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| fabformwiki:research:research_efforts [2023/10/11 18:42] – [Conclusions and Further Research] rpschmitz | fabformwiki:research:research_efforts [2023/10/19 15:00] (current) – [Research Papers] rpschmitz |
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| <fs medium>The shape a wall panel could take was first explored using a plaster model with various interior support and perimeter boundary conditions (Figures 1-2). The cloth fabric, when draped over interior supports and secured at the perimeter, deforms as gravity forms the shape of the panel with the fluid plaster as shown in the completed plaster casts (Figure 3). Once a satisfactory design has been obtained, a full scale cast with concrete can be made.</fs> | <fs medium>The shape a wall panel could take was first explored using a plaster model with various interior support and perimeter boundary conditions (Figures 1-2). The cloth fabric, when draped over interior supports and secured at the perimeter, deforms as gravity forms the shape of the panel with the fluid plaster as shown in the completed plaster casts (Figure 3). Once a satisfactory design has been obtained, a full-scale cast with concrete can be made.</fs> |
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| <fs medium>The casting of a full scale panel using concrete requires finding a fabric capable of supporting the weight of the wet concrete. For this purpose, a geotextile fabric made of woven polypropylene fibers was utilized. Assorted interior supports were added to the formwork (Figure 4) and the flexible fabric material was pre tensioned at the perimeter (Figure 5). Depending upon the configuration of these interior support conditions, three dimensional funicular tension curves are produced in the fabric as it deformed under the weight of the wet concrete (Figure 6). Reinforcement added to the panel only served to hold it together and was not designed for any particular loading condition for the completed panel (Figures 7 and 8) Figure 9 shows the formwork used for the completed wall panel shown in Figure 10. Alternatively a completed wall panel may also serve as a form. The glass fiber reinforced concrete (GFRC) wall panel shown in Figure 11 was cast on the finished surface of the panel Shown in Figure 10.</fs> | <fs medium>The casting of a full-scale panel using concrete requires finding a fabric capable of supporting the weight of the wet concrete. For this purpose, a geotextile fabric made of woven polypropylene fibers was utilized. Assorted interior supports were added to the formwork (Figure 4) and the flexible fabric material was pre tensioned at the perimeter (Figure 5). Depending upon the configuration of these interior support conditions, three-dimensional funicular tension curves are produced in the fabric as it deformed under the weight of the wet concrete (Figure 6). Reinforcement added to the panel only served to hold it together and was not designed for any particular loading condition for the completed panel (Figures 7 and 8) Figure 9 shows the formwork used for the completed wall panel shown in Figure 10. Alternatively a completed wall panel may also serve as a form. The glass fiber reinforced concrete (GFRC) wall panel shown in Figure 11 was cast on the finished surface of the panel Shown in Figure 10.</fs> |
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| <fs medium>We believe however, until new fabrics are developed the benefits of using geotextiles far outweighs any disadvantages.</fs>\\ | <fs medium>We believe however, until new fabrics are developed the benefits of using geotextiles far outweighs any disadvantages.</fs>\\ |
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| ===== Engineering Complex Forms ===== | ===== Engineering Complex Forms ===== |
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| <fs large>See [[fabformwiki:research:usa:usa_schmitz|USA_Schmitz]] for current research efforts.</fs> | <fs large>See [[fabformwiki:research:usa:usa_schmitz|USA_Schmitz]] for current research efforts.</fs> |
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| ===== International Research ===== | ===== International Research ===== |
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| <align justify><fs medium>While the list of countries conducting research into the use of fabric as a formwork for architectural works continues to grow, the research at [[fabwiki:research:canada:canada_research|C.A.S.T.]] has been the most innovative and pioneering effort the author has seen to date. Their research centers on the development of new technologies for forming concrete structural members using fabric formworks. They seek to:</fs></align> | ### |
| | <fs medium>While the list of countries conducting research into the use of fabric as a formwork for architectural works continues to grow, the research at [[fabformwiki:research:canada:canada_research|C.A.S.T.]] has been the most innovative and pioneering effort the author has seen to date. Their research centers on the development of new technologies for forming concrete structural members using fabric formworks. They seek to:</fs> |
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| * <fs medium>Find new simple and efficient forming strategies using standard tools and fasteners for all the architectural applications mentioned above.</fs> | * <fs medium>Find new simple and efficient forming strategies using standard tools and fasteners for all the architectural applications mentioned above.</fs> |
| * <fs medium>“…. make these new technologies available to both high and low capital building cultures.” (C.A.S.T. brochure)</fs>\\ | * <fs medium>“…. make these new technologies available to both high and low capital building cultures.” (C.A.S.T. brochure)</fs>\\ |
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| <align justify><fs medium>In addition to the fabric-formed precast concrete wall panels previously mentioned they have explored and continue to explore fabric-formed beams, trusses, columns, vaults and shotcrete thin-shell curtain wall systems.</fs></align> | ### |
| | <fs medium>In addition to the fabric-formed precast concrete wall panels previously mentioned they have explored and continue to explore fabric-formed beams, trusses, columns, vaults and shotcrete thin-shell curtain wall systems.</fs> |
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| {{gallery> fabwiki:research:international_research:fig_1-15?200x200&5&showtitle&lightbox }} | {{gallery> fabformwiki:research:international_research:fig_1-15?200x200&5&showtitle&lightbox }} |
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| <align justify><fs medium>C.A.S.T. students explore full-scale construction techniques by first modeling them in plaster (Figures 1 - 4) and then casting them in concrete at full-scale (Figures 5 - 13). And as part of the engineering research being done at C.A.S.T. Ph.D. students are conducting structural tests on variable section beams and trusses as well (Figures 14 and 15). Variable section beams in general and the ‘pinch’ beam in particular (Figure 8), by using one-third the concrete of an equivalent rectangular beam, can offer a substantial savings in the amount of materials required for construction contributing to a more efficient and sustainable design.</fs></align> | ### |
| | <fs medium>C.A.S.T. students explore full-scale construction techniques by first modeling them in plaster (Figures 1 - 4) and then casting them in concrete at full-scale (Figures 5 - 13). And as part of the engineering research being done at C.A.S.T. Ph.D. students are conducting structural tests on variable section beams and trusses as well (Figures 14 and 15). Variable section beams in general and the ‘pinch’ beam in particular (Figure 8), by using one-third the concrete of an equivalent rectangular beam, can offer a substantial savings in the amount of materials required for construction contributing to a more efficient and sustainable design.</fs> |
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| {{gallery> fabwiki:research:international_research:fig_16-21?200x200&5&showtitle&lightbox }} | {{gallery> fabformwiki:research:international_research:fig_16-21?200x200&5&showtitle&lightbox }} |
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| <align justify><fs medium>Simple, flat rectangular sheets of fabric are also being used to explore the shapes columns might take (Figures 16 - 20). And while structural efficiency may not play a major role in their design their appearance is anything but boring as they can take on a very sculptural look (Figure 21).</fs></align> | ### |
| | <fs medium>Simple, flat rectangular sheets of fabric are also being used to explore the shapes columns might take (Figures 16 - 20). And while structural efficiency may not play a major role in their design their appearance is anything but boring as they can take on a very sculptural look (Figure 21).</fs> |
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| <align justify><fs medium>Most recently C.A.S.T. research has focused on thin-shell concrete vaults formed from fabric molds. These vaults can themselves serve as molds for stay-in-place formwork pans or glass fiber reinforced concrete (GFRC) applications. Their innovative work closely follows methods of funicular shell formation first pioneered by Heinz Isler. Isler used small scale funicular models to determine full-scale geometry and structural behavior of reinforced concrete thin-shell structures.</fs></align> | |
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| {{gallery> fabwiki:research:international_research:fig_22-25?200x200&4&showtitle&lightbox }} | ### |
| | <fs medium>Most recently C.A.S.T. research has focused on thin-shell concrete vaults formed from fabric molds. These vaults can themselves serve as molds for stay-in-place formwork pans or glass fiber reinforced concrete (GFRC) applications. Their innovative work closely follows methods of funicular shell formation first pioneered by Heinz Isler. Isler used small scale funicular models to determine full-scale geometry and structural behavior of reinforced concrete thin-shell structures.</fs> |
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| <align justify><fs medium>Fabric sheets are allowed to deflect into naturally occurring funicular geometries, producing molds for lightweight funicular compression vaults and double curvature wall panels. Figures 22 thru 25 show the process of taking that pure funicular tension geometry and inverting it to produce pure funicular compression geometry, a most efficient structural shape. And, as a method of construction, inverse casts can also reduce the amount of concrete used and as a result the dead weight superimposed on the supporting structural members below. It should be noted here however, that in order for the compression vault to carry a uniform load the fabric formwork membrane must also be loaded uniformly. Other loading conditions can be accommodated by altering the load placed on the membrane to reflect the design load which automatically alters the membrane’s geometry accordingly.</fs></align> | |
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| {{gallery> fabwiki:research:international_research:fig_26-31?200x200&4&showtitle&lightbox }} | {{gallery> fabformwiki:research:international_research:fig_22-25?200x200&4&showtitle&lightbox }} |
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| <align justify><fs medium>Creating formwork intended for thin-shell GFRC stay-in-place formwork pans for CIP floor slabs or thin-shell funicular compression vaults also shows great promise. Figures 26 thru 29 show the process of creating the prototype funicular fabric-formed mold. The use of GFRC stay-in-place formwork pans for a CIP floor slab system shown in Figure 30 allows the slab to span between integral support beams in pure compression. The reduction of construction materials including those consumed in formwork, concrete and reinforcement along with a reduction in the deadweight of the system all help to contribute to structural sustainability.</fs></align> | ### |
| | <fs medium>Fabric sheets are allowed to deflect into naturally occurring funicular geometries, producing molds for lightweight funicular compression vaults and double curvature wall panels. Figures 22 thru 25 show the process of taking that pure funicular tension geometry and inverting it to produce pure funicular compression geometry, a most efficient structural shape. And, as a method of construction, inverse casts can also reduce the amount of concrete used and as a result the dead weight superimposed on the supporting structural members below. It should be noted here however, that in order for the compression vault to carry a uniform load the fabric formwork membrane must also be loaded uniformly. Other loading conditions can be accommodated by altering the load placed on the membrane to reflect the design load which automatically alters the membrane’s geometry accordingly.</fs> |
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| <align justify><fs medium>Fabric-formed rigid molds required the production of a new fabric that allowed concrete to adhere to one side but not the other. High density fabrics woven from polyethylene or polypropylene can be manufactured with a smooth coating on one side and a fuzzy non woven fabric welded to the other. Concrete placed against the smooth coated side will release without the use of release agents but adhere to the fuzzy non woven side (Figure 31).</fs></align> | {{gallery> fabformwiki:research:international_research:fig_26-31?200x200&4&showtitle&lightbox }} |
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| {{gallery> fabwiki:research:international_research:fig_32-41?200x200&5&showtitle&lightbox }} | ### |
| | <fs medium>Creating formwork intended for thin-shell GFRC stay-in-place formwork pans for CIP floor slabs or thin-shell funicular compression vaults also shows great promise. Figures 26 thru 29 show the process of creating the prototype funicular fabric-formed mold. The use of GFRC stay-in-place formwork pans for a CIP floor slab system shown in Figure 30 allows the slab to span between integral support beams in pure compression. The reduction of construction materials including those consumed in formwork, concrete and reinforcement along with a reduction in the deadweight of the system all help to contribute to structural sustainability.</fs> |
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| <align justify><fs medium>Another vault option being explored is a direct-cast fabric-formed thin-shell vault that can span between abutments in a beamlike fashion. These members are formed using a single flat rectangular sheet of fabric simply hung from a perimeter frame and used as a mold to form a double curvature vault. Figures 32 thru 35 show the process of creating double curvature funicular thin-shell vault shape. Using a carbon fiber grid in lieu of conventional reinforcing steel allows for a creation of a very thin section – only 3cm (1.2 in.) thick (Figure 36). Figures 37 thru 40 show the process of creating double curvature lenticular thin-shell vault shape. The completed vaults, as shown in Figures 36 and 41, would certainly enhance the appearance of any enclosed space. C.A.S.T. has created a number of variations in vault construction using this fabric formed approach; see their website for further information.</fs></align> | ### |
| | <fs medium>Fabric-formed rigid molds required the production of a new fabric that allowed concrete to adhere to one side but not the other. High density fabrics woven from polyethylene or polypropylene can be manufactured with a smooth coating on one side and a fuzzy non-woven fabric welded to the other. Concrete placed against the smooth coated side will release without the use of release agents but adhere to the fuzzy non-woven side (Figure 31).</fs> |
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| {{gallery> fabwiki:research:international_research:fig_42-46?200x200&5&showtitle&lightbox }} | {{gallery> fabformwiki:research:international_research:fig_32-41?200x200&5&showtitle&lightbox }} |
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| <align justify><fs medium>Another approach to forming thin-shell panels from sheets of fabric is to hang them and spray them with GFRC. The double curvature shapes a hanging sheet takes will naturally provide stiffness and strength to a thin concrete shell panel (Figures 42 - 46). Again, GFRC may be the best material choice as the random fiber reinforcing can give the concrete the flexural strength and ductility needed to resist superimposed loads.</fs></align> | ### |
| | <fs medium>Another vault option being explored is a direct-cast fabric-formed thin-shell vault that can span between abutments in a beamlike fashion. These members are formed using a single flat rectangular sheet of fabric simply hung from a perimeter frame and used as a mold to form a double curvature vault. Figures 32 thru 35 show the process of creating double curvature funicular thin-shell vault shape. Using a carbon fiber grid in lieu of conventional reinforcing steel allows for a creation of a very thin section – only 3cm (1.2 in.) thick (Figure 36). Figures 37 thru 40 show the process of creating double curvature lenticular thin-shell vault shape. The completed vaults, as shown in Figures 36 and 41, would certainly enhance the appearance of any enclosed space. C.A.S.T. has created a number of variations in vault construction using this fabric formed approach; see their website for further information.</fs> |
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| <align justify><fs medium>The engineering of these complex and exotic vault and thin-shell panel shapes will require an approach different than the form-finding approach described above for a horizontal fabric formed precast panel. Whereas Isler tested small scale models of his shell structures and then scaled them up to full size these vaults and thin-shell wall panels may already be at full-scale before they are put to use. Two approaches to the engineering analysis of these thin-shell panel shapes might be considered. One is a photographic method using a commercially available software program called PhotoModeler® Scanner [7]. This program imports images from a digital camera to create a dense point cloud and mesh data which can be exported to FEA software. Another method might be to use High Definition Laser Scanning which also creates a dense point cloud and mesh data which can be exported to FEA software. Both approaches will involve an iterative process where one would first image the basic member shape and then analyze it for the superimposed design loads. Results of the first analysis would show where weak points in the member occur. Further analysis would suggest to what degree the member needs to be built-up using additional textile reinforcement and concrete materials.</fs></align> | {{gallery> fabformwiki:research:international_research:fig_42-46?200x200&5&showtitle&lightbox }} |
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| | <fs medium>Another approach to forming thin-shell panels from sheets of fabric is to hang them and spray them with GFRC. The double curvature shapes a hanging sheet takes will naturally provide stiffness and strength to a thin concrete shell panel (Figures 42 - 46). Again, GFRC may be the best material choice as the random fiber reinforcing can give the concrete the flexural strength and ductility needed to resist superimposed loads.</fs> |
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| | <fs medium>The engineering of these complex and exotic vault and thin-shell panel shapes will require an approach different than the form-finding approach described above for a horizontal fabric formed precast panel. Whereas Isler tested small scale models of his shell structures and then scaled them up to full size these vaults and thin-shell wall panels may already be at full-scale before they are put to use. Two approaches to the engineering analysis of these thin-shell panel shapes might be considered. One is a photographic method using a commercially available software program called PhotoModeler® Scanner [7]. This program imports images from a digital camera to create a dense point cloud and mesh data which can be exported to FEA software. Another method might be to use High Definition Laser Scanning which also creates a dense point cloud and mesh data which can be exported to FEA software. Both approaches will involve an iterative process where one would first image the basic member shape and then analyze it for the superimposed design loads. Results of the first analysis would show where weak points in the member occur. Further analysis would suggest to what degree the member needs to be built-up using additional textile reinforcement and concrete materials.</fs> |
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| ===== Conclusions and Further Research ===== | ===== Conclusions and Further Research ===== |
| <fs medium>We hope this article has piqued your interest and left you inspired. Readers interested in additional information are encouraged to visit the websites listed under Further information especially, the [[http://www.umanitoba.ca/cast_building/|C.A.S.T.]] website at the University of Manitoba where numerous examples and literature on this topic may be found.</fs> | <fs medium>We hope this article has piqued your interest and left you inspired. Readers interested in additional information are encouraged to visit the websites listed under Further information especially, the [[http://www.umanitoba.ca/cast_building/|C.A.S.T.]] website at the University of Manitoba where numerous examples and literature on this topic may be found.</fs> |
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| ===== Research Papers ===== | ===== Research Papers ===== |
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| ===== References ===== | ===== References ===== |
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