Evaluation - CivicWeb

A DIVISION OF 594798 Alberta Ltd

100, 221 – 62 Ave SE, Calgary, Alberta T2H 0R5 Phone: (403) 255-6040 Fax: (403) 255-6043 email: [email protected]

October 14, 2016 Mr. Lloyd Smith Director of Leisure Services City of Fernie 501-3rd Ave., Box 190 Fernie BC V0B 1M0 Dear Mr. Smith,

Re: Project 16088-T2 – Fernie Fire Hall Roof Structure – Structural Evaluation

Thank you for retaining our office to carry out the review of the structural capacity and condition of the existing Fernie Fire Hall located at 692 – 3rd Avenue, Fernie, BC. The purpose of the review was to visually assess the structural condition of exposed members, assess the load capacity of the existing roof structure, and provide recommendations for any required reinforcements. Detailed design of reinforcement for the roof structure is beyond the scope of this report. A site visit was conducted on September 23, 2016 to assess the existing condition, and confirm member sizes and dimensions. The building was originally constructed in 1970 as a Firestone Tire & Rubber Company service garage and was converted for use as a fire hall in 1979. It is understood that the roofing system was modified circa 1997 in order to upgrade the roof insulation. A structural assessment of the roof structure was completed by Armstrong Engineering and Land Surveying on October 29, 1997 (file number 4139) at that time to confirm the capacity of the existing roof considering the new roofing system. In this report, several recommendations were made for reinforcing and modifying existing members to comply with 1995 design loads. The report also imposed a maximum height of 20” for roof snow as an alternative to the structural modifications. It is understood that only the recommendation for roof snow removal has been implemented and the structural modifications have not been implemented. Analysis Parameters Codes:

• Design loads for the existing structure as per the National Building Code 1970 (NBCC 1970).

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• Design code and member capacity as per the Timber Design Manual Design Manual 1970 (CSA O86-1970), Steel Structures for Buildings (CSA S16-1969).

Design Loads:

• Superimposed roof dead loads: 0.72 kPa (15 psf)

• Roof snow load: - 2.30 kPa (48 psf) based on 1970 code with exposed condition - 1.52 kPa (32 psf) based on 20” snow height removal limit - 4.37 kPa (91 psf) based on 2012 code with sheltered condition (for

comparison purposes)

• Roof live load: 1.00 kPa (21 psf)

• Wind load: 1 in 30 year pressure of 0.43 kPa (9 psf)

• Walkway and storage cabinets suspended from OWSJ: 2.40 kPa (50 psf)

Record Drawings and Original Design Loads:

• The following record drawings were available for review: - Architectural record drawings as issued in 1970 by the Real Estate

Department of Firestone Tire & Rubber Company - Structural and architectural record drawings as issued on October 1979 by

Mecman Engineering & Testing Ltd

• Structural record drawings for the original building in 1970 were not available for review, but are referenced by the 1997 report by Armstrong Engineering and Land Surveying

Existing Geometry (refer to Appendix A for roof framing sketch):

• One story building approximately 36.4 m long x 15.2 m wide x 6.45 m high.

• Tongue and groove 2” thick roof deck decking spanning east-west supported by steel OWSJ spanning north-south. Material grade considered as Commercial Spruce Fir based on 1997 structural report reference to record drawings.

• Roof Open Web Steel Joist (OWSJ): - Supported on exterior and interior concrete block walls on west side, and

on a W360x39 steel beam and exterior concrete block walls on east side. - 1.78 m to 2.15 m spacing centre to centre between joists - 9.1 m span with two lines of bridging for north OWSJ and 5.6 m with one

line of bridging for south OWSJ - 460 mm deep steel joists with hat sections for top and bottom chords and

21 mm diameter rod for diagonals - 248 MPa yield strength considered based on typical historical sections at

time of construction


• W360x39 beam supporting OWSJ on east side is supported by a W150x22 column adjacent to concrete block wall on east end and directly on the interior concrete block wall on west end.

• Double C200x17 lintel beams on north wall are provided over overhead door openings and supported by W200x46 columns.

• 300 mm wide exterior concrete block walls supported on strip footings

• 300 mm and 150 mm wide interior concrete block walls (foundations could not be confirmed based on available record drawings)

• Mezzanine walkway and storage cabinets on west side of building are supported by brackets into the interior block wall and tie rods suspended from the OWSJ.

Application of Snow Loading on Roof The current roof structure was originally designed per the NBCC 1970 for a 2.30 kPa (48 psf) snow load as referenced in the 1997 structural report. This loading is based on an exposed condition assuming no obstructions higher than the roof within a distance of 10*h, where h is the height of the obstruction above the roof level. Since the building was constructed, subsequent building code editions have increased the ground snow load for Fernie, BC, introduced a 1.15 importance factor for post-disaster buildings, and restricted use of exposed conditions for non-post-disaster buildings only. The design snow load as per the BC Building Code 2012 considering these restrictions is 4.37 kPa (91 psf). This represents a 90% increase from the original snow load. As per Commentary L – Application of NBC Part 4 for the Structural Evaluation and Upgrading of Existing Buildings, an existing building designed and built in accordance with a previous building code can be considered to have demonstrated satisfactory capacity to resist loads other than earthquake provided:

• Examination by a professional engineer does not expose evidence of significant damage, distress or deterioration

• Structural system is reviewed, including critical details, and checked for load transfer

• Building has demonstrated satisfactory performance for 30 years or more

• No changes within the past 30 years that could significantly increase the loads on the building or affect its durability, and no such changes are contemplated

Based on the record drawings, the original roof system from 1970 is described as “steel joists, wood or steel deck, rigid insulation, asphalt, felt & gravel”. It is understood that the building was renovated in 1997 to upgrade the roof insulation and re-roof. This


modification has the potential to increase the snow load acting on the roof if the original insulation may have been insufficient to prevent melting of snow on the roof due to heat loss. As a maximum roof snow height of 20” was imposed in 1997, it cannot be confirmed if the current structure renovated in 1997 would perform under a full snow load. On this basis, the structure can only be judged for satisfactory performance over a period greater than 30 years based on the 20” roof snow height limit. The use of a snow removal procedure in lieu of structural reinforcements poses risk for life safety and should only be considered on a short term basis. Failure to remove snow from the roof in an adequate manner can result in catastrophic consequences. It should also be noted that the current building code requires a higher level of life safety for post-emergency buildings such as fire halls which the original codes do not require. The existing roof structure has been analyzed for the original 1970 building code loads as well as the reduced snow height of 20” considering the current snow removal procedure. Results 1. Roof deck The existing roof deck was found to be sufficient for the original loading imposed on it. Visual inspection of the underside of the exposed deck did not show any signs of distress or moisture damage. 2. Roof Open Web Steel Joist (OWSJ) The existing joists did not show any signs of distress or damage based upon visual inspection of the exposed and accessible sections. The joists within the southwest corner of the building could not be inspected due to gypsum ceiling finishes within the mezzanine office area. Refer to photo 1 for a typical north joist within the truck area. The existing joists were found to be sufficient for the original 1970 snow loading. As a comparison, the 2012 snow loads were also checked and several members were found to have insufficient capacity. Several diagonal chords are overstressed by 11% to 280% and the top and bottom chords fail by 41% and 140% respectively. These results are consistent with the 1997 structural report. It should be noted that several joists also had concentrated loads from a suspended walkway and storage cabinets. The architectural drawings from 1970 do not show this walkway and it is likely that it was added after the original construction. No local reinforcement was observed on any joist for the additional loading. These joists were


verified for the concentrated loads and found to be adequate based on 1970 snow loads. Refer to photo 2 for the suspended walkway attachment to the joist. Our calculations show that the south joists are structurally adequate for the original snow loads.

Photo 1: Typical joist spanning north-south

Photo 2: Rod attachments to joist for cabinets and walkway


3. W360x39 roof beam The original loading on the east-west interior steel beam supporting the joists exceeds the member bending capacity by 240%. Even considering the maximum roof snow height limit of 20”, the beam is still overstressed by 160%. Additionally, the current beam does not have any restraint for twisting at the column support and a bolt for the connection to the column top plate is missing. Refer to photo 3 below for details.

Photo 3: Beam support at W150 column

4. W150x22 end column supporting roof beam The existing column is laterally unbraced for its full height and is not acceptable structurally due to excessive slenderness of the section. By attaching the column to the adjacent exterior concrete block wall with brackets and locally reinforcing the block wall, the column capacity can be increased to an acceptable level for the original loads. There was no evidence of previous lateral support angles attached to the existing masonry that were removed and it is likely these supports were missed in the original design or construction. Refer to photo 4 for details.


Photo 4: Column unsupported laterally for full height

5. Double C200x17 lintels and W200x46 columns The existing lintels and supporting columns along the north wall were found to be adequate for the original design loads. No signs of distress or damage were observed. 6. Roof structure above lounge area Based on the architectural record drawings, the roof within this area is supported by 12” joists. The material of construction is not specified on the drawings and the structure could not be verified during the site review due to the gypsum ceiling. The ceiling should be cut locally and the structural supports sizes and spacing should be determined for the roof capacity to be evaluated. 7. Exterior and interior concrete block walls The exterior concrete block walls on the north and south walls as well as two interior concrete block walls support the roof joists. Cracking was noted at some of the joists at the 150 mm wide concrete block interior wall. This is consistent with findings of the previous 1997 structural report. Refer to photo 5 for cracking noted on an interior block wall. The cracking is likely due to the block wall acting as an intermediate support for


the joist. The concrete block was built up around the joist without allowing for a gap, which changed the load path from the original design intent and introduced loading into the block wall. Additionally, large vertical cracks extending through the height of the 300 mm wide interior block wall were observed adjacent to the existing mandoors with horizontal separation of the blocks. The cracks were noted to be wider in the top of the wall and narrowing down along its length. Refer to photos 6 and 7. Cracks widths vary from 7.5 mm to 18 mm and have resulted in horizontal separation of the blocks as well as cracks through the cross section of the blocks. The cracks do not appear to be recent based on an adhesive paper on the crack noting its size increase over the years. The cracks may be due to uneven foundation settlement along the wall length or lack of sufficient control joints. The addition of the mezzanine and walkways may also have introduced additional loading which the block wall was not originally designed for.

Photo 5: Cracking at 150 mm wide interior block wall


Photo 6: Vertical crack beside mezzanine mandoor

Photo 7: Vertical crack on main floor interior block adjacent to mandoor


Recommendations Based on the site review and calculations, the existing roof structure does not have sufficient capacity for the original 1970 design loads. As a minimum, it is recommended that the roof structure is immediately upgraded to comply with the original 1970 design loads as per the requirements listed below. As there has been no change in occupancy since 1979, it is not required by code to upgrade the building to comply with 2012 snow loads. However, given the importance of the fire hall and its use for emergency situations, it is recommended that the building is upgraded to comply with the latest 2012 building code. The current snow removal policy for roof snow depths greater than 20”, should only be used as a temporary measure until the reinforcements are incorporated. Snow removal is not a good alternative to the structural reinforcements. Failure to remove the snow due to unexpected delays could lead to failure of the roof system and catastrophic consequences. This is especially critical considering the building’s role in emergencies and the consequences of the loss of this facility. In order to withstand 1970 snow loads, the following are required:

1. Reinforce W360x39 roof beam: the existing roof beam does not have sufficient capacity in bending even without any snow load on it. It is critical that the top and bottom flanges of the beam are reinforced and that vertical stiffener plates are provided at the column support to prevent twisting as soon as possible. Any snow on the roof within the eastern joists supported on this beam should be removed until the repairs are complete. Refer to Appendix A for the extent of snow removal required. Finally, the connection of the beam to the top of column should be verified for any welds. The missing bolt may have been replaced during construction with welding, but this could not be confirmed during the original site visit. If additional welding from the beam to the column has not been provided, the missing bolt should be installed or additional welding should be provided.

2. Install bracket from W150x22 column to adjacent block wall: the steel column adjacent to the east block wall is laterally unsupported for its full height and is inadequate due to excessive slenderness. Additional reinforcement and brackets attaching to the adjacent concrete block wall must be installed near the top of the column to provide lateral support. The concrete block should also be corefilled at the bracket location. This repair is urgent and should be carried out as soon as possible due to the potentially catastrophic consequences of the column failing.


3. Confirm roof members and spacing in southwest area: the roof framing could not be verified for the higher roof level in the southwest section above the existing lounge area due to the drywall ceiling. Openings should cut into the ceiling in order to verify the existing framing and evaluate the roof capacity in this area.

In order to upgrade the building to 2012 snow loads, the following are required:

4. Reinforce existing joists: upgrading the existing joists would require reinforcing the diagonals, and top and bottom chords with additional steel welded to these sections. Based on the member capacities, addition of an intermediate joist between existing joists would reduce the extent of reinforcement required, but would not eliminate it completely from the existing joists.

5. Additional reinforcement to W360x39 roof beam: the extent of reinforcement required to upgrade the existing beam would be increased compared to the 1970 loads.

In addition to the reinforcements, the following repairs are recommended:

6. Remove concrete blocks and provide gap at intermediate joist support: the blocks in the 150 mm wide wall should be removed from around the roof joists in order to allow the joists to deflect under load. The block can then be re-installed between the joists, leaving a gap for joist deflection.

7. Re-point and re-grout cracked interior concrete block walls: the cracked interior concrete block walls should have the mortar in the cracks ground out and re-pointed to restore the wall’s integrity. The wall should be monitored for further cracking.

The recommendations above should be designed and implemented as soon as possible to ensure life safety compliance of the building. It should be noted that even with the current snow removal procedure of limiting the snow height to 20” that several members do not have sufficient capacity for the 1970 design loads. We would be pleased to provide further recommendations and detailed design of the required reinforcements. Respectfully, Kassian Dyck & Associates, Consulting Engineers A Division of 594798 Alberta Ltd. Reviewed by: Kathleen Fritzsons, P.Eng. Arno Dyck, M.A.Sc., P.Eng.

16088-T2 - Fernie Fire Hall Roof Structural EvaluationAppendix A

W150X22COLUMN

300 mm WIDEEXTERIORCONCRETEBLOCK WALL(TYP.)

300 mm WIDEINTERIORCONCRETE BLOCKWALL (TYP. UNO)

150 mm WIDEINTERIORCONCRETE BLOCKWALL

460 mm DEEP OWSJ

305 mm JOISTS FOR UPPER ROOF (BASED ON ARCHITECTURALRECORD DRAWINGS, TO BE CONFIRMED)

W200X46 COLUMNS(TYP. 6 LOCATIONS)

2-C200X17 LINTELS(TYP. 5 LOCATIONS)

W360x39

Item 4: reinforce existing joists or installadditional joists up to 2012 coderequirements

Item 2: install brackets from W150x22column to adjacent block wall

Item 1: reinforce W360x39 roof beamand remove all snow load on joistssupported on this beam untilreinforcement is installed (hatchedblue area)

Item 5: additional reinforcement forW360x39 roof beam for 2012 snowloads

Item 3: confirm roof members andspacing in southwest area

Item 7: re-point and re-grout crackedinterior concrete block walls.

WALKWAY ANDCABINETSSUSPENDEDFROM OWSJ

Existing Roof Plan

Item 6: remove concrete blocks locallyand provide gap from joist atintermediate support

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