Non-linear behaviour and failure mechanism of bamboo poles in bending

The adoption of bamboo poles in construction can support the reduction of carbon dioxide emissions generated by the manufacture of conventional structural elements produced from unsustainable industrialised materials. This research focuses on the study of the nonlinear softening behaviour and failure mechanism of bamboo poles in bending through a series of experimental tests on Moso (Phyllostachys pubescens) bamboo and Finite Element simulations supported by digitisation techniques. The results indicate that this nonlinear behaviour is caused by the incremental development of cracks at the locations where the circumferential tensile capacity of bamboo is exceeded leading to the eventual failure of the pole. Also, the simulations in this study suggest that reinforcing bamboo poles with pretensioned stainless steel bands is ineffective in counteracting the development of significant circumferential tensile stresses and the associated longitudinal cracks. More generally, this work highlights the challenges and limitations of applying traditional methods of structural testing and design for manufactured components to a highly variable natural structural element and speculates whether modern digital technologies can be adopted to manage more effectively the effects of this inherent variability

Seismic overturning of rocking structures with external viscous dampers

Numerous structures exhibit rocking behavior during earthquakes and there is a continuing need to retrofit these structures to prevent collapse. The behavior of stand-alone rocking structures has been thoroughly investigated, but there are relatively few theoretical studies on the response of retrofitted rocking structures. In practice, despite the benefits of allowing rocking motion, rocking behavior is typically prevented instead of optimized. This study characterizes the fundamental behavior of damped rocking motion through analytical modeling. A single rocking block analytical model is utilized to determine the optimal viscous damping characteristics which exploit the beneficial aspects of rocking motion while dissipating energy and preventing overturning collapse. To clarify the benefits of damping, overturning envelopes for the damped rocking block are presented and compared with the pertinent envelopes of the free rocking block. Preliminary experimental work to verify analytical modeling is also presented. Finally, the same principles of controlling rocking behavior with damping are extended to a particular class of rocking problems, the dynamics of masonry arches. A pilot application of the proposed approach to masonry arches is presented

Towards a unified description of rocking structures

Numerous studies on the rigid rocking block have generated a wealth of knowledge about rocking behavior. However, evaluation of more complex rocking systems requires the derivation and solution of complicated equations of motion. This paper investigates the possibility of a unified description of several rocking systems through investigation of rocking mechanisms which describe the masonry wall and the masonry arch. Effective rocking parameters are derived for each of these structures, and the similarity of the rocking behavior is discussed. The error of the proposed approximation, which defines the limitations for this approach, is quantified for the example structures considered. Where appropriate, a unified description of rocking would allow the use of rocking spectra, which would be useful to readily predict the response of a wide array of rocking structures

Dynamically equivalent rocking structures

Predicting the rocking response of structures to ground motion is important for assessment of existing structures, which may be vulnerable to uplift and overturning, as well as for designs which employ rocking as a means of seismic isolation. However, the majority of studies utilize a single rocking block to characterize rocking motion. In this paper, a methodology is proposed to derive equivalence between the single rocking block and various rocking mechanisms, yielding a set of fundamental rocking parameters. Specific structures that have exact dynamic equivalence with a single rocking block, are first reviewed. Subsequently, approximate equivalence between single and multiple block mechanisms is achieved through local linearization of the relevant equations of motion. The approximation error associated with linearization is quantified for three essential mechanisms, providing a measure of the confidence with which the proposed methodology can be applied. © 2014 John Wiley & Sons, Ltd