A vast amount of goods and products are transported in bulk as palletized unit loads, where the pallet is the base of the unit load. Material handling systems represent the physical environment in which unit loads are transported through supply chains. Material handling systems include different transportation modes and storage conditions, many of which are well researched. While industrial forklifts are paramount to material handling systems, the physical effect they have on load systems is not well understood. The weight of the unit load causes the pallets to deflect, and previous research has revealed that forklift vibration amplifies pallet deflection. The effects of forklift vibration on pallet deflection are not considered in international standards used to determine pallet load capacities. Standards such as ISO 8611 and ASTM D1185 provide deflection limits that are used to determine pallet load capacities, yet there is a lack of understanding and justification on these deflection limits related to forklift support conditions. A comprehensive understanding of the effects of forklift vibration on unit load performance is necessary to produce accurate and safe load capacity ratings. In this research, two studies were completed to gain further understanding on unit load performance and stability in forklift handling conditions. The first study evaluated pallet deflection and unit load stability of unbound unit loads designed with a 20 mm. performance limit (ISO 8611, 2011). Common forklift handling factors were investigated and included fork tine angle (level and 4-degree incline) and pallet orientation (racked across the width and across the length). The results showed that the dynamic environment of forklift handling created unstable unit loads. The second study of this research project investigated unit load performance against unit load design factors of load capacity (500 lbs., 750 lbs., 900 lbs.) and box size (8 in., 12 in., 16 in.). The results showed that unit load instability occurred at all load levels and all box sizes. Additionally, an increase in box size decreased load bridging for unit loads under fork tine support conditions. Furthermore, the time to instability was used to calculate projected forklift travel distances that can be used to further optimize material handling systems. / Master of Science / Many goods and products are transported across the world every day using a multitude of transportation modes and systems. The use of pallets to transport goods in bulk optimizes efficiency of the supply chain system. The physical transportation environment pallets are exposed to is used to determine their load capacity. While pallets are commonly handled by industrial forklifts, the environment the forklift creates for the pallet is not well understood. The mechanical stressors that forklifts create play a vital role in pallet performance and have been found to cause unit load instability.  Vibration represents one mechanical stressor that creates a hazard for material handling.  The goal of this research was to evaluate the performance of pallets in relation to the vibration imposed by industrial forklifts.   Previous studies measured forklift vibration and developed test procedures to replicate the forklift handling environment in a laboratory setting. Previous research investigated unit load performance where the pallet load capacity was determined using a 4.5-degree performance limit (ISO 8611, 2021). This study expanded on previous research by further investigating unit load performance against various load capacities and design parameters. This study included two experiments. The first experiment investigated the effect of common material handling factors on unit loads designed with a 20 mm. performance limit (ISO 8611, 2011). The second experiment investigated the effect of unit load design parameters such as load capacity and box size on unit load performance.   This study found that forklift vibration creates a hazardous environment where pallet deflection combined with magnified vibration caused unbound unit loads to become unstable. The data also revealed that larger boxes decrease unit load bridging in the fork tine support condition. Additionally, projected forklift travel distances were determined for various pallet testing standards. This data can be used to further optimize material handling systems.

The unit load is the form of most commercial and industrial products during storage and distribution. A simple form of a unit load, a palletized bulk bin is commonly used to transport fruit and vegetables from the point of harvest to processing facilities. These vibration sensitive products are often subjected to damaging vibrations during this period. Most damage occurs during the large accelerations associated with resonance, which occurs when the natural frequency of the unit load matches the input frequencies commonly encountered during transportation. A computer model, called RoPUL (resonance of palletized unit loads), of a palletized bulk bin loaded with fruit, was developed using finite element analysis techniques. Unit loads consisting of palletized bulk bins of apples and peaches were tested and RoPUL was found to accurately predict the resonant frequencies of these loads. Using RoPUL, the effects of product mass, container design, and pallet design on natural frequencies can be analyzed. As the input frequencies of most transportation modes is well documented, RoPUL can be used to help design a unit load to better protects vibration sensitive products during shipment. / Ph. D.

Corrugated paper boxes are the predominant packaging and shipping material and account for the majority of packaging refuse by weight. Wooden pallets are equally predominant in shipping, transportation and warehousing logistics. The interaction between these two components is complex and unexplored leaving industry to compensate with outdated component specific safety factors. Providing a focused exploration of the box and pallet interaction will open the door for holistic design practices that will reduce cost, weight, damage, and safety incidents. This study was separated into four chapters exploring different aspects of the corrugated box to pallet interaction. The first chapter evaluates the support surface provided by a pallet consists of deckboards spaced perpendicular to the length of the pallet. The resulting gaps between deckboards reduce the support to the box. Gaps were limited to 55% of box sidewall length for practical reasons. The effect of gaps was significant and produced a nonlinear reduction in box strength. Small boxes were more susceptible to gaps than larger boxes. Moving the gap closer to the corner increased its effect while increasing the number of gaps did not increase the effect. A modification to the McKee equation was produced that was capable of predicting the loss in strength due to gaps. The equation is novel in that is modifies a widely used equation and is the first such equation capable of handling multiple box sizes. This study also has practical implications for packaging designers who must contend with pallet gap. Chapter 2 explores the relationship between deckboard deflection and box compression strength. Testing found that reducing the stiffness of the deckboard decreases the compression strength of the box by 26.4%. The location of the box relative to the stringer also had varying effects on the box strength. A combination of deckboard stiffness and gaps produced mixed with results with gaps reducing the effect of stiffness. It was observed that lower stiffness deckboards not only deflect but also twist during compression. The torsion is suspected to have a significant influence on compression but further exploration is needed. The third chapter tests the effect of box flap length on box compression strength under various support conditions. Variables included four flap lengths, gaps between deckboards, low stiffness deckboards, column stacking and misaligned stacking. The results show that the box flaps can be reduced by 25% with no significant effect of box strength under any support condition tested. Furthermore, the box flap can be reduced by 50% with less than 10% loss in compression strength under all scenarios. These results have significant sustainability implication as 25% and 50% reduction in box flap reduce material usage by approximately 12% and 24%, respectively. In the fourth and final chapter, the theory of beam-on-elastic foundation is applied to deckboard bending and corrugated boxes. In this model the corrugated box acts and the foundation and the deckboard is the beam. Rotational stiffness, load bridging, and foundation stiffness changes required the development of novel testing solution and model development. The model was capable of predicting the distribution of force along the length sidewall but was not capable of predicting the ultimate strength of the box. The model developed in the study will be applicable in determining potential weakness in the unit load in addition to optimizing those that are over designed. These four chapters represent a considerable contribution of applicable research to a field that relied on outdated safety factors over thirty years. These safety factors often lead to costly over design in an industry where corrugated box and pallets volumes make event the smallest improvements highly beneficial. Furthermore, this research has opened the door for significant additional research that will undoubtedly provided even greater economic and sustainability benefits. / Ph. D.

The global supply chain has been built on the material handling capabilities provided by the use of pallets and corrugated boxes. Current pallet design methodologies frequently underestimate the load carrying capacity of pallets by assuming they will only carry uniformly distributed, flexible payloads. But, by considering the effect of various payload characteristics and their interactions during the pallet design process, the structure of pallets can be optimized. This, in turn, will reduce the material consumption required to support the pallet industry. In order to understand the mechanical interactions between stacked boxes and pallet decks, and how these interactions affect the bending moment of pallets, a finite element model was developed and validated. The model developed was two-dimensional, nonlinear and implicitly dynamic. It allowed for evaluations of the effects of different payload configurations on the pallet bending response. The model accurately predicted the deflection of the pallet segment and the movement of the packages for each scenario simulated. The second phase of the study characterized the effects, significant factors, and interactions influencing load bridging on unit loads. It provided a clear understanding of the load bridging effect and how it can be successfully included during the unit load design process. It was concluded that pallet yield strength could be increased by over 60% when accounting for the load bridging effect. To provide a more efficient and cost-effective solution, a surrogate model was developed using a Gaussian Process regression. A detailed analysis of the payloads' effects on pallet deflection was conducted. Four factors were identified as generating significant influence: the number of columns in the unit load, the height of the payload, the friction coefficient of the payload's contact with the pallet deck, and the contact friction between the packages. Additionally, it was identified that complex interactions exist between these significant factors, so they must always be considered. / Doctor of Philosophy / Pallets are a key element of an efficient global supply chain. Most products that are transported are commonly packaged in corrugated boxes and handled by stacking these boxes on pallets. Currently, pallet design methods do not take into consideration the product that is being carried, instead using generic flexible loads for the determination of the pallet's load carrying capacity. In practice, most pallets carry discrete loads, such as corrugated boxes. It has been proven that a pallet, when carrying certain types of packages, can have increased performance compared to the design's estimated load carrying capacity. This is caused by the load redistribution across the pallet deck through an effect known as load bridging. Being able to incorporate the load bridging effect on pallet performance during the design process can allow for the optimization of pallets for specific uses and the reduction in costs and in material consumption. Historically, this effect has been evaluated through physical testing, but that is a slow and cumbersome process that does not allow control of all of the variables for the development of a general model. This research study developed a computer simulation model of a simplified unit load to demonstrate and replicate the load bridging effect. Additionally, a surrogate model was developed in order to conduct a detailed analysis of the main factors and their interactions. These models provide pallet designers an efficient method to use to identify opportunities to modify the unit load's characteristics and improve pallet performance for specific conditions of use.

The optimization of pallet design in today’s competitive supply chain is imperative to reduce costs and improve sustainability. With over two billion pallets in circulation in the United States, most packaged products are handled using unit loads and the interactions between the unit load components are not being considered in the pallet design process. This study aims to investigate the effect of the interlocking of layers and the pallet stacking patterns on pallet bending. This effect is part of a greater encompassing observed behavior known as load bridging, where a redistribution of the stresses on the pallet dependent on the characteristics of the load is generated. The bending of the unit load was measured under four common support conditions, warehouse racked across the width and length, fork tine support across the width and floor stacking. Five different pallet stacking patterns were then analyzed, comparing different interlocking levels, from column stacking to fully interlocking. It was identified that interlocking the layers causes a reduction in pallet deflection of up to 53% versus column stacking, and is more significant on lower stiffness pallets. The stacking patterns and interlocking levels also presented an effect on pallet deflection, albeit only for very low stiffness pallets when supported on its weakest components. A relationship between the observed results and a ratio of load and pallet stiffness was conducted, suggesting that when the load on the pallet is not significantly high in relation to the stiffness, load bridging won’t be observed. These results provide a guideline on improving pallet design and help furthering the understanding of the load bridging effect. / Master of Science / The optimization of pallet design in today’s competitive supply chain is imperative to reduce costs and improve sustainability. With over two billion pallets in circulation in the United States, most packaged products are handled using unit loads and the interactions between the unit load components are not being considered in the pallet design process. This study aims to investigate the effect of the interlocking of layers and the pallet stacking patterns on pallet bending. This effect is part of a greater encompassing observed behavior known as load bridging, where a redistribution of the stresses on the pallet dependent on the characteristics of the load is generated. Tests were conducted to measure the pallet bending performance under common scenarios, evaluating the effect of five different pallet stacking patterns. It was identified that when the layers of a unit load are interlocked, the pallet presents lower deflection (up to 53%). A relationship between the observed results and a ratio of load and pallet stiffness was conducted, suggesting that when the load on the pallet is not significantly high in relation to the stiffness, load bridging won’t be observed. These results provide a guideline on improving pallet design and help furthering the understanding of the load bridging effect.

Pallets are the foundation of unit loads and supply chains. They provide a way to store and transport products in an efficient manner. The load capacity of pallets greatly depends on the type of packages carried by the pallet; however, current pallet design methods do not consider the effect of packages on the load carrying capacity of the pallet. This results in excessive use of materials which reduces the sustainability of unit loads, drives costs up, and creates issues for people in the supply chain. The objective of this study was to investigate the effect of a corrugated box's size and head space on pallet deflection and stress distribution on the top of the pallet as a function of pallet stiffness across multiple pallet support conditions. Data analysis identified that box size had a significant effect on the deflection of the pallet. This effect was only significant for warehouse racking across the width and length support conditions. As much as a 53% reduction in pallet deflection was observed for high stiffness pallets supporting corrugated boxes with 25.4 mm headspace when the size was increased from small to large. Meanwhile, no significant effect of box size was found for other supports. The effect of headspace was significant in some scenarios but inconsistent thus more investigation with a larger sample size is recommended. In addition, redistribution of vertical compression stresses towards the supports was observed as a function of the increasing box size. The increased concentration of compression stresses on top of the supports and the resulting lower pallet deflection could significantly increase the actual load carrying capacity of some pallet designs. / Master of Science / Pallets are the foundation of unit loads and supply chains. They provide a way to store and transport products in an efficient manner. The load capacity of pallets greatly depends on the type of packages carried by the pallet; however, current pallet design methods do not consider the effect of packages on the load carrying capacity of the pallet. This results in excessive use of materials which reduces the sustainability of unit loads, drives costs up, and creates issues for people in the supply chain. The objective of this study was to investigate the effect of a corrugated box’s size and head space on pallet deflection and stress distribution on the top of the pallet as a function of pallet stiffness across multiple pallet support conditions. The data from the study identified that box size does have an effect on the deflection of the pallet but, it was only found to be significant for the warehouse racking supports. The highest reduction in pallet deflection was 53% on the high stiffness pallets carrying corrugated boxes with 25.4 mm of headspace as the boxes increased in size. The other support conditions showed no significant effect of the box size. Headspace showed some significant effect in some conditions but was found inconsistent, therefore an investigation with a larger sample size is recommended. In addition, the redistribution of vertical compression stresses towards the supports was observed as a function of increasing box size. This increase in stress on the supports resulted in lower pallet deflection that could significantly increase the actual load carrying capacity of some pallet designs.

Pallets are a critical component of logistics infrastructure. Approximately 1.9 billion pallets are used each year in the United States for transportation of goods, from raw materials to finished products. Solid wood pallets represent 90% to 95% of the pallet market. To run their operations, wood pallet companies deal with suppliers, customers, and other supply chain components. Each of the steps is important to deliver the right products, with the required quality, and in a timely fashion. However, there is little research about the industry's supply chain practices. The objective of this research is to increase the understanding of the U.S. wood pallet manufacturing industry, its supply chain management practices, and factors affecting the supply chain management processes. To accomplish the research objectives, a nationwide mail survey of wood pallet manufacturers was carried out. In total 1,500 companies were sent questionnaires and the response rate was 14%. A model for supply chain success factors was developed based on previous research and was analyzed using the results from the survey. Results of the survey provide an up-to-date profile of the US wood pallet industry. It was found that pallet production per company was 727,229 units on average during 2009. Out of the 1500 respondents, 38.6% indicated they were medium-sized companies (20 to 99 employees) and 53.9% small companies (1 to 19 employees). Thirty five percentage of respondents indicated that their sales were less than one million dollars and 43% from one to five million dollars. Also, 45% of respondents were involved in pallet recycling or repair, and these companies indicated that, on average, 42% of the material in a recycled pallet is, in fact, new material. Regarding Supply Chain practices, close to three-quarters (73.1%) of respondents sold their products directly to customers and the order lead time for raw materials to shipment was 1 to 10 days for 81.9% of companies. The most important factors for purchasing decisions are availability, cost, and reliability of supplier (all rated 4.4 in an importance scale from 1 to 5, respectively). Respondents' answers suggest a preference to work with domestic materials (rated 4.3); however, respondents also indicated that there is currently a high level of competition for raw materials (rated 4.3). Results also indicated that information technology (IT) appears to receive little attention from wood pallet manufacturers, given that the importance of items in this area were rated relatively low, especially the use of internet for purchasing and training in IT (rated 2.2 and 2.1, respectively). Lastly, 86.0% of respondents did not believe that their customers would be willing to pay a premium for environmentally certified pallets, citing cost as the major barrier for a higher demand of these products. Also, a theoretical framework of supply chain management was designed, developed, and tested with factor analysis, allowing identification of seven factors in the wood pallet supply chain: (1) environmental uncertainty, (2) information technology, (3) supply chain relationships, (4) value-added process, (5) supply chain management performance, (6) business management, and (7) customer satisfaction. Relationships between factors were tested using multiple linear regression. Results show that value-added process positively affects supply chain relationships, and these in turn are positively correlated to supply chain management performance and customer satisfaction. Results from this research are useful for the industry to formulate a well-informed supply chain management strategy by understanding the connections between the different supply chain management practices and the business performance and customer satisfaction. The information presented is also useful for organizations supporting the wood pallet industry to design more effective assistance and educational programs. / Master of Science

Research on unit load stability aids manufacturing facilities in selecting the most efficient load stabilizer when shipping their products to market. This study's objective was to compare the performance a variety of different commonly used load stabilizers to stretch hooding. Stretch hooding is a method of load stabilization in which a tubular film is heat sealed at the top, stretched by four mechanical arms to a desired width, pulled down over the unit load. The film is slowly released as the arms descend, and is released under the pallet. 400ga stretch hooding, 80ga and 63ga stretch wrap and strapping were tested. Twenty unit loads for both vibration and impact testing were used, with 5 replications per load stabilizer. Container displacement and pallet-container displacement were measured, and the number of tares in the load stabilizer film, on the corners of the test units, after testing, was noted. Container displacement was significantly greater during impact testing than in vibration testing. Strapping was the most effective stabilizer during vibration testing because of its ability to restrict vertical displacement. The stretch hooding was the most effective stabilizer during impact testing because of its ability to restrict horizontal displacement. / Master of Science

A major upgrade to the wastewater treatment plant in Saskatoon, Canada significantly improved the final effluent quality. Consequently, the relative impact of the citys urban runoff on the receiving stream, the South Saskatchewan River, has increased. Moreover, at the inception of the study, pending amendments to provincial legislation governing urban runoff were such that urban runoff would no longer be automatically exempt from regulation. In response to this impending change, which has since been made, Saskatchewan Environment initiated a study to examine the water quality of the urban runoff in Saskatoon, because little had been done to date involving the water quality of urban runoff in Saskatchewan.<p>The field program was conducted in 2001 and 2002 to collect representative urban runoff water quality and flow rate data from four different land uses: newer residential, older residential, commercial, and industrial. Three characterizations of the water quality were developed on the basis of the data collected: Site Mean Concentration (SMC), multiple variable regression models, and the unit load. The SMC results indicate that the average water quality parameter concentrations in Saskatoon are greater than those from NURP, the updated U.S. nationwide urban runoff database, and from Vancouver, Canada, but are similar to those from Wisconsin. The regression analyses indicate that the rainfall depth is the most frequently significant parameter in the prediction of event loads. The unit load analyses indicate that the commercial catchment produces the most pollutant load per unit area. Comparison of the methods indicates that the SMC can be used to estimate longer term urban runoff loads, in lieu of the more complex regression method.<p>Heavy metals, pesticides, and fecal coliforms were detected in the urban runoff at concentrations that exceed guideline values. Further investigation is recommended.<p>In comparison to the loads discharged by local point sources, urban runoff contributes larger total suspended solids (TSS) and total Kjeldahl nitrogen (TKN) loads to the South Saskatchewan River. The load of COD to the river is comparable to that of the Saskatoon Wastewater Treatment Plant (WWTP). The total phosphorus load contributed by urban runoff is slightly smaller than that of the WWTP. Considering the relative load of TSS from urban runoff to the WWTP and the potential for other, more toxic pollutants to adsorb to the TSS, sediment controls should be implemented at all levels of development. Further examination of urban runoff with specific emphasis on spring and winter runoff is recommended.

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