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HomeMy WebLinkAboutAttachment D - Lindley Center - 2022 Structural Assessment Structural Assessment, Site Findings and Recommendations for the City of Bozeman’s Lindley Center 1102 E Curtiss St. Bozeman, MT 59715 Reported to: Mike Gray, Facilities Superintendent Max Ziegler, Facilities Project Coordinator Prepared by: Morrison-Maierle, Inc. Project #: 0417.091 Rebecca Scheetz, PE Austin Batson, EI Jay Fischer, PE Spring 2022 Page 1 of 10 BACKGROUND The Lindley Center is owned and maintained by the City of Bozeman and serves as a community gathering space that is available for the public to rent for meetings, functions, receptions, etc. The original log-framed structure was built on a stone foundation, and several additions and remodels have been completed since its original construction in 1937. The main level is approximately 2680 sq ft and consists of an assembly area, a kitchen, restrooms and an office. See Figure 1. The basement is approximately 2000 sq ft and it is likely the basement was not part of the original structure. Previously the basement was used as locker rooms and a mechanical space, and today the basement primarily serves as mechanical and storage space. Reference the Structural Assessment Report prepared by Stahly Engineering & Associates, Inc. for the City of Bozeman in 2014 (Appendix C) for additional background information on facility use. Figure 1: Main assembly area and kitchen (beyond) at the main level. In January of 2022, the City of Bozeman requested a visual Structural Assessment of the Lindley Center to support and inform upcoming facilities renovations. At the time of the assessment, Structural Construction Documents were not available, nor were any record drawings from previous renovations, remodels or additions. This report outlines the visible existing conditions at the Lindley Center, identifies potential hazards associated with its current condition, and provides options for renovations / repairs and the estimated cost associated with each. ON-SITE OBSERVATIONS AND IDENTIFICATIONS OF AREAS OF CONCERN The overall objective of this assessment to identify areas of structural concern and provide recommendations by which the City of Bozeman may manage and / or monitor these areas accordingly. We understand the objectives of this structural assessment to be as follows: 1) To conduct a visual condition assessment of the structure. 2) To obtain photographs of the structure to document its current condition. 3) To obtain photographs and measurements of components of the structure to aid in future analysis efforts if necessary. Page 2 of 10 4) To use the information obtained to develop a system to help the City of Bozeman manage and mitigate immediate and / or long-term safety concerns with this structure. 5) To provide the City of Bozeman with options for renovations / repairs and the estimated cost associated with each. STRUCTURAL SYSTEMS Morrison-Maierle structural engineers Rebecca Scheetz, PE, and Austin Batson, EI, arrived on site at approximately 9:00AM on Monday, January 24th to perform a visual structural assessment Lindley Center. We met with Max Ziegler of the City of Bozeman to discuss the areas to be observed. Max accompanied us through the building during the assessment. The following figures (Figure 1 and 2) by Stahly Engineering & Associates, Inc. give an approximate layout of the different framing areas at both the floor and roof levels of the Lindley Center. Figure 2: Lindley Center Floor Framing (Stahly, 2014) Figure 3: Lindley Center Roof Framing (Stahly, 2014) Page 3 of 10 As a result of the building’s history of additions and remodels there are multiple framing systems through different parts of the building. We have established the following structural systems based on our onsite observations and on the report by Stahly Engineering & Associates, Inc. (2014). Floor Level Framing Systems 1 Area Framing System Description Area 1 Concrete slab. The depth of the slab and the presence of reinforcing were not determined during this assessment. Based on similar construction, the depth of the slab is assumed to be 4" and it assumed to be reinforced with #4's at 12" on center each way (Stahly, 2014). The concrete slab is supported by exterior foundation walls and a buit up triple 2x8 beam. The built up beam is supported by the exterior wall, a 6x6 post and an 11"x16" concrete column. The presence of reinforcing in the concrete column could not be confirmed during this assessment. Area 2 1x8 T&G decking over 2x6 rough sawn joists supported by exterior walls and 7" diameter log framing. This area also includes unsheathed non-bearing framed walls. Area 3 Stair opening infilled with plywood decking over 2x4 joists. Framing is supported by concrete walls, infilled framed walls and 2x support beams. Area 4 1x8 T&G decking over 2x8 joists supported by concrete walls. 2 Floor framing typical all other areas 1x8 T&G decking over 2x8 joists. The joists are supported by concrete walls, framed walls, B.U. 2x beam lines, 6x6 beams, 7" diameter log beams and one W10x15 steel beam. The beams span to concrete walls, 6x6 posts, 7" diameter log columns, one steel pipe column, one 11"x16" concrete column and one 2'-0"x2'-0" square footing. There is also a stone fireplace that bears directly on the soil in the crawlspace of this area. 2 Key Notes: 2. Access to the structural elements was limited in crawl space areas. 1. Information presented is based on onsite observations as well as information given in the report by Stahly Engineering & Associates, Inc., 2014. See Figures 1 and 2 for more information. Page 4 of 10 The most concerning structural issues identified in the Lindley Center were the lack of positive connections at several vertical bearing points and the lack of any visibly apparent identifiable lateral system. The report by Stahly Engineering & Associates, Inc. also identifies several members / connections that are significantly overstressed, and at least one of these locations appears to be visibly deflecting under its current loading conditions. Other issues observed include isolated locations throughout with varying degrees of water damage/staining, discoloration, degradation, and general wear. The foundations of this building are a combination of stone, concrete and concrete masonry units (CMU). The original structure was most likely built on a stone foundation without a basement, and the concrete basement walls were likely poured during a remodel to create the basement space and to reinforce the stone foundation, and the CMU walls were likely added to replace the stone foundations in areas that had failed (Stahly Engineering & Associates, Inc., 2014). The foundations and basement slab show signs of wear and irregularities that are typical for this age of concrete, including water staining, spalling, cracking and general wear, but do not appear to have major structural issues that have not already been addressed during a previous remodel. The report by Stahly Engineering & Associates, Inc. indicates limited isolated locations where Roof Level Framing Systems 1 Area Framing System Description Area 1 Wood decking over handmade rough sawn 2x4 trusses at 2'-0" on center. The individual 2x4 truss members are connected with nails. The trusses are supported on the exterior wall and on a built up triple 2x12 beam at the shared framing line between areas 1 and 2. 2 Area 2 Wood decking over 3-4" diameter logs strengthened by a flat 2x6 below at 2'-0" on center. The built up beams are supported on the exterior wall and on a built up triple 2x12 beam at the shared framing line between areas 1 and 2. It is assumed that there are headers over the large windows at the exterior wall. 2 Area 3 Wood decking over 3-4" diameter logs strengthened by a flat 2x6 below at 2'-0" on center. The built up beams bear on interior and exterior walls. 2 Area 4 Wood decking over 3-4" diameter log rafters spanning from a 7-8" diameter log ridge beam to the interior walls and are supported at mid span by a 7-8" diameter log. The rafters are supported by two 7-8" diameter log headers at the openings between areas 4 and 5. There are three bays of similar framing in Area 4. The ridge beams bear on two log trusses supported by columns and on the two former log-course end walls from the original construction of the building. 2 Area 5 1x8 T&G decking over 3-4" diameter log rafters at 2'-0" on center. The rafters are supported by interior and exterior walls and by two 7-8" diameter log headers at the openings between areas 4 and 5. It is assumed that there are headers over the large windows at the exterior wall. These rafters are exposed from below. Area 6 Wood decking over handmade rough sawn 2x6 trusses with 2x4 webbing at 2'-0" on center. center. The individual truss members are connected with nails. The trusses are supported by interior and exterior walls. 2 Key Notes: 1. Information presented is based on onsite observations as well as information given in the report by Stahly Engineer & Associates, Inc., 2014. See See Figures 1 and 2 for more information. 2. Access to the structural elements was limited in areas covered by ceiling panels. Page 5 of 10 foundation may need to be reinforced or replaced. Our structural assessment did not include the observation of the existing buried concrete foundation footings. It is assumed the concrete foundation footings are constructed below frost level on suitable bearing soil. We did not observe conditions that would indicate settlement, differential settlement, frost heave, or conditions associated with bearing failure of the concrete foundation footings. See Figures 4 and 5 for typical stone foundations and wood column base connections. The floor structure largely consists of wood decking over wooden joists and beams. The wood framing is primarily supported by wooden 6x6 posts, wooden 7” diameter log columns, and concrete walls. According to the analysis performed by Stahly Engineering & Associates, Inc. (2014), the triple 2x8 built up beam in Area 1 is 230% overstressed in a fully loaded condition. Though this assessment does not include analysis of the existing structure, it was noted that this member is separating and that the splice and bearing connections appear insufficient for a member of this length and type. See Figure 6. Figure 4: Stone foundation viewed from the exterior. Figure 5: Basement slab and typical wood column-to-slab connection. Figure 6: Triple 2x8 floor beam in Area 1. Figure 7: Typical floor beam-to-column bearing connection. Page 6 of 10 There are several load-path related unknowns at the basement level that are of structural concern. There is a load transfer issue at the beam to column bearing connections, where the connections were constructed to transfer vertical (bearing only) loads and do not have capacity to adequately transfer lateral loads. Additionally, the column base connections were cast into concrete and a positive connection could not be verified. See Figure 5. There are also locations throughout where the load path is unclear, and there are several locations where the connections are shimmed and appear to be insufficient. See Figures 7 and 8. The framed walls in the basement are unsheathed and do not provide a lateral load path to the foundations; it is assumed that the lateral load is resisted through the exterior foundation walls at the basement level. The framed walls also lack anchorage to the foundations. See Figure 9. There also is one location under the restrooms where the bottom plate has been crushed and appears to have rotted and / or degraded away. The structural intent for this wall could not be verified during this assessment. See Figure 10. The exterior of the building is framed with log-coursed bearing walls, and the interior walls are assumed to be standard-framed stud walls. Our structural assessment did not include destructive Figure 10: Crushed/degraded bottom plate at the basement level Figure 9: Bottom plate is not anchored to concrete foundation Figure 8: Insufficient / shimmed connection at floor joist bearing on concrete wall (lack of positive connection) Page 7 of 10 investigation to verify that the wall framing at the floor level is sufficient to support the roof elements that it supports. Additionally, as mentioned previously, the structure does not have a visibly apparent lateral system. A more in depth and likely destructive investigation may be required to determine if the framed and log-coursed walls have adequate lateral capacity and connections to handle both seismic and wind lateral loads. Another concern with the log-coursed exterior shell of the building was the deterioration observed at exposed ends of the exterior log framed walls. This assessment did not include a full quantification of the extent of the deterioration nor its effect on the structural members and their connections. There are also several envelope- related concerns at or near the log-coursed walls around the perimeter of the building. The roof structure primarily consists of log rafters (Figures 12 and 14) and hand-made trusses (Figure 13). Access to most of the structural elements observed at the roof was limited, but those which were visible appear to be in good condition without excessive checking or water damage. According to the analysis performed by Stahly Engineering & Associates, Inc. (2014), the Area 1 2x6 are 274% overstressed in a fully loaded condition, the Area 6 2x6 trusses are 169% overstressed in a fully loaded condition, and the triple built up 2x12 beam between Areas 1 and 2 is 730% overstressed in a fully loaded condition. A positive connection to the triple built up 2x12 beam could not be verified, and the ceiling below the beam appears to be visibly deflecting, though it was not possible to determine if the ceiling is deflecting or if the triple 2x12 beam is deflecting. See Figure 11. The Stahly report also reports that the nailed connections joining the truss members are deficient. Figure 11: Concealed triple built-up 2x12 roof beam between Area 1 and 2 with visible deflection Figure 12: Area 3 roof framing and roof deck Page 8 of 10 See supporting photos in Appendix B attached for more information. RECOMMENDATIONS We have developed a table to summarize the areas of structural concern, recommendation options, and a cost estimate range for each. See Appendix A. In the table, we have used a system to categorize the visible structural deficiencies and our level of concern with each as follows: A) Safety Concerns B) Mild / Moderate Damage / Wear C) Envelope or Aesthetic Concerns (Non-Structural) In order to prioritize our top concerns, we have also identified a tiered ranking system to categorize our recommendations as follows: A) “HP” items are High Priority structural items where our observations made indicate that the element(s) is / are perceived to be severely degraded, deficient, overstressed and / or provide support to large portions of the structure. We highly recommend these items be verified / reinforced / repaired as soon as possible, B) “P” items are other Priority structural items where our observations made indicate that the element(s) is / are perceived to be degraded, deficient, overstressed and / or provide support large portions of the structure. We recommend that owner prioritize these items based on project timeline and available funding Figure 13: Typical Area 1 and 6 rough sawn 2x4/2x6 roof trusses. Figure 13: Typical Area 4 roof framing and roof deck. Page 9 of 10 C) “D/W” are structural items which appear to be damaged or worn. These items will require minimal upgrades or simply continued monitoring. D) “OD” items are those which are not concerning from a structural standpoint at this time but were included for the owner’s review and information. It should be noted that the above-mentioned categories are provided for the purpose of indicating perceived risk by the observers and were developed based on the information and access to the structure provided at the time of observation. Access to the structural framing elements was limited to the bottom of the members in most cases, and there were many parts that were not accessible at all without performing a destructive investigation. Access to the structural elements observed was also limited by space and time restraints, and all parts of the structure could not be observed in detail for minute deficiencies. The observations provided are intended to highlight those areas of current and, in some cases, critical concern. We also recommend that the City consider the vulnerability of the 1930’s design and construction, including additions, remodels and modifications, as well as the inevitable uncertainties involved in the assessment of an approximately eighty-five-year-old structure, in their long-term planning actions. See the appendices to this report for descriptions of the areas of concern observed, recommendations for each and associated photos. It should also be noted that several items in the Summary Table are marked with Key Note 3. This indicates that the total cost of these items may exceed than the estimated cost provided in the event that additional modifications are found to be necessary based on the provisions given in the 2018 International Existing Building Code (IEBC). Per the 2018 IEBC, the extent of the repairs performed and classification of the work will dictate the full extent of the alterations required for code compliance. Please do not hesitate to contact us with any questions or concerns you may have. LIMITATIONS Our discussions and opinions expressed verbally and in the summary information above does not express nor imply any warranty or guarantee of the existing conditions and is limited to the directed areas of focus and structural elements that were observable at the time of these efforts. There is no claim, neither stated nor implied, that all faulty conditions were or could be determined based on the limited scope of our efforts. We are available to continue investigations that will provide more detail on the conditions and measures necessary to address any damage or deficiencies. Morrison-Maierle, Inc. Jay Fischer, PE Rebecca Scheetz, PE Austin Batson, EI Page 10 of 10 Attachments: Appendix A: Lindley Center Summary Table and Cost Estimate Appendix B: Lindley Center Photos (7 pages) Appendix C: Lindley Center Structural Report by Stahly Engineering & Associates, Inc.