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2006-2008 Research Projects: Coastal Natural Hazards

Project: Predicting Wind Uplift Failures Of Wood-Framed Residential Roof Structures Using Influence Functions And Database Assisted Design

Principal Investigators

David Prevatt, Clemson University

Project Number

R/CE-7

Research Description

The focus of this research is to demonstrate and apply a Database-Assisted Design Method to a single-family wood-framed house to demonstrate the effectiveness of the technology in making homes less vulnerable to hurricane damage.

Objectives include: (1) Wind Tunnel Analysis – Analyze wind tunnel results from Clemson Standard Models (CSM) from a previous experiment and obtain the time series wind pressure data for gable roof buildings and a typical residential structure, located in suburban terrain. Generate time histories for these buildings for wind directions at 10 degree intervals; (2) Data Gathering – Inspect the structural framing of typical gable-roofed residential structures to determine typical construction practices in South Carolina. This study will categorize the roof structures by age, location and building size and structural system (roof truss with bottom chords, scissors trusses, or stick-built) to identify typical construction practices in the state. Develop a survey methodology to determine from practicing engineers and building official how they actually apply ASCE 7 design provisions to residential wood-framed construction; (3) Structural Tests – Develop the influence surface coefficients for uplift loads on the roof-to-wall connections using a structural model of a gable roof house selected from objective 2 above. We will determine the influence coefficients using load cells and displacement transducers to measure critical parameters of the behavior of roof-to-wall connections under uplift load; (4) Generate time-histories of total uplift wind load on critical locations of the roof structure (i.e. the roof-to-wall connection, sheathing to top chord connection) by integrating the wind load on roof weighted by influence functions developed in objective 3; (5) Compare the results of aggregated uplift loads at critical locations of the roof structure with design wind loads determined using ASCE 7-02 wind design procedure and the tributary area analogy. By comparing the two results, we will develop a relationship factor between the two methods.

An innovative design methodology will be formulated that generates uplift loads on critical roof components including the roof-to-wall connection and sheathing to roof-truss using wind tunnel data and influence functions. The proposed work is designed to produce results that will benefit coastal homeowners, builders, and the insurance industry. The research product will be an important reference tool for wind-engineering researchers and low-rise building structure designers, and will provide the foundation for an entirely new design paradigm – Data-Assisted Wind Load Design. Once the methodology is established, the investigator plans to explore influence functions (coefficients which affect the strength of roof-to-wall connections) and uplift loads on more complex roof shapes, such as the intersecting hipped and gable roof systems that are commonly used in many coastal communities.

Contact for Questions

David Prevatt (prevatt@clemson.edu)