FORM 1 CERTIFICATE OF SEISMIC PERFORMANCE LEVEL UC ......Campus: UC Berkeley Building Name: Boalt...

Campus: UC Berkeley

Building Name: Boalt Hall

CAAN ID: 1231

Auxiliary Building ID: N/A Date: 7/11/2019

This Form 1 (March 26, 2019) is to be used in connection with Guidebook, Version 1.3, Section III.A.3.c-g

FORM 1

CERTIFICATE OF SEISMIC PERFORMANCE LEVEL

☒ UC-Designed & Constructed Facility

☐ Campus-Acquired or Leased Facility

BUILDING DATA


Address: Core Campus, Berkeley, CA 94720

Site location coordinates: Latitude 37.869722 o Longitudinal -122.253333 o

UCOP SEISMIC PERFORMANCE LEVEL (OR “RATING”): IV

ASCE 41-17 Model Building Type:

a. Longitudinal Direction: C2: Concrete Shear Walls (with Stiff Diaphragms)

b. Transverse Direction: C2: Concrete Shear Walls (with Stiff Diaphragms)

Gross Square Footage: 125,572 sq. ft. out of 281,721 sq. ft. Number of stories above grade: 6

Number of basement stories below grade: 0

Year Original Building was Constructed: 1950

Original Building Design Code & Year: 1946 UBC (Assumed)

Retrofit Building Design Code & Year (if applicable): N/A

SITE INFORMATION

Site Class: C Basis: Site Specific Zone Map of campus by Geomatrix

Geologic Hazards:

Fault Rupture: No Basis: Earthquake Zones of Required Investigation- Oakland West Quadrangle

https://maps.conservation.ca.gov/cgs/informationwarehouse/regulatorymaps/

Liquefaction: No Basis: Earthquake Zones of Required Investigation- Oakland West Quadrangle


Landslide: No Basis: Earthquake Zones of Required Investigation- Oakland West Quadrangle


ATTACHMENT

Map of Boalt Complex

Seismic Evaluation: Seismic Assessment Report Boalt Hall School of Law University of California,

Rutherford & Chekene, January 16, 2009

Campus: UC Berkeley


CAAN ID: 1231



CERTIFICATION & PRESUMPTIVE RATING VERIFICATION STATEMENT

I, Bret Lizundia, a California-licensed structural engineer, am responsible for the completion of this

certificate, and I have no ownership interest in the property identified above. My scope of review to

support the completion of this certificate included both of the following (“No” responses must include an

explanation):

a) the review of structural drawings indicating that they are as-built or record drawings, or that they

otherwise are the basis for the construction of the building: � Yes ☐ No

b) visiting the building to verify the observable existing conditions are reasonably consistent with those

shown on the structural drawings: � Yes ☐ No

Based on my review, I have verified that the UCOP Seismic Performance Level (SPL) is presumptively

permitted by the following UC Seismic Program Guidebook provision (choose one of the following):

☐ 1) Contract documents indicate that the original design and construction of the aforementioned

building is in accordance with the benchmark design code year (or later) building code seismic design

provisions for UBC or IBC listed in Table 1 below.

� 2) The existing SPL rating is based on an acceptable basis of seismic evaluation completed in 2006 or

later. Note: In the 2009 report, based on a Tier 2 linear seismic evaluation using ASCE 41-06, the building

was assigned a FAIR (current Level IV) to GOOD (current Level III) rating. Accordingly, a conservative

Seismic Performance Level rating of Level IV is assigned.

☐ 3) Contract documents indicate that a comprehensive1 building seismic retrofit design was fully-

constructed with an engineered design based on the 1997 UBC/1998 or later CBC, and (choose one of the

following):

☐ the retrofit project was completed by the UC campus. Further, the design was based on ground

motion parameters, at a minimum, corresponding to BSE-1E (or BSE-R) and BSE-2E (or BSE-C) as

defined in ASCE 41, or the full design basis ground motion required in the 1997 UBC/1998 CBC or later

for EXISTING buildings, and is presumptively assigned an SPL rating of IV.

☐ the retrofit project was completed by the UC campus. Further, the design was based on ground

motion parameters, at a minimum, corresponding to BSE-1 (or BSE-1N) and BSE-2 (or BSE-2N) as

defined in ASCE 41, or the full design basis ground motion required in the 1997 UBC/1998 or later CBC

for NEW buildings, and is presumptively assigned an SPL rating of III.

☐ the retrofit project was not completed by the UC campus following UC policies, and is presumptively

assigned an SPL rating of IV.

1 A comprehensive retrofit addresses the entire building structural system as indicated by the associated seismic evaluation, as opposed to

addressing selective portions of the structural system.

Campus: UC Berkeley


CAAN ID: 1231



07-15-19

CERTIFICATION SIGNATURE

Bret Lizundia Executive Principal

AFFIX SEAL HERE

Print Name Title

S3950

12/31/2020

CA Professional Registration No. License Expiration Date

Signature Date

Rutherford + Chekene

375 Beale Street, Suite 310

San Francisco, CA 94105-2066

415-568-4400

Firm Name, Phone Number, and Address

07-15-2019

Campus: UC Berkeley


CAAN ID: 1231



Table 1: Benchmark Building Codes and Standards

UBC IBC

Wood frame, wood shear panels (Types W1 and W2) 1976 2000

Wood frame, wood shear panels (Type W1a) 1976 2000

Steel moment-resisting frame (Types S1 and S1a) 1997 2000

Steel concentrically braced frame (Types S2 and S2a) 1997 2000

Steel eccentrically braced frame (Types S2 and S2a) 1988g 2000

Buckling-restrained braced frame (Types S2 and S2a) f 2006

Metal building frames (Type S3) f 2000

Steel frame with concrete shear walls (Type S4) 1994 2000

Steel frame with URM infill (Types S5 and S5a) f 2000

Steel plate shear wall (Type S6) f 2006

Cold-formed steel light-frame construction—shear wall system (Type CFS1) 1997h 2000

Cold-formed steel light-frame construction—strap-braced wall system (Type CFS2) f 2003

Reinforced concrete moment-resisting frame (Type C1)i 1994 2000

Reinforced concrete shear walls (Types C2 and C2a) 1994 2000

Concrete frame with URM infill (Types C3 and C3a) f f

Tilt-up concrete (Types PC1 and PC1a) 1997 2000

Precast concrete frame (Types PC2 and PC2a) f 2000

Reinforced masonry (Type RM1) 1997 2000

Reinforced masonry (Type RM2) 1994 2000

Unreinforced masonry (Type URM) f f

Unreinforced masonry (Type URMa) f f

Seismic isolation or passive dissipation 1991 2000

Note: UBC = Uniform Building Code . IBC = International Building Code .a Building type refers to one of the common building types defined in Table 3-1 of ASCE 41-17.b Buildings on hillside sites shall not be considered Benchmark Buildings.c not usedd not usede not usedf No benchmark year; buildings shall be evaluated in accordance with Section III.J.

h Cold-formed steel shear walls with wood structural panels only.i Flat slab concrete moment frames shall not be considered Benchmark Buildings.

Building Seismic Design Provisions

g Steel eccentrically braced frames with links adjacent to columns shall comply with the 1994 UBC Emergency Provisions, published September/October

1994, or subsequent requirements.

Building Typea,b

Note: This table has been adapted from ASCE 41-17 Table 3-2. Benchmark Building Codes and Standards for Life Safety Structural Performed at BSE-1E.

SIMON HALL1391

N

BOALT HALL(Robbins Collection)

1231.1

BOALT SOUTHINFILL1231.3

BOALT HALL1231

BOALT HALLNORTH ADDITION

1231.2

BUILT 1967BASEMENT REMODLED1979

BUILT 2011

BUILT 1995

BUILT 19671 STORY ADDED IN 1980

BUILT 19494 STORIES FOR LIBRARYADDED IN 1960WALL OPENING IN 1984COL. FRP ADDED 2011

BOALT HALLCOMPLEX

BANCROFT WAY

PIE

DM

ON

T A

VE

NU

E

Seismic Assessment Report

Boalt Hall School of Law University of California, Berkeley

January 16, 2009

Rutherford and Chekene Consulting Engineers

55 Second Street, Suite 600 San Francisco, CA 94105

Consulting Engineers • Structural & Geotechnical 55 Second Street Suite 600 San Francisco CA 94105 • TEL 415 568 4400 FAX 415 618 0684

PRINCIPALS: David S. Bleiman; Dominic E. Campi; Helen M. Fehr; Larry C. Fournier; William T. Holmes; Afshar Jalalian; Gyimah Kasali, Ph.D.; Thomas W. Lauck; Bret Lizundia; Joseph Maffei, Ph.D.; Richard W. Niewiarowski; Peter C. Revelli; Patrick J. Ryan; C. Mark Saunders; Joseph D. Ungerer; Wayne W. Wong

January 16, 2009 Mr. Joseph Nicola Ratcliff Architects 5856 Doyle Street Emeryville, CA 94608

2006-101S Subject: BOALT HALL SCHOOL OF LAW UNIVERSITY OF CALIFORNIA, BERKELEY BERKELEY, CALIFORNIA

Dear Mr. Nicola:

In conjunction with the design of the new Infill Building, the University of California, Berkeley Seismic Review Committee requested an additional review of the existing structure. We are pleased to transmit herewith our seismic assessment report for the existing Boalt Hall School of Law at the University of California campus in Berkeley, California.

This report summarizes the results of our seismic assessment, which consisted of a site visit, engineering analyses, and structural design recommendations for the proposed project. A calculation package is included as an appendix to this report.

If there are questions regarding any aspect of this investigation, please contact us. We appreciate the opportunity to be of service to you on this project. Sincerely, RUTHERFORD & CHEKENE

Dominic Campi, S.E. Afshar Jalalian. S.E. Principal Principal Lawrence Burkett Staff Engineer DEC-AJ-LAB/hb

Boalt Hall School of Law – University of California, Berkeley January 16, 2009 Seismic Assessment Report Page i

TABLE OF CONTENTS

Letter of Transmittal Table of Contents........................................................................................................................................... i List of Figures .............................................................................................................................................. iii

PURPOSE ..........................................................................................................................................1

BUILDING DESCRIPTION..................................................................................................................1 General Description.................................................................................................................................. 1 Structural System...................................................................................................................................... 2

Gravity System ..................................................................................................................................... 2 Lateral System...................................................................................................................................... 3

EVALUATION METHODOLOGY........................................................................................................3

EVALUATION OF CONCRETE SHEAR WALLS..................................................................................4 Evaluation of Level 1 Walls ..................................................................................................................... 4

Evaluation Results ............................................................................................................................... 4 McEnerney Stacks Walls.......................................................................................................................... 4

Evaluation Results – Line R/S (East) Wall .......................................................................................... 5 Evaluation Results – Line 18 (North) Wall.......................................................................................... 7 Evaluation Results – Line 10/9 (South) Wall....................................................................................... 8

EVALUATION OF MCENERNEY STACKS COLUMNS ........................................................................8 Evaluation Results ............................................................................................................................. 10

EVALUATION OF DIAPHRAGMS .....................................................................................................10 Evaluation Results ............................................................................................................................. 10

CONCLUSION AND RECOMMENDATIONS.......................................................................................10

REFERENCES..................................................................................................................................13

Boalt Hall School of Law – University of California, Berkeley January 16, 2009 Seismic Assessment Report Page ii

APPENDIX: STRUCTURAL CALCULATIONS

1.0 Existing Building Properties 1.1 Material Properties 1.2 Mass and Dead Load Takeoff 1.3 Site Specific Spectra

2.0 Shear Wall Evaluation 2.1 Level One Wall Evaluation 2.2 McEnerney Stacks Wall Evaluation

2.2.1 Wall Demands 2.2.1.1 Background 2.2.1.2 Modeling 2.2.1.3 Wall Demands

2.2.2 Wall Evaluation 2.2.2.1 Background 2.2.2.2 Modeling 2.2.2.3 Wall Capacities and Evaluation Results

2.3 McEnerney Stacks Wall Retrofit Evaluation 2.3.1 Background 2.3.2 Modeling 2.3.3 Results

3.0 McEnerney Stacks Column Evaluation 3.1 Column Limit State Calculations Based on Fix-Fix End Restraint Condition

3.1.1 Background 3.1.2 Modeling 3.1.3 Results

3.2 Column Demand Calculation Limited By Slab Flexural Capacity 3.2.1 Background 3.2.2 Modeling 3.2.3 Results

3.3 Column Demand Calculation Limited By Slab Punching Shear Capacity 3.3.1 Background 3.3.2 Modeling 3.3.3 Results

3.4 Column M10 Evaluation 3.4.1 Background 3.4.2 Results

4.0 Diaphragm Evaluation 4.1 Diaphragm Capacity Calculations 4.2 McEnerney Stacks Level S6 Evaluation

Boalt Hall School of Law – University of California, Berkeley January 16, 2009 Seismic Assessment Report Page iii

LIST OF FIGURES Figure 1: Boalt Hall Substructures ........................................................................................................ 2 Figure 2: Site Design Spectra ................................................................................................................ 4 Figure 3: Walls Included in McEnerney Stacks Area Evaluation – Plan View..................................... 5 Figure 4: Line R/S Wall Pier DCR........................................................................................................ 6 Figure 5: Line 10 Dowel Detail ............................................................................................................. 7 Figure 6: Line 18 Wall Pier DCR.......................................................................................................... 7 Figure 7: Line 10/9 Wall Pier DCR....................................................................................................... 8 Figure 8: Typical Interior Reinforced Concrete Column Sections at McEnerney Stacks ..................... 9 Figure 9: Line 18 Wall Modifications ................................................................................................. 11 Figure 10: Line R/S Wall Modifications ............................................................................................... 12 Figure 11: Line 10/9 Wall Modifications .............................................................................................. 12

Boalt Hall School of Law – University of California, Berkeley January 16, 2009 Seismic Assessment Report Page 1

PURPOSE

In conjunction with making a substantial investment in a new Infill Building, as well as making various renovations to its existing facility, UC Berkeley Capital Planning has requested more detailed information regarding the expected seismic performance of the existing Boalt Hall building and recommendations for measures that would be prudent to construct in conjunction with proposed renovations.

In a previous seismic evaluation [1997 Preliminary Seismic Evaluations, University of California, Berkeley], Boalt Hall was rated “GOOD” under the University Policy on Seismic Safety (UPSS) guidelines.

The purpose of this report is to present results and recommendations based on a more detailed seismic assessment undertaken in order to verify and supplement the findings of the earlier seismic evaluation. The report identifies specific areas where minor seismic improvements should be undertaken in conjunction with building renovations currently under design.

This assessment is not intended to satisfy the requirements of CBC Section 3415 for seismic assessment and retrofit of existing State-owned buildings, which is applicable to buildings that undergo such substantial renovation or structural alteration that seismic retrofit is warranted.

BUILDING DESCRIPTION

General Description

The home of the School of Law at University of California Berkeley, Boalt Hall is located in the southeast corner of the campus, about 0.5 km from the Hayward Fault. The original building, which was constructed in 1949, consists of four distinct functional parts that are structurally connected.

At the far west of the complex is the Classroom Wing, composed of two occupiable floors: a partially subterranean basement and a classroom level containing three large, sloped-floor auditoriums. The classroom wing is covered by a hip roof.

McEnerney Reading Room runs along the south edge of the complex, occupying two floor levels. The first floor consists of several meeting rooms and offices under a single large reading room at the second floor. The tall Reading Room space is also covered by a hip roof.

The McEnerney Stacks portion of the building originally consisted of four occupiable floors and a flat roof. In 1958, additional floors were added to the stacks area, increasing the number of occupiable floors from four to eight. In this final configuration, Levels S3, S5 (the original roof), S6, and S9 (the final roof) are of conventional concrete slab construction. The intermediate floor Levels S2, S4, S7, and S8 are of light reinforced concrete construction, partially supported by the Stacks shelving structure. The stacks were further renovated in 1996, when a significant portion of the stack floor slab at Level S4 was eliminated and minor changes were made to the north wall.

A Connector segment links the Classroom Wing, the Reading Room, and the book storage Stacks area. This connector houses some library facilities and offices over three occupiable elevated floors and a small

Levels L2, L3, L4 and Roof

Levels L1M, L2M, L5 and L6


basement area below grade. As opposed to the classroom and reading room areas, the connector area has a flat roof to accommodate some mechanical equipment and an elevator penthouse.

Figure 1: Boalt Hall Substructures

Various other structures that comprise the law complex, and were rated as “Good” in the Preliminary Assessments, are not included in this more detailed evaluation. These areas are all structurally separated from Boalt Hall. Simon Hall (initially referred to as Earl Warren Legal Center), was added to the east of Boalt Hall. To the east of the McEnerney Stacks, Robbins Hall is a seismically separate office structure. Another addition to Boalt Hall is the reading room and office structure located north of McEnerney Stacks. This seismically separated structure lacks a unique name on the campus map.

Structural System

Gravity System

The majority of Boalt Hall uses a common gravity load support system. In the Classroom Wing, the McEnerney Reading Room, and the Connector Area, a complete structural steel frame provides support for gravity loads. Typical floor construction consists of one-way reinforced concrete slabs supported by concrete encased steel beams.

At the Classroom Wing and at the McEnerney Reading Room, terra cotta tile roofing is supported on a 4 inch thick one-way reinforced concrete roof slab. Steel trusses, spanning between perimeter columns, support the roof slab. At the connector area, a sloped terra cotta tile roof over a reinforced concrete slab


system exists at the building perimeter, supported on sloping concrete encased steel beams. The connector interior area is supported by a flat roof system for mechanical equipment and an elevator penthouse. The flat roof consists of a reinforced concrete slab supported on concrete encased steel beams.

Although the McEnerney Stacks are seismically connected to the remainder of the structure, this portion of the building uses a distinctly different structural system. The gravity system for the stacks area includes mostly reinforced concrete columns, with some concrete encased steel columns along the southern boundary of the stacks. Columns with capitals support conventional reinforced concrete flat slab floors at Levels S3, S5, S6, and the roof (S9). Perimeter concrete walls, with integral pilasters, provide gravity support for the floor slabs at the building perimeter. Intermediate stack floors are inserted between the main flat slab floor levels. These intermediate 3 ½” reinforced concrete stack floors are supported by building columns, perimeter walls, and the light-gauge steel posts that make up the library book stacks.

Both perimeter and interior shear walls are founded on shallow strip footings. Columns are supported by spread footings at the foundation level.

Lateral System

Lateral forces are resisted by reinforced concrete diaphragms spanning to reinforced concrete shear walls. Perimeter shear walls with punched openings surround Boalt Hall on all sides. These perimeter walls vary in thickness from 8 inches to 14 inches. In the classroom wing, two significant interior walls run east/west on Lines 4 and 10, and a single long wall runs north/south on Line E. Shorter interior walls exist throughout the other building substructures.

EVALUATION METHODOLOGY

In order to assess the seismic performance of Boalt Hall, engineering analysis was performed based on existing standards including ASCE 31-03, ASCE 41-06 (Supplement 1), and FEMA 306. All calculations used linear procedures to investigate the performance of critical components of the lateral load path including shear walls, columns, and diaphragms.

The portions of Boalt Hall within the scope of this assessment include the initial 1949 construction and the addition to McEnerney Stacks constructed in 1958. Material properties for the original construction were not available during this assessment. As a result, lower bound material properties from ASCE 41-06 Tables 6-1 and 6-3 were used. For the 1958 addition, the material properties specified on structural drawings were considered as lower bound values. Expected material properties for each period were established per ASCE 41-06 Table 6-4.

Earthquake demands for linear analyses were based on site specific spectra equivalent to BSE-1 hazard level capped at 1.5 g.


University of California Berkeley: Boalt HallSite Design Spectra -

Based on 10%/50 Year Hazard (vS= 540 ft/sec)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

T (sec)

Sa (g

) 2007 UCB 10%/50 YRDesign Spectra

Figure 2: Site Design Spectra

EVALUATION OF CONCRETE SHEAR WALLS

Evaluation of Level 1 Walls

At Boalt Hall, resistance to lateral forces is provided by a series of reinforced concrete shear walls, occurring both at the building perimeter as well as at a number of interior locations. A wall demand capacity check was performed to determine the adequacy of the first floor walls, where a large number of punched window and door openings are located. The check was based on a linear static procedure per ASCE 31-03, where expected wall capacities are compared to wall demands assuming the building period falls in the constant acceleration region of the design spectra. Wall demands are computed assuming a rigid diaphragm and earthquake forces transferred to walls in proportion to their shear area. In this simplified check, the additional effects of the torsional moment due to eccentricity between the building centers of mass and rigidity are assumed to be negligible and are ignored. The presence of reinforced concrete shear walls at the entire building perimeter tends to effectively resist any torsional moments in the building with minimal effect on the wall shear demands.

Evaluation Results

Demand-Capacity Ratios (DCR’s) for walls in each primary direction are typically less than 2 which satisfy the Life Safety Performance criteria per ASCE 31-03. Refer to the appendix for DCR results.

McEnerney Stacks Walls

The McEnerney Stacks area contains two significant vertical irregularities. At the Stacks Level 5 (S5), perforated openings were introduced to the north and east perimeter walls during the 1958 addition. These openings, which reduce the wall area, create a substantial strength and stiffness irregularity at Level S5.


An additional irregularity occurs due a discontinuity in the wall that forms the southern boundary of the Stacks, between Levels S4 and S3. The southern boundary defined by an 8” wall (located at grid line 10) does not continue below Level S3. The southern wall below Level S3 shifts south to a location near grid line 9.

In order to determine whether sufficient capacity exists at these vertical irregularities, a more detailed investigation of the McEnerney Stacks was performed. A linear dynamic procedure per ASCE 41-06 was used to compute wall demands. Story shears were calculated using the results of a dynamic analysis on a stick model which reflected the shear area and moment of inertia of the Stacks’ walls at each Level. Each wall property was computed including the appropriate width of perpendicular wall flange area. Wall pier capacities were computed based on the methodology outlined in FEMA 306 Section 5.3.6.

Earthquake forces are distributed to the wall piers based on the flexural and shear rigidities of each pier, considering both accidental eccentricity and torsion due to plan separation of the centers of mass and rigidity. The acceptance criteria for shear walls were based on ASCE 41-06 as follows: i) Demand Capacity Ratios (DCR) below 2.5 meet the Life Safety performance criteria; ii) DCR greater than 3 fails to satisfy the criteria. Intermediate DCR values between 2.5 and 3 provide marginally acceptable performance. A DCR greater than 3 on an individual pier was judged acceptable in areas where adjacent wall piers have sufficient excess capacity. The weighted average DCR of all piers on a wall line was used to determine if there is sufficient excess capacity (i.e. DCRave < 2.5).

Figure 3: Walls Included in McEnerney Stacks Area Evaluation – Plan View

Evaluation Results – Line R/S (East) Wall

Like the north wall of the McEnerney Stacks, the east wall is broken up into a number of piers due to the perforated wall openings at Level S5. The analytical investigation revealed that many of the eastern wall piers at Level S5 are over-stressed and do not meet the ASCE-41 parameters for the life-safety


performance objective. The piers are made vulnerable by the number of wall openings added during the 1958 modifications. Refer to Figure 4 for pier demand-capacity ratios.

Figure 4: Line R/S Wall Pier DCR

An alternate load path was investigated, using the Level S6 diaphragm to transfer north-south direction story shear forces into roof of the Reading Room area and ultimately into the Reading Room walls. However, the S6 diaphragm connection along Line 10 between the Stacks and the reading room was found to be inadequate. At the time of the 1958 Stacks addition that included the construction of the S6 slab, the wall at Line 10 already existed above Level S6 as the northern boundary of the Reading Room. As a result, the Level S6 slab is connected to the wall at Line 10 using grouted dowels with limited capacity. Refer to Figure 5.

It should be noted that in the course of renovations subsequent to the 1958 addition, a number of the Stacks area north and east wall openings have been covered; presumably by architectural finish which can be in-filled using reinforced concrete as a strengthening measure.


Figure 5: Line 10 Dowel Detail

Evaluation Results – Line 18 (North) Wall

Line 18, at the north wall of the Stacks, is one of the critical areas, due to the number of perforated wall openings added during the 1958 construction. The rigidity based analysis of Levels S5 and S6 shows that the average DCR for each level meets the criteria for acceptable performance. Since the southern Stacks wall at Line 10 is continuous, with no openings, much of the east/west earthquake forces are resisted by that stiffer wall. The stockier end piers at Line 18 experience the highest DCR at both Level S5 and S6. At Level S5, these piers exceed the acceptable performance level. Refer to Figure 6 for pier demand-capacity ratios.

Figure 6: Line 18 Wall Pier DCR


Evaluation Results – Line 10/9 (South) Wall

At the southern boundary of McEnerney Stacks, a discontinuous 8 inch thick shear wall provides resistance in the east/west direction. Below Level S5, where the demands on the piers were generally lower, earthquake forces are distributed based on the shear area of wall piers. Our analysis results indicate that above Level S4, the continuous wall provides sufficient capacity to resist expected shear demands. At Level S3, the diaphragm capacity is sufficient to transfer the discontinuous wall forces to other walls below Level S3. Further, the overall wall line below Level S3 has sufficient capacity.

However, the analysis shows that the Line 9 wall, located south of the discontinuous wall below Level S3, is overloaded due to the limited sliding shear capacity of the wall. Although the available documentation is incomplete, it appears that the wall piers between R/10 and S/10 at S1 received only architectural infill at the time of the Simon Hall construction in 1967. As a result, these piers fail to meet the criteria for acceptable performance.

Figure 7: Line 10/9 Wall Pier DCR

EVALUATION OF MCENERNEY STACKS COLUMNS

The McEnerney Stacks area is the only portion of Boalt Hall that lacks a structural steel gravity load support system. Stacks’ gravity loads are supported by a concrete two way flat slab floor system that spans to reinforced concrete columns with capitals and perimeter walls. The concrete columns are reinforced with widely spaced ties, typical of the construction era.

In a two-step evaluation, the behavior of concrete columns was investigated to determine whether they have adequate capacity to resist earthquake induced forces and story drifts.

Initially the evaluation was performed assuming that column hinging occurs at the major [8 ½”] slabs and that the stacks [3 ½”] slabs offered no significant bending restraint. A slab punching shear capacity check


revealed that all intermediate, light [3 ½”] slabs in the McEnerney Stacks (S2, S4, S7, S8) lack the ability to induce significant moment in the columns.

Based on this assumption, column shear demand-capacity ratio was used to characterize the likely column limit state per ASCE 41-06 Section 6.4.2.2.2. Column shear capacity was computed per ASCE 41-06.

Evaluation results indicated that all interior reinforced concrete columns above Level S5 exhibit flexure critical behavior and interior columns below Level S5 are shear critical. The change in limit state mainly corresponds to the change in the column reinforcing in the two construction eras (1949 vs. 1958). Level S5 was the roof of the original 1949 Stacks area. The flexural capacity of the Addition columns is reduced significantly due to a reduction in longitudinal reinforcing steel, commonly from 8-#10 in the 1949 construction to 8-#8 in the 1958 columns. This change constitutes almost a 40% reduction in longitudinal reinforcement. At the same time, although the transverse reinforcement ratios are relatively close [#4 bars at 1’-8” on center (AS/bs = 0.00091) are provided in the 1949 columns, while #3 bars at 1’-0” on center (AS/bs = 0.00083) are provided in the 1958 columns], the original columns have tie spacing almost equal to the effective depth of the columns, therefore offering greatly reduced shear capacity.

Figure 8: Typical Interior Reinforced Concrete Column Sections at McEnerney Stacks

In the next step, the assumption that the column hinging occurs at the major floor slabs was inspected. In order for the shear critical limit state to control column behavior below S5, the structural slabs must have sufficient flexural and/or punching shear capacity to generate the column hinge moment. It was determined that at all Levels (S3, S5, S6, S9), the major slab flexural capacity is inadequate to create a shear critical limit state in the Stacks columns. The [8 ½”] slab punching shear capacity was found to be greater than the demands associated with the maximum probable moment capacity of slab, which is a desirable condition.


Evaluation Results

The above investigation revealed that the floor slabs lack sufficient capacity to create a shear critical limit state in the Stacks columns. The columns are expected to only experience flexural hinging at their base (S1) at a relatively large seismic drift which is not expected for this stiff structure. Although this performance is generally considered adequate to meet the Basic Safety Objectives of ASCE-41 (life-safety in DBE and collapse-prevention in MCE), we recommend that the columns at lower levels (1949 construction) to be jacketed by fiber reinforced polymer (FRP) as part of renovation work. The FRP wrap would provide additional confinement and shear capacity for the original (1949) columns that have wide tie spacing.

EVALUATION OF DIAPHRAGMS

In the Classroom Wing, the McEnerney Reading Room, and the Connector Building, the shear walls possess adequate capacity to resist earthquake shear forces. As a result, large, concentrated diaphragm shears are not expected. The diaphragms in these areas are well tied to the surrounding walls and the connection has sufficient capacity to transfer shear forces.

At the McEnerney Stacks, the diaphragms are well connected to the perimeter shear walls. The exception occurs at Level S6, the first new level added during the 1958 Stacks Addition. As shown in Figure 6, the connection at Line 10 to the existing Reading Room wall consists of grouted ¾” diameter A307 machine bolts.

Evaluation Results

The ability of this detail to develop the bolt capacity is uncertain. Assuming the bolts have sufficient embedment to develop the machine bolt, the connection DCR is 2.36. This result exceeds the acceptable value of 2.00 per ASCE 31-03 Section 4.2.4.3.2.

CONCLUSION AND RECOMMENDATIONS

The Boalt Hall lateral force resisting system, excluding the McEnerney Stacks area, possesses sufficient strength, stiffness, and ductility to meet the Life-Safety performance objective as defined in ASCE-41 Standard. On this basis, we confirm that the building should generally be rated “Fair” to “Good” in accordance with UC Seismic Safety Policy.

Our analysis, however, has identified localized structural deficiencies in the Stacks area, caused by the 1958 Addition and structural modifications that should be corrected to maintain this rating. Specifically, we recommend that the following items are required to be corrected in conjunction with renovations that are proposed at this time.

1. At the North exterior wall of the stacks, structurally infill existing openings at Level S5 and S6 between Lines N and O with reinforced concrete as shown in Figure 9. These openings are currently covered with architectural finishes; however, we have found no documents to suggest that they have been structurally filled.


2. At the East exterior wall at Stacks Level S5, infill existing openings with reinforced concrete as shown in Figure 10. These openings are currently covered with architectural finishes; however, we have found no documents to suggest that they have been structurally filled.

In order to further enhance the seismic performance of the building toward achieving “GOOD” performance rating, we recommend the following additional improvements:

1. Improve the connection between the 1958 portion of the McEnerney Stacks Addition and the adjacent Reading Room walls, at Level S6 diaphragm. This involves adding grouted dowels between Line 10 concrete wall and Level S6 diaphragm.

2. Although analysis shows that the reinforced concrete columns at the McEnerney Stacks are not likely to experience critical limit state forces and deformations in the design earthquakes (DBE and MCE), it is recommended to improve the performance of lower level columns between levels S1 and S5 by jacketing them with fiber reinforced polymer (FRP) as renovation work is performed at these levels. The FRP wrap would provide additional confinement and shear capacity for the original (1949) columns that have wide tie spacing.

3. It is recommended to infill the Level 1 wall openings between Lines 10/R and 10/S and Lines R/6 and R/10 (adjacent to Simon Hall) with reinforced concrete. These openings are currently covered up with architectural finishes. Refer to Figures 10 and 11.

Figure 9: Line 18 Wall Modifications


Figure 10: Line R/S Wall Modifications

Figure 11: Line 10/9 Wall Modifications


REFERENCES

The following reports and publications were used for information in the course of this investigation:

1. American Concrete Institute, (2008), Building Code Requirements for Structural Concrete and Commentary, ACI Standard, (ACI 318-08).

2. American Society of Civil Engineers, (2003), Seismic Evaluation of Existing Buildings, ASCE Standard, (ASCE/SEI 31-03).

3. American Society of Civil Engineers, (2006), Seismic Rehabilitation of Existing Buildings, ASCE Standard, (ASCE/SEI 41-06).

4. Federal Emergency Management Agency, (1999), Evaluation of Earthquake Damaged Concrete and Masonry Wall Buildings, Basic Procedures Manual, (FEMA 306).

FORM 1 CERTIFICATE OF SEISMIC PERFORMANCE LEVEL UC ......Campus: UC Berkeley Building Name: Boalt...

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