Shake table testing of scaled rammed earth models

Abstract

The ancient method of rammed earth construction has been used in various parts of the globe, including Central and South America, which experience high seismic activity. Although some studies have been done on rammed earth, relatively little is known about the extent of its shear and tensile capacities or practical methods for improving the seismic survivability of these structures.

This research explored not only the effects of dynamic testing on scaled models of a simplified rammed earth house but also two types of reinforcement: a wooden ring beam, and a plastic mesh. The objective was to observe gross failure, catalogue different failure modes and determine which type of reinforcement best preserved the structure. Each model was loaded by a sine wave starting at the fundamental frequency of the model, then increasing both the amplitude and the frequency until failure. Each model was designed at one-third scale with one door opening, 6 inch wall thickness, 3 foot wall height, and a 4 foot by 4 foot plan. All models were tested on a shaketable at the Fears Structural Engineering Laboratory.

Results showed that sine wave base motion, starting at the fundamental frequency, can be an effective dynamic test method. Results also showed that the wooden ring beam was the more effective type of reinforcement. Although the plastic mesh did not serve as structural reinforcement, it still prevented collapse of the rammed earth model.