|THE RIVERGATE||title page | contents | appendices | cd-book cover|
engineering, and construction
|I.||The Rivergate, A Phenomenal Work|
|II.||Building In Tension|
|III.||Twentieth-Century Urban Relationships, Rivergate, World Trade Center, Place de France|
|IV.||The Roof, A Radically New Reading Of An Ancient Form|
|V.||How The Roof Was Constructed|
|VI.||Significance Of The Rivergate|
I. The Rivergate, A Phenomenal Work
The Rivergate, the Port Of New Orleans Exhibition Center (constructed 1964-1968) was a sophisticated reinforced concrete structure of the Expressionist School in the same genre as Eero Saarinen's Dulles Airport (1963), TWA Terminal at the John F. Kennedy Airport (1962), and the David S. Ingalls Hockey Rink at Yale (1959); LeCorbusier's Ronchamp Chapel (1950-1954); Jorn Utzon's Sydney Opera House (1957-1965); and the shapely and daring designs of Oscar Niemeyer, Felix Candela, and Pier Luigi Nervi.
The Rivergate was a product of the post World War II New Orleans building boom. Political and economic factors fostered the concept of a new convention-exhibition facility. City administrators had an interest in revitalizing New Orleans' central business area. Conventions and trade shows were the sixth largest money producers in the United States (100 percent of the revenue generated stayed in the community). The Municipal Auditorium (dedicated 30 May 1930) had become obsolete for convention-exhibition purposes. Rapidly changing developments in communications and forms of travel called for fresh commercial responses, and Rivergate's history commenced in mid 1957 (Dixon 1966; Garth 1968; Herman 1968).
New Orleans, a leader in world trade among American port cities, has long expressed its participation in national and international trade through significant architecture, such as the historic riverfront French Market (1813-1823, remodeled in the 1930s, alterations and additions begun in 1973), the U.S. Customhouse (A.T. Wood, architect, constructed 1848-ca. 1880), and the Board of Trade (James Freret, architect, 1883). These buildings are and always have been surrounded by the offices of maritime lawyers, commodities traders, and shipping agents many of which are housed in nineteenth-century buildings designed for street-level commerce and upper-story offices and/or family residences. Surviving masonry warehouses reflect the heyday of cotton, sugar, tobacco, and bananas that moved through the Port of New Orleans. The architecture of nineteenth-century mercantilism lives on in New Orleans through direct use and adaptive reuse of these buildings.
In the revitalization scheme of the 1950s, one of the most prominent sites in downtown New Orleans, the intersection of the broad main thoroughfare Canal Street with the Mississippi River, was selected to erect what Richard R. Dixon called one of the nation's finest new convention-exhibition facilities (Dixon 1966). The Rivergate cost $25 million 1960 dollars. By 1994, this building was estimated to be worth $300 million (Curtis 1993-1994). The designated site, six city blocks, is bounded by Canal, Poydras, South Peters Streets, and Convention Center Boulevard. The Rivergate had pedestrian entrances on Canal and Poydras Streets and Convention Center Boulevard. The South Peters Street elevation was dedicated to entrance and exit openings for the two-level subsurface 800-automobile parking garage, a long loading dock with two access doors 20' x 20' to the first floor, and freight elevators.
Although the Rivergate was conceived and designed as a convention-exhibition facility, it was also used as the venue for Mardi Gras balls, high school graduations, and an important funeral -- the lying in state of Mahalia Jackson (1972), a native of New Orleans. The building was linked not only to the city's political and economic history but to the city's cultural history as well.
The architectural firm of Curtis and Davis, which the New York Times referred to as the spokesmen for modernity in the Crescent City, was selected to design a signature building for New Orleans (Forgeron 1968). Nathaniel Curtis was the partner in charge and design architect. Associate architects were Silverstein and Associates; and Favrot, Mathes and Bergman and Associates; consulting engineers were Skilling, Helle, Christensen and Robertson; the general contractor was C.H. Leavell and Co.
Ground breaking ceremonies on 4 December 1964 were followed by the driving of piles and a deep excavation to provide space for the parking garage, mechanical and electrical equipment, stairs and escalators to move people from subsurface levels up to the first floor, and a tunnel 60' x 750' ($1.3 million) which was designed and built to be a link in the controversial but never constructed riverfront expressway (Baumbach and Borah 1981).
The avant-garde Rivergate was an architectural and engineering study in reinforced concrete design and building technology. Enormous reinforced concrete columns and beams in the subsurface parking area supported the imposing above-grade structure as well as the first floor of the Rivergate's Main Hall which was designed to hold loads of 300 lbs. per sq. ft. Floor outlets (30' on center) contained such services to exhibitors as electricity, telephone, steam, compressed air, gas, and water (Dixon 1966); electrical power 20 amp single phase 120 volt to 100 amp three phase 480 volt; telephone lines; steam and steam return lines 110/125 psi; compressed air lines, 100 psi; gas lines, 7-inch water gauge; cold water lines, 50 psi; and 3-inch drains (n.n.a., n.d.). Garage areas were equipped with an automatic sprinkler system and storage spaces.
The most distinguishing feature of the Rivergate was the roof. The 95,500-sq. foot South Hall was covered by a swooping and sweeping dual curved roof. This reinforced concrete barrel-arched roof design was symbolic of the rolling Mississippi River which flows about 500 feet from the building (Dixon 1966). Engineering News Record referred to these "humpbacked" 1-1/2 catenary curve barrel arches 453 ft. long as having the profile of a whale (n.n.a. 1967b, 59-60). The Rivergate roof was perhaps the longest thin shell concrete roof span that had been constructed at that time. The 34,500-sq. foot North Hall, later called Penn Hall, in honor of its distinguished and successful manager, Herman Penn, was spanned by steel trusses 6' deep and covered with a flat roof.
From its earliest attempts architecture was essentially building in compression and consisted of laying bricks on top of bricks, marbles on top of marbles, and clay pots nested into each other. Whether the results were walls, posts-and-beams, columns and lintels, arches, or domes, the structural thrust was compressive and remained so for centuries. In the Rivergate the roof structure, tons of it, was essentially in tension, supported by miles of thin steel strands, post-tensioned. Even the columns, deliberately erected 2-1/2" off center and pulled into plumb by the post-tensioning process, can be said to be in tension. Tension structures, long familiar in bridges, are increasingly utilized in building construction, but nowhere had the techniques of tension building been utilized as in the Rivergate: a curved barrel vault system which rose from 30-foot high walls to a 59-foot ceiling over the 253' wide South Hall and then rose from 30' to 59' in the 139-foot riverside span (which covers convenience rooms, concourses, specialty rooms, and porte-cochere) with 30-foot overhangs and 7-foot upturned collars all around literally pushed tension building to the edge of its envelope. The overhangs and collars achieved architectural and engineering balance, and all elements served the whole.
Both South and North Halls were column free, divided only by ceiling-high folding doors. Together the halls produced 130,000 sq. ft. of continuous open space and seated 17,000 persons. South Hall alone accommodated 734 standard booths 10' x 10' and their required circulation spaces.
South and North Halls on their riverside was a two-story concourse which
extended some 400 ft. from the pedestrian entrance at 4 Canal Street to
the pedestrian entrance at 101 Poydras Street and opened on the riverside
to pedestrian entrances at 301 and 401 Convention Center Boulevard. Although
this 26-foot wide space accommodated vast crowds, it retained a human
scale. Natural light entered from the glazing in the ends of the roof
vaults and was transmitted to the first floor through four large plastered
ellipses cut into the second floor of the grand concourse. Well scaled
openings lined the long walls.
entrance No. 4 (on Convention Center Boulevard) lined up with the equestrienne statue of
Jeanne d'Arc, centerpiece of the Parc du France, a small urban space (Samuel Wilson Jr.,
architect, 1967) between the Rivergate and the World Trade Center (Edward Durell Stone,
architect in association with Robert Lee Hall, 1967). The gilded bronze Jeanne d'Arc
monument (Emmanuel Frémiet, French sculptor, nineteenth-century) was a gift from the
people of France to the people of New Orleans and was on axis with the lobby of the World
Trade Center. The massive horizontal Rivergate and the tall vertical cruciform World Trade
Center were linked together with the small bright gold historic monument to form the
twentieth-century architectural counterpart to the nineteenth-century Jackson Square in
the Vieux Carré a short distance down river.
Although there were five pedestrian entrances at or near grade, the most inviting access to the Rivergate was through 301 and 401 Convention Center Boulevard. Both openings were located under the protection of a 420-foot long porte-cochere which had a three-lane automotive drive-through and a 20-foot wide pedestrian apron -- all sheltered by the six 60-foot bays of the Rivergate's signature vaults plus 30-foot overhangs, sides and ends, and finished with 7-foot upturned collars in thin shell reinforced concrete. All pedestrian entrances to the Rivergate were protected by wide and deep concrete overhangs, the subtle way Nathaniel Curtis described in the New York Times to combat the strong sun and rain in New Orleans (Forgeron 1968).
The mammoth roof of the Rivergate was supported on twenty-one identical columns arrayed in three rows of seven columns each. Two rows of columns supported the undulating roof of South Hall with its 253-foot span. These columns were engaged in the wall structure, all finished in exposed aggregate, bush hammered concrete. South Hall was a vast column-free space, 253' wide and over 360' long. Abutting it on its river side was a 139-foot wide x six-bay space which sheltered an elegant concourse from Canal to Poydras Streets and a two-story structure which contained meeting rooms, stairways, cocktail and dining rooms, porte-cochere and pedestrian apron, and duct work. The porte-cochere with its six-bay portico recalled the classic treatment characteristic of much public American architecture. Glazed clerestories at the east and west openings of the vaults brought natural light to all parts of the structure.
were highly original elements. The base of each column began as a 4-foot
square, rotated 45-degrees so that it appeared diamond shaped, and tapered
in easy curves up to the point of bearing, 30' above grade, to a 2'-6"
square. The columns supported as much as 2 million pounds each.
The barrel shell-type roof, long familiar in form and engineering, differed from other thin shells in that it curved in both longitudinal and latitudinal directions. The extremely long spans produced high stress levels. The post-tensioned shells and the curved tendons introduced live loads on the shells. Post-tensioning, rather than pre-stressing, was chosen for the Rivergate's roof because the tendons could be easily curved to express the stress patterns of the members.
According to J.C. Pittard, construction superintendent for C.H. Leavell for the final fifteen months of the building of the Rivergate, post-tensioning was achieved by pulling wire and setting up forces in the concrete which were exactly opposite to those which the structure would experience when loaded. Therefore, when the loads were applied, an equilibrium was achieved. In the catenary curve the tendons were located at the bottom of mid-span and proportionately higher as the stress was decreased near the end (Pittard 1967). The tendons were 2-1/2" in diameter, and each tendon contained 40-1/4" steel wires, each wire capable of supporting 11,800 lbs. The tendons arrived on the job in flexible metal conduits 2-1/2" in diameter, some 270' long, and were embedded in the thin shell concrete in a catenary curve and in the valley beams from column to column. Each 60-foot wide bay in the main span section contained twenty tendons in addition to the rebars -- two layers of #4 (1/2" diameter steel) running both ways with a plastic-coated chair under the bottom layer. All of this was in a 5-1/2-inch thick concrete shell with 3/4" clearance minimum required top and bottom. This posed a problem in concrete placement and compaction on a form continuously curved in both directions. Arch frame and stiffener beams were provided at quarter points to stiffen and support the shells with respect to longitudinal buckling and to reduce the transverse moment. Horizontal post-tensioned ties were provided between the barrels at the high point of the roof in line with the transverse stiffeners. There were two 253-foot long, post-tensioned girders on each end of the building, 20' deep at mid-span (n.n.a. 1967a).
This design was computed on the basis of ASCE Manual 31 for straight cylindrical shells modified by the consideration of an additional longitudinal curve. The complete analysis was based on the beam method utilizing an IBM 1620 model 22 computer. No formulae existed for the 7-foot collar that edges the entire roof.
The structure was designed for dead load (its own weight), a live load of 30 lbs. per sq. ft. (induced by the use of the post-tensioned tendons), and a wind load of 45 lbs. per sq. ft.; a temperature variation of 50EF, and a shrinkage co-efficient of three ten-thousandths; reinforcing steel with a minimum yield strength of 60,000 lbs. per sq. in.; and a concrete compression strength of 4,000 lbs. per sq. in. The concrete was designed according to ACI Code 318-63 ultimate strength design method (Pittard 1967).
The roof shell form work was supported by 20 kip Patent Scaffold Shores: approximately 16,000 end frames were erected to complete the roof. With the use of 52-foot long timber trusses, a near maximum load was achieved on the scaffolding. The trusses, on 5-foot centers, were supported at mid-span directly off the shoring U-heads. This eliminated any need for continuous longitudinal beams. The heel sections of trusses rested on a base section 12' long x 7' high. Two of these base sections, when joined with the trusses, created a complete curvature of a lateral section of one barrel, which was a compound arc composed of two radii. Two base sections opposing each other formed the valley or beam area of the roof shell. The outer part of the valley sections also set directly on U-heads, eliminating need for longitudinal beams. The inner part, on 12-foot continuous double 4 x 10 beams, bore on 12-foot long continuous double 4 x 10s which were, in turn, supported by 4-foot long 6 x 8s set in 12" x 8" U-heads. The trusses were tied together with inner-lapping 2 x 4s on 8-inch centers which were then decked over with 1/4" plywood. The web members of the bottom quarter of the trusses were made rigid by complicated systems of continuous lateral bracing and plywood diaphragms along the longitudinal axis of the barrels (Pittard 1967).
After much experimentation, it was determined that the best mix for normal weather consisted of 6-1/2 sacks normal Portland cement, 46 percent sand, 54 percent rock, and 2-3 oz. Plastiment retarder. An air-entraining compound was eliminated from the concrete mix which caused the concrete to adhere better to the tendons and eliminated some voids. Voids were a problem throughout and finally were treated as a separate condition: the concrete was placed and the voids patched. They were located with a ball-peen hammer and a Schmidt rebound test hammer; defective concrete was removed with small chipping hammers and voids patched with Sika Colma patching compound which reached 10,000 psi within twenty-four hours (Pittard 1967).
Concrete was placed on the thin shell roof with two mechanically operated Smith Line Concrete Pumps. A typical pour averaged 250 cu. yds. and extended from column to column -- from the crown of one barrel to the crown of the adjacent barrel. Concrete had to be pumped 70' vertically and in some cases an additional 250' horizontally. The pumps had a 4-inch discharge line rated at 30 cu. yds. per hour although the average was about 18 cu. yds. per hour per pump due to time lost in changing hoses and pipe and vibration of concrete. The minimum clearances of 3/4" were required on top and bottom which left little space for the 3/4" aggregate concrete to consolidate properly. Different methods of vibration and various slumps, concrete mixtures, and admixtures were utilized in attempts to eliminate voids. Too much vibration caused the concrete to slide down the slopes to the valley beams, and too little vibration caused insufficient consolidation under the tendons. In the first pours, concrete was pumped from the crowns down to the valley beams; later, concrete was pumped upwards. To pour up or down seemed to have little effect on consolidation. Concrete with low slumps produced fewer voids.
Construction News from London, England described in the following manner how the sequence of the longer span decentering was accomplished (seven barrels on each span):
When numbered and written, the steps for construction of this unique building sound easy, mechanical, logical, and automatic. Another word should be added to this list: difficult. Contractors encountered continual difficulty in the placing of the concrete. Often heavy thunder storms occurred, and the entire placement had to be removed and redone. The notations of chipping, removal, and patching run like a wide band through the account of construction.
Additionally, the construction of the Rivergate was marred and delayed by two noteworthy incidents. The first, Hurricane Betsy, struck on 9 September 1965 at a time when deep excavations had been made for basements; mechanical, electrical, and utility areas; lower parking level; and the never-used link (tunnel) in the never-built riverfront expressway which had been completed but never roofed. Torrential rains accompanied the hurricane, and when dawn broke the next morning, the lower portions of the building were compartmented pools of varying depths which engulfed newly installed air conditioning equipment and control boards. These pieces of equipment were so large that it was appropriate for them to have been placed in their appointed positions, and the building constructed around and over them. No one could have foreseen that one of the worst storms of the century would catch the building without a roof over its vitals. When pools were pumped out, it was discovered that no harm had come to the air conditioning machinery, for they were sealed units, but their control panels were totally destroyed and had to be replaced.
The second incident occurred on the afternoon of 19 September 1967 during the installation of the long-span steel joists which comprise the structure of the flat roof over North Hall, which came to be known as Penn Hall. Engineers and architects had been understandably watchful and concerned about the proper erection of these enormous but slim structural items, and the records of correspondence among the professionals and the construction firm reflect the care given to all aspects of the building of the Rivergate. Unfortunately, concern did not penetrate to those who were actually placing the joists. The Times-Picayune of the following morning accurately reported that two cranes, one on either side of Penn Hall, were setting the 4-ton 138-foot bar joists, and the crane on the Canal Street side "slacked off, and the joist began to buckle" (n.n.n. 1967c). That joist then hit the one adjacent to it setting up a chain reaction, and fourteen of sixteen joists were knocked from their pedestals to the floor some forty feet below.
It was said at the time "that none of the sixteen joists was secured to its pedestals and had some of them been, the chain reaction could have been avoided." One of the architects said that "the joists were temporarily secured by bolts, but the weight of the joists sheared them in two" (n.n.n. 1967c).
This accident which slightly injured three men and seriously injured another was avoidable. During the bid process an unsuccessful subcontractor had recommended that these long-span joists be connected to one another with properly sized diagonal steel braces, dimensioned for proper spacing and causing groups of three or four joists so joined to be erected as a unit and bolted into place. Had this procedure been followed, the joists would not have fallen, and no one would have been injured.
Separate forming and finishing were required to blend the roof structure seamlessly into the column capitals with their restricted sections. Roof soffits, column faces, entrance hoods were all finished in smooth white Portland cement. All walls, interior and exterior, were bush-hammered concrete, and some interior opening trims were the same smooth white Portland Cement finish that was used on the exterior. Exterior paving was smooth concrete. Interior concourse floors were grey terrazzo with elliptical inserts, and the floors of South and North Halls were smooth concrete. Interior ceilings received 1/2-inch blown-on asbestos, a state-of-the-art finish at the time of construction. Some specialty rooms, such as the Amoss Room, cocktail and cafeteria rooms, received elegant wall covering and ceiling treatments. Interior and exterior handrails were identically detailed and finished.
After some years of deliberate neglect and disuse (dismantled furnishings, disconnected plumbing, heating, ventilating, and air conditioning), the Rivergate looked a bit forlorn, but it was not by any means a derelict building. Every aspect and every facet of the Rivergate were of the highest quality, and it was structurally sound. Although the building was closed to public access, the parking garage was still operational, and people who used this facility entered and exited through 401 Convention Center Boulevard. Shortly before demolition, the interior of the parking garage received a fresh coat of white paint.
The Rivergate, a distinct and innovative building, was distinguished by the dynamic expression of its structure and materials. Unfortunately this building became a pawn in the political games brought on by a new gambling era inflicted on the public by local and state politicians. This masterpiece of mid twentieth-century architectural design and engineering technology was scheduled for destruction "allegedly" to create jobs by requiring the developer/operator to build a replacement building. The Architectural Review Committee of the Central Business District Historic District Landmarks Commission, a city agency which by law advises the City Planning Commission on architectural matters, described on three different occasions in three different letters in 1993 and 1994, the proposed replacement for the Rivergate as "inferior" to the Rivergate as a facility for a land-based gambling casino. In the conclusion of the letter dated 12 July 1994, the director of the Historic District Landmarks Commission states: "...the overall building footprint is too large for the site and that if existing functions were redistributed into some of the upper level volume of the building, the overall footprint could be reduced and the building's mass in relationship to the site could be improved" (Hesdorffer 1994).
According to Natalie W. Shivers, architect and architectural historian, to destroy and replace the Rivergate with the proposed building, a pastiche of historic styles, was an irreversible step towards turning New Orleans from a real city into a tourists' theme park (Shivers 1994)). The Rivergate was not only a landmark in New Orleans, a city world-renowned for conserving its historic resources, but it also belonged to the world inventory of daring and capable twentieth-century architecture. Even more important, the Rivergate was designed by New Orleans architects.
Curtis and Davis (Nathaniel C. Curtis Jr. and Arthur Q. Davis, principals, both Fellows in the American Institute of Architects and both among the first to graduate in the modern movement at the Tulane University School of Architecture in New Orleans) earned ninety-five awards in the firm's thirty-two year existence, 1946-1978; thirty-four were national in scope. For the Rivergate the firm received two awards from the Louisiana Architects Association. Curtis (partner in charge and design architect for the Rivergate) had designed buildings in thirty states and nine countries. Projects produced by both the parent firm and Curtis have been published in national and international journals and books.
In the mid 1960s, America was filled with great optimism for the future. In 1969, the year after the Rivergate was completed, the United States landed a man on the moon. This exuberant, confident spirit of the times and the new age of technology were captured in three dimensional form by the Rivergate's creators. The bold, extraordinarily large column-free space of the Rivergate, at that time the largest ever created (n.n.a. 1967a), served as the learning ground for another Curtis and Davis project, the Louisiana Superdome (1975) which set another record for a large column-free volume and earned another award for the firm.
Architects and engineers came from all over the world to study the unique Rivergate under construction. Prior to demolition the building was closed to the public, but according to the guard, visitors from all over the world still stopped to observe the exterior of the structure. The Rivergate made a contribution to the development of a distinct style that has attained a position in the scheme of world architectural history.
Tourism, the city's second most important industry after the port, depends heavily on the preservation of the city's distinguished buildings. The Rivergate made a significant contribution to the continuation of the rich tradition of New Orleans building types. Who knows if or when the world economy will ever again be able to afford such a labor intensive and technically demanding creative design. The Rivergate existed in its original form. Ideal for adaptive reuse as a land-based casino, the Rivergate could have served its new tenants who originally wanted to utilize the building but who were prevented by political pressure from following their sensible instincts. The Rivergate was a national treasure and enrollment on the National Register of Historic Places might have helped to insure its survival for future generations and its service as a model for other cities whose fine, young architecture is experiencing stresses unrelated to quality, utility, or value.
The Rivergate was the property of the City of New Orleans, and by that fact belonged to the people of the City of New Orleans. Citizens were never asked or permitted to vote on whether they wanted to destroy or adaptively reuse the Rivergate. Two mayors and the majorities of two city councils voted to demolish the Rivergate. Concerned citizens, Friends of Rivergate, who spoke at every opportunity on behalf of adaptive reuse of the building as the land-based gambling casino were rebuffed by City and State government at every turn. When some Friends of Rivergate attempted to enroll the building in the National Register of Historic Places, they could act only as concerned citizens, not as owners, for they did not have title to the property.
The record is clear: Friends of Rivergate did not receive the necessary assistance from state or national authorities in the quest for appropriate recognition of a significant example of twentieth-century architecture and engineering. Those who sought this recognition realized from the outset that it might, but probably would not, result in the rescue of the Rivergate. However, notwithstanding the odds, they made every effort to achieve the building's enrollment as a landmark of the United States of America.