Optimizing Fastener Spacing in Multiple Bolt Wood Connections for Natural Hazard Loading

Recipient Organization
WASHINGTON STATE UNIVERSITY
240 FRENCH ADMINISTRATION BLDG
PULLMAN,WA 99164-0001

Performing Department
COLLEGE OF ENG & ARCHITECTURE

Non Technical Summary
Current wood conection design methodology has been shown to produce unsafe connection designs with the achievable capacities being only 50 - 70 percent of the allowable design loads. This project will quantify the adjustment factors required to ensure a safe design process for wood connections.

Animal Health Component

100%

Research Effort Categories

Basic

(N/A)

Applied

100%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
401	0650	2020	10%
402	0650	2020	10%
511	0650	2020	40%
723	0650	2020	40%

Knowledge Area
401 - Structures, Facilities, and General Purpose Farm Supplies; 511 - New and Improved Non-Food Products and Processes; 723 - Hazards to Human Health and Safety; 402 - Engineering Systems and Equipment;

Subject Of Investigation
0650 - Wood and wood products;

Field Of Science
2020 - Engineering;

Keywords

Goals / Objectives
The objectives of this research project are 1) to determine the optimum spacing between bolts in a row under monotonic and cyclic loading, 2) quantify the effect of spacing between rows of bolts on joint performance up to and including catastrophic failure, and 3) determine the modification factors for design specifications that account for the effect of number of bolts in a row, the spacing between bolts in a row, and the spacing between rows of bolts on the strength of multiple-fastener joints uner reverse cyclic and monotonic loading.

Project Methods
The objectives will be achieved using experimental means. The experimental portion o the project will investigate the spacing between bolts and the spacing between rows of bolts, using wood connection configurations that cover three of the four recognized yield modes in the National Design Specification for Wood Construction.

Progress 12/15/02 to 12/14/06

Outputs
This project found that the optimum spacing of bolts within wood connections is larger than the current design code allows. It was also found that the spacing between rows of bolts directly influences the mode of failure that occurs in the connection. These results are significant in that proposals for changes to the national design code will now be developed to improve the safety of wood buildings. Designers can now modify the design process by adding two new equations that will allow the configurations of the connections to be optimized for either the geometry constraints of the structure or the maximum load capacity possible. In either case, the designer can estimate the actual strength of the connections and compare this value with the design force for the configuration and obtain a measure of how much reserve capacity there is in the connection. Since the connections are the only source of ductility and toughness wood structures have, it is imperative that the designer be able to estimate this margin for safe designs in earthquake prone regions.

Impacts
The expected impact of this research is that the design methodology for wood buildings will be modified to provide a more accurate estimation of the safety margin in the structure with direct design improvements for safety. This is especially true for regions of high earthquake or hurricane risks. The cost impact on construction of wood structures in zero, while the safety improvement is significant.

Publications

No publications reported this period

Progress 01/01/04 to 12/31/04

Outputs
This project has completed the testing stage and is now in the analytical stage. Initial results indicate that the spacing between rows of bolts will dictate the type of failure (row tear out, block shear, or net section). The spacing between bolts within a row dictates the mechanism of yielding (wood crushing or bolt bending) and this spacing directly affects the connection capacity. The analysis will be completed by July, 2005. and the final report will be completed by August, 2005. Currently, 3 technical publications are planned and will be drafted during the summer of 2005 and will be submitted for publication in the Fall, 2005. An additional 2 trade publications are planned to get the information to contractors and designers that would be effected by the results.

Impacts
This work will result in improved reliability of connection design and an associated improvement in the reliability of wood structures as a whole.

Publications

No publications reported this period

Progress 01/01/03 to 12/31/03

Outputs
The experimental investigation into the optimum spacing for bolts in a row is currently underway. This work should be complete within the first quarter of 2004. The test fixtures for the experimental investigation to optimize the spacing between rows of multiple-bolts are being fabricated and the materials to fabricate the connections has been defined and ready to request bids for supply. The connections will be fabricated by June, 2004 and testing of the connections will be completed by Fall, 2004.

Impacts
This work will result in improved reliability of connection design and an associated improvement in the reliability of wood structures as a whole.

Publications

No publications reported this period