Bridges In Transportation Networks Research Articles

A risk-based quantitative approach for priority assessment of ageing bridges accounting for deterioration

The significant role of bridges in transportation networks requires continuous improvement of bridge management strategies, which has been even more exacerbated by the recent bridge collapses worldwide. This study proposes a framework for the prioritization and preliminary risk assessment of existing bridges subjected to seismic and traffic hazards. The proposed method adopts quantitative expressions to define risk in a simplified manner and, consequently, the priority associated with a certain bridge within a bridge stock. The three primary components of risk are considered: vulnerability, exposure, and hazard, which are specified according to the characteristics of the bridge, site, and road network. The bridge state of conservation is accounted for in the vulnerability component through average and critical defect condition indicators. The proposed method is implemented in a case-study of thirty real bridges in northern Italy. The impact of defects on vulnerability and priority ranking of bridges, the assumptions for defects condition and each subcomponent’s contribution to risk classification are discussed. The prioritization results are presented in absolute and normalized formats, with the latter providing a clearer view of the bridges’ relative priority within the stock. Finally, the proposed method’s findings are compared with the current Italian qualitative guidelines for bridge management.

Non-parametric stochastic subset optimization for reliability-based importance ranking of bridges in transportation networks

• Proposes a non-parametric stochastic subset optimization algorithm for reliability-based importance ranking of bridges. • Proposes iterative approach with adaptive stochastic sampling to improve efficiency of algorithm. • Number of iterations only grows logarithmically with respect to the total number of bridges in the transportation network. • Algorithm is highly efficient and especially useful for large-scale networks with many bridges. Establishing reliability-based importance ranking of bridges in a transportation network usually entails significant computational efforts, especially for large-scale networks. This paper proposes a non-parametric stochastic subset optimization (NP-SSO) algorithm to efficiently identify the reliability-based importance ranking of bridges. It first generates failure samples from an augmented failure distribution and then directly establishes the importance ranking by comparing the number of failure samples for each bridge. To improve the efficiency, an iterative NP-SSO algorithm is established by restricting the search space to the subset of bridges identified in the previous iteration. For each iteration, the modified accept-reject algorithm with adaptive kernel sampling density (AKSD) is adopted to efficiently generate failure samples. The proposed NP-SSO algorithm is highly efficient for identification of important bridges, and the number of iterations only grows logarithmically with respect to the number of bridges, and NP-SSO is especially useful for large-scale networks with many bridges. The effectiveness and efficiency of NP-SSO are demonstrated through identifying the importance ranking of bridges in the transportation network of Los Angeles and Orange counties.

A new model for bridge management: Part A: condition assessment and priority ranking of bridges

Due to substantial role of bridges in transportation networks and in accordance with the limited funding for bridge management, remediation strategies have to be prioritised. A conservative bridge assessment will result in unnecessary actions, such as costly bridge strengthening or repairs. On the other hand, any bridge maintenance negligence and delayed actions may lead to heavy future costs or degraded assets. The accuracy of decisions developed by any manager or bridge engineer relies on the accuracy of the bridge condition assessment which emanates from visual inspection. Most of the bridge ranking systems are commonly based on structural condition. Parameters such as functionality and client preferences are used in an isolated fashion. The developing prioritisation method described herein is an important step in adding more holism and objectivity to the current approaches. To achieve this goal, all important parameters have been identified, weighted and finally synthesised in an index introduced as Priority Index (PI). PI is expressed as a number which enables the decision-makers to simply understand and compare the overall condition of a variety of bridges in the network. It embraces three factors: structural efficiency, functional efficiency and client impact factor. The proposed model was tested through case studies and qualified experts (senior bridge inspectors, engineers and asset managers) from about 30 private and public transportation authorities.

Influence of scour effects on the seismic response of reinforced concrete bridges

Flood-induced scour is a common phenomenon that causes the loss of lateral support at bridge foundations. However, the impact of scour is usually ignored when assessing the anticipated response of bridges under earthquake loads. This study quantifies the effect of scour on the dynamic behavior and seismic performance of reinforced concrete (RC) bridges. Additionally, this study investigates potential structural design alternatives to mitigate damage from earthquake exposure given scour conditions. Since the structural periods corresponding to the first few vibration modes increase with the increase of scour depth, this study finds that the sensitivity of the periods to the scour depth varies for different types of bridges. Also, bridge variety determines whether scour has a beneficial or detrimental effect on the seismic column fragility. In addition, scour may amplify the potential seismic damage of the bridge via transferring damage from the column to the pile foundations, or increasing the probability of deck unseating. Regarding strategies to manage detrimental scour effects, this study finds that increasing the foundation stiffness is effective for reducing the seismic damage of scoured bridges, while increasing the foundation depth only has a minor effect. Also, the foundation type has great impact on the seismic performance of scoured bridges. The findings of this study can be used to guide the seismic design of new bridges or the retrofit of existing bridges in transportation networks along flood-prone regions.

Rapid identification of properties of column-supported bridge-type structure by using vibratory response

Some engineering structures, such as bridges in transportation network, may be subject to unexpected hazardous events, which calls for the rapid identification of their structural properties using portable hardware and data analysis system to evaluate their remaining load-carrying capacity. A significant challenge in such mission is the lack of baseline information of the structure to be evaluated. In this research, we formulate a vibration-based methodology using modal testing to identify properties of column-supported bridge-type structure. An assumed-mode based discretization is adopted to establish an equivalent nominal model that is a function of the unknown structural properties. The system identification algorithm is built upon the mass response method, i.e., introducing a known added mass to the structure and measuring respectively the modal information before and after this mass is added. This approach enables the structural identification without a priori information of the mass. Systematic case studies are then carried out to evaluate the effectiveness of this methodology. It is found that the new algorithm formulated can yield very accurate and robust identification results.

A Methodology for Bridge Condition Evaluation

Due to the substantial role of bridges in transportation networks and in accordance with the limited funding for bridge management, remediation strategies have to be prioritised. A conservative bridge assessment will result in unnecessary actions, such as costly bridge strengthening or repairs. On the other hand, any bridge maintenance negligence and delayed actions may lead to heavy future costs or degraded assets. The accuracy of decisions developed by any manager or bridge engineer relies on the accuracy of the bridge condition assessment which emanates from visual inspection. Many bridge rating systems are based on a very subjective procedure and are associated with uncertainty and personal bias. The developing condition rating method described herein is an important step in adding more holism and objectivity to the current approaches. Structural importance and material vulnerability are the two main factors that should be considered in the evaluation of element structural index and the causal factor as the representative of age, environment, road class and inspection is implemented as a coefficient to the OSCI (overall structural condition index). The AHP (analytical hierarchy process) has been applied to evaluate the priority vector of the causal parame