Construction of infrastructures in cold regions and the Arctic has grown rapidly since the 2000s, including railways, platforms, bridges, roads, and pipelines. However, the harsh low temperatures significantly influence the mechanical behaviors of construction materials, and bring safety and durability challenges to these engineering structures. This study made a state-of-the-art review on materials and structures exposed to low temperatures. This review started from constructional-material mechanical properties, including concrete, steel reinforcement, mild/high-strength steel plate, and steel strand at low temperatures. It reflected that low temperatures improved the strength of construction materials. However, the freeze–thaw cycles (FTCs) had a detrimental effect on the modulus and strength of concrete. Furthermore, it was revealed that low temperatures increased the interfacial bonding strength between the steel reinforcements (or shear connectors) and concrete. Moreover, low temperatures improved the bending, shear, and compression resistances of reinforced concrete (RC) or prestressed concrete structures, but reduced the ductility of RC columns under lateral cyclic loads. Finally, reviews also found that low temperatures improved the compression resistance of concrete-filled steel tubes using mild, high-strength, and stainless steels, whereas FTCs and erosion reduced their compression capacity. In addition, low temperatures increased the bending resistance of steel–concrete composite structures, but the FTCs reduced it. The low temperatures bring challenges to the safety and resilience of engincering constructions, which requires careful further studies. Continuous further studies may focus on the durability of materials and the resilience of structures under diverse hazards, including earthquakes, impacts, and even blasts.
Sequential seismic events occur worldwide,which impose significant threats to the safety and serviceability of Civil infrastructure, especially buildings and bridges. Fragility functions are imperative to support decision-making tools for potential seismic risk identification and its impact on str uctural performance during sequential carthquakes. The increasing number of publications shows a notable increase in interest among rescarchers and the scien tific community in this domain. This study presents a systema eview of available resources and techniques for structural performance and fragility evaluation subjected to mainshock-aftershock seismic loading. Efforts have been made to focus on the salient features of various approaches rather than criticizing the mathematical frameworks and associated analysis approaches. Existing knowledge related to the effect of sequential seismic loading on buildings and bridge infrastructures and their fragility estimates is presented concisely. The paper concludes by detailing the opportunities for future developments in the fragility analysis of Civil infrastructure under sequential seismic hazard. This would encourage stakeholders and decision-makers to put into practice their applications for risk mitigation, recovery planning, and well-informed decision-making.
Bamboo materials are known for their excellent toughness and seismic performance, which makes them a promising option for advancing their application in the field of structural engineering to enhance the seismic resilience of engineering structures. This study focused on mechanical behavior of bolted steel-neosinocalamus affinis-based bamboo scrimber and steel connections, and conducted shear test research and analysis on 54 specimens divided into 18 groups,aiming to promote the application of bamboo scrimber in the field of structural engineering. The study indicates that connections with thin steel plates (t = 0.5d, t=Id) predominantly exhibit a single-hinge yield mode, while those with thick steel plates (t=2d) are inclined towards a double-hinged yield mode. The yield and ultimate load-carrying capacities of a connection are enhanced with the increase in bolt diameter. However, the influence of the steel plate’s strength grade on these capacities is minimal. The yield load-carrying capacity of connections with thick steel plates has a significant increase compared with the connection with thin steel plates. The thickness of the steel plate does not significantly affect the connection ultimate load-carrying capacity. The initial stiffness of a connection is positively correlated with the bolt diameter, yet it remains unaffected by variations in the steel plate’s thickness. The stiffness of a connection is categorized into two distinct types based on the steel plate strength grade. Connections using steel plates with a strength grade above Q235 exhibit similar stiffness levels, which are consistently higher than those using Q235-grade steel plates. The angle between the load direction and the grain direction has an effect on the connection ductility. The ductility coefficient across various connections predominantly centers around 2.5. The research also validates that the Foschi theoretical model, traditionally applied to wood structures with bolted, nailed, and similar dowel-type connections, accurately delineates the nonlinear load-displacement behavior of bolted steel-bamboo scrimber and steel connections for the entire duration of the process. When comparing the same configurations, connections utilizing neosinocalamus affinis-based bamboo scrimber demonstrate a higher load-carrying capacity than those using phyllostachys pubescens-based bamboo scrimber, with a maximum enhancement in load-carrying capacity of 18%. The design carrying capacity meets the test load requirements for the given end distances of 7d. This research can provide theoretical support for the engineering application of neosinocalamus affinis-based bamboo scrimber.
The shortcomings of segmentally assembled round-end hollow-section piers (SRHPs), such as weak segment joints and poor energy-dissipation capacity, have limited their application in high-intensity carthquake regions. Therefore, this article particularly focuses on the seismic performance of SRHPs. Three high-speed railway bridges are designed, which are equipped with three different types of round-end hollow-section piers (RHPs): cast-in situ RHP (CRHP), segmentally assembled RHP with energy-dissipation bar (E-SRHP), and segmentally assembled RHP with low-yield point steel connection buckles (L-SRHP). Subsequently, three nonlinear finite element models of the corresponding bridges were established and validated by quasi-static test results. Furthermore, compared to CRHP, the seismic performance of E-SRHP and L-SRHP was evaluated from the perspectives of seismic fragility and life-cycle seismic loss. Research results revealed that the seismic fragility performance of the bridge with L-SRHP is the best among all three bridges, followed by the bridge with E-SRHP. Notably, the life-cycle cost considering seismic loss for E-SRHP is 83% of that for CRHP, whereas L-SRHP is only 65% of that for CRHP. In general, the high-speed railway bridge supported by L-SRHP possesses the best seismic performance and economic benefits among the three bridges, which shows promising application prospects in high-intensity earthquake-prone regions.
Nonstructural components (NSCs) contribute about 80%–90% of the construction investment in a modern public building. The post-earthquake safety and normal operation of NSCs are necessary to achieve performance-based design and resilient buildings. The piping system is one of the most essential nonstructural systems to preserve the post-earthquake functionality of public buildings.To accurately evaluate the seismic performance and vulnerability of piping systems in buildings, a component-level seismic fragility database is urgently to be developed. System composition, failure modes of piping systems, and induced consequences during previous earthquakes are introduced first in this article Then a concise description of component-level fragility methodology suggested by the Applied Technology Council is presented. Seismic fragility database of piping components including pipes, piping joints, and seismic braces through quasistatic tests are developed based on the fragility analysis method. Experimental results from available literature are summarized and presented in the form of seismic fragility curves. Specifc hysteretic curves of these components are also presented, which are used for the calibration of numerical models. In addition the future research directions on the seismic fragility of piping components are summarized and prospected. The developed component-level seismic fragility database can be used to help understand the seismic performance and post-earthquake damage states of the piping system. Seismic performance assessment and seismic fragility analysis of modern piping systems can be conducted using the developed database and numerical simulation method.
Grain plays a crucial role in a nation’s economic security and public welfare, and the efficient storage of grain in group silos is essential for maintaining these reserves. As a global leader in grain production, consumption, and imports, China also holds a significant position in grain reserves. Based on shake table tests and actual case studies, this study explores the seismic mechanisms and failure modes of column-supported group silos using the Abaqus finite element simulation method.This study includes shaking table test verification and a refined numerical simulation method for column-supported silos. The dynamic responses, natural frequency, acceleration, and lateral pressure of storage material are analyzed to verify the rationality of numerical methods. Additionally, this study investigates the implementation and mechanisms of the material-structure interaction system in Abaqus, including the selection of material constitutive models, earthquake records, element size division, and grain-structure contact issues. Then, finite element models of different silo structures are built for single silos, row silos, and group silos. The modal shapes, natural frequencies, acceleration responses, relative displacement responses, and lateral pressure of storage material under the action of EL-Centro waves, Kobe waves, and artificial waves are investigated to reveal the seismic response mechanisms of column-supported silo structures under different storage material conditions. This research not only helps guide practical engineering design but also provides a scientific supplement to existing silo seismic theories.
Since the Fukushima nuclear incident in 2011, the focus on nuclear safety has intensified significantly, leading to heightened demands for nuclear power plant modeling to go beyond the mere dynamic analysis of soil–structure interaction (SSI) or fluid–structure interaction (FSI). In current engineering practice, FSI is typically described using simplified forms, such as loads or added mass. However, this approach lacks a comprehensive analytical framework that integrates refined FSI analysis with soil–structure interaction (SSI). This study analyzes the dynamic response of the nuclear island structural system using a fully coupled fluid–structure–soil interaction (FSSI) model. The effectiveness and validity of the model are verified through case comparisons. Simulations were conducted using the parameters of five different types of nuclear power engineering sites for both homogeneous and layered foundations. The results indicated that the hydrodynamic pressure response and acceleration amplification of layered foundations significantly exceeded those of homogeneous foundations, underscoring the importance of considering layered sites in the comprehensive complex modeling of nuclear power projects.
The safety of an isolated structure built on the soft soil ground under the action of carthquakes is of major concern because the current seismic design of isolated structures has not considered the motions of the foundations caused by the effects of the soil-isolated structure dynamic interaction (SISI). On this basis, a shaking-table test method for base-isolated structures on change of soil foundation stiffness was proposed and implemented. The foundation stiffness was controlled by the duration compression ratio and intensity of the input ground motion based on the influence of the increase in the excess pore water pressure ratio on the stifiness of the saturated sandy foundation. Meanwhile, the influence laws of foundation stiffness on the dynamic characteristics of base-isolated structures were summarized and analyzed. The results showed that the first-order natural frequency of base-isolated structures on change of foundation stiffness decreased with an increase in the relative stiffness ratio of the structure-soil foundation (RS), while its damping ratio increased significantly. The seismic isolation efficiency of the seismic isolation layer and the amplification effect on the rotational angular acceleration of the pile cap were significantly weakened. Meanwhile, under the same conditions, for the soil foundation with relatively small stiffness, the amplitudes of the bending moment and horizontal lateral displacement in the middle and upper parts of the pile remarkably increase because of the efects of the ISI. The research results of this test provide a certain scientific basis and reference for the seismic design of base-isolated structures considering the SISI effects.
Isolation bearings play an important role in the seismic resilience of highway bridges. Flexible and high-strength reinforcement has been applied in elastomeric isolation bearings to substitute conventional rigid steel plate reinforcement to enhance their lateral performance, for example, Iower lateral stiffness and larger deformability. However, the main literature shows that existing flexible reinforcement, such as carbon/glass fiber fabric, may not guarantee a sufficient vertical load-carrying capacity of elastomeric bearings to meet the design requirement of 30 MPa considering the vertical seismic effect. To this end, the emerging high-strength steel woven wire mesh was introduced as an alternative flexible reinforcement for the bearings in this study to increase their ultimate compression capacity while maintaining superior lateral performance. Vertical compression tests were conducted on 34 specimens of the proposed unbonded steel-mesh-reinforced bearings (USRBs) to investigate the ultimate compression capacity. In addition to the general ultimate behavior of USRBs under vertical loading, the influence of various design parameters (i.e., individual rubber layer thickness, number of reinforcement layers, bearing design load) was investigated through comparisons among the specimens. From the test results, the compressive failure mechanism of USRBs was unveiled, which originated from the tensile failure of the steel mesh reinforcement. The steel mesh reinforcement was proved to increase the bearing ultimate compression capacity to an average of 52.0 MPa compared to fiber-reinforced bearings, with 85% of specimens exceeding 30 MPa. Moreover, the compression capacity of USRBs was identified to be significantly affected by the individual rubber layer thickness. Specific discussions were further provided concerning the influence of potential manufacturing defects. Finally, suggestions were provided to further enhance the ultimate compression capacity of USRBs based on the results and discussions.
This paper presents two physics-based, orientation-independent intensity measures that truly captures the three-dimensional motion of an orthogonal array of accelerometers and are more appropriate for seismic structural design. This is achieved by processing all three components of the record simultaneously, rather than simply combining the results of processing each component in isolation. Compared to other commonly accepted orientation-independent intensity measures, it was found that horizontal seismic demand may be systematically underestimated by as much as 29% in the worst-case scenario. In addition, these new measures are much more computationally efficient than the current ones, as they reduce the number of response spectra calculations per seismic record to just 2 or 3, depending on the measure. Thus, the orientation-independent intensity measures introduced here optimize the processing of seismic records and may help to reduce the uncertainty of the estimation of the seismic acceleration for structural design.