A Performance Assessment of Flood-Damaged Shearwalls

Flood events affect more people than any other form of natural disaster. Flooded structures are partially submerged and then re-dried, which leads to swelling and shrinking over an arbitrary wall height. One repair scheme is to remove the interior cladding (drywall), dry the wood system, and re-install new drywall. This investigation was conducted to evaluate the effects of long-term water exposure on the mechanical properties of oriented strand board (OSB) sheathing and the impact of those changes on the capacity of light-frame shearwalls. OSB was submerged for up to seven days, air-dried and then tested for embedment strength, shear strength through the thickness, and shear modulus. Nine walls were built for the test program. Three were tested at ambient conditions and monotonically loaded in shear to establish the displacement criteria for the quasi-static methods; three walls were tested at ambient conditions (control walls) using a quasistatic loading protocol; and three were submerged in 1 m of water for seven days, re-dried, and then tested using the same quasi-static protocol as the control walls. The results from the OSB material tests showed that most of the material property degradation occurred in the first 48 hr of submersion, for example, the embedment strength was reduced by almost 40 percent after 48 hr and showed no further reduction even with 120 hr of additional soaking. The shearwall test results did not follow the materials’ results -the quasi-static shearwall tests showed that water submersion did not reduce shearwall capacity, the energy absorption of the wall, or change the yield mode. However, shearwall stiffness was reduced, apparently the result of reduced embedment stiffness of the OSB sheathing.