Earthquakes and extreme waves pose significant threats to the safety of offshore bridges, particularly in deep-water environments. The temporal sequence of earthquakes and waves and the specific type ...of earthquake are critical factors that contribute to the potential risks involved. This study aimed to fill a key knowledge gap by conducting a comprehensive series of physical tests on a deep-water bridge pier at a scale factor of 1:30. White noise tests, shaking table tests, wavemaker tests, and combined shaking table and wavemaker tests were carried out. Near-field pulsed earthquakes, far-field long-period earthquakes and earthquake-wave phase differences were examined in the tests. The test results indicate that the presence of water has a noticeable impact on the natural frequency, particularly the 2nd-order frequency, of bridge piers, which may significantly influence the dynamic responses of high bridge piers. The effects of water–pier interactions are further intensified by seismic actions such as the pulsed Loma Prieta and long-period Chi-Chi earthquakes. Moreover, the earthquake-induced hydrodynamic pressures on the upstream and downstream faces of the pier are nearly identical, whereas there is a notable difference when the pressures are caused by incident waves. The magnitude of the combined earthquake and wave responses in relation to the individual responses is influenced by the earthquake–wave phase differences, and the combined responses are less than the sum of the individual responses.
•Dynamic responses of bridge piers to earthquakes and waves are investigated and carried out through joint tests.•Phase differences between earthquakes and waves are emphasized, and pulsed and long-period earthquakes are considered.•The effect of combined action on bridge pier responses and the distribution of hydrodynamic pressures are summarized.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In the territory of Herzegovina there is a large number of masonry buildings, the age of which exceeds 50 years. These are mostly smaller buildings, with one to two floors, while the load-bearing ...walls are mainly made of cut stone in lime mortar. Larger buildings with load-bearing walls made of bricks and concrete blocks in cement-lime mortar appeared a little later. The floor structures mainly consist of timber oak beams, supported by load-bearing walls, with boarding on the upper side and plaster, on reed netting, on the lower side. Such structures are exceptionally sensitive to seismic action, and almost certainly could not withstand the design seismic load without significant damage and collapse. A nonlinear static analysis of the structure of one such building was performed in this paper. A check of the existing condition was performed in the first analysis, and a check of the partially strengthened structure in the second. It is evident from the analysis that such strengthening significantly improves the bearing capacity, while the increase in deformability (ductility) is significantly smaller due to the very high stiffness of such structures.
•The evaluation method of model boundary effect and dynamic characteristics of shaking system is put forward.•A method for evaluating the failure mode of model soil based on MSE is proposed.•A damage ...evaluation method of EMD energy damage index for lining is proposed.
This paper presents the findings of a series of shaking table tests conducted to investigate the seismic damage and dynamic characteristics of a tunnel crossing a sliding surface system. An evaluation methodology is introduced to assess the model’s boundary effects and dynamic characteristics. In this study, we propose a model soil failure mode assessment method based on Marginal Spectral Entropy (MSE) using Hilbert-Huang Transform (HHT) and information entropy parameters. Furthermore, a damage evaluation method for tunnel lining is presented, which utilizes the Hilbert Energy Spectrum (HES) and an Empirical Mode Decomposition (EMD) energy damage index. The results of the tests reveal that the MSE accurately reflects the slope failure process and provides insights into the depth of the sliding surface. The observed behavior of the model indicates a push-back shear slip type characterized by sinking, squeezing, pulling, and shearing. The HES analysis of the model soil indicates that the energy primarily concentrates in the frequency range of 0 to 25 Hz, expanding with elevation. Notably, the tunnel crossing the hauling sliding surface exhibits a more pronounced broadband effect in the model soil compared to the main sliding surface. The peak HES of the lining occurs after that of the model soil and is found to be 18.07 s. The damage index distribution correlates with the spatial position of the lining parts. When the damage index exceeds 90 %, it indicates the presence of significant damage to the specific parts of the lining, a finding that has been validated through post-seismic analysis. Furthermore, the EMD energy damage index, in conjunction with dynamic finite element simulation, demonstrates its potential for preliminarily determining the location and extent of lining damage through abrupt changes. The research findings contribute to the theoretical understanding of extracting damage features in tunnel-landslide models.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•An efficient procedure for the collapse mechanism evaluation of existing RC bridges under horizontal loads is presented.•Three different scenarios of corrosion levels are considered.•A multimodal ...pushover analysis approach is adopted.•The results obtained for the different corrosion levels are discussed considering brittle and ductile failure mechanisms.
The structural safety and durability of existing reinforced concrete bridges can be considered as one of the current most important research topics in structural engineering, especially after the numerous collapses that have occurred in recent years. Considering the Italian context, it is important to highlight that most of these structures were built in the 1960s and 1970s and, consequently, the effects of materials degradation phenomena have reduced their vertical and horizontal load-bearing capacity.
This paper presents an efficient procedure for the collapse mechanism evaluation of existing reinforced concrete motorway bridges under horizontal loads, considering the corrosion effects due to carbonation through a simplified model that takes into account the steel rebars reduction and applying a multi-modal pushover analysis approach. In this study, three different (slight, moderate and high) corrosion scenarios are considered for two existing reinforced concrete bridges characterized by frame piers. The results of the numerical analyses, which consider both brittle and ductile failure mechanisms, highlight a significant decrease of the seismic capacity of the structures as the corrosion level increases, especially for brittle collapse mechanisms that are strongly affected by the bridge maintenance condition. Such a procedure allows identifying the first structural elements reaching the collapse, providing useful information for the maintenance of existing bridges in terms of repair and strengthening interventions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Актуальность работы. В статье анализируются требования к расчетному сейсмическому воздействию. Прежде всего, это обеспечение запаса прочности сооружения при рассмотрении его предельных состояний. С ...этой точки зрение понятие похожести реального и расчетного воздействия весьма условны. По крайней мере, внешнего сходства реального и расчетного воздействия не требуется. Вместе с тем расчетное воздействие должно иметь ряд характеристик близких к реальным. Цель работы. В статье анализируется три группы характеристик: кинематические, энергетические и спектральные. Из кинематических характеристик детально проанализированы пиковые ускорения и коэффициент гармоничности. Установлена связь этих характеристик с преобладающим периодом воздействия на акселерограмме. Предложена новая модификация коэффициента гармоничности с учетом остаточных смещений после землетрясения. Методы работы. Для оценки пиковых ускорений предложена методика, основанная на шкале балльности и не требующая привлечения других нормативных документов и карт ОСР. Результаты работы. Отмечено, что кинематические характеристики являются основными для проведения силовых расчетов на действие проектного землетрясения. В качестве энергетических характеристик рассмотрены интенсивность по Ариасу, абсолютная кумулятивная скорость, плотность сейсмической энергии, среднеквадратичные ускорения и показатель Парка-Янга. Показано, что энергетические характеристики в рамках одного балла постоянны и не зависят от спектрального состава воздействия. Получены доверительные границы для оценки интенсивности по Ариасу и абсолютной кумулятивной скорости. Отмечено, что энергетические характеристики являются определяющими для расчетов конструкций за пределами упругости на действие максимального расчетного землетрясения. При анализе спектральных характеристик помимо традиционных спектров ответа рассмотрены спектр работы сил пластического деформирования и предложенный авторами спектр повреждаемости сооружения. Первый спектр важен для расчета упругопластических систем, а второй – для расчета адаптивных систем. При моделировании спектрального состава воздействия авторы считают необходимым исходить из использования резонансных для сооружения расчетных воздействий. Уход от этого принципа должен иметь веское обоснование сейсмологов, которые, наряду с инженерами-проектировщиками должны нести за это финансовую и юридическую ответственность.
Relevance. The paper analyzes requirements for the design seismic input. First of all, it is ensuring the structure safety margin when considering its limiting states. From this point of view, the concept of similarity between real and design actions is rather indefinite. At least, no external similarity between the real and the design actions is required. At the same time, the design action should have a number of characteristics close to real ones. Aim. The paper analyzes three groups of such characteristics: kinematic, energy and spectral ones. Out of the kinematic characteristics, the peak accelerations and the harmonic coefficient are analyzed in detail. The relationship of these characteristics with the input predominant period on the accelerogram has been established. A new modification of the harmonic coefficient is proposed, taking into account the residual displacements after the earthquake. Methods. To assess peak accelerations, the authors proposed a method based on a scale of earthquake intensity, which does not require the use of other regulatory documents and seismic zoning maps. Results. It is noted that the kinematic characteristics are the main ones for carrying out force calculations of structures under the action of a design earthquake. The Arias intensity, absolute cumulative velocity, seismic energy density, root-mean-square acceleration and Park-Young indicator are considered as energy characteristics. It is shown that the energy characteristics in the frame of the same seismic intensity are constant and do not depend on the action spectral composition. Confidence limits for the Arias intensity and absolute cumulative velocity estimates were obtained. It is noted that the energy characteristics are important for calculations of structures out of elasticity area under maximum design earthquake. When considering the spectra, besides the response spectra, the spectrum of the work of plastic deformation forces and the spectrum of structure damageability are considered. The former spectrum is important for calculating elastoplastic systems, and the latter one is important for calculating adaptive systems. When modeling the action spectral composition, it is necessary to use resonant design input for the calculated structure. A contravention of this requirement must have a strong rationale for seismologists, who must bear financial and legal responsibility for this solution.
•The effects of uncertain geometry on the collapse of masonry arch are considered.•Probabilistic models are adopted to describe the geometrical uncertainties.•The arch horizontal carrying capacity is ...evaluated by a limit analysis procedure.•Geometrical uncertainties reduce the bearing capacity of the arch.•Uncertainties effects are described by a safety factor versus a stereometry parameter.
This paper aims to evaluate the effect of the geometrical uncertainties on the collapse condition of the circular masonry arch in presence of horizontal actions. Adopting Heyman’s hypotheses about the material, a limit analysis based procedure has been developed in order to evaluate the horizontal loads multiplier, taking into account the uncertainties related to the imprecisions of construction, the shape defects of the voussoirs or the deterioration level. The collapse state has been determined in terms of horizontal loads multiplier, whose statistical moments up to second order and probability density functions have been evaluated versus a stereometry parameter. The comparison between the obtained results and those related to the nominal geometry highlighted that the uncertainties effects could reduce significantly the nominal bearing capacity of the structure. Within this context, a safety factor, which takes into account such effects, is introduced.
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