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.
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.
Cross-sea–cable-stayed bridges located in earthquake-prone areas can be subjected to earthquakes, wave action, and other dynamic loads of potential threats during their construction and service ...periods. The dynamic response of a cable-stayed bridge was studied under the combined effects of earthquakes and wave flow. In this study, a cross-sea–cable-stayed bridge is investigated as a prototype. ANSYS software was used to establish a spatial finite-element model, and CFD software was used to simulate the wave loads and calculate the fluid-structure coupling. The peak displacement at each location was determined under different loading conditions during the combined action of earthquakes and waves. The displacement at the top of the tower was the largest, followed by that at the main span. However, when the wave action was severe, the peak displacements of the tower top and main span were comparable, and these two peak displacements occurred simultaneously. The internal-force-response law at the bottom of the tower tended to be consistent, and only the peak values differed. The peak change in the shear force was smaller than that in the bending moment. Earthquakes and waves had a negative effect on bridges; however, they played a dominant role. Nevertheless, the presence of waves alters the dynamic response during joint action; therefore, the effect of waves on the bridge cannot be ignored. The root-mean-square (RMS) under the joint action of earthquakes and waves was evaluated using the RMS of superimposed independent earthquakes and independent waves. However, it can be observed that the joint effect is not a simple superposition effect. Complex interactions exist between the earthquakes and waves.
•Using a cross-sea cable-stayed bridge as a background, a spatial finite element model of the bridge was established by ANSYS, and wave loads were simulated by CFD software.•Investigating the dynamic response of bridge key sections under the combined action of earthquakes and waves.•Proving that the combined effects of earthquakes and waves on bridges are not a superposition of dynamic responses, but a complex coupling between earthquakes and waves.
•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.
The seismic response and strengthening of two complex monumental masonry churches located in Northern Italy have been investigated through an advanced macro-modelling FE-based approach. An extensive ...documentary research and several field surveys have provided a fundamental preliminary knowledge of the two churches. Detailed three-dimensional FE models with a damage plasticity behavior for masonry have been developed and non-linear dynamic analyses have been performed to simulate the damage distribution in the churches and to identify the most vulnerable macro-elements. The analyses have highlighted the effects of geometrical features and masonry coverings on the seismic behavior of the two churches. The examination of the results in terms of tensile damage contour plots, maximum normalized displacements and energy density dissipated by tensile damage has provided a thorough description of the seismic response of both the whole church and the different macro-elements. In this regard, the procedure utilized could be regarded as a general guideline to follow for a realistic insight into the seismic response and failure analysis of large complex masonry structures without box behavior. From the results obtained, a hypothetical strengthening intervention has been implemented in the numerical models of the two churches according to the Italian Code, in order to quantitatively estimate the vulnerability reduction. A decrease of both tensile damage and displacements has been observed for the critical elements of the two churches in the case of strengthened models. Moreover, the results have shown the importance of the presence of the nave masonry covering to increase the effectiveness of the strengthening intervention, preventing the out-of-plane mechanism of the nave walls.
•Failure analysis of two monumental masonry churches under seismic actions.•Identification of the critical macro-elements.•Effects of geometrical features and coverings on the seismic response.•Effectiveness of a strengthening intervention.•Strengthening implementation to reduce vulnerability on the base of the NLDAs results.
This paper aims to evaluate the limit equilibrium condition and the minimum thickness of masonry arches in presence of horizontal loads. The analysis fits into the frame of limit analysis referring ...to Heyman's theory. Two types of arches are analysed, the circular and pointed one. The loading system consists of vertical and horizontal loads, which refer respectively to the self-weight of the voussoirs and to the seismic actions. The collapse mechanism and the corresponding horizontal load multiplier are determined, in the condition of rigid abutments, as functions of the geometrical features of the structure. The results are supported by some simple experimental tests and a sensitivity analysis, which considers the effect of geometrical irregularities on the load multiplier.
•A numerical iterative procedure for the collapse analysis of circular and pointed masonry arches is developed.•Some classes of collapse mechanisms of pointed arches are identified, depending on the geometrical parameters.•Minimum thickness for circular and pointed arches is evaluated in presence of vertical and horizontal loads.•A probabilistic sensitivity analysis on the lateral load multiplier is carried out by varying the geometrical parameters of the circular and pointed arch.
