TANK INDUSTRY CONSULTANTS

Transcription

1 March 28, 2017 TANK INDUSTRY CONSULTANTS 7740 West New York Street Indianapolis, Indiana / Phone 317 / FAX Plainfield, Illinois 815 / El Paso, Texas 915 / Houston, Texas 281 / Pittsburgh, Pennsylvania 412 / Sacramento, California 916 / Mr. Tom Zimmerman, P.E. Terra Consulting Group, Ltd. 600 Busse Highway Park Ridge, Illinois RE: Mr. Zimmerman, via TZimm@TerraLTD.com Professional Antenna Review Services Associated with the Kenilworth Elevated Water Storage Tank And Proposed New Verizon Antenna Equipment City of Kenilworth, Illinois TIC H In fulfillment of Tank Industry Consultants (TIC) proposal of February 27, 2017, this report will summarize TIC s Structural Evaluation of the suitability of the Kenilworth Elevated Water Storage Tank for proposed new antenna equipment to be installed on the roof of the subject tank. This evaluation was based on documents provided by T-Mobile Northeast LLC. EXECUTIVE SUMMARY TIC concludes that the existing tank is not a suitable candidate for additional proposed new antenna equipment to be installed on the roof of the tank as described herein. TIC s structural evaluation calculations conclude that the existing anchorage of the tank to the concrete foundation would be overstressed by design wind loads on the tank in comparison to allowable anchor bolt stress criteria prescribed in AWWA Standard D100. The original drawings for the tank specified (16) 1-1/4 inch diameter anchor bolts. Field measurements made by TIC on March 22, 2017 found the existing anchor bolts to be 1-1/8 inch diameter. TIC calculations (See Appendix B of this report) conclude that the anchorage loads would be within acceptable limits for 1-1/4 inch bolts, but they are not for 1-1/8 inch bolts. In addition to the structural inadequacy of the anchorage, there were several safety-related conditions observed that should be corrected as described herein. DOCUMENTS REVIEWED BY TIC TIC reviewed the following documents provided by Terra Consulting Group, Ltd. in performing the structural evaluation of the subject tank: 1) Klein Hoffman review.pdf: (13) pages report of structural evaluation performed by Klein & Hoffman, Inc., dated March 9, An Employee-Owned Company

2 Structural Evaluation of Kenilworth Elevated Water Storage Tank Page 2 2) Sprint Analysis.pdf: (38) pages of structural calculations performed by Fullerton Engineering Consultants, dated March 28, ) Burns Report.pdf: (11) pages report on stability evaluation performed by The Burns Group, dated November 11, ) ATT Structural.pdf: (38) pages of structural calculations performed by Fullerton Engineering Consultants, dated September 26, ) Burns Engineering Review.pdf: (7) pages report on engineering review of stability calculations performed by The Burns Group, dated September 27, ) Burns Letter.pdf: (3) pages letter on review of water tower stability, dated October 21, ) Geotechnical Report.pdf: (27) pages geotechnical report for water tower foundation soil assessment by Wang Engineering, Inc., dated October 21, ) Verizon_332476_Kenilworth_WT_IL_Tower_Mapping.pdf: (66) pages tower mapping report by Hightower Solutions, Inc., dated February 9, ) Kenilworth Water Tank Photosim_ pdf: (2) pages photo simulation of tank before and after installation of proposed new antenna equipment by Verizon and Terra Consulting, undated. 10) Kenilworth Water Tower Plans Compressed1.pdf: (5) pages of original tank drawings by Universal Tank & Iron Works, Inc., dated January 9, OBSERVATIONS The subject tank was observed by TIC s Chad Mitchell and David Shoemaker on March 22, Photographs taken by TIC are included in Appendix A of this report. 1) The tank was in generally good structural condition. There were areas of isolated coating failures on the exterior surfaces and the interior surfaces that were accessible during TIC s observations on March 22 nd. (See photos 1, 49 50, 53, 59 67) 2) The tank foundation was in generally good condition except for chips, bug holes and exposed aggregate in some areas. Grout between the concrete foundation and the tank base plate ranged in thickness from 1-1/2 to 2-1/4 and appeared to be in generally good condition. (See photo 2) 3) The tank appeared to have been constructed in accordance with tank drawings by Universal Tank & Iron Works except as discussed herein. One significant difference was that the existing anchor bolts were measured to be 1-1/8 diameter with calipers whereas the drawings indicated 1-1/4 diameter anchor bolts. (See photos 57 58) 4) Ultrasonic thickness (UT) measurements were made on structural components of the tank and compared to the specified thicknesses on the original construction drawings. All UT measurements were made through the coatings on the tank. UT measurements and drawing specified thicknesses for the tank components are summarized below: a. Tank base plate: measured; 7/16 (0.438 ) specified; b. Base cone (or bell):

3 Structural Evaluation of Kenilworth Elevated Water Storage Tank Page 3 i. Ring 1 (bottom): measured; 7/16 (0.438 ) specified; ii. Ring 2: measured; 7/16 (0.438 ) specified; iii. Ring 3: measured; 7/16 (0.438 ) specified; iv. Ring 4 (top): measured; 1/2 (0.500 ) specified. c. Support column (shaft): i. Ring 1 (bottom): measured; 1/2 (0.500 ) specified; ii. Ring 2: measured; 1/2 (0.500 ) specified; iii. Ring 3: measured; 1/2 (0.500 ) specified; iv. Ring 4: measured; 15/32 (0.469 ) specified; v. Ring 5: measured; 15/32 (0.469 ) specified; vi. Ring 6: measured; 15/32 (0.469 ) specified; vii. Ring 7 (top): measured; 15/32 (0.469 ) specified. d. Roof and upper shell: i. Upper knuckle: measured; 5/16 (0.313 ) specified. ii. Lower knuckle: measured; 7/16 (0.438 ) specified. iii. Finger plates: measured; 5/16 (0.313 ) specified. iv. Cap plates: measured; 1/4" (0.250 ) specified. 5) There was a significant amount of antenna-related equipment on the tank and associated cables routed from the base of the tank to the roof. This equipment was concentrated inside the base bell of the tank and on a railing or corral-type structure at the center of the roof. A summary of the existing antenna-related equipment and cables is included on sheet 5 of the calculations in Appendix B of this report. This summary was excerpted from the document Verizon_332476_Kenilworth_WT_IL_Tower_Mapping.pdf provided to TIC by Terra Consulting and was used as the basis for the structural evaluation of the effects of the existing antenna equipment on the subject tank. Note that no specific information was provided about the additional equipment Verizon proposes to add to the tank. In lieu of specific design information about proposed new antenna equipment, TIC used the document Kenilworth Water Tank Photosim_ pdf to estimate the effects of the proposed new equipment in the calculations included in Appendix B. (See photos 3 17, 20 30, 32 56) 6) The antenna-related equipment and cables inside the base bell of the tank were generally well-organized, except where cables were suspended from the side rail bracket on the access ladder to upper levels of the tank. (See photo 15)

4 Structural Evaluation of Kenilworth Elevated Water Storage Tank Page 4 7) Antenna cables routed up the inside of the tank support shaft were generally wellorganized and did not interfere with safe use of the access ladder. Intermediate platforms within the support shaft had a significant amount of debris, probably related to antenna equipment installation and maintenance activities. (See photos 26 28, 32 35) 8) Antenna cables routed up the inside of the access tube between the tank support shaft and the roof of the tank interfered with safe use of the access ladder by severely constricting the space for use of the ladder and by preventing adequate toe space for climbing the ladder in accordance with OSHA regulations. (See photos 37 39, 41 42) 9) The majority of the otherwise safe walking space on the roof of the tank within the antenna railing or corral support structure was covered with antenna cables and brackets. This concentration of cables, brackets and other antenna equipment created numerous tripping hazards. The surface of the roof plate had numerous locations of coating damage and minor dings and dents due to the antenna equipment and the maintenance thereof. (See photos 43, 48 50) 10) The antenna equipment on the roof of the tank was generally supported on a railing or corral-type structure comprised of a top rail, a mid-rail and vertical posts, all fabricated of 1-3/4 round tubing and of welded construction. The top rail was 4 6 above the roof of the tank. The vertical posts were attached to the roof of the tank with pinned base plates to adjust to the contour of the roof. The base plates were attached to the roof using 3/8 diameter stainless steel welded studs with caulking around the perimeter of the base plates. The railing was furnished with a 4 x 1/4 toe plate. The gap between the bottom of the toe plate and the roof of the tank varied from approximately 1/2" to 4 around the circumference of the railing. Note that current OSHA regulations require a maximum gap of 1/4" between the bottom of the toe plate and the roof of the tank. Coatings on the railing components and base plates were damaged in many areas and no longer providing effective corrosion protection. (See photos 43 46, 51 56) CONCLUSIONS 1) TIC evaluated the effects of the existing and proposed new antenna equipment on the overall structural stability of the tank. TIC calculations are included in Appendix B of this report. The effects of the existing and proposed new antenna equipment on the overall structural stability of the tank were evaluated for two cases due to the discrepancy between the anchor bolt size specified on the original construction drawings, i.e. 1-1/4 diameter, and the anchor bolt size, i.e. 1-1/8 diameter, measured by TIC using calipers on March 22 nd. Based on TIC s calculations, 1-1/8 diameter anchor bolts would be overstressed by approximately 13% using AWWA D100 allowable stress criteria, for the existing antenna equipment. This calculated overstress would increase to approximately 19% considering the estimated effects of additional new antenna equipment and antenna support structure proposed by Verizon. 2) The calculations in Appendix B of this report were based on the following assumption and observations:

5 Structural Evaluation of Kenilworth Elevated Water Storage Tank Page 5 a. The weight of the empty tank with no antenna equipment was based on information on Universal Tank & Iron Works construction drawings for the subject tank. TIC field UT measurements confirmed that the actual tank thicknesses are consistent with the thicknesses specified on the construction drawings. (See sheet 1 of calculations) b. Wind loading on the tank was assumed to be in accordance with the provisions of AWWA D100. Wind loading effects were first evaluated considering an empty and bare, i.e., no antenna equipment, tank. (See sheet 2 of calculations) c. The effects of wind loading on an empty tank with the existing antenna equipment was then evaluated. The existing antenna equipment and associated cables were assumed to be as described on pages 7 8 and 23 24, respectively, of the Antenna Mapping Report prepared by Hightower Consulting, dated February 9, (See sheets 3 and 5 of calculations) d. The effects of wind loading on an empty tank with the existing antenna equipment and the proposed new equipment was then evaluated. No specifications for new antenna equipment were provided for TIC s evaluation. For the purposes of this evaluation, TIC estimated the effects of the proposed new equipment based on a photographic simulation of the tank appearance before and after the addition of proposed new antenna equipment. (See sheets 4, 6 and 7 of calculations) e. The effects of the increased overturning moments on the tank anchor bolts due to the existing and proposed new antenna equipment on the anchorage were then evaluated, first for the 1-1/4 diameter anchor bolts specified on the construction drawings and then for the 1-1/8 diameter anchor bolts measured in the field. (See sheets 8 and 9 of calculations) 3) TIC performed a cursory review of the antenna railing support structure on the roof and concluded that it appeared to be structurally adequate for the existing antenna equipment as long as all components of the railing and its attachments to the tank roof are maintained in as-built condition. However, deterioration or deformation of the railing and/or attachment components, if undetected or not corrected, could lead to failure of the railing support structure under high wind conditions. RECOMMENDATIONS 1) TIC recommends that no new antenna equipment or cables be added to the subject tank as this would increase the risk of failure of the anchorage system and increase safety hazards for personnel accessing the roof of the tank. 2) TIC recommends that all existing antenna equipment other than essential police or fire department equipment be removed from the tank and that the tank coatings be repaired to restore adequate corrosion protection. 3) TIC recommends that, unless and until the external antenna equipment is removed from the tank, a visual inspection be performed immediately following any severe storm or extreme high wind conditions, such as those due to a tornado or hurricane, as antenna

6 Structural Evaluation of Kenilworth Elevated Water Storage Tank Page 6 equipment, mountings and cable trays/ladders have been known to experience damage in such extreme conditions. Loose or broken components can become projectiles in these high wind conditions and pose a risk to the public and to adjacent structures, vehicles and equipment. 4) No structural modifications or repairs to the subject tank are recommended at this time. Although TIC s calculations indicated an approximate 2.8% overstress of the 1-1/8 diameter anchor bolts for an empty tank with no antennas, this calculated overstress is not significant and is within the accuracy of the analysis performed. Please contact me at (815) or lieb@tankindustry.com if you have any questions. Sincerely, Tank Industry Consultants, Inc. John M. Lieb, P.E. Chief Engineer Cc: Stephen W. Meier, P.E., S.E./Gregory R. Chip Stein, P.E. TIC, Indianapolis Sabrina Fleming TIC, Plainfield