Structural Assessment

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STRUCTURAL ASSESSMENT

REPORTfor

Existing Structure at Cooley Landing

2100 Bay Road, East Palo Alto, California


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Executive Summary

Structech Engineering Inc. performed an evaluation of the existing boat shop structures at the

Cooley Landing site in East Palo Alto. The existing structure is composed of two (2) sections, a

one story, building (North Section) relocated to this site in 1963, and a two story addition to the

south end of the older one-story section constructed at the site in 1965 (South Section).

The purpose of this assessment is to evaluate the feasibility of restoring the existing structures

for safe public access in serving the East Palo Alto Community.

The evaluation task included assessment of the existing structural members, such as roof,

bearing walls, foundations, and interior slab on grade for both gravity loads as well as lateralloads (wind and seismic).

Our firm has concluded the following:

Structural framing of the roof, floor, and bearing walls, with some strengthening andenhancement may be able sustain the minimum gravity and lateral loads as prescribed by

the California Building Code (CBC).

The existing foundation may be adequate for the anticipated light commercial serviceloads. The North Section (one-story) however, does not appear to be anchored to its

foundation properly.

Interior building slab shows signs of age and cracks have developed in several places.We do not believe that the slab in underlain by any type of moisture barrier.

The exterior siding has been exposed to the elements for too long without properprotection. Siding has decayed in several areas, and on the west elevation is in contact

with adjacent grade.

The boat launch structural steel has been exposed to the elements without properprotection. The rust is more pronounced at the steel posts where it is within the water

level. We believe with proper care and some repairs this structure can be reused for light

service loads.


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Table of Content Page

Description of Structure 4

Structural Assessment and Recommendations

1. Roof Framing System 52. Wall Framing System 63. Second Floor, Exterior Rear Balcony, and Access Stairs 74. Foundations 85. Boat Launch 96. Site Drainage Adjacent to the building 97. Conclusions 10Appendix I Cooley Landing Photos 11

Appendix II Cooley Landing Schematics 27


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Description of Structure (Photos 1-10)

The structure is composed of two sections and was used as a repair facility (See Photo 1):

North SectionThis section is the original one story building; relocated to this site. The building has12-6 wall plate height and a gable roof with slope of 4:12. The roof is supported on wood trusses

placed at 6-0 on centers and intermediate 2x6 roof rafters between trusses at 2 feet on centers. It is

stated that the North section was moved to Cooley Landing about 1963 in 3 sections (See Photos 2-5).

This section of the structure was used as boat repair area.

The building foot print dimensions are 32 feet wide by about 69 feet long, connected to the 2-story

South Section addition. This section has little or no seismic or wind load resisting features at the current

state.

South SectionThis section is a two story addition to the North Section. The section has two levels,

with balloon framed walls. Each level is approximately 9-0 high. The roof is gabled with a 4:12 slope.

The roof framing seems to be composed of 2x6 rafters. The second floor is framed with 2x12 at 16" on

centers. This section was constructed about 1965. (See photos 5 - 10). The structure appears to be

unfinished with exposed plywood as siding. The interior walls have no wall sheathing or insulation.

This portion has a second floor deck facing the San Francisco Bay.

The building approximate foot print dimensions are 32 feet wide by 35 feet long and is connected to the

south face of the North Section.


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Structural Assessment and Recommendations

1. Roof Framing System (Photos 11-16)The roof framing system over the one story North Section is composed of tar paper and gravel

roofing over 1x 6 horizontal wood slat which are placed perpendicular to the main load carrying

roof trusses, spaced at 6-0 on centers, and intermediate 2x6 roof rafters, spaced at 2' on centers.

Based on the age of the structure and the excessive exposure of tar paper and gravel roofing, we

believe the nailed connections between roof slats and the roof framing members are inadequate

to resist any uplift generated by wind load on the roof . The system also lacks the required roof

diaphragm features needed to resist lateral loads.

The roof rafters and the top chord of the trusses are supported by intermediate purlins, spaced at

8 feet from side walls running along the longitudinal direction of the building (See Photos 11-

13). The roof trusses are constructed from 2x6 wood chords and web members with 1 to 3

machine bolts connections depending on the location. The bottom cord of the trusses are

attached to 1x6 cross braces with a single machine bolt (See Photos 1416), and at some

locations the bottom chord cross bracing has been cut to accommodated electrical and other

equipment clearances.

The two story South Section roof system is constructed with 2 x6 rafters at 2-0 on centers with

plywood roof sheathing. We believe that the roof plywood in this section has also deteriorated

and will require replacement before a new roofing is installed.

Recommendation 1 : It is recommended that a comprehensive analysis of the building roof system for

gravity and lateral loads to be performed per American Society of Civil Engineers (ASCE) publication

7-05 and the 2007 California Building Code (CBC). Any repairs to the roof should include the creation

of a diaphragm system such as plywood sheathing and proper nailing to the framing members below.

The framing, which includes roof rafters and roof trusses, should be evaluated for anticipated loads and

reinforced accordingly to meet the minimum code requirements. While major roof repairs are

anticipated, we advise that the roof for both North and South Sections be protected temporarily in order

to minimize further weather damage to the framing members.


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2. Wall Framing System (Photos 1-10 & 17-21)The general construction of the exterior load bearing walls in the older North Section is 2x6

studs at 24" on centers. At approximate wall height of 12'-6", we believe that the stud size is

adequate for this section. The South Section exterior walls are composed of 2x4 studs, balloon

framed at 16" on centers. Based on the length and slenderness of these studs some modification

may be necessary in these walls in order to account for the excessive stud heights. In all cases, a

thorough examination of all wall framing for exposure and termite damage is in order prior to

any modification or reinforcement.

Crane runway on the North Section of the building is supported by wood corbels attached to 6x6

wood posts. The connections of the wood corbel to the wood post are via a machine bolt and a

partial bearing within a notch on the post (See Photos 17-18). If the future use of the building

would require full usage of the crane, a detailed analysis of the crane support system would be

required per ASCE 7-05 and the 2007 CBC. If the future use of the building would require the

carne to operate in an entirely unloaded mode, the system of railing and supports should be

evaluated by calculations and careful visual examination of its condition to assure ultimate

safety for the building occupants and visitors.

As it can be observed from Photos 1-9 and 18 through 21, the existing exterior walls have

number of window and door openings. The North Section's exterior siding is believed to be of

milled redwood (all three elevations). There are visible damages to the siding in some areas

resulting from exposure, rotting, and breakage. Even with adequate repairs and partial

replacement, the existing wood siding is inadequate to resist any lateral loads induced by wind

or earthquake. If it is desired to keep and refurbish the existing wood siding, the damaged areas

may be replaced with similar dimensional wood siding, milled to existing specifications to

preserve the originality. In such case, the retrofit of the exterior load bearing walls will have to

be accomplished by applying structural sheathing to the inside face of the wall framing to

provide adequate lateral load carrying capacities. Alternatively, the existing siding can be

removed and replaced with similar dimensional and architectural siding after application of

plywood and building paper to the exterior side.


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The South section is entirely sheathed with unprotected plywood panels. This section has large

openings on two sides. The remaining solid walls would need to be retrofitted to act as lateral

load resisting elements with proper plywood sheathing and anchorage. The existing plywood

siding is damaged and is not usable for any purpose.

Recommendation 2: It is recommended that a comprehensive structural analysis of the combined

building sections to be performed for gravity and lateral loads (seismic and wind) per ASCE 7-05 and

the 2007 California Building Code (CBC), to determine the required lateral load resisting systems. This

effort should include the usage of as many existing structural members as possible, but adding the proper

devices, anchorage, and connections that will bring the entire building up to current building code

standards.

3. Second Floor and Balcony in South Section (Photos 22-26)We were not able to access the second floor at the time of our site visits because of failing

exterior stairs and the fact that all openings to this area were boarded up. We did note that the

floor framing is 2x12 joists spaced at 16" on centers supported by two (2) interior bearing walls

located at about 14 feet and 24 feet of exterior west wall (See Photos 22-25). The floor joist

members are believed to be adequate for the anticipated gravity loads, however, the floor

decking and the nailing to the floor joists will have to be examined and verified for the building

use and lateral load diaphragm demand/capacity per ASCE 7 -05 and the 2007 CBC.

This assessment is within the parameters of Recommendation 2 in the previous section.

There is a cantilever wood balcony at the rear (facing the Bay) of the South Section. Because

of the excessive exposure to elements, we believe that this area is currently unsafe for any

type of usage. A telling sign of this condition is the fact that the exterior stairway leading

to the balcony has completely failed for the similar reasons. If the balcony is to be used in

the future, we recommend removal of the existing damaged joists and installation of new

floor joists overlapped with joists inside the building. As an alternative, the balcony can

be supported on the building wall at one end, and support beam and posts at the outer

end. Both of these alternatives require structural calculations to ensure adequate capacity

per ASCE 7-05 and 2007 CBC for commercial use application.


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4. Foundations (Photos 27-29)Based on our preliminary investigations and exposing a small portion of the exterior footings for

both building sections, we have determined that the existing foundation is generally composed

of an exterior grade beam and monolithically poured in place slab on grade floor. The existing

exterior grade beam appears to be in good condition (no major structural cracks observed), and

in compliance with the requirements for the area, as outlined in theReport File Number

770771/007 by Kleinfelder, dated May 23, 2007. The depth of the exterior grade beams for

both building sections were approximately18 inches. The width of these grade beams were

estimated to be between 12 to 15 inches. These footings seem sufficient in size for light

commercial type use of the building. Our staff did not perform exploration or testing for

concrete reinforcing steel within the footings. This inexpensive and non-destructive testing

should be done within the frame work of a major structural design and analysis as to ensure that

the foundation can sustain the induced gravity and lateral loads to the fullest extent possible. It is

important to mention that the use of fully loaded operational crane or generally using the

buildings for industrial operation would require a more robust foundation system capable of

resistance against crane or equipment induced vibrations.

The interior slab on grade has developed cracks and slight heaves in various locations. This slab

seems to be of poor quality, without a moisture barrier, and unknown reinforcement. The latter,

combined with the fact that the building site was previously used as a disposal area suggests that

some of the cracking may be attributed to swelling of sub grade below, or uneven loading

caused by crane usage and heavy boat loads. There is also a possibility that methane gas

produced by decaying disposed material may exist throughout the site, including below the

building slab. While it is possible to repair the existing slab and seal it with an epoxy coating

capable of preventing methane leakage inside the building, it is much more cost effective in the

long run to remove the existing slab in its entirety and replace it with a new reinforced slab.

Providing a stable and compacted sub grade and proper vapor barrier below the new slab will

better accommodate future uses of this building.

Recommendation 3: It is recommended that a non-destructive testing be done to determine the

existence of horizontal steel reinforcement near the top and bottom of the exterior grade beams. This is


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critical because the uplift and downward forces produced in seismic and wind loading conditions cannot

be fully resisted without reinforcement in the footings.

Based on our observations, we found no anchor bolts connecting the North Section walls to the exterior

grade beams. As a part ofRecommendation 2, the required wall anchorage to the foundation can be

calculated based on ASCE 7-05 and the 2007 California Building Code (CBC). We recommend using

Simpson "Titen" or epoxy anchors in the existing concrete.

5. Boat LaunchThis is an existing structure composed of two rows of 12" diameter steel posts and series of

pipes, wide flanges, and channel steel members as main support. The system supports a

movable open steel platform previously used to lower the boats into the water. Our visual and

preliminary inspection has revealed that excessive rust has developed on most of the structural

steel because of contact with salt water and lack of maintenance. This is more notable in places

where standing water can occur, and on the steel posts where it meets the Bay's water level. In

our opinion this structure is no longer reliable to carry heavy boat loads in the current state. The

structure can however be modified and possibly retrofitted for a walking or fishing platform.

The latter requires design modification and fortification to mitigate the effects of rust in several

places as well as removal of excess weight not necessary for the lighter usage.

6. Site Drainage Adjacent to the building (Photos 1-10)Based on the field geotechnical investigation report by Klienfelder (Report File Number

770771/007 by Kleinfelder, dated May 23, 2007), an approximately a two (2) inch thick

pavement section has previously been placed at the north and west elevations of the North

Section. This paving is at or in some locations above the top of the grade beam or the interior

slab. Thus, some untreated structural members and wood siding are in direct contact with the

adjacent grade, resulting in decaying and deterioration of the wood members.

The soil strata under the pavement and surrounding the building perimeter are composed of

fill to depths of about 18 feet. The fill consist of about 5 to 10 feet of soft to very stiff lean

clay underlain by very loose to medium dense clayey sand to about 18 feet below ground


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surface. The above soft to very stiff clay is very susceptible to seasonal moisture

changes; therefore, a positive drainage away from the building would be required to

avoid excessive foundation movement and cracking.

Recommendation 4: It is recommended that the paving be removed and lightly excavated to an

elevation of minimum 6 inches below the top of the slab and grade beam to avoid direct contact of

wood members with adjacent grade. If another pavement slab is planned, It should be placed no less

than two(2) inches below the top of the building interior slab elevation. Furthermore, the areas

adjacent to the entire building should be sloped away (minimum 2%) for positive drainage from the

perimeter foundation. This is critical in avoiding a cycle of moisture recharging and drying of the

underlying perimeter soil.

7. ConclusionsThe scope of this report has been to concentrate on the structural assessment and integrity of the

existing building. The contents and recommendations provided in this report are based on

multiple site visits, observations, and exploratory excavations adjacent to the exterior

foundations of the North Section and South Section. We are optimistic that a majority of the

framing members can be used as originally intended, but additional modern load resisting

features are required to ensure the structural reliability the building and safety of the future

occupants. Through a comprehensive structural analysis of the existing structure and based on

the current building code requirements, a feasible, value engineered solution for remedial work

can be presented to perform retrofit of the existing buildings to conform to the governing

California building codes for life safety and safe occupancy. The analyses will include an

assessment of each structural components for performing and demonstrating safe behavior under

the imposed and superimposed limit loads and load combinations as required by the governing

codes. Upon completing the required analysis, a final set of plans and construction documents

can be developed and submitted to the Chief Building Official at the City of East Palo Alto for

his review and approval. It has been our experience that all retrofit projects will benefit from

close cooperation of engineers and contractors during the construction. Our firm believes that

such team work will increase efficiency and optimizes the work, thereby reducing engineering


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Appendix I

Cooley Landing Photos


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Photo 1 - Cooley Landing (North Section & South Section)

Photo 2 - Cooley Landing North Section North Elevation


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Photo 3 - Cooley Landing North Section West Elevation

Photo 4 - Cooley Landing North Section & South Section East Elevation


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Photo 5 - Cooley Landing North Section East Elevation

Photo 6 - Cooley Landing South Section West Elevation


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Photo 7- Cooley Landing South Section South Elevation

Photo 8 - Cooley Landing South Section South Elevation


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Photo 9 - Cooley Landing South Section West Elevation

Photo 10 - Cooley Landing South Section East Elevation


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Photo 11 - Cooley Landing North Section Roof Framing

Photo 12 - Cooley Landing North Section Roof Framing


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Photo 13 - Cooley Landing North Section Framing Trusses and Rafters

Photo 14 - Cooley Landing North Section Roof Framing Trusses Cross Tension Members


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Photo 15 - Cooley Landing North Section Roof Framing Trusses and Cross Tension Members

Photo 16 - Cooley Landing North Section Roof Framing Trusses Chord and Web Members Connections


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Photo 17 -Inside view, Cooley Landing Exterior Wall and Corbel

Photo 18 - Cooley Landing Exterior Wall and Crane Runway Support


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Photo 19 - Cooley Landing Exterior Wall at North Section, Wall Opening

Photo 20- Cooley Landing Exterior Wall at 2-Story South Section Opening


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Photo 21- Cooley Landing Exterior Wall at 2-Story South Section South Wall Opening

Photo 22- Cooley landing 2-Story South Section 2ndfloor Joists


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Photo 23- Cooley landing 2-Story South Section 2ndfloor Joists & Blocking

Photo 24- Cooley landing 2-Story South Section 2ndfloor Joists @Bearing Wall Support


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Photo 25- Cooley landing 2-Story South Section 2ndfloor Joists @ Bearing Wall

Photo 26- Cooley Landing 2-Story South Section Balcony and Stair Access


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Photo 27 - Cooley Landing North Section Exterior Grade Beam Foundation

Photo 28 - Cooley Landing North Section Exterior Grade Beam Foundation


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Photo 29 - Cooley Landing South Section Exterior Grade Beam Foundation


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Appendix II

Cooley Landing

Schematic

Plans and Elevations


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Documents

Structural Assessment