WHY PAGODAS DON'T FALL DOWN

Why Pagodas Don’t Fall Down?

Tại sao những ngôi chùa không bị đổ sập

In a land swept by typhoons and shaken by earthquakes, how has Japan’s tallest and seemingly flimsiest old buildings – 500 or so wooden pagodas-remained standing for centuries? Records show that only two have collapsed during the past 1400 years. Those that have disappeared were destroyed by fire as a result of lightning or civil war. The disastrous Hanshin earthquake in 1995 killed 6,400 people, toppled elevated highways, flattened office blocks and devastated the port area of Kobe. Yet it left the magnificent five-storey pagoda at the Toji temple in nearby Kyoto unscathed, though it levelled a number of buildings in the neighbourhood.

Tại 1 vùng đất nằm ngay tâm bão và tâm chấn, làm thế nào mà những công trình gần như mõng manh cũ kỹ và cao trọc trời của Nhật Bản có niên đại gần 500 tuổi hay những ngôi chùa gỗ hoàn toàn đứng vững hàng thế kỷ qua? Theo ghi nhận chỉ có 2 công trình bị đổ sập trong suốt 1400 năm qua. Những công trình đó đã biến mất bởi sự phá hủy do lửa là kết quả của sét đánh hoặc nội chiến. Trận động đất thảm khốc ở Hanshin vào năm 1995 đã giết chết 6,400 người, lật đổ các đường cao tốc, dỡ đổ các tòa nhà văn phòng và tàn phá khu vực cảng Kobe. Tuy nhiên, nó đã bỏ sót lại ngôi chùa 5 tầng lộng lẫy ở ngôi đền Toji ở gần thành phố Kyoto không bị ảnh hưởng gì , mặc dù nó đã san bằng một lượng lớn tòa nhà trong khu phố.

Japanese scholars have been mystified for ages about why these tall, slender buildings are so stable. It was only thirty years ago that the building industry felt confident enough to erect office blocks of steel and reinforced concrete that had more than a dozen floors. With its special shock absorbers to dampen the effect of sudden sideways movements from an earthquake, the thirty-six-storey Kasumigaseki building in central Tokyo-Japan’s first skyscraper–was considered a masterpiece of modern engineering when it was built in 1968.

Các học giả Nhật Bản đã bị gây xao nhãng về lý do tại sao những tòa nhà cao và mảnh mai này vẫn ổn định. Chỉ mới ba mươi năm trước đây ngành công nghiệp xây dựng cảm thấy đủ tự tin để xây dựng các khối văn phòng bằng thép và bê tông gia cố mà có hơn 12 tầng. Với các bộ giảm chấn đặc biệt để giảm ảnh hưởng của những chuyển động đột ngột từ một trận động đất, tòa nhà Kasumigaseki 36 tầng ở trung tâm Tokyo – tòa nhà chọc trời đầu tiên của Nhật – được coi là một kiệt tác của kỹ thuật hiện đại khi nó được xây dựng vào năm 1968.

Yet in 826, with only pegs and wedges to keep his wooden structure upright, the master builder Kobodaishi had no hesitation in sending his majestic Toji pagoda soaring fifty-five meters into the sky-nearly half as high as the Kasumigaseki skyscraper built some eleven centuries later. Clearly, Japanese carpenters of the day knew a few tricks about allowing a building to sway and settle itself rather than fight nature’s forces. But what sort of tricks?

Tuy nhiên, năm 826, chỉ với những cái cọc và nêm để giữ cho cấu trúc bằng gỗ của ông thẳng đứng, người chủ xây dựng Kobodaishi không ngần ngại đưa ngôi đền toji hùng vĩ của mình đạt đến năm mươi lăm mét lên bầu trời – gần một nửa so với tòa nhà chọc trời Kasumigaseki xây dựng khoảng mười một thế kỷ sau. Rõ ràng, các thợ mộc Nhật Bản ngày nay đã biết một vài thủ thuật về việc cho phép một tòa nhà lắc lư và ổn định hơn trong việc chống lại các thế lực tự nhiên. Nhưng thủ thuật là gì?

The multi-storey pagoda came to Japan from China in the sixth century. As in China, they were first introduced with Buddhism and were attached to important temples. The Chinese built their pagodas in brick or stone, with inner staircases, and used them in later centuries mainly as watchtowers. When the pagoda reached Japan, however, its architecture was freely adapted to local conditions they were built less high, typically five rather than nine storeys, made mainly of wood and the staircase was dispensed with because the Japanese pagoda did not have any practical use but became more of an art object. Because of the typhoons that batter Japan in the summer, Japanese builders learned to extend the eaves of buildings further beyond the walls. This prevents rainwater gushing down the walls. Pagodas in China and Korea have nothing like the overhang that is found on pagodas in Japan.

Chùa nhiều tầng đã du nhập Nhật Bản từ Trung Quốc vào thế kỷ thứ sáu. Như ở Trung Quốc, họ được giới thiệu lần đầu tiên với Phật giáo và được gắn liền với các đền thờ quan trọng. Người Trung Quốc xây dựng chùa của họ bằng gạch hoặc đá, với cầu thang bên trong và sử dụng chúng trong những thế kỷ sau đó chủ yếu là xây tháp canh. Tuy nhiên, khi các ngôi chùa đến Nhật Bản, kiến trúc của nó đã được tự do thích nghi với điều kiện địa phương – chúng được xây dựng thấp hơn, điển hình là 5 chứ không phải là 9 tầng, chủ yếu làm bằng gỗ và cầu thang được tách ra bởi vì ngôi chùa Nhật Bản không có công dụng thực tế nào nhưng trở thành một vật thể nghệ thuật. Bởi vì những cơn bão đập vào Nhật Bản vào mùa hè, các nhà xây dựng Nhật Bản đã học cách mở rộng các mái hiên của các tòa nhà xa hơn các bức tường. Điều này ngăn nước (mưa) dột qua các bức tường. Các chùa ở Trung Quốc và Hàn Quốc không có gì giống như phần nhô ra trên các ngôi chùa ở Nhật Bản.

The roof of a Japanese temple building can be made to overhang the sides of the structure by fifty percent or more of the building’s overall width. For the same reason, the builders of Japanese pagodas seem to have further increased their weight by choosing to cover these extended eaves not with the porcelain tiles of many Chinese pagodas but with much heavier earthenware tiles.

Mái nhà của một ngôi đền Nhật Bản có thể được làm vượt qua các cạnh của cấu trúc tầm năm mươi phần trăm hoặc nhiều hơn tổng chiều rộng của tòa nhà. Cũng vì lý do này, các nhà xây dựng chùa Nhật dường như đã tăng trọng lượng mái mở rộng này bằng cách chọn gạch đất nung nặng hơn nhiều thay vì gạch sứ như nhiều chùa ở Trung Quốc.

But this does not totally explain the great resilience of Japanese pagodas. Is the answer that, like a tall pine tree, the Japanese pagoda with its massive trunk-like central pillar known as shinbashira simply flexes and sways during a typhoon or earthquake) For centuries, many thought so. But the answer is not so simple because the startling thing is that the shinbashira actually carries no load at all. In fact, in some pagoda designs, it does not even rest on the ground, but is suspended from the top of the pagoda-hanging loosely down through the middle of the building. The weight of the building is supported entirely by twelve outer and four inner columns.

Nhưng điều này không hoàn toàn giải thích sự phục hồi tuyệt vời của chùa Nhật Bản. Câu trả lời có phải là, giống như một cây thông cao, ngôi chùa Nhật Bản – với trụ cột trung tâm giống như thân cây lớn gọi là shinbashira – chỉ đơn giản là uốn cong và dao động trong cơn bão hoặc trận động đất hay sao? Trong nhiều thế kỷ, nhiều người nghĩ vậy. Nhưng câu trả lời không phải là đơn giản bởi vì điều gây sửng sốt là shinbashira thực sự mang không nặng chút nào cả. Trên thực tế, trong một số thiết kế chùa, nó thậm chí còn không nằm trên mặt đất, nhưng bị treo lơ lửng từ trên đỉnh của ngôi chùa – treo lơ lửng xuyên qua giữa tòa nhà. Trọng lượng của tòa nhà được hỗ trợ hoàn toàn bằng mười hai cột bên ngoài và bốn cột bên trong.

And what is the role of the shinbashira, the central pillar? The best way to understand the shinbashira’s role is to watch a video made by Shuzo Ishida, a structural engineer at Kyoto Institute of Technology. Mr Ishida, known to his students as ‘Professor Pagoda’ because of his passion to understand the pagoda, has built a series of models and tested them on a ‘shaketable’ in his laboratory. In short, the shinbashira was acting like an enormous stationary pendulum. The ancient craftsmen, apparently without the assistance of very advanced mathematics, seemed to grasp the principles that were, more than a thousand years later, applied in the construction of Japan’s first skyscraper. What those early craftsmen had found by trial and error was that under pressure a pagoda’s loose stack of floors could be made to slither to and fro independent of one another. Viewed from the side, the pagoda seemed to be doing a snake dance with each consecutive floor moving in the opposite direction to its neighbours above and below. The shinbashira, running up through a hole in the centre of the building, constrained individual storeys from moving too far because, after moving a certain distance, they banged into it, transmitting energy away along the column.

Và vai trò của shinbashira, trụ cột trung tâm là gì? Cách tốt nhất để hiểu vai trò của shinbashira là xem một đoạn video tạo bởi Shuzo Ishida, một kỹ sư kết cấu tại Viện Công nghệ Kyoto. Ông Ishida, sinh viên của ông là ‘giáo sư về Chùa’ vì niềm đam mê của mình để hiểu chùa, đã xây dựng một loạt các mô hình và thử nghiệm chúng trên một ‘bàn rung’ trong phòng thí nghiệm của ông. Tóm lại, shinbashira đã hoạt động như một con lắc cố định rất lớn. Các thợ thủ công cổ xưa, rõ ràng là không có sự trợ giúp của toán học tiên tiến, dường như nắm bắt được các nguyên tắc mà hơn một nghìn năm sau đó được áp dụng trong việc xây dựng tòa nhà chọc trời đầu tiên của Nhật Bản. Điều mà những người thợ thủ công đầu tiên đã tìm thấy bằng thử nghiệm và sai lầm là dưới áp lực, những tầng sàn lỏng lẻo của một ngôi chùa có thể được tạo ra để trượt và độc lập với nhau. Nhìn từ phía bên kia, chùa dường như đang làm một điệu nhảy rắn – mỗi tầng liên tiếp di chuyển theo hướng đối diện với những tầng kế phía trên và dưới. Các shinbashira, chạy qua một lỗ ở trung tâm của tòa nhà, hạn chế các tầng riêng biệt di chuyển quá xa bởi vì, sau khi di chuyển một khoảng cách nhất định, chúng có va đập, truyền năng lượng đi dọc theo cột.

Another strange feature of the Japanese pagoda is that, because the building tapers, with each successive floor plan being smaller than the one below, none of the vertical pillars that carry the weight of the building is connected to its corresponding pillar above. In other words, a five storey pagoda contains not even one pillar that travels right up through the building to carry the structural loads from the top to the bottom. More surprising is the fact that the individual storeys of a Japanese pagoda, unlike their counterparts elsewhere, are not actually connected to each other. They are simply stacked one on top of another like a pile of hats. Interestingly, such a design would not be permitted under current Japanese building regulations.

Một điểm đặc biệt nữa của ngôi chùa Nhật Bản đó là vì tòa nhà được xây dựng theo kiểu tầng kế tiếp nhỏ hơn tầng bên dưới, không có cột trụ dọc nào mang trọng lượng của tòa nhà được nối với trụ cột tương ứng ở trên. Nói cách khác, một ngôi chùa 5 tầng thậm chí không có một trụ cột đi qua tòa nhà để mang các khối kết cấu từ trên xuống dưới. Đáng ngạc nhiên hơn là thực tế là các tầng riêng biệt của một ngôi chùa Nhật Bản, không giống như các bản của chúng ở nơi khác, không thực sự kết nối với nhau. Chúng chỉ đơn giản xếp chồng lên nhau như một đống mũ. Thật thú vị, thiết kế như vậy sẽ không được chấp nhận theo như quy định xây dựng hiện tại của Nhật Bản.

And the extra-wide eaves? Think of them as a tight rope walker balancing pole. The bigger the mass at each end of the pole, the easier it is for the tightrope walker to maintain his or her balance. The same holds true for a pagoda. ‘With the eaves extending out on all sides like balancing poles,’ says Mr. Ishida, ‘the building responds to even the most powerful jolt of an earthquake with a graceful swaying, never an abrupt shaking. Here again, Japanese master builders of a thousand years ago anticipated concepts of modern structural engineering.

Và các mái hiên ngoài rộng? Hãy nghĩ về chúng như là một cột cân bằng của người đi bộ thắt chặt. Khối lượng càng lớn ở mỗi đầu cực, thì càng dễ dàng cho người đi bộ để duy trì sự cân bằng của mình. Điều này cũng đúng đối với một ngôi chùa. Ông Ishida nói: “Với những mái hiên trải rộng khắp mọi phía như các cột cân bằng , tòa nhà đáp ứng được ngay cả cơn lắc mạnh nhất của một trận động đất với sự lắc lư tao nhã, không bao giờ lắc đột ngột. Nhắc lại một lần nữa, các chuyên gia xây dựng của Nhật Bản từ hàng nghìn năm trước dự đoán các khái niệm về kỹ thuật kết cấu hiện đại.

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