サン・アントニオ・ミッションズ国立歴史公園 (San Antonio Missions National Historical Park) はサン・アントニオ川に沿って建つ4つの伝道所で構成される。最も上流にあるのがコンセプシオン伝道所 (Mission Concepción) で、1716年にテキサス東部に建設されたヌエストラ・セニョーラ・デ・ラ・コンセプシオン・デ・ロス・アイナイス (Nuestra Señora de la Purísima Concepción de los Hainais) が前身で、1731年にサンアントニオに移された。米国で最も古い修復されていない石造の教会。
San Antonio Missions National Historical Park (U.S. National Park Service)
In 2020 I was proud to have been involved in the stabilization of the 18th century dome on the church of Mission Concepcion, part of the San Antonio Missions World Heritage Site #WorldHeritage #sanantonio pic.twitter.com/Fm9xjPcCCz
— Patrick Sparks (@psparks1960) 2020年12月31日
The project team included Ford, Powell & Carson architects, Pugh Constructors contractor, Hunt Restorations mason, and Tommy Lambert plasterer.
— Patrick Sparks (@psparks1960) 2020年12月31日
The church was completed in 1755 by the Franciscans, but was abandoned for about a century after secularization in 1790s. pic.twitter.com/Ii13rSzRa3
We became concerned when a circumferential crack appeared in the 1990s stucco covering along the cornice. No other distress was apparent, but the stucco was largely reinforced, so no cracks would appear except where the wire mesh was discontinuous. pic.twitter.com/GRzMqoU25M
— Patrick Sparks (@psparks1960) 2020年12月31日
Probes showed the original cornice to be intact, but suggested that the circumferential crack might extend horizontally into the outer part of the dome. GPR scans showed that the base of the dome was made largely of rubble. pic.twitter.com/nsAtXgyNrl
— Patrick Sparks (@psparks1960) 2020年12月31日
We also obtained a laser scan of the interior and exterior of the dome, so we could analyze the dome's geometry. The dome is mostly conical and with a thinner part near the high shear zone. pic.twitter.com/CpBMB3qAtG
— Patrick Sparks (@psparks1960) 2020年12月31日
We tested samples of the tufa and mortar, finding an approximate compressive strength of just 100-psf pic.twitter.com/8r37mt04o2
— Patrick Sparks (@psparks1960) 2020年12月31日
Probing of the dome proper was problematic. Here is an image of the typical masonry in the drum. pic.twitter.com/begss59p14
— Patrick Sparks (@psparks1960) 2020年12月31日
Taken together, our investigation, testing and analysis suggested that the circumferential crack was caused by creep/consolidation of the weak masonry, and that shear failure just above the springing was possible. To strengthen, we added a continuous stainless steel tension band, pic.twitter.com/NQRB5TiWej
— Patrick Sparks (@psparks1960) 2020年12月31日
...and installed 1/4" dia stainless rods along with grout injection, selectively in the risk zone. We also used stainless steel plaster lath on both interior and exterior to provide confinement.
— Patrick Sparks (@psparks1960) 2020年12月31日
We felt met the requirements of safety under least intervention. pic.twitter.com/ecbV0rRhkJ
