CONCRETE STRUCTURES

[0002] BACKGROUND

[0003] The invention relates to concrete structures having gauges and sensors pre-cast therein.

[0004] It is of growing interest to embed electronic sensors in concrete, but practically speaking, the manufacturing process and environment poses its own set of challenges that work against the effort. For example, the assignee has developed concrete pilings that have strain gauges and accelerometers embedded at the piling top and the piling tip. A radio is also embedded to transmit the sensor signals from the piling so that driving of the piling can be monitored and/or controlled during pile installation. The prior known pilings are described in U.S. 6,533,502, which was developed by the University of Florida and is licensed to the Assignee, as well as US2006/0021447 and US2007/0151103 which were developed by the assignee, the contents of all of which are incorporated herein by reference as if fully set forth.

[0005] Generally, the sensors are located in the piling form, and concrete is then poured into the form. The concrete includes heavy aggregate, and can be directed from a chute up to six feet above the form. This heavy flow of material can dislodge or damage the gauges and sensors as well as the wires connecting them to a transmitter and/or antenna assembly that is installed in a surface of wet concrete after it is poured.

[0006] Accordingly, the challenges presented include (but are not limited to) maintaining sensor position and alignment, ensuring good/complete concrete coverage around the sensor and electronic detail areas without creating voids, making sure the delicate sensors are not damaged during the concrete placement (and sometimes high temperature curing) process, and preventing water in the mix at higher head pressures from permeating and compromising the sensors, connectors, and electronics, etc. [0007] It would be desirable to provide sensor assembly and a method that overcomes these issues.

[0008] SUMMARY

[0009] A method and an assembly of pre-casting, and preferably covering and sealing, the sensors and sensitive measurement electronic devices such as strain sensors, accelerometers, temperature sensors, inclinometers, tiltmeters, load and pressure cells, piezometers, etc., sometimes in multiple combinations and arrangements, in various controlled and visually identifiable simple shapes such as rods, cones, spheres, cylinders, blocks, etc., is provided, preferably using a lower modulus (than the final concrete element) cement grout-based material, with possible light-weight filler added. This allows the sensitive electronics and sensors to be encapsulated in a more controlled process/environment that specifically addresses the challenges described above. These precast assemblies that include the desired sensor(s) encapsulated therein can then be positioned in the final element in a desired location prior to casting the concrete.

[0010] Depending on the application requirements, the encapsulating material properties such as mix viscosity, material, thermal conductivity, weight, permeability, and material modulus can be controlled to ensure sensor measurements accurately reflect desired conditions within the final structure, and also protect the sensors from damage.

[0011] As part of the pre-cast sensor assemblies; aspects of the shape, color, external markings, external dimensions, and outside surfaces can provide quick visually identifiable information about the sensors within. This includes information on sensor types, combinations, configurations, and orientations.

[0012] The sensor positions/locations within the encapsulated material of the pre-cast sensor assembly are controlled and documented relative to the assembly's final external dimensions. It is also desirable to include as part of these objects, electronically stored within and identifiable information on manufacturer, sensor lot numbers, calibration data, date of manufacturer, configuration, and unique serial numbers to name a few; essentially making the objects self-identifying.

[0013] Also, as part of the pre-cast sensor assembly, mechanical mounting features such as threaded rods, loops, hooks, anchor holes, etc. to provide means to rigidly and repeatably mount or affix the pre-cast sensor assemblies in the proper orientation (if applicable) within the framework of the final concrete element. It is preferable that the external mounting features are part of the internal structure that supports the sensor elements.

[0014] A pig tail cable section preferably extends outside of the pre-cast sensor assembly allowing for wired interface connections to be made. It is also possible to provide a recessed cavity to make the connection, and then cover or epoxy the connection closed. This interface method allows for a number of these sensor objects in the same or different configurations all within the same final element to be connected to a common data acquisition device.

[0015] BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The foregoing summary, as well as the following detailed description of the preferred embodiments of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements shown.

[0017] Fig. 1 is a perspective view of a pre-cast sensor assembly according to the present invention.

[0018] Fig. 2 is an end view of the pre-cast sensor assembly of Fig. 1.

[0019] Fig. 3 is a perspective view of an alternate embodiment of a precast sensor assembly according to the invention.

[0020] Fig. 4 is a perspective view of an exterior of the sensor assembly of the embodiment of Fig. 3. [0021] Fig. 5 is a perspective view of a further alternate embodiment of a pre-cast sensor assembly according to the invention.

[0022] Fig. 6 is a cross-sectional view through a mould or form showing the pre-cast sensor assembly of Figure 1 installed in position prior to casting concrete.

[0023] DETAILED DESCRIPTION OF THE PREFERRED

EMBODIMENTS

[0024] Certain terminology is used in the following description for convenience only and is not considered limiting. The words "lower", "upper", "left" and "right" designate directions in the drawings to which reference is made. As used herein, the recitation of "at least one of A, B or C" means any one of A, B or C or any combination thereof, where A, B and C represent the noted features or elements of the invention. Additionally, the terms "a" and "one" are defined as including one or more of the referenced item unless specifically noted.

[0025] Referring to Fig. 1, a pre-cast sensor assembly 10 is shown. The pre-cast sensor assembly 10 includes a carrier plate 12, preferably made of punched steel sheet metal. It includes at least one sensor cutout 14 along with positioning holes 16 for attaching a sensor, such as a strain gauge 18, in position. The cutout 14 is formed so that the encapsulating material used to encapsulate the sensor 18 and the carrier plate 12 in order to form the precast sensor assembly 10 can make intimate contact with the sensor 18. The carrier plate 12 further includes tabs 30 with attachment holes for later use.

[0026] Preferably, the carrier plate 12 further includes holes 20 for locating and attaching a conditioning electronics module 22 which can be used to receive the signal from the sensor 18 and condition the signal for transmission to an external source, such as converting it to a radio transmission signal. Preferably, the conditioning electronics 22 includes a processor and a memory for storing data. A cable 28 preferably extends outside of the pre-cast sensor assembly 10 and is connected to other cables or wires within the mould or form used to shape the concrete structure, for example to a radio transmitter assembly prior to casting the concrete. The cable 28 preferably has a plug on its end to allow for easier connections.

[0027] In a preferred embodiment, tie wraps 24 are used in order to attach the conditioning electronics module 22 as well as the sensor 18 in position on the carrier plate 12 by threading the tie wrap 24 through the holes 16, 20 provided and tightening the tie wrap knuckle in order to firmly connect the sensor 18 as well as the conditioning electronics 22 in position. Those skilled in the art will recognize that the carrier plate 12 can have additional sensor cutouts, for example, for attaching an accelerometer, pressure sensor or other sensor, as discussed below in connection with Fig. 5.

[0028] After the carrier plate 12 is assembled with the sensor 18 and the conditioning electronic module 22, it is positioned in a form (not shown) and cast with the encapsulating material 38. The encapsulating material 38 is preferably a grout-based material mixed from cement, sand, optional lightweight filler, and water in order to achieve desired properties. The lightweight filler can be, for example, vermiculite. The mixture can include other additives for controlling properties such as thermal conductivity, permeability, and material modulus. The mixture viscosity can also be adjusted by adding more liquid or cement. The encapsulated material 38 is cast and cured in a small quantity in a controlled environment under desired conditions which allows the sensor 18 be completely encapsulated in order to address the challenges described in the background above prior to installation in a concrete structure.

[0029] The tabs 30 on the carrier plate 12 extend outside of the body of the encapsulating material. This allows the pre-cast sensor assembly 10 to be prepositioned in a concrete form when it is assembled into the final concrete element that is to be manufactured in a later step. As shown in Figure 1, preferably the attachment holes 32 are outside the encapsulating material.

[0030] In the first preferred embodiment, the pre-cast sensor assembly

10 is shaped as a rectilinear block 40. The shape can be used as a visually identifiable indicator of the type(s) of sensor(s). Various shapes such as spheres, cylinders, rectilinear blocks, etc. can be used. The shapes are preferably quadrant symmetric shapes (i.e., symmetric about the X and Y axes when viewed in cross- section). Further, the shapes can have indentations or undercuts to allow mechanical interlocking with the concrete structure in which it is encapsulated. Other markings such as color coding in the encapsulating material 38 can also be utilized as an identifier.

[0031] Referring to Fig. 2, the rectilinear block 40 for the pre-cast sensor assembly 10 is shown with the external tabs 30 extending from opposing sides.

[0032] Figs. 3 and 4 show an alternate embodiment of a cylindrical cast block 50 used to form a pre-cast sensor assembly 10'. Here, for example, the cylindrical cast block 50 could indicate that the pre-cast sensor assembly 10' includes an accelerometer 18' located in a sensor cutout 14' in the carrier plate 12', instead of a strain gauge 18 as in the first embodiment 10. The remaining elements of the pre-cast sensor assembly 10' are the same as in the first embodiment 10, and have been identified with the same reference numbers [0033] Alternatively, as shown in Fig. 5, the pre-cast sensor assembly

10" can have a plurality of sensors embedded therein, such as the strain gauge 18 and the accelerometer 18'. Here, the carrier plate 12" includes multiple sensor cut-outs 14. 14" to accommodate the two sensors 18, 18', which are held in place using tie-wraps in the same manner as the prior embodiments. Here, the pre-cast block 70 has a rectilinear shape, although it could have another shape. Those skilled in the art will recognize that various shapes can be utilized. Other external markings, dimensions, or exterior visually identifiable information can be provided in order to allow a user to quickly and easily determine the type of sensor located within the pre-cast sensor assembly 10, 10', 10". Further, the orientation of the sensor can be indicated by markings, the dimensions and/or configuration of the block 40, 50, 70.

[0034] Referring to Fig. 6, use of a pre-cast sensor assembly 10 in connection with a concrete form is illustrated. Here the pre-cast sensor assembly 10 is located between the re-bar or other reinforcements 62 in a concrete mould or form 60 used in casting a concrete structure, for example, drilled shafts, piles, spun-cast piles, auger-cast piles, concrete containment vessels, superstructure components, and various other concrete structures. Here the pre-cast sensor assembly 10 is preferably cast of a cement grout- based encapsulating material and is held in position by threaded rods or wires 64 that are connected through the attachment holes 32 of the external tabs 30 on the pre-cast sensor assembly 10 and connected on their ends to the re-bar or other reinforcements 62 via hooks or other means. Through the use of the pre-cast sensor assembly 10, 10', 10", special care is not required in casting the course aggregate used in forming concrete structures to ensure that it completely encapsulates the sensor without any air voids and further to avoid direct pouring of the concrete mixture onto the pre-cast sensor assembly 10, 10', 10" since it is ruggedized by the encapsulating material utilized in forming the cast block 40, 50, 70.

[0035] While the preferred embodiments of the invention have been described in detail, the invention is not limited to the specific embodiments described above, which should be considered as merely exemplary. Further modifications and extensions of the present invention may be developed, and all such modifications are deemed to be within the scope of the present invention as defined by the appended claims.