L.A. County Museum of Art Contacts CAS DataLoggers
CAS DataLoggers has just provided the structural monitoring technology for the Los Angeles County Museum of Art (LACMA), which has begun work on their newest conservation project–the Watts Towers, a Los Angeles monument and a masterpiece of regional folk art. The Towers were named a National Historic Landmark in 1990, with the tallest structure reaching to a height of about 100 ft. LACMA’s webpage states, “Constructed between 1921 and 1954/55 by Italian immigrant Simon Rodia, the Watts Towers have become an iconic monument to the city. The collection of 17 structures, which Rodia himself called ‘Nuestro Pueblo’ (Our Town), were erected by hand and made of steel rods wrapped in wire mesh and coated with cement. Embedded into nearly every inch of the environment are shards of ceramics, bottles tiles, shells, and other scraps—often brought to Rodia by others in the neighborhood.” Simon Rodia left the area in 1955 and gave the property to his neighbor until the state of California later took ownership.
In October 2010 LACMA contracted with the city’s Dept. of Cultural Affairs to preserve the towers by conducting daily maintenance on the site and by revising the 1983 Conservation Handbook to develop a new preservation plan. Over the past 40 years, workers have attempted to patch the towers’ cracks, but the damage keeps reappearing. In order to effectively restore the Watts Towers, LACMA’s Conservation Dept. needs to see how these structures are actually functioning under several environmental influences.
Dr. Charlotte Eng works as part of LACMA’s Conservation Center and has helped to restore much of the Museum’s collection over several years. As a Conservation Scientist and a Doctor of Materials Sciences and Engineering, Dr. Eng specializes in identifying needed materials and repairs to many different types of artwork. Now she and the rest of the team are actively restoring and protecting one of LA’s most impressive and accessible art installations.
The LACMA team’s efforts are focusing on finding and monitoring the movement of cracks in the site’s cement covering and fissures. To do this, the Department needs to view this positional data to see where the fissures are opening and to what extent. The conservation team will then repair the cracks using a custom repair material consisting of elastomeric crack fillers and polymer amended mortars. This will ensure that the repaired areas move in accordance with the rest of the structure to preserve its overall integrity.
LACMA is also working with UCLA’s Department of Engineering to record a combination of structural response and environmental data that will show where the damage to the structure is originating, which will guide all future efforts. Macroscopic monitoring techniques have already been undertaken on the site and structure, including telephoto photography, radiography and the use of high-magnification spotting scopes. Dr. Eng explains, “The Towers have also been laser-scanned and analyzed with ground-penetrating radar sweeps to show us the ground’s stability.”
Additionally, the Watts Towers are affected by many other factors including the day’s heat, wind speed, seismic activity, and more. For example, tilt meters have confirmed that the top of the main tower moves slightly as the day progresses and begins moving back again in the evening. This produces slight movements causing stresses which crack the concrete and cause other deterioration such as loss of the Towers’ ornamentation. To combat this, the team has to continually monitor the movement of the Towers and their foundations.
LACMA’s project supervisor and Senior Conservation Scientist Dr. Frank Preusser has over 40 years’ experience working with prestigious sites including the Egyptian pyramids, the Getty Museum, and museum-based work around the world. He and the Department are now specifically searching for new damage and areas where the Towers are losing their ornamentation. This work requires a high-accuracy datalogger that can connect with the project’s specific type of potentiometers. With this in mind Dr. Eng contacted CAS DataLoggers to find a portable device allowing users a quick way to get the data: “As a guide, we looked at monitoring projects conducted by other institutions such as UCLA which have successfully used a similar setup.”
LACMA’s Conservation Department has installed a dataTaker DT80 Intelligent Universal Input Data Logger provided by CAS DataLoggers to help determine the Watts Towers’ structural condition. This smart system is performing all the continual monitoring of this phase of the project as the team takes readings by positioning the portable datalogger around the base of the central tower. Later the DT80 will be mounted to a support structure above ground level, depending on where the most cracks are found as a result of this inspection. Most of the cracks that workers are seeing have formed around the base of the towers where the bulk of the structure’s weight is, and the concrete and rebar are thinner near the top so they’re more flexible than the base and develop less cracks. The dataTaker will be installed relatively close to the ground and out of the way of visitors but still accessible by a short ladder.
The dataTaker’s removable screw terminals have ensured a secure physical installation, which is especially desirable in this outdoor setup. Meanwhile a plastic cover is enough to protect the DT80 from rain—dataTaker’s ruggedized construction means that users don’t otherwise have to worry about leaving the data logger outside in case LA’s usually-sunny weather turns nasty.
The team is currently using a pair of Firstmark Series 150 Subminiature Position Transducers to monitor the movement of the cracks, relocating the sensors around the base of the central tower’s structure to find which cracks are moving through trial and error. The team used an external power source to power the sensors. These transducers use a measuring cable affixed to an attached shaft and a wire spool which revolves around a spring. Once a new crack is found, each sensor’s cable measures its linear position to see how much and how quickly it’s opening and closing. The potentiometer cable moves along with the crack, rotating the spool and generating an electrical signal proportional to the cable’s linear extension or velocity. This way, the sensor translates a crack’s linear position into a variable resistance which the dataTaker reads and records using its universal analog inputs.
Users setup the dataTaker to take a reading from each sensor once every 15 minutes as suggested by CAS DataLoggers. Equipped with 5 to 15 universal analog sensor inputs, the stand-alone device records data in real time at an accurate 18-bit resolution. High-speed counter inputs, phase encoder inputs and a programmable serial sensor channel allow dataTaker data loggers to read data from most sensors and log resistance, bridges, strain gauges, digital signals, or nearly any value. Current readings are shown on the logger’s built-in display.
The DT80 datalogger stores up to 10 million data points in its user-defined memory so that users can log as much or as little as needed, having independent control of schedule size and mode. The logger’s flexible communications array includes a USB memory slot so users can simply pull their Flash drive from the datalogger’s USB port to quickly collect the data. Once a month, a team member climbs up a short ladder to pull out the Flash drive, puts it in a laptop to download the data, and replaces it.
Dr. Eng explains, “We’ve retrieved the data and now we’re checking it for evidence of any seismic disturbances, since earthquakes are frequent in this area. There are other influences that may result in extreme data, such as the ‘Santa Anas,’ the hot winds blowing in from the desert at 50 to 60 miles per hour, so we’re looking for those indications too.”
In addition, dataTaker’s dEX graphical interface software is built into the datalogger. This user friendly, Windows Explorer-style software comes pre-installed and enables quick setup and configuration, suitable for both novice and advanced users. The software runs and is configured directly from a web browser, so it can be accessed either locally or remotely over the Internet. Operators can use any of the logger’s built-in communications ports to view dEX, including USB.
The dataTaker and string potentiometers are well within the Conservation Department’s budget, the real advantage being that the measurements and software are packaged in a single system. Dr. Eng sums up why LACMA chose dataTaker for their application: “We had several needs for this phase of the project: our system had to be portable, it had to be small, and it had to last more than a week or two. This system runs on its own out there indefinitely, it’s easy for us to get the data, and its compact size and screw terminals make it easy to mount on the towers.”
She continued, “We looked at similar projects using data loggers, but they had large and heavy batteries or they had to be hardwired first. We knew we wanted something standalone that would save us all that work; the USB retrieval is very handy and can be done by anyone at any time. Someone just brings a laptop and collects the data that way.” From there, the data can be analyzed in detail from an office PC.
The team can easily put the versatile dataTaker to work in other projects, using its universal inputs to log other values. “We can also use it for our strain gauge sensors. The logger we currently use to take strain gauge data is much bigger, about 12 x 12 inches and 3 inches thick, so it will be much easier to just use the dataTaker for that application too.”
Throughout LACMA’s selection process, CAS DataLoggers Application Specialist Pat Picciano worked with Dr. Eng to give her a choice of systems and is always available to demonstrate the dataTaker’s software features. As the project continues, the team may expand the number of transducers they’re using, and the dataTaker can easily accommodate a higher channel count.
As conservator of the Watts Towers, LACMA’s ongoing restoration work with this new data collection technique is helping to revolutionize how art installations are restored and preserved. Thanks to the Conservation Department’s efforts, the near century-old Watts Towers will continue to amaze visitors to Los Angeles for decades to come. Pat Picciano remarks, “It’s really unbelievable that one man was able to build all this, and the Museum is certainly taking good care of the site. We look forward to seeing what the data reveals as their project finishes.”
Check out LACMA’s webpage on the Watts Towers conservation project at http://www.lacma.org/art/exhibition/watts-towers for more info.
Learn more about UCLA’s equipment site which is part of the Network for Earthquake Engineering Simulation (NEES) at http://nees.ucla.edu/.