An investigation was conducted to provide information concerning the flexural behavior of oak pallet shook. This information is to be used in the development of a rational pallet design procedure. The investigation was designed to meet three basic objectives 1) to collect basic data concerning the flexural properties of oak shook, 2) to evaluate the potential of a visual grading system and 3) to investigate the impact of growth and manufacturing defects on the flexural properties of oak pallet shook. Strength, stiffness and selected physical property values were determined and reported. The visual grading system was found to be effective at separating oak pallet shook on the basis of strength and stiffness. A comparison of test results with published procedures indicates strength ratios may be an effective approach to accounting for the influence of growth and manufacturing defects found in oak pallet shook. / M.A.

Pallets are widely used to efficiently store and handle goods and are often subjected to bending and impact loads. The consequences of structural failure of a loaded pallet can include loss of goods, increased labor and equipment costs, and possible severe or fatal injury to humans. - The pallet industry, which annually consumes nearly 20% of all lumber manufactured in the United States, recognized a need for a rational design methodology, based upon engineering principles, to ensure consistent safety and economy in pallets of any geometry. To satisfy this need a cooperative research project between Virginia Tech, the U. S. Forest Service, and the National Wooden Pallet and Container Association was established. The objective of the project was to develop methods to design pallets for strength, stiffness, and durability. A primary expected benefit of the design methodology is to allow comparison of different pallet designs on a performance basis, without the need for extensive physical testing. This dissertation presents the results of this cooperative research project. The developed methodology was computerized (Pallet Design System (PDS)) and is intended to allow pallet manufactures to obtain estimates of the maximum safe load capacity or the member dimensions required to resist known loads. Additionally, the program produces estimates of the durability and cost-per-use for pallets in specific service environments. PDS is limited in scope to pallets with up to four stringers and a maximum of 15 deckboards. Five different load types and four support modes can be analyzed. These include uniformly distributed and concentrated loads, and racked, stacked, and sling support modes. The techniques for estimating the strength and stiffness are based on matrix structural analysis and classical beam theory. The deckboard-stringer joints are modeled as spring elements, the stiffness of which are based upon characteristics of the fastener. Most fasteners commonly used in pallet construction (i.e. threaded nails or staples) can be analyzed. A probabilistic design technique based on mean value methods was applied in PDS to ensure safety in the resulting designs. The safety index was calibrated to pallet designs associated with warehouse load data. The physical properties of the material are estimated using either a modified clear-wood property approach (ASTM D-245 method), or in·graded testing of pallet lumber. The durability estimates are based upon studies of field data and economic analysis. / Ph. D.

Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains viii, 77 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 58-59).

Lateral collapse is a failure mode of wood pallets which most frequently occurs during transportation and handling. The study objective was to develop a simplified procedure for making relative comparisons in the lateral collapse potential of competing pallet designs. A theoretical model was developed to predict the maximum horizontal force a pallet can sustain. A simple equilibrium of forces approach including joint rigidity was used. A lateral load test machine was built which induces and measures the amount of horizontal force required to collapse a pallet. After testing, the model was shown to be accurate when no upper deckboard bending occurred and inaccurate when bending occurred. To account for bending, two multiple regression equations were developed to predict modification factors using a matrix structural analysis program. predicts K-factors for two stringer A closed form solution designs. These K-factors are used to modify the resisting moments generated by the fastened joints. The modified model was shown to slightly overpredict maximum collapse load but did accurately discern differences in relative lateral collapse potential. The ratio of the maximum horizontal load to the vertical load on the pallet provides a means of ranking the potential for lateral collapse. Those designs whose ratios fall between 0.0 and 0.6 are at high risk, from 0.6 but less then 1.0 are at medium risk, and from 1.0 to infinity are at low risk of lateral collapse. These ratios have been calibrated against documented cases of lateral collapse. The factors that influence the lateral collapse potential of a design are stringer aspect ratio, joint characteristics, unit load, and upper deck flexural rigidity. / M.S.

Persons involved in pallet decisions at U.S. grocery distribution centers were surveyed to investigate the degree of material substitution, assess factors influencing pallet material substitution, and quantify consumer perceptions of wood pallets compared to substitutes. A total of 444 questionnaires were mailed nationwide. Underlying reasons for material substitution were investigated through in-depth interviews with 20 respondents. Cost per use was considered by grocery distributors to be the Persons involved in pallet decisions at U.S. grocery distribution centers were surveyed to investigate the degree of material substitution, assess factors influencing pallet material substitution, and quantify consumer perceptions of wood pallets compared to substitutes. A total of 444 questionnaires were mailed nationwide. Underlying reasons for material substitution were investigated through in-depth interviews with 20 respondents. Cost per use was considered by grocery distributors to be the most important factor when choosing a pallet to be sent downstream to their customers. Common advantages of solid wood pallets reported by respondents included: availability, low initial cost, durability/stability (the ability of the pallet to be racked and hold the necessary weight with little deflection), industry standard, ability to exchange, ease of repair. Common disadvantages of solid wood pallets reported by respondents included: easily damaged, short life, high repair and replacement costs, heavy, inconsistent construction, and damages product. Advantages of plastic pallets reported by respondents included: light weight, durability, longer life, true four-way entry, and ability to nest. Plastic pallets were perceived to be superior to wood pallets in terms of overall performance, durability, and recyclability. Although 100 percent of the responding companies use solid wood pallets to ship goods to customers, approximately 20 percent of the companies also use plastic pallets (the dominant substitute pallet material) for this purpose. The common plastic pallet used by respondents was of the twin sheet thermoform type. The primary reason for switching to plastic pallets was perceived overall cost savings resulting from long pallet life. / Master of Science

Today, American industries are in a highly competitive international market. To achieve the competitive edge, manufacturers are demanding excellence from their vendor/suppliers. The pallet and container industries are the suppliers to the other companies. Statistical Process Control (SPC) is one-way to prove to the buyer the quality level of their products. One part of the this thesis is a handbook, which explains a step by step process of implementing an SPC program for the pallet and container industry. In addition, the thesis examines the quality levels of materials that goes into the pallet including the finished product such as raw material, cut-stock, fasteners, and workmanship. The raw material proved quite variable from the different sawmills. The between board variation was greater than the within for both the thickness and width. The cut-stock had less size variation in thickness than width. The workmanship of the finished pallets showed that the number of nail splits and uniformity of deckboard spacing to be a problem. While the number of missing nails, protruding nail points and heads, and the "out of squareness." It was not a problem. The physical characteristics of the fasteners proved extremely variable from one characteristic to another. There are a number of fasteners being produced outside of the NWPCA criteria for wire diameters. The most popular fastener gauges are the 11 and 11.5. In addition, the most popular fastener length is 2.25 and fastener flute number is 4. The MIBANT angle variation is higher for the stiffstock fasteners then the hardened fasteners. / Master of Science

The concept of a bin leasing system represents an effort to use bins more extensively. In a leasing system one inventory of bins would be used by two‘or more annual users. System benefits would be lower per-use costs for the user and the opportunity for the lessor to make a profit. In order to establish a working data base of information, a mailed questionnaire was sent to 333 fruit and vegetable processors. The response rate on the survey was 45%. A typical bin is built of hardwood lumber, lasts about seven years, and costs an average of $36.53. Seventy-eight percent of the owners considered bin repair a problem, 85% thought bin transport was expensive, 96.5% agreed that bins were a significant investment. Overall, 66% considered bin leasing a viable option to ownership. Eastern North Carolina was chosen as the most promising leasing system location. The system will cater to cucumber/pepper processors and sweet potato packers. The method chosen to establish the system is to contract with one or more large companies to supply, on a lease basis, the required replacement bins for future years. A sample system was designed based on cost and revenue information received from area bin owners. Calculations yielded a net present value of $31,056.99 for a 15 year run of the system when using a discount rate of 12.5%. The effects of changes in key variables were analyzed. The most dramatic changes in NPV were due to changes in bin life and per-bin revenues. / Master of Science

Wood pallets serve as interfaces between packaged products and transport vehicles. vertical vibrations are transmitted through pallets into unit-loads. Pallet response to forced vibration affects forces experienced by products. A study was conducted to determine how pallet design influenced the resonant response of a uniformly distributed case goods unit-load. other studies were conducted to develop a pallet section model to emulate the response of three stringer wood pallets to forced vibration. This model was used to investigate the effects of joint stiffness, deckboard EI, and uniformly distributed load level on the resonant response of pallet decks. Pallets were found to lower unit-load resonant frequencies and increase transmissibilities at resonance. Pallet sections constructed with stiff decks and joints were found to have higher resonant frequencies and lower transmissibilities than sections constructed with less stiff deck components. To prevent pallets from elevating acceleration transmitted through unit-loads, pallets should be constructed with the stiffest decks and joints that are economically feasible. / Master of Science

The model used to estimate pallet life in the durability section of PDS is a composite of several computed "factors" which are intended to reflect the impact of design characteristics on pallet durability. The objective of this study was to evaluate the reliability of the estimates of joint performance and the resulting estimates of pallet life relative to the estimated joint performance. A series of delayed fastener axial withdrawal tests were performed on a wide range of pallet fasteners to evaluate the estimates of joint separation resistance that are used in the computation of the F ( 1) factor, the factor for joint separation resistance perpendicular to the pallet deck. This data, in addition to data obtained from previous studies, suggested that the model underestimated the delayed withdrawal performance of threaded nails. An improved relationship was derived for helically threaded, twisted square wire and annularly threaded nails which had the additional advantage of being sensitive to lumber moisture content both at the time of joint assembly and at the time of joint testing. Both the original and the improved relationships were found to grossly overpredict the withdrawal performance of plain shank nails and staples. A series of pallet corner drop tests were performed to evaluate the reliability of the estimates of joint torsional shear resistance that used in the computation of the F(2) factor, the factor for joint separation resistance parallel to the pallet deck. The pallets tested varied by lumber species, number of fastener couples, and fastener stiffness as measured by the MIBANT bend angle. The observed affect of changes in fastener stiffness on pallet diagonal rigidity was found to be accurately reflected in the computed F(2) values. The observed affect of changes in the number of fastener couples on pallet diagonal rigidity was overpredicted in the computed F(2) values. The observed affect of changes in the lumber specific gravity on pallet diagonal rigidity appeared to be overpredicted in the computed F(2) values but this might be due to the fact that the measured pallet distortions were adjusted to account for differences in pallet weights. Pallet weight is specific gravity dependent and adjusting pallet distortion by weight may have reduced the observed affect of specific gravity. It was not possible to statistically confirm a relationship between the estimates of pallet durability relative to pallet diagonal rigidity and observed pallet life. However, such a relationship appears likely. Also, the estimates of pallet durability were found to be conservative. / M.S.

The objective of this project is to develop a methodology to measure and predict the strength and the stiffness of red alder (Alnus rubra) nailed pallet connections subjected to repetitive loading. Joint tests were conducted to define the mechanical properties of bottom block pallet connections. The primary tests were conducted to define the strength and stiffness of joint specimens tested in cyclic lateral loading, using three different side member thicknesses and four types of nails. Also, the influence of other specific variables on joint performance was evaluated including friction, pattern, moisture content, number of nails per joint, specific gravity, and rate of loading. In total, 23 sets of nailed joint specimens, with 15 replications each, were constructed and tested. The use of a reversing cyclic lateral loading procedure permits documentation of the effect of dynamic loading on the load-slip response of the connection. Analysis of the data included the creation of two envelope curves, the initial and the final (stabilized) curve. The data obtained from the two curves was used to find the “best” model for predicting the strength and stiffness of the connections. Four models were identified but only one of these was found useful for prediction purposes. Finally, experimental capacity loads were found to be at least three times greater than the national design specification allowable design loads. / Master of Science