The broad objective of this research is to examine the relationship between the cellular micromechanical environment and disease progression in cancer. The mechanical stiffness of cancerous tissue is a key feature that distinguishes it from normal tissue and thus facilitates its detection clinically. While numerous inroads have been achieved toward elucidating molecular mechanisms that underlie diseases such as cancer, quantitative characterization of associated cellular mechanical properties and biophysical attributes remains largely incomplete. To this end, the present research provides insight into the following questions: (1) What is the effect of extracellular matrix (ECM) stiffness and architecture on internal cancer cell rheology and cytoskeletal organization? (2) What are the integrated effects of ECM stiffness and cell metastatic potential on the intracellular rheology and morphology of breast cancer cells? (3) What are the integrated effects of ECM stiffness, ECM architecture, and cell metastatic potential on the motility of breast cancer cells? To examine these phenomena, the present research utilizes a multidisciplinary engineering approach that integrates experimental rheology, theoretical mechanics, confocal microscopy, computational algorithms, and experimental cell biology. Briefly, genetically altered cancer-mimicking cells are cultured within synthetic ECMs of varying mechanical stiffness and structure, where they are then observed using time-lapsed confocal microscopy. Image analyses and computational algorithms are then employed to extract measures of cell migration speed and intracellular stiffness via particle-tracking microrheology techniques. Major results show that ECM stiffness elicits an intracellular mechanical response only within the framework of physiologically relevant matrix environments and that a key cell-matrix attachment protein (the integrin) plays an essential role in this phenomenon. Additional results indicate that a well-known breast cancer-associated biomarker (ErbB2) is responsible for sensitizing mammary cells to ECM stiffness. Finally, results also show that a switch in ECM architecture significantly hinders the migratory capacity of ErbB2-associated cells, which may explain why the ErbB2 biomarker is detected with much higher frequency in early stage breast cancer than in later stage invasive and metastatic cancers. In total, these findings inform the fields of mechanobiology and cancer biology by systematically linking cell rheology, cell motility, matrix mechanics, and disease progression in cancer. / text

Doctor of Philosophy(PhD) / Soil Stiffness is an important parameter for any geotechnical engineering design. In laboratory tests it can be derived from stress-strain curves or from dynamic measurement based on wave propagation theory. The second method is a more accurate and direct method for measuring stiffness at very small strains. Until now dynamic measurements have usually been obtained manually from the triaxial test. Attempts have been made to automate the procedure but have apparently failed due to the high level of variability in dynamic measurements. Moreover, triaxial tests of soil can be very lengthy and manual dynamic measurements can be very tedious and impractical for long stress-path tests. In this research a computer program has been developed to automate the stiffness measurement (using bender elements) based on the cross- correlation technique. In this method the program records all the peaks and corresponding arrival times in the cross-correlation signal during the test. The stiffness is calculated and displayed on the screen continuously. The Bender Element enabled to get the small strain shear modulus. An arbitrary “Chirp” waveform of 4 kHz frequency was used for this purpose. Subsequently Bender Element test results were checked by ‘Sine’ waveforms of frequencies 5kHz to 20kHz, as well as by manual inspection of the arrival time. This thesis discusses the method and some of the difficulties in truly automating the process. Finally some results from a number of stress path tests on uncemented and cemented calcareous sediments are presented. Bender elements have been used by many researchers to determine the shear modulus at small strain. Most previous studies have used visual observation of arrival time, which is time consuming and often requires some judgement from the operator. This thesis will describe the use of cross-correlation as a method for automation of Gmax measurement. Cross-correlation has been claimed to be unreliable in the past. However, it will be shown that provided several peaks in the cross-correlation signal are monitored it is possible to follow the variation of Gmax throughout consolidation and shearing. The measurement can be made at regular intervals within the software controlling a stress-path apparatus. Details of the apparatus used and practical considerations including selection of waveform and frequency are discussed. A series of drained cyclic triaxial tests was carried out on artificially cemented and uncemented calcareous soil of dry unit weights 13, 15, and 17 kN/m3 and sheared with constant effective confining stress 300 kPa. Gypsum cement contents of 10%, 20% and 30% of the dry soil weight were used. In addition a series of stress path tests were performed on Toyuora sand samples. Results will be presented for two uncemented and one cemented sand. In addition to the bender elements, all tests had internal instrumentation to monitor axial and lateral strains. Results will be presented for Toyura sand to show that the measurements are consistent with those obtained by other methods. Results will also be presented for carbonate sand subjected to a wide range of stress paths. Finally, results will be presented for the carbonate sand cemented with gypsum. The degradation of Gmax of the cemented soil subjected to variety of monotonic and cyclic stress-paths is presented. Analysis of the results includes assessment of the factors influencing Gmax for uncemented sand. Preliminary analysis indicates that in order of importance these are the mean effective stress, the stress history, void ratio and stress ratio. For cemented sand, Gmax is initially constant and independent of stress path. After yielding the modulus degrades, becoming increasingly stress level dependent and eventually approaches the value for uncemented sand. Factors influencing the rate of degradation are discussed. For the Toyuora sand samples the effects of end restraint on the stress-strain response at small strains were investigated. The conventional method of mounting triaxial specimen has the effect of introducing friction between sample and end platen during a compression test. This inevitably restricts free lateral movement of the specimen ends. Frictional restraint at the sample ends causes the formation of 'dead zones' adjacent to the platens, resulting in non-uniform distribution of stress and strain (and of pore pressure if undrained). On the other hand the specimen with 'free' ends maintain an approximate cylindrical shape instead of barrelling when subjected to compression, resulting in a more uniform stress distribution.

A rigidez a pequenas deformações e sua respectiva degradação são informações cruciais para se determinar parâmetros de projeto mais precisos. Apesar de sua importância, estas propriedades não são usualmente investigadas. Assim, o objetivo do presente trabalho foi de estudar a degradação da rigidez da areia de Osório artificialmente cimentada por meio de diferentes métodos de laboratório. A escolha por um material cimentado ocorreu baseada em apelos ambientais, econômicos e técnicos. O presente estudo também objetiva desenvolver e validar um sistema de Bender Elements (BE), que forneça resultados confiáveis na avaliação da degradação do solo. Pares de BE foram construídos para serem utilizados em testes de bancada e ensaios triaxiais. Além disso, um amplificador de sinal, assim como scripts foram desenvolvidos especialmente para a interpretação dos dados no domínio do tempo. O aumento da rigidez durante o processo de cura foi avaliado por meio da velocidade de onda cisalhante, medida pelos BE e por um equipamento de ondas ultrassônicas (UPV), sob condições de pressão atmosférica. Ensaios de degradação da rigidez, por sua vez, foram conduzidos em uma câmara triaxial especialmente modificada para a instalação dos BE Após sete dias de cura atmosférica, os corpos-de-prova foram cisalhados no equipamento triaxial modificado enquanto mudanças de rigidez eram obtidas por meio de testes de BE e instrumentação interna. Os resultados demonstraram que o sistema BE desenvolvido foi bem sucedido na avaliação da rigidez do solo estudado. A comparação entre os resultados do BE e UPV não foi conclusiva no que se refere à dependência do solo à frequência. A degradação do módulo obtida por ambas as metodologias apresentou uma adequada concordância para o corpo-deprova com menor quantidade de cimento. Módulos obtidos por BE foram pouco maiores que os obtidos por medidas internas. Ainda, a interpretação no domínio do tempo dos resultados de BE para corpos-de-prova cimentados, especialmente durante ensaios triaxiais, foi difícil de ser executada, reforçando a necessidade de se combinar diferentes métodos de interpretação quando BE forem utilizados. / Stiffness at small strains and its respective degradation are crucial information to determine more precise design parameters. Despite their importance, these properties are not usually investigated. Thus, the objective of the present work was to study the stiffness degradation of artificially cemented Osorio sand by means of different laboratory methods. The choice for a cemented material was based on environmental, economic, and technical appeals. The present study also aimed to develop and validate a Bender Elements (BE) system that can provide reliable results in the evaluation of soil degradation. BE pairs were built for bench and triaxial tests. In addition, a signal amplifier, as well as scripts were specially developed for the interpretation of data in the time domain. Increase in stiffness during the curing process was evaluated by shear wave velocity measured by BE and an ultrasonic pulse wave velocity (UPV) equipment under atmospheric pressure conditions. Stiffness degradation tests were conducted in a specially modified triaxial chamber for BE installation After seven days of atmospheric curing, specimens were sheared in the modified triaxial equipment, while stiffness changes were obtained by BE tests and internal instrumentation. The results showed that the developed BE system was capable of successfully evaluating the studied soil. The comparison between BE and UPV results was not conclusive regarding soil dependence on frequency. Shear module degradation obtained with the two methodologies presented an adequate agreement for the specimen with the smaller amount of cement. Shear moduli obtained with BE were slightly larger than those obtained with internal measurements. Also, BE results interpretation in the time domain for cemented specimens, especially in the triaxial tests, was difficult to perform, reinforcing the need to combine different interpretation methods when BE are used.

A rigidez a pequenas deformações e sua respectiva degradação são informações cruciais para se determinar parâmetros de projeto mais precisos. Apesar de sua importância, estas propriedades não são usualmente investigadas. Assim, o objetivo do presente trabalho foi de estudar a degradação da rigidez da areia de Osório artificialmente cimentada por meio de diferentes métodos de laboratório. A escolha por um material cimentado ocorreu baseada em apelos ambientais, econômicos e técnicos. O presente estudo também objetiva desenvolver e validar um sistema de Bender Elements (BE), que forneça resultados confiáveis na avaliação da degradação do solo. Pares de BE foram construídos para serem utilizados em testes de bancada e ensaios triaxiais. Além disso, um amplificador de sinal, assim como scripts foram desenvolvidos especialmente para a interpretação dos dados no domínio do tempo. O aumento da rigidez durante o processo de cura foi avaliado por meio da velocidade de onda cisalhante, medida pelos BE e por um equipamento de ondas ultrassônicas (UPV), sob condições de pressão atmosférica. Ensaios de degradação da rigidez, por sua vez, foram conduzidos em uma câmara triaxial especialmente modificada para a instalação dos BE Após sete dias de cura atmosférica, os corpos-de-prova foram cisalhados no equipamento triaxial modificado enquanto mudanças de rigidez eram obtidas por meio de testes de BE e instrumentação interna. Os resultados demonstraram que o sistema BE desenvolvido foi bem sucedido na avaliação da rigidez do solo estudado. A comparação entre os resultados do BE e UPV não foi conclusiva no que se refere à dependência do solo à frequência. A degradação do módulo obtida por ambas as metodologias apresentou uma adequada concordância para o corpo-deprova com menor quantidade de cimento. Módulos obtidos por BE foram pouco maiores que os obtidos por medidas internas. Ainda, a interpretação no domínio do tempo dos resultados de BE para corpos-de-prova cimentados, especialmente durante ensaios triaxiais, foi difícil de ser executada, reforçando a necessidade de se combinar diferentes métodos de interpretação quando BE forem utilizados. / Stiffness at small strains and its respective degradation are crucial information to determine more precise design parameters. Despite their importance, these properties are not usually investigated. Thus, the objective of the present work was to study the stiffness degradation of artificially cemented Osorio sand by means of different laboratory methods. The choice for a cemented material was based on environmental, economic, and technical appeals. The present study also aimed to develop and validate a Bender Elements (BE) system that can provide reliable results in the evaluation of soil degradation. BE pairs were built for bench and triaxial tests. In addition, a signal amplifier, as well as scripts were specially developed for the interpretation of data in the time domain. Increase in stiffness during the curing process was evaluated by shear wave velocity measured by BE and an ultrasonic pulse wave velocity (UPV) equipment under atmospheric pressure conditions. Stiffness degradation tests were conducted in a specially modified triaxial chamber for BE installation After seven days of atmospheric curing, specimens were sheared in the modified triaxial equipment, while stiffness changes were obtained by BE tests and internal instrumentation. The results showed that the developed BE system was capable of successfully evaluating the studied soil. The comparison between BE and UPV results was not conclusive regarding soil dependence on frequency. Shear module degradation obtained with the two methodologies presented an adequate agreement for the specimen with the smaller amount of cement. Shear moduli obtained with BE were slightly larger than those obtained with internal measurements. Also, BE results interpretation in the time domain for cemented specimens, especially in the triaxial tests, was difficult to perform, reinforcing the need to combine different interpretation methods when BE are used.

Shallowly embedded column base connections with unreinforced block out concrete are a common method of connecting steel columns to their foundation. There has been little research done to accurately quantify the effects of this block out concrete on the connection strength and rigidity, and therefore there is nothing to aid the practicing engineer in accounting for this in structural analysis. Due to this lack of understanding, engineers have typically ignored the effects of shallow block out concrete in their analysis, presumably leading to a conservative design. Recent research has attempted to fill this gap in understanding. Several methods have been proposed that seek to quantify the effects of shallow block out concrete on a column base connection. Barnwell proposed a model that predicts the strength of a connection. Both Jones and Tryon used numerical modeling to predict the rotational stiffness of the connection. An experimental study was carried out to investigate the validity of these proposed models. A total of 8 test specimens were created at 2/3 scale with varying column sizes, connection details, and embedment depths. The columns were loaded laterally and cyclically at increasing displacements until the connection failed. The results show that the strength model proposed by Barnwell is reasonable and appropriate, and when applied to this series of physical tests produce predictions that have an observed/predicted ratio of between 0.95 to 1.39. The results also show that methods for estimating the rotational stiffness of the connection at the top of the block out concrete, as proposed by Jones and Tryon also produce reasonable values that had observed/predicted ratios of between 0.93 to 1.47. An alternative model for determining a design value for the rotational stiffness of a shallowly embedded column base plate is also proposed. When the embedment depth to column depth ratio is greater than 1.22, the connection is sufficiently rigid and at small deflections (less than 1% story drift) may be accurately modelled with infinite rotational stiffness (a "fixed" connection) at the base of the column.

ix Flexibility has traditionally been considered an important component of human physical fitness but this conjecture lacks supporting empirical evidence. While there is extensive published research examining the relative importance of flexibility and the impact of various methods of stretching on levels of flexibility, performance and injury risk, the quality of studies has varied considerably, reliability and validity of methodology has not always been proven, and rationale has at times been questionable. Additionally, much literature has focused on static flexibility which is not necessarily related to properties of the musculotendinous unit and thus dynamic flexibility. This thesis was designed to fill gaps in the existing literature by using accepted methods to establish relative and absolute reliability of hamstring flexibility tests, consider the comparability of static and dynamic components of the global concept of flexibility and explore how dynamic flexibility and performance are influenced by fatiguing exercise and subsequent static stretching. The first aim was realised by a repeated measures study designed to establish the intraday and interday, intrarater reliability and measurement error of static and dynamic measures of hamstring flexibility. Significant relative reliability for measures of static and dynamic hamstring flexibility was demonstrated via intraclass correlation coefficient (3,1) but limits of agreement analysis indicated there was a degree of absolute measurement error that must be interpreted in relation to analytical goals. The second aim required evaluation of relationships shared by static and dynamic measures of hamstring flexibility. Significant relationships between the different static flexibility tests were established but the extent of unexplained variance indicated that only measurements from the same tests should be directly compared to each other. Relationships between different measures of dynamic flexibility and static flexibility varied from non-significant to moderately strong, suggesting that measures of static and dynamic flexibility are not identical and results should not be interchanged between the two types of tests. Due to a lack of explanatory empirical evidence, the final chapter aimed via a prospective randomised repeated measures study to investigate the impact of fatigue and post-exercise static stretching on measures of dynamic flexibility and performance. Fatigue resulted in no significant changes to passive or active dynamic flexibility measures but a significant worsening of static flexibility levels and perceived stiffness. Post-exercise stretch resulted in significantly increased passive and active energy absorption immediately and 18 hours post-exercise and in significantly reduced joint position sense immediately post-exercise. Effect sizes were small so the clinical meaningfulness of performing post-exercise static stretching is questionable, particularly if performed in place of other, potentially more beneficial practices. / Thesis (DPhil)--University of Pretoria, 2013. / gm2014 / Biokinetics, Sport and Leisure Sciences / unrestricted

Die exakte Kenntnis vom Materialverhalten und speziell von lokalen Flächenmasseschwankungen der textilen Flächen ist Voraussetzung für eine Verbesserung der Produktentwicklung und für eine hohe Qualitätsverarbeitung in der Konfektionsindustrie. Dieser Fakt ist ebenfalls für die zunehmende Anwendung im Bereich der Simulationsberechnungen von erheblicher Bedeutung. Der Wandel von 2D-CAD- zu 3D-CAD-Systemen führt in der Bekleidungsindustrie zur zwingenden Berücksichtigung der Materialeigenschaften. Aufgrund des Montageprozesses zeigen die konfektionierten textilen Flächen im Vergleich zu unkonfektionierten textilen Flächen ein anderes Erscheinungsbild. Mehrlagige Gewebe (infolge einer Naht, einer Einlage oder eines Futterstoffes) beeinflussen das Biegeverhalten und das Fallverhalten der textilen Flächen erheblich. Zur Bestimmung der Biegesteifigkeit ist seit Jahrzehnten das manuell zu bedienende Prüfgerät nach dem Cantilever-Verfahren das Bekannteste. Die eigenen Untersuchungen bestätigen, dass das Prüfgerät viele Mängel hat, welche die Genauigkeit und die Reproduzierbarkeit der Messergebnisse wesentlich beeinflussen. Im Rahmen dieser Arbeit wird ein neues Biegesteifigkeitsprüfgerät (ACPM 200) entwickelt, um eine optimale Genauigkeit und hohe Reproduzierbarkeit der Messergebnisse zu erfassen. Eine neue Methode zur Ermittlung des Einflusses der Naht auf die Biegesteifigkeit einer größeren textilen Fläche ist in der Arbeit vorhanden, um die exakte Beschreibung des realen Verhaltens von textilen Bekleidungsprodukten zu ermitteln. Die Simulation des Biegeverhaltens textiler Flächen ohne und mit vertikaler Naht wird mit Hilfe der FEM durchgeführt. Abschließend wird eine neue Prüfnorm vorgestellt, welche die Biegesteifigkeit von textilen Flächen mit lokalen Flächenmasseschwankungen mittels des neuen Biegesteifigkeitsprüfgerätes ACPM 200 beinhaltet. / Bending stiffness and Drapeability are essential material parameters for simulating textile and clothing products. Due to assembling processes garments are showing different appearances through modelling than textile fabrics. This is based on stiffening, which is caused by assembling process and local variations within material’s mass throughout the fabric. Since decades the manual bending stiffness testing device, which is based on Cantilever method, has been known. This device is insufficient because of irregular feed speed of bending sample, the visual determination of reaching and reading the bending length, the little reading precision of the measurable slide (half Millimetre) and the form of the front edge of the sample does not stay linear. Obtaining an exact evaluation of this sample edge is not possible with this device. Extensive experiments have confirmed that these deficits influence the accuracy and the reproduction of the results in a high degree. To remedy these deficits and to obtain an exact description of the material’s behaviour in order to achieve an optimal modelling of the clothing products is the new bending stiffness testing device (ACPM 200) at the ITB of TU Dresden developed. Within the investigations a new method for determining the influence of the seam on the bending stiffness of the adjacent textile fabric will be introduced. The Influence of seams on the drapability of textile fabric is investigated. A static model of Fabric with and without vertical seams is analysed with using the finite element method (FEM).

Built-up timber beams consist of individual lumber laminations connected together using mechanical fasteners such as nails, bolts and screws. Lateral torsional buckling (LTB) is an important failure mode that needs to be considered in deep beams with long spans and insufficient lateral supports. Due to the mechanical connectors, built-up beams are expected to have a lower moment capacity compared with solid beams with similar dimensions. The behaviour of built-up beams is greatly affected by the stiffness of the fasteners joining the individual laminations and determining the level of partial composite action attained in the beam. The current research aims to investigate the buckling behaviour of timber built-up beams. This is done by initially investigating the important parameters that play a role in the behaviour through an extensive sensitivity analysis. The focus of the analysis is on the contribution of the connections, since the buckling behaviour of individual solid timber beam element has been relatively well-established. Input parameters for the connection properties are obtained from joint level experimental tests. Finally, recommendations for specific fastener patterns and accompanying reduction factors on the buckling capacity relative to equivalent solid sections are developed and proposed.

Introduktion: Smartphoneapplikationen My Jump2 har bedömts att ha större tillgänglighet och inte vara beroende av labbutrustning vid vertikala hopptester. I jämförelse med kraftplatta (golden standard) har applikationen visat sig valid och reliabel. My Jump2 har uppvisat mycket bra- perfekt korrelation mot övrig kraftutrustning. Jämförelse mellan My Jump2 och kliniska tester är ännu inte beprövat på detta område. Syfte: Syftet med denna kliniska studie var att analysera samband och korrelationer mellan värden från My Jump2 och kliniska tester gällande funktionell bedömning av underbenets muskulatur. Därför jämfördes värden hos aktiva, icke skadade män och kvinnor. Metod: Totalt 26st kvinnor och män testades vid ett indivduellt testtilfälle i gymmiljö. 3rep MAX, lunge-test, antal tåhävningar och bäst av tre drop jump analyserades på dominanta benet. Pearsons korrelation användes för att undersöka samband mellan My Jump2 och kliniska tester och ANCOVA för att undersöka skillnader mellan deltagare. Resultat: Huvudfynden var att MyJump2 uppvisade två signifikanta korrelationssamband för männen och ett för kvinnorna vid jämförelse med kliniska tester. Signifikanta skillnader gällande RSI-värde med hänsyn till muskelstyrka 3rep MAX (95% CI; 0,01-0,19, p = 0,03) fanns mellan könen. Ingen signifikant skillnad i stiffness med hänsyn till ROM (95% CI; -0,11- 0,55, p = 0,18) justerat mot kön (95% CI; -0,78-2,03, p = 0,37) återfanns. Konklusion: Resultaten indikerar på att vidare forskning är nödvändig. Endast få signifikanta korrelationssamband återfanns mellan värden från My Jump2 och kliniska tester. My Jump2 visar signifikanta nivåer för RSI-värdet med hänsyn till muskelstyrka och kön. Studien kan inte bekräfta förväntade samband mellan My Jump2 och kliniska tester för underbenet. / Introduction: The smartphoneapplication My Jump2 has been assessed in rescent research for its validity and reliability. In comparison to golden standard devices, My Jump2 shows great- perfect correlation measuring jump height. Eventhough former results indicate usability of the smarthphoneapplication, further research is needed in order to evaluate clinical usefulness in a more expanded population. Aim: The aim of this study was to analyse the relationship and correlations between measured values from My Jump2 and clinical testing of lower extremity performance. This in an active and recreational population, both male and female. Method: A total of 26 males and females were tested individually in a gym-location. 3rep MAX, lunge-test, heel-rises to exhaustion and best of three drop jumps were analysed on the dominat leg. Pearsons correlation was used to evaluate the relationship between My Jump2 and clinical tests and ANCOVA to analyse diffrences within the testgroup. Results: Analysis showed two significant correlations between functional values for the men and one for women when comparing My Jump2 and clinical tests. A significant difference in RSI-value was found between the covariate (sex) (95% CI; 0,01-0,19, p = 0,03) considering 3rep MAX (factor). No significant difference was found in stiffness between the covariate (sex) considering ROM (factor). Conclusion: This study indicates that further research is needed. Analysis shows few significant correlations between My Jump2 and clinical tests. My Jump2 results shows significant values regarding RSI-values considering sex and musclestrenght. This study can not confirm the relationship and correlations between measured values from My Jump2 and clinical testing of lower extremity performance.

Recent research has shown that a significant number of the falls from elevation occur when laborers are working on unfinished structures. Workers walking on wood I-joists on roofs and floors are prone to fall hazards. Wood I-joists have been replacing dimension lumber for many floor systems and a substantial number of roof systems in light-frame construction. Wood I-joists are designed to resist axial stresses on the flanges and shear stresses on the web while minimizing material used. However, wood I-joists have poor resistance to applied lateral and torsional loads and are susceptible to lateral-torsional buckling instability. Workers walking on unbraced or partially braced wood I-joists can induce axial and lateral forces as well as twist. Experimental testing demonstrated that workers cause lateral-torsional buckling instability in wood I-joists. However, no research was found related to the lateral-torsional buckling instability induced by individuals walking on the wood I-joists. Furthermore, no research was found considering the effects of the supported end conditions and partial bracing in the lateral-torsional buckling instability of wood I-joists. The goal of this research was to derive mathematical models to predict the dynamic lateral-torsional buckling instability of wood composite I-joists loaded by individuals walking considering different supported end conditions and bracing system configurations. The dynamic lateral-torsional buckling instability was analyzed by linearly combining the static lateral-torsional buckling instability with the lateral bending motion of the wood I-joists. Mathematical models were derived to calculate the static critical loads for the simply supported end condition and four wood I-joist hanger supported end conditions. Additionally, mathematical models were derived to calculate the dynamic maximum lateral displacements and positions of the individual walking on the wood I-joists for the same five different supported end conditions. Three different lean-on bracing systems were investigated, non-bracing, one-bracing, and two-bracing systems. Mathematical models were derived to calculate the amount of constraint due to the lean-on bracing system. The derived mathematical models were validated by comparison to data from testing for all supported end conditions and bracing systems The predicted critical loads using the static buckling theoretical models for the non-bracing system and the static buckling theoretical models combined with the bracing theoretical models for the simply and hanger supported end conditions agreed well with the critical loads obtained from testing for the two wood I-joist sizes investigated. The predicted maximum lateral displacements and individual positions using the bending motion theoretical models for the simply and hanger supported end conditions agreed well with the corresponding maximum lateral displacements and individual positions obtained from testing for both wood I-joist sizes. Results showed that; a) the supported end condition influenced the critical loads, maximum lateral displacements and individual positions, b) the bracing system increased the critical loads and reduced the maximum lateral displacements, c) the critical load increased as the load position displaced away from the wood I-joist mid-span, d) the critical load reduced as the initial lateral displacement of the wood I-joist increased and e) the wood I-joist mid-span was the critical point in the dynamic lateral-torsional buckling instability. / Ph. D.