Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The South African National Standard for the structural use of cold-formed steel (SANS 10162-2) provides capacity prediction models for screwed connections. Screwed connections are designed against shear failure of the screw(s), section tear-out, net section failure and tilt-andbearing failure. Previous studies (Rogers & Hancock, 1997) showed that the capacity is typically determined by the tilt-and-bearing type failure mode. The aim of this document is to report on the reliability of single screwed connections in cold-formed steel against this critical failure mode. Predicted nominal capacities depend on the ultimate tensile strength of the steel, the thickness of the connected plates and the diameter of the screw. Design capacities are obtained by multiplying the nominal capacities by a capacity reduction factor of 0.5, according to SANS 10162-2. Reliability is assessed by means of FORM analyses, taking uncertainty in the prediction model and variability of input parameters into account. Laboratory testing of 222 single screwed connections allowed to statistically describe the model factor, i.e. the ratio of actual tested- over unbiased predicted capacity. For each connection, the steel strength, plate thickness and screw diameter were measured, with the measured values used to predict capacity. This implies that the model factor accounts for uncertainty in the prediction model and experimental setup, while the variability of input parameters is separately accounted for through appropriate statistical modelling. Variability in the input parameters was described using appropriate statistical distributions from expert literature (Holicky, 2009:199; JCSS, 2000). For steel strength, the mean value and standard deviation were obtained from tensile tests, while mean values and standard deviations of the plate thickness and screw diameter were obtained from the above mentioned measurements. The experimental work and numerical analysis resulted in a model factor with a mean just exceeding unity and a small standard deviation. This suggests that the design code under consideration is able to accurately predict the nominal capacity of screwed connections. The FORM analysis resulted in computed reliability indexes significantly higher than the corresponding target values which suggest conservative and reliable design formulations. Die eksperimentele werk en numeriese analise het gelei tot 'n model faktor met 'n gemiddeld hoër as een en 'n klein standaardafwyking. Dit dui daarop aan dat die ontwerp-kode onder oorweging in staat is om die nominale kapasitiet van skroef verbindings akkuraat te voorspel. Die betroubaarheid analise het gelei tot betroubaarheidsindekse aansienlik hoër as die ooreenstemmende teiken waardes wat daarop dui dat die ontwerp formulerings betroubaar en hoogs konserwatief is. / AFRIKAANSE OPSOMMING: Die Suid-Afrikaanse Nasionale Standaard vir die strukturele gebruik van koud gevormde staal (SANS 10162-2) bied voorspellingsmodelle vir die kapasitiet van skroef verbindings. Skroef verbindings word ontwerp teen skroef faling, staal profiel faling, die uitskeer van skroewe en ook faling weens skroef kanteling. Vorige studies (Rogers & Hancock, 1997) het getoon dat die kapasiteit gewoonlik bepaal word deur die skroef-kantel falingsmodus. Die doel van hierdie navorsing is om verslag te doen oor die betroubaarheid van tipiese enkel skroef verbindings in koud gevormde staal strukture teen hierdie kritiese falingsmodus. Voorspelde nominale kapasiteite hang af van die treksterkte van die staal, die dikte van die verbonde profiele en die diameter van die skroef. Volgens die SANS 10162-2 word die ontwerp kapasiteit verkry deur die nominale kapasiteit met 'n kapasiteitsverminderingsfaktor van 0.5 te vermenigvuldig. Betroubaarheid word ontleed deur middel van ʼn eerste orde betroubaarheidsmetode analise, met die in ag neming van onsekerheid in die voorspellingsmodel en wisselvalligheid van die parameters. Laboratoriumtoetse van 222 enkel skroef verbindings het ʼn statistiese beskrywing van die model faktor toegelaat. Die model faktor is bereken as die verhouding tussen die getoetste kapasitiet en die voorspelde kapasitiet. Die staal sterkte, profiel dikte en skroef diameter is gemeet vir elke verbinding met die gemete waardes wat gebruik is om die kapasiteit te voorspel. Dit beteken dat die model faktor slegs onsekerhede in die voorspellingsmodel en van die eksperimentele opstelling in ag neem, terwyl die wisselvalligheid van die parameters afsonderlik in ag geneem word deur toepaslike statistiese modellering. Variasie in die parameters is beskryf met gepaste statistiese verdelings voorgestel deur verskeie literatuur (Holicky, 2009:199; JCSS, 2000). Aangaande die staal sterkte, is die gemiddelde waardes en standaardafwykings verkry deur standaard trek toetse terwyl die gemiddelde waardes en standaardafwykings van die plaat dikte en skroef diameter verkry is deur die bogenoemde metings.

In this thesis the experimental results of seven full-scale glass fiber-reinforced polymer (GFRP) reinforced concrete (RC) slab-column edge connections are presented. The dimensions of the slabs were 2,800×1,550×200 mm with a square column measuring 300×300×2,200 mm. The test connections were divided into two series. Series I included three connections investigating the effect of flexural reinforcement ratio (0.90, 1.35 and 1.80%) when high strength concrete (HSC) is used, while Series II included four connections investigating the effect of GFRP shear reinforcement type and pattern on normal strength concrete (NSC) connections. Test results showed that increasing the reinforcement ratio increased the punching capacity and the post-cracking stiffness of the HSC connections. Furthermore, the use of headed studs and corrugated bars increased the punching capacity and the deformability of the NSC connections. Test results were compared to the predictions of the Canadian and American design provisions for FRP-RC structures. / February 2017

Este trabalho trata da influência da rigidez das ligações na deslocabilidade lateral e na distribuição de esforços de pórticos planos de aço sob condições de serviço. Estuda-se em particular a influência das ligações com chapa de topo, e propõe-se um modelo para descrição do comportamento momento-rotação dessas ligações. Este trabalho também apresenta um revisão dos diversos modelos existentes para previsão do comportamento momento-rotação de ligações viga-coluna, e discute as diversas formas de influência dessas ligações no comportamento global da estrutura e de seus elementos individuais. / The aim of this work is the influence of connections flexibility in the plane framed structures in serviceability conditions. Special attention is paid for the influence of extended end plate connections, for which proposes a model for prevision of moment-rotation relationship. This work also presents a revision of the various models for prevision of moment-rotation relationship of beam-to-column connections, and discusses the several forms of the influence of that connections in overall performance of the structures and your individual members.

Recentemente observou-se experimentalmente, Johnson et al. (2010), que fatias organotípicas corticais de rato são capazes de completar padrões espaço-temporais, após serem treinadas. Embora se especule que mecanismos de plasticidade sináptica e homeostática estejam por trás do fenômeno, ainda não existe nenhuma explicação detalhada sobre o assunto. Com o intuito de propor uma explicação clara e consistente para os mecanismos que permeiam a resposta da rede aos estímulos como um todo, nos propomos a estudar este fenômeno por meio de uma rede de neurônios de integração-e-disparo dotada de mecanismos de homeostase intrínseca e de plasticidade sináptica dependente de disparos. O sistema construído foi explorado, de modo a determinar em que condições a rede poderia comportar-se como o sistema real, e treinado de forma similar `a realizada experimentalmente por Johnson et al. (2010). / Recently it has been observed experimentally, Johnson et al. (2010), that organotypic cortical slices of rat are capable of completing spatio-temporal patterns after training. Although it is speculated that synaptic and homeostatic plasticity may have an important role in this phenomenon, there is still no detailed explanation about this subject. In order to propose a clear and consistent explanation for the mechanisms that underlie the network response to stimuli as a whole, we propose to study this phenomenon through a network of integrate-and-fire neurons endowed with intrinsic homeostasis and spike-timing dependent plasticity mechanisms. The constructed system was explored, aiming to determine in which conditions the network could behave as the real system, and trained in a way similar as the experimental one done by Johnson et al. (2010).

Finite element models were created in Abaqus 6.14 to characterize the rotational stiffness of shallowly embedded column-foundation connections. Scripts were programmed to automate the model generation process and allow study of multiple independent variables, including embedment length, column size, baseplate geometry, concrete modulus, column orientation, cantilever height, and applied axial load. Three different connection types were investigated: a tied or one part model; a contact-based model; and a cohesive-zone based model. Cohesive-zone modeling was found to give the most accurate results. Agreement with previous experimental data was obtained to within 27%. Baseplate geometry was found to affect connection stiffness significantly, especially at lower embedment depths. The connection rotational stiffness was found to vary only slightly with cantilever height for typical column heights. Results from varying other parameters are also discussed.

The interstate highway system is vitally dependent upon current and future bridges. These bridges must be designed economically to continue the serviceability with limited maintenance. For precast bridge construction a portion of the design must consider the bridge connections. Some current connections have proved insufficient in serviceability as there is uncontrolled cracking. In other connections there are uncertainties in the calculations (or lack of calculations) which require design guidelines. This thesis presents design recommendations for precast decking u-bar reinforcement in tension which results from negative moment over a pier. Testing results from the University of Tennessee were analyzed to determine the design recommendations. The calculated capacity of the specimens was determined first by strut and tie modeling by AASHTO and ACI, but was shown to be insufficient. Proposed changes to the current calculation of the strut width as specified in AASHTO and ACI STM methods were discussed in order to match the test results. However, strut and tie modeling demonstrated that the design for the lacer bar was inadequate. Since the strut and tie modeling method resulted in an inaccurate lacer bar size, another method was developed. A triangular shape develops from the flow of forces in the connection joint zone; as a result, a free body diagram (FBD) was developed from the concrete triangular shape. This diagram showed how the forces flow in the in-situ joint as well as how they are resisted. A formula was developed from the FBD to determine the capacity of the joint which accurately reflected the capacities from tests. A FBD was also made of the lacer bar utilizing the forces and geometry calculated from the capacity calculations. A computer analysis program was used to determine the forces in the lacer bar. The lacer bar could then be designed since the required forces to resist (moment and shear) were known. A comparison of the strut and tie model to the triangular method led to the conclusion that both can determine the longitudinal reinforcement spacing, joint overlap length, and concrete strength, but only the triangular method can determine a more sufficient lacer bar size.

Darbo objektas – naujų tarporganizacinių ryšių formavimasis Lazdijų rajono turizmo sektoriuje. Darbo tikslas – atskleisti (ištirti) naujų tarporganizacinių ryšių formavimosi procesus Lazdijų rajono turizmo sektoriuje. Darbo uždaviniai: 1. Išanalizuoti tarporganizacinių ryšių sampratą; 2. Išanalizuoti tarporganizacinių ryšių formas bei modelius; 3. Atlikti Lazdijų rajono turizmo sektoriaus SSGG analizę tarporganizacinių ryšių formavimosi kontekste. 4. Atlikti tarporganizacinių ryšių formavimosi Lazdijų rajono turizmo sektoriuje ekspertinį vertinimą. Darbo metodai: mokslinės literatūros analizė, ekspertinis vertinimas, SSGG analizė. Pagrindinės darbo išvados: Siekiant išsiaiškinti tarporganizacinių ryšių formavimosi aspektus, buvo atliktas Lazdijų rajono turizmo sektoriaus ekspertinis vertinimas. Lazdijų rajono turizmo sektoriaus ekspertų vertinimo metu nustatyta, kad didžiausią įtaką apsisprendimui kurti, įsitraukti į tarporganizacinių ryšių formavimosi procesą turi vidiniai organizacijos veiksniai, t.y. organizacijų filosofija ir vertybės bei vadovo pozicija ir siekiai. Reikia pažymėti, kad Lazdijų rajono turizmo sektoriaus atstovams labiausiai priimtinos partnerystės, klasterio bei tinklo bendradarbiavimo formos, mažiausiai – sąveikavimas konkuruojant bei integracinis bendradarbiavimas. Tikėtina, kad ekspertams apie žemesniais balais įvertintas tarporganizacinių ryšių formas ir jų veikimo principus trūksta informacijos. Ekspertų vertinimo duomenimis nustatyta, kad... [toliau žr. visą tekstą] / The object - the formation of new interorganizational connections in the tourism sector of Lazdijai district. The aim - to explore processes of the formation of new interorganizational connections in the tourism sector of Lazdijai district. Objectives: 1. To analyze the concept of interorganizational connections; 2. To analyze forms and types of the interorganizational connections; 3. To perform SWOT analysis of Lazdijai district’s tourism sector in the context of the formation of the interorganizational connections. 4. To accomplish expert evaluation of the formation of Lazdijai district’s tourism sector‘s interorganizational connections. Methods: analysis of scientific literature, expert evaluation, SWOT analysis. The main conclusions: In order to elucidate aspects of the formation of interorganizational connection was performed expert evaluation of Lazdijai district’s tourism sector. During Lazdijai district’s tourism sector’s expert evaluation was found that the greatest influence on the decision to develop, to become involved in the process of the formation of interorganizational connection have organization’s internal factors, i.e. organizational philosophy and values, and leader’s position and aspirations. It should be noted that the most acceptable to representatives of Lazdijai district‘s tourism sector is partnership, cluster and network forms of cooperation, at least acceptable –interaction competition and integrational cooperation. It is likely that the experts... [to full text]

Recentemente observou-se experimentalmente, Johnson et al. (2010), que fatias organotípicas corticais de rato são capazes de completar padrões espaço-temporais, após serem treinadas. Embora se especule que mecanismos de plasticidade sináptica e homeostática estejam por trás do fenômeno, ainda não existe nenhuma explicação detalhada sobre o assunto. Com o intuito de propor uma explicação clara e consistente para os mecanismos que permeiam a resposta da rede aos estímulos como um todo, nos propomos a estudar este fenômeno por meio de uma rede de neurônios de integração-e-disparo dotada de mecanismos de homeostase intrínseca e de plasticidade sináptica dependente de disparos. O sistema construído foi explorado, de modo a determinar em que condições a rede poderia comportar-se como o sistema real, e treinado de forma similar `a realizada experimentalmente por Johnson et al. (2010). / Recently it has been observed experimentally, Johnson et al. (2010), that organotypic cortical slices of rat are capable of completing spatio-temporal patterns after training. Although it is speculated that synaptic and homeostatic plasticity may have an important role in this phenomenon, there is still no detailed explanation about this subject. In order to propose a clear and consistent explanation for the mechanisms that underlie the network response to stimuli as a whole, we propose to study this phenomenon through a network of integrate-and-fire neurons endowed with intrinsic homeostasis and spike-timing dependent plasticity mechanisms. The constructed system was explored, aiming to determine in which conditions the network could behave as the real system, and trained in a way similar as the experimental one done by Johnson et al. (2010).

Recentemente observou-se experimentalmente, Johnson et al. (2010), que fatias organotípicas corticais de rato são capazes de completar padrões espaço-temporais, após serem treinadas. Embora se especule que mecanismos de plasticidade sináptica e homeostática estejam por trás do fenômeno, ainda não existe nenhuma explicação detalhada sobre o assunto. Com o intuito de propor uma explicação clara e consistente para os mecanismos que permeiam a resposta da rede aos estímulos como um todo, nos propomos a estudar este fenômeno por meio de uma rede de neurônios de integração-e-disparo dotada de mecanismos de homeostase intrínseca e de plasticidade sináptica dependente de disparos. O sistema construído foi explorado, de modo a determinar em que condições a rede poderia comportar-se como o sistema real, e treinado de forma similar `a realizada experimentalmente por Johnson et al. (2010). / Recently it has been observed experimentally, Johnson et al. (2010), that organotypic cortical slices of rat are capable of completing spatio-temporal patterns after training. Although it is speculated that synaptic and homeostatic plasticity may have an important role in this phenomenon, there is still no detailed explanation about this subject. In order to propose a clear and consistent explanation for the mechanisms that underlie the network response to stimuli as a whole, we propose to study this phenomenon through a network of integrate-and-fire neurons endowed with intrinsic homeostasis and spike-timing dependent plasticity mechanisms. The constructed system was explored, aiming to determine in which conditions the network could behave as the real system, and trained in a way similar as the experimental one done by Johnson et al. (2010).

Este trabalho trata da influência da rigidez das ligações na deslocabilidade lateral e na distribuição de esforços de pórticos planos de aço sob condições de serviço. Estuda-se em particular a influência das ligações com chapa de topo, e propõe-se um modelo para descrição do comportamento momento-rotação dessas ligações. Este trabalho também apresenta um revisão dos diversos modelos existentes para previsão do comportamento momento-rotação de ligações viga-coluna, e discute as diversas formas de influência dessas ligações no comportamento global da estrutura e de seus elementos individuais. / The aim of this work is the influence of connections flexibility in the plane framed structures in serviceability conditions. Special attention is paid for the influence of extended end plate connections, for which proposes a model for prevision of moment-rotation relationship. This work also presents a revision of the various models for prevision of moment-rotation relationship of beam-to-column connections, and discusses the several forms of the influence of that connections in overall performance of the structures and your individual members.