Method of inspecting canopy structures

[0001] Canopy structures such as installed at vehicle fuel dispensing service stations typically have flat roofs supported by hollow vertical columns made of corrodible material such as steel. Such columns are often used as conduits for draining water from the flat roof, thus exposing the interior of the columns to corrosive deterioration and loss of strength needed to support the roof. Since the deterioration of the columns may be entirely internal, they can weaken to a dangerous condition resulting in a collapse of the canopy without the owner or operating personnel being aware of their dangerously weakened condition.

[0002] This invention provides a method of non-destructively inspecting canopy structures to determine their structural integrity and also to identify inadequacies or defects in the roof water drainage system. The method of inspection includes visual inspection to identify areas of deterioration or concern, impact and resonance testing of vertical support columns checking support column thickness using ultrasonic technology and may optionally also include inspection of the drainage system using fiber optic technology such as a fiberscope. Several methods of inspection are herein disclosed for a variety of canopy structures.

[0022] FIGS. 1 through 12 illustrate several types of vehicle fuel service station canopies to which the herein described methods of inspection can be beneficially applied. FIGS. 1, 2, 3, 4 and 5 show one type of canopy for a vehicle fuel service 31 station to which the herein disclosed method of inspection is advantageously applied. The service station includes a pair of fuel dispensing unit or modules 32, 33 mounted on concrete service islands 34, 36, respectively, which in turn are mounted on a concrete floor 37. The canopy 31 includes an elongated roof 38 supported on a pair of upright or vertical hollow steel columns 41, 42 of square or quadrilateral cross section the lower ends of which are embedded in and supported by the islands 34, 36 respectively. The roof 38 includes interconnected roof panels 43 secured to the underside of longitudinally extending horizontal steel roof stringers or channels 46, 47, 48, 49. The vertical support columns 41, 42 support a pair of steel I beams 51, 52 which in turn support the roof stringers 46, 47, 48, 49. The I beams 51, 52 rest on horizontal steel plates 53, 54 which seal off the top of the columns 41, 42. A façade 56 rims the roof 38. Water on the roof 38 drains into a central gutter 61 which in turn drains into the support columns 41, 42 through openings. One such opening 62 is shown in FIG. 3, their opposite sides facing the gutter 61. Water is discharged from the columns 41, 42 through openings 63 at their bottoms, only one of which is shown.

[0023] A second type vehicle fuel service station canopy 66 is illustrated in FIGS. 6 and 7. The canopy 66 includes three longitudinal roof stringers 67, 68, 69 supported by two transverse I beams 71, 72. The I beams 71, 72 are supported on hollow vertical steel columns 73, 74 mounted on fuel dispensing islands 76, 77. The roof 78 of the canopy 66 includes a pair of longitudinally extending gutters 81, 82 at its laterally opposite sides which drain to the support columns 73, 74 by way of laterally extending connecting gutters 83, 84, 86, 87. Openings 91, 92 are formed in opposite sides of the support columns 73, 74, respectively, for draining the water from the roof 78 via the connecting gutters 83, 84, 86 87. An opening 91 at the bottom of column 74 allows discharge of water from its interior. A similar opening, not shown is provided in column 73.

[0024] FIGS. 8 and 9 show an alternative discharge of water from the column 73 through a conduit 93 embedded in the island. In some service stations the canopy water is discharged from the support column underground with or without a storm sewer connection. Debris or other obstruction in such underground discharge systems can result in a back up of water in the steel support column with attendant corrosion or rusting of the column.

[0025] FIG. 10 illustrates a canopy 101 having gutters at laterally opposite sides, only gutter 102 of which is shown, which are interconnected to vertically disposed PVC pipes 103, 104 by laterally extending PVC pipes 106, 107, 108, 109. The pipes 106, 107 extend downwardly through the support columns 111, 112 and, as shown in FIG. 12, water is discharged from the lower end of the columns, in FIG. 12 shows a discharge elbow 113 at the lower end of the conduit 104. An opening not shown is provided in the support column 112 to allow discharge of water from the elbow 113. In a similar manner, water is discharged from the conduit 103 through an opening at the lower end of the support column 111. FIG. 11 shows a construction similar to that of FIG. 10; however, the lateral pipes 106, 107, 108, and 109 are boxed in with trough shaped members 116, 117, 118, 119 to improve the ceiling décor.

[0026] When the unprotected interior of the hollow steel support columns 41, 42, 73, 74, 111, 112 is exposed to moisture they will rust. The extent of the interior rust is hidden from view and thus the owner and operating personnel of the service station are not aware of the weakened condition of the support columns. Canopies have collapsed because of structural failure of the support columns due to excessive rust deterioration. The collapse of a canopy can be catastrophic with possible personal injury, property damage and fire. The herein disclosed inspection method reveals the location and extent of deterioration in the canopy support structure, thereby affording the owner and operating personnel the opportunity to take corrective action in a timely manner. Periodic inspections conducted according to the herein disclosed methods and timely corrective action minimizes risk of collapse of the canopy.

[0027] The method of inspection includes testing procedures which are designated to not interfere with normal operation of the service facility. Traffic flow and customer access to the fueling modules is not interrupted. Preferably a sketch showing a plan view of the canopy is developed showing critical dimensions such as canopy size, ground clearance and fascia height, support column dimensions and locations, fuel dispensing module locations and drains. Photographing the canopy from different angles is recommended.

[0028] An initial visual inspection is made of the canopy installation taking notes as to the canopy roof, its support structure and drainage, and noting whether the structural steel components are welded or bolted or a combination thereof. A determination is made as to how drainage from the roof is handled. The visual inspection includes a physical examination of the base of each support column, the top of each support column, all visible drains and the top of the canopy, observing the condition of the gutters, namely whether they are rusty or clogged with debris; and whether or not the discharges from the gutters to the support columns are clogged.

[0029] The method of inspecting canopies may include an impact and resonance test procedure following the visual inspection of the columns for holes, rust, and loose or defective paint. An initial impact test is conducted using an impact tool such as a ball and peen hammer. Each column is struck with the tool, as if driving a nail, at about the ear level of a person standing and doing the testing or at about four or five feet above the base of the column. A record is made of the impact test. Was it destructive? Was the sound a hollow or solid sound? Was there a sound of falling debris? If the initial test does not produce a destructive result, the impact test is repeated on the opposite side of the column at a height of about two feet below the initial test or at a height intermediate the lower end of the column and the height of the initial test.

[0030] It is preferred that the support columns be tested for wall thickness with ultrasonic testing equipment, after calibrating the thickness gauge of the ultrasound testing equipment. The column thickness readings at all four sides at the base of each column are recorded. If a thickness reading is not obtained near the bottom, the sensor is moved vertically up the column until a reading is obtained and the height at which the reading is obtained and its value are recorded. The last mentioned column thickness test procedure is preferably preformed on all four sides of the column at its top. It is also desirable that a recorded top to bottom scan of all four sides of each column be made producing graphs showing deviations in wall thickness. This is done using the scan mode of the thickness gauge of the ultrasonic testing equipment. The graph on the thickness gauge display is recorded by an image recording device or photographed and referenced as to location on the support column. This definitative examination is essential for an engineering analysis in evaluating the risk of a canopy collapse. FIG. 13 shows an ultrasonic thickness gauge 131 being used measuring the thickness of the column wall at one side of the support column 73 near its bottom. FIG. 14 shows an ultrasonic thickness gauge 131 being used to measure the thickness of the wall of the column 73 near its upper end and FIG. 15 shows the ultrasonic thickness gauge being used to measure the adjacent wall of the support column 73 just below the junction of the gutter 83 with the support column 73.

[0031] As shown in FIG. 16 a fiberscope testing device or equipment 141 is being used to observe, through opening 62, the interior of the upper end of the hollow support column 61 and, as shown in FIG. 17, the fiberscope testing equipment 141 is used to view the inside of the column drain 93 passing through the island 76. This allows the people performing the inspection to observe and record the nature of any clogged condition of the inspected components of the canopy drainage system. The fiberscope testing equipment includes a camera or image recording device 143 for recording images or pictures which are included in the written report of the inspection. It may be desirable to drill small diameter holes in the support columns in order to insert the fiber bungle or probe 144 into the interior of the vertical support columns, thereby permitting the inspector to view and record images of selected areas of the interior of the columns.

[0032] The scope of the canopy inspection is decided by the owner of the canopy and an appropriate plan or method of inspection is chosen to determine the integrity of the canopy support system. Each inspection plan includes a report of findings and recommendations of corrective action to remedy apparent or discovered deficiencies. If there is no apparent deterioration of the canopy support system a limited somewhat cursory plan of inspection may be chosen. One such cursory canopy inspection is performed by the method shown in FIG. 18 which includes the step of visually inspecting the canopy to identify areas of deterioration or concern and recording the location and nature of the deterioration. A cursory inspection includes ultrasonic testing of the thickness of the walls of the support column. The cursory inspection method also includes the steps of issuing a written report identifying the location and nature of the deficiencies in the canopy support system uncovered by the foregoing steps and issuing written recommendations as to corrective action to correct or remedy the deficiencies. The foregoing cursory inspection method may include issuance of written recommendations for maintenance of the canopy.

[0033] As illustrated in FIGS. 19 through 22, more comprehensive methods of inspection of the canopy can be performed to more precisely identify and evaluate parts of the support structure weakened by corrosion. A strategic scan mode ultrasonic thickness gauge analysis of strategic structural locations of the canopy is preferably included to identify flaws or defects at critical construction points such as at the bases of the support column and at the connections between the top of the support columns and the roof stringers or support beams. A top to bottom scan of laterally opposite sides, or all four sides, of each column to produce recorded graphs of wall thickness should also be conducted to provide data for a structural analysis of each column. An engineering analysis is conducted to determine the integrity of the existing canopy support structure based on structural characteristic found from the inspection with due regard for current applicable design techniques and requirements. In addition to such an engineering analysis, written recommendations for correction of deficiencies in the support structure are rendered.

[0034] The drainage of water from the roof through the hollow support columns provides the moisture conducive to rusting or corrosion of the inside of the hollow steel support columns. The method of inspection includes a visual inspection of the roof drainage system and, preferably, also includes fiberscope inspection with attendant image recordation, particularly images of stoppages, debris and areas of leakage. The inspection report includes a description of the drainage investigation, together with prints of recorded images.

[0035] The herein disclosed methods of inspecting canopies are designed to greatly reduce the risk of collapse of the canopy by providing timely information concerning possible deterioration in the canopy support structure. Each method of inspection preferably includes reporting the results of the inspection and recommendations for action to correct deficiencies in the support system revealed from the inspection. The reduced risk of canopy collapse, and probable reduction in insurance premiums, makes the inspection cost effective.