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Statue of Liberty and Pedestal
Liberty's torch rises 305 feet above New York Harbor and was once the tallest structure in New York City.
The Statue of Liberty is probably the best known monument in the world and is a global symbol of freedom and democracy. Dedicated in New York City on October 28, 1886, the colossal copper-clad statue stands on Liberty Island (formerly Bedloe's Island) in New York Harbor alongside Ellis Island, the former point of entry to the United States for twelve million immigrants between 1892 and 1954. Many foreigners arriving by steamships from Europe were greeted by the sight of the Statue of Liberty as one of their first views of America after the two-week long voyage across the Atlantic Ocean.

The statue is 151 feet (46 m) tall and rises above a pedestal which in turns sits atop the star-shaped rampart of Fort Wood, one of the early defenses of New York Harbor. In total, the top of the torch rises 305 feet (93 m) above the ground. The Statue of Liberty was once the tallest manmade structure in New York City (and the United States), surpassing the towers of the Brooklyn Bridge and the steeple of Trinity Church in Lower Manhattan. When the Statue of Liberty briefly functioned as a lighthouse from 1886 to 1902, its torch could be seen as far as 24 miles (39 km) away at sea. During that period, the torch was illuminated by nine Wood arc lamps powered by an on-site generator, making it the first lighthouse in the United States to use electricity.

The Statue of Liberty was a gift from the people of France to mark the centennial of the signing of the Declaration of Independence and the alliance formed between the two countries during the American Revolutionary War. The idea of erecting a statue at the entrance to New York Harbor to commemorate Franco-American friendship was inspired by French scholar Édouard René de Laboulaye and created by French sculptor Frédéric-Auguste Bartholdi (who also designed the Marquis de Lafayette Statue in Union Square). While visiting the United States in 1871, Bartholdi selected Bedloe's Island in New York Harbor as the preferred site for a statue depicting the "Goddess of Liberty". The statue was originally intended to be presented to the United States for its centennial on July 4, 1876 but achievement of this goal was prevented by the political climate in France and a delayed start in raising funds to pay for the statue.

Statue of Liberty Tablet
Lady Liberty's copper skin was hand hammered using the repoussé technique and is supported by an iron framework designed by Gusteve Eiffel.

Officially named Liberty Enlightening the World, the Statue of Liberty depicts a woman wearing a stola—similar to the Roman goddess Libertas—that is holding up a flaming torch to embody enlightenment. Lady Liberty's other hand embraces a tablet inscribed with the date of American independence, July 4, 1776 (in Roman numerals), which is symbolic of a nation governed by law. The spikes of her diadem stand for the seven seas and continents and the 25 windows around her crown represent the gemstones found on the earth. An important feature that cannot be seen by visitors is the broken shackle and chain at the statue's feet, symbolizing America's freedom from oppression and tyranny. Bartholdi's design for the Statue of Liberty was remarkably similar to his earlier attempt to construct a colossal statue of a torch-bearing woman at the northern entrance to the Suez Canal, which Egyptian ruler Isma'il Pasha never commissioned due to financial issues.

The Statue of Liberty was fabricated in the workshop of Gadget, Gauhier, & Cie on the Rue de Chazelles in Paris and was erected in the company's courtyard, rising above the rooftops of all the buildings in the surrounding neighborhood. The hand and torch were temporarily exhibited at the Philadelphia Centennial in 1876 and then in New York City's Madison Square Park from February 1877 to June 1882, helping to raise funds for the construction of the pedestal. Meanwhile, the head and crown were displayed at the Paris Exhibition in 1878. The statue was completely assembled in Paris beginning in 1883 and was later disassembled into 350 individual pieces and packed in 214 crates so it could be shipped across the Atlantic Ocean. The statue was carried aboard the French frigate Isère, which departed from Rouen, France on May 21, 1885 and arrived in New York Harbor on June 17, 1885.

Bartholdi chose the repoussé technique of metalworking that involved hand-hammering 332-inch (2.4 mm) thick heated copper sheets into negative wooden molds. Before creating the wooden molds, positive plaster molds of the statue were built in increasing scale by taking measurements at numerous reference points. The finished copper sheets were riveted together and then hung to a framework of iron armatures. The repoussé method allowed for more artistic opportunities and permitted a lighter statue, allowing it to be transported to America. A total of 62,000 pounds (28,100 kg) of copper was used to build the Statue of Liberty, which was shaped using 300 different types of hammers.

Statue of Liberty at Night
The Statue of Liberty functioned as a lighthouse from 1886 to 1902 and was the first in America to use electricity.

To design the support the massive structure, Bartholdi employed the assistance of French architect Eugene Viollet-le-Duc, however Viollet-le-Duc died in 1879 having only completed plans to support the torch and head. Alexandre-Gusteve Eiffel, the most famous French engineer of the time, was then engaged to design the internal framework. Eiffel is known for his design of several important railway bridges in Europe, and later for the Eiffel Tower in Paris, constructed for the World's Fair of 1889. Also a pioneer in the study of wind effects on structures, Eiffel's hand calculations on wind loads for the statue still remain accurate to this day despite advances in technology. The 250,000 pounds (113,400 kg) of iron framework inside the statue supports the entire copper skin and was designed for wind loadings, differential expansion and contraction of iron and copper, and electrolysis effects.

The financing, design, and construction of the pedestal were the responsibility of the United States. Construction of the foundation and pedestal fell under the supervision of General Charles P. Stone, an American civil engineer and a graduate of the U.S. Military Academy at West Point. Excavations for the foundations began on May 11, 1883 in the center of Fort Wood, a star-shaped fort that was completed on Bedloe's Island in 1811. A total of 27,000 tons (24,500 t) of concrete were poured to build the 65-foot (20 m) tall foundation, which was completed on May 17, 1884. Meanwhile, assembly of the Statue of Liberty in France was completed the following month and Minister to France Levi P. Morton formally accepted the statue in Paris on behalf of the United States at a ceremony on July 4, 1884.

Richard Morris Hunt, an eminent American architect of the time (the distinction between architect and engineer was less pronounced than it is now) served as the designer of the pedestal. The first American to attend the École des Beaux-Arts in Paris, Hunt also designed the façade and Great Hall of the Metropolitan Museum of Art in New York City and the Biltmore Estate near Asheville, North Carolina. The statue's pedestal was faced with 13 layers of brick from Leete's Island, Connecticut, symbolizing the original colonies. Ten circular stones were placed along the bottom of each side of the pedestal and were originally intended to carry the shields of each state and territory in the union at the time, as well as the District of Columbia.

The cornerstone of the pedestal was laid on August 5, 1884. Two sets of four iron girders were placed inside the 89-foot (27 m) high pedestal and later bolted to the statue's framework, making the statue an integral part of the pedestal. Construction of the pedestal was temporarily suspended for a five-month period in 1885 due to a lack of funds but a campaign launched by Joseph Pulitzer, publisher of The World newspaper, raised the money needed to complete it. Instead of relying on failed attempts to obtain donations from millionaires, Pulitzer reached out to the common people including recent immigrants and school children and was able to collect enough donations to complete the pedestal over a 21 week period. The capstone for the pedestal was finally set into place on April 22, 1886.

Statue of Liberty and Fort Wood
The massive granite and concrete pedestal was built inside the star-shaped walls of Fort Wood and was one of the heaviest pieces of masonry ever built.

Once the pedestal was complete, the crates transported by the Isère were unpacked and the statue was reassembled during the summer and early fall. A dedication ceremony was held on October 28, 1886 and despite the rainy weather, a million spectators came to watch a parade of 20,000 uniformed men march along Fifth Avenue and Broadway, from just below Central Park to the Battery. During the ceremony on Bedloe's Island, Bartholdi climbed up to the statue's head and cut a rope which removed large French flag draped over the statue to unveil its face. This was met with whistles from the hundreds of vessels in the harbor and a gun salute from the battleship USS Tennessee. President Grover Cleveland gave a brief speech and formally accepted the gift from the people of the France. Liberty's torch was first lit on November 1, 1886 and was celebrated with a fireworks display.

In 1981, after the statue had weathered the effects of nearly a century of wind, salt air, rain, and pollution, a team of a team of French architects and engineers—working in cooperation with the National Park Service—set out to assess the condition of the statue and determine what type of repairs may be needed. After learning that significant repairs would be required, the Statue of Liberty-Ellis Island Foundation was formed the following year to raise the money to restore the Statue of Liberty and Ellis Island for their upcoming centennials. Between 1984 and 1986, an extensive restoration of the Statue of Liberty was undertaken and the statue was encased with 300 tons (272 t) of aluminum scaffolding. At 250 feet (76 m) in height, it was the tallest freestanding scaffold in the world and was designed to resist winds of up to 100 mph (161 km/h).

Statue of Liberty Torch
The torch was replaced in 1985 during the statue's restoration and the new flame was plated in 24 carat gold leaf.

Liberty's torch had been plagued with leaks ever since it was modified in 1916 to install internal lighting. Gutzon Borglum, the sculptor of Mount Rushmore, had cut out most of the copper from the flame and installed 250 tinted yellow glass panes. The torch was deemed beyond repair and was hoisted off the statue on July 4, 1984. A team of ten French metalworkers constructed a new torch on Liberty Island using the same techniques and tools as Bartholdi. Old photos and measurements taken from the original were used as a reference so the new torch would remain consistent the original design, except that the copper flame was plated in 24 carat gold leaf (in 1893 Bartholdi had suggested gilding the statue when he was disappointed by its lighting). The new torch was raised into place on November 25, 1985 and the original torch was placed on display for visitors in the lobby of the museum in the pedestal.

ASCE funded the development of a complete set of three-dimensional computer aided design (CAD)-generated construction drawings of the Statue of Liberty, which were donated to the National Park Service and incorporated into exhibits in the museum located in the pedestal. Most of the original drawings of the statue had been destroyed in a fire in Paris at the turn of the century. ASCE's efforts to document the civil engineering aspects of the restoration effort and create electronic drawings that could predict the dynamic response of the structure using finite element analysis were led by Dr. John Tesoro, a structural engineer at the firm of Burns & Roe. Dr. Tesoro was also assigned by ASCE to serve as a consultant to the National Park Service during the restoration process.

Dynamic and fatigue analyses were performed on the statue's structural framework to evaluate the stresses and determine its remaining life. The most critical problem was found in Liberty's right shoulder. Inside the statue, a 97-foot (30 m) tall central pylon consisting of four girders with horizontal and diagonal cross bracing supports the secondary framework and armature, as well as a 40-foot (12 m) long extension that supports the raised arm and torch. The CAD drawings revealed that the head and shoulder were misaligned during the original construction; the arm was moved 18 inches (46 cm) away from where Eiffel had designed it to join the central pylon and the head was two feet (61 cm) off center.

A team of American and French architects and engineers came up with two solutions to correct the structural stability in the statue's shoulder: one option to completely rebuild the connection based on Eiffel's original plans and transfer the weight directly to the central pylon (reducing stresses), and a second option to strengthen the existing connection by adding new diagonal bracing and steel plates (further reinforcing repairs that had been made to the connection in 1932). Using the computer models, finite element analysis showed that both solutions would work so the second option was selected because preservation, not replacement, was the ultimate goal of the historic restoration project. Additional supports were added inside the head to improve its stability and address the alignment issues.

Statue of Liberty Restoration
ASCE was involved in the the restoration of the Statue of Liberty from 1984-1986 and donated a set of CAD drawings to the National Park Service.

Galvanic corrosion between the statue's copper skin and puddled iron armature bars led to some bars losing half of their original thickness while rust on others caused them to stick in the copper saddles attached to the skin, eliminating their ability to slide and provide flexibility during wind loadings and changes in temperature. Although Eiffel had used asbestos dipped in pitch as an insulator to protect against the effects of electrolysis, the material had worn away. Each of the 1,350 iron armature bars were replaced with stainless steel members and insulated with Teflon tape to prevent galvanic corrosion. Only four bars could be removed from each side of the statue at any one time, so each day a total of eight bars were removed and copies were made in a metalworking shop and returned to the statue the following day. Additionally, all of the flat bars connecting the armature bars to the secondary structural framework were replaced.

Over the years, coal tar and seven layers of paint had been applied to the interior of the copper skin by maintenance workers hoping to prevent leaks; however this process in reality trapped water in certain locations and also hid corroded areas. Liquid nitrogen at -350°F (-212°C) was sprayed to freeze and remove the paint layers while special techniques were developed to remove the interior coal tar coatings without damaging the copper skin of the statue by blasting with sodium bicarbonate powder. Meanwhile, corroded sections of copper skin on the exterior of the statue were replaced and leaks were patched and caulked. A new double deck, glass-enclosed passenger elevator was installed in the pedestal, and at 97 feet (30 m) in height it was one of the tallest hydraulic elevators in the world. New platforms were added on the spiral staircase leading up to the crown and a ventilation system was installed to provide tempered fresh air to visitors climbing up the 168 steps to the observation windows in the head.

On September 9, 1987, the Metropolitan and New Jersey Sections served as joint hosts for the dedication of the Restoration of the Statue of Liberty as the 1987 ASCE Outstanding Civil Engineering Achievement award. Over 100 people attended the dedication ceremony, which was followed by a tour of the national monument and a luncheon on Governor's Island. ASCE President Dan Barge presided over the dedication ceremony at the statue.

ASCE Outstanding Civil Achievement Award
Dan Barge, Mike Skelly, Jim O'Brien, and Ed Cohen display the 1987 ASCE OCEA Award at a ceremony held at the Statue of Liberty on September 9, 1987.

The Statue of Liberty was designated as an International Historic Civil Engineering Landmark by ASCE and the Société des Ingénieurs et Scientifiques de France in 1985. A plaque marking the designation was dedicated by the two societies on October 24, 1986 and is located at the base of the pedestal. The statue was also designated as a National Monument in 1924, listed on the National Register of Historic Places in 1966, designated as a New York City Landmark in 1976, and listed as a World Heritage Site by the United Nations in 1984.

While a largely symbolic structure, the design and construction of the Statue of Liberty involved many unique engineering challenges. The iron framework supporting the copper skin was an early example of curtain wall construction, a method of construction copied in 1885 for the first skyscraper, and still in use today. By designing the thin copper skin to "float" over framework, it permitted thermal expansion and contraction to take place without inducing excessive stresses. The massive granite and concrete pedestal was one of the heaviest pieces of masonry ever built. Its construction stimulated the use of concrete as a building material for many structures in the United States.