Material characterization and structural response under earthquake loads of hakka rammed earth buildings

Hakka Tulou are rammed earth buildings that have survived material aging, natural weathering and earthquakes for hundreds of years. Previous paper has reported our observations and findings from nondestructive evaluations in field with focus on the integrity of the rammed earth outer walls and inner timber structures as well as the thermal comfort of living in these buildings [1]. This paper presents the structural response of Tulou buildings under earthquake loads using material data from field and employing finite element (FE) analysis program. The material characterization included scanning electron microscopy and compression strength/modulus of rammed earth samples and wall reinforcements, revealing their high strength and durability. The FE analyses were conducted on unreinforced Huanji Tulou as per the simplified lateral force analysis procedure defined by the Code ASCE-7 under three types of wall conditions: 1) unreinforced rammed earth outer wall only, 2) reinforced rammed earth outer wall without inner wooden structures, and 3) unreinforced rammed earth outer wall with inner wooden structures. The FE modeling revealed that the existing large crack in the outer earth wall of Huanji Tulou would not have developed under a strong earthquake load if the earth walls were reinforced. Furthermore, the high volume rammed earth wall integrated with inner timber structures would have offered the building unique earthquake resistance.