Exterior Conditions Investigation at the Fire Island LIghthouse

March 22, 2016

The week of October 5, 2015 was a busy one at the Fire Island Lighthouse on the Great South Bay of Long Island, NY.  In addition to several 4th grade school groups climbing the 192 steps to reach the top of the lighthouse each day, a team of consultants working with the National Park Service and Fire Island Lighthouse Preservation Society were on site to perform an investigation of the exterior. The team led by John G. Waite Associates, Architects with Old Structures, Atkinson-Noland & Associates, and Vertical Access was tasked with assessing the exterior concrete coating of the lighthouse.

The current Fire Island Lighthouse was built in 1858 to replace an 1826 lighthouse on a nearby site. At 168 feet in height, it was twice as tall as the previous structure, and its Fresnel light was visible for at least 21 miles. The lighthouse is circular in plan, with load-bearing brick walls tapering from about 11 feet thick at the base to about 2 1/2 feet near the top. The lighthouse was decommissioned in 1974 and management of the structure was transferred from the U.S. Coast Guard to the National Park Service in 1979 when it became part of Fire Island National Seashore. A major restoration in 1985 removed and replaced the exterior concrete coating over the structural brick. The lighthouse is operated by the Fire Island Lighthouse Preservation Society.

As part of the field work performed over three days under perfect weather conditions, Vertical Access performed a hands-on investigation of the exterior of the lighthouse, documenting the conditions and sounding the concrete coating with acrylic mallets to help in the assessment of its condition. During the site work, team members from the National Park Service and JGWA participated in a live-feed video discussion with Vertical Access. While Vertical Access partner Kelly Streeter, P.E. performed a drop from the balcony level of the lighthouse to the ground, the rest of the participants could view on a nearby monitor the conditions as Kelly described them and ask questions to facilitate an understanding of the observations.

As part of the investigation, VA also took core samples for testing by others, performed borescope probes to better understand the condition of the concrete coating as well as the underlying brick masonry,

Fire Island Thermography01

Infrared thermographic images were used to identify moisture and underlying metal elements.

and took infrared thermographic images to identify moisture and underlying metal elements. During the same week, Shan Wo of Atkinson-Noland was on site performing ground penetrating radar (GPR) and other instrumental investigations as part of the non-destructive evaluation of the lighthouse. VA assisted ANA with full-height GPR scans at the exterior of the lighthouse. The information collected on site by Vertical Access and others is now being analyzed by the project team as part of the assessment of the Fire Island Lighthouse.

Learn more

Follow the Fire Island Lighthouse on Facebook

Visit the Lighthouse and National Seashore

 


Who is Buried in Grant’s Tomb? *

January 30, 2014
Grant’s Tomb is off the beaten track tread by most visitors to Manhattan. Photo credit: www.timeshutter.com

Grant’s Tomb is off the beaten track tread by most visitors to Manhattan.
Photo source: http://www.timeshutter.com

Once one of the most popular attractions in New York City, today Grant’s Tomb is off the beaten track tread by most visitors to Manhattan.  Constructed with the assistance of donations from 90,000 people totaling $600,000, the most money raised for a public monument at the time, the structure later suffered from neglect and fell into decline.[1]  Although it stands on a prominent point of Riverside Park overlooking the Hudson River, Grant’s Tomb is hidden in plain sight, with relatively few people venturing inside the mausoleum that contains the remains of President Ulysses S. Grant and his wife, Julia Dent Grant. 

 

 Grant’s Tomb was constructed between 1891 and 1897. Photo source: xxxx

Grant’s Tomb was constructed between 1891 and 1897. Photo source: National Park Service

Grant’s Tomb was designed by New York architect John H. Duncan and constructed between 1891 and 1897.  The exterior is based on the Mausoleum of Halicarnassus and the interior is modeled after the Tomb of Napoleon at Les Invalides in Paris.  On the exterior, the structure consists of a square base surmounted by a conical dome with a tall, colonnaded drum level, all faced with granite.  The main entry on the south side of the structure is distinguished by a wide plaza with steps leading up to a portico covering monumental bronze doors.  The ground floor has a large oculus through which the sarcophagi on the floor below can be seen.  Polished marble from Massachusetts is used for the interior floor surfaces and the railings, trim and dados at the walls of the ground floor and basement are clad with Italian marble.  The upper areas of the interior, including four barrel vaults facing the cardinal directions of the base of the monument, the pendentives where the square base transitions to the dome, the gallery at the drum level and the coffered ceiling at the interior dome, are faced with ornamental cast plaster.

The Grant Monument Association operated Grant’s Tomb until 1959, at which time the National Park Service took over management control and the site was designated as General Grant National Memorial.  From the 1970s to the early 1990s, visitors who ventured to Grant’s Tomb would find the granite walls of the monument covered with graffiti, the glass in the windows broken and the site in an overall state of disrepair.  Finally, faced with public criticism and a threat from the Illinois state legislature to move the remains of the Grants to their state, the federal government undertook much-needed repairs.  Following the restoration effort, the monument was re-dedicated on April 27, 1997.

Hands-on investigation of the plaster pilasters. Photo by Vertical Access.

Hands-on investigation of the plaster pilasters. Photo by Vertical Access.

As part of a site inspection of the General Grant National Memorial performed in 2012, National Park Service staff identified areas of cracking at the interior plaster at the drum level of the rotunda.  Some of the plaster at the pilasters at this area appeared detached.  The National Park Service requested the services of Vertical Access to perform a hands-on investigation of the plaster pilasters to better understand the causes of the cracks and determine whether the current condition presented an immediate public safety hazard.

As part of the investigation of the interior plaster, Vertical Access utilized several non-destructive and diagnostic tools.  As a first step, VA laid out the location of rigging holes in the coffered ceiling for the industrial rope access approach.  To locate the first rigging hole at the ceiling, a self-leveling laser level positioned on the ground floor was first used to establish the plumb line for the drop ropes in front of one of the pilasters.  To confirm which coffer was in line with the center of the pilaster when viewed from the attic side of the ceiling, the unfinished attic side of the coffer was warmed with a heat gun and the finished interior side was viewed with an infrared camera from the ground level.

 Conditions were documented using annotated drawings, still photography and video. Photo by Vertical Access.

Conditions were documented using annotated drawings, still photography and video. Photo by Vertical Access.

Once drop ropes were in place, Vertical Access technicians performed the hands-on investigation of the plaster pilasters, using diagnostic tools to better understand the construction of the pilasters and further investigate conditions of deterioration observed at the face of the pilasters.  A wall tie locator and rigid tube borescopes with a 0° (straight ahead) and 90° (right angle) direction of view as well as a 36”-long flexible tube borescope were employed during the investigation.  A video camera attached to the borescope unit provided recorded documentation of the subsurface conditions.  The cast plaster sections of the pilasters appear to be attached to the brick back-up structure with wood blocking.  Metal elements including wire ties and nails appear to have been used but no evidence of straps or anchors into the plaster was found.

 Conditions identified during the hands-on and close visual examination of the interior plaster were documented using annotated drawings, still photography and video.  At the conclusion of the investigation, Vertical Access installed crack monitors at two different pilasters.  Although the condition of the interior plaster does not represent an immediate threat to public safety, the crack monitors will be used to help determine whether the cracks observed are active.


* From Groucho Marx in the game show “You Bet Your Life”.  The correct answer is no one, since Ulysses S. Grant and his wife Julia are entombed but not buried in the memorial.

[1] Keister, Douglas.  Stories in Stone New York: A Field Guide to New York City Area Cemeteries & their Residents: Layton, UT: Gibbs Smith, 2011.  Page 142.


Ultrasonic Investigation for the Characterization and Evaluation of Guastavino Tile Vaults: A Pilot Study

December 10, 2012

The third biennial meeting of The Construction History Society of America was held at Massachusetts Institute of Technology in Cambridge MA November 2-3, 2012. This scholarly forum is a venue for professionals from a wide range of construction related disciplines to come together to exchange ideas and research findings about their passions for design, engineering, and preservation.

This year, in conjunction with the opening of the exhibit, Palaces for the People: Guastavino and America’s Great Public Spaces at Boston Public Library, all of Saturday’s agenda was devoted to the exploration of  topics pertaining to his work.

VA’s presentation, Evaluation of In-Service Tile Vaults, was based on findings from a pilot study performed on a mockup of a Guastavino vault with simulated faults, such as voids and delaminations, built into the vault as it was being constructed.  The abstract and full report are included below.

ABSTRACT

Presentation by Kelly Streeter, P.E. and Kent Diebolt
3rd Biennial Meeting of the Construction History Society of  America
Cambridge, MA | November 3, 2012

In response to aging infrastructure in the United States, nondestructive evaluation (NDE) is increasingly used as a monitoring tool, a method of investigation and in a quality control capacity.  The adaptation of existing NDE techniques to the evaluation of historic architectural and structural materials provides great potential for increasing the information available to professionals evaluating historic structures.

Guastavino ceiling tiles on the south arcade of the Manhattan Municipal Building

Guastavino ceiling tiles on the south arcade of the Manhattan Municipal Building

The process of addressing the significant public safety concerns of aging tile assemblies, such as Guastavino tile vaults, can be complicated by the difficulty of access – the undersides of the tiles often soar over heavily-used public spaces commonly filled with pews and other structures which make temporary scaffolding problematic.  The proposed sounding method examines the feasibility of evaluating Guastavino tile vaults from the top, which would allow architects and engineers to evaluate the vaults from the often easily-accessible attic spaces, thereby reducing the need for expensive and disruptive scaffolding systems for evaluation.  This could also facilitate more frequent periodic inspections.

Engineers evaluating the structural condition of existing tile vaults often need to determine construction details, including combined wythe and mortar bed thicknesses, in order to model vaults.  Hammer sounding is frequently employed to qualitatively evaluate the condition of the soffit layer of Guastavino tile.  The ultimate goal of this research path and the basis of this pilot study on the ultrasonic investigation of Guastavino tile vaults was the removal of the aural subjectivity inherent in hammersounding by the quantification of this same phenomenon: the differing acoustic quality of delaminated and bonded tiles.  By capturing and quantifying the impact response of steel hammer taps with an ultrasonic transducer and data acquisition system, the raw signals can be analyzed in the frequency domain using modern computational methods in an effort to characterize vault construction and condition.

dottyarrowDownload the full report (PDF)


Building a Vault in the Style of Rafael Guastavino

August 9, 2012

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Kent Diebolt, founder of Vertical Access, recently spent two days in July working at the Massachusetts Institute of Technology (MIT) with John Ochsendorf, a group of his students and two masons from the International Masonry Institute (IMI), building a mock-up of a vault in the Guastavino style for the upcoming exhibition, Palaces for the People. Years since its first conception, John was recently successful in getting funding for a major exhibition that opens this fall at the Boston Public Library and will travel to the Museum of the City of New York and The National Building Museum in Washington, DC.

Our interest in the mock-up project was to construct portions of the vault with known faults (primarily delaminations between tile wythes). VA Partner Kelly Streeter has done some preliminary NDT testing using ultrasound to evaluate the structural integrity of multi-wythe tile vaults that has been promising. The MIT vault, constructed with known delaminations at varying depths will allow for more empirical testing of the technology. Kelly and Kent will be presenting the results of this ongoing research at the Construction History Society of America (CHSA) meeting at MIT this fall.

We’d like to say thank you to John for including us in this effort. It was another great learning experience and a pleasure to share in the group’s enthusiasm for the work.

Additional Information:

The Guastavino Project at the Massachusetts Institute of Technology

VA Research, The Guastavino Timeline 1842 – 1968


Documenting Movement Over Time

July 28, 2011

As part of our work investigating buildings and structures, Vertical Access documents existing conditions and collects data about a specific moment in time. In most of our surveys, when we collect information about condition quantities, such as crack width and amount of displacement, it is a snapshot of the current condition. In some cases, it is important to document changes over time. When this is the case, instrumental monitoring can be incorporated into the investigation.

Wire crack gauges installed at plaster ceiling and plaster truss

One type of instrumental monitoring employs electronic gauges that collect and record data in real time. An example of a project where electronic monitoring has been employed is Marble Collegiate Church in New York City. In 2009, a study was conducted of the roof system and plaster ceiling in the sanctuary of the church. The design team for the project was led by Helpern Architects and included Robert Silman Associates and Vertical Access. Following a survey of the ceiling and development of repair documents, RSA and VA worked together to design a monitoring program to record movement at representative areas of the plaster ceiling, masonry walls and wood roof trusses.

Vibra-Tech was engaged to implement the system, which included vibrating wire crack gauges at the ceiling, vibrating wire strain gauges at the roof trusses and temperature and relative humidity sensors. These crack gauges were installed in February 2011, several months before the planned start of the roof repair and plaster conservation work, to measure and report crack displacement of existing cracks in the sanctuary ceiling, strain on the steel tie rods of the existing roof truss system in the church attic, and temperature and relative humidity in both the attic and sanctuary. Data from the gauges is transmitted continuously to a data center in the church. The real time data is available to the project team on a web site. There are also automatic notifications via email or text messages to the project team when movement thresholds are exceeded.

Wire crack gauges installed at plaster ceiling

Another type of monitoring uses crack gauges that must be physically examined to record the data. This more traditional system of monitoring employs crack gauges with sliding plates installed on either side of a crack. One plate has a grid and the other has crosshairs so that any future movement at the crack can be compared to the initial reading. Typically, the crack gauges are affixed to masonry or the other substrate using epoxy. One of the drawbacks of this system of monitoring is that it relies on visually checking each monitor to know whether there has been any movement or not. However, in cases where the purpose of the monitoring is to document any change that may be associated with a known event, this is a reasonable protocol.


NDE on a Rope

June 15, 2011

by Kelly Streeter, PE

I joined Evan and Keith at the Confederation Building in Newfoundland in May to complete a nondestructive evaluation pilot project designed to challenge our conclusions from our hammer sounding study of the limestone units. While in some cases it may be easy to detect delaminations by hammer sounding alone, the variable installation details at the Confederation Building made it very difficult to confidently predict by ear whether or not a stone “sounded” delaminated.

Delaminated stone used for calibration - on the ground

By using ultrasonics we were able to evaluate the stone’s response to a hammer hit in both the time domain and the freqency domain.  As Evan mentioned in his post, we had the added advantage of easily-accessible, known-delaminated and known-sound units which had already been removed for the renovation of the building’s west wing.    Not only were these units easily accessible, we could clearly see the delaminations in some of these removed units.  We tested those first to calibrate our observations.  It was fairly easy to see the multiple reflections from the delaminated stones, marked with arrows in the plot below, as opposed to the one clear reflection from the sound stone.

We then plotted the power spectral density, or PSD of the recorded hammer hit.  The PSD allows us to convert the power of a signal, as measured over time, into the frequency domain, showing us clearly in numerically and visually (on a graph) what our ear is trying to parse out.  Using this method we can analyze the way the frequency content changes from one stone to another.

The calibration went very smoothly. We found that we could easily identify the differences in both the time and frequency domain plots between the sound and delaminated stone units. We took these observations to the wall to test two different areas on the tower.

And then came the hard part.

Completing Ultrasonic testing - on the wall

It was a challenge (to put it lightly) to manage the rope access equipment, the tablet computer and the hammer and receiving transducer and all of the associated cables.  I found myself wishing I had two more arms.

Another significant challenge was the weather. We had to battle the frequent, low-level mist and rain throughout our visit. I was attempting to get the data but not expose the electronics to excessive moisture.

In the end, it was an excellent and rare opportunity to apply different nondestructive evaluation theories derived for more modern structural materials like concrete and pavements, to dimension stone. We discovered that we could quite easily detect delaminations once we had calibrated the equipment to a known condition.


At the Edge of a Continent

May 20, 2011

Imagine what the Norse sailors who first settled the site now known as L’Anse aux Meadows in Newfoundland must have experienced traveling across the Atlantic Ocean 1,000 years ago; or what the English explorer John Cabot felt when he purportedly landed on Newfoundland at the end of the 15th century. These sailors, venturing west from northern Europe, found the edge of a new continent. While a four-hour delay on the outbound flight and a cancelled return flight are hardly hardships compared to what these early explorers suffered, they do make one realize that St. John’s, only three hours from New York City by airplane, is still an insular and isolated place.

Cape Spear Lighthouse, photo by Keith Luscinski

Following Cabot, explorers from other European countries landed on the shores of Newfoundland, and in 1583 Sir Humphrey Gilbert declared the island to be a colony of England. Although France was granted land rights to parts of Newfoundland in 1713, the island was effectively a British colony until 1907 when it acquired dominion status. Finally, a tightly contested referendum held in 1948 determined that Newfoundland, together with Labrador to the north, would become a province of Canada.

Quidi Vidi Lake, photograph by Keith Luscinski

The Confederation Building, constructed in 1959-60, was built to house the Newfoundland and Labrador House of Assembly as well as other government offices for the newly established province. The building consists of an eleven-story tower with three to five story wings on three sides of the tower. The exterior is mainly clad in brick, with St. Marc (Quebec) limestone used at the parapets and window surrounds.

Confederation Building with west wing under scaffold for renovation and Kelly at top of tower

Exterior renovations began in the fall of 2009 to address the deterioration of the window systems and masonry cladding. With work at the west wing ongoing, Vertical Access was retained by Erik Jokinen to assist with the investigation of the limestone on the tower. During three days of field work this week, Vertical Access technicians Keith Luscinski and Evan Kopelson performed a hands-on inspection of the upper areas of the tower, documenting masonry conditions and hammer sounding over 1,000 limestone units. Kelly Streeter joined Keith and Evan for two days on site to perform a pilot study on the use of acoustic emission as part of the investigation.

Evan with St. John's and Atlantic Ocean in the background

A key question in the study was how to identify blind delaminations that may not be visible on the exterior surface of the stone and are difficult to detect by traditional hammer sounding. As part of the pilot study, acoustic emission, a nondestructive techniques based on ultrasound, was applied to stone units previously removed from the west wing of the building. Both sound units and units with visible delaminations were tested in the pilot project setup. Following calibration of the testing procedures to the specific stone used on the Confederation Building and type of delamination encountered, Kelly performed ultrasonic testing at two areas of limestone at the top of the tower. Initial results are promising in being able to identify blind delaminations based on the frequency pattern of the acoustic emission. Also evident from the pilot study is the need for careful calibration to the specific conditions likely to be encountered.

Kelly performing ultrasound testing on south facade


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