9DBMC-2002 Paper 050 Page 1 A Performance Assessment of Flood-Damaged Shearwalls RJ Leichti R Staehle & DV Rosowsky Department of Forest Products Oregon State University USA Summary: 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 quasi- static 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. Keywords: Shearwall; monotonic testing; quasi-static testing; timber; durability 1 INTRODUCTION Durability of structures has been the focus of study and design innovation in recent years. The design engineer implements design features and materials that, when used with appropriate construction methods, yields buildings that have long-term durability (TenWolde and Rose 1994). The presumptive design assumption is that the condition of the building system will remain unchanged throughout its service life. However, after a flooding event, there may be a loss in capacity to resist major loading events. Designing for durability requires quantification of the changes in the mechanical properties and resulting performance of the structure. Condition assessment combined with quantified data on the impact of the given material and connection condition provides a vital link to predicting residual structural capacity to resist future loading events given the existing level of damage that is revealed by physical inspection. At present, durability assessment has incorporated only the observed condition of the materials and essentially a go/no-go” basis for replacement. It would be desirable to include the existing levels of damage in the framing and sheathing components in the fragility of residual life assessment of a structure after a natural disaster. Flooding is a natural disaster that affects more people world wide than any other form of natural disaster (Hausmann & Perils 1998). Geo-scientists have reported that floods account for 23 percent of global natural catastrophes but accounted for 67 percent of casualties and caused 53 percent of the economic losses in the US (Munich Re 2001). The insurance industry has many definitions of “flooding” because flooding can originate from many different events and takes many forms. In general, the insurance industry agrees that a flood is a general and temporary inundation of normally dry land from the overflow of inland or tidal water, rapid accumulation of runoff of surface waters, mud flows or mud slides, or waters due to the collapse of shores and retaining systems. Data reported by Hausmann and Perils (1998) showed that most flood events in buildings involve water depths less than 2 m. The number of affected properties can be significant, as in 1993, when approximately100,000 houses were damaged by flooding in the Mississippi River Basin. Thus, flooding represents a potential hazard to the durability and serviceability of residential and industrial buildings.
A Performance Assessment of Flood-Damaged Shearwalls
Jul 01, 2023
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