Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Alan Darrell Ho. / M.S.

The usefulness of Coulomb (friction) damping in earthquake-resistant design of structures is examined by studying the seismic response characteristics of structures with various arrangements of sliding interfaces. First, three basic arrangements are studied for their effectiveness in reducing lateral displacements of the supporting frame, accelerations of the floor slab and the resulting secondary floor spectra. These are: (1) slab sliding system which has the sliding interface between the floor slab and the supporting frame, (2) double sliding system which consists of sliding interfaces at both top and bottom interfaces (a combination of slab sliding and base sliding), and (3) spring-assisted slab sliding system which is a slab sliding system aided by lateral springs attached to the columns to resist excessive sliding displacement of the slab. The responses are obtained for structures with different frequencies and are presented in response spectrum form. The isolation characteristics of one slab sliding system are compared with those of the base sliding and hysteretic systems. Non-dimensional design parameters defined in terms of the corresponding elastic design spectra are introduced for design purposes and for a consistent presentation of the results. Methods for predicting the important response quantities using the non-dimensional parameters are discussed and their applicability is evaluated. Next, the response of a simple slab sliding arrangement to simultaneous horizontal and vertical ground motion input is studied to see the effects of the vertical excitation on the isolation efficiency of that arrangement. Finally the suitability of adopting such sliding arrangements in multi-story structures is also examined. The seismic responses of multi-story structures with floor slabs sliding at different story levels are obtained and compared with the response of non-sliding structure and base sliding to examine the effectiveness of such sliding arrangement. / Ph. D.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Water-retaining structures are commonly used in South Africa for the storage of potable water and waste water. However, a South African code pertaining to the design of concrete water-retaining structures do not currently exist and therefore use is made of the British Standard BS 8007 (1987). For the design of concrete water-retaining structures in South Africa, only the hydrostatic loads are considered while forces due to seismic activity are often neglected even though seismic excitations of moderate magnitude occur within some regions of the country. Hence, the primary aim of this study was to determine whether seismic activity, as it occurs in South Africa, has a significant influence on water-retaining structures and whether it should be considered as a critical load case. In order to assess the influence of seismic activity on the design of water-retaining structures the internal forces in the wall and the required area of reinforcement were compared. Comparisons were made between the seismic analyses and static analyses for both the ultimate and serviceability limit states. In order to obtain the internal forces in the wall use was made of an appropriate Finite element model. Three Finite element models were investigated in this study and the accuracy of each model was assessed based on the fundamental frequency, base shear force and overturning moment. These values were compared to the values obtained with the numerical method presented by Veletsos (1997) which was verified with Eurocode 8: Part 4 (2006). The results obtained indicated that seismic excitations of moderate magnitude do have a significant influence on the reinforcement required in concrete water-retaining structures. For both the ultimate limit state and serviceability limit state the required reinforcement increased significantly when seismic loads were considered in the design. As in the case for static design of water-retaining structures, the serviceability limit state also dominated the design of these structures under seismic loading. / AFRIKAANSE OPSOMMING: Beton waterhoudende strukture in Suid-Afrika word op ‘n gereelde basis gebruik vir die stoor van drink- sowel as afvalwater. ‘n Suid-Afrikaanse kode vir die ontwerp van hierdie strukture bestaan egter nie en dus word die Britse kode BS 8007 (1987) hiervoor gebruik. Vir ontwerp doeleindes word soms slegs die hidrostatiese kragte beskou terwyl kragte as gevolg van seismiese aktiwiteite nie noodwendig in berekening gebring word nie. Seismiese aktiwiteite van gematigde grootte kom egter wel voor in sekere dele van Suid-Afrika. Die hoofdoel van hierdie studie was dus om die invloed van seismiese aktiwiteite, soos voorgeskryf vir Suid-Afrikaanse toestande, op beton waterhoudende strukture te evalueer asook om te bepaal of dit ‘n kritiese lasgevalle sal wees. Vir hierdie doel is die interne kragte asook die area staal bewapening vir elk van die statiese en dinamiese lasgevalle vergelyk. Vergelykings is getref tussen die dinamiese en statiese resultate vir beide die swigtoestand en die diensbaarheidstoestand. Vir die bepaling van die interne kragte is gebruik gemaak van eindige element modelle. Tydens hierdie studie was drie eindige element modelle ondersoek en die akkuraatheid van elk geëvalueer op grond van die fundamentele frekwensie, die fondasie skuifkrag en die omkeermoment. Hierdie waardes was ondermeer bereken met twee numeriese metodes soos uiteengesit in Veletsos (1997) en Eurocode 8: Part 4 (2006). Die resultate dui daarop dat die invloed van seismiese aktiwiteite op beton waterhoudende strukture in Suid-Afrika nie weglaatbaar klein is nie en wel in berekening gebring behoort te word tydens die ontwerp. Die interne kragte vir beide die swigtoestand en diensbaarheidstoestand is aansienlik hoër vir die seismiese lasgeval as vir die statiese geval. Die diensbaarheidstoestand het deurentyd die ontwerp van beton waterhoudende strukture vir seismiese toestande oorheers.

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Certain regions within the Western Cape Province are at risk of a moderate intensity earthquake. It is therefore crucial that infrastructure in these areas be designed to resist its devastating effect. Numerous types of structural buildings exist in these seismic prone areas. The most common types are either reinforced concrete framed buildings with masonry infill or unreinforced masonry buildings. Many of these buildings predate the existence of the first loading code of 1989 which provided regulations for seismic design. The previous code was superseded in 2010 with a code dedicated to providing guidelines for seismic design of infrastructure. A concern was raised whether these buildings meet the requirements of the new code. A numerical investigation was performed on a representative reinforced concrete framed building with masonry infill to determine whether the building meets the new code’s requirements. The results from the investigation show that the stresses at critical points in the columns exceed the codified requirements, thus leading to local failure. After careful review it was discovered that these local failures in the columns will most likely lead to global failure of the building. / AFRIKAANSE OPSOMMING: In sekere streke in die Wes-Kaap bestaan daar risiko van matige intensiteit aardbewings. Dit is dus noodsaaklik dat die infrastruktuur in hierdie gebiede ontwerp word om die vernietigende uitwerking te weerstaan. Gebous met verskillende tipes strukturele uitlegte kom in hierdie gebied voor. Die mees algemene struktuur tipe is gewapende beton-raam geboue met baksteen invol panele sowel as ongewapende baksteen geboue. Baie van hierdie geboue is gebou voor die eerste las-kode van 1989 wat regulasies vir seismiese ontwerp voorsien in gebruik geneem is. Die vorige kode is vervang in 2010 met ’n kode toegewy tot die verskaffing van riglyne vir seismiese ontwerp van infrastruktuur. Kommer het ontstaan of hierdie geboue voldoen aan die vereistes van die nuwe kode. ’n Numeriese ondersoek is uitgevoer op ’n verteenwoordigende gewapende beton geraamde gebou met baksteen panele om te bepaal of die gebou voldoen aan die nuwe kode vereistes rakende sismiese ontwerp. Die resultate van die ondersoek toon dat die spanning op kritieke punte in die kolomme die gekodifiseerde vereistes oorskry, wat tot plaaslike faling lei. Na verdere onderssoek is dit bepaal dat die plaaslike faling in die kolomme waarskynlik tot globale faling van die gebou sal lei.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering; and, (M.S.)--Massachusetts Institute of Technology, Dept. of Architecture, 1981. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: p. 175-178. / by Joseph Gilmary Burns. / M.S.

Comparisons were made on the behavior of two full-sized reticulated domes subjected to uniform static loads only and uniform static loads with earthquake excitations. Space truss elements were used in the dome models. The stiffness matrix of the space truss element allows for the nonlinear strain-displacement behavior and the stress-strain behavior of the material is modeled with a bilinear approximation. The nonlinear solution technique is the Newton-Raphson method while the direct integration technique is the Newmark- Beta method. The joint displacements for the static and the dynamic analyses were compared for both domes along with the axial stresses in all members. The percentage increases in the axial stresses of the dynamic analyses as compared to those of the static analyses were determined. The reticulated domes used in the study were found to bet capable of withstanding the earthquake excitations when subjected to various uniform loads without failure. / Master of Science

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: South Africa has some regions which are susceptible to moderate seismic activity. A peak ground acceleration of between 0.1g and 0.15g can be expected in the southern parts of the Western Cape. Unreinforced Masonry (URM) is commonly used as a construction material for 2 to 4 storey buildings in underprivileged areas in and around Cape Town. URM is typically regarded as the material most vulnerable to damage when subjected to earthquake excitation. In this study, a three-storey URM building was analysed by applying seven earthquake time-histories, that can be expected to occur in South Africa, to a finite element model. Experimental data was used to calibrate the in- and out-of-plane stiffness of the URM. A linear modal dynamic analysis and non-linear implicit dynamic analysis were performed. The results indicated that tensile cracking of the in-plane piers was the dominant failure mode. The building relied on the postcracking capacity to resist the 0.15g magnitude earthquake. It is concluded that URM buildings of this type are at risk of failure especially if sufficient ductility is not provided. The results also showed that connection failure must be investigated further. Construction and material quality will have a large effect on the ability of typical URM buildings to withstand moderate magnitude earthquakes in South Africa. / AFRIKAANSE OPSOMMING: Sekere gebiede in Suid-Afrika het ’n risiko van matige seismiese aktiwiteit. Aardbewings met maksimum grondversnellings van tussen 0.1g en 0.15g kan in die suidelike gedeeltes van die Wes- Kaap voorkom. Twee- tot vier-verdieping onbewapende messelwerkgeboue kom algemeen voor in die lae sosio-ekonomiese gebiede van Kaapstad. Oor die algemeen word onbewapende messelwerkgeboue as die gebou-tipe beskou wat die maklikste skade opdoen tydens aardbewings. In hierdie studie is sewe aardbewings, wat tipies in Kaapstad verwag kan word, identifiseer en gebruik om ’n tipiese drie-verdieping onbewapende messelwerkgebou te analiseer. Eksperimentele data is gebruik om die materiaaleienskappe in die in-vlak asook uit-vlak rigtings te kalibreer. Beide ’n liniêre modale en nie-liniˆere implisiete dinamiese analises is uitgevoer. Die resultate dui daarop dat die dominante falingsmode die kraak van in-vlak messelwerk-tussenkolomme is. Die gebou moes sy plastiese kapasiteit benut om die 0.15g aardbewing te kan weerstaan. Die gevolgtrekking is dat dié tipe onbewapende messelwerkgeboue ’n risiko inhou om mee te gee, veral as genoegsame vervormbaarheid nie verskaf word nie. Die resultate toon ook dat konneksie-faling verder ondersoek moet word. Kwaliteit van vakmanskap en van materiaal het ’n groot invoed op die vermoë van onbewapende messelwerkgeboue om aardbewings van matige intensiteit in Suid-Afrika te weerstaan.

Shape Memory Alloys (SMAs) exhibit the ability to undergo large deformations but can recover permanent strains via heating (shape memory effect) or when stress is removed (superelastic effect). This study evaluates the comparative seismic performance of steel moment resisting frames (SMRFs) with innovative beam-to-column connections that use SMA bars as connecting elements. The performance evaluation studies are based on two types of SMA beam-to-column connections: (1) superelastic SMA connections with recentering capability; (2) martensitic SMA connections with high energy dissipation capacity. Fiber models for these SMA connections are implemented in the OpenSees finite element framework, and are verified against data from full-scale experimental tests that were performed on a prototype SMA connection in previous research at Georgia Tech. Three- and a nine-story model buildings with partially-restrained (PR) moment frames are selected from the SAC Phase II Project as case studies. Non-linear time history analyses on these model buildings, with and without SMA connections, are conducted using suites of ground acceleration records from the SAC Phase II project that represent different seismic hazard levels. Several SMA connections are designed for each structure, and their effect on peak and residual inter-story drift angles, connection rotations, and normalized dissipated hysteretic energy demands are investigated to determine the most suitable design. Finally, the seismic demands on the model buildings with conventional PR and selected SMA connections are evaluated in a probabilistic framework. The resulting seismic demand relationships are used to assess the effectiveness of the SMA connections in enhancing the building performance over a range of demand levels. The results of this performance evaluation show that the SMA connections are most effective in controlling structural response under high levels of seismic intensity leading to large deformation demands. In particular, the energy dissipating SMA connections are found to be effective in reducing maximum deformation demands, while the recentering SMA connections are more suitable for controlling residual deformations in the structure.

Earthquakes are among the most devastating and unpredictable of natural hazards that affect civil infrastructure and have the potential for causing numerous casualties and significant economic losses over large areas. Every region that has the potential for great earthquakes should have an integrated plan for a seismic design and risk mitigation for civil infrastructure. This plan should include methods for estimating the vulnerability of building inventories and for forecasting economic losses resulting from future events. This study describes a methodology to assess risk to distributed civil infrastructure due to large-scale natural hazards with large geographical footprints, such as earthquakes, hurricanes and floods, and provides a detailed analysis and assessment of building losses due to earthquake. The distinguishing feature of this research, in contrast to previous loss estimation methods incorporated in systems such as HAZUS-MH, is that it considers the correlation in stochastic demand on building inventories due to the hazard, as well as correlation in building response and damage due to common materials, construction technologies, codes and code enforcement. These sources of correlation have been neglected, for the most part, in previous research. The present study has revealed that the neglect of these sources of correlation leads to an underestimation of the estimates of variance in loss and in the probable maximum loss (PML) used as a basis for underwriting risks. The methodology is illustrated with a seismic risk assessment of building inventories representing different occupancy classes in Shelby County, TN, considering both scenario earthquakes and earthquakes specified probabilistically. It is shown that losses to building inventories estimated under the common assumption that the individual losses can be treated as statistically independent may underestimate the PML by a factor of range from 1.7 to 3.0, depending on which structural and nonstructural elements are included in the assessment. A sensitivity analysis reveals the statistics and sources of correlation that are most significant for loss estimation, and points the way forward for supporting data acquisition and synthesis.

L'objectif majeur de la présente thèse de doctorat est la validation structurelle d’une connexion hybride plancher-voile pour la reprise de l'action sismique dans les bâtiments en béton armé à voiles. Le manque de références normatives et scientifiques pour la caractérisation de ce type de système, nous a conduits à concevoir un protocole de caractérisation original basé principalement sur une analyse expérimentale à grande échelle du comportement de la liaison plancher-voile. Tout d'abord, nous présentons quelles ont été les problématiques et les exigences qui ont amené à l'innovation du rupteur de ponts thermiques SLABE, connexion hybride pour la jonction plancher-voile. Nous analysons ensuite les protocoles de caractérisation cyclique pour les systèmes structurels similaires ("coupling beams" ou "shearheads"). Sur base de cette réflexion, nous proposons un programme expérimental composé de trois séries d'essais: deux campagnes à grande échelle visant à restituer au mieux les configurations courantes de chargement dans un bâtiment (sollicitations horizontales et verticales), et une campagne d'essais d'ancrage. Ces essais sont capables de caractériser le comportement de la liaison dans les trois directions de l’espace. Les résultats de chaque campagne d'essais sont présentés dans le détail. Ils montrent notamment que la connexion étudiée, sous chargement cyclique, se comporte de façon quasi-élastique et stable pour les niveaux de charge correspondant aux sollicitations sismiques en France métropolitaine. De plus, ces essais ont souligné la grande réserve de ductilité du système, permettant une redistribution des efforts et contribuant ainsi à une meilleure robustesse du système, indispensable pour une sollicitation sismique présentant, par nature, un fort degré d’incertitude. Enfin, nous évaluons l'impact de la connexion plancher-voile sur le comportement structurel des bâtiments au travers d’une analyse structurelle sur des ouvrages de référence. Nous analysons la réponse modale et la redistribution des efforts entre les voiles de contreventement. Cette évaluation nous permet de définir une démarche de dimensionnement pour les ouvrages béton armé munis de ces éléments et de proposer des outils de calcul adaptés à l’ingénieur. L’exhaustivité de la démarche de validation présentée en fait une référence, déjà reconnue par les instances décernant les agréments techniques français, et qui pourrait être proposée comme protocole standard pour la validation des systèmes de rupteurs de ponts thermiques ou de liaison plancher-voile, au niveau européen. / The main objective of the PhD thesis is the structural evaluation of a hybrid structural connection at the slab-to-wall junction in concrete shear wall buildings under seismic action. The lack of normative and scientific literature for the characterization of this kind of systems leads us to devise an original protocol for the characterization which is mainly built on a large-scale experimental analysis of behaviour of the slab-towall connection. First, we explain the reasons that led us to design an innovative thermal break system, the SLABE, which is thermally insulated hybrid connection for the slab-to-wall junction. Then we analyse the existing protocols for the cyclic characterization of similar structural systems ("coupling beams" or "shearheads"). Based on the outcome of this investigation, we propose an experimental program composed with three test series: two large-scale campaigns where the actual loading conditions in a building are reproduced (horizontal and vertical shear forces) and an axial test campaign. The test results provided the required information to correctly characterize the behaviour of the hybrid connection in the three directions in space. The results of the experimental campaigns are presented in detail. In particular, they show that the connection, under cyclic loads, exhibits a quasi-elastic and stable behaviour at usual seismic load levels, in France. In addition, these tests highlight the large reserve of ductility of the system that guarantees the robustness of the system. This is essential for seismic actions which have by nature a high degree of uncertainty. The impact of the slab-to-wall connexion on the structural behaviour of buildings is evaluated through a structural analysis on representative structures. We particularly analyse the modal response and the force redistribution between the internal and external shear walls. Based on the outcome of this study, we suggest a seismic design method for reinforced concrete structures equipped with these structural elements. Along with that, we propose a computational tool for engineers. The completeness of the presented validation approach makes it a benchmark, already recognized by the French authorities granting technical approvals. It could be proposed as a standard protocol for the validation of other thermal break systems or hybrid slab-to-wall connections, at European level.