METHOD FOR BUILDING PRESTRESSED CONCRETE STRUCTURES BY MEANS OF PROFILES CONSISTING OF A SHAPE-MEMORY ALLOY, AND STRUCTURE PRODUCED USING SAID METHOD

• US 20160053492A1
• Filed: 03/17/2014
• Published: 02/25/2016
• Est. Priority Date: 04/08/2013
• Status: Active Grant

• Current Assignee: Empa, Re-Fer AG
• Original Assignee: Empa, Re-Fer AG
• Inventors: LEINENBACH, Christian, MOTAVALLI, Masoud, WEBER, Benedikt, LEE, Wookjin, BRNNIMANN, Rolf, CZADERSKI, Christoph
• Granted Patent: US 9,758,968 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: C22C 38/00 Ferrous alloys, e.g. steel alloys cast-iron alloys C22C37/00
• CPC Class Codes: C22C 38/02 containing silicon
• CPC Class Codes: C22C 38/04 containing manganese
• CPC Class Codes: C22C 38/105 containing Co and Ni
• CPC Class Codes: C22C 38/14 containing titanium or zirconium
• CPC Class Codes: C22C 38/40 with nickel
• CPC Class Codes: E04B 1/16 Structures made from masses, e.g. of concrete, cast or similarly formed in situ with or without making use of additional elements, such as permanent forms, substructures to be coated with load-bearing material E04B1/32 - E04B1/36 take precedence
• CPC Class Codes: E04C 5/01 Reinforcing elements of metal, e.g. with non-structural coatings E04C5/08 takes precedence
• CPC Class Codes: E04C 5/07 Reinforcing elements of material other than metal, e.g. of glass, of plastics, or not exclusively made of metal metal elements with non-structural coatings E04C5/01
• CPC Class Codes: E04C 5/08 Members specially adapted to be used in prestressed constructions production of reinforced objects in general B28B23/00; prestressed structures produced in situ E04G21/12
• CPC Class Codes: E04G 21/12 Mounting of reinforcing inserts; Prestressing shell tubes for prestressing members E04C5/10; anchoring means E04C5/12; connections of reinforcing elements and spacers E04C5/16
• CPC Class Codes: E04G 23/0218 Increasing or restoring the load-bearing capacity of building construction elements E04G23/0203 and E04G23/0266 take precedence

Abstract

The invention relates to a method according to which a profile consisting of a shape-memory alloy is placed into concrete, or a concrete to be reinforced is roughened on the outside, then profiles (2) consisting of a shape-memory alloy are fastened to the roughened outside (9) of the structure (6) and a cementitious matrix is applied to the roughened outside (9) to cover the profiles (2). After the cementitious matrix has set, said profiles (2) produce a contraction force and thus a tension as a result of the input of heat. The mortar covering layer (16) thereby acts as a reinforcement layer owing to the interlocking of the mortar covering layer (16) with the roughened outside (9) of the structure (6). The profiles (2) run in an outer mortar as a reinforcement layer (16) of the outside of a structure along the outside of the structure inside the mortar or reinforcement layer (16). A structure can also be prepared for a prestress in the equipped mortar or reinforcement layer by the input of heat, in that electrical cables (3) are routed from the end regions thereof to the outside of the mortar or reinforcement layer (16) or the end regions of the electrical cables (3) are accessible by removing inserts (5).

Claims

1. A method to create prestressed concrete structures by means of profiles made from a shape-memory alloy, be it of new structures and structural elements or cement-bound mortar mixes for the reinforcement of existing concrete structures, characterised by the fact that

a. the outside of the existing structure to be reinforced or recess (FIG. 9) is roughened therein,

b. that profiles (2) made from a steel-based shape-memory alloy of polymorphic and polycrystalline structure with ribbed surface or with a thread-shaped surface, which can be taken from its condition as martensite to its permanent condition as austenite by increasing its temperature, are attached to the roughened outside (9) of a structure (6,12),

c. capillary saturation of the outside of the structure (6,12) with water is generated and then a cementitious matrix is applied to this outside as mortar mix to cover the profiles (2) made from a shape-memory alloy,

d. following the hardening of the cementitious matrix, the profiles (2) made from a shape-memory alloy are made to generate contraction force and thus tension through the input of heat, as a result of which the created mortar mix causes prestressing of the same as reinforcement layer (16,19) through the indentation of the roughened outside (9) of the structure (6,12) whereby force is transmitted to the concrete or mortar mix (1) through the surface structure of the profile (2).

2. A method to create prestressed concrete structures by means of profiles made from a shape-memory alloy according to claim 1, characterised by the fact that under

a. the profiles (2) are attached to the roughened outside (9) of the structure (6,12) with additional end anchors and under

d. force is also transmitted to the concrete or mortar mix (1) through the end anchors.

3. A method to create prestressed structures by means of profiles made from a shape-memory alloy according to one of the preceding claims, characterised by the fact that

a. the outside of the existing structure to be reinforced (6,12) or recess therein is roughened hydromechanically with a pressure of at least 500 bar or by means of sand blasting up to a surface roughness of minimum 3 mm so that the underground is saturated with water,

b. profiles (2) made from a shape-memory alloy are attached to the roughened outside (9) of the structure (6,12) or in the recess by means of anchors or steel profiles,

c. capillary saturation of the outside of the structure (6,12) or recess therein with water is generated and then a cementitious matrix as mortar mix is applied as reinforcement layer (16,19) by hand or sprayed on as dry sprayed concrete or that, in case of horizontal outsides, a mortar mix is created as reinforcement layer (16,19) by means of coats of self-levelling flow mortar and covering of the profiles (2) made from shape-memory alloy with, alternatively, dowelling of the mortar mix and/or reinforcement layer (16,19) by applying dowels (13) which extend behind a front concrete reinforcement (7,8) of the structure (12) behind the applied mortar mix and/or reinforcement layer (16,19),

d. following the hardening of the applied mortar mix and/or reinforcement layer, the profiles (2) made from a shape-memory alloy are made to generate contraction force and thus tension through the input of heat, as a result of which the applied mortar mix and/or reinforcement layer (16,19) causes prestressing of the same through the indentation with the roughened outside (9) of the structure or its recess.

5. A method to create prestressed concrete structures by means of profiles made from a shape-memory alloy according to one of the preceding claims, characterised by the fact that the profiles (2) made from a shape-memory alloy, for the purpose of the heat input from a voltage source in the form of an energy unit from a row of serially linked batteries through fixed or temporarily connected electrical cables (3), are put under electrical tension of 10-20 V per m of profile length to generate a current of 10-20 A per mm² of cross-section area so that these form resistance heating and are brought from their condition as martensite to their existing condition as austenite within 2 to 10 seconds.

6. A method to create prestressed concrete structures by means of profiles made from a shape-memory alloy according to claim 5, characterised by the fact that multiple electrical connections with outward leading heating cables are provided across the length of the profile and the input of heat is generated step by step through the application of voltage at two neighbouring electrical connections at any one time.

7. A concrete structure built by using the method according to claim 1.

8. A concrete structure built by using the method according to claim 2.

9. A concrete structure built by using the method according to claim 3.

11. A concrete structure built by using the method according to claim 5.

12. A concrete structure built by using the method according to claim 6.

4. A method to create prestressed concrete structures by means of profiles made from a shape-memory alloy, characterised by the fact that profiles (2) made from a steel-based shape-memory alloy with ribbed surface are inserted into the concrete of the current structure (14) to be created for the potential preparation at a later time of an extension of a new concrete structural element (15) to a current structure (14) to be created, so that these profiles run perpendicular to the outside of the structure (18) and are equipped with a coarse thread (20) at the end and end below the surface of the outside of the structure (18) whereby the end regions are enclosed with a removable insert (5) and subsequently covered with mortar so that a projecting concrete structural element (15) can be concreted and prestressed to the previously created concrete structure (14) at a later time as needed as the concrete structural element (15) to be added is equipped with profiles (2) with ribbed surface made from a shape-memory alloy and coarse thread (20) in the end region and can be connected through coupling elements (22) with transfer of tensile force from the outside towards the outside of the structure (18) of the previously created concrete structure (14) with the end regions of the exposed profiles (2) made from a shape-memory alloy in the existing concrete structure (14) and can be concreted afterwards so that, after hardening by means of the input of heat, its profiles (2) made from a shape-memory alloy with ribbed surface generate contraction force and that the attached concrete structural element (15) experiences its own prestress this way and is docked to the existing concrete structure (14) under prestress.

10. A concrete structure built by using the method according to claim 4.