Thesis (M.S.)--Auburn University, 2008. / Abstract. Includes bibliographical references (p. 187-189).

Thesis (Ph. D.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 191-204). Also available on the World Wide Web.

Thesis (M.S.)--University of Wisconsin, 1962. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (p. 29-31).

Identifying damage of a bridge from a vehicle moving over it is an attractive idea especially for those bridges without structural health monitoring systems as it is faster than putting sensors on the bridges. Many parts of highways and railways have been constructed on bridges and it is important to ensure that they are in good conditions. Therefore a large amount of bridges need to be monitored and for the sake of economy the monitoring should be efficient. If an instrumented vehicle can identify the occurrence and locations of damage by running over the bridges, it would save a lot of labor and time. As acceleration is easier to acquire, it is used as the main signal for damage detection. Research in this area is relatively little, not to mention the need to take into account road surface roughness and experimental verification. Frequencies can be conveniently extracted from the vehicle response. The damage can hence be identified based on the relationship between the change of frequencies and the fractional change of strain energy. A vehicle-bridge interaction system is used to simulate the process of a vehicle running over a bridge and obtain the vehicle response for investigation. The proposed method can identify damage of simply supported and multi-span continuous bridges taking into account road surface roughness and measurement noise. They are also validated in the laboratory where a simply supported bridge is modeled using an aluminum beam and the vehicle is modeled with aluminum vehicles. This method can limit the damage location to two potential locations. The multi-level multi-pass strategy makes use of the identification from the above method, applies genetic algorithm and lets the vehicle run over the bridge at various speeds. The unique damage location can then be identified. A numerical study for simply supported bridges and multi-span continuous bridges has verified its effectiveness. Continuous wavelet transform (CWT) can identify local changes in a signal as damage is assumed to cause local change to the vehicle response, which makes it suitable for damage detection from vehicle response. However, the road surface roughness and measurement noise often mask the information about damage. Smoothing technique and damage indicators are proposed to help with the identification. By validating the method with a numerical vehicle-bridge interaction system and model tests in the laboratory, the damage can be correctly identified. Additional masses and sinusoidal excitation force can help with the identification too. Repeated application of CWT involves applying the CWT to the coefficients of continuous wavelet again and again, which can also improve the results. If CWT is treated as a mathematical microscope, repeated application of CWT is like amplifying the signal several times. The effectiveness of the method has been verified numerically and experimentally. In summary, a convenient and efficient technique to test the conditions of bridges by putting sensors on a moving vehicle is proposed and the method is verified by numerical and experimental studies. It can provide an alternative or a useful complement to conventional structural health monitoring systems. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

Thesis (M.S.)--Missouri University of Science and Technology, 2009. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed May 27, 2009) Includes bibliographical references (p. 72-74).

Progressive collapse is a failure mechanism that causes local damage of one structural element to progress throughout the whole structure leading to collapse of the entire structure. Recent catastrophic structural collapses in the world have drawn attention from structural engineers to the importance of designing structures that will continue to be operational even after some local failures occur. For some bridge types, although the design of each single member follows the proper design standards, they still cannot provide sufficient degree of redundancy to withstand a local failure without the total collapse of the entire structural system. In this study, two truss-type bridges, a half-through pedestrian bridge and a through-truss bridge, are investigated. The design configurations follow the AASHTO specifications, and they are usually classified as fracture-critical, non-redundant structures. Furthermore, traditional design and evaluation procedures generally classify through-truss bridges as single-load-path structures. However, due to the configuration of this bridge type, alternative load paths in the bridge could exist, indicating that this type of structural system has the ability to continue sustaining further loads after one of its members reaches its ultimate capacity by using different load paths. It is important to note that, since the structural load-carrying capacity strongly depends on the location of the damaged area, the progressive collapse mechanism of a structure could change substantially under different damage conditions. For the pin-connected pedestrian bridge model, the analysis showed that the failure of a local member is not responsible for the bridge’s collapse. Instead, it is the global buckling (instability) of top chord system that led the bridge to collapse. A modified 2D structure was studied to properly match the buckling load and its associated deformed shape with those obtained in the 3D model’s top chord system. The conclusions of this study verified that the collapse mechanism of this type of bridge is linked to the instability of the top chord system. For the same pedestrian bridge with beam-type connection, the bridge’s failure mechanism is instead associated with the local buckling of an upper chord element that led the bridge to collapse. Therefore, the pedestrian bridge should not be considered a fracture-critical structure since the failure mechanisms that led to its collapse were associated with large compression forces in the upper chord. Looking at deterioration effects on bridge performance, corrosion is one of the dominant causes of deterioration in steel bridges due to aggressive environment and inadequate maintenance. The effects of corrosion damage could alter significantly the bridge behavior depending on the extent of deterioration on the bridge structure. Comprehensive nonlinear analyses were conducted to investigate the changes in collapse mechanisms considering various corrosion level and different corroded locations. Results from the deteriorated pedestrian bridge analyses showed that the deterioration of corroded top chord members could significantly reduce the load-carrying capacity of the bridge and lead the structure to sudden catastrophic failure even for a load lower than the one used in the original design. For the through-truss bridge model, the cases with a corroded middle diagonal member revealed similar load-carrying capacities and collapse mechanisms to the undamaged bridge. These models show similar collapse mechanisms, related to the bending failure of the middle bottom chord and the local buckling of the middle top chord. When the corrosion of the top chord element is severe, the collapse mechanism of the bridge is still linked to the buckling failure of upper chord together with the bending failure of the middle bottom chord. However, the load-carrying capacity of this damaged bridge could drop considerably when compared to that of the undamaged model. Among all the cases analyzed in this study, the corrosion of the end post element represents the most critical case: here, the results indicated a considerable decrease in the load-carrying capacity of this damaged bridge model when compared to that of the undamaged bridge. In addition, this study also focused on the effects of support settlements on the load-carrying capacity and on the collapse mechanism of deteriorated bridges. It was found that, even with only a slight differential settlement support, the bridge model with a localized corroded diagonal element reached its ultimate capacity much earlier in the loading process than the bridge with fixed boundaries, with a reduction of the original load-carrying capacity of about 15%.

Modern societies increasingly depend on the reliable functioning of urban infrastructure systems in the aftermath of natural disasters such as hurricane and earthquake events. Apart from a sizable capital for maintenance and expansion, the reliable performance of infrastructure systems under extreme hazards also requires strategic planning and effective resource assignment. Hence, efficient system reliability and risk assessment methods are needed to provide insights to system stakeholders to understand infrastructure performance under different hazard scenarios and accordingly make informed decisions in response to them. Moreover, efficient assignment of limited financial and human resources for maintenance and retrofit actions requires new methods to identify critical system components under extreme events. Infrastructure systems such as highway bridge networks are spatially distributed systems with many linked components. Therefore, network models describing them as mathematical graphs with nodes and links naturally apply to study their performance. Owing to their complex topology, general system reliability methods are ineffective to evaluate the reliability of large infrastructure systems. This research develops computationally efficient methods such as a modified Markov Chain Monte Carlo simulations algorithm for network reliability, and proposes a network reliability framework (BRAN: Bridge Reliability Assessment in Networks) that is applicable to large and complex highway bridge systems. Since the response of system components to hazard scenario events are often correlated, the BRAN framework enables accounting for correlated component failure probabilities stemming from different correlation sources. Failure correlations from non-hazard sources are particularly emphasized, as they potentially have a significant impact on network reliability estimates, and yet they have often been ignored or only partially considered in the literature of infrastructure system reliability. The developed network reliability framework is also used for probabilistic risk assessment, where network reliability is assigned as the network performance metric. Risk analysis studies may require prohibitively large number of simulations for large and complex infrastructure systems, as they involve evaluating the network reliability for multiple hazard scenarios. This thesis addresses this challenge by developing network surrogate models by statistical learning tools such as random forests. The surrogate models can replace network reliability simulations in a risk analysis framework, and significantly reduce computation times. Therefore, the proposed approach provides an alternative to the established methods to enhance the computational efficiency of risk assessments, by developing a surrogate model of the complex system at hand rather than reducing the number of analyzed hazard scenarios by either hazard consistent scenario generation or importance sampling. Nevertheless, the application of surrogate models can be combined with scenario reduction methods to improve even further the analysis efficiency. To address the problem of prioritizing system components for maintenance and retrofit actions, two advanced metrics are developed in this research to rank the criticality of system components. Both developed metrics combine system component fragilities with the topological characteristics of the network, and provide rankings which are either conditioned on specific hazard scenarios or probabilistic, based on the preference of infrastructure system stakeholders. Nevertheless, they both offer enhanced efficiency and practical applicability compared to the existing methods. The developed frameworks for network reliability evaluation, risk assessment, and component prioritization are intended to address important gaps in the state-of-the-art management and planning for infrastructure systems under natural hazards. Their application can enhance public safety by informing the decision making process for expansion, maintenance, and retrofit actions for infrastructure systems.

Earthquake ground motion can induce out-of-phase vibrations between adjacent structures due to differences in dynamic characteristics, which can result in impact or pounding of the structures if the at-rest separation is insufficient to accommodate the relative displacements. In bridges, seismic pounding between adjacent decks or between deck and abutment can result in localized deck damage, bearing failure, damage to shear keys and abutments, and even contribute to the collapse of bridge spans. This study investigates pounding in bridges from an analytical perspective. A simplified nonlinear model of a multiple-frame bridge is developed in MATLAB incorporating the effects of inelastic frame action, nonlinear hinge behavior and abutments. The equations of motion of the bridge response to longitudinal ground excitation are assembled and solved using the fourth-order Runge-Kutta method. Pounding is simulated using contact force-based models such as the linear spring, Kelvin and Hertz models, as well as the momentum-based stereomechanical method. In addition, a Hertz contact model with nonlinear damping (Hertzdamp model) is also introduced to model impact. The primary factors controlling the pounding response are identified as the frame period ratio, ground motion effective period ratio, restrainer stiffness ratio and frame ductility ratio. Pounding is most critical for highly out-of-phase frames. Impact models without energy dissipation overestimate the stiff system displacements by 15%-25% for highly out-of-phase, elastic systems experiencing moderate to strong ground excitation. The Hertzdamp model is found to be the most effective in representing impact. Traditional column hysteresis models such as the elasto-plastic and bilinear models underestimate the stiff system amplification and overestimate the flexible system amplification due to impact, when compared with stiffness and strength degrading models. Strength degradation and pounding are critical on the stiff system response to near field ground motions, for highly out-of-phase systems. Current design procedures are adequate in capturing the nonlinear hinge response when the bridge columns are elastic, but require revisions such as the introduction of time dependent reduction factors, and a frame design period to work for inelastic situations. Finally, a bilinear truss element with a gap is proposed for implementing energy dissipating impact models in commercial structural software.

Extreme rainfall events associated with global warming are likely to produce an increasing number of flooding scenarios. A large magnitude of hydrologic events can often result in submerged orifice flow (also called pressure flow) or embankment and bridge overtopping flow, in which the foundation of a bridge is subjected to severe scour at the sediment bed. This phenomenon can cause bridge failure during large floods. However, current laboratory studies have focused on only cases of free-surface flow conditions, and they do not take bridge submergence into account. In this study, abutment scour experiments were carried out in a compound channel to investigate the characteristics of abutment scour in free-surface flow, submerged orifice flow, and overtopping flow cases. Detailed bed contours and three components of velocities and turbulent intensities were measured by acoustic Doppler velocimeters. The results show that the contracted flow around an abutment because of lateral and/or vertical contraction and local turbulent structures at the downstream region of the bridge are the main features of the flow responsible for the maximum scour depth around an abutment. The effects of local turbulent structures on abutment scour are discussed in terms of turbulent kinetic energy (TKE) profiles measured in a wide range of flow contraction ratios. The experimental results showed that maximum abutment scour can be predicted by a suggested single relationship even in different flow types (i.e., free, submerged orifice, and overtopping flow) if the turbulent kinetic energy and discharge under the bridge can be accurately measured.

[ES] Las inundaciones pueden llegar a desestabilizar los vehículos y estos, a su vez, pueden exacerbar los efectos negativos de las inundaciones cuando son arrastrados por el flujo, generando no solamente pérdidas económicas sino también de vidas humanas. En las ciudades, la mayor parte de las muertes durante las inundaciones ocurre al interior de los vehículos debido a que los conductores intentan cruzar con sus vehículos por zonas inundadas (Jonkzman and Kelman 2005; Drobot et al. 2007; Kellar and Schmidlin 2012). En países desarrollados, un alto porcentaje de estas muertes ocurre durante inundaciones relámpago cuando los conductores intentan cruzar por zonas inundadas en lugar de evitarlas (Fitzgerald et al. 2010; Kellar y Schmidlin 2012). Debido a esto, en áreas sujetas a inundaciones relámpago, casi la mitad de las víctimas son pasajeros atrapados en sus vehículos (Versini et al. 2010a) Entre las partes de las vías que resultan afectadas por las crecidas de los ríos se encuentran los puentes, las cuales son obras de infraestructura muy importantes. Un alto porcentaje de los fallos de los puentes a nivel mundial se presenta debido a las crecidas de los ríos, lo cual tiene un impacto negativo en los vehículos y los sistemas de transporte. Debido a esto, con el fin de realizar una adecuada gestión de las inundaciones es necesario determinar el riesgo de inestabilidad al que están sometidos los vehículos en una zona inundable. Sin embargo, a pesar del impacto negativo de las inundaciones, hasta la fecha se dispone de pocos estudios que permitan determinar los efectos negativos que las condiciones climáticas generan sobre los sistemas de transporte (Molarius et al., 2014). En esta investigación se desarrolló una nueva metodología para calcular este riesgo a partir de las características de las crecidas, los puentes, los vehículos, y el tráfico vehicular. Esta metodología fue generada a partir de una estructura conceptual y un desarrollo matemático novedosos y permite determinar el riesgo a través de la integral estadística de la amenaza de inestabilidad y la vulnerabilidad de los coches. En áreas urbanas y en las intersecciones entre las corrientes de agua y las vías, la amenaza se establece a través de una función de estabilidad de autos parcialmente sumergidos, las características geométricas de los vehículos y las características hidrodinámicas de las crecidas (calados y velocidades) y su probabilidad de ocurrencia, mientras que la vulnerabilidad se calcula por medio de la combinación de la susceptibilidad y la exposición de los coches. En puentes, la peligrosidad se obtiene a través del análisis de los datos de caudal disponibles y la vulnerabilidad mediante el análisis del estado estructural del puente, las características de la cuenca y del cauce aguas arriba y aguas abajo de la estructura, la estabilidad del canal y la potencial acumulación de acarreos. La metodología desarrollada se implementó para determinar el riesgo en los siguientes casos de estudio, los cuales están localizados en territorio español: (i) en las áreas urbanas correspondientes a los municipios de Alfafar y Massanassa, (ii) en los sitios de intersección entre vías y ríos localizados en el municipio de Godelleta; y (iii) en 12 puentes fluviales. Los resultados obtenidos podrían estar indicando que el método propuesto tiene en cuenta los elementos más importantes que deben considerarse al establecer este tipo de riesgo. La metodología desarrollada permite obtener un panorama detallado del riesgo de desestabilización de los vehículos debido a inundaciones en una zona determinada. En consecuencia, la implementación de esta metodología puede ayudar a disminuir los efectos negativos antes y durante este tipo de eventos, resultando de gran ayuda para las entidades encargadas de la planificación urbana y de la protección civil con el fin de diseñar e implementar acciones que permitan disminu / [CAT] Les inundacions poden desestabilitzar els vehicles i aquests, al mateix temps, poden exacerbar els efectes negatius de les inundacions quan són arrossegats pel flux, generant no solament pèrdues econòmiques sinó també de vides humanes. A les ciutats, la major part de les morts durant les inundacions ocorre a l'interior dels vehicles pel fet que els conductors intenten creuar amb els seus vehicles per zones inundades (Jonkzman and Kelman 2005; Drobot et al. 2007; Kellar and Schmidlin 2012). En països desenvolupats, un alt percentatge d'aquestes morts ocorre durant inundacions llampec quan els conductors intenten creuar per zones inundades en lloc d'evitar-les (Fitzgerald et al. 2010; Kellar i Schmidlin 2012). A causa d'això, en àrees subjectes a inundacions llampec, quasi la meitat de les víctimes són passatgers atrapats en els seus propis vehicles (Versini et al. 2010a) Entre les parts de les vies que resulten afectades per les crescudes dels rius es troben els ponts, les quals són obres d'infraestructura molt importants. Un alt percentatge de les fallades dels ponts a nivell mundial es presenta com a conseqüència de les crescudes dels rius, la qual cosa té un impacte altament negatiu en els vehicles i els sistemes de transport.. A causa d'això, amb la finalitat de realitzar una adequada gestió de les inundacions és necessari determinar el risc d'inestabilitat al qual estan sotmesos els vehicles en una zona inundable. No obstant això, malgrat l'impacte negatiu de les inundacions, fins a la data es disposa de pocs estudis que permeten determinar els efectes negatius que les condicions climàtiques generen sobre els sistemes de transport (Molarius et al., 2014). En la present investigació es va desenvolupar una nova metodologia per a calcular aquest risc a partir de les característiques de les crescudes, els ponts, els vehicles, i el trànsit vehicular. Aquesta metodologia va ser generada a partir d'una estructura conceptual i un desenvolupament matemàtic nous i permet determinar el risc a través de la integral estadística de l'amenaça d'inestabilitat i la vulnerabilitat dels cotxes. En àrees urbanes i en les interseccions entre els corrents d'aigua i les vies, l'amenaça s'estableix a través d'una funció d'estabilitat de cotxes parcialment submergits, les característiques geomètriques dels vehicles i les característiques hidrodinàmiques de les crescudes (calats i velocitats) i la seua probabilitat d'ocurrència, mentre que la vulnerabilitat es calcula per mitjà de la combinació de la susceptibilitat i l'exposició dels cotxes. En ponts, la perillositat s'obté a través de l'anàlisi de les dades de cabal disponibles i la vulnerabilitat mitjançant l'anàlisi de l'estat estructural del pont, les característiques de la conca i del llit aigües amunt i aigües avall de l'estructura, l'estabilitat del canal i la potencial acumulació d'enderrocs. La metodologia desenvolupada es va implementar per a determinar el risc en els següents casos d'estudi, els quals estan localitzats en territori espanyol: (i) en les àrees urbanes corresponents als municipis d'Alfafar i Massanassa, (ii) en els llocs d'intersecció entre vies i rius localitzats en el municipi de Godelleta; i (iii) en 12 ponts fluvials. Els resultats obtinguts podrien estar indicant que el mètode proposat té en compte els elements més importants que han de considerar-se en establir aquest tipus de risc. La metodologia desenvolupada permet obtindre un panorama detallat del risc de desestabilització dels vehicles a causa d'inundacions en una zona determinada. En conseqüència, la implementació d'aquesta metodologia pot ajudar a disminuir els efectes negatius abans i durant aquesta mena d'esdeveniments, resultant de gran ajuda per a les entitats encarregades de la planificació urbana i de la protecció civil amb la finalitat de dissenyar i implementar accions que permeten disminuir els efectes negatius de les inundacions. / [EN] Flooding can destabilize vehicles which might, in turn, exacerbate the negative effects of floods when vehicles are swept away by flows, leading to economic loss and fatalities. The main cause of death in cities during flood events corresponds to cars being swept away when they are driven by flooded roads (Jonkzman and Kelman 2005; Drobot et al. 2007; Kellar and Schmidlin 2012). In developed countries a high percentage of these deaths occurs during flash floods when drivers try to cross overflowing water bodies instead of avoiding them (Fitzgerald et al. 2010; Kellar and Schmidlin 2012). Hence, in areas subject to flash floods almost half of the victims are passengers trapped inside their own vehicles (Versini et al. 2010a). Among the parts of the roads that are most affected by floods are bridges, which are very important infrastructure works for society. Because of this, a high percentage of bridge failures worldwide occur as a result of river floods, which has highly negative impacts for vehicles and transportation systems. Therefore, in order to suitably manage floods, it is necessary to determine the risk of instability to which vehicles in flood-prone areas are subject. However, Despite the negative impact of floods, very few studies have centred on determining the negative effects of floods on transport systems (Molarius et al., 2014). In this research, a new methodology to estimate this risk based on the characteristics of vehicles, floods, bridges and vehicular traffic was developed. This methodology was generated from a novel conceptual structure and mathematical development and allows to determine the risk by the statistical integral of the instability hazard and the vehicles' vulnerability. In urban areas and stream crossings, the hazard is determined by a stability criterion of partially submerged cars, the geometric characteristics of the vehicles and the hydrodynamic characteristics of the floods (depths and velocities) and their probability of occurrence, while vulnerability is calculated by combining the susceptibility and exposure of cars. In bridges, the hazard is obtained by analysing available discharge data and the vulnerability by examining the structural condition of the bridge, the characteristics of the watershed and watercourse upstream and downstream of the structure, the stability of the channel and the potential accumulation of debris. The developed methodology was implemented to determine the risk in the following case studies, which are located in Spanish territory: (i) in the urban areas corresponding to the towns of Alfafar and Massanassa; (ii) in the stream crossings located in the municipality of Godelleta; and (iii) in 12 river bridges located. The results obtained could be indicating that the proposed method takes into account the most important elements to be considered when establishing this type of risk. The developed methodology provides a detailed vision of the vehicle instability risk due to flooding in a given area. Consequently, implementing this methodology can help to reduce negative effects before and during flooding events, which is extremely helpful for those organizations in charge of urban planning and civil protection to design and take actions that cushion the negative effects of flooding. / I thank Colciencias for financing this research through call 728-2015. / Bocanegra Vinasco, RA. (2020). Evaluation of the risk due to fluvial flooding in vehicles and road infrastructures at basin scale [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/157654 / TESIS