Post-tensioned timber buildings utilise a new construction technique developed largely as part of research undertaken at the University of Canterbury. Timber buildings are constructed using an engineered timber product, such as laminated veneer lumber (LVL), and then stressed with post-tensioned unbonded high-strength steel tendons. The tendons apply a compressive stress to timber members to create a ductile moment resisting connection between adjacent timber members. The major benefit of post-tensioned timber buildings is a significantly improved structural performance. As timber is a combustible material there is a perceived high fire risk in timber buildings. While timber buildings can be designed to perform very well in fire, a design guide for the fire safety design of post-tensioned timber buildings has not been previously developed. Furthermore, previous research has found that post-tensioned timber box beams may be susceptible to shear failure in fire conditions. This research investigated the fire performance of post-tensioned timber buildings. A design strategy for the fire performance of post-tensioned timber buildings was developed in conjunction with a simplified calculation method for determining the fire resistance of post-tensioned timber structural members. The fire performance and failure behaviour of post-tensioned timber box beam was also specifically investigated, with special focus given to the shear performance of box beams. A full scale furnace test of a LVL post-tensioned LVL box beam was conducted at the Building Research Association of New Zealand (BRANZ). Four further full scale tests of LVL box beams were conducted at ambient temperature at the University of Canterbury structural laboratory. Through this research two distinct strategies for the fire design of post-tensioned timber structures were developed. The first strategy is to rely on the residual timber of the members only. The second strategy considers specific fire protection of the post-tensioning system, which can then be used to contribute to the fire resistance of the member. The results of the full scale tests showed good agreement with the proposed the simplified calculation method. It was also determined that shear failure does not need to be specifically considered other than performing strength checks as for other design actions.

This study describes a method for conducting the structural dynamic analysis of a crane fly (family Tipulidae) forewing under different airflow conditions. Wing geometry is captured via micro-computed tomography scanning. A finite element model of the forewing is developed from the reconstructed model of the scan. The finite element model is validated by comparing the natural frequencies of an elliptical membrane with similar dimensions of the crane fly forewing to its analytical solution. Furthermore, a simulation of the fluid-structure interaction of the forewing under different airflows is performed by coupling the finite element model of the wing with a computation fluid dynamics model. From the finite element model, the mode shapes and natural frequencies are investigated; similarly, from the fluid-structure interaction, the time-varying out-of-plane deformation, and the coefficients of drag and lift are determined.

Yes / Over the last few decades, progressive collapse disasters have drawn the attention of codified bodies around the globe; as a consequence, there has been a renewed research interest. Structural engineering systems are prone to progressive collapse when subjected to abnormal loads beyond the ultimate capacity of critical structural members. Sudden loss of critical structural member(s) triggers failure mechanisms which may result in a total or partial collapse of the structure proportionate or disproportionate to the triggering event. Currently, researchers adopt different modelling techniques to simulate the loss of critical load bearing members for progressive collapse assessment. GSA guidelines recommend a column removal time less than a tenth of the period of the structure in the vertical vibration mode. Consequently, this recommendation allows a wide range of column removal time which produces inconsistent results satisfying GSA recommendation. A choice of a load time history function assumed for gravity and the internal column force interaction affects the response of the structure. This paper compares different alternative numerical approaches to simulate the sudden column removal in frame buildings and to investigate the effect of rising time on the structural response.

Because little was known about how the masonry lighthouses constructed during the 19th century at exposed locations around the British Isles were responding to wave action, the dynamic response of the Eddystone lighthouse under wave impacts was investigated. Like other so called 'rock lighthouses', the Eddystone lighthouse was built on top of a steep reef at a site that is fully submerged at most states of the tide. Consequently, the structure is exposed to loading by unbroken, breaking and broken waves. When the breaking occurs, wave loading leads to complex phenomena that cannot be described theoretically due to the unknown mixture of air and water involved during the wave-structure interaction. In addition, breaking waves are generally distinguished from unbroken and broken wave due to the fact that they cause impulsive loads. As a consequence, the load effects on the structural response require a dynamic analysis. In this investigation the dynamic response of the Eddystone lighthouse is investigated both in the field and by means of a small-scale model mounted in a laboratory wave channel. In particular, field data obtained by the use of geophones, cameras and a wave buoy are presented together with wave loading information obtained during the laboratory tests under controlled conditions. More than 3000 structural events were recorded during the exceptional sequence of winter storms that hit the South-West of England in 2013/2014. The geophone signals, which provide the structural response in terms of velocity data, are differentiated and integrated in order to obtain accelerations and displacements respectively. Dynamic responses show different behaviours and higher structural frequencies, which are related to more impulsive loads, tend to exhibit a predominant sharp peak in velocity time histories. As a consequence, the structural responses have been classified into four types depending on differences of ratio peaks in the time histories and spectra. Field video images indicate that higher structural frequencies are usually associated with loads caused by plunging waves that break on or just in front of the structure. However, higher structural velocities and accelerations do not necessarily lead to the largest displacements of around a tenth of mm. Thus, while the impulsive nature of the structural response depends on the type of wave impact, the magnitude of the structural deflections is strongly affected by both elevation of the wave force on the structure and impact duration, as suggested by structural numerical simulations and laboratory tests respectively. The latter demonstrate how the limited water depth strongly affects the wave loading. In particular, only small plunging waves are able to break on or near the structure and larger waves that break further away can impose a greater overall impulse due to the longer duration of the load. As a consequence of the depth limited conditions, broken waves can generate significant deflections in the case of the Eddystone lighthouse. However, maximum accelerations of about 0.1g are related to larger plunging waves that are still able to hit the lighthouse with a plunging jet. When compared to the Iribarren number, the dimensionless irregular momentum flux proposed by Hughes is found to be a better indicator concerning the occurrence of the structural response types. This is explained by the fact that the Iribarren number does not to take into account the effects of the wide tidal range at the Eddystone reef, which has a strong influence on the location of the breaking point with respect to the lighthouse. Finally, maximum run up were not able to rise up to the top of the lighthouse model during the laboratory tests, despite this having been observed in the field. As a consequence, the particular configuration of the Eddystone reef and the wind could have a considerable bearing and exceptional values of the run up, greater than 40 m, cannot be excluded in the field.

The concept of using aluminum as the primary construction material for high speed ships and the hydroelastic behavior of the structure is widely gaining importance as a significant research topic in naval architecture. Aluminum is lighter than steel and hence can be predominantly used in high speed crafts which experiences significant slamming. This thesis work is focused on wedge shaped models. Free fall wedge impact is studied and a FORTRAN 90 computer program is developed to estimate the structural response of the wedge experiencing slamming by the use of matrix methods, finite element techniques and Newmark-Beta numerical time integration methods. The numerical solution is validated by comparison with the static solution. The theoretical hydrodynamic pressures which are used as input for this work was originally developed by using a flat cylinder theory [26]. The wedge drop at 0.6096 m (24 inch) drop height with an impact veloc- ity of v=3.05 m/s is based as the premise and the experimental pressure distributions measured by the pressure-transducers and the theoretical pressure predictions are used as inputs and the structural response is derived. Additionally, the response is compared for three different plate thicknesses and the results are compared against each other. The maximum deflection is comparable to the deflection evaluated from the experiment and tends to attain convergence as well. As the plate thickness reduces there tends to be a significant rise in the deflection values for the wedge plate, in the manner that when the plate thickness is halved there is a deviation of more than 75% in the deflection values as such.

This study uses dynamic centrifuge tests and three-dimensional (3D), nonlinear finite-difference analyses to: (1) evaluate the effect of soil-cement grid reinforcement on the seismic response of a deep soft soil profile, and (2) to examine the dynamic response of structures supported by shallow foundations on soft clay reinforced by soil-cement grids. The soil profile consisted of a 23-m-thick layer of lightly over-consolidated clay, underlain and overlain by thin layers of dense sand. Centrifuge models had two separate zones for a total of four different configurations: a zone without reinforcement, a zone with a "embedded" soil-cement grid which penetrated the lower dense sand layer and had a unit cell area replacement ratio Ar = 24%, a zone with an embedded grid with Ar = 33%, and a zone with a "floating" grid in the upper half of the clay layer with Ar = 33%. Models were subjected to a series of shaking events with peak base accelerations ranging from 0.005 to 0.54g. The results of centrifuge tests indicated that the soil-cement grid significantly stiffened the site compared to the site with no reinforcement, resulting in stronger accelerations at the ground surface for the input motions used in this study. The response of soil-cement grid reinforced soft soil depends on the area replacement ratio, depth of improvement and ground motion characteristics. The recorded responses of the structures and reinforced soil profiles were used to define the dynamic moment-rotation-settlement responses of the shallow foundations across the range of imposed shaking intensities. The results from centrifuge tests indicated that the soil-cement grids were effective at controlling foundation settlements for most cases; onset of more significant foundation settlements did develop for the weakest soil-cement grid configuration under the stronger shaking intensities which produced a rocking response of the structure and caused extensive crushing of the soil-cement near the edges of the shallow foundations. Results from dynamic centrifuge tests and numerical simulations were used to develop alternative analysis methods for predicting the demands imposed on the soil-cement grids by the inertial loads from the overlying structures and the kinematic loading from the soil profile's dynamic response. / Ph. D.

This study presents a ground-motion selection and scaling procedure that preserves the inherent uncertainty in the modified recordings. The proposed procedure provides a set of scaled ground-motion records to be used in the response estimation of structural systems for a pre-defined earthquake hazard level. Given a relatively larger ground-motion dataset, the methodology constrains the selection and scaling of the accelerograms to the differences between individual records and corresponding estimations from a representative ground-motion predictive model. The procedure precisely calculates the distribution parameters of linear structural systems whereas it provides estimations of these parameters for nonlinear structural response. Thus this method is not only useful for ground-motion selection and scaling but also for probability based performance assessment studies. The proposed procedure is also capable of matching with a pre-defined target elastic response spectrum and corresponding variance over a period range. Case studies that compare the performance of the proposed procedure with some other record selection and scaling methods suggest its usefulness for the accurate verification of structural systems and rapid loss estimation studies.

Made available in DSpace on 2015-03-26T13:28:01Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1698447 bytes, checksum: 33bc2ee8eb9cdc0043c10b9a19d26c8e (MD5) Previous issue date: 2011-02-04 / The purpose of this work was to analyze the resilient behavior of the typical soils from Viçosa-MG, employed in the subgrade and the reinforcement pavement in a hypothetical flexible pavement. The following tests were performed to characterize the resilient response of soils: Geotechnical characterization, soil compaction (the compactive efforts used for this study were the standard Proctor and intermediate Proctor), California Bearing Ratio tests, triaxial conventional tests (unconsolidatedundrained or UU test), repeated-loading triaxial tests for determining the resilient modulus of soils (according to with the requirements of AASHTO T 307-99 and DNER-ME 131/94 specifications). Through the test results achieved in the test laboratory equations were developed for predicting the resilient modulus of soils used to obtain the pavement structural response model using the Everstress software. The main studies in this research were: (i) Analysis and interpretation of results of laboratory tests, above all resilient modulus obtained by methods outlined above; (ii) Study of the results of stress and displacement in the floor structure based on predictive models of resilient modulus expressed in terms of the first invariant of stress and stress deviation. / Este trabalho teve por objetivo analisar o comportamento resiliente de três solos típicos da região de Viçosa-MG, quando supostamente empregados no subleito e na camada de reforço de um pavimento flexível hipotético. Para cumprir esta finalidade, foram realizados os seguintes ensaios: caracterização geotécnica, compactação, empregando-se as energias do Proctor normal e intermediário, índice de suporte Califórnia, triaxial convencional do tipo não consolidado e não drenado (triaxial UU) e triaxial de cargas repetidas (este último para a determinação do módulo de resiliência dos solos), empregando-se as normas AASHTO T 307-99 e DNER-ME 131/94. Através dos resultados dos ensaios alcançados no laboratório, obtiveram-se várias equações para previsão do módulo de resiliência dos solos em questão e algumas delas foram utilizadas no programa Everstress para estudo da resposta estrutural do pavimento. Os principais estudos desta pesquisa foram: (i) análise e interpretação dos resultados dos ensaios de laboratório, especificamente os de módulo de resiliência obtidos pelo emprego das metodologias anteriormente citadas em duas energias de compactação; (ii) apreciação dos resultados de tensão e deslocamento na estrutura do pavimento quando da utilização dos modelos de previsão de módulo de resiliência expressos em função do primeiro invariante de tensão e da tensão desvio.

No description available.

Recent events including deliberate terrorist attacks and accidental explosions have highlighted the need for comprehensive research in the area of structural response to blast loading. Research in this area has recently received significant attention by the civil engineering community. Reinforced Concrete (RC) water reservoir tanks are an integral part of the critical infrastructure network of urban centers and are vulnerable to blast loading. However, there is a lack of research and knowledge on the performance of RC reservoir walls under blast loading. The objective of this research study is to experimentally investigate the performance of reinforced concrete reservoir walls subjected to blast loading and to analyze the structural response. This study provides experimental test data on the performance of reinforced concrete reservoir walls under blast loading and complementary analytical predictions using the Singe-Degree-Of-Freedom (SDOF) analysis method. The reservoir walls in this study were designed according to the water volume capacity using the Portland Cement Association (PCA 1993) methodology. The design was validated using software SAP 2000. The experimental program involved the construction and simulated blast testing of two RC reservoir wall specimens with different support conditions: (1) two opposite lateral edges fixed, bottom edge pinned and top edge free; and (2) two opposite lateral edges fixed, and bottom and top edges free. The first boundary condition was intended to promote two-way bending action, while the second was dominated by one-way bending. The two specimens were each subjected to a total of six consecutive incrementally increasing blast tests. The experimental program was conducted in the shock tube testing facility that is housed in the University of Ottawa. Wall displacements, reinforcement strains, and reflected pressures and impulses were measured during testing. Analytical calculations were conducted using the equivalent SDOF method to simulate the dynamic response of the RC reservoir wall specimens under different blast loadings. Published tables, charts and coefficients contained in Biggs (1964) and UFC 3-340-02 (2008) were adopted in the equivalent SDOF calculations. The analytical results were compared against the ii experimental data. The SDOF method predicted smaller displacements than those recorded during testing. The approximate nature of the parameters and tables used in the equivalent SDOF calculations contributed to the discrepancy between the analytical and experimental results. Furthermore, assumptions regarding the support conditions and neglecting residual damage from previous blast tests contributed to the underestimation of the displacements.