Combining Wood and Viscoelastic Material.
Passive energy dissipation (PED) devices, when incorporated into a structure, work by adding supplemental damping to the system which reduces the structural response during an earthquake or high winds. Viscoelastic dampers are one type of PED device that has emerged as an innovative solution to improving the seismic performance and wind response of structures. Viscoelastic dampers have been especially successful at gaining widespread acceptance by the engineering and construction industries as evidenced by its increased application over the last 10 years. Traditionally, viscoelastic dampers have been used exclusively in steel and reinforced concrete structures; however, there have been some recent studies demonstrating the feasibility of using viscoelastic dampers in woodframe structures. (Dinehart et. al., 1999) These initial studies used dampers consisting of viscoelastic material bonded to steel plates, typical of devices found in steel and concrete structures. To date no attempts have been made to utilize viscoelastic material bonded to wood. The objective of this study is to show that wood and viscoelastic material can be combined effectively and to characterize and quantify the differences between viscoelastic dampers constructed from steel and wood. Tests were conducted on double-lap shear viscoelastic dampers of various thickness constructed with wood and steel to examine the performance under fully reversed cycles of loading. Tests were conducted on matching steel and wood dampers. The dampers were constructed using, 0.2” (5 mm), 0.4” (10 mm), and 0.6” (15 mm) thick VE, self adhesive, material with a shear area of 8 in2 (5161 mm2) per pad or 16 in2 (10323 mm2) per damper. Cyclic tests were conducted at frequencies of 0.1 and 0.5 Hz and strains of 10 and 50 percent. Each damper test was conducted twice for a total 48 tests. A comparison of the dampers constructed with the steel and wood demonstrates several important characteristics. Overall, when subjected to low strains and frequencies, viscoelastic material performed well when integrated with wood. The damper stiffness of the steel and wood dampers was within 4 percent while the energy dissipation capacity was within 8 percent. There were no signs of any degradation of stiffness or energy dissipation capacity during the constant amplitude cycling, indicating that the viscoelastic material maintained a complete bond to wood when subjected to the test parameters stated herein. Further testing will be conducted on these dampers overtime to investigate the bond integrity over time. These tests show that viscoelastic material and wood can be combined effectively. This finding directly leads to an increase in the utilization of viscoelastic material in wood structures. More importantly, these results allow engineers to investigate new applications of combining wood and viscoelastic material. Applications may include improving the dynamic performance of woodframe structures subjected to wind or earthquakes or reducing vibrations of floor systems.
|Main Author:||Lewicki, David E.|
|Other Authors:||Dinehart, David W.|