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HomeMy WebLinkAboutFS 2007-11-05 Item 2C - Report - Seismic Hazards Screening Report Th70Rl-vIATION MElVIO To: From: Date: Subject: Mayor Mullet Public Works Directo~ October 29,2007 Seismic Hazards Screening Report ISSUE Review results of Seismic Hazards Screening Report BACKGROUND Reid Middleton was contracted to provide Seismic Hazard Screening and Reporting services, using FEMA 154 (see section 1.2, page 1-1) and ASCE 31-03 (see section 2.0, page 2.1) screening criteria for nine City buildings (Minkler Shops was separated into three separate structures, see Table 1-1). This initial screening and evaluation only looks at rough structural details and does not include detailed structural analysis and seismic retrofit design and cost estimating. A1~AL YSIS The screening and evaluation results from the FEMA 154 criteria shown in Table 1-1, are based on a Maximum Considered Earthquake (MCE), which has a 2 percent probability of exceedance in 50 years. The Table 1-1 structural scores are based on the probability of collapse for the MCE. The lower the score, the higher the probability of collapse. The scores range from 3.1 for City Hall down to 1.1 for the Community Center. The ASCE 31-03 Tier 1 evaluation results are shown in section 2 of the report. The evaluation results outline deficiencies and structural elements worth of additional evaluation and analysis. RECOMMENDATION Facilities with a structural score of 2.5 or less receive an in-depth seismic evaluation (6300 Building, Fire Stations 51, 53 and 54, and the Community Center). Fire Station 53 and City Hall will be further evaluated because of their criticality, and Fire Station 52, Minkler and George Long Shops will be evaluated for replacement or seismic upgrade. attachments: Final Phase I seismic hazard screening report (sections 1,2 and 3) P:\PUBWORKS\PROJECT$\A- BG Projects\03BG04 Seismic Screening Oty Fadlities\Info Memo Seismic Screening Report.doc 1.0 Rapid Visual Screening 1.1 Overview Reid Middleton, Inc. performed rapid visual screenings on 11 buildings that the City of Tukwila identified as critical to their operations. Rapid visual screening of buildings for potential seismic hazards is often the first step of a multi-phase procedure for identifying seismically hazardous buildings. The Rapid Visual Screening Procedure (RVSP) uses a methodology based on a "sidewalk survey" of a building with a data collection form, which the inspector completes based on visual observation of the building. Structural scores are assigned to each building. The scores are tabulated to create a property inventory and ranking of buildings based on their relative seismic hazard potential. The rapid visual screening evaluations are then used to determine which facilities should be considered for further investigation. The RVSP is the first step in the development of a seismic risk reduction program for buildings owned and occupied by the City of Tukwila. 1.2 Criteria This work was performed in accordance with Rapid Visual Screening of Buildings for Potential Seismic Hazards (FEMA 154 and 155) published in 1988 and revised in 2002 by the Federal Emergency Management Agency (FEMA). This procedure is based on the Applied Technology Council's ATC-2l project and is a nationally recognized and widely accepted methodology to perform an initial seismic screening of buildings. The seismic hazard criteria in the second edition of FEMA 154 are based on achieving the Collapse-Prevention Performance Objective for ground motions from what is commonly referred to as a Maximum Considered Earthquake (NICE). An MCE has a 2 percent probability of exceedance in 50 years, corresponding to a return interval of 2,475 years. A building performing at a collapse-prevention level in an MCE would be expected to be severely and irreparably damaged but should not totally collapse. 1.3 Evaluation Procedure Overview The FEMA 154 process is a preliminary seismic screening procedure based on visual observations used to identify potentially hazardous buildings. Data collection forms, included in the Appendices, assign structural scores to each building. Structural scores are based on building type classifications and performance modification factors that qualitatively indicate the expected seismic performance of the buildings. The structural scores are used to rank the buildings to determine which buildings will likely provide an acceptable measure of life-safety protection and which buildings may be seismically hazardous and may warrant further investigation. The expected seismic risk that is determined by the RVSP is based on historical performance of buildings with similar characteristics. The results should be considered preliminary and used only as a guide to determine which buildings warrant further investigation. In some cases, such an investigation may reveal elements of a structure that compensate for the deficits identified in City of Tukwila Seismic Screening & Evaluation 1-1 .;~~~~: the RVSP. Furthermore, since the RVSP is typically accomplished without exposing structural elements and in some cases without entering the building, some indicators of high seismic risk may not be apparent to the screener. As a result, some buildings may be more at risk than indicated by the RVSP. 1.4 Evaluation Results The following table ~ummarizes the rapid visual screening structural scores and resulting relative seismic safety rankings for the 11 City of Tukwila buildings evaluated. Higher structural scores indicate better expected seismic performance. Table 1-1. City of Tukwila RVSP Scores and Relative Rankings. Relative Structural Rank Building Description Scores, S 1 Tukwila Community Center 1.1 2 6300 Building 1.2 3 Fire Station 51 1.5 4 Minkler Shop Office and 1.5 Repair Garage 5 Minkler Shop Work Room 1.5 and Storage Bins 6 Minkler Shop Covered 1.5 Parking 7 Fire Station 52 2.0 8 George Long Shop 2.1 9 Fire Station 54 2.2 10 Fire Station 53 2.9 11 Tukwila City Hall 3.1 FEMA 154 uses the structural scores to predict the probability of building collapse for the MCE; the score is applied as an exponent to the number 10. for example, a building with a score of 2 would have a 1 in 100 chance of collapse, while a building with a score of 3 would have a 1 in 1,000 chance of collapse. Thus, the building with a RVSP score of 1 would be more hazardous than a building with a score of 2. Note that the rapid visual screening scores (and, therefore, the rankings) given do not explicitly account for a building's use or importance. For example, a fire station that is staffed 24 hours a day with a R VSP score of 2.0 may pose greater risk than a lower occupancy structure, such as covered parking, with a RVSP score of 1.5. Comparisons between the MCE and recent earthquakes experienced in this area may be made based on information provided in the Reconnaissance Report of the February 28,2001 Nisqually Earthquakel. This report estimates that the ground motions from the 2001 Nisqually Earthquake would be only one I Reconnaissance Report (SSRP-2001/02) of the February 28, 2001 Nisqually (Seattle-Olympia) Earthquake prepared by University of California, San Diego; Andre Filiatrault; Chia-Ming Uang, Bryan Folz, Constantin Chrstopoulos, Kip Gatto; March 200 I City of Tukwila Seismic Screening & Evaluation 1-2 .mber 2007 .. I lf1t1ir.If;HiJil third as strong as the ground motions felt from the MCE for a site adjacent to the City of Tukwila. This indicates that many buildings that performed well during the Nisqually Emthquake may not perform well during a design-level event. 1.5 Conclusions and Recommendations Table 1-1 shows the R VSP seismic hazard structural scores for the 11 City of Tukwila buildings that have been evaluated. For typical buildings, FEMA 154 recommends a cut-off score of 2.0 be utilized as the RVSP score where buildings that score below this value be investigated more thoroughly. However, the FEMA guidelines also suggest that higher cut off scores may be more appropriate for determining if further seismic evaluations are warranted for essential facilities and critical infrastructure. We recommend that a RVSP structural score of 2.5 be used as the cut off for this evaluation. Buildings with a structural score of 2.5 or less should be analyzed in greater detail, since they may be vulnerable to collapse as a result of an earthquake having severe ground motions. In addition, because Tukwila City Hall and Fire Station 53 are essential facilities that provide first response capabilities for the City's police and fire personnel, more detailed seismic evaluation of these facilities is recommended. City of Tukwila Seismic Screening & Evaluation 1.3 sQmber 2007 .. I l'ltnnU:HiTil 2.0 ASCE 31-03 Tier I Evaluations Preliminary seismic evaluations were performed for 11 buildings owned by the City of Tukwila. The evaluations reviewed the expected seismic performance of each building to identify potential structural deficiencies that may affect the building's functionality after an earthquake. The following 11 buildings were evaluated in more detail compared to the RVSP described in the previous section: . Tukwila City Hall . 6300 Building . Fire Stations 51, 52, 53, and 54 . Minkler Shops (3 Total Buildings) . George Long Shop . Tukwila Community Center The preliminary seismic evaluations do not consider compliance of the subject buildings with the seismic requirements of the current building code for new construction. Buildings designed prior to the current or previous building codes often include structural configurations and detailing that . do not comply with current code requirements. Buildings designed to older building code standards are typically evaluated using evaluation and design guidelines specifically developed for existing structures by the Federal Emergency Management Agency (FEMA) and the American Society of Civil Engineers (ASCE). The latest edition of the building code includes these documents as reference standards for the evaluation of existing buildings. Findings and recommendations presented herein are primarily based on a review of record drawings provided by the City of Tukwila and on visual observations of the buildings. The available record documents do not contain some information that is needed to confirm the structural configuration of some portions of the buildings. This is typical of record documentation for older buildings. Reid Middleton participated in a walk-through of each of the buildings noted above. Limited visual observations of existing conditions were performed during the walk-through. No testing or field verification efforts were performed to confirm or supplement information shown in the record drawings. Future, detailed evaluations should include material testing and additional field verification as appropriate to better understand the existing structural condition and configuration of each building. The current standard for the seismic evaluation of existing buildings is the ASCE Standard 31-03, Seismic Evaluation of Existing Buildings (ASCE 31). ASCE 31 is a screening and evaluation document used to identify potential seismic deficiencies that may require additional seismic evaluation or hazard mitigation. The document presents a three-tiered review process implemented by following a series of comprehensive checklists and "quick check" calculations. Each tier is designed to perform an increasingly refined evaluation procedure for seismic deficiencies identified in previous tiers in the process. City of Tukwila Seismic Screening & Evaluations 2-1 .~~~~~: TIER I Screening Phase Checklists of evaluation statements to quickly identify potential deficiencies Requires field investigation and /or review of record drawings Analysis limited to "Quick Checks" of global elements May proceed to Tier 2, Tier 3, or rehabilitation design if defidencies are identified TIER 27- Evaluation_ Phase "Full Building" or "Deficiency Only" evaluation Address all Tier 1 seismic deficiencies Analysis more refined than Tier 1, but limited to simplified linear procedures Identify buildings not requiring rehabilitation TIER 3'= aatailed Evaluation Phase, Component -based evaluation of entire building using reduced FEMA 356 forces Advanced analytical procedures available if Tier 1 and /or Tier 2 evaluations are judged to be overly conservative Complex analysis procedures may result in construction savings equal to many times their cost AND /OR Interest in Redudng Seismic Risk Data Collection T Pha Phase YES TIER 2 Evaluation Phase NO s AND /OR Figure 2 -1 Flow Chart and Description of ASCE 31 Seismic Evaluation Procedure. Tier 1 checklists screen for potential seismic deficiencies by examining the lateral systems and details of the structure in comparison with configurations that have historically caused poor seismic performance in similar buildings. Tier 1 includes basic analyses for primary components of the lateral system such as columns, frames, and beams. Tier 2 provides more detailed evaluations for deficiencies identified in the Tier 1 review. Tier 3 involves more detailed analysis and review of the demand and capacity of each building component. This report contains the findings from ASCE 31 -03 Tier 1 evaluations of the 11 City of Tukwila buildings identified above. Because many of these buildings provide first- response capabilities and important post disaster recovery functions for the City of Tukwila, they were evaluated to Immediate Occupancy Performance levels. Buildings that meet Immediate Occupancy Performance are expected to be structurally functional after an earthquake. City of Tukwila Seismic Screening Evaluations 2 -2 Se tember 2007 Reid iddletott 2.1 Tukwila City Hall 2.1.1 Building Description, Tukwila City Hall Tukwila City Hall is a 32,800-square foot building that has a distinctive saw-tooth plan shape on the south elevation of the structure. The building's vertical structural system consists of plywood floor sheathing supported by wood trusses, wood beams, wood posts, concrete columns, and concrete bearing walls supported by spread and strip foundations. The lateral force resisting system (LFRS) consists of wood diaphragms supported by wood and concrete shear walls. Tukwila City Hall Built in 1977 2 stories on east side 3 stories on west side Floor Area: 32,800 SF 2.1.2 Evaluation Results, Tukwila City Hall The primary deficiency identified in Tukwila City Hall is related to the building's limited lateral support and structural irregularity in the upper floor. The building has wood shear walls that are perpendicular to the building's south facing windows at many locations. These walls are not continuous to the building's foundation and are not typically in line with the lateral framing elements below. There also appears to be in sufficient amounts lateral framing in the upper floor's east-west direction. Because of these load path discontinuities, the building appears to have limited ability to transfer latera1loads to the base of the structure form its upper floors. This likely will result in poor performance during a seismic event. Additional deficiencies are identified in the completed ASCE 31-03 Tier 1 Checklist in Appendix B. This building does not currently meet the Immediate Occupancy Performance Objective. 2.1.3 Recommendations, Tukwila City Hall Because of the discontinuities identified in the building's LFRS, and other deficiencies noted in the Tier 1 checklists, we recommend that a more detailed ASCE 31-03 Tier 3 evaluation of Tukwila City Hall be conducted. City of Tukwila Seismic Screening & Evaluations 2-3 .~~~~~: 2.2 6300 Building 2.2.1 Building Description, 6300 Building The 6300 Building is a three-story, 33,600-square foot building that was constructed on the side of a slope. The gravity system consists of plywood floor sheathing supported by open web steel joists, wood beams, wood posts, steel columns, and concrete bearing walls supported by shallow spread and strip concrete foundations. The LFRS for the 6300 Building consists primarily of wood diaphragms with concrete shear walls. In addition to the primary framing systems mentioned above, the building has wood shear walls, steel moment frames, concrete moment frames, and elevated precast concrete slabs in some locations. A variety of structural systems and material types, in conjunction with three partial-basement sides of the building that act as retaining walls, add to the buildings complexity. 6300 Building Built in 1978. 3 Stories Floor Ai'ea: 33,600 SF 2.2.2 Evaluation Results, 6300 Building The primary deficiency identified in the 6300 Building is the significant number of structural irregularities throughout the building. Based on the record drawings available, the upper stories have a minimal amount of lateral framing in the building's longitudinal direction. This may result in poor structural performance during a seismic event. In addition, a number of the building's concrete shear walls are tall and slender, with aspect ratios greater than 4: 1. These walls do not have adequately confined boundary zones, which may result in undesirable non- ductile performance of these walls under seismic loading. An additional concern is the diaphragm to wall connections. These connections are needed to stabilize the concrete shear walls for out-of-plane lateral forces but appear inadequate. Failure of these connections could lead to separation of the walls from the floors and partial collapse of the roof and floor structures during a seismic event. This connection deficiency also limits the diaphragm's ability to transfer lateral loads into the concrete shear walls. Additional deficiencies are identified in the complete ASCE 31-03 Tier I Checklist in Appendix B. This building does not currently meet the Immediate Occupancy Performance Objective. City of Tukwila Seismic Screening & Evaluations 2-4 .~~~: 2.2.3 Recommendations, 6300 Building Because of the discontinuities identified in the building's LFRS, and other deficiencies noted in the Tier 1 checklists, we recommend that a more detailed ASCE 31-03 Tier 3 evaluation of the 6300 Building be conducted. 2.3 Fire Station 51 2.3.1 Building Description, Fire Station 51 Fire Station 51 is a two-story; 17,700-square foot building that houses the Tukwila Fire Department's administration offices, and a battalion chief, an engine company, and a variety of reserve and special operation apparatuses. The gravity system consists of plywood floor sheathing supported by wood trusses, wood beams, steel beams, steel posts, concrete columns, and concrete bearing walls supported by spread and strip concrete foundations. The LFRS consists of wood diaphragms with wood and concrete shear walls. Fire Station 51 Built in 1973 2 Stories Floor Area: 17,700 SF 2.3.2 Evaluation Results, Fire Station 51 Several notable deficiencies were identified in Fire Station 51. The structure has limited lateral resistance of the high roof structure located above the crew quarters. The concrete shear walls located on the east side of the crew quarters are not continuous to the foundation. Because these walls are not continuous to the building's foundations, they may not provide adequate lateral resistance and could cause damage to their supporting structural elements during a seismic event. Furthermore, the diaphragm to wall connections that are needed to provide out-of-plane lateral stability for the precast concrete shear walls do not appear to have adequate capacity. Rupture of these connections could lead to separation of the floors from the walls and partial or total collapse of the roof and floor structures during an earthquake. This deficiency is primarily a concern in the areas over the apparatus bay. City of Tukwila Seismic Screening & Evaluations 2-5 .~~~~~: Additional deficiencies were noted at the wall panel to panel connections and at the foundation to wall panel connections. These deficiencies could lead to the panels acting independently, rather than acting together as a unit as is desired. This independent action can lead to excessive stress in the individual panels, causing wall failures. Another seismic issue is the slenderness of the wall piers between the apparatus bay doors. Because these piers have high aspect ratios, special reinforcing detailing is required to resist seismic forces. This detailing was not incorporated into the original design due to the age of construction; additional more in depth evaluation is required to determine the seismic adequacy of these elements. Additional deficiencies are identified in the complete ASCE 31-03 Tier 1 Checklist in Appendix B. This building does not currently meet the Immediate Occupancy Performance Objective. 2.3.3 Recommendations, Fire Station 51 Because of the discontinuities in the buildings' LFRS, the identified panel connection deficiencies and the other deficiencies noted in the Tier 1 checklist, we recommend that a more detailed ASCE 31-03 Tier 3 evaluation of Fire Station 51 be conducted. 2.4 Fire Station 52 2.4.1 Building Description, Fire Station 52 Fire Station 52 is a single-story, 3350-square foot building that currently houses one engine company. The gravity system consists of plywood floor sheathing supported by wood beams and precast concrete bearing walls supported by strip concrete foundations. The LFRS for Station 52 consists of wood diaphragms with precast concrete shear walls. Fire Station 52 Built in 1971 One Story Floor Area: 3,350 SF City of Tuk\vila Seismic Screening & Evaluations 2-6 \Imber 2007 '. I ~'ltfinJrnfiTi1 2.4. Evaluation Results, Fire Station 52 Deficiencies identified in Fire Station 52 pertain to the building's LFRS connections. Of primary concern is the roof diaphragm to wall connections. These connections are needed to provide out-of-plane lateral stability for the precast concrete shear walls. Rupture of these connections could lead to separation of the roof from the walls and partial or total collapse of the roof structures during an earthquake. This connection deficiency also limits the roof s diaphragm ability to transfer lateral loads into the concrete shear walls. Additional deficiencies were noted at the panel-to-panel connections and the foundation to wall panel connections. These deficiencies could lead to the panels acting independently, rather than acting in a more desirable composite fashion. This independent action can lead to excessive stress in the individual panels causing wall failures. Another deficiency is the slenderness of the wall piers between the apparatus bay doors. Because these piers have large aspect ratios, special reinforcing detailing is required to resist seismic forces. This detailing was not incorporated into the original design due to the age of construction; additional more in depth evaluation is required to determine the seismic adequacy of these elements. Additional deficiencies are identified in the complete ASCE 31-03 Tier 1 Checklist in Appendix B. This building does not currently meet the Immediate Occupancy Performance Objective. 2.4.3 Recommendations, Fire Station 52 Because the deficiencies in Fire Station 52 are fairly well defined, we recommend that a design be developed to upgrade the building. 2.5 Fire Station 53 2.5.1 Building Description, Fire Station 53 Fire Station 53 is a single-story, 14,000-square foot building that currently houses one engine company. The gravity system consists of plywood floor sheathing supported by wood beams, wood posts, steel posts, and wood bearing walls on concrete grade beams supported by auger- cast piling. The LFRS for Station 53 consists of wood diaphragms with wood shear walls and steel moment frames in the apparatus bay. The station's hose tower is constructed of concrete masonry units (CMU). City of Tukwila Seismic Screening & Evaluations 2-7 .mber 2007 '. I \'Jmnu:~liTiI Fire Station 53 Built in 1995 One Story Floor Area: 14,000 SF 2.5.2 Evaluation Results, Fire Station 53 Fire Station 53 can be expected to have acceptable performance during an earthquake and may meet the Immediate Occupancy Performance Objective. Several deficiencies were identified during the Tier 1 screening process, however, as a result of details missing from the original design drawings. See the ASCE 31-03 Tier 1 Checklist in Appendix B for additional information. 2.5.3 Recommendations, Fire Station 53 Because the building is close to meeting the chosen performance objective, we recommend conducting an ASCE 31-03 Tier 2 evaluation of the building. Field investigation may be required as part of the Tier 2 evaluation in order to obtain additional information about the location for which the details were missing from the original drawings. 2.6 Fire Station 54 2.6.1 Building Description, Fire Station 54 Fire Station 54 is a single-story, 5,300-square foot building that currently houses one ladder company. The gravity system consists of plywood floor sheathing supported by wood beams, wood posts, wood bearing walls and masonry bearing walls supported by strip concrete foundations. The LFRS for Station 54 consists of wood diaphragms with masonry shear walls. The station's hose tower is constructed of concrete masonry units (CMU). City of Tukwila Seismic Screening & Evaluations 2.8 .mber 2007 .. I ~',mnlrnrnil Fire Station 54 Built in 1961 One Story Floor Area: 5,300 SF 2.6.2 Evaluation Results, Fire Station 54 Deficiencies identified at Fire Station 54 pertain to the masonry walls and the walls' connections to the roof diaphragm. Because limited information is available in the record drawings pertaining to either of these items, they are assumed to be non-compliant based on the age of the building. Significantly less reinforcing was typically used in CMU walls of Station 54's era than would be required today. Inadequate wall reinforcing can result in non-ductile behavior and wall failure. The walls also are over stressed based on the quick check procedure meaning that they may experience shear failures during an earthquake. Inadequate diaphragm to wall connections were also typical of Station 54's era, and may result in out-of-plane wall failures. Inadequate connections also limit the ability of the diaphragm to transfer forces into the shear walls. Additional deficiencies are identified in the complete ASCE 31-03 Tier 1 Checklist in Appendix B. . This building does not currently meet the Immediate Occupancy Performance Objective. 2.6.3 Recommendations, Fire Station 54 Because of the lack of information available on Fire Station 54 and the deficiencies identified in the Tier 1 check list, we recommend that a more detailed ASCE 31-03 Tier 3 evaluation be conducted. 2.7 Minkler Shops Work Room And Storage Bins 2.7.1 Building Description, Minkler Shops Work Room and Storage Bins The Minkler Shops Work Room and Storage Bin Building is a 4,700-square foot, single-story building. The gravity system consists of precast concrete roof planks and diagonal wood roof decking supported by precast concrete bearing walls supported by strip concrete foundations. City of Tukwila Seismic Screening & Evaluations 2.9 ~ber 2007 ". I l',rtililrnmil The LFRS for the building consists of wood and concrete diaphragms with precast concrete shear walls. :Minkler Shops Work Room and Storage Bins Built in 1972 One Story Floor Area: 4,700 SF 2.7.2 Evaluation Results, Minkler Shops Work Room and Storage Bins Deficiencies identified in the Minkler Shops Work Room and Storage Bins pertain to the building's LFRS connections. Of primary concern is the roof diaphragm to wall connections. These connections are needed to provide out-of-plane lateral stability for the precast concrete shear walls. Rupture of these connections could lead to separation of the roof from the walls and partial or total collapse of the structures during a seismic event. This connection deficiency also limits the roof diaphragm's ability to transfer lateral loads into the concrete shear walls. Additional deficiencies were noted at the panel-to-panel connections and at the foundation to wall panel connections. These deficiencies could lead to the panels acting independently, rather than acting in a more desirable composite fashion. This independent action can lead to excessive stress in the individual panels, causing wall failures. Additional deficiencies are identified in the complete ASCE 31-03 Tier 1 Checklist in Appendix B. This building does not currently meet the Immediate Occupancy Performance Objective. 2.7.3 Recommendations, Minkler Shops Work Room and Storage Bins Because the deficiencies in the Minkler Shops Work Room and Storage Bins are fairly well defined, we recommend that a design be developed to upgrade the building. 2.8 Minkler Shops Covered Parking 2.8.1 Building Description, Minkler Shops Covered Parking The Minkler Shops Covered Parking is an 8,850-square foot roof structure that is used to store public works equipment. The gravity system consists of precast concrete roof planks supported by concrete beams, steel posts, and precast concrete bearing walls supported by strip concrete foundations. The LFRS for the building consists of wood and concrete diaphragms with precast concrete shear walls. City of Tukwila Seismic Screening & Evaluations 2-10 s.mber 2007 '. I \'ltfifilrnroil Minkler Shops Covered Parking Built in 1972 One Story Floor Area: 8,850 SF 2.8.2 Evaluation Results, Minkler Shops Covered Parking Deficiencies identified in the Minkler Shops Covered Parking pertain to the building's LFRS connections. Of primary concern are the roof diaphragm to wall connections. These connections are needed to provide out-of-plane lateral stability for the precast concrete shear walls. The available record drawings do not show a direct connection between the concrete roof planks and the concrete wall panels; connections between these elements were also not observed during our building walk-through. The lack of roof diaphragm to wall connections could lead to separation of the roof from the walls and partial or total collapse of the structures during an earthquake. This connection deficiency also limits the roof diaphragm's ability to transfer lateral loads into the concrete shear walls. Additional deficiencies were noted at the panel-to-panel connection and at the foundation to wall panel connections. These deficiencies could lead to the wall panels acting independently, rather than acting in a more desirable composite fashion. This independent action can lead to excessive stress in the individual panels causing wall failures. Deterioration of the wall panel to wall panel connections, including rusting of steel connections and concrete cracking near the panel inserts, was observed during our building walk-through. Additional deficiencies are identified in the complete ASCE 31-03 Tier 1 Checklist in Appendix B. This structure does not currently meet the Immediate Occupancy Performance Objective. 2.8.3 Recommendations, Minkler Shops Covered Parking Because the deficiencies in the Minkler Shops Covered Parking are fairly well defined, we recommend that a design be developed to retrofit the structure. City of Tukwila Seismic Screening & Evaluations 2-11 s.mber 2007 .. I \'~ "Hi HiH;fil 2.9 Minkler Shops Office And Garage 2.9.1 Building Description, Minkler Shops Office and Garage The Minkler Shops Office and Garage is a 7,200-square foot single-story building that houses offices and equipment. The gravity system consists of diagonal wood roof decking supported by wood beams and precast concrete bearing walls supported by strip concrete foundations. The LFRS for the building consists of wood diaphragms with precast concrete shear walls. Minkler Shops Office and Garage Built in 1972 One Story Floor Area: 7,200 SF 2.9.2 Evaluation Results, Minkler Shops Office and Garage Deficiencies identified in the Minkler Shops Office and Garage pertain to the building's LFRS connections. Of primary concern is the roof diaphragm to wall connections. These connections are needed to provide out-of-plane lateral stability for the precast concrete shear walls. Rupture of these connections could lead to separation of the roof from the walls and partial or total collapse of the structures during a seismic event. Additional deficiencies were noted at the panel- to-panel connections and at the foundation to wall panel connections. These deficiencies could lead to the panels acting independently, rather than acting in a more desirable composite fashion. This independent action can lead to excessive stress in the individual panels causing wall failures. Deterioration of the wall panel to wall panel connections, including rusting of steel connections and concrete cracking near the panel inserts, was observed during our building walk- through. Additional deficiencies are identified in the complete ASCE 31-03 Tier 1 Checklist in Appendix B. This building does not currently meet the Immediate Occupancy Performance Objective. 2.9.3 Recommendations, Minkler Shops Office and Garage Because the deficiencies in the Minkler Shops Office and Garage are fairly well defined, we recommend that a design be developed to retrofit the building. City of Tukwila Seismic Screening & Evaluations 2-12 s.mber 2007 .. I MrH'lI r:l!iTil 2.10 George Long Shops 2.10.1 Building Description, George Long Shops The George Long Shop is a 32,200-square foot, two-story, pre-manufactured metal building that houses offices and vehicle maintenance operations. The gravity system consists of steel decking supported by steel beams and steel columns supported on spread foundations. The LFRS for the building consists of steel deck diaphragms with steel moment frames. George Long Shops Year Built: Unknown Two Stories Floor Area: 32,200 SF 2.10.2 Evaluation Results, George Long Shops Limited record drawings are available for the George Long Shop. No original construction drawings are available; partial information was provided by drawings created for subsequent remodeling and alterations. Based on the information that is available and observations from our building walk-though, the building is a pre-manufactured metal building. Typically, these buildings resist lateral loads with steel moment frames in one direction with steel tension bracing in the other. During the building walk-through no steel bracing was observed. The apparent lack of steel bracing is the primary concern for this building. It is possible that the exterior walls may act as metal panel shear walls in that direction, reducing the need for bracing. However, the amount of wall is very limited on the side of the building with the large vehicle access doors and bracing may still be required. Additional deficiencies are identified in the complete ASCE 31-03 Tier 1 Checklist in Appendix B. This building does not currently meet the Immediate Occupancy Performance Objective. 2.10.3 Recommendations, George Long Shops Because the George Long Shop Building is a pre-manufactured metal building, we do not believe that it is economically feasible to retrofit the building to meet an Immediate Occupancy Performance Objective. As a result, additional evaluation based on a reduced performance objective may be warranted. City of Tukwila Seismic Screening & Evaluations 2-13 .mber 2007 ". I l'JtrWlrnrnil 2.11 Tukwila Community Center 2.11.1 Building Description, Tukwila Community Center The Tukwila Community Center is a one-story; 55,000-square foot building. The areas outside of the gymnasium and entry hall have a vertical structural system consisting of plywood roof sheathing supported by wood beams, wood posts, steel posts and wood bearing walls supported by spread and strip foundations. The LFRS consists of wood diaphragms with wood shear walls. The gymnasium portion of the building is constructed of steel roof decking supported by steel trusses and masonry bearing walls. The LFRS for this area consists of steel deck diaphragms with masonry shear walls. Tukwila Community Center Built in 1995 One Story Floor Area: 55,000 SF 2.11.2 Evaluation Results, Tukwila Community Center Deficiencies identified for the areas outside of the gymnasium and entry hall pertain to the building's wood shear walls. Some of the walls are potentially overstressed and lack adequate hold-down anchorage. Hold-down anchorages are intended to prevent the walls from overturning under seismic loads. These deficiencies may result in poor performance during a seismic event. Deficiency identified in the gymnasium portion of the building is that the masonry shear walls are over stressed for seismic shear loads. This may result in degradation and potential failure of the wall during a seismic event. Additionally, the roof diaphragm to masonry wall connections were found to be inadequate. These connections are needed to provide out-of-plain lateral stability for the masonry shear walls. rupture of these connections could lead to separation of the roof from the walls and partial or total collapse of the structures during a seismic event. Additional deficiencies are identified in the complete ASCE 31-03 Tier I Checklist in Appendix B. This building does not currently meet the Immediate Occupancy Performance Objective. City of Tukwila Seismic Screening & Evaluations 2.14 limber 2007 .. I ,'J t1HiI r!HiTil ~ 2.11.3 Recommendations, Tukwila Community Center Because of the excessive stresses identified in the wood and masonry shear wall elements system and the other deficiencies noted in the Tier 1 checklist, we recommend that a more detailed ASCE 31-03 Tier 3 evaluation of the Tukwila Community Center be conducted. City of Tukwila Seismic Screening & Evaluations 2-15 s.;mber 2007 .. I ~'It1iIiIl!UiTiI 3.0 Conclusions ASCE 31-03 Tier 1 structural evaluations were performed for 11 buildings owned by the City of Tukwila. A walk-through of the structures was performed in conjunction with these evaluations. Based on deficiencies noted in our Tier 1 evaluations and based on the complexity of the building structures, we recommend that additional, detailed investigations and analyses be performed for the followings structures: e Tukwila City Hall . 6300 Building . Fire Stations 51, 53, and 54 . George Long Shop . Tukwila Community Center Additional analyses and investigations of these structures may lead to recommendations for upgrades. Based on deficiencies noted and the straight-forward nature of the potential upgrades, we recommend upgrades be performed for the following structures: . Fire Stations 52 . Minkler Shops (3 Total Buildings) Most of the recommended improvements to these structures consist of added or improved connections between walls and the roofs and floors of these structures. City of Tukwila Seismic Screenings & Evaluations 3-1 .mber 2007 ". I ~TltfHiIrHliTiI