WO2020194205A1

WO2020194205A1 - Construction method of providing prefabricated post-tensioned superstructure system

Info

Publication number: WO2020194205A1
Application number: PCT/IB2020/052800
Authority: WO
Inventors: Antonio Honki CO; Sladan JOVANCOV
Original assignee: Co Antonio Honki
Priority date: 2019-03-25
Filing date: 2020-03-25
Publication date: 2020-10-01
Also published as: PH12019050044A1

Abstract

The present invention relates to a construction method of providing a prefabricated post-tensioned superstructure system. The construction method of the present invention comprises the steps of: (a) producing pre-cast structural elements in steel molds in factory conditions; (b) transporting the pre-cast structural elements from a pre-cast plant to a building site on which at least one building is being built; (c) forming vertical joints of lower and upper columns of the prefabricated post-tensioned superstructure system using a special steel temporary equipment; (d) forming horizontal joints between vertical and horizontal structural elements of the pre-cast structural elements; (e) disassembling of the special steel temporary equipment; and (f) positioning shear walls in the at least one building relative to the pre-cast structural elements of the prefabricated post-tensioned superstructure system.

Description

CONSTRUCTION METHOD OF PROVIDING PREFABRICATED POST- TENSIONED SUPERSTRUCTURE SYSTEM

TECHNICAL FIELD

The present invention generally relates to construction methods but more particularly to a construction method of providing prefabricated post-tensioned superstructure system.

BACKGROUND ART

In the construction industry conventional method (cast in place concrete) has been wildly used. This is because designers (architects and structural engineers for example) do not pay big attention to the benefits of the owners (investors) in terms of cost-effective construction such as, for example, time of delivery and buildings safety. However, there are other opinions that designers are“more in mind on conventional way of thinking,” and at the same time, they are afraid of any“prefabricated” (i.e., “pre-cast”) idea. Additionally, for some of them, post-tensioning is also“zone that they would rather not to be involved”, due to lack of experience in this field.

Thus, from the commercial point of view for the owners (or investors), there is a need for a construction method that provides for cheaper construction, including saving in foundation, rapid assembling of building superstructure, and building’s safety.

SUMMARY OF THE INVENTION

The invention is a construction method of providing a prefabricated post- tensioned superstructure system. The construction method of the present invention comprises the steps of: (a) producing pre-cast structural elements in steel molds in factory conditions; (b) transporting the pre-cast structural elements from a pre-cast plant to a building site on which at least one building is being built; (c) forming vertical joints of lower and upper columns of the prefabricated post-tensioned superstructure system using a special steel temporary equipment; (d) forming horizontal joints between vertical and horizontal structural elements of the pre-cast structural elements; (e) disassembling of the special steel temporary equipment; and (f) positioning shear walls in the at least one building relative to the pre-cast structural elements of the prefabricated post-tensioned superstructure system.

The pre-fabricated structural elements may be concrete elements which are joined into an extremely safe and stable monolithic frame superstructure by post tensioning, done in two orthogonal directions at each floor level of the building if the building has two or more floor levels thereby bringing out the natural compressive strengthening nature of cement. As a rule, all joints are evenly exposed to the applied pressure of post-tensioning in both orthogonal directions. The prefabricated post- tensioned superstructure system of the invention is fully integrated, and all joints have capacity adequate to transfer the loads in service and in earthquake conditions.

All joints preferably have at least equal capacity as the corresponding joints of conventional cast-in-place structures. All members act as the conventionally reinforced ones (since no high compression strength develops due to the applied post-tensioning). Thus, the structure and its members behave as the ductile ones, as required by the contemporary principles of seismic resistant design. Ductile behavior of members and joints is confirmed by full-scale tests. The joints formed by post-tensioning (i.e., joints which are exposed to significant and/or optimal compression) are superior in comparison to the corresponding conventional ones.

If the seismic aspect is considered, post-tensioning of floor decks into orthogonal directions has the substantial role. Floor decks are initially exposed to the compression and integrated by post-tensioning. As the consequence of the elements fabrication and assembly method, uncontrolled construction joints, cold joints and similar imperfections (possible in case of conventional construction), cannot occur in case of the herein disclosed prefabricated post-tensioned superstructure system. Due to the above post- tensioned framework, floor decks are surely rigid in their own planes and fully capable to transfer seismic influences to the vertical elements. Superior resistance of the joints compressed by the post-tensioning has particular importance in case of the shear walls.

Several drawing figures attached to this invention show how the shear walls are incorporated into the herein disclosed prefabricated post-tensioned superstructure system. Shear capacity of joints exposed to post-tensioning is more than sufficient to integrate the shear wall with the adjacent columns. Thus, active shear wall section is also shown in two of the drawing figures attached to this invention. Bending moment generated by lateral load and affecting shear wall divides between the shear walls and columns. Proportioning of shear wall reinforcement depends on the part of bending moment that affects the shear wall. However, part of moment that affects the columns, among others possible structural elements of the building, generates additional axial forces (compression or tension) and columns are designed accordingly.

In case that the building architecture requires door (or any other openings) in the shear wall, lintel reinforcement, reinforcement on the edge of the opening, etc. is designed according to the common rules of reinforced concrete design. Shear walls are principal elements transferring seismic loads. They are cast in place concrete elements which are reinforced and concreted from the foundation up to top floor of buildings, working as some kind of “vertical cantilever.” Basically, they are located in some symmetrical composition in the buildings floor layout. Since the shear wall flexural stiffness, in comparison to the column flexural stiffness, is extreme, the major part of seismic influence is taken by the shear walls. However, in design of the prefabricated post- tensioned superstructure system, the provisions of National Structural Code of the Philippines (edition 2015) and Unified Building Code (USA), by way of examples, are fully respected. A hundred percent of design seismic forces are transferred to the entire structure including shear walls. In addition to this, according to the requirements of the mentioned codes, structural frame (columns and floor elements, without participation of shear walls) is designed to accept 25% of seismic forces. Prefabricated post-tensioned superstructure system complies also with other seismic codes.

The herein disclosed construction method may be alternatively called as PPS Building Technology (PPS BT), and may have completely different approach in comparison with different conventional construction methods. Namely, as an advanced and industrialized system, the herein disclosed construction method of providing prefabricated post-tensioned superstructure system includes production of prefabricated (pre-cast) structural elements of the building’s superstructure in the factory conditions. One of the novel aspects of the construction method of the invention is based on post tensioning procedures on the building site for connection of the vertical (e.g., columns and short pillars) structural elements and horizontal (e.g., floor slabs, cantilever floor slabs and edge girders) structural elements. The joints formed between the prefabricated structural elements by post-tensioning method create strong compression between the structural elements and provide stability and strength to a building superstructure.

Another novel aspect of the invention is the use of shear walls to address horizontal forces. The herein disclosed prefabricated post-tensioned superstructure system is a structural load bearing dual frame system, consisting of proprietary pre-cast post tensioned SMRF (or“Special Moment Resisting Frame”) plus shear walls.

BRIEF DSESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Figure 1 is a block diagram showing the active steps of the construction method of providing a prefabricated post-tensioned superstructure system. Figure 2 shows a 3D view of exemplary prefabricated post-tensioned superstructure system’ superstructures with details of tendons placing and post tensioning and with position of shear walls in accordance with one or more embodiments of the invention.

Figure 3 shows exemplary production line of pre-cast structural elements of the prefabricated post-tensioned superstructure system (columns with one, two and three- story, floor slabs with different options and shapes, cantilever floor slabs with different options and shapes, edge girders, stairs and shear walls) and a 3D view of exemplary vertical joint of columns and horizontal joint of columns and floor slabs in accordance with one or more embodiments of the invention. Figure 4 shows a view of exemplary prefabricated floor slab of the prefabricated post-tensioned superstructure system as first option in accordance with one or more embodiments of the invention.

Figure 5 shows a view of exemplary prefabricated floor slab of the prefabricated post-tensioned superstructure system as second option in accordance with one or more embodiments of the invention.

Figure 6 shows a view of the exemplary prefabricated post-tensioned superstructure system with vertical joint of columns. Figure 7 shows a view of exemplary assembly of the prefabricated post-tensioned superstructure system with simple pre-cast floor slabs and typical floor (connection by primary post-tensioning) in accordance with one or more embodiments of the invention.

Figure 8 shows a view of exemplary composite pre-cast floor slab of the prefabricated post-tensioned superstructure system consisting of two pieces in one case (connection by secondary post-tensioning) in accordance with one or more embodiments of the invention.

Figure 9 shows a view of exemplary composite pre-cast floor slab of the prefabricated post-tensioned superstructure system consisting of four pieces in another case, by use of short pillar (connection by secondary post-tensioning) in accordance with one or more embodiments of the invention.

Figure 10 shows a view of exemplary horizontal joint between pre-cast columns and floor slabs of the prefabricated post-tensioned superstructure system in accordance with one or more embodiments of the invention. Figure 11 shows a view of exemplary horizontal joint between pre-cast columns and edge girders (and/or cantilever floor slabs) of the prefabricated post-tensioned superstructure system in accordance with one or more embodiments of the invention.

Figure 12 shows a view of exemplary location of shear walls of the prefabricated post-tensioned superstructure system in some symmetrical composition in the building’s floor layout in accordance with one or more embodiments of the invention.

Figure 13 shows a view of exemplary cross section of buildings with shear walls (option A) and without shear walls (option B) of the prefabricated post-tensioned superstructure system in accordance with one or more embodiments of the invention.

Figure 14 shows a view of exemplary assembly of the pre-cast post-tensioned framework floor deck (rigid) of the prefabricated post-tensioned superstructure system in accordance with one or more embodiments of the invention.

Figure 15 shows a view of exemplary arrangements of the shear walls (layout) of the prefabricated post-tensioned superstructure system in accordance with one or more embodiments of the invention. Figure 16 shows a view of exemplary reinforcement detail of connection between the column and the shear wall of the prefabricated post-tensioned superstructure system in accordance with one or more embodiments of the invention.

Figure 17 shows a cross section of exemplary shear walls in the line of two adjustment columns (thru the line of tendons) of the prefabricated post-tensioned superstructure system in accordance with one or more embodiments of the invention.

Figure 18 shows a front view of exemplary shear walls between two adjustment columns (in the frame of columns and floor slabs) of the prefabricated post-tensioned superstructure system in accordance with one or more embodiments of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before describing the present invention in details, it is to be understood that the phraseologies and terminologies used herein are for the purpose of description and should not be regarded as limiting.

Referring now to the attached drawing sheets provided with several illustrative figures, wherein like reference numerals designate the steps, components or elements throughout the ensuing enabling description, the present invention provides for construction method of providing a prefabricated post-tensioned superstructure system. The entirety of the active steps of the method is designated as 10.

Referring now to the Figure 1, the herein construction method of the present invention starts with step“A.” More particularly, step“A” represents production of pre cast structural elements in steel molds in factory conditions (open polygon in the Philippines for example). However, depending on climate conditions, the production of the structural elements can be organized in the following manner: (a) off-site, in covered and closed factory settings, and (b) on-site, in outdoor concrete facilities (pre-cast plant).

Steel molds are the main equipment for production of the structural elements of the herein disclosed prefabricated post-tensioned superstructure system in accordance with embodiments of the present invention. They can be used for casting about 2,500 to 3,000 times, depending on timely and proper maintenance. They could be movable or fixed. Steel molds and technology layout of the pre-cast facilities are part of the structural design of the herein disclosed prefabricated post-tensioned superstructure system.

Figure 2 shows a 3D view of exemplary assembled prefabricated post-tensioned superstructure system buildings superstructure and positions of all pre-cast structural elements in this. Meanwhile, Figure 3 shows an exemplary production line of the pre cast structural elements of the herein disclosed prefabricated post-tensioned superstructure system of the present invention, as follow: columns with one, two and/or three story (11/lla), floor slabs with different options and shapes (12), cantilever floor slabs with different options and shapes (13), edge girders (14), stairs (15) and shear walls (16). Reinforcement grade 40/60 and concrete with strength of 5000 psi are used for production of elements. Pre-cast finished elements may be stored at pre-cast plant. Additionally, Figures 4 and 5 show typical prefabricated floor slab (12) of the herein disclosed prefabricated post-tensioned superstructure system— hereby presented as options 1 and 2. Generally, in both options floor slabs are of waffle (ribs) types.

According to the requirements for assembly of elements on the building site, step “B” is next. The structural elements of the herein disclosed prefabricated post-tensioned superstructure system may be transported from the pre-cast plant to the building site (housing, public or industrial buildings) on which a building is being built by use of standard lorries with or without additional platforms. The weight of heaviest elements does not exceed seven (7) tons, and their dimensions allow moving of elements in public transport. Common practice is that pre-cast elements delivered on site are placed on temporary site storage area. In case of absence of available space for that purpose, pre cast elements can be installed directly from the lorry (i.e., vehicle).

After step“B” is achieved and/or performed, and the pre-cast structural elements (11 to 16) are ready for assembly, step“C” is next and it is characterized by assembly of pre-cast elements of the herein disclosed prefabricated post-tensioned superstructure system by use of special steel temporary equipment— diagonals (23) for lower columns (11) vertical fixing and steel support (24) for floor slabs assembly (12). These are separately illustrated in Figures 6, 7 8, and 9 of the attached drawing sheets.

Basically, the herein disclosed prefabricated post-tensioned superstructure system has two typical joints. The first one joint is achieved in the step“C” of the herein disclosed construction method of the present invention in accordance with several disclosed embodiments. Figure 6 shows an exemplary vertical joint of columns (11 depicts lower column; 11a depicts upper column) of the herein disclosed prefabricated post-tensioned superstructure system. Typical cross section of the pre-cast columns of the herein disclosed prefabricated post-tensioned superstructure system is square. Their lengths can vary up to three (3) floors— one-storey, two-storey, or three-storey, by way of examples and not by way of limitation. They have openings on every floor level of buildings in both (level of floor slabs) for positioning (placing thru the lower column 11) post tensioning tendons (20). Lower columns (11) verticality is adjusted by temporarily steel diagonals (22) and fixing in proper positions, in both orthogonal directions.

During continuation of columns (vertical joint of columns) reinforcement bars, dowels (17) of lower columns (11) are slid into the pre-determined holes of upper columns (11a) where the joints are on the floor level, in accordance with some embodiments. Between lower and upper columns (11/lla), steel spacers (18) are placed in order to achieve the space between the columns. This space and holes of upper columns (11a) are then injected with mortar (19) that act as protection against corrosion.

In some embodiments, before the vertical joining of columns (11 and 11a), steel temporary support for floor slab assembly (23) is fixed on the surface of the lower column (11). In this way, step“C” is completed. Next is step“D” after step“C.”

The second one joint is achieved in step“D.” Figure 10 shows an exemplary horizontal joint between pre-cast lower columns (11) and floor slabs (12) of the herein disclosed prefabricated post-tensioned superstructure system. Namely, floor slabs (12) which may come with options 1 and 2 (Figures 4 and 5, respectively)— of the herein disclosed prefabricated post-tensioned superstructure system that can be installed and post-tensioned into floor deck as shown on Figure 7 wherein the assembly of simple pre cast floor slabs may be made of one piece and may be connected with columns by primary post-tensioning and use of tendons tensioning (20).

However, in case of architectural needs for bigger span (say 6.00 x 6.00 m and more), the composite floor slabs (12) of the herein disclosed prefabricated post-tensioned superstructure system may be applied and may be made of 2 or 3 pieces as shown in Figure 8, or 4 pieces with implementation of short pillars (24) as shown in Figure 9. In these cases, compacting of floor slabs pieces into one piece (12) are produced by secondary post-tensioning and use of tendons tensioning (21). This is done prior to connection of floor slabs (12) with lower columns (11) and primary post-tensioning (20).

Consistent with the herein disclosed embodiments, cross section of the typical horizontal joint formed between lower pre-cast columns (11) and pre-cast floor slabs (12) is shown in Figure 10. Pre-cast floor slabs (waffle or flat) may have indented comers positioned at the junction of jointing with lower columns (11).

During assembly, adjacent pre-cast floor slabs are placed on temporary steel supports— or the profiles called“capitel” (23) in Europe, which are already prepared and fixed on the surface of the lower column (11) during execution of step“C.” These supports are removed after applying post-tensioning and concreting of tendons (20).

Tendons (20) are placed thru lower columns (11), thru the empty space between two adjacent floor slabs (12), from one to the other ends of buildings in both orthogonal directions on each floor level. Tendons (20) are fixed by anchors and wages on both ends of buildings. Connection between vertical elements (lower and upper columns 11 and 11a; and short pillars 24) and horizontal elements (floor slabs— 12, cantilever floor slabs— 13 and edge girder— 14) are produced on site by post-tensioning method, using tendons, which are tensioned by jacks and pumps (e.g., hydraulic equipment for the herein disclosed prefabricated post-tensioned superstructure system). Line of tendons tensioning, process of tendons tensioning, such as a choice of hydraulic pumps and jacks are subject to detailed structural design and applicable design standards.

Figure 11 shows exemplary horizontal joint between pre-cast lower columns (11) and edge girders (14) and/or cantilever floor slabs (13) of the herein disclosed prefabricated post-tensioned superstructure system. This joint is achieved as explained in this step“D.” After application of the designed horizontal force in tendons (20), step“D” is completed. Step“E” consists of cast in place concreting (i.e., protecting) tendons (20) into the empty space between two adjacent floor slabs (12)— the lines of tendons (20), from one to the other ends of buildings in both orthogonal directions on each floor level. Concreting (or protecting) tendons is done after designed post-tensioning horizontal force is applied. This process is done by cast in place concrete of 5000 psi strength. When all lines of tendons according to step“E” are executed, step “F” is next. Step“F” consists of disassembly of special steel temporary equipment of the herein disclosed prefabricated post-tensioned superstructure system or the diagonals for columns vertical fixing (22) and steel support for floor slabs (23). Repetition of all above steps“A” to“F” on the next building’s floor if it has multiple floor levels.

Step “G” consists of assembly of shear walls (16) of the herein disclosed prefabricated post-tensioned superstructure system. This assembly may be done in pre cast or cast in place, executing simultaneously with steps“A” to“F” on every floor level of the building if the building has two or more floor levels. Specific advantage of the concept of shear walls of the herein disclosed prefabricated post-tensioned superstructure system is in the way in which the load-bearing elements are joined by post-tensioning with tendons (20). Effective application of the shear walls (16), which absorb impact of horizontal forces (as explained in details in the present invention), makes the especially suitable for earthquake prone seismic zones and areas where very strong winds may be expected. Seismic design is tailored for Zone IV (UBC-USA), which makes it ideal for use in the Philippines for example. The structural design of the herein disclosed prefabricated post-tensioned superstructure system may also be capable of withstanding strong winds brought about by super typhoons of up to Category 5. In some embodiments, the position for the shear walls (16) may be in the center of each half of the building.

In Figures 12, 13 14, 15, 16, 17 and 18, general recommendations and procedures of shear walls (16) assembly are exemplary given in different views. Figure 12 shows a view of exemplary location of the shear walls (16) of the herein disclosed prefabricated post-tensioned superstructure system in some symmetrical composition in the building’s floor layout. Figure 13 shows a view of exemplary cross section of buildings with shear walls (16) as option A and without shear walls as option B.

Figure 14 shows a view of exemplary assembly of the pre-cast post-tensioned framework floor deck (rigid) of the herein disclosed prefabricated post-tensioned superstructure system. Accordingly, and further, Figure 15 shows a view of exemplary arrangements of the shear walls (layout) of the herein disclosed prefabricated post- tensioned superstructure system while Figure 16 shows a view of exemplary reinforcement detail of connection between the columns (11) and the shear walls (16) of the herein disclosed prefabricated post-tensioned superstructure system. Figures 17 and 18, respectively, shows a view of exemplary cross section of shear walls (16) in the line of two adjustment columns (11) preferably thru the line of tendons (20) of the herein disclosed prefabricated post-tensioned superstructure system of the present invention, and a front view of exemplary shear walls (16) between two adjustment columns (11), in the frame of columns (11) and floor slabs (12).

In sum, the herein disclosed construction method of providing a prefabricated post-tensioned superstructure system comprises the steps of: (a) producing pre-cast structural elements in steel molds in factory conditions; (b) transporting the pre-cast structural elements from a pre-cast plant to a building site on which at least one building is being built; (c) forming vertical joints of lower and upper columns (11, 11a) of the prefabricated post-tensioned superstructure system using a special steel temporary equipment; (d) forming horizontal joints between vertical and horizontal structural elements of the pre-cast structural elements; (e) disassembling of the special steel temporary equipment; and (f) positioning shear walls (16) in the at least one building relative to the pre-cast structural elements of the herein disclosed prefabricated post- tensioned superstructure system. Again, the transporting step may be carried out by use of standard lorries with or without platforms, and the disassembling step may be carried out manually. Further, the positioning step may be executing simultaneously with all other steps on every floor level of the building if the building has two or more floor levels in accordance with general recommendations and procedures of the shear walls positioning, consistent with the disclosures of the present invention.

There are several advantages of the present invention and benefits of using the herein disclosed prefabricated post-tensioned superstructure system. Prefabricated post- tensioned superstructure system is economical as in turn it decreases cost of construction thru less consumption of materials (due to post-tensioning); lighter shell allows designing smaller and more economical components/foundation. The herein disclosed prefabricated post-tensioned superstructure system is time-saving as it cuts down construction time thru industrial production of pre-cast elements that can start and go parallel with design work, site prep, foundation work & other services. Speedy assembly as discussed earlier is also an advantage. With the herein disclosed prefabricated post-tensioned superstructure system, high quality construction procedures are guaranteed along with strict quality control undertaken with procedures and quantities during production of elements, assembly procedure and application of post-tensioning on the site.

Additionally, the herein disclosed prefabricated post-tensioned superstructure system is fully“open” as it allows wide range of different architectural solutions. The system is open for use of other secondary systems and materials. The present invention as illustrated allows an almost unlimited diversity of pre-cast cladding elements and facade. Balconies, loggias, and a combination of both can also be used. Further, the herein disclosed prefabricated post-tensioned superstructure system is safe.

To emphasize, the novelty of the present invention resides in the way in which the load-bearing elements are joined by pre-stressing with tendons. Effective application of shear walls, which absorb impact of horizontal forces, makes the herein disclosed prefabricated post-tensioned superstructure system especially suitable for earthquake prone seismic zones and areas where very strong winds may be expected. Seismic design is tailored for Zone IV (UBC-USA), which makes it ideal for use in the Philippines for example. The herein disclosed design is also capable of withstanding strong winds brought about by super typhoons of up to Category 5.

Claims

1. A construction method of providing a prefabricated post-tensioned superstructure system, the construction method comprising the steps of: producing pre-cast structural elements in steel molds in factory conditions; transporting the pre-cast structural elements from a pre-cast plant to a building site on which at least one building is being built; forming vertical joints of lower and upper columns of the prefabricated post- tensioned superstructure system using a special steel temporary equipment; forming horizontal joints between vertical and horizontal structural elements of the pre-cast structural elements; disassembling of the special steel temporary equipment; and positioning shear walls in at least one building relative to the pre-cast structural elements of the prefabricated post-tensioned superstructure system.

2. The method according to claim 1, wherein the pre-cast structural elements of the prefabricated post-tensioned superstructure system include columns, floor slabs, cantilever floor slabs, edge girders, stairs and the shear walls.

3. The method according to claim 1, wherein the transporting step is carried out by use of standard lorries.

4. The method according to claim 1, wherein the disassembling step is carried out manually.

5. The method according to claim 1, wherein the positioning step is executing simultaneously with all other steps on every floor level of the building if the building has two or more floor levels.