Dissertations / Theses on the topic 'Bridge Collapses'

The Deck truss portion of the I-35W Highway Bridge in Minneapolis, Minnesota collapsed on August 1, 2007 while roadwork was underway on the bridge. The entire truss was recovered from the river to study the causes of failure. The National Transportation Safety Board attributes the collapse to inadequate load carrying capacity of the steel gusset plates connecting the main truss members at four specific nodes. Permanent deformations of the members in proximity to these nodes were documented and a surveillance video camera recorded the collapse event in a major section of the structure.
The inelastic behavior of the deck truss during the collapse event is studied in this research by performing nonlinear structural analysis on a simplified two-dimensional model. Nonlinear behavior is discretized at specific locations starting with buckling of the critical gusset plates and continuing with yielding in members where the internal forces increased at a higher rate during the post-buckling behavior.
The analysis results show the sequence of failure events that lead to the formation of a collapse mechanism in the center span of the deck truss, which is the first to fall into the river. Comparison between the available evidence and the analysis results validate the conclusions drawn in this research.
Master of Science

[Truncated abstract] As a consequence of the increase in terrorist incidents, many comprehensive researches, both experimental and numerical modelling of structure and blast interaction, have been conducted to examine the behaviour of civilian structures under dynamic explosion and its impact. Nevertheless most of the works in literature are limited to response of simple structures such as masonry walls, reinforced concrete beams, columns and slabs. Although these studies can provide researchers and structural engineers a good fundamental knowledge regarding blast load effect, it is more likely for blast load to act upon entire structures in actual explosion events. The interaction between blast load and structures, as well as the interaction among structural members may well affect the structural response and damage. Therefore it is necessary to analyse more realistic reinforced concrete structures in order to gain an extensive knowledge on the possible structural response under blast load effect. Among all the civilian structures, bridges are considered to be the most vulnerable to terrorist threat and hence detailed investigation in the dynamic response of these structures is essential. This thesis focuses on the study of the response of a modern cable-stayed bridge under blast loadings. ... Firstly, analysis is conducted to examine the failure of four main components namely pier, tower, concrete back span and steel composite main span under close proximity dynamic impact of a 1000 kg TNT equivalent blast load. Secondly, based on such results, the remainder of the bridge structure is then tested by utilizing the loading condition specified in the US Department of Defence (DoD) guideline with the aim to investigate the possibility of bridge collapse after the damage of these components. It is found that failure of the vertical load bearing elements (i.e. pier and tower) will lead to catastrophic collapse of the bridge. Assuming that terrorist threat cannot be avoided, hence protective measures must be implemented into the bridge structure to reduce the damage induced by explosive blast impact and to prevent bridge from collapse. As such, a safe standoff distance is determined for both the pier and tower under the blast impact of 10000 kg TNT equivalent. This information would allow the bridge designer to identify the critical location for placing blast barriers for protection purpose. For the case of bridge deck explosion, carbon fibre reinforced polymer (CFRP) is employed to examine in respect of its effectiveness in strengthening the concrete structure against blast load. In this research, appropriate contact is employed for the numerical model to account for the epoxy resin layer between the CFRP and concrete. In addition, to ensure that the CFRP can perform to its full capacity, anchors are also considered in the numerical study to minimize the chance of debonding due to the weakening of the epoxy. The results reveal that although severe damage can still be seen for locations in close proximity to the explosive charge, the use of CFRP did reduce the dynamic response of the bridge deck as compared to the unprotected case scenario. Further investigation is also carried out to examine the change in damaged zone and global response through variation in CFRP thickness.

The seismic design maps on ASCE 7-05, International Building Code- 2006/2009, assumed uniform hazard ground motion with 2% probability of exceedance in 50 years for the entire conterminous U.S. But, Luco et al in 2007 pointed out that as uncertainties in collapse capacity exists in structures, an adjustment on uniform hazard ground motion was proposed to develop new seismic design maps. Thus, risk-targeted ground motion with 1% probability collapse in 50 years is adopted on ASCE 7-10. Even though these seismic design maps are developed for buildings, performance-based bridge design is done using same maps. Because significance difference lies on design procedure of buildings and bridges this thesis suggests some adjustment should be made on uncertainty in the collapse capacity(β) when using for bridge design. This research is done in 3 cities of U.S— San Francisco, New Madrid and New York. Hazard curve is drawn using 2008 version of USGS hazard maps and risk- targeted ground motion is calculated using equation given by Luco et al adjusting the uncertainty in collapse capacity(β) to be 0.9 for bridge design instead of 0.8 as used for buildings. The result is compared with existing result from ASCE 7-10, which uses β=0.6. The sample design response spectrum for site classes A, B, C and D is computed for all 3 cities using equations given in ASCE 7-10 for all β. The design response spectrum curves are analyzed to concluded that adjustment on uncertainty in collapse capacity should be done on ASCE 7-10 seismic design maps to be used for performance-based bridge design.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2007.
Includes bibliographical references (p. 73-74).
The West Gate Bridge, intended to span the Yarra River in Australia, collapsed during its third year of construction in 1970. Investigation into the project revealed numerous issues in the bridge's design and construction. The West Gate Bridge is one of a number of box girder bridges built during the mid 20th century, and was one of four to fail in a three year period. An overview of the design and erection issues is presented, particularly those dealing with thin elements in compression. A comparison of moments and stresses resulting from the use of concrete blocks and jacks to reduce the camber difference encountered on span 10-11 shows that the latter method would have been preferable. The failure of three other box girder bridges between 1969 and 1971, and the required strengthening of dozens of others, reveal the lack of understanding of the slender compressive elements present in such structures. A brief literature review presents the buckling and deformation modes found in stiffened plates under compressive loading, showing the development of understanding of these systems from papers written or published in 1997, 2001, 2004 and 2006 - over three decades after the West Gate collapse.
(cont.) Criteria by AASHTO and by B. H. Choi and C. H. Yoo for the minimum moment of inertia of longitudinal and transverse stiffeners of box girders are presented. The resulting values are compared to the moment of inertia of sections used to strengthen the West Gate Bridge after the collapse of a similar bridge. This comparison shows that the requirements are quite sensitive to scale and can provide inconsistent requirements for stiffness. Thus, there is currently a lack of guidance and regulation from codes for the design of wider single-cell box girders. The complex and non-linear nature of the slender elements in compression used in box girders does not allow the extrapolation of simpler rules developed for the design of smaller bridges. Despite the complex behavior of box girders, they offer a number of advantages and further research is needed to improve their analysis, design, construction, repair and maintenance.
by Alia Christine Burton.
M.Eng.

This research examines the effect of plan irregularities on the progressive collapse of steel structures. Firstly, 2, 3 and 5-storey steel structures, regular and irregular, located in regions with different seismic activity designed in accordance with AISC (20 I 0) and ASCE7 (20 I 0). Secondly, the effect of the four plan irregularities on the progressive collapse of braced and unbraced steel structures located in regions with different seismic activity assessed. The collapse patterns of the I4 buildings is analysed and compared under seven loading scenarios using nonlinear dynamic and static analyses. In the nonlinear dynamic analyses, node displacements above the removed columns and the additional force on the columns adjacent to them are discussed. Furthermore, the capacity of the columns is compared to determine their susceptibility to collapse. ln the nonlinear static analyses, the pushdown curve and yield load factor of the structures are obtained after column removal. The results indicate that an irregular structure designed in site class C seismic zone collapses in most of the column removal scenarios. Moreover, when comparing regular and irregular structures designed in site class E seismic zone, the demand force to capacity ratio (D/C) of the columns in the irregular structures is on average between I.5 and 2 times that of the regular ones has been discussed by Homaioon Ebrahimi et.al (20 I7). The lack of 2-storey building bearing capacity to withstand the removal of the column is lower than that of the 5-storey structure, which is due to the level of redundancy that characterises in the 5-storey structure.

This doctoral thesis presents a structural analysis of the Paderno d’Adda Bridge, an impressive iron arch viaduct built in 1889 and located in Lombardia region (Italy). The thesis falls in the context of a research activity started at University of Bergamo since 2005, that is still ongoing and aims to perform an evaluation of the present state of conservation of the bridge. In fact, the bridge is currently still in service and its important position in the context of transport network will soon lead to questions about its future destination, with particular attention to the evaluation of the residual performance capacity. To this end, an inelastic structural analysis of the Paderno d’Adda bridge has been performed, up to failure. This analysis has been conducted through an autonomous computer code of a 3D frame structure that runs in the MATLAB environment and has been developed within the classical frame of Limit Analysis and Theory of Plasticity. The algorithm has been developed applying the “exact” and stepwise holonomic step-by-step analysis method. It has shown very much able to track the limit structural behaviour of the bridge, by reaching convergence with smooth runs up to the true limit load and corresponding collapse displacements. The main characteristic ingredients of its elastoplastic FEM formulation are: beam finite elements; perfectly plastic joints (as an extension of classical plastic hinges); piece-wise linear yield domains; “exact” time integration. In the algorithm, the following original features have been implemented: treatment of mutual connections by static condensation and Gaussian elimination; determination of the tangent stiffness formulation through Gaussian elimination. These peculiar contributions are presented in detail in this thesis.

碩士
國立成功大學
土木工程學系碩博士班
97
Numerous accidents of bridge collapses occurred during the past decade, The security problems of old bridge have arisen to compatriots and engineering after the Hou-Fong Bridge accident occurred. Nowadays bridge scour induced by heavy rain and typhoon becomes the most important key-factor for the safety of cross-river bridges in Taiwan. If the external force is larger than the bearing capacity of the bridge, the piers will be easily inclined and unstable, even lead to the bridge deck being caved. Fault Tree Analysis (FTA), a widely recognized technique for industry safety, can effectively evaluate cause-and-effect relationship and accident probability. However, the major restriction for using FTA is that it’s difficult to accurately assess accident probability when historical data are insufficient and factors such as human error are vague in nature. On the other hand, Fuzzy Sets (FS) can be used to cope with this problem. In addition, because Analytic Hierarchy Process (AHP) is a commonly used approach to analyze relative importance (frequency) of each paired factor, this paper proposes an analytical model integrated with FTA, FS and AHP to assess accident probabilities. A case study of assessing overall Concrete Bridge Collapses in Taiwan is performed to illustrate the potential aptness of this model. By understanding the features of river flow and river scour influence toward piers, we wish the study to be the reference to improve the river scour problems, which could lead to bridge collapse.

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%.

碩士
國立中央大學
營建管理研究所
99
Taiwan is located in the Pacific earthquake ring of fire and on the path of typhoons occurring in summer seasons; therefore bridges are frequently damaged by earthquakes, scouring, or debris that result in interruption of traffic or even casualties. Currently, evaluation of bridge safety is performed by professional engineers collecting data and evaluating at the bridge sites; which requires huge amount of manpower and costs. 　　This research investigates the major factors which have significant impacts on bridge collapse by literature reviews and expert interviews. These factors are then weighted by the Analytical Hierarchical Process (AHP) method to establish a preliminary evaluation mechanism for bridge collapse due to earthquake, scouring, and debris. The established mechanism reveals similar performance with satisfactory results when tested against on site evaluations of 20 bridges. 　　This research also establishes a fast evaluation process to apply the established mechanism to the Taiwan Bridge Management System (T-BMS) to screen out the most dangerous bridges which have relatively high potential to collapse. These bridges should have higher priority to install prewarning monitoring systems and should obtain more attentions from the bridge management agencies. Results of this research should be beneficial to the tasks related to evaluations of bridge collapse and bridge safety.

碩士
國立臺灣科技大學
營建工程系
93
Abstract After bridge collapse, a proper temporary bridge for reducing additional social cost and delays of rescue is needed with emergency to assist rescuer to enter the disaster area. Usually, the temporary bridge method is decided by engineer with experience, and the influence of duration on social cost and relief time is ignored. Therefore, this study considers time effect of rescue and economical phase to create the Economic Evaluation of Temporary Bridge Methods and Alternate Routes.

碩士
國立中央大學
土木工程學系
101
When the bridge failure events come, vehicles on the bridge may not get good vision or can’t exactly know the health of bridge forwardly, it is possible that people and vehicles will get great damage. The subject of study is to develop a reliable, low maintenance, cheap and effective warning system of bridge collapse, without the monitoring data and complicated theory, only judge from whether the event of bridge collapse happened or not, when it did, the warning system can exactly warn the people on the bridge to avoid the unnecessary damage. There are Water-Source and Circuit warning system respectively, the former uses the controller of water level in the water tank as detecting component, the water pipe connect the tank to the gap between the beams, when the beams have relative displacement, the cutting device which installs on lateral of beams will cut the pipe and make the water level descend, then the controller works to trigger the alarm, the latter uses the electric wire and relay as detecting component, then install and fix the wire at bridge unit like beams or piers, when it’s a large displacement between beams or piers, the wire breaks because of the pulling force, by the characteristic of relay, when the wire breaks, relay’s interior system will trigger the warning system. This paper has also take advantage of the evaluation table of scouring potential of bridge foundation from Ministry of Transportation and Communications, combining AHP and constructing the structure of hierarchy, regarding the feedback of expert questionaries, then get the weight of evaluation index in the hierarchy, so we can evaluate the scouring potential for the bridge and estimate whether the bridge installs the warning system or not.

碩士
國立成功大學
水利及海洋工程學系碩士在職專班
102
Lin-bian River bridge railway was built in 1941 and began to operate in the same year. During Typhoon Morakot, piers P11, P12 and three girders of the bridge were damaged by the flood on Aug 8, 2009, before the embankment broke. Typhoon Morakot produced copious amounts of rainfall, 15 rainfall records reached 2,000mm in 72 hours and the average rainfall of four gauge stations within the Linbian River Watershed reached 1,583mm in two days. The peak discharge of the river achieved 5,466 cms. Jointly with the geological characteristics of Taiwan, the enormous rainfall amount brought by typhoon easily resulted in the landslide and debris flow in Taiwan. In addition, the land subsidence in Pington during 1972 to 2004 was severe (3.22m at maximum) and it caused the elevation level of bridge 2.3 m only. The low height makes the bridge to accumulate drift wood easily and increases the water-blocking cross section, which threatens the safety of bridge. In this study, the data of hydrology, river landform, bridge structure and debris wood amount, was analyzed by HEC-RAS model computation. Moreover, the sampling and testing of the concrete was conducted as well as the rebound Hammer Test in order to obtain the stress intensity of pier material. The outcome showed that drift wood was the most critical factor to damage bridge due to its blocking water effects that generates additional torque and shear stress.

The collapse of the I-35W Bridge in Minneapolis, MN on August 1, 2007 brought into question the design and inspection of gusset plates in steel truss bridges. The experimental tests performed in this research study the sway-buckling strength and behavior of large-scale steel gusset plates in an isolated truss connection. Parameters studied include plate thickness,combination member loading, initial out-of-plane imperfection, diagonal compression member out-of-plane flexural stiffness, corrosion, and alternative retrofits to increase lateral stiffness. The flexural stiffness of the diagonal compression member and retrofit designs were unique to the testing program. The variables monitored during testing include gusset plate surface stresses and strains, member axial strains, out-of-plane displacement of the gusset plate free edge, and buckling capacity. The results were compared with previously established design models for predicting buckling capacity of gusset plates which include the Whitmore effective width, the Modified-Thornton method, and the FHWA Load Rating Guidelines. A parametric finite element model was developed to determine the lateral stiffness of the gusset plate connection and the additional stiffness provided by the alternative retrofit options. The results showed interaction between the diagonal compression member and gusset plate occurs, which affects sway-buckling capacity. Combination of member loads showed evidence of detrimental effects on sway-buckling capacity. Corrosion of the gusset plates along the top edge of the bottom chord did not lead to significant reduction in sway-buckling capacity. The two retrofit designs showed increases in both lateral stiffness and buckling capacity as well as economic benefits over traditional retrofit methods. Comparison of the results to the current design guidelines showed that the current methods are conservative and do not accurately represent the true behavior of gusset plate connections. The research concludes with two proposed models for future use in design and retrofit of gusset plates. The first is a member-gusset plate interaction model based on a stepped column analogy that takes into account the effects of member flexural stiffness and gusset plate stiffness. The second is a general design guideline developed for retrofit of gusset plate connections dominated by sway-buckling behavior which uses a stiffness based approach to increase the capacity of gusset plate connections.
Graduation date: 2012

碩士
國立臺北教育大學
自然科學教育學系碩士班
98
This study was to explore the effectiveness of a project-based teaching strategy on students’ learning motivation, attitude and ability levels towards scientific inquiry. The researcher, a teacher in Miaoli, Taiwan taught a sixth grade class of 13 boys and 11 girls in primary school. The teacher implemented the project-based learning course with a socio-scientific driven question, “Could the Hou-Fong bridge not collapse?” for 12-week. The project consisted of two parts, (1)courses for the improvement of students’ inquiry ability, and (2)doing scientific inquiring project activities. Both parts were complementary during the instruction. The study, through mixed-method, collected data comprising (1)quantitative instruments including the stages of learning motivation, attitude and ability towards science inquiry which were used for pretest and posttest to examine the inquiry elevated by t-test and (2)qualitative data including video recording of the instruction, interviews, teacher self-report, and the final projects made by students. The results showed that: (1) The building of scaffoldings before and during the instruction helped increase the students’ understanding of scientific inquiry, (2) Students’ learning motivation and attitude were enhanced through practices, (3)This instruction not only cultivated the inquiry ability of project-based activities for the students, but also made the teacher to better understand how to use the scaffoldings as inquiry instruction. The study inspired the module to construct scaffolding project-based instruction for science educators.

Tese de doutoramento em Engenharia Civil (Estruturas) apresentada à Fac. de Ciências e Tecnologia da Univ. de Coimbra
O método dos elementos discretos baseado em elementos discretos poligonais, inicialmente aplicado ao estudo de maciços rochosos, depressa se adaptou e generalizou a outros estudos, como o das estruturas em alvenaria de edifícios e pontes históricas. Este método é particularmente apropriado à representação de estruturas de carácter predominantemente discreto com elementos discretos poligonais, dispensando, contrariamente ao método dos elementos finitos, a modelação das juntas com outro tipo de elemento. Entre as principais características do método encontra-se a possibilidade dos elementos discretos efectuarem deslocamentos e rotações finitos, separarem-se uns dos outros e estabelecerem novos contactos. As formulações existentes do método dos elementos discretos contemplam modelos constituídos por elementos discretos poligonais, rígidos ou deformáveis, ou por elementos discretos circulares rígidos, quer em 2D quer em 3D. No sentido de alargar a aplicação deste método foi desenvolvido neste trabalho um modelo plano misto de elementos discretos rígidos que associa o elemento discreto poligonal e o elemento discreto circular. Deste modo, é possível efectuar estudos 2D de pontes em arco de alvenaria, simulando o arco e os muros de tímpano com elementos discretos poligonais e o material de enchimento do arco com elementos discretos circulares. Este modelo segue os requisitos clássicos do método dos elementos discretos mas introduz alguns aspectos novos, nomeadamente, a definição de novos tipos de contacto, a adequação do método de detecção de novos contactos, a geração da malha de elementos discretos circulares localizados entre o extradorso do arco e a cota do pavimento, entre outros. O modelo plano desenvolvido permite também a determinação de valores e vectores próprios do sistema constituído pela estrutura e enchimento, sendo os primeiros relevantes para a sua calibração. A aplicação do método misto dos elementos discretos à análise quase estática de estruturas está especialmente vocacionada para o cálculo da carga de colapso, e respectivo modo de colapso, de pontes em arco de alvenaria, sendo apresentado o exemplo de uma aplicação deste tipo.
The discrete element method applied to a system of polygonal discrete elements, originally employed in the study of jointed rock masses, was quickly adapted and generalized to other studies, such as the structural behaviour of historical masonry bridges and other buildings. This method is particularly appropriated to the representation with polygonal discrete elements of structures whose character is predominantly discrete, without the need to specifically contemplate the joint with any type of element, as it is required in the finite element method. One of the main characteristics of the method is the possibility of each discrete element to undergo finite displacements and rotations, disconnect from another one and establish new contacts. The existent formulations of the discrete element method consider models constituted by polygonal discrete elements, rigid or deformable, or by rigid circular discrete elements, either in 2D or in 3D. In order to enlarge the domain of application of this method a rigid mixed plane model of discrete elements was developed in the present work, including both the polygonal and the circular discrete elements. This makes it possible to accomplish 2D studies of masonry arch bridges, modelling the arch and the spandrel walls with polygonal discrete elements and the fill of the arch with circular discrete elements. This model follows the classic requirements of the discrete element method, but required the introduction of some new features, namely, the definition of new types of contact, the adaptation of the detection method to these new types of contact, the generation of the mesh of circular discrete elements between the extrados of the arch and the road surface, among others. The developed 2D algorithm allows the determination of the eigenvalues and eigenvectors of the system structure plus fill, which are very useful to calibrate the numerical model. The application of the mixed discrete element method to the quasi-static analysis of structures is specially indicated for the calculation of the bearing capacity, and respective collapse mode, of masonry arch bridges, and an example of this type is presented.