Nondestructive Evaluation of Historic Hakka Rammed Earth Structures

Abstract

Abstract:The in-service Hakka rammed earth buildings, in the Fujian Province of China, are unique in design and performance. Their UNESCO's inscription as World Heritage sites recognizes their artistic, cultural, social and historic significance. Sponsored by the National Science Foundation of the United States, the authors have examined the engineering values of these buildings in terms of comfortable living at low energy consumption, sustainability and durability. The objective of this study was to better understand the thermo-mechanical and aging responses of Hakka earth buildings under thermal and earthquake loads through nondestructive field evaluation, including full-scale roof truss and floor testing, laboratory testing of field samples and finite element modeling. This paper presents our observations and findings from the field nondestructive evaluations with emphasis on the integrity of the rammed earth outer walls and inner wood structures, as well as the thermal comfort of living in these buildings, while a second paper presents the results from the material characterization of field samples and the structural responses of a representative building under earthquake induced loads through finite element analysis.

Assessing the Rebound Hammer Test for Rammed Earth Material

“…In the present paper, the author explores the possibility of using the well-known rebound hammer test to determine rapidly the compressive strength of in-situ RE walls. It is worth noting that this technique has been tried by Khadka & Shakya [28] and Liang et al [29]; however, the empiric curves of the rebound hammers were established for conventional concretes where the rebound number was more than 20 (corresponding to the compressive strengths more than 10 MPa); for RE material with lower compressive strengths, the calibration curve was not available, so these authors could not predict the compressive strength of the RE specimens measured. That was the reason why in the present study, a new calibration curve was investigated and proposed for RE material.…”

History Made for Tomorrow: Hakka Tulou

“…They find that the posts and beams circling the Tulou distribute loads evenly across the structure and then outward to the rammed earth walls. Even though these load-carrying members are jointed to each other through pinned connection (without a single nail in the entire building), the study reveals that the jointed neighboring members have a high load-sharing effect in a manner similar to a fixed beam and all the surrounding horizontal and vertical members connected to the load carrying beam, have acted in partial unison and restrained the load carrying beam such that the boundary conditions surpass those of a fixed beam, offering extremely high stiffness [6]. Another vital component of sustainability is the Tulou's ability to withstand earthquakes.…”

“…Minoru tracks the temperatures inside every day, year round, using data loggers with the goal of providing the scientific community with empirical proof that Tulou architecture regulates temperature throughout the seasons. Climate data generated both by Liang [6] and Ueda [9] independently do in fact demonstrate that the unique floor plan and thermal mass help the Hakka Tulou moderate temperature and humidity. Furthermore, after a rigorous environmental/sustainability study on the performance of Hakka Tulou, Ueda concluded that Chengqi Tulou built over 300 years ago, and still in-service, was highly ranked in a variety of types of evaluations using modern assessment tools, including the United States Green Building Council's Leadership in Energy and Environmental Design (LEED) guidelines [9].…”

“…Figure 7 is a group photo of some members of the international team researching on Tulous with the Owner of Fuxinglou, Kong Mei-Chang. Surprisingly, radiocarbon dating test of wooden sample from Chengqi Tulou has successfully verified the building's age of over three hundred years [6].…”

“…Figure 8 shows ultrasonic devices being used to measure the strength of a rammed earth wall in a nondestructive manner. Here ultrasonic devices provide data that show the rammed earth walls behave like concrete [6][7][8]. -It looks very comparable.…”