With the increasing need for large columnless structures in today's society, glued-laminated Triax domes are being designed and built. Even though many have already been constructed, no methods have been established to accurately determine the ultimate load capacity or the factor of safety. Several ABAQUS finite element analyses have been conducted at Virginia Polytechnic Institute and State University to determine these values (Davalos, 1989). The work in this area has been slowed due to the absence of a preprocessor for the creation of the input data file. The use of a preprocessor could greatly accelerate the analysis process and prove to be more efficient. The primary objective of this thesis is to present a clear detailed procedure for the creation of the input data file using the Integrated Design Engineering Analysis Software package (I-DEAS) version 4.1. In addition to meeting this objective, several other topics concerning I-DEAS modeling guidelines and post processing features are discussed. The results oT a linear finite element analysis is also presented. The use of a preprocessor is essential for the creation of the triax input data fiIe. I-DEAS can not only meet this challenge, but can provide assistance in all facets of finite element modeling. / Master of Science

A finite element modeling and geometrically nonlinear static analysis of glued-laminated timber domes is presented. The modeling and analysis guidelines include: the generation of the geometry, the selection of finite elements to model the components of a dome (beams, purlins, connections, and tension ring), the specification of boundary conditions, the specification of material properties, the determination of a sufficiently accurate mesh, the determination of design loads and the specification of load combinations, the application of analysis procedures to trace the complete response of the structure, and the evaluation of the response. The modeling assumptions and analysis procedures are applied to a dome model whose geometry is based on an existing glulam timber dome of 133 ft span and 18 ft rise above the tension ring. This dome consists of triangulated networks of curved southern pine glulam members connected by steel hubs. The members lie on great circles of a spherical surface of 133.3 ft radius. The dome is covered with a tongue-and-groove wood decking, which is not considered in this study. Therefore, the surface pressures are converted into member loads and then discretized into nodal concentrated loads. A geometrically nonlinear, 3-d, 3-node, isoparametric beam element for glulam beams is formulated, and a program is developed for the analysis of rigid-jointed space frames that can trace the response of the structure by the modified Newton-Ralphson and the modified Risk-Wempner methods. The material is assumed to be continuous, homogeneous, and transversely isotropic. The material properties are assumed to be constant through the volume of the element. The transverse isotropy assumption is validated for southern pine by testing small samples in torsion. The accuracy of the modeling assumptions for southern pine glulam beams is experimentally verified by testing full-size, curved and straight, glulam beams under combined loads. The results show that the isobeam element can accurately represent the overall linear response of the beams. However, to analyze glulam domes with the program, connector elements to model the joints and a truss element to model the tension ring must be added. Therefore, the finite element program ABAQUS is used for the analysis of the dome model. Three dead-load/snow-load combinations are considered in the analysis of the dome model. The space frame joints and the purlin-to-beam connections are modeled with 2-node isobeam elements. A 3-d, 2-node, truss element is used to model the tension ring. Three distinct analyses are considered for rigid and flexible joints: a linear analysis to check the design adequacy of the members. A linearized eigenvalue buckling prediction analysis to estimate the buckling load, which provided accurate estimates of the critical loads when rigid joints were specified. Finally, an incremental, iterative, geometrically nonlinear analysis to trace the complete response of the structure up to failure. It is shown that elastic instability, which is governed by geometric nonlinearities, is the dominant failure mode of the test dome. At the critical load, the induced element stresses remained below the proportional limit of the material. A discussion of the results is presented, and recommendations for future extensions are included. / Ph. D.

Thesis (M.S.)--Ohio University, November, 2004. / Includes bibliographical references (p. 67-72)

Thesis (M.S.)--Ohio University, November, 2004. / Title from PDF t.p. Includes bibliographical references (p. 67-72)

The object of this study is to investigate the stability of the Church of the Nazarene Varax dome under various load distributions. A model of the dome constructed using I-DEAS is presented and results of linear and nonlinear analyses are discussed. A comparison between the critical load obtained using nonlinear analysis and combined linear and nonlinear analysis is made. The model is modified to include flexible joints and bracing to model the decking. The effect of these modifications on the critical load is discussed. / Master of Science

Subduction zone volcanoes are a major natural hazard, frequently endangering lives and livelihoods. The eruptive history of many subduction zone volcanoes includes the extrusion of blocky, silicic lava that forms domes or flows, but we do not yet understand what determines the duration of dome-forming behaviour, what path magma may take to the surface, or how these systems may change over time. This thesis presents an investigation of the Santiaguito complex of lava domes and flows in Guatemala, which has been erupting continuously since its inception in 1922. The Santiaguito lavas are predominantly dacitic to andesitic, with a gradual reduction in SiO2 content from ~66 wt% in the 1920s, to ~62 wt% in 2002. This is consistent with a ~15% decrease in the extent of fractional crystallization over that time. The compositions of plagioclase phenocryst cores indicate a diminished role for magma mixing after the 1940s. I model the Santiaguito system as progressively extracting magma from an extensive, chemically-stratified storage zone. Petrological data are consistent with a storage zone extending from ~25 to ~12 km depth, and magma storage temperatures of ~940 to ~980°C. Phenocryst-hosted apatites suggest melt in this storage zone contained 401 to 1199 ppm S, 600 to 1300 ppm F, and 4100 to 6200 ppm Cl. Ascending magma may pass slowly through a conduit bottleneck, or plug, at shallow depths; groundmass texture suggests that melt rigidifies at or near the base this plug. Pre-eruptive melt volatile concentrations suggest time-averaged fluxes of 40 to 263 Mg d-1 SO2, 32 to 145 Mg d-1 HF, and 247 to 708 Mg d-1 HCl, giving ratios of 0.6 to 0.8 HF/SO2, and 2.7 to 6.2 HCl/SO2. These results are consistent with the few direct measurements of SO2 at Santiaguito, and with measured halogen emissions from other silicic dome-forming systems.

Thesis (MSc)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: The northeast-trending south Central Zone (sCZ) of the Pan-African Damara belt in central Namibia is structurally characterized by kilometer-scale, northeast-trending dome structures developed in Neoproterozoic rocks of the Damara Sequence. A number of different structural models have been proposed for the formation of these domes in the literature. This study describes the structural geology of the Usakos dome. The study discusses the structural evolution of the dome within the regional framework of the cSZ that represents the high-grade metamorphic axis of the Damara Belt, characterized by voluminous Pan-African granitoids. The northeastern part of the Usakos dome is developed as an upright- to northwestverging anticlinorium containing a steep southeasterly-dipping axial planar foliation. The northeast fold trend persists into the southwestern parts of the Usakos dome. However, this southwestern core of the dome is inundated by synkinematic granitic sheets. Distinct marker horizons of the Damara Sequence outcrop as screens within the granite, preserving a ghost stratigraphy. These screens illustrate the position and orientation of second-order folds. Significantly, most of the stratigraphy of the Damara Sequence is overturned in these folds. For example, some second-order anticlines developed in the northeastern parts of the Usakos dome can be followed along their axial traces into the southwestern hinge of the dome, where they appear as synformal anticlines, i.e. synformal structures cored by older strata, plunging towards the northeast. The inverted stratigraphy and northeasterly fold plunges suggest the northeast-trending folds are refolded by second-generation, northwest-trending folds, thus, forming kilometer-scale Type-2 interference folds. The resulting fold geometries are strongly non-cylindrical, approaching southwest-closing sheath folds indicating a top-to-the-southwest material transport. Lower-order folds in this overturned domain show radial fold plunges, plunging away from the centre of the dome core, as well as a shallowly-dipping schistosity. The close spatial and temporal relationship between granite intrusion and the formation of the southwest-vergent, sheath-type folds, radial distribution of fold plunges and the subhorizontal foliation confined to the southwestern hinge of the Usakos dome are interpreted to signify the rheological weakening and ensuing collapse of the developing first-order Usakos dome immediately above the synkinematic granite intrusions. Orogenparallel, southwest-vergent sheath folds and top-to-the southwest extrusion of the southwestern parts of the Usakos dome and northwest-vergent folding and thrusting characterizing the northeastern extent of the Usakos dome are both responses to the northwest-southeast- directed contractional tectonics recorded during the main collisional phase in the Damara belt. On a regional scale, the Usakos dome represents the link between the foreland-vergent northeastern part of the sCZ and the southwest-vergent, high-grade southwestern parts of the sCZ. The results of this study illustrate how dramatic variations in structural styles may be caused by the localized and transient rheological weakening of the crust during plutonic activity. / AFRIKAANSE OPSOMMING: Die noordoos-strekkende, suidelike Sentrale Sone (sSS) van die Pan-Afrikaanse Damara gordel in sentraal Namibië word karakteriseer deur kilometer-skaal, noordoosstrekkende koepel strukture, ontwikkel in die Neoproterozoïkum gesteentes van die Damara Opeenvolging. 'n Aantal verskillende struktuur modelle is voorgestel in die literatuur vir die vorming van hierdie koepels. Hierdie ondersoek beskryf die struktuur geologie van die Usakos koepel. Die ondersoek bespreek die strukturele ontwikkeling van die koepel in die regionale konteks van die sSS, wat die hoë graadse metamorfe magmatiese as van die Damara Gordel verteenwoordig, en karakteriseer word deur omvangryke Pan-Afrikaanse granitoïede. Die noordoostelike gedeelte van die Usakos koepel is ontwikkel as 'n antiklinorium met 'n vertikale- tot noordwestelike kantelrigting. wat 'n steil hellende, suidoostelike asvlak planêre foliasie bevat. Die noordoos-strekkende plooiing kom voor tot in die suidwestelike kern van die Usakos wat ingedring is deur sinkinematiese granitiese plate. Die posisie en oriëntasie van tweede-orde plooie is afgebeeld in die graniete deur 'n skimstratigrafie wat preserveer is deur duidelike merker horisonne van die Damara Opeenvolging. Die stratigrafie van die Damara Opeenvolging is opmerklik meestal omgekeer in hierdie plooie. Byvoorbeeld, tweede-orde antikliene ontwikkel in die noordoostelike gedeelte van die Usakos koepel kan gevolg word langs hul asvlakspore tot in die suidwestelike skarnier van die koepel, waar dit voorkom as sinforme antikliene, d.w.s. sinforme strukture met ouer strata in die kern wat na die noordooste duik. Die omgekeerde stratigrafie en noordoostelike plooi duiking impliseer dat die noordoosstrekkende plooie weer geplooi is deur tweede-generasie, noordwes-strekkende plooie, wat dus aanleiding gegee het tot die vorming van kilometer-skaal, tipe-2 interferensie plooie. Die gevolglike plooi geometrieë is uitdruklik nie-silindries, en toon 'n oorgang na skede plooie met 'n sluiting na die suidweste, wat dui op 'n bokant-na-die-suidweste materiaal vervoer. Laer-orde plooie in die omgekeerde domein vertoon radiale duiking van die plooie, weg van die middelpunt van die koepel kern, sowel as 'n vlak hellende skistositeit. Die noue ruimtelike en temporele verwantskap tussen graniet intrusie en die vorming van skede-tipe plooie met 'n kantelrigting na die suidweste, die radiale verspreiding van plooi duiking, en die subhorisontale foliasie wat beperk is tot die suidwestelike skarnier van die Usakos koepel, word interpreteer as 'n aanduiding van die reologiese verswakking en die gevolglike ineenstorting van die ontwikkelende eerste-orde Usakos koepel, onmiddellik aan die bokant van die sinkinematiese graniet intrusies. Die orogeenparalleie skede plooie met kantelrigting na die suidweste en bokant-na-die-suidweste ekstrusie van die suidwestelike gedeelte van die Usakos koepel, en plooiing met kantelrigting na die noordweste en stootverskuiwing wat kenmerkend is van die noordoostelike gedeelte van die Usakos koepel, is beide 'n reaksie op die noordwessuidoos- gerigte vernouings tektoniek opgeteken gedurende die hoof botsings fase in die Damara gordel. Op 'n regionale skaal verteenwoordig die Usakos koepel die verbinding tussen die noordoostelike gedeelte van die sSS met 'n voorland kantelrigting. en die hoë graad suidwestelike gedeelte van die sSS met 'n kantelrigting na die suidweste. Die resultate van hierdie ondersoek toon aan hoe dramatiese variasies in struktuur style veroorsaak kan word deur die gelokaliseerde en kortstondige reologiese verswakking van die kors gedurende plutoniese aktiwiteit.

A roof over a manure reservoir eliminates the entry of precipitations, reduces odour and volatile gas emissions, lowers the storage and handling costs and alleviates environmental impacts. / Structural analysis and testing were carried out to establish the feasibility of geodesic domes as manure reservoir roofting. A stress analysis, conducted by computer was used to determine maximum compression loads on roof members. Compression tests were carried out in the laboratory to test two laminated designs and to evaluate the performance of a member joint. / Structural analysis showed that the Lamella type dome, with a diameter/height ratio of 4, offers the best geometry considering design criteria for manure roofs. Compression tests confirmed that laminated members, made of 38 x 89 mm and 38 x 140 mm pieces, can resist the design stress developed in a 22 meter diameter dome. / Loading tests revealed that non laminated wood members failed at 80% of the design load. However, the joints (formed by two 3,1 mm thick steel plates bolted to the members) were still able to resist an increase in loading. / Data obtained from the tests were used for a preliminary design of a geodesic roof taking into account specific conditions such as humidity and manure gas. However further study is required to adapt this concept to real conditions over a manure reservoir. / The cost of a 22 meter diameter dome, for covering manure reservoirs, is estimated at 79$/m$ sp2$ which is more expensive than the cost of the currently used, least expensive manure pit roof (wood truss design).

No description available.

No description available.