WO2015188203A2

WO2015188203A2 - System and method for method remote assessment of quality of construction

Info

Publication number: WO2015188203A2
Application number: PCT/ZA2015/000042
Authority: WO
Inventors: Michael Rodger LORETZ
Original assignee: Loretz Michael Rodger
Priority date: 2014-06-05
Filing date: 2015-05-29
Publication date: 2015-12-10
Also published as: WO2015188203A3; ZA201605131B; WO2015188203A8; WO2015188203A4; GB2542077A; GB2542077B; GB201700069D0

Abstract

The invention provides a system (10) and method for remote assessment of the quality of construction of a structure, for example a multi-storey building (11). The system (10) is characterized Insofar as it includes thermal imaging means (13) for generating thermal images of the structure. The system further comprises the following components; at least one camera system (13) for generating images of the structure; distance measuring means (12) for measuring distances In relation to the structure; primary data processing means (14); storage means loaded with CAD software for execution by said primary data processing means (14); and data transmission means (17, 18) for transferring data from said camera system (13) and said distance measuring means (12) to said primary data processing means (14). The camera system (13) may have integrated, dual capabilities of generating video and thermal images. The method of the Invention includes a step of generating thermal images of a structure using thermal imaging means.

Description

Title of Invention : SYSTEM AND METHOD FOR REMOTE ASSESSMENT OF QUALITY OF CONSTRUCTION

Technical Field

[0001] This invention relates to a system for monitoring quality during construction of structures and facilities, particularly although not exclusively, during construction of multi-storey buildings.

Background Art

[0002] In the field of construction it is necessary to verify that works are being completed in accordance with contractual obligations and that designs are being correctly interpreted. It is also necessary to ensure that appropriate construction techniques are being used. Typically, monitoring of construction sites is carried out by consulting engineers who perform visual inspections and interpret results of testing. Comparison of actual dimensions against plan dimensions is required. The correctness of structural reinforcing must be verified. Visible defects or deviations from specifications must be noted.

[0003] The minimum requirements for construction monitoring stipulate that site inspections must be conducted by the consulting engineer's qualified personnel. Technology can, however, be harnessed to enhance a quality inspector's ability to make informed judgements on the quality of products and workmanship.

[0004] Systems have previously been developed to assist in this regard. For example, networked CCTV camera imagery transmitted over a wireless internet connection has been applied to track the construction progress of a bridge (Kim, C, ef a/., 2009). Kim ef al. described how image processing software was applied to determine the outline of the structure which was then processed in a three- dimensional (3D) Computer Aided Draughting (CAD) model. The 3D image was then matched to the CAD model and actual progress could then be measured against planned progress. The combination of 3D CAD with CCTV capability is now known as 4D CAD and is being applied in Building Information Management (BIM) (Kwak, J, er a/., 201 1). [0005] There is a trend towards cost driven procurement policies in the Consulting Engineering industry. During the design stages of a project, such cost considerations can lead to the implementation of an approach based on "catalogue engineering" instead of a "design from first principles" protocol. This in turn can compromise design quality and potentially increase the risk of failure due to design error. Reductions in physical monitoring, also driven by cost considerations, may further decrease confidence in the quality assurance aspect of a project. A challenge currently faced by many consulting engineers is to maintain a high standard of service for all aspects of a project.

[0006] Given the above challenges and pressures, there is an ongoing need for development of systems which can aid consulting engineers in the assessment of quality during construction.

Definitions

[0007] "Assessment" - This term includes reference to monitoring and supervision activities carried out in connection with construction works and construction sites, for the purpose of quality assurance in relation thereto.

[0008] "Axis camera" - This term refers to an Axis Q87-E camera.

[0009] "CCTV" - This term refers to Closed Circuit Television.

[0010] "Flir camera" - This term refers to a Flir PT-602CZ dual CCTV and thermal imagery camera.

[0011] "Leica (laser) distance meter" - This term refers to a Leica Disto D810 Touch laser distance meter.

[0012] "Structure" - This term is intended to be construed broadly and includes reference to buildings, facilities, amenities, roads, parking bays, parking lots, paved surfaces, construction sites generally, and sub-sections thereof.

Summary of Invention

[0013] According to a first aspect of the invention there is provided a system for remote assessment of quality of construction of a structure comprising a plurality of structural elements, said system comprising the following components: at least one camera system for generating images of at least one of said structural elements; distance measuring means for measuring distances in relation to at least one of said structural elements;

primary data processing means;

storage means loaded with CAD software for execution by said primary data processing means; and

data transmission means for transferring data from said camera system and said distance measuring means to said primary data processing means;

characterized in that said system further includes thermal imaging means for generating thermal images in relation to at least one of said structural elements.

[0014] The thermal imaging means may comprise at least one thermal imagery camera. The thermal imagery camera may be integrated with the camera system, providing a dual camera system. The camera system may comprise at least one video camera, preferably a CCTV camera.

[0015] The distance measuring means may comprise an optical distance measurement instrument, preferably a laser distance meter. The distance measuring means and the camera system (or dual camera system) are typically mounted in fixed relationship to each other, for example on a motorised unit adapted for rotational, inclinational and/or declinational motion. They may have a synchronised relationship to each other, such that, in use, movement of the camera (or motorised unit) effects a movement of the distance meter, or vice versa, thereby to keep both facing in a generally corresponding direction. In use, the actual orientation and position of the distance meter in relation to the absolute centre point of the camera (or motorised unit) is established in advance, so that trigonometrical formulae can be applied to calculate correspondence between the distance meter and the camera.

[0016] The system may include a remote command input system to permit real-time interaction by operators. The command input system may include secondary data processing means, for example a tablet or like computer, with communication means for communicating with the other components of the system through Bluetooth or a similar short-range wireless technology standard. The command input system may include means for interactive communication with the primary data processing means and the CAD software. [0017] The system may include a plurality of like components, in order to extend coverage of the system over the structure, to provide redundancy of components and/or means for confirming data and measurements established by the components. For example, the system may include a plurality of video camera systems, a plurality of distance measuring means and a plurality of thermal imaging means.

[0018] The structure may be a multi-storey building.

[0019] According to a further aspect of the invention there is provided a method of assessing quality of construction of a structure comprising a plurality of structural elements, said method comprising the steps of:

(a) providing a system comprising the following components:

at least one camera system for generating images of at least one of said structural elements;

distance measuring means for measuring distances in relation to at least one of said structural elements;

thermal imaging means for generating thermal images of at least one of said structural elements;

primary data processing means;

data storage means loaded with CAD software for execution by said primary data processing means;

data transmission means for transferring data from said camera system, distance measuring means and said thermal imaging means to said primary data processing means;

(b) performing a quality check on said structure, representative of at least one pre-determined juncture in time, by carrying out the following sub-steps:

(b1) determining an initial spatial reference co-ordinate for said system;

(b2) assessing an actual setting out of at least one of said structural elements by taking linear measurements in relation to said initial spatial reference coordinate and said structural element using said distance measuring means; and

(b3) providing a spatial design of said structural element, comparing said actual setting out against said spatial design, and applying trigonometrical formulae to calculate deviations between said actual setting out and said spatial design;

(c) generating an image of said structural element using said camera system; and

(d) generating a thermal image of said structural element using said thermal imaging means.

[0020] The structural elements may comprise concrete structural elements and the method may further include assessing properties of said concrete by

importing said thermal image into said CAD software as a background thermal image;

providing a thermal design of said structural element;

overlaying said thermal design onto said background thermal image to generate a quality drawing;

calculating temperature deviations between said thermal image and said thermal design, thereby to calculate thermal performance data; and displaying said data on said quality drawing.

[0021] The method may include predetermining a specific reference point on at least one of said structural elements; generating spatial co-ordinates for the actual setting out of the structural element using linear distances measured by the distance measuring means in relation to the specific reference point on the structural element; interrogating the spatial design to establish spatial coordinates corresponding to the specific reference point within the spatial design; and

displaying in said quality drawing, in addition to the thermal performance data, (i) said spatial co-ordinates of said actual setting out, (ii) said spatial co-ordinates established from said spatial design, and (iii) deviations between said coordinates.

[0022] The method may include periodically performing a plurality of said quality checks, thereby to generate a plurality of successive quality drawings, and storing said successive quality drawings thereby to generate a historical record of the quality of construction of the structure. [0023] The step (b1) of determining an initial spatial reference co-ordinate for the system may include the following sub-steps:

providing and installing in proximity to said structure at least two benchmark beacons to serve as calibration reference points;

taking linear measurements in relation to each beacon using said distance measuring means;

loading the CAD software with trigonometrical formulae for determining the spatial co-ordinates of the initial spatial reference co-ordinate, by reference to said linear measurements taken in relation to said beacons;

assigning said initial spatial reference co-ordinate to a position of the distance measuring means.

[0024] The method may further include establishing the orientation and position of the distance measuring means in relation to the camera system.

Advantageous Effects of Invention

[0025] The system described herein may present certain advantages and outcomes.

The system could potentially enhance the levels of construction monitoring from a part-time to a virtual full time presence.

[0026] Enhanced construction monitoring may inhibit construction stage failure risks at a comparatively lower cost than having full time personnel present on site.

[0027] The system may enhance the efficiency of conventional concrete testing methodology by providing additional informative data which is accessible remotely in real-time. The thermal imagery camera of the present system can provide this data with the additional benefit of an early warning system.

[0028] The inclusion of the thermal imagery camera in the present system may also facilitate the following:

[0029] (i) assessment and monitoring of the hydration process of concrete structural elements, and detection of abnormalities associated therewith;

[0030] (ii) assessment and monitoring of the adequacy of concrete curing processes;

[0031] (iii) detection of defects and abnormalities in concrete structures; and [0032] (iv) alleviation of weather related constraints.

[0033] There is a growing emphasis on cost effective solutions which do not compromise quality. The advancement in technologies has a convincing part to play in achieving this. However, the human factor still has the major role when it comes to quality assurance of the construction of multi-storey buildings.

[0034] Further potential benefits of the system include high precision engineering survey capability, cost effectiveness by comparison with conventional survey methodology, reduction of uncertainty, safety benefits, enhanced ability to resolve problems with construction processes, and the capacity to simulate and analyze potential impacts.

[0035] The system described herein may also provide visual data that surpasses conventional visual inspection and testing methodologies.

Brief Description of Drawings

[0036] For a better understanding of the present invention, and to show how the same may be carried into effect, embodiments of the invention will now be described by way of non-limiting example with reference to the accompanying diagrammatic drawing:

Fig.1

[0037] Figure 1 illustrates, schematically, the proposed architecture of an embodiment of a system according to the invention.

Description of Embodiments

[0038] Construction of a hypothetical double storey office block on the basis of a concrete frame with brick infill is used as an example for illustrative purposes.

[0039] Referring to Figure 1 , reference numeral 10 indicates, generally, an example of an integrated system or model according to the present invention. The exemplary system 10 is implemented for assessing quality during construction on a building construction site 11.

[0040] The system 10 integrates the following components: [0041] (i) An optical distance measurement instrument 12, advantageously a hand-held unit such as the Leica laser distance meter.

[0042] (ii) A combined (i.e. dual) video camera system and thermal imaging means 13 in the form of a Flir or Axis camera. Such units pre-integrate dual functions within a single unit, the dual functions being (i) CCTV video imaging and (ii) thermal imaging. The use of such units simplifies the integration of the video and thermal imaging into the full system model. These units also have their own motorised rotation and tilt functions.

[0043] (iii) Primary data processing means 14 in the form of a remote office desktop computer which can be loaded with CAD software (for example the Caddie utility) and at least one file containing data which is representative of (a) the construction site or portions thereof and (b) the construction process.

[0044] (iv) secondary data processing means 15 in the form of an Android based tablet computer (or other suitable processing means such as a Raspberry Pi or Arduino device) to serve as a communications link mediating communication between the distance meter 12, the camera 13 and the remote computer 14.

[0045] (v) a steel or concrete mast 16, on which the distance meter 12, camera 13 and tablet 15 are mounted in elevated position, providing a vista over at least a portion of the construction site 11.

[0046] The tablet 15 has means for connecting wirelessly to the distance meter 12 and the camera 13. A short range communication protocol such as Bluetooth is preferred in this role, figuratively indicated by reference numeral 17. Thus, the Leica 12 and other components of the system 10 are linked to the tablet 15 (or Raspberry Pi or Arduino device) via Bluetooth.

[0047] Additionally, the tablet 15 has means for connecting wirelessly to the remote computer 14 by means of a wireless internet protocol, for example the Global System for Mobile Communications (GSM), which is figuratively indicated by reference numeral 18. Thus, the tablet 15 forms a wireless IP communication link between the other components of the system and the remote office desktop 14 through the GSM or other suitable wireless IP network. [0048] The laser distance meter 12 is mounted in fixed relation to the camera 13 so that it can move in synchronization with the camera 13 and remain pointed in the direction in which the camera 13 is facing. It may be mounted on the camera 13, above or below it, for example, and provides the distance meter 12 with mobility properties, for example motorized rotational, inclinational and/or declinational properties corresponding to and matching those of the camera 13 on which it is mounted. In addition a person operating the system using the CAD software is able visually to see (via the CCTV and/or thermal imagery camera 3) the laser target that is projected by the distance meter 12 onto an object to be measured.

[0049] A stand-alone unit can be provided to house selected components of the system in preferred embodiments. The stand-alone unit may include its own internal power source and/or power generation capacity, and means for wireless internet communication with the primary and/or secondary data processing means, so that the unit may operate independently of an external power source and fixed-line internet connection. The stand-alone unit may include its own solar panel, batteries, controller board and/or wind turbine. Such a unit could be erected, for example, at a remote rural construction site.

[0050] The mast 16 must be structurally engineered to take account of the potentially deleterious effects of wind conditions and mechanical resonance phenomena. This is crucial to the accuracy of measurements being affected by high wind conditions (Griffin, O. M., et a/., 1973). Griffin et al state that "it is a well-known natural phenomenon that the alternate vortex shedding that accompanies the flow past a bluff obstacle can excite the body into resonant, transverse vibrations when the vortex shedding frequency is sufficiently near to one of the body frequencies."

[0051] Those skilled in the art will appreciate that the components identified above and in Figure 1 are suggested by way of example only, and that other suitable devices and apparatus serving similar functions may be substituted for said components.

[0052] The function of the CCTV camera [0053] During the construction of the hypothetical building, the CCTV camera is installed in an elevated position on the construction site. It provides a visual confirmation component of a conventional visual inspection, with the added benefit of real-time remote access. The CCTV camera can continuously record construction activities. A photo record is kept for future reference during a conventional inspection, and may be recalled for a particular time period or point in time. This capacity for reference to historical data may increase an Engineer's ability to accurately assess the status of quality of materials and workmanship.

[0054] There are constraints that can be anticipated relating to the efficiency of a CCTV camera as the sole visual quality confirmation tool (Kim, C, et ai, 2013). Weather conditions such as dense fog, mist, rain, windy and dusty conditions could be a limitation.

[0055] Strong winds could affect the visual imagery of a unit mounted on a mast.

This could, for example, affect visual confirmation of the number of reinforcing bars in a particular reinforced concrete component. It can also be anticipated that there would be certain zones of the construction site which may be visually inaccessible on account of the positioning of the camera on site.

[0056] Accordingly, planning of the system and positioning of the masts and components may require a multiple setup of a single unit or multiple units in order to provide coverage and redundancy and confirmatory capabilities.

[0057] The function of the thermal imagery camera

[0058] Inclusion of the thermal imagery camera can address weather related constraints such as those mentioned above.

[0059] The thermal imagery component of the Flir or Axisunit compliment the CCTV camera as part of the visual aspect of the remote quality assurance system or model.

[0060] In addition to the use of thermal imagery as a visual quality confirmation tool, the unit can form an integral part of the quality assurance of structural concrete components during construction. The most common conventional quality control method for concrete strength is the compressive strength testing of samples as determined at 3 days, 7 days and 28 days. The testing is conducted under controlled conditions and is indicative of the status of the compressive strength of concrete structural elements even though the test is not done in-situ. The earliest indication of any problems is after the 3 day test results become available. Tests to determine the in-situ status at an earlier stage can be done using the Schmidt hammer testing method or core sampling, which is a destructive test method.

[0061] The use of the thermal imagery camera enables the monitoring of the hydration process of concrete structural elements which is indicative of the predictable strength properties of such an element (Azenha, M, et al., 201 1). The thermal imagery could then be utilized to detect any abnormalities with the hydration process which could influence the desired compressive strength.

[0062] The adequacy of a concrete curing process can be assessed visually using a thermal imagery camera (Rao, P. 2008). The thermal imagery camera of the present system can be applied towards this end, and may allow for early intervention and corrective measures. The curing status of concrete cannot be determined to equivalent accuracy with conventional visual inspection.

[0063] Thermal imagery is successfully used as a remote non-destructive evaluation technique for detecting defects in concrete structures (Bhalla, S, et al., 201 1). This allows for the early detection of fine cracks, honeycombing and voids, which are not necessarily detectable during a visual inspection.

[0064] The function of the optical distance measurement instrument

[0065] The distance meter can be remotely accessed to obtain linear distance measurements of the structure to be assessed. These measurements can be transferred into a 3D CAD model in real-time. The CAD package can be configured to allow for the interpretation of data to measure deviations from design parameters.

[0066] When positioned at a fixed elevated position above the works, the distance meter can be used to determine depths of layer works for each layer during construction thereof.

[0067] Roads, parking bays and other paved surfaces are typically built up in different layers, each layer having a different quality of material, with upper layers often comprising crushed rock coming from a rock quarry and crusher. The layers are usually approximately 150mm in depth.

[0068] For a multi-storey building's roads, parking bays and paved surfaces, the relevant area is typically prepared and compacted, and the layer works for the area are done up to the final pavement layer, which could be paving bricks, asphalt or concrete slabs. The layer works' depths are important from a quality point of view. The Leica distance meter, installed on a mast, may be utilised to progressively measure layer thicknesses as construction of the roads, parking bays and paved areas in the vicinity of the building progresses. A 'base' engineering survey is carried out prior to the commencement of construction of the layer works. Then, once a layer has been constructed, a subsequent survey is done in the same area. The difference between the two surveys determines the actual thickness of the layer. A quality drawing can be generated to replace the conventional surveys required.

[0069] The distance meter can be used to determine the positioning of shuttering (formwork casing) for concrete columns in relation to the anticipated final in-situ positioning of said columns, and deviations from specification can be measured. This may simplify the setting out of the shuttering to ensure that the column positions are within required tolerances.

[0070] By comparison, in conventional practice the position of a shutter is set out using a tape measure, or in best case scenarios, electronic survey equipment. The design setting out position is depicted on the design drawing. When the shutter is installed, the actual position versus the design position needs to be determined on order to see if adjustments to a given shutter are required before the concrete is cast into the shutter.

[0071] Integration of the components of the system:

[0072] Chart 1 (below) is a simplified, schematic process-flow diagram depicting the work flow for integrating components of the system according to the invention.

Chart 1

[0074] Software is required to allow remote command input into the Leica distance meter via Bluetooth. The linear distance measurement taken by the unit is the output provided by unit which is then imported into the Caddie CAD software in real-time.

[0075] A unit setup and calibration protocol is required to ensure that the Leica distance meter is aligned with the Flir or Axis camera. It is also required for determining the point of reference co-ordinates which are imported into Caddie CAD software.

[0076] At least two benchmark beacons are required to be installed on the construction site as calibration reference points. A benchmark is created by inserting a steel peg in the ground and encasing it with concrete. Once the motorized unit with camera and distance meter is installed on site, linear measurements are taken to each beacon using the distance meter. The CAD software is programmed with trigonometrical formulae in order to determine the exact spatial co-ordinates of the position of the motorized unit. This is a calibration procedure that can be followed regularly. This enables accurate measurements to be taken to structural elements (beams, columns, foundations, etc.) so that any deviations can be monitored. The distance meter is positioned at an offset to the rotational centre point of the camera or motorized unit. Therefore, the actual orientation and position of the distance meter in relation to the camera or motorized unit's absolute rotational centre point needs to be taken into account when calibrating the system - this is a function of the trigonometrical formulae.

[0077] Enhanced visual confirmation of points of measure can be achieved by integrating visual confirmation software that is provided with the Leica distance meter, with data and images generated by the Flir or Axis CCTV and thermal imagery cameras.

[0078] The Leica distance meter has its own on-board camera but it does not have the same quality as that of a Flir or Axis cameras, and therefore it has limitations. The distance meter's visual confirmation software includes cross hairs which enable a user to point at the exact position on a structural element before taking a measurement. During use of the present system, the cross hair function is integrated with the better quality camera of the Flir or Axis camera, so that the quality of visual confirmation of exactly where the measurement is taken can be improved.

[0079] Web based software is required, providing a portal interface for interactive wireless communication with the integrated system or model. The software may include user specific, automated reporting.

[0080] The integrated system or model requires a casing or housing. Industrial Applicability

[0081] The system and method disclosed herein have industrial application in the field of construction. Reference Signs List

[0082] In Figure 1 , the following references numerals have the meanings stated:

10. System for remote assessment of quality of construction of a structure.

1 1. Multi-storey building construction site.

12. Leica Disto D810 Touch laser distance meter.

13. Flir PT-602CZ (or Axis Q87-E) dual CCTV and thermal imagery camera.

14. Remote desktop computer.

15. Android tablet (or Raspberry Pi computer or Arduino device).

16. Mast.

17. Bluetooth link.

18. GSM link (Wireless internet protocol). Citation List

[0083] Citation List follows: Patent Literature

[0084] Nil.

Non Patent Literature

[0085] Azenha, M., Faria, R., & Figueiras, H. (201 1). Thermography as a technique for monitoring early age temperatures of hardening concrete. Construction and Building Materials, 25(1 1 ), 4232-4240.

[0086] Bhalla, S., Tuli, S., & Arora, R. (201 1 ). Defect detection in concrete structures using thermal imaging techniques. Experimental Techniques, 35(4), 39-43.

[0087] Griffin, O. M., Skop, R. A., & Koopmann, G. H. (1973). The vortex-excited resonant vibrations of circular cylinders. Journal of Sound and Vibration, 31 (2), 235-IN3.

[0088] Kim, C, Kim, H., & Ju, Y. (2009, June). Bridge construction progress monitoring using image analysis. International Proceedings of the 26th International Symposium on Automation and Robotics in Construction (ISARC 2009) (pp. 101-104).

[0089] Kim, C, Park, T., Lim, H., & Kim, H. (2013). On-site construction management using mobile computing technology. Automation in Construction, 35, 415-423.

[0090] Kwak, J. M., Choi, G. Y., Park, N. J., Seo, H. J., & Kang, L. S. (2011 ). 4D CAD Application Examples and Directions for Development in Civil Engineering Projects. International Proceedings of Economics Development & Research, 13. Rao, P. (2008). Infrared thermography and its applications in civil engineering. The Indian Concrete Journal, 82(5), 41-50.

[0091] Rao, P. (2008). Infrared thermography and its applications in civil engineering.

The Indian Concrete Journal, 82(5), 41-50.

Claims

[Claim 1] A system for remote assessment of quality of construction of a structure comprising a plurality of structural elements, said system comprising the following components:

primary data processing means;

[Claim 2] A system as claimed in Claim 1 , wherein the thermal imaging means comprises a thermal imagery camera, the camera system comprises a video camera system, and the thermal imagery and video camera are integrated with each other, providing a dual camera system.

[Claim 3] A system as claimed in Claim 1 , wherein the distance measuring means comprises a laser distance meter mounted in fixed relationship to the camera system.

[Claim 4] A method of assessing quality of construction of a structure comprising a plurality of structural elements, said method comprising the steps of:

(a) providing a system comprising the following components:

distance measuring means for measuring distances in relation to at least one of said structural elements; thermal imaging means for generating thermal images of at least one of said structural elements;

primary data processing means;

(b) performing a quality check on said structure, representative of at least one pre-determined juncture in time, by carrying out the following sub- steps:

(b1 ) determining an initial spatial reference co-ordinate for said system; (b2) assessing an actual setting out of at least one of said structural elements by taking linear measurements in relation to said initial spatial reference co-ordinate and said structural element using said distance measuring means; and

[Claim 5] A method as claimed in Claim 4, wherein the structural elements comprise concrete structural elements and the method includes assessing properties of said concrete by

providing a thermal design of said structural element;

overlaying said thermal design onto said background thermal image to generate a quality drawing; calculating temperature deviations between said thermal image and said thermal design, thereby to calculate thermal performance data; and displaying said data on said quality drawing.

[Claim 6] A method as claimed in Claim 5, which includes displaying in said quality drawing, in addition to the thermal performance data, data representative of (i) the actual setting out of the at least one structural element, (ii) the spatial design, and (iii) deviations between said data.

[Claim 7] A new system for remote assessment of quality of construction, substantially as herein described.

[Claim 8] A new method of assessing quality of construction, substantially as herein described.