silo installation including a pair of completed silos; 25 Figure 2 is a top plan view of the silo installation of figure 1;

Figure 3 is a schematic side view of side wall panels being cast on a bench;

Figure 4A is a front view of a side wall panel; 4 1001439189

Figure 4B is a side view of a side wall panel; 2016202790 29 Apr 2016

Figure 4C shows an end-on detail of the joint between two adjacent side wall panels;

Figure 5 shows a cross-sectional side view through a side wall assembly 5 between a base slab and a capping beam;

Figures 6A and 6B show respective side and cross-sectional views of a hoop tendon anchorage in the form of Freyssinet X-range anchors;

Figure 7 shows a cross-sectional side view detail of the connection between the side wall, the base slab and an edge kerb; 10 Figure 8A shows a cross-sectional side view of a detail of an upper connection between an upper portion of the side wall, a capping beam and a roof section,

Figure 8B shows a cross-sectional detail of a side edge profile of the edge kerb, and

Figure 9 shows a cross-sectional side view of an alternative embodiment of an 15 upper connection between a side wall and a roof section.

Detailed description of the embodiments

Referring first to Figures 1 and 2, a grain silo installation comprises a pair of silos 10 and 12 having a central tower and elevator 14 from which a pair of conveyor trusses 16 and 18 extend to feed grain into top openings 20 of the respective silos. Each of the 20 silos comprise a round cylindrical side wall assembly 22 on a cast concrete foundation or base slab 24. The round cylindrical side wall assembly comprises 64 pre-cast concrete side wall panels 22.1, 22.2, 22.3... 22.64 which are inter-engaged with one another. The side wall assembly is capped by a conical steel roof structure 25. Each silo is provided with a door 26 and a reclaim system including piping 28 may be used to 25 reclaim grain from each silo.

The precast concrete sidewall panels 22.1, 22.2... 22.64 are substantially identical in form. The thickness and number of sidewall panels is generally dictated by ease of transportation. Ideally, a 24 ton limit is provided in order to limit the size of the 5 1001439189 transport trucks. If taller and heavier panels are required, it is contemplated that in situ casting solutions may be provided. 2016202790 29 Apr 2016

Referring now to Figure 3, a schematic view of new panels 22.1 and 22.2 to be cast with intense compaction is shown. The panels rest on a precast bench 30 and 5 formwork 31 is provided for forming the profiles of the panels. It can clearly be seen in Figure 2 how each of the panels 22.1 and 22.2 are formed with tongues 32 at one end which locate within complemental grooves 34 on adjacent panels. Whereas only two panels are shown on the precast bench, it will be understood that the size of the bench is designed to be able to cast a sufficient number of panels simultaneously to arrive at I0 the most cost-effective solution. The panels are also formed with interior vertical prestressing ducts 38 into which tendons are inserted for prestressing the panels to reduce their thickness to about 300mm.

As is shown in Figures 4A and 4B, tendons 40 are passed through the preformed apertures 38. Each of the tendons may be formed from three 15.7mm diameter 15 strands having dead end anchorages 42 at one end and active anchorages 44 at the opposite end with bursting rebar and stressed vertically at 25MPa compressive strength. It will be appreciated that different sized strands (12.7mm or 15.2mm for example) and different numbers of strands may be used. In the embodiment, the panels have a width of approximately 2.76 metres and a height of 15 metres, and are 300mm >0 thick. Curvature of each panel is 5.625 degrees, as a result of which a total of 64 panels are required to complete the cylindrical side wall assembly.

Figure 4C shows the aforementioned tongue and groove joint between adjacent panels, with the joints terminating at the outer surface of the panels in recesses 45 which accommodate mastic filler or sealant 46. Mastic or a rubber strip may also be 25 provided along the width of the joints. Generally, it is desirable that the sealing here and elsewhere provides resistance to the fumigation of the grain to 200 Pascals. The pressure loss should also not be greater than 50% over 10 minutes, and this is tested for after completion of the silo.

Mesh such as RL718 (not shown) may be provided on the face of each panel, 30 and the dead end and active anchorages are adapted with lifting attachments to enable the panels to be manoeuvred and erected on site using two mobile cranes. A support 6 1001439189 system is typically installed before the erection of each panel so that it is retained in the vertical position. 2016202790 29 Apr 2016

Referring now to Figure 5, the panel 22.1 is shown resting on base slab 24. Once all 64 panels have been assembled into the side wall assembly, it is externally 5 post-tensioned using a proprietary X-Range anchorage system (1x15) developed by Freyssinet for the strengthening of cylindrical structures. The anchorage system makes use of external post-tensioning hoop tendons 48 to apply radial pressure to the cylindrical wall assembly.

Figures 6A and 6B provide more details of the X-Range anchorage system, I0 which includes a series of cast iron anchor blocks 50 which anchor corresponding greased and sheathed strands 52 in position. Each sheathed strand is formed with an FIDPE outer duct 54 which allows the strand to slide freely inside the sheath without bonding to the structure. The outer duct is injected with cement grout, and a grease nipple 56 is provided for keeping the strand greased. A threaded end cap 58 is used for 15 tightening up the strand, which is anchored using corresponding three piece wedges 60. In a more aggressive environment, where additional durability is required, galvanised tendons may be used.

Cement grout is injected into the FIDPE outer duct before tensioning of the tendon so that the greased and sheathed strand is fully embedded and a more uniform >0 pressure is applied on the concrete surface. The external tendon is then protected against corrosion by a combination of the grease protection and the FIDPE sheath and outer duct, which is filled with cementitious grout. Outside the anchorage, corrosion protection is effected by coating the anchorage with a fusion bonded nylon.

In the embodiment illustrated in Figure 5, a total of seventy 15.7mm strands are 25 used, graduated evenly from spacings of 110mm at the base of the wall, which is subjected to greater loads, in the region of 1820 KN or more, to a spacing of 1600mm at the top of the wall, where there is a load of about 21.5 KN. The cables are stressed to 80% UTS. It will be appreciated that the hoop tendons are terminated and anchored on opposite sides of the door 26 of the silo. 7 1001439189

Referring now to Figure 7, after pre-stressing has occurred using the hoop tendons 48, a series of 12mm apertures 61 are drilled at 300mm intervals around the outer periphery of the side wall assembly for receiving J-shaped rebar anchors 62, which are chemically anchored in place. Reinforcing bars 64 are fitted to the underside 5 of the anchors 62. Each of the wall panels 22.1 are formed with lower apertures defined by PVC tubes 66 at 750mm intervals for receiving lengths of rebar 68 which are grouted in place, and which project outwardly from the wall panels. 2016202790 29 Apr 2016

Once the anchors 62 and the rebars 64 and 68 are in position, a concrete nib 70 is cast in situ against the outer face of the wall panel 22A around its periphery. In the I0 embodiment, the nib is 250mm wide, and slopes down at 15 degrees to an outer height of 150mm. The nib is formed with an external waterproof coating 72 which also extends up the outer surface of the wall panel 22A for about 100mm. Waterproofing of the overall structure is also ensured by applying a damp-proof membrane 74 around the concrete base. The external waterproof coating 72 overlaps membrane 74. 15 Figure 7 also shows in more detail the internal structure of the wall panel 22.1, including the active anchorage 44 in the panel anchoring the three 15.7mm strands 40 and surrounded by an anti-burst reinforcement cage 76. RL918 mesh 28 is also used to reinforce the panel.

Referring now to Figure 8A and 8B, after the nib 70 has been formed, a series of >0 capping beams, one of which is shown at 71, are mounted securely to the top and uppermost side edges of the wall panels 22.1 to 22.64. The end caps are formed with 75mm sleeves 80 at 500mm intervals. The sleeves 80 are aligned with threaded lifting ferrules 82 extending from the upper surfaces of the wall panels. A total of sixteen curved capping beams 71 are provided, each spanning four wall panels. A 6 to 10mm 25 neoprene strip 84 is interposed between the upper surface of the wall panel 22.1 and the recess in the capping beam 71 to enhance sealing between the capping beam and the wall panel.

Threaded bars are inserted through the sleeves 80 and screwed into the lifting ferrules 82, and are then grouted into position to anchor the capping beams in place. In 30 order to further secure the structure and increase the hoop strength, a series of four 15.7mm strands 86 are passed around the outer peripheral surfaces 88 of the capping 8 1001439189 beams and are tightened using four 1x15 anchorages illustrated in Figures 6A and 6B. The steel roof structure 90 is a conventional steel framed structure which is bolted in position on the capping beams via ferrules 92 extending into the beams. As shown in Figure 8B, the capping beam 71 is formed with an end with a central recess 96 and a 5 corresponding male end 97 with a complemental central tongue 97.1, so that adjacent capping beams fit snuggly and complementally together. Mastic sealant 98 is provided in the outermost grooves 99 of adjacent capping beams. 2016202790 29 Apr 2016

Referring now to Figure 9, details of an upper end of a second embodiment of a pre-cast panel 100 is shown fitted with a ring beam arrangement 101 including steel I0 flanges 102 and 104 extending from a steel cap 106. Seals 108 are provided between the flanges and the outer surfaces of the panel of the precast concrete panel 100, and post tensioning bars 110 and 112 extend through the precast concrete panel and serve as high tensile bolts to bolt the steel cap 106 in position. A roof beam 114 has a flanged end 116 through which bolts 118 extend for securing the roof beam in position on the 15 steel cap.

For the purposes of calculating the pressure on the walls of the silo and the required post-tensioning it is necessary to carefully study and model the behaviour of the grain within the silo, as this is non-linear. As a result, the silo and grain have to be modelled using a finite element model analysis. This allows the pressure on the walls of >0 the silo to be calculated not only due to the initial grain pressure but also due to the flow grain pressure. By virtue of this analysis it is possible to extract the maximum radial pressure at a series of levels in the silo and then to determine the horizontal tension force in the silo, both at the levels and in combination. This will then determine the number of strands required per tendon, the positioning of the tendons and the spacing 25 between the tendons.

It should be noted that the pressure on the walls is not always constant for a certain height, as the silo can be empty on one side and full on the other, in particular if there is a bottom emptying system, with bottom openings that can lead to asymmetric loading, which is also calculated using the finite element analysis model. 30 It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features 9 1001439189 2016202790 29 Apr 2016 mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention. 10 1001439189

Claims

1. A method of manufacturing a silo comprising a base, a round cylindrical side wall assembly extending from the base and a roof extending over the side wall assembly, the method including: providing a plurality of precast concrete side wall panels, each side wall panel being formed with side edges having interengaging joint formations for engaging with adjacent side wall panels; providing a base in the form of a concrete foundation slab; erecting the side wall panels on the foundation slab, each of the side wall panels being positioned side-by-side in an interengaging configuration to form the wall assembly, externally post-tensioning the wall assembly by locating a plurality of posttensioning hoop tendons at predetermined intervals around an external surface of the wall assembly, and post tensioning the hoop tendons, forming a retaining edge kerb between a lower external face of the side wall assembly and the base, providing a roof support on the side wall assembly, and fitting the roof to the side wall assembly via the roof support.

2. A method according to claim 1 in which the side wall panels are precast with a series of interior longitudinally extending prestressing ducts for receiving pre-tensioning tendons for pre-stressing the panels.

3. A method according to either one of claims 1 or 2 in which the post-tensioning hoop tendons include X-Range anchorage systems of the type manufactured by Freyssinet.

4. A method according to claim 3 in which the positioning of the hoops is predetermined by the predicted radial loading along the height of the silo.

5. A method according to any one of claims 1 to 4 in which sealing means are provided between adjacent side wall panels for forming a sealed side wall assembly.

6. A method according to any one of the preceding claims in which kerb anchoring means are provided for anchoring the retaining edge kerb between the lower external face of the side wall assembly and the base.

7. A method according to any one of the preceding claims in which the roof support includes a plurality of pre-cast capping beams which are configured with operatively lower recesses for complementally engaging with the uppermost portions of the side wall panels and which are engaged with one another to form a capping beam assembly.

8. A method according to claim 7 which includes the step of externally posttensioning the capping beam assembly by locating at least one post-tensioning hoop tendon around an outer peripheral surface of the capping beam assembly, and post tensioning the at least one hoop tendon.

9. A method according to either one of claims 7 or 8 in which the capping beams are formed to interengage with one another, with each capping beam spanning a plurality of side wall panels.

10. A method according to any one of claims 7 to 9 in which the capping beams are sealingly engaged with one another and with the side wall panels.

11. A method according to claim 5 in which the wall panels are formed with apertures for accommodating kerb anchoring means.

12. A method according to claim 10 in which the kerb anchoring means comprise rebar anchors.

13. A method according to claim 12 in which an outer peripheral portion of the base adjacent the external surface of the side wall assembly is formed with apertures for receiving the rebar anchors.

14. A silo comprising: a base in the form of a concrete foundation slab a round cylindrical side wall assembly extending from the base, the round cylindrical side wall assembly including: a plurality of precast concrete side wall panels, each side wall panel being formed with side edges having interengaging joint formations for engaging with adjacent side wall panels, and a plurality of post-tensioned hoop tendons located at predetermined intervals around an external surface of the wall assembly, a roof extending over the side wall assembly; a roof support extending between the roof and the side wall assembly, and a retaining edge kerb formed between a lower external face of the side wall assembly and the base.

15. A silo according to claim 14 in which the roof support includes a plurality of cast capping beams which engage with one another to form a capping beam assembly, which is post tensioned using at least one post tensioning hoop tendon system.

16. A silo according to either one of claims 13 or 14 in which the side wall panels are precast with a series of interior longitudinally extending prestressing ducts locating pretensioning tendons for pre-stressing the panels.

17. A silo according to any one of claims 13 to 15 in which the post-tensioning hoop tendons include X-Range anchorage systems of the type manufactured by Freyssinet, with the positioning of the hoops being predetermined by the predicted radial loading along the height of the silo.

18. A silo according to any one of claims 13 to 17 in which the interengaging joint formations are tongue-and-groove formations, with recesses being formed along external faces of the joint formations for receiving sealing material.

19. A grain silo installation including at least a pair of silos according to any one of claims 13-18, a central tower and elevator from which a corresponding pair of conveyor trusses extend to feed grain into top openings of the silos.