RFQ No. 02-26-03 Attachment A.PDF

208 Flynn Avenue, Suite 2A, Burlington, VT 05401 � Tel: 802-863-6225 � Fax: 802-863-6306

85 Mechanic Street, Suite B2-2, Lebanon, NH 03766 � Tel: 603-442-9333 � Fax: 603-442-9331

August 8, 2017

City of Keene, New Hampshire

Attn.: Scott Martin

City Hall EV#16905

3 Washington St.

Keene, NH 03431 smartin@ci.keene.nh.us

Re.: Contract #02-17-43

Structural Engineering Survey at City Hall – 3 Washington St. Keene, NH

Dear Scott:

We have visited and performed a structural visual conditions assessment of the Keen City Hall

Building. Structural observations were completed on March 21 and March 28, 2017. The intent of this report is to provide a comprehensive itemization of findings and recommendations for corrective repairs.

Observations and Assumptions:

1. Our study is based on visual observations of observable portions of the structure. No testing was conducted as part of our work. Additionally, a review of available related documents provided by the City was completed as part of our work. These documents consist of:

a. Renovation plans by Kenneth F Parry and Associates dated April 15, 1982

b. February, 1983 geotechnical report by Soils Engineering, Inc. of Charlestown, NH

c. February, 2017 Field Investigation Report by The City of Keene, regarding an existing water conduit beneath the building.

2. The 2009 International Building Code and International Existing Building Code are the building codes in effect in this jurisdiction and are thus the reference documents for this report. Additional reference is made to Federal Emergency Management Agency, (FEMA) Report No. 574 – ‘Techniques for the Seismic Rehabilitation Of Existing

Buildings’.

3. Our work does not include identification of asbestos or other hazardous materials.

4. The structure consists of two main areas; a 2-story area and a 4-story area, denoted as

Areas ‘A’ and ‘B’ in Figure 1, respectively. The first floor and basement of Area B house a restaurant. The remainder of this area and all of Area A are utilized by the City Hall.

5. Our evaluation encompasses the entirety of the building. It is understood that the request for a building evaluation by the City was precipitated by observations of building movement which they had made, (Figure 2).

6. Other than the documents listed in (1) above, historic information for the buildings is lacking. The original building is believed to have been constructed in the 1800’s. From

March 21 discussions with you it is understood that during pile driving operations from construction of the parking structure adjacent to the west edge of the City Hall building, the exterior wall around the first floor evidence room and second floor restroom became detached from the structure. It is also understood that Area A was originally a three story structure but underwent substantial renovations after a fire, including a reduction in height to two stories. No construction documents are available for this structure, either pre- or post fire. However, a photograph of the original configuration is on display in the City Hall lobby, (Figure 3). The tower in the photograph is in the location of the present day main entrance/lobby area.

7. While onsite it was brought to our attention that the City conducted exploratory work with the intent to more clearly define the layout and condition of a water conduit beneath the building between Feb. 2-6, 2017, (Figure 4). According to the subsequently generated field investigation report, the conduit is believed to be brick, 24 in. in diameter, and to have been constructed in the 1890’s. The work included a push-camera investigation of the pipe. However, according to the report limited information was obtained from the investigation due to blockages in the pipe and extreme bends. It is understood that the City has concerns with possible erosion of soil beneath the building foundation and its possible contribution to structural damage which they had observed.

8. A review of the aforementioned geotechnical report was completed. Several borings were completed at the site, with one extending to bedrock. Bedrock was hit at approximately 86 ft below finish grade. A 15 ft thick ‘soft’ layer of silt and clay was encountered at 50 ft below finish grade, (Figure 5). This poor material would be the likely cause of settlement of the building.

9. The building consists of a blend of different structural systems, briefly described as follows:

a. Area A:

i. Foundation: Areas constructed in 1983 consist of concrete frost walls.

Other areas of unknown date of construction are comprised primarily of a combination rock wall with several courses of brick on top, (Figure 6).

The basement floor consists of a slab on grade.

ii. Exterior Walls: Unreinforced brick masonry (load bearing). Some walls appeared to be original and some constructed as part of subsequent renovations. CMU backup wall was observed in some locations, (North

Wall of Area ‘A’).

iii. Interior Gravity Load Support System: Ground Floor

1. Joist and Deck: Sawn lumber wood floor joists spanning in the north-south direction, topped primarily with wood decking, with lightweight concrete topping in the former cell block area, corridor leading to the sally port, and related rooms.

2. Joist Support: Unreinforced brick masonry load-bearing walls and structural steel beam/columns.

iv. Interior Gravity Load Support System: Second Floor

1. Joist and Deck: Sawn lumber wood floor joists spanning in the north-south direction, topped with wood decking.

2. Joist Support: Similar to Ground floor.

v. Interior Gravity Load Support System: Roof

1. Joist and Deck: Open web steel joists spanning in the east-west direction, topped with wood decking.

2. Joist Support: One line of steel beam/columns spanning in the north-south direction.

b. Area B:

i. Foundation: Areas constructed in 1983 consist of concrete frost walls.

Other areas constructed earlier are comprised primarily of a combination rock wall with several courses of brick on top, (Figure 6). The basement floor consists of a slab on grade.

ii. Exterior Walls: Original existing unreinforced brick masonry, (load bearing).

iii. Interior Gravity Load Support System: Ground Floor

1. Joist and Deck: Sawn lumber joists and wood deck in areas which were not impacted by 1982 renovations. Cold formed steel with concrete-filled metal deck in areas which were renovated, (see

Figure 7).

2. Joist Support: Unreinforced concrete bearing walls and heavy timber girders/brick piers.

iv. Interior Gravity Load Support System: Second, Third, & Fourth Floors.

1. Joist and Deck: Cold formed metal joists topped with concrete-filled metal deck.

2. Joist Support: Structural steel wide flange beams and structural steel columns.

v. Interior Gravity Load Support System: Roof.

1. Joist and Deck: Cold-formed metal deck (without concrete topping).

2. Joist support: Structural steel wide flange beams and structural steel columns.

10. Foundation Structural Observations: Areas A and B

a. Observed portions of the foundations for both areas A and B appeared to be in fair condition overall, considering the age of the structure and soil conditions.

Some cracking of the brick was observed on the south perimeter foundation wall of Area B, (Figure 8). The cracking occurred mostly along brick lines but some cracking was observed extending directly through brick units. Differential settlement is one likely cause of this type of cracking, in addition to poor quality mortar.

b. Mortar deterioration was also observed on the some of the brick piers in Area B, (Figure 10).

c. The basement floor slab in Areas A and B was observed to be uneven but otherwise in fair condition.

d. Diagonal cracking was observed in two foundation walls which intersect the west wall of the building, (Figures 11 and 12).

e. Foundation movement was observed in the form of cracking of the basement ceiling finishes, (Ref. Figure from RFP and related references in Figures 1, 2, 11, and 13 of this report). Due to the damage of finishes which was observed, (Figure 14), selective demolition of finishes in the area was carried out in order to gain a better view of the existing structural conditions, (Figure 15). The existing steel beam supporting deck above was observed to be severely corroded. Additionally, damage to load-bearing wall was observed, which apparently occurred during installation of pipe penetrations, (Figure 16).

f. A telescopic adjustable column was observed in Area A, near the east wall of the building, (Figure 17). It should be noted that these are columns are intended for use in temporary applications and per the building code are not permitted in permanent applications.

g. While on site I was shown a basement floor drain (Figure 18) in Area A and told that it is believed that this drain flows into the below-grade water conduit depicted in Figure 4. It was stated that water occasionally flows out of this drain during rain events.

11. First Floor Structural Observations: Areas A and B

a. Much of the first floor framing of Areas A and B are concealed by finishes. We observed these for signs of discoloration and cracking, which would be indicators of moisture damage and overstress, respectively. Few signs of this were observed other than those already noted as part of foundation observations.

Moisture damage of was observed at some of the joists adjacent to the south wall of Area B, (Figure 19).

b. In many areas the first floor was observed to be out of level. In order to rule out possible causes of this, an analysis of wood joists in Areas A and B was completed. Assuming a lumber grade of spruce pine fir No. 1/2 and assuming no holes or notches in the joists, the existing wood framing (3x14 rough sawn joists at 12” on center, (o.c.) and spanning 17’-6” at Area A and 2x11 ½” rough sawn joists at 16” o.c. and spanning 9’-6” in Area B) was found to be structurally adequate to support code-required loads for new construction and joist deflection was determined to be within code allowances for new construction. It is therefore believed that the unevenness is primarily due to differential settlement of the foundation.

c. Most wood joists are believed to be supported directly by the brick via pockets or continuous ledgers. In some areas, (at former evidence room) joist end support at the foundation walls was observed to be via toe-nail attachment to 2x ledger (Figure 20).

12. Second floor framing observations: Areas A and B

a. Second floor framing in Area A was observed to be concealed by multiple layers of finishes, (Figure 21). Selective demolition was completed in order to expose the floor framing interface with exterior walls. Based on damage to exterior structure, (Figures 1 and 2 from the RFP and Figures 1, 2, 22, and 23 from this report) it was deemed necessary to view structure in this area. We observed that there was no positive attachment of second floor framing to the structure in this area, and up to 1 5/8” of horizontal movement of the wall away from the framing, (Figure 23). This movement constitutes an unsafe condition and the

City was notified of this finding on 3/29, the day following its discovery. The exterior walls on the east and west edges of the building are held to the framing by steel tie rod/plate assemblies, spaced apart at approximately 17 ft-20 ft, (Figure 24). This system in combination with an unreinforced masonry wall system is deficient, but at least there is something in place which is intended for holding the walls and floor system together. No plate/rod assemblies or other effective means, (friction between underside of joist and top of brick shelf are not permitted by code) were observed to be in place either in this wall, the adjacent vestibule area to the south, or the north wall of Area ‘A’, (Figures 25 and 26). Though the framing at the north wall at Area ‘A’ did not exhibit movement of the magnitude which was observed at the restroom/vestibule area.

b. From observations of the underside of the second floor, it initially appeared that the second floor framing had undergone excessive deflection or was impacted by differential settlement. This is likely the case to an extent but some of the appearance of deflection was due to variations in the gap between suspended ceiling and existing hard ceiling above which were needed in order to accommodate sprinkler piping.

c. An existing wall in the vicinity of the damage depicted in Figure 3 of the RFP, was observed to have undergone significant damage, (Figures 1, 2, and 27 of this report). It appeared that this was at least in part caused by installation of a penetration in the wall for piping. This constitutes an unsafe condition which should be corrected.

d. A walkthrough of the second floor of Area B was completed. No cracked or discolored finishes were observed which would serve as indicators of structural damage. However, upon review of plan information some issues with the attachment of structure to the exterior wall were observed, specifically that the in many cases the connection between the floor deck and the exterior wall was not direct, and the load ‘path’, that is, the sequence of structural elements and connections between the wall and the floor, did not appear to properly address transfer of forces into the deck and should be reviewed/analyzed further. Such analysis is beyond the scope of this study. The aforementioned force transfer is necessary in order to properly facilitate load transfer to vertical lateral load resisting elements, (ie. shear walls, moment frames).

13. Third and fourth floor observations, Area B:

a. A walkthrough of the third and floors of Area B were completed. No cracked or discolored finishes were not observed which would serve as indicators of structural damage. Similar issues to 12.d above were noted at these levels, upon review of the plans.

14. Roof observations, Areas A and B:

a. There are significant differences between the roof configurations of Areas A and

B. As noted previously, the Area A roof is supported by open web steel joists topped with wood decking and the Area B roof is supported by cold formed metal joists topped with cold formed metal decking. Additionally, the Area A roof material was observed to be an adhered membrane system while the Area

B roof was observed to be a ballasted system.

b. The attachment of the open web steel joists and roof decking to the exterior walls could not be observed but in assuming similar construction to the second floor of Area A it is likely deficient and should be analyzed.

c. Standing water was observed on the roof of Area A, (Figure 28). Some water infiltration was observed inside of the building, near the north edge of Area A.

Some of the roof drains were observed to have been partially obstructed with debris.

d. Per discussions with you, it is understood that structural engineering work was not completed as part of the rooftop solar array project. Such work would typically include an evaluation/load rating of the roof framing for support of new loads from solar equipment, calculations to design the array structure itself, and calculations to determine ballast requirements. It was observed that there was no positive attachment of the arrays to the structure below, and in some areas the array support pads appeared to be compressing the roof membrane, which over time could cause a penetration in the membrane.

Conclusions and Recommendations:

1. The movement of the brick at the second floor of the restroom area, (Figures 1 and 2 from the RFP) constitutes an unsafe condition and should be addressed as soon as possible. Possible solutions for this condition include implementation of a new, (wood or cold formed metal) stud bearing wall system and foundation placed inboard of the existing brick bearing wall and foundation system. This solution could serve multiple functions, including:

a. Support for gravity framing, (ie. joists).

b. Provide solid structure for anchorage/attachment of brick wall. Could use many fasteners spread out over a large area, such as the Helifix system by MasonPro, Inc. for attachment and lateral support of brick.

c. Could be augmented with sheathing and/or strapping to provide additional shear wall/lateral resistance.

The above listed improvements could possibly be carried throughout Area A as part of seismic/lateral upgrades described later in this section.

2. We recommend that the City complete its study of the underground water conduit beneath the building for undermining of soil beneath the building and proper flow of water through the pipe and take appropriate corrective measures. However, we feel that the primary issues with the building are related to the superstructure.

3. The structure is built on poor soils and has undergone some settlement. For the Area A structure, the current loads being placed onto the soils are likely less than the loads from the original, taller structure. From a settlement standpoint, this means that future additional settlement would be relatively minor unless loads on the foundation are somehow increased. It is likely that the implementation of a heavier floor system in

Area B in 1983 caused some of the observed settlement in that area. Now approaching

35 years after construction, additional settlement would be anticipated to be relatively minor, unless loads on the foundation are increased.

4. Area A has non-existent or deficient means of support for resistance of lateral, (wind, earthquake) loads. Area B has means of support for resistance of said loads which are likely deficient, (12.d of ‘Observations and Assumptions’) relative to current building code requirements and should be analyzed and upgraded if needed. Both areas have deficiencies with regards to elements for support of in-plane shear. A structural analysis to determine the full extent of these deficiencies is beyond the scope of this report

Unreinforced masonry buildings with wood floor systems such as City Hall are considered among the most hazardous of building systems with regards to performance during an earthquake. The difference in stiffness, (flexible wood vs. brittle brick) between the unreinforced masonry and wood floor and roof deck at Area A serve to amplify the force that a building would experience during an earthquake as compared to stiffer floor and roof systems, (ie. concrete, metal deck), and thus offers poor capability for earthquake resistance. We recommend that another facility is selected for the

Emergency Operation Center, (E.O.C.) until the issues identified in this report can be addresses.

5. The structure has deficient means of attachment of the wall to the floor and roof deck.

Aside from the immediate need to prevent the wall from falling down at the restroom area, this is important to address because the primary failure mode of this type of structural system, (see item 4 above) in an earthquake is detachment of wall structure from floor/roof structure and subsequent collapse of the wall and supported framing.

We recommend that, in addition to correcting the immediate issue of attachment of wall to floor and roof framing, Areas A and B of the structure undergo design of seismic upgrades. Seismic upgrades would likely include implementation of new elements to resist in plane shear, (ie. steel X-bracing, shear walls) along interior wall lines and around the perimeter stiffening of floor and roof diaphragm systems, (ie. addition of additional layers of floor and roof sheathing) and reinforcement of chords, (diaphragm perimeter elements placed under tension and compression) and related connections for transfer of these forces into the new X-bracing/shear walls. Some foundation work in should also be anticipated, particularly at the base of lateral force resisting elements.

Foundation underpinning may be needed in these areas if bearing capacity is found to be insufficient. As part of design of seismic upgrades, a geotechnical study per IBC 2009

Section 1803 should be completed. The existing wall systems could also be reinforced to better support out of plane wind loads. This could possibly be achieved by implementation of a cold-formed metal stud back-up framing system and attachment of this framing to the brick. Other aspects of the building may possibly be enhanced during this work, such as improvement of roof slope to the roof drains.

6. We recommend that repairs be completed to the foundation at the areas identified in item 10 of ‘Observations and Assumptions’ including:

a. Repointing brick masonry.

b. Replacement of adjustable jack posts with new posts and footings intended for long term-permanent use.

c. Reinforcement of cracked foundation walls noted in d and e of item 10. This could include injection grouting cracks or possibly placement of reinforced concrete coating adjacent to the damaged portions of walls.

d. Reconstruction of structure beneath the exit door on the west edge of the building with an improved structural steel and concrete elevated slab system that will be sealed against water infiltration.

7. Connections of wood floor joists to wood ledgers, (11.c of ‘Observations and

Assumptions’) should be reinforced. Steel framing angles such as those manufactured by Simpson Strong Tie could possibly be used for this.

8. Walls which have been damaged by installation of pipe penetrations should be repaired/reinforced. Possible reinforcement measures could include placement of load-bearing headers with jack studs above and adjacent to the wall penetration location, respectively. Damaged existing load-bearing brick could possibly be removed and replaced with beam and post assemblies.

9. We recommend that a review of the rooftop solar arrays is completed, to determine the adequacy of the module support structure, ballast, and capacity of the roof framing to support the loads imposed by this equipment, with reinforcement implemented as required.

10. Roof drains should be cleared of debris and improvements in roof slope should be implemented in order to prevent ponding.

Please feel free to contact me with any questions.

Sincerely, Miles Stetson, P.E. – Project Engineer

Figure 1 - Overall building plan with area designations. (Ref. Google Earth.)

Figure 2 - Partial view of Sheet A7 of 1982 Kenneth F Parry & Associates plans depicting areas of concern which were idendified in the RFP.

Figure 3 - Photograph of east elevation of Area 'A' ca. 1960's.

Figure 4 - Approximate location of brook beneath City Hall, Ref. Sheet A1 of 1982 Kenneth

Parry & Associates, Inc. Drawings.

Figure 5 - Partial view of boring log plan from 1983 geotechnical report by Soils Engineering, Inc. A 15 ft thick ‘soft’ layer of soil consisting of silt and clay was encountered approximately

50 ft below finish grade.

Figure 6 - Typical foundation wall. Rock wall w. joints filled with mortar, topped with several courses of brick, and some CMU present, (used as infill).

Figure 7 - Area B ground floor, Ref. Sheet S2 of 1982 Kenneth Parry & Associates, Inc.

Drawings.

Figure 8 - Cracking of brick at perimeter foundation wall at south edge of Area 'B'.

Figure 9 – Foundation wall - deterioration of mortar at brick and rock joints, foundation wall adjacent to stairwell – Area ‘B’.

Figure 10 – Deterioration of mortar at brick pier – Area ‘B’.

Figure 11 - Foundation deficiencies near west edge of building, Ref. Sheet S1 of S2 of 1982

Kenneth Parry & Associates, Inc. Drawings.

Figure 12 - Cracking of interior foundation wall near west edge of buidling.

Figure 13 – Observed Movement between brick wall and floor and glass door system at exit door on west edge of building (Ref. Figure 3 from RFP). Note compromised joint sealant at walkway.

Figure 14 - View of condition noted in Figure 13, from basement level, (looking north).

Figure 15 - View of condition noted in Figure 13 after removal of finishes, (looking south).

Note severe corrosion of steel beam at ceiling level and damage to brick foundation wall near pipe penetrations. Corrosion of steel is presumed to be caused by compromised joint sealant above, (Ref. Figure 13).

Figure 16 - Photograph of exit door, looking north. Note no movement observed at the ramp, which is indicative of observed movement of the building/foundation itself likely taking place during construction of the exterior ramp system.

Figure 17 - Telescopic adjustable column observed near east edge of building - not permitted for permanent use.

Figure 18 – Area A floor drain, believed to tie into conduit beneath building, (Ref. Figure 4).

We were informed that water flows out of the drain on occasion.

Figure 19 - Moisture damage to floor joists along the south edge of Area 'B'.

Figure 20 – Moisture damage and toe-nail ledger attachment of ends of first floor joists at

Area 'A' beneath evidence room.

Figure 21 - Area 'A' second floor structure concealed by multiple layers of finishes.

Figure 22 – Close-up of damage to exterior brick wall at second floor Area ‘A’, (restroom) with apparent movement having been observed by the City over time.

Figure 23 - Measurement of apparent movement at underside of end of second floor joist beneath restroom, with apparent 1/2"+/- relatively recent movement and 1 5/8" total movement. No positive attachment of framing at the second floor level to the brick wall was observed.

Figure 24 - Steel tie rod/plate assemblies at 17ft.-20ft. o.c. spacing. Rods are assumed to extend through the width of the building, (Area 'A') in the east-west direction. These assemblies were not observed in the area where the most movement was observed, (Figures

22-23). No rods were observed in the north-south direction.

Figure 25 - Second floor joist bearing condition at Area 'A' north exterior wall. Note no positive attachment of joist end to brick/masonry was observed. Also, minimal signs of movement were observed.

Figure 26 – Cracking of finishes at north edge of vestibule, Area ‘A’.

Figure 27 – Severe cracking of wall supporting Area ‘A’ second floor framing. Likely cause is installation of piping penetrations through the unreinforced brick masonry.

Figure 28 - Standing water observed on Area 'A' roof.

Figure 29 - Rooftop solar arrays with ballast.

Figure 30 - Solar array support pad compressing roof membrane below.