Cost-based resilience assessment of bridges subjected to earthquakes

European Commission H2020-Marie Skłodowska-Curie Research Grants Scheme MSCA-IF-2016 (grant agreement No 746298: TRANSRISK – Vulnerability and risk assessment of transportation systems of assets exposed to geo-hazards)

Conflict-resilience framework for critical infrastructure peacebuilding

Apart from security issues, war-torn societies and countries face immense challenges in rebuilding damaged critical infrastructure. Existing post-conflict recovery frameworks mainly focus on social impacts and mitigation. Also, existing frameworks for resilience to natural hazards are mainly based on design and intervention, yet, they are not fit for post-conflict infrastructure recovery for a number of reasons explained in this paper. Post-conflict peacebuilding can be enhanced when resilience by assessment (RBA) is employed, using standoff observations that include data from disparate remote-sensing sources, e.g. public satellite imagery, forensics and crowdsourcing, collected during the conflict. This paper discusses why conflicts and warfare require a new framework for achieving post-conflict infrastructure resilience. It then introduces a novel post-conflict framework that includes different scales of resilience with a focus on asset and regional resilience. It considers different levels of knowledge, with a focus on standoff observations and data-driven assessments to facilitate prioritisation during reconstruction. The framework is then applied to the transport network of the area west of Kyiv, Ukraine to demonstrate how resilience by assessment can support decision-makers, such as governments and multilateral financial institutions, to address infrastructure needs and accelerate financial and humanitarian assistance, absorb shocks and maximise infrastructure recovery after conflict

Innovations in earthquake risk reduction for resilience: Recent advances and challenges

The Sendai Framework for Disaster Risk Reduction 2015-2030 (SFDRR) highlights the importance of scientific research, supporting the ‘availability and application of science and technology to decision making’ in disaster risk reduction (DRR). Science and technology can play a crucial role in the world’s ability to reduce casualties, physical damage, and interruption to critical infrastructure due to natural hazards and their complex interactions. The SFDRR encourages better access to technological innovations combined with increased DRR investments in developing cost-effective approaches and tackling global challenges. To this aim, it is essential to link multi- and interdisciplinary research and technological innovations with policy and engineering/DRR practice. To share knowledge and promote discussion on recent advances, challenges, and future directions on ‘Innovations in Earthquake Risk Reduction for Resilience’, a group of experts from academia and industry met in London, UK, in July 2019. The workshop focused on both cutting-edge ‘soft’ (e.g., novel modelling methods/frameworks, early warning systems, disaster financing and parametric insurance) and ‘hard’ (e.g., novel structural systems/devices for new structures and retrofitting of existing structures, sensors) risk-reduction strategies for the enhancement of structural and infrastructural earthquake safety and resilience. The workshop highlighted emerging trends and lessons from recent earthquake events and pinpointed critical issues for future research and policy interventions. This paper summarises some of the key aspects identified and discussed during the workshop to inform other researchers worldwide and extend the conversation to a broader audience, with the ultimate aim of driving change in how seismic risk is quantified and mitigated

Bridges with fixities and bearings vs isolated systems

Seismic isolation exhibits a breakthrough in contemporary bridge engineering. The principal of isolation is to protect the bridge piers, by either reducing their seismic actions or through the increase in the damping of the structure. However, there are bridges in which the seismic loading of piers is not effectively reduced when using seismic isolation, and hence the use of expensive and expendable isolators can be avoided. The ineffectiveness of seismic isolation with typical elastomeric bearings was observed in bridges with tall piers. As such the piers can be connected with the deck through rotation-free connections, such as fixed bearings or stoppers, while their seismic loading is not significantly increased. A parametric study is conducted with alternative isolated bridge-models to identify the necessity of piers' isolation against longitudinal seismic actions. Bridge-models with bents of variable heights ranging from 5m to 30m and cross sections ranging from flexible to stiff bent-types were analyzed. All bridge-models were re-analyzed considering that shear keys placed on the piers restrict the longitudinal deck displacements. The adequacy of the piers was checked against longitudinal and transverse seismic actions. The analyses for two levels of the seismic action indicated specific bridge design cases that can utilize both rotation-free pier-to-deck fixities and bearings, while the bridge remains essentially elastic

Uplift of elastomeric bearings in isolated bridges subjected to longitudinal seismic excitations

© 2014 Taylor & Francis Bearings are used to isolate bridge substructures from the lateral forces induced by creep, shrinkage and seismic displacements. They are set in one or two support lines parallel to the transverse axis of the pier cap and are typically anchored to the deck and to the pier cap. This detailing makes them susceptible to possible tensile loading. During an earthquake, the longitudinal displacements of the deck induce rotations to the pier caps about a transverse axis, which in turn cause tensile (uplift) and compressive displacements to the bearings. Tensile displacements of bearings, due to the pier rotations, have not been addressed before and questions about the severity of this uplift effect arise, because tensile loading of bearings is strongly related to elastomer cavitation and ruptures. An extended parametric study revealed that bearing uplift may occur in isolated bridges, while uplift effect is more critical for the bearings on shorter piers. Tensile displacements of bearings were found to be significantly increased when the isolators were eccentrically placed with respect to the axis of the pier and when flexible isolators were used for the isolation of the bridge. The results of this study cannot be generalised as bridge response is strongly case-dependent and the approach has limitations, which are related to the modelling approach and to the fact that emphasis was placed on the longitudinal response of bridges

Seismic design of bridges with the participation of seat-type abutments

Abutments are not only earth-retaining systems as they also participate to the earthquake resisting system (ERS) of the bridge, under certain design considerations. Current research mainly focuses on the assessment of the performance of integral abutment bridges, while only a few studies dealt with the design of bridges with seat-type abutments accounting for their seismic contribution. Along these lines, a comparative study on seat-type abutment bridges was performed. The scope of the study was to identify possible differences in their seismic response affecting significant design parameters that are the displacements of the deck and the bending moments of the piers. The study employed three real bridges of variable total lengths, openings at the expansion joints, backfill models and moderate to strong earthquake excitations. Non-linear dynamic time history analysis was performed. The study showed that the strong participation of the abutment and the backfill soil can reduce effectively the seismic demand of bridges. However, attention should be given in bridges with tall piers, whose seismic forces can be increased under certain design conditions. © 2012 Elsevier Ltd

Seismic design of bridges with the participation of seat-type abutments

Abutments are not only earth-retaining systems as they also participate to the earthquake resisting system (ERS) of the bridge, under certain design considerations. Current research mainly focuses on the assessment of the performance of integral abutment bridges, while only a few studies dealt with the design of bridges with seat-type abutments accounting for their seismic contribution. Along these lines, a comparative study on seat-type abutment bridges was performed. The scope of the study was to identify possible differences in their seismic response affecting significant design parameters that are the displacements of the deck and the bending moments of the piers. The study employed three real bridges of variable total lengths, openings at the expansion joints, backfill models and moderate to strong earthquake excitations. Non-linear dynamic time history analysis was performed. The study showed that the strong participation of the abutment and the backfill soil can reduce effectively the seismic demand of bridges. However, attention should be given in bridges with tall piers, whose seismic forces can be increased under certain design conditions. © 2012 Elsevier Ltd

Uplift of elastomeric bearings in isolated bridges subjected to longitudinal seismic excitations

© 2014 Taylor & Francis Bearings are used to isolate bridge substructures from the lateral forces induced by creep, shrinkage and seismic displacements. They are set in one or two support lines parallel to the transverse axis of the pier cap and are typically anchored to the deck and to the pier cap. This detailing makes them susceptible to possible tensile loading. During an earthquake, the longitudinal displacements of the deck induce rotations to the pier caps about a transverse axis, which in turn cause tensile (uplift) and compressive displacements to the bearings. Tensile displacements of bearings, due to the pier rotations, have not been addressed before and questions about the severity of this uplift effect arise, because tensile loading of bearings is strongly related to elastomer cavitation and ruptures. An extended parametric study revealed that bearing uplift may occur in isolated bridges, while uplift effect is more critical for the bearings on shorter piers. Tensile displacements of bearings were found to be significantly increased when the isolators were eccentrically placed with respect to the axis of the pier and when flexible isolators were used for the isolation of the bridge. The results of this study cannot be generalised as bridge response is strongly case-dependent and the approach has limitations, which are related to the modelling approach and to the fact that emphasis was placed on the longitudinal response of bridges