INTRODUCTION The Building This building, designed by the noted modernist architect, Eero Saarinen, consists of a spherical segment dome-shaped concrete roof enclosing a triangular area approximately 160 feet on a side. The primary building function is the enclosure of an 1238 seat auditorium and associated lobbies, restrooms, and projection facilities. The dome is entirely supported on three points at the vertices of the triangle, or was by the original design. As every article written on the dome seems to mention, the total weight of the roof is approximately 1500 tons, and the thickness of the roof shell is 3 ½ inches, thickened to 18‖ at the perimeter.
History The Massachusetts Institute of Technology (MIT) in Cambridge, Massachusetts, commissioned renowned architect Eero Saarinen to design a 1,200-seat auditorium and 200-seat theater in 1950. Anderson, Beckwith & Haible of Boston were the associate architects. The consulting engineer was Ammann & Whitney of New York, which had previous thin-shell experience.
The building was named in honor of chain-store magnate Sebastian S. Kresge, whose foundation donated $1.5 million towards the cost of the auditorium and an adjacent cylindrical chapel, also designed by Saarinen. Kresge, a strong advocate of higher education, had previously funded the construction of a building at the Harvard Business School. The history of this building is more fully covered in the discussion in Module I.
Technology The building‘s roof structure is a spherical dome. However, because of the interruptions to the doubly-curved spherical shape due to the triangular plan of the building, severe edge disturbances to the membrane stresses in the shell result. This requires the addition of a stiffening beam around the perimeter of the building. The thickening of the shell to18‖ at the perimeter is intended to provide the necessary stiffening to the edge of the shell. A review of the discussion of edge stiffening of shells in Module I can be accessed here. A second ‗shell‘ was intended to be provided by the addition of a 2 ½‖ non-structural layer of gunite (spray-applied concrete), which was initially intended as the substrate for the roofing. Changes during construction permitted the substitution of a lightweight ‗nailable‘ concrete material. The requirement for stiffening of the edge of the shell, and the subsequent problems, described below, prompted Billington‘s criticism of this building, and other architect-designed shell structures as , ―This difference in viewpoint explains why it was that many of the most prominent thin shell concrete structures designed during the 1950s by architects generally were not thin, far overran cost estimates and often performed badly to the point of collapse: the Berlin Congress Hall, the Sydney Opera House, the Kresge Auditorium, the New York TWA Terminal—all proclaimed during this period as precursors of a new architecture.‖ Other technological concerns in the design of the structure were the transmission of sound from the exterior into the auditorium, and the application of a roof membrane to the shell. Much of the concern over sound transmission was reflected in the approval process for the substitution of lightweight concrete for the gunite. The acoustical consultant would only approve the substitute material if it had sufficient mass to inhibit sound transmission. The selection and application of a roof membrane to the doubly-curved shell was a particularly difficult technical problem. There is little evidence in the written record that this was given sufficient attention, other than concerns over the budget. The consequence of this inattention became quite evident a few years after the construction of the building, as detailed below.
CONSTRUCTION ASPECTS Concrete Placement of concrete on sloped doubly curved surfaces is difficult at best, and the problems were compounded in the construction of the Kresge Auditorium by the steepness of the slopes at the vertices, and by the edge stiffening beams that were raised above the level of the top of the roof slab. The selection of the concrete mix for a project like this presents difficulties of its own. It is necessary to choose a stiff mix (concrete stiffness is estimated by ‗slump.‘) so that the
plastic concrete will not segregate or flow down the forms, while it is more difficult to consolidate stiff concrete properly. During construction, trials were undertaken resulting in a contractor request to increase the slump to 2 ½‖, ‗since a trial pour on a mockup of the corners has indicated that this is necessary to insure proper workability, particularly in the corners with their heavy steel concentration.‘ Three construction photos of the concrete placement follow. They are very revealing of the kind of difficulties involved in the construction of this structure, and will be discussed in detail.
Construction Photo 1 Construction Photo 1 shows the preparations for concrete placement at the vertex at one of the buttresses. It is dated February 2, 1954. It shows extensive preparations for one of the steepest concrete placements in the building. The crew size is very large for a concrete placement of this size. A single vibrator, for consolidation of the concrete is in evidence at the left edge of the photo towards the top. It also appears that a top form had to be added to prevent the plastic concrete from flowing to the bottom. The crew along the right edge appears to be consolidating concrete by hand through the edge beam forms. There is a general atmosphere of uncertainty, with nobody in the crews working particularly hard or in any focused manner. The cold weather is also significant, in that it can prevent the concrete from achieving its full strength.
Construction Photo 2 Construction Photo 2 shows the extraordinary and difficult combination of stiff (low slump) concrete, congested, large-diameter reinforcement, and sloping roof. The main method of transporting concrete seems to be the shovel in the foreground. It is very difficult to lay out the double curvature of the roof with 2 4 screed rails,and the placement of the rails does not appear particularly accurate. Moreover, the rails are being disturbed by foot traffic. The concrete near the edge beam is showing the difficulty in working with low-slump concrete, as it has not been sufficiently smoothed by the screeding operation. It also does not appear that sufficient cover is being maintained over the reinforcement, which will accelerate the process of corrosion of the reinforcement. A man with a single small vibrator is attempting to consolidate the concrete. The concrete in the foreground does not appear to be consolidated, and again does not appear to have sufficient cover over the reinforcement.
Construction Photo 3 Construction photo 3 shows the placement of the concrete in the raised edge beam. This work is being executed very poorly under very difficult conditions. Concrete has been placed in the edge beam forms, but has not been screeded, and the vibrator needed to consolidate the concrete is not in evidence. A cold joint is forming at the end of the beam closest to the viewer, and the worker kneeling on the beam does not seem to appreciate having a photo taken at this moment. The worker finishing the slab has also run out of concrete, and appears to be trying to use his tools to transport concrete. The conditions under which the concrete was placed, which are very evident in the photos is at least partially responsible for some of the conditions later observed in the section entitled ‗Repair History.‘ In addition to problems generated by the structural failure of the dome, the problems of poor consolidation of the concrete and inadequate cover on the reinforcement resulted in an acceleration of the corrosion of the reinforcement, and the general deterioration of the roof shell.
Roofing The roofing material seems to have been a subject of discussion and reconsideration, as much as the construction of the substrate for the roofing. A May 8, 1952 letter from Redfield Proctor, Chairman of the Board of Vermont Marble Company discusses the fabrication of marble tiles for
the roof, and appears to request that the architects reconsider a request for tiles of dimension 2 feet four feet, and use stones of a foot square, on grounds of the curvature of the roof and the fabrication costs for the larger tiles. An estimate from Eero Saarinen and Associates dated August 6, 1952 shows an estimated cost of $14,000 for ‗Roofing,‘ with handwritten notes ‗does not include tile‘ and ‗add $50,000 for tile roof.‘ This estimate is adjusted on an August 18, 1952 internal M.I.T. document, and the estimate of $14,000 for roofing remains with a typewritten footnote, ‗This does not contemplate tile roofing – add $50,000 for tile roof. This estimate was later increased to $40,000 for a lead coated copper roof on a three column estimate summary, in a column entitled 12/30/52 (Building Comm. Visit). The roof was later to be planned to be built of lead coated copper sheets. A credit memo dated August 4, 1953 allows a credit of $1000 for the substitution of 12# to 15# lead coated copper sheets for the 40# to 50# product. While the building was under construction, on September 9, 1953, a letter from the architect to the contractor discusses the use of a lightweight nailable concrete deck for the outer shell, listing as one of the advantages ‗possible saving in cost in the application of the copper roofing inasmuch as the cleats could be nailed directly into the concrete.‘ The use of these copper roofing ‗tiles‘ was eventually abandoned, due to problems in forming the joints. The roof system substituted was a liquid-applied roof, consisting of fine limestone chips in an acrylic polymer binder.
Application of the Trowel-on Roofing material. MIT Photo Archive CC-W16-233, ‗Beginning Application of Orostone‘
REPAIR HISTORY Repairs and Modifications during Construction Although the contemporary accounts of the construction of the shell for Kresge Arena discuss the roofing problems and the modifications to the roof undertaken quite candidly, there is almost no mention in contemporary accounts of the serious structural problems encountered with the shell. Our current understanding of the modifications that had to be undertaken rest on two pieces of evidence. A 1985 article by Cohen, Dobbs, and Combs described in detail the ca. 1979-80 repair program, and will be used later in this discussion as a major reference for that work. In this paper, the authors, two employees of Amman and Whitney and one of MIT Office of Physical Plant, construct an analytical model of the history of the work as accurately as possible. Their loading history of the building includes the following phases 1 Start of analysis corresponding ot March 19, 1954, when the forms were first removed from the newly poured shell
2, 3.
Unhindered creep of the concrete shell from March 19, 1954, until March 31, 1954
4.5. Unhindered creep of the concrete shell from March 31, 1954 until April 28, 954, at which time the Auditorium was cribbed. 6. The model is jacked upward at the crown of the edge beam to a total vertical downward deflection of 5 inches. 7. A small percentage (9.3%) of the force necessary to apply to the crown of the edge beam in Load Step 6 at Node 109 is applied to Node 133, on the edge beam, where the outer columns are to be located. [this appears to be a technical correction to the results of the computer analysis]. 8. the model deflections of the column base locations are fixed and the column elements corresponding to the structure mullions are activated.... The original architectural drawings allowed for 1 ½‖ maximum vertical movement of the edge beam so that roof loading would not be transferred to the window mullions. However, the structure evidently underwent much larger uncontrolled creep deflections on removal of the temporary shoring for the roof. The ‗structure mullions‘ refer to a modification of the vertical mullions of the windows, which was necessary to make them into load-carrying elements. The edge beam underwent large magnitudes of creep displacement (clearly well over 5‖) before the entire roof was shored on April 28, 1954. A drawing from the MIT Physical Plant Archive, produced by Babcock Davis Associates, ‗Iron, Steel, and Mechanical Specialists,‘ dated May 10, 1954 shows details of a series of vertical window mullions, made as slender as possible out of very heavy stock (typically 1‖ thick or more). An additional set of large mullions is labelled ‗49 edge beam strut.‘ So, ironically, the claim of Stephen F. Spencer, the Superintendent of Buildings and Inspector of Buildings for the City of Cambridge, that the glass walls would be called on to support the concrete roof, actually proved to be a correct assessment. The change in the type of roof was also finalized during construction. A later account of the first re-roofing, in the following section, describes the last-minute alteration to the proposed roofing scheme, At first, the architects had planned to finish the roof off with a facing of lead-coated copper applied as diamond-shaped plates. But mechanical problems with the seams showed up when the designers tried to join sample sheetmetal panels together. At the corners of the pattern, where four diamonds came together, they found that 12 thicknesses of sheet metal piled up, one on top of the other. Not even the most skilled craftsmen could make these corner joints with reasonable speed. So this scheme was dropped. Failing to solve the problems with the sheetmetal skin, the designers specified instead a liquid-applied covering of fine limestone chips in an acrylic polymeric binder
First Re-roofing
The continuation of the above Engineering News-Record describes graphically the problems encountered with the liquid-applied roofing system of the Kresge Auditorium In service, the roof sustained pronounced differential heating. At times, one side of the roof would be covered with snow; the other side, completely dry, would be baked by a brilliant winter sun. Steep temperature gradients occurred across the thickness of the roof system, too. The inside surface remained fairly constant (because the auditorium is air conditioned) while the outside surface temperature varied with changes in the weather. The result of the uneven heating of the roof system was unequal expansion and contraction of the elements of the system. Because the lightweight concrete acoustic layer was unconnected to the structural shell, expansion of this layer could accumulate across wide areas of the roof surface. To relieve the stresses induced by thermal expansion, faults developed in the concrete layer and caused surface irregularities as great as ½ in. At the edges of the shell where the concrete top fill butted against a structural edge beam, the flashing was destroyed. Water entered the roof system through these first openings and lodged under the top layer of concrete. In hot weather, the trapped water vaporized and raised in the concrete topping a bubble that followed the sun across the roof surface. The deformations caused by the travelling bubble cracked the concrete topping even more. The re-roofing appears to have been directed by the George A. Fuller Company, the original construction contractor for the building. The Engineering News-Record article quoted above does not mention an engineering consultant for the work, although the contribution of MIT‘s staff engineers is acknowledged. The roofing scheme involved cutting relief kerfs into the lightweight concrete outer shell and drilling anchors into this material to fasten it more positively to the structural shell. The new roofing membrane consisted of roughly 2 foot square sheets of lead anchored to a stainless steel wire grid. The joints between lead sheets were soldered in the field. An elaborate venting scheme was also installed (see Plate IV) to relieve moisture trapped under the roofing membrane. Additionally a de-icing system was installed at the buttress points of the roof to make sure that they roof could drain water and ice ponded at the joints between edge beams. It is not difficult to understand why this roofing system failed. Although the issue of differential movements of the double shell may have been addressed by the repairs, the application of the roofing material called for approximately 20,000 feet of flat, hand-soldered seams in a roof of complex geometry subject to very large temperature variations. Moroever, the elaborate venting details shown in Plate IV are very difficult to execute, while retaining a weathertight roofing membrane. As a result, although lasting approximately 15 years, as opposed to the 8 year life of the original roof, in 1979, the building had to be closed pending further repairs to the concrete structure and to the roof, as investigation of the concrete structure had disclosed serious defects in the concrete in the shell and the edge beams.
An illustration of the process necessary to achieve watertight joints for the first re-roofing. The new roof included approximately 20,000 lineal feet of soldered lap seams, such as that illustrated here.
This photograph, taken after the first roof repair, shows dramatically the thermal gradients to which the roof of the Kresge Auditorium was subjected. The de-icing system at the corner has either failed or been overwhelmed by the large volume of snow and ice.
Second Re-roofing and Repair of Concrete Edge Beams, Buttress, and Shell According to the account of Amman and Whitney, the repair and modificatoin program for Kresge Auditorium began in September 1979. Inspections of the visible portions of the edge beams had disclosed severe damage to these members, especially in the vicinity of the three abutments, where snow, ice, and water accumulated during winter months. Apparently, the defects uncovered were much more serious than anticipated as several newspaper accounts in early October 1979 indicate that the Auditorium was forced to close. ―The university originally had planned to close the building next spring for roofing work, but speeded up its plans after workers found more damage than expected....‖ In the investigation which followed, the entire lead roofing membrane was stripped, the exterior lightweight concrete shell was removed, and the waterlogged insulation above the inner structural shell was removed to expose the bare concrete of the structural elements: shell, edge beams, and buttresses. Severe problems with deterioration of the concrete below the exterior shell and insulation, and in the edge beams, particularly adjacent to the buttresses were disclosed in these investigations. The findings of the investigation are summarized in a report by the Engineer, Amman and Whitney, the firm charged with the design of the original structure. This work is also summarized (the omissions from the
report in the article are particularly revealing, as discussed in the section on the problems in the initial construction of the building) in an article authored by a managing partner and a senior associate of Amman and Whitney and a member of the MIT Department of Physical Plant. The edge beams were carefully shored before the inspections, as it was clear that a significant amount of the concrete and reinforcement at the buttresses was going to have to be removed and replaced. According to the account of Amman and Whitney During removal of the outer (lead) roofing, a significant number o fjoint failures were observed at the connections of adjacent sections of the lead shingles. Many of thes joints were found to be taped to prevent leakage....In addition, the lightweight concrete was found to be extensivel cracked. The report follows with a description of the results of the direct inspection of the structural shell. Visual inspections of the structure in 1973 and 1978 had revealed serious deterioration of the roof edge beams in the vicinity of the three abutments. The deterioration consisted primarily of ―leaching‖ of the cement paste resulting in the disintegration of the concrete in these areas. In addition, hairline cracking of the edge beams was observed. The damage to the edge beams at the west abutment was more severe than that observed at the other two abutments. A continuous flow of water was also observed at these locations. It was thought that the constant flow of water was caused by condensation beneath and/or leakage through the lead roof covering. The water apparently ran down the shell and escaped from beneath the lead flashing at the three corners of the roof. Concrete cores were also extracted from the shell concrete and the edge beams. In general, where suitable core specimens were recoverable, the strength of the concrete was found to be well above the required strength, ranging from 4500 psi to 5500 psi. The edge beams at the abutments were generally found to be in poor condition, with large zones of severely deteriorated concrete and corroding reinforcement in the upper portions of the cross-section. Petrographic analysis of the cores and visual inspection both indicated that the damage was primarily due to freeze-thaw action, with water entering the concrete after passing through flaws in the roofing membrane, and causing concrete deterioration as a result of freeze-thaw action. Notes on the petrographic analysis of the cores indicate that there is minimal entrained air, which makes the concrete extremely vulnerable to freeze-thaw action, and 3% to 5% entrapped air, by volume, which is an indication of poor consolidation of the concrete. The survey also found small non-structural cracks widely distributed throughout the shell structure and larger parallel cracks in the vicinity of the abutments. Areas of delamination of the shell concrete adjacent to the buttresses were also noted. The recommendations called for and subsequent repairs provided a full-depth repair for the lower 25 feet of the edge beams at the west abutment and the lower 15 feet of the edge beams at the other two abutments. Keeping the shoring in place on the edge beam, all of the concrete and reinforcement at these locations was removed and replaced. New edge beam forms were built and reinforcement was tied into existing reinforcement. The specified concrete had a minimum
28 day strength of 3750 psi, a specified slump of 2‖, and 4%-6% entrained air by volume. New concrete was bonded to old by a high-modulus epoxy material, similar to that used for crack injection. Delaminations were repaired by a pressure injection method.
Photo of buttress at Kresge Auditorium (2001), showing that corrosion of the steel, and delamination of the concrete continue to be a problem for this building.
LESSONS LEARNED The Kresge Auditorium demonstrates several important principles in the management of thin-shell concrete structures. Even from the time of its design, it reveals the tensions between the architectural and the engineering profession over the principals to be applied to design. Although the architectural profession enjoyed the possibilities for expression that resulted from the apparent ‗free forms‘ of shell construction, the engineering profession continued to caution that only certain forms were appropriate for thin-shell construction. Although Tedesco‘s shells performed very well structurally, the reliance on parabolic barrel vault types must have appeared uninteresting and mundane to the architectural profession (see also Boothby and Rosson 1998). As Billington points out, the conception of the Kresge Auditorium shell depends on a misunderstanding of the importance of edge effects, which resulted in severe structural problems for the Kresge Auditorium shell.
The problems with this building did not end with the resolution of the structural problems. The shell was difficult and unusual to construct, and significant difficulties were encountered in concrete placement, protection of the reinforcing steel and above all in waterproofing the roof of the building. The satisfactory resolution of these problems had to wait until decades after the commissioning of the building, and through several trials of different roofing procedures. The repair of the construction problems was vexing, costly, and forced the closure of the building for a few months. The fact that this building endured through such frequent and costly repair campaigns reflects the understanding of the owner of the building that they are dealing with a significant and worthy example of modern architecture and that the pain of repairing it properly is worth offset by the value of this building. This understanding is assisted by the association of the building with an important architect, who is recognized as one of the pioneers of the modern movement in architecture and the adaptation of thin-shell concrete construction to the needs of modern architecture.
BIBLIOGRAPHY Billington, David, The Tower and the Bridge, New York, Basic Books, Inc. 1983. p. 170. Boothby, T.E. and Rosson, B.T. Historic Preservation of Thin-Shell Concrete Structures. Journal of Architectural Engineering, 4(1):4-11, March 1998 Cohen, E., Dobbs, N. and Combs, W. Inspection, Analysis, and Restoration of MIT Kresge Auditorium. Rehabilitation, Renovation and Preservation of Concrete and Masonry Structures. ACI SP-85. Detroit, American Concrete Institute. pp. 31-94. MIT Photo Archives, MIT Museum CCW16-218e ‗Pouring roof at west buttress‘ February 2, 1954. MIT Photo Archives, MIT Museum CCW16-218m ‗Crew placing concrete at corner‘ undated MIT Photo Archives, MIT Muesum CCW16-218o ‗Placing Concrete at Edge Beam‘ undated Letter, dated October 27, 1953, Ammann & Whitney to George A. Fuller Company, 1953 Correspondence File, MIT Office of Physical Plant Archive. Roof Repair: More Than Skin Deep, Engineering News-Record, August 8, 1963, pp. 80-84. Roof Problems Close Auditorium at MIT, Hartford Cournt, October 3, 1979. Draft of Report on Investigations and Repairs to Kresge Auditorium, by Ammman and Whitney, located in MIT Physical Plant Archive.
Plate I. Original design of the roof, showing lead-coated copper sheet layout. This design was discarded at the time of construction, as being excessively elaborate and difficult to fabricate.
Plate II. Fabricators drawing of the structural mullions for the windows, which were ultimately used to support the edge beams, after these had undergone excessive creep deflections.
Plate III. Architect’s original drawing of the details of the window mullions, showing the 1 ½” allowance for deflections of the edge beam.
Plate IV. Contractor‘s drawing of first re-roofing scheme. While this has in many ways the appearance of the original roofing scheme in Plate I, the elaborate venting details are particularly noteworythy. The execution of this roofing system, as shown in Figure ???, was particlarly demanding. ____________________________________ _________________________________
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Participants
Eero Saarinen (architect)
Architecture
Eero Saarinen & Associates
Structural engineering
Ammann & Whitney
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Roofs are generally shaped like a curved shell and assemble to larger structures architecture, the roof construction in general shell structures by slight build with shell elements.Thin shell is a shell with a thin dimension, the deformations are not disproportionate to the thickness. Shell structure of the various structures such as bending plates that are flat. Shell membrane bending deformations, when he stresses that make the structure of the shell of a slender solid roof made. In this article we have tried one of the exemplary structure of concrete shell roof MIT campus architecture, the name of the building, the roof concrete shell visit in Kresge Auditorium 48 Massachusetts Avenue, Cambridge, Massachusetts is located. Kresge Auditorium of the famous Eero Saarinen designed in 1953 and consecrated in 1955 with the inauguration of the MIT Chapel architecture. Kresge Auditorium concrete shell roof structure looks so elegant thin shell structure, one-eighth of a world growing at a height of 50 feet, and decided by the vertical glass walls, so that it reaches the country, on three points. 1200 tons of weight of the roof structure of the concrete composite shell with innovative technology. The architecture of the concrete shell with a conical roof at the edge of the roof, designed the building, when viewed from the top of the construction of the roof structure, viewed as a clam.
You Read Concrete Shell roof structure Kresge Auditorium, MIT campus Architecture. Thanks for Your visit. I hope You can get new inspirations and find what You are looking for.
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The main acoustical problem with Kresge Auditorium was the very short reverberation time. Reverberation time is the number of seconds it takes for an impulse sound (i.e. hand clap) to die out. A short reverberation time, say one second or less, is good for speech and solo performances miked close up since echos from the hall don't blur the sound. On the other hand it lends an unwanted sharpness to ensemble music. The sound of the instruments don't blend. A very long reverberation time, say more than three seconds, muddies the sound by adding too much echo. It is like music in a cathedral. Ideally, for ensemble groups you want a reverberation time in the two second range, longer for full orchestras, shorter for quartets. The Kresge auditorium was optimized for lectures. The architects apparently overlooked the fact that the hall would be used for music as well. The problem is similar to that of "sharpening" in digital photos. Too much and the picture appears wirey or grainy, too little and it appears overly soft and fuzzy. Eugene Levy's piano performances were well suited to the characteristics of the hall in the 50s. The fix by BB&N employed reversible panels with sound absorbing material on one side and reflecting material on the other so that the reverberation time could be altered depending on the performance. Not much could be done about the uneven sound dispersal throughout the auditorium except to proved supplementary loudspeakers to reinforce the sound in the blanked out areas. In general, most classical music was composed to be played in halls with wood and masonry construction and elaborate ornamentation that reflected the sound into all nooks and crannies of the auditorium. From an acoustical point of view, the old halls are still the best. It's mostly a question of the mass of the construction materials. Modern materials, steel, glass, and plastic tend to reflect sound too well and must be treated to provide an adequate acoustic ambience. They don't make them like they used to. But I suppose that's more than anyone on the LUG wants to know about architectural acoustics.
