"c' est magnifique" is how French and foreign. Architectural Precast Panels Glamorize French Embassy. Fa~ade in Mexico City PCI DESIGN AWARD WINNER

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1 PCI DESIGN AWARD WINNER Archtectural Precast Panels Glamorze French Embassy Fa~ade n Mexco Cty Bernard Kohn Presdent Bernard Kahn Assoces Sant Mande, France Eduardo Terrazas Prncpal Eduardo Terrazas y Asocadas Mexco Cty, Mexco Maro Fastag Presdent PRETECSA, S.A. de C.V. Mexco Cty, Mexco Archtectural precast concrete panels played a promnent role n beautfyng the exteror fa~ade of the new French Embassy n Mexco Cty, Mexco. A total of 2100 precast concrete components wth a large varety of dmensons n flat, curved, and angled shapes were used. In addton to the panels, there are heavy stone-lke balustrades and ralng peces as well as screen panels perced wth square openngs. Two fnshes were used on the panels - a shny, hghly polshed surface and a bush-hammered, rough surface. Ths artcle dscusses the overall concept and soluton, desgn features, producton, and erecton of the buldng wth partcular emphass on the archtectural precast components. "c' est magnfque" s how French and foregn dplomats have descrbed the new French Embassy n Mexco Cty, Mexco (see Fg. 1). The man reason for ths rare exuberance s because of the beautful exteror and nteror fa~ade of the buldng, whch makes abundant use of archtectural precast concrete. The French Embassy s stuated overlookng three streets n a resdental secton of ths captal cty. Because of ths rregular street pattern, t was not possble to buld a symmetrc buldng. Sesmc ssues were also consdered n the desgn of the structure because Mexco Cty s located n a hgh sesmc zone and has had a long hstory of earthquake actvty. The last severe earthquake occurred on September 19-20, The French Embassy faclty actually comprses two adjacent buldngs. The Chancellery Buldng s 13 stores hgh 14

2 .. Fg. 1. Panoramc vew of French Embassy complex showng form and elegance of structure. wth a floor space of 65,000 sq ft (6145 m 2 ). The Publc Buldng s 9 stores hgh wth a floor space of 51,500 sq ft (4790 m 2 ). The total favade surface area of both buldngs comprses 125,500 sq ft (11700 m 2 ) of archtectural precast panels. Underneath the two buldngs, there s a four-level parkng structure. wth a floor space of 186,500 sq ft ( m 2 ). The two buldngs are connected at the lobby level and also on several floors. Fg. 2 shows a vertcal secton of the buldngs and parkng structure. Fgs. 3 and 4 show partal floor plans March-Aprl 1998 of the Chancellery and Publc Buldngs, respectvely. A front vew of the favade of the Chancellery Buldng s shown n Fg. 5. The enlarged embassy complex was bult to accommodate the unprecedented growth durng the last decade n admnstratve and consular servces as a result of a sgnfcant ncrease n trade, toursm, and mutual dplomatc actvtes between the governments of France and Mexco. Offcals of the Mnstry of Foregn Affars of France ssued a stff challenge to the wnnng archtect of ths project: Desgn a buldng that projects a dual mage- one that exhbts "monumentalty" and yet does so wthout suggestng any massveness. Desgn a buldng that s stuated on an rregular ste plan, overlookng three streets. Desgn a buldng that s located n a hgh sesmc zone. The soluton to fndng the proper exteror surface of the buldng was to use archtectural precast concrete panels for the favade. A total of 2100 precast components, wth a large varety of dmensons n flat, curved, and angled shapes, were used. Each panel 15

3 1- IF ~ I ~ ~ ~ ~ 7? I II II m n 111m 111m ;,..,.. I 1-=--=--:. ~ 1 n n ~ r m Ill m I I m I I IA9=ff~=#~ ~~*F ~ ~ I Fg. 2. Cross secton of French Embassy buldngs. Below ground level s the four-story parkng structure. Fg. 4. Part al floor plan of Publc Buldng. A C D G I! I I I I F=*====::f- -j j--4:====~ !!!!!! o'---~. -~ h ' & ' Fg. 3. Partal floor plan of Chancellery Bu ldng. Fg. 5. Front vew of fa<;:ade of Chancellery Buldng. has deep reveals that are made to match the jonts between panels. Ths s done ntentonally to conform to the expresson of the precse archtectural modular system of the fa~ade. In addton to the panels, there are heavy stone-lke balustrades and ralng peces, as well as screen panels perced wth square openngs n front of enclosed loggas. The balustrades 16 were used as decoratve peces to emphasze the buldng's sold mage and overall unty. Precast concrete panels ftted wth alumnum fenestraton were specfed for aesthetc, durablty, and cost consderatons. To acheve the aesthetc objectves, the desgn team erected a panel that ncorporated several appearances. Ths was done by carefully combnng dfferent aggregates of both grante and marble, whch are embedded nto a whte cement matrx. Two fnshes were used on the panels. One s a shny, hghly polshed surface whle the other s a bush-hammered, rough surface (see Fg. 6). Ths latter fnsh was used to create horzontal bands runnng n several layers

4 ... I I. v POLISHED FINISH ~ \\ ANCHOR.<J. NEOPRENE POLISHED FINISH ANCHOR ANGLE 4" X 4"x 5/16" X 8" PRECAST PANEL Fg. 6. Plan and sectons of po lshed and bush-hammered fnshes. Fg. 7. Typ cal sesmc connecton between precast panel and re nforced concrete frame. around the buldng, producng an elegant and dstngushed effect. The ablty to economcally replcate a panel shape played a key role n the decson to proceed wth a precast soluton. Havng a relable, hgh qualty precast concrete manufacturer close at hand (PRETECSA S.A. de C.V., Mexco Cty) made the decson to use precast concrete even easer. The panels were formed followng a very precse archtectural modular system, whch was used n both the vertcal and horzontal dmensons of the entre buldng. The desgn and executon of both real and false jonts that look extremely smlar added to the overall aesthetc desgn. Horzontal and vertcal corner panels were cast as one pece, creatng the effect of "cornerstones." Ths was essental n gvng the entre buldng a vsual structural strength that could not have been acheved usng only flat panels that came together at the angles. Fg. 8. Front vew of Publc Buldng. March-Aprl

5 Fg. 9. Entrance to Chancellery pato (court). Fg. 10. Interor fa<;:ade of Publc Buldng. 18 The panels were cast n two layers, usng a bult-up mx of normal structural concrete along wth a 1 n. (25 mm) thck face mx comprsng whte cement, sand, crushed whte and pnk hard marble together wth black and gray grante chps. The aggregates had to pass rgorous hardness and durablty tests n the precaster's qualty control laboratory. The end result was that the face mx projects a beautful and unform surface that harmonzes wth nearby exstng buldngs and the natural terran. The shny polshed surface was acheved as a perfect mtaton of a Mexcan natural grante called "Acapulco grante." Careful attenton was also pad to the detalng around the wndow openngs. The frames were artculated and separated vsually from the panels. Ths resulted n a precse shadow that separates the panels from the wndows and adds vsual nterest and depth to the fa9ade. The structural frame of the buldngs s renforced concrete. An mportant sesmc feature n the desgn s the connecton between the precast panel and the man concrete frame (see Fg. 7). Ths connecton, whch has been used successfully n other projects, has both ductlty and shock absorbng propertes n transferrng loads, and s partcularly effectve n the event of an earthquake. Panel connectons nclude a 1 1 / 4 n. (32 mm) slot as a gap provson for dfferental movement between any two adjonng stores. Ths was acheved usng 8 n. (203 mm) long galvanzed steel bolts. These bolts attached each precast panel's top nserts to the concrete structure's embedded connecton plates by means of 1 /z n. (13 mm) thck neoprene pads nstalled between metallc washers (see Fg. 7). Erecton logstcs posed a challenge. The panels were hosted nto place wth tower cranes. These cranes were also used to erect other components of the buldng, thus reducng costs and erecton tme. The fact that the panels were fabrcated off-ste made the erecton process more effcent. The erecton of the buldng fa9ade took 6 months to complete.

6 Fg. 11. Balcony balustrade showng bush-hammered precast concrete panel. Fg. 12. Horzontal curved panels showng shn y, h ghly polshed surface combned wth bush-hammered surface. Constructon of the entre buldng took 2 years. The buldng was opened for offcal use at the end of Completed vews of the French Embassy buldng are shown n Fgs. 8 to 14. The total cost for materals, haulng and erecton of the precast concrete fa~ade was $1.80 mllon. Ths fgure was economcally compettve n Mexco and s far lower than anythng that could be acheved wth precast concrete n the Unted States. In June 1997, the French Embassy project won a desgn award n the PCI Desgn Awards Program for "Best Publc Buldng." The jury' s ctaton was as follows: "The use of two dstnctve fnshes on ths project adds a lot of nterest, especally from a dstance. The combnaton of true jonts and reveals was ncely done so that the dstnctons between the two cannot be seen, as they can n some buldngs of ths type. Ths was a well-done example of combnng a formdable presence wth some subtle fnsh and detal aspects." CONCLUDING REMARKS The overall archtectural effect of the precast panels, where functonal and aesthetc consderatons are ntegrated, mparts to the buldng a very dstngushed and elegant appearance. The structure communcates both a Fg. 13. Fnshed v ew of French Embassy compl ex. March-Aprl

7 dgnty and a soberness that s partcularly well-suted to the mage of such an mportant publc buldng. Ths s due to the strong ntegraton of concept, desgn, producton, and constructon usng a team approach. The buldng has now been n use for just over two years. The owner and the entre desgn and constructon team are very pleased wth the functonng aspects and aesthetcs of the buldng. Indeed, the new French Embassy has fast become a wellknown cty landmark. The embassy staff s enjoyng the new faclty and vstors as well as the publc all admre the beautful archtecture of the buldng. Fg. 14. Nght-tme vew of French Embassy complex. CREDITS Owner: Mnstry of Foregn Affars of France, Mexco Cty, Mexco Archtects: - Bernard Kohn Assoces, Archtectes Urbanstes, Sant Mande, France - Eduardo Terrazas y Asocadas, Arqutectos Urbansts, Mexco Cty, Mexco Structural Engneer: Garca Jarque Ingeneros, Mexco Cty, Mexco, n collaboraton wth Marc Mmram, Pars, France Precast Concrete Manufacturer: PRETECSA S.A. de C.V., Mexco Cty, Mexco Project Manager and Coordnator: Janco Ingeneros S.A. de C.V., San Francsco, Mexco Concrete Structure and Interor Fnsh Contractor: Desarrollo Monarca, Mexco Cty, Mexco 20