Introduction
The City of Glendora (City) has requested that JMD and Cho Design Associates, Inc. (CDA), review and provide a preliminary assessment of the structural elements of the City's Public Library roof slab and framing system that forms the base of the Bidwell Plaza. It is our understanding that the City desires to add a permanent shade structure to the existing Bidwell Plaza that is on top of the roof of the Glendora Public Library. During the initial investigation to add a shade structure to the existing roof, it was noted that there were some cracks in the existing concrete roof system and some water intrusion into the library. A preliminary assessment of the concrete roof system was requested by the City. This assessment includes the plaza deck and library roof system.
Purpose and Scope
The goal of the project is to provide the City with a preliminary structural engineering assessment/investigation of the City's existing Public Library roof slab and framing system that forms the base of the Bidwell Plaza in terms of its utility and possible hazards. CDA conducted a site visit to assess the overall structural condition of the library's roof framing system and slab. A summary of our findings and recommendations is included in this Preliminary Condition Assessment Report.
Description
Based on as-built plans provided by the City, the existing library facility and Bidwell Plaza was completed in 1972. The library is a two-story reinforced concrete and concrete masonry (CMU) structure located next to the City of Glendora City Hall at the southeast corner of Glendora Boulevard and W. Foothill Avenue.
Data Collection and Review
The following documents and information have been received from the City and reviewed in association with this project:
• As-built plans for Glendora Public Library, prepared by Anthony & Langford Architects, dated September 5, 1970, consisting of 30 sheets.
• As-built plans for Glendora Public Library – Voluntary Upgrade, dated June 2003 prepared by Jeff Coronado, S.E.
• As-built plans for Glendora Public Library – Plaza Demo and Resurfacing, undated, prepared by Jeff Coronado, S.E.
No other plans or reports are available for our review.
Review of As-Built Plans and Reports
Cho Design Associates conducted a review of the as-built plans provided by City. According to the as-built plans for the facility, the main floor and structure was designed utilizing concrete with a required minimum compressive strength of 3,000 psi at 28 days and Grade 40 reinforcing steel. The building envelope consists of cast-in-place concrete and CMU walls with a wood roof framing system.
No structural calculations or geotechnical reports were available for our review as a part of this project.
In 2003 and 2004 the library went through extensive structural modifications to reinforce the structure and its foundation to bring the building into compliance with the current codes and standards at the Item #17. Page 63
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Preliminary Condition Assessment
time. The 2003 project reinforced the north wall and the supporting columns. The 2004 project addressed the plaza’s deteriorating concrete surface and water infiltration by replacing its water-proof membrane and adding a lightweight concrete topping on the existing deck. It appears that the 2004 project may have also repaired some roof slab cracks with epoxy injection. We did not find any plans or specifications to document that this was to be done as a part of the project, only what we observed in some project construction photos provided by the City.
Based on information from the City, the concrete deterioration at the library has been an ongoing for some time and generally consist of cracks in the concrete beams and roof slab surfaces. There appears to be some water infiltration into the main library after rain events, located primarily in the north-east section of the library ceiling. This study only includes a representative visual assessment of the surface defects, a review of the as-built plans and evaluation of the City's historical observations.
Preliminary Condition Assessment
A visual condition assessment of the surface defects was conducted at the library on March 29, 2022 and was limited to a representative sampling of the beams and slabs above the drop ceiling.
Our preliminary investigation consisted of physically accessing each area by removing the drop ceiling panels and visually inspecting the surfaces for deterioration. Most of the concrete deterioration consisted of minimally to moderately cracked concrete surfaces. We did not observe anything that would indicate an immediate underlying structural problem in the areas with the deteriorated concrete surface areas. We also employed the use of a rotary percussion hammer to check for areas of delamination or other structural defects that were not noticeably visible. Generally, the underlying surface of the concrete was found to be sound, with no visual evidence of delamination or spalling.
The main area of obvious deterioration are the numerous superficial cracks throughout the roof beams and roof slabs of the library (Figures 1 and 2). The majority of these are not thought to be a serious issue since they were small and there was no evidence of major seepage, leakage or corrosions stains that were noted on the concrete. There are however several locations where the epoxy repaired cracks are exhibiting some sort of leakage and staining (Figures 5 and 6). There also appears to be some new cracks that may have occurred after the 2004 repairs. Some of these new cracks in the slab are showing signs of water infiltration and staining, but there was no indication of corrosion of the beam or slab reinforcing from the water infiltration (Figures 7, 8, 9 and 10). These cracks are thought to be new because they are large enough so they should have been repaired during the epoxy injection process of the other cracks, or they were smaller back then and have developed into larger cracks since the 2004 project.
There are also several areas where there are large cracks in the main girders. These cracks exceed
0.06" (1.5mm) in width which is the accepted threshold for a reasonable crack width of 0.016” (0.41mm) (Figures 3 and 4). No other significant structural issues were noted during our representative assessment of the library beams and slab system.
The following are some representative photos of the typical cracks and other defects that were found during our preliminary visual assessment. A complete set of photos taken during our visual assessment is included in Appendix "A" of this report.
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Preliminary Condition Assessment
Figure 1 - Typical Cracking in Slab (minor)
Figure 2 – Typical Concrete Cracks at Beam and Slab (minor) Item #17. Page 65
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Figure 3 – Large Girder Crack, > 0.016"
Figure 4 - Close-up of Girder Crack, > 0.016"
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Figure 5 – Epoxy Injection Repaired Area
Figure 6 – Leakage at Epoxy Repair
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Figure 7 – Leakage at Slab Crack (unrepaired)
Figure 8 – Leakage and Staining at Beam (unrepaired)
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Figure 9 – Crack at Waffle Slab (Main Reading Area)
Figure 10 – Close-up of Waffle Slab Crack (Main Reading Area) Item #17. Page 69
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Preliminary Condition Assessment
Conclusions
In summary, the concrete beams, roof slab and overall structural systems of the library and plaza base are generally in sound structural condition, but there are some issues that needs to be addressed to maintain the structural integrity of the facility. Based on our initial visual inspection and evaluation, the library roof and slab and plaza base needs to have the crack issues addressed. These repairs should not require the library to be shut down.
The American Concrete Institute (ACI) publishes document ACI 224R-01 "Control of Cracking in Concrete Structures". Table 4.1 from that document provides a general guideline for reasonable crack widths for reinforced concrete elements under service loads. Acceptable crack widths range from
0.004 in. (0.1 mm) to 0.016 in. (0.41 mm), with smaller widths for concrete in wet or aggressive environments and larger crack widths for drier exposures. For the City's library, the 0.016" (0.41 mm) is considered an acceptable crack width.
There are numerous cases where the crack width exceeds the reasonable limit of 0.016" as presented in the table above and needs to be addressed. Many of the cracks are less than that and do not pose any real issues.
The condition of the unexposed reinforcing steel could not be assessed, because the level of inspection for this project did not include destructive testing, no conclusion was drawn for the condition of the unexposed reinforcing steel.
No visual evidence of carbonation or alkali-silica reactivity or other issues were apparent. Laboratory testing for these issues is beyond the scope for this project.
A plot showing the approximate locations of the representative photos and cracks is included in Appendix "A" along with a complete photo log.
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Recommendations
We recommend that City initiate a full extensive survey of the roof and slab of the library to fully document the repair needs for this facility as soon as possible to minimize any further damage.
At this time, the following items are recommended:
• Comprehensive Field Survey: Perform a comprehensive field survey, assessment and evaluation of the entire library roof slab and beam system. This survey should fully document the size and location of all cracks. Any additional defects such as spalling, delamination or pop-outs should also be noted.
• Final Repair Plans: Prepare comprehensive plans, details and specifications for the repair and rehabilitation of all defects noted in the Comprehensive Field Survey above.
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Page A-1
Appendix A
Photo Location Record
and
Photo Log
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Page A-3
Photo Log
Photo # Description
1 Slab cracks, < 0.03"
2 Slab cracks, < 0.03"
3 Slab cracks, < 0.03"
4 Slab cracks, < 0.03"
5 Slab cracks, < 0.03"
6 Slab cracks, ~0.025"
7 Slab cracks, ~0.025"
8 Slab cracks, ~0.025"
9 Beam cracks, >0.06"
10 Beam cracks, >0.06"
11 Beam cracks, >0.06"
12 Minor beam crack approximately 12" from end, typical at numerous beams 13 Beam and slab cracks, ~0.02"
14 Beam and slab cracks, ~0.02"
15 Repaired beam
16 Beam cracks, >0.03"
17 Beam cracks, >0.06"
18 Beam cracks, >0.06"
19 Beam and slab cracks, ~0.02"
20 Slab cracks, ~0.02"
21 Beam cracks, ~0.02"
22 Epoxy injection repaired area with water stains
23 Epoxy injection repaired area with water stains
24 Epoxy injection repaired area with water stains
25 Beam and slab crack
26 Epoxy injection repaired area
27 Epoxy injection repaired area
28 Area with new cracks and active water infiltration
29 Area with new cracks and active water infiltration
30 Area with new cracks and active water infiltration
31 Area with new cracks and active water infiltration
32 Slab cracks, ~0.02"
33 Beam crack, ~0.04"
34 Beam crack, ~0.04"
35 Beam crack, ~0.02"
36 Beam crack. ~0.05"
37 Beam crack @ waffle slab, >0.05" (typical)
38 Beam crack @ waffle slab, >0.05" (typical)
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Page A-4
Photos
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Page B-1
Appendix B
As-Built Plans
• As-built plans for Glendora Public Library, prepared by Anthony & Langford Architects, dated September 5, 1970, consisting of 30 sheets.
• As-built plans for Glendora Public Library – Voluntary Upgrade, dated June 2003 prepared by Jeff Coronado, S.E.
• As-built plans for Glendora Public Library – Plaza Demo and Resurfacing, undated, prepared by Jeff Coronado, S.E.
Item #17. Page 76
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AWARD A CONTRACT AGREEMENT TO MYERS
HOUGHTON & PARTNERS, INC. FOR IN-DEPTH
LIBRARY STRUCTURAL ANALYSIS & LONGTERM FUTURE ASSESSMENT Public Works, Engineering
City Council
Item #
January 10, 2023
Michael Sledd, Assistant Public Works Director CityOfGlendora.org Item #17. Page 77
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2 Background
• Built in 1972
• Bidwell Plaza serves as majority of
lower/main floor’s roof
• Historic and ongoing water infiltration
issues on main library floor
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3 2004 Renovations Item #17. Page 79
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4 2004 Renovations Item #17. Page 80
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5 2004 Renovations Item #17. Page 81
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6 2004 Renovations Item #17. Page 82
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7 2004 Renovations Item #17. Page 83
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8 2004 Renovations Item #17. Page 84
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9 2004 Renovations Item #17. Page 85
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10 2004 Renovations Item #17. Page 86
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11 Preliminary Assessment Item #17. Page 87
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12 Preliminary Assessment Item #17. Page 88
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13 Request For Proposals (RFP)
• September 22, 2022, released on QuestCDN
• October 5, 2022, pre-submittal job walk conducted w/12 different consultant firms • October 20, 2022, proposal due date
• 5 proposals were submitted
• Based on proposal evaluation and interviews by Library and Public Works staff, Myers Houghton & Partners, Inc (MHP) was recommended as best meeting City’s needs.
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14 Proposal Cost Summary & Draft Workplan Item #17. Page 90 Meeting Date: 1/10/2023 / Packet Page #: 879
15 FISCAL IMPACTS
Item (All amounts from Fund 321 – Capital Projects Fund) Item Amount Preliminary condition assessment total costs (completed) ($41,115.71) MHP Proposal Amount ($215,941.00)
MHP Agreement Contingency (10%) ($21,594.10)
Total Costs ($278,650.81)
FY2021/23 Adopted Two-Year Budget Project Funding $190,000.00 Appropriation Needed $88,650.81
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16 RECOMMENDATIONS
1. Award an agreement with Myers Houghton & Partners, Inc. for the Library Structural Analysis and Options for Vertical Expansion project in the amount of $215,941.00;
2. Authorize the City Manager or his designee to execute the agreement with Myers Houghton & Partners, Inc., including minimal and/or non-substantive changes;
3. Authorize the Public Works Director to execute any necessary change orders in an amount not to exceed 10% ($21,594.10) of the original contract amount, for a potential total agreement amount of $237,535.10; and
4. Authorize the Administrative Services Director to appropriate $88,650.81 using Capital Projects Fund 321 towards project budget.
That the City Council:
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