Structural and Mechanical Analysis of the Black Widow Spider Web Subjected to Stretching , Expansion and Wind

The web of the black widow is apparently a random spatial arrangement of threads, whichprovides its occupant with housing, means to capture prey and protection. However toensure that these functions are fulfilled, the spider has evolved to adapt the architecture ofthe web so that it would be able to adequately respond to the outer environment and toproperly transmit the stresses within its structure. By performing the structural analysis ofthe web subjected to various external loads, a relationship between the web geometry andmechanical response may be established.For this study, a web model constructed based on data collected from a member of thespecies Latrodectus mactans (southern black widow) is tested under three loadingconditions: uniaxial stretching, expansion in the three main directions and shearing effectsof the wind action. In addition, to determine whether the response of the erratic ensembleof threads is efficient as compared to a more orderly system, a second structureconstructed from elements of equal lengths organized in simplistic pattern is subjected tosimilar tests and results are compared.These tests indicate a complex flow of stresses throughout the network. Unlike theelements in the orderly system, which carry approximately the same amount of load, theindividual response of the threads in the web varies significantly, with some experiencingvery large stresses, while others not being loaded at all. This shows that the high degree ofredundancy in the web allows for multiple possible load paths, redirecting stresses incertain regions of the structure, while maintaining others safe for the spider to continueinhabiting them. However, while certain patterns may be observed in the way load iscarried throughout the web, these tests fail to establish a concrete correlation betweengeometry and stress flow.Thesis Supervisor: Markus J. BuehlerTitle: Professor of Civil and Environmental Engineering