Evaluator: XXX Evaluator: EGM/BL Date: 03/06/2019 · Building Name: Botantical Garden Tropic House Evaluator: EGM/BL CAAN ID: 1752 Date: 03/06/2019 Page 2 BUILDING DESCRIPTION General

Evaluator: XXX Evaluator: EGM/BL

Date: 03/06/2019

Page 1

07-15-19

ASCE 41-17 Tier 1 Seismic Evaluation

Building Name: Botanical Garden Tropic House

CAAN ID: 1752

Auxiliary Building ID: Not applicable

Address: 200 Centennial Drive, Berkeley, 94720

Site location coordinates: Latitude 37.873611 o Longitudinal -122.238888 o

Plan East Elevation (Looking West)

UCOP SEISMIC PERFORMANCE LEVEL (OR “RATING”) BASED ON TIER 1 EVALUATION FINDINGS: V

BUILDING DATA

ASCE 41-17 Model Building Type (Governing Building Type bolded for Seismic Risk Model when multiple

types exist):

a. Longitudinal Direction: S3: Light Metal Frame

b. Transverse Direction: S3: Light Metal Frame

Square Footage: 1,709 sq. ft. (UCB Records)

Building Length: 41’-9” (E-W direction)

Building Width: 39’-2” (N-S direction)

Building Height: Slopes, 20’-0” at low point and 29’-8” at high point

Story Height: 20’-0” at low point and 29’-8” at high point

Number of stories above grade: 1

Number of basement stories below grade: None

Year of Original Construction and Code Year: Construction was completed in 1972. The drawings are dated

1971 (1970 UBC assumed).

Year of Later Constuction and Code Year: No retrofits, additions, or alterations

COST RANGE TO RETROFIT (if applicable): High: $200-$400 per square foot

Building Name: Botantical Garden Tropic House Evaluator: EGM/BL

CAAN ID: 1752 Date: 03/06/2019

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BUILDING DESCRIPTION

General

The Tropic House is located in the Berkeley Hills at the UC Berkeley Botanical Gardens north of the core

campus. It is a one-story greenhouse that maintains the collection of tropical plants used by the University

for educational and research purposes. It is also open to the public by admission into the Gardens. The

Tropic House is a rectangular structure that measures 39’-2” by 41’-9” and has a gable framed roof. The

exterior skin of the entire structure is glass. However, the University plans to replace the glass with acrylic

or polycarbonate panels by TECHLITE in the summer of 2019. The original construction drawings

demonstrate design intent, but they indicate the greenhouse was a design-build item. Site observations

indicate that modifications were made to the concept shown in the design documents.

Structural System

On the west and east elevation, the exterior glass panes are supported by aluminum angles measuring

3”x 2”x 3/16” that span horizontally to aluminum vertical posts. The posts are 8”deep channel sections

and run from the ground to the low roof without being spliced. They are bolted to the concrete

foundation wall with a steel angle on one side of the channel web. On the north and south elevations, 4”

deep aluminum channels span horizontally to “W”-shaped aluminum posts. These posts are 12” deep and

are bolted to the concrete foundation with steel angles on each side of the column web.

In the longitudinal direction, the lateral load-resisting system consists of 3/8” diameter steel tension rods

oriented in an “X”-configuration. There is one bay of bracing on the north and south elevation. In the

transverse direction, the lateral load-resisting system is comprised of a mix of steel rod bracing and

aluminum moment frames. The east and west elevations each contain two bays of “X”-shaped, 3/8”

diameter tension rods. Moment frames are located on three interior bays and contain bolted moment

connections at their corners and at the apex of the gable roof. The roof diaphragm consists of one bay of

“X”-shaped steel rod bracing. In general, the rod bracing is eccentrically connected to the columns such

that moment and shear would be imposed on the columns under lateral load.

Along the greenhouse perimeter, the exterior glass walls sit on a reinforced concrete pony wall. This 8”

wide wall is reinforced with a single layer of #4 bars spaced at 12” o.c. in each direction. The wall is

supported by a 24” wide by 14” deep strip footing and varies in height due to a slightly sloping site.

The moment frame columns and building corner columns are supported by 18” x 16” rectangular concrete

pilasters that are integral with the concrete pony wall. The pilasters contain 6-#6 longitudinal bars with

#3 ties spaced at 12” o.c. The pilasters are then supported 24” diameter by 12’-0” deep reinforced

concrete piers. The pilaster reinforcing is continued to the bottom of the pier.

Building Condition: Good

Date of Site Visit: 02/14/2019, Bret Lizundia and Emma Meehan, Rutherford + Chekene

Limitations of walk-through: Member sizes were verified in the field where accessible. Roof framing and

connections above head height were not measured and are not easily reached due to the growth of the

plant collection.


CAAN ID: 1752 Date: 03/06/2019

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SITE INFORMATION

Site Class (A-F): D Basis: Default value per ASCE 41-17 when site conditions are unknown

Site Specific Ground Motion Study? No

BSE-1N Spectral Accelerations: Basis: ATC website, https://hazards.atcouncil.org

SDS: 1.929g SD1: 1.044g Using Site Class D for Default soil

BSE-2E Spectral Accelerations: Basis: ATC website, https://hazards.atcouncil.org

SXS: 2.451g SX1: 1.278g

Level of Seismicity: High

Performance Level: Collapse Prevention Structural Performance

Geologic Hazards:

Fault Rupture: No Basis: CGS website http://maps.conservation.ca.gov/cgs/informationwarehouse/

Liquefaction: No Basis: CGS website http://maps.conservation.ca.gov/cgs/informationwarehouse/

Landslide: Yes Basis: CGS website http://maps.conservation.ca.gov/cgs/informationwarehouse/

PREVIOUS RATINGS SUMMARY

Fair - 1997 Preliminary Seismic Evaluation (SAFER), Degenkolb Engineers

DOCUMENTATION

Architectural Drawings: Botanical Garden Greenhouse and Multi-Use Building, Jack Kositsky

Architect, August 16, 1971, A2 to A4

Structural Drawings: Botanical Garden Greenhouse and Multi-Use Building, Jack Kositsky

Architect, August 16, 1971, S1 to S3

Seismic Evaluations: 1997 Preliminary Seismic Evaluation (SAFER), Degenkolb Engineers

Geotechnical Reports: None

Other Documents: None

CONSTRUCTION DATA

Gravity Load Structural System: Aluminum channel and angle beams spanning to aluminum wide

flange or channel posts

Exterior Transverse Walls: Glass Opening(s)? Door opening

Exterior Longitudinal Walls: Glass Opening(s)? No

Roof Materials/Framing: Glass supported by aluminum channels

Intermediate Floors/Framing: None

Ground Floor: Earth Floor

Columns: Aluminum wide flange and

channel sections

Foundation: Concrete strip

footings below

walls. Concrete

piers below

columns

General Condition of Structure: Structural elements are in good condition with no apparent rust or

deterioration. The glazing is in poor condition. Water and air leaks


CAAN ID: 1752 Date: 03/06/2019

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occur between the glass panes, and the glass is in need of mildew

removal and new whitewash on exterior. The steel rods need to be

tightened.

Evidence of Settling?: No

Special Features & Comments: Falling glass poses a safety hazard

LATERAL-FORCE-RESISTING SYSTEM

Longitudinal Transverse

ASCE 41-17 Building Type: S3: Building Frame S3: Building Frame

Diaphragms: Steel tension rod bracing Steel tension rod bracing

Vertical Elements: Aluminum channel and wide

flange posts

Aluminum channel and wide

flange posts

Connections: Bolted frame connections at

moment frame corners at

apex of roof

Bolted frame connections at

moment frame corners at

apex of roof

Details: Refer to field sketches.

Design documents are not

accurate

Refer to field sketches.

Design documents are not

accurate

Estimated Fundamental Period, T (sec): 0.19 sec 0.19 sec

BSE-2E Spectral Acceleration, Sa: 2.451g 2.4513g

Modification Factor, C: 1.3 (S3 – Table 4-7) 1.3 (S3 – Table 4-7)

Building Weight, W (kips): 24.3 kips 24.3 kips

Seismic Base Shear, V (kips): 77.5 kips 77.5 kips

System Modification Factor, Ms: 3.5 3.5

Significant Structural Deficiencies, Potentially Affecting Seismic Performance Level Designation:

Lateral System Stress Check (wall shear, column shear or flexure, or brace axial as applicable)

☐ Load Path

☐ Adjacent Buildings

☐ Weak Story

☐ Soft Story

☐ Geometry (vertical irregularities)

☐ Torsion

☐ Mass – Vertical Irregularity

☐ Cripple Walls

☐ Wood Sills (bolting)

☐ Diaphragm Continuity

☐ Openings at Shear Walls (concrete or masonry)


CAAN ID: 1752 Date: 03/06/2019

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☐ Liquefaction

☐ Slope Failure

☐ Surface Fault Rupture

☐ Masonry or Concrete Wall Anchorage at Flexible Diaphragm

☐ URM wall height to thickness ratio

☐ URM Parapets or Cornices

☐ URM Chimney

☐ Heavy Partitions Braced by Ceilings

☐ Appendages

OVERALL SEISMIC DEFICIENCIES & EXPECTED SEISMIC PERFORMANCE

The Tropic House at the UC Berkeley Botanical Gardens is a square one-story green house with steel rod

bracing in the E-W direction and a combination of aluminum moment frames and steel rod bracing in the

transverse direction. The Tier 1 assessment of the Tropic House indicated a number of potential

deficiencies. These include overstressed tension rod bracing in the longitudinal direction and insufficient

capacity of moment frame connections in the transverse direction, as well as some nonstructural falling

hazards.

The Tropic House contains two bays of 3/8” diameter rods in the longitudinal direction. These braces have

a stress of 113 ksi under the BSE-2E earthquake, and this significantly exceeds the limit of 0.5Fy which is

18.5 ksi. In addition, the rod bracing is eccentrically connected to the column web which will induce

moment and shear on the column under lateral load. Field investigation of the rods indicates that they

were loose and should be tightened.

The Tier 1 quick check also indicates that the moment frame connections in the transverse direction are

unable to develop the capacity of the moment frame members and do not meet compactness

requirements. It is noted the Tier 1 check is a capacity-based check, and given the light weight of this

structure, it is possible that the development of the full moment capacity is not required

The Tropic House contains four gas heaters, with one located at each corner. These do not contain seismic

bracing and pose a falling hazard. In addition, the glass is a potential falling hazard to occupants. The

current occupants have experienced falling panels when operating the air venting mechanism in the green

house. The glass is difficult to maintain with little to no access to the glass panes located on the roof and

the upper portion of the walls. It required regular power washing on the interior and white washing on

the exterior to reduce glare and heat gain on the plants. The panels are single pane and are not tempered.

The gap between the existing glass panels inside the mullions could not be observed during the site visit.

Seismic Performance Level Rating

A Seismic Performance Level of V is assigned to Botanical Garden Tropic House based on the Tier 1

evaluation, including review of the details and analytical results, because of the deficiencies identified

above including overstressed tension rod bracing in the longitudinal direction, insufficient capacity of

moment frame connections, and nonstructural falling hazards.

Recommended Next Step

It is recommended to complete an ASCE-41 Tier 2 deficiency-based check to verify the columns capacity,

and the expected drift that the frames and glass panes would undergo. The Tier 2 analysis will dictate


CAAN ID: 1752 Date: 03/06/2019

Page 6

whether the columns have sufficient capacity to resist these eccentric loads. Otherwise, it is

recommended to remove the existing rods and replace them with rods and connection plates that are

concentrically detailed. An additional bay of rod bracing can be added to increase the capacity of the

lateral force-resisting system in this direction. The analysis will verify the drift of the frame and the

corresponding demands on the members and their connections. Moreover, the drift will determine if the

glass panes have the ability to rack or rotate during an earthquake to the expected building drift. The

University plans to replace the glass with a new acrylic or polycarbonate panel system in the near future,

and it is recommended that the expected drift of the system be specified in the design criteria

documentation for the new exterior skin.

Since the completion of the Tier 1 assessment, the University authorized Rutherford + Chekene Structural

Engineers to complete a seismic retrofit of this structure. Construction documents for the seismic upgrade

of the Botanical Garden Tropic House were issued and construction is planned to coincide with the glass

replacement project described above in the Summer of 2019.

Seismic Retrofit Concept Sketches/Description (only if above-listed rating is V or greater):

• Replace the existing single pane glass with polycarbonate panels

• Replace existing rod bracing with high capacity bracing or additional bays of bracing. Bracing

connections should be concentric

• Strengthen existing moment frame connections

• Install lateral bracing for gas water heaters

Appendices

A. Additional Images

B. ASCE 41-17 Tier 1 Checklists (Structural)

C. UCOP Seismic Safety Policy Falling Hazards Assessment Summary

D. Quick Check Calculations

APPENDIX A

Additional Images

Building Name: Botanical Garden Tropic House Evaluator: EGM/BL

CAAN ID: 1752 Date: 3/06/19

Page 2

Plan


CAAN ID: 1752 Date: 3/06/19

Page 3

Framing Configuration from Field Measurements


CAAN ID: 1752 Date: 3/06/19

Page 4

East Elevation

South Elevation


CAAN ID: 1752 Date: 3/06/19

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West Elevation

North Elevation with ADA ramp under construction


CAAN ID: 1752 Date: 3/06/19

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Unbraced Gas Heater

Eccentric Rod Bracing


CAAN ID: 1752 Date: 3/06/19

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Greenhouse Interior

Bolted Moment Frame Connection

APPENDIX B

ASCE 41-17 Tier 1 Checklists (Structural)

UC Campus: Berkeley Date: 3/06/2019

Building CAAN: 1752 Auxiliary CAAN:

By Firm: RUTHERFORD + CHEKENE

Building Name: Botanical Garden Tropic House Initials: EGM Checked: BL

Building Address: 200 Centennial Drive, Berkeley, CA 94720 Page: 1 of 3

ASCE 41-17

Collapse Prevention Basic Configuration Checklist

Note: C = Compliant NC = Noncompliant N/A = Not Applicable U = Unknown

LOW SEISMICITY

BUILDING SYSTEMS - GENERAL

Description

C NC N/A U

LOAD PATH: The structure contains a complete, well-defined load path, including structural elements and connections, that

serves to transfer the inertial forces associated with the mass of all elements of the building to the foundation. (Commentary:

Sec. A.2.1.1. Tier 2: Sec. 5.4.1.1)

Comments: Glass is connected to a bolted aluminum frame which transfers load to a combination of moment

frames and steel rod bracing in the transverse direction and steel rod bracing in the longitudinal direction.

C NC N/A U

ADJACENT BUILDINGS: The clear distance between the building being evaluated and any adjacent building is greater than

0.25% of the height of the shorter building in low seismicity, 0.5% in moderate seismicity, and 1.5% in high seismicity.

(Commentary: Sec. A.2.1.2. Tier 2: Sec. 5.4.1.2)

Comments: No adjacent buildings

C NC N/A U

MEZZANINES: Interior mezzanine levels are braced independently from the main structure or are anchored to the seismic-

force-resisting elements of the main structure. (Commentary: Sec. A.2.1.3. Tier 2: Sec. 5.4.1.3)

Comments: No mezzanine

BUILDING SYSTEMS - BUILDING CONFIGURATION

Description

C NC N/A U

WEAK STORY: The sum of the shear strengths of the seismic-force-resisting system in any story in each direction is not

less than 80% of the strength in the adjacent story above. (Commentary: Sec. A2.2.2. Tier 2: Sec. 5.4.2.1)

Comments: One-story structure

C NC N/A U

SOFT STORY: The stiffness of the seismic-force-resisting system in any story is not less than 70% of the seismic-force-

resisting system stiffness in an adjacent story above or less than 80% of the average seismic-force-resisting system stiffness

of the three stories above. (Commentary: Sec. A.2.2.3. Tier 2: Sec. 5.4.2.2)

Comments: One-story structure






ASCE 41-17



C NC N/A U

VERTICAL IRREGULARITIES: All vertical elements in the seismic-force-resisting system are continuous to the foundation.

(Commentary: Sec. A.2.2.4. Tier 2: Sec. 5.4.2.3)

Comments: Lateral system is symmetrical. However, steel rod bracing stops above the bottom of the column.

The column has to “cantilever” down.

C NC N/A U

GEOMETRY: There are no changes in the net horizontal dimension of the seismic-force-resisting system of more than 30%

in a story relative to adjacent stories, excluding one-story penthouses and mezzanines. (Commentary: Sec. A.2.2.5. Tier 2:

Sec. 5.4.2.4)

Comments: Structure is rectangular

C NC N/A U

MASS: There is no change in effective mass of more than 50% from one story to the next. Light roofs, penthouses, and

mezzanines need not be considered. (Commentary: Sec. A.2.2.6. Tier 2: Sec. 5.4.2.5)

Comments: One story structure

C NC N/A U

TORSION: The estimated distance between the story center of mass and the story center of rigidity is less than 20% of

the building width in either plan dimension. (Commentary: Sec. A.2.2.7. Tier 2: Sec. 5.4.2.6)

Comments: Lateral system is symmetrical

MODERATE SEISMICITY (COMPLETE THE FOLLOWING ITEMS IN ADDITION TO THE ITEMS FOR LOW SEISMICITY)

GEOLOGIC SITE HAZARD

Description

C NC N/A U

LIQUEFACTION: Liquefaction-susceptible, saturated, loose granular soils that could jeopardize the building’s seismic

performance do not exist in the foundation soils at depths within 50 ft (15.2m) under the building. (Commentary: Sec. A.6.1.1.

Tier 2: 5.4.3.1)

Comments:

C NC N/A U

SLOPE FAILURE: The building site is located away from potential earthquake-induced slope failures or rockfalls so that it is unaffected by such failures or is capable of accommodating any predicted movements without failure. (Commentary: Sec. A.6.1.2. Tier 2: 5.4.3.1)

Comments: Site is within an earthquake-induced landslide zone per CGS website

http://maps.conservation.ca.gov/cgs/infomrationwarehouse/






ASCE 41-17



MODERATE SEISMICITY (COMPLETE THE FOLLOWING ITEMS IN ADDITION TO THE ITEMS FOR LOW SEISMICITY)

GEOLOGIC SITE HAZARD

C NC N/A U

SURFACE FAULT RUPTURE: Surface fault rupture and surface displacement at the building site are not anticipated.

(Commentary: Sec. A.6.1.3. Tier 2: 5.4.3.1)

Comments:

HIGH SEISMICITY (COMPLETE THE FOLLOWING ITEMS IN ADDITION TO THE ITEMS FOR MODERATE SEISMICITY)

FOUNDATION CONFIGURATION

Description

C NC N/A U

OVERTURNING: The ratio of the least horizontal dimension of the seismic-force-resisting system at the foundation level to the building height (base/height) is greater than 0.6Sa. (Commentary: Sec. A.6.2.1. Tier 2: Sec. 5.4.3.3)

Comments: B = 5.44, H = 20 ft, B/H = 0.27

Sa = 2.4g

0.6 x Sa = 1.47 B/H < 0.6 x Sa

B is the width of a single bay of bracing which occurs in the longitudinal direction. Note the over building length

in that direction is 41’-9”.

C NC N/A U

TIES BETWEEN FOUNDATION ELEMENTS: The foundation has ties adequate to resist seismic forces where footings, piles, and piers are not restrained by beams, slabs, or soils classified as Site Class A, B, or C. (Commentary: Sec. A.6.2.2. Tier 2: Sec. 5.4.3.4)

Comments: Foundation is drilled piers with no ties in the transverse direction. Assumed Site Class D as a

default when site conditions are unknown.






ASCE 41-17

Collapse Prevention Structural Checklist For Building Type S3


LOW AND MODERATE SEISMICITY

SEISMIC-FORCE-RESISTING SYSTEM

Description

C NC N/A U

BRACE AXIAL STRESS CHECK: The axial stress in the diagonals, calculated using the Quick Check procedure of Section 4.4.3.4, is less than 0.50Fy. (Commentary: Sec. A.3.3.1.2. Tier 2: Sec. 5.5.4.1)

Comments: Braces in the longitudinal direction have a stress of 113 ksi which exceeds the limit of 18.5 ksi.

CONNECTIONS

Description

C NC N/A U

TRANSFER TO STEEL FRAMES: Diaphragms are connected for transfer of seismic forces to the steel moment frames. (Commentary: Sec. A.5.2.2. Tier 2: Sec. 5.7.2)

Comments: Glass is held in place using a compression sub-frame. Lateral load transfer to primary frame is through friction.

C NC N/A U

STEEL COLUMNS: The columns in seismic-force-resisting frames are anchored to the building foundation. (Commentary: Sec. A.5.3.1. Tier 2: Sec. 5.7.3.1)

Comments: Steel angles are located on each side of the column web and are through bolted. The angles are then bolted into the concrete foundation.

HIGH SEISMICITY (COMPLETE THE FOLLOWING ITEMS IN ADDITION TO THE ITEMS FOR LOW AND MODERATE SEISMICITY)

SEISMIC-FORCE-RESISTING SYSTEM

Description

C NC N/A U

MOMENT-RESISTING CONNECTIONS: All moment connections are able to develop the elastic moment (FyS) of the adjoining members. (Commentary: Sec. A.3.1.3.4. Tier 2: Sec. 5.5.2.2.1)

Comments: FySy of the connection plates is less than FySy of the frame members. Bolts also do not have sufficient shear capacity.






ASCE 41-17

Collapse Prevention Structural Checklist For Building Type S3


HIGH SEISMICITY (COMPLETE THE FOLLOWING ITEMS IN ADDITION TO THE ITEMS FOR LOW AND MODERATE SEISMICITY)

SEISMIC-FORCE-RESISTING SYSTEM C NC N/A U

COMPACT MEMBERS: All frame elements meet compact section requirements in accordance with AISC 360, Table B4.1. (Commentary: Sec. A.3.1.3.8. Tier 2: Sec. 5.5.2.2.4)

Comments: Column web is slender for axial compression

DIAPHRAGMS

Description

C NC N/A U

OTHER DIAPHRAGMS: Diaphragms do not consist of a system other than wood, metal deck, concrete, or horizontal bracing. (Commentary: Sec. A.4.7.1. Tier 2: Sec. 5.6.5)

Comments: Rod bracing acts as the roof diaphragm

CONNECTIONS

Description

C NC N/A U

ROOF PANELS: Where considered as diaphragm elements for lateral resistance, metal, plastic, or cementitious roof panels are positively attached to the roof framing to resist seismic forces. (Commentary: Sec. A.5.5.1. Tier 2: Sec. 5.7.5)

Comments: Rod bracing acts as the roof diaphragm

C NC N/A U

WALL PANELS: Where considered as shear elements for lateral resistance, metal, fiberglass, or cementitious wall panels are positively attached to the framing and foundation to resist seismic forces. (Commentary: Sec. A.5.5.2. Tier 2: Sec. 5.7.5)

Comments: Connection of glass panels to concrete foundation wall is unknown. In the longitudinal direction, the rod bracing that acts as in-plane wall bracing is eccentrically located above the top of the foundation wall by approximately 18”. Moment and shear are induced in the column due to this eccentricity.

APPENDIX C

UCOP Seismic Safety Policy Falling Hazards Assessment

Summary



By Firm: Rutherford+Chekene



UCOP SEISMIC SAFETY POLICY

Falling Hazard Assessment Summary

Note: P= Present, N/A = Not Applicable

Description

P N/A

Heavy ceilings, features or ornamentation above large lecture halls, auditoriums, lobbies, or other areas where large numbers of people congregate (50 ppl or more)

Comments: Falling glass encasing greenhouse poses a safety hazard to occupants. Note however, that the

glass is scheduled to be replaced with an acrylic or polycarbonate panels in the Summer of 2019.

P N/A

Heavy masonry or stone veneer above exit ways or public access areas

Comments:

P N/A

Unbraced masonry parapets, cornices, or other ornamentation above exit ways or public access areas

Comments:

P N/A

Unrestrained hazardous material storage

Comments:

P N/A

Masonry chimneys

Comments:

P N/A

Unrestrained natural gas-fueled equipment such as water heaters, boilers, emergency generators, etc.

Comments: Unbraced gas heaters occur in each of the 4 corners of the structure and are hung from the roof framing

P N/A

Other:

Comments:

P N/A

Other:

Comments:

P N/A

Other:

Comments:

Falling Hazards Risk: Moderate

APPENDIX D

Quick Check Calculations