Search Results (33)

This study uses a U-shaped aqueduct structure in a specific irrigation area as the research object to examine the damage patterns of large-span elevated U-shaped aqueduct structures under seismic action. A single-span aqueduct model that integrates fluid–structure interaction is created with the finite element program ANSYS. The incremental dynamic analysis approach is utilized to perform nonlinear dynamic time–history assessments for three types of bearings—plate rubber bearings, pot rubber bearings and lead-core rubber bearings—under conditions of an empty condition, a half-full condition and a design water level. Seismic fragility curves for the bearings and piers subjected to transverse seismic stress are developed using capacity–demand ratio models and specified damage limit states. The findings demonstrate that the likelihood of aqueduct components being damaged increases substantially as seismic intensity increases, with bearings failing before piers. Under the conditions of empty, half-full and design water levels, the structural mass increases as a result of higher water levels. This alters the dynamic response characteristics and increases the likelihood of failure in a variety of damage states. The probability of plate rubber bearings experiencing minor damage exceedance increases from 11.75% to 61.6% as the water level rises from vacant to design conditions. Lead-core rubber bearings provide better seismic isolation than plate rubber bearings and pot rubber bearings. This greatly lowers the aqueduct structure’s displacement response and damage likelihood. Under design water level circumstances, the chance of mild damage to lead rubber bearings is 8.64%, at a peak ground acceleration of 0.4 g. The damage probabilities for the pot rubber bearings and the plate rubber bearings are 80.68% and 97.45%, respectively. The research findings establish a theoretical foundation for the seismic design and damage evaluation of aqueduct structures in places with high seismic activity, ensuring the stable operation of water transfer projects and sustainable water resource utilization, presenting considerable technical applicability. Full article

In earthquake-prone regions, predicting the impact of seismic events on highway bridges is crucial for post-earthquake effective emergency response and recovery planning. This paper presents a methodology for a simplified seismic risk assessment of bridges using fragility curves that integrates updated ductility ratios of reinforced concrete bridge columns from literature based on experimental results on cyclic tests of reinforced concrete circular columns. The methodology considers two damage states (cover spalling and bar buckling) for bridge columns with seismic and non-seismic design considerations and then estimates displacement thresholds for each damage state. The Damage Margin Ratio (DMR) is introduced as an index defined by the ratio of the median Peak Ground Acceleration (PGA) for a specific damage state to the PGA that corresponds to the target seismic hazard probability of exceedance in 50 years that is typically defined in bridge design and evaluation codes and standards. The DMR is then compared to a user-specified Threshold Damage Margin Ratio (TDMR) to evaluate the level of risk at a specific threshold probability of exceedance of the damage state (5% and 10%). Comparative assessment is conducted for the relative seismic risk and performance of non-seismic and seismic bridges corresponding to the seismic hazard values at 10% and 2% probability of exceedance in 50 years for 7 urban centers in the province of Quebec as a case study demonstration of the methodology. The proposed methodology offers a rapid tool for screening and prioritizing bridges for detailed seismic evaluation. Full article

This study evaluates the seismic fragility and code compliance of reinforced concrete buildings in Turkey following the 6 February 2023 Kahramanmaraş earthquake. Sixty representative buildings were modeled in SAP2000, consisting of thirty structures designed according to TEC-1975 and thirty according to TEC-1998. These models were subjected to three-dimensional nonlinear time history analyses using ground motions scaled to match the seismic characteristics of the earthquake. Structural performance was assessed by comparing calculated displacement demands with capacity thresholds defined by modern code provisions. The results show that buildings designed under TEC-1998 generally performed better than those constructed according to TEC-1975, particularly in terms of deformation capacity and collapse resistance. Fragility curves and exceedance probabilities were developed to quantify damage likelihoods across different performance levels. When compared with post-earthquake field observations, the analytical models produced lower collapse rates, which may suggest the presence of widespread code noncompliance in the actual building stock. These findings highlight the critical importance of ensuring adherence to seismic design regulations to improve the resilience of existing structures. Full article

The seismic performance assessment of timber structures and topology optimization have been widely researched in recent years. Furthermore, the use of wood as a construction material has increased due to new sustainability challenges. This research assesses the seismic performance of a topologically optimized timber building located in Concepcion, Chile. The structure is a five-story glulam braced frame, designed following current Chilean standards. The structural configuration was obtained through a topology optimization process using a variation of a soft-kill BESO algorithm implemented in MATLAB R2015a, obtaining topologies with low structural redundancy. For the analysis, a full 3D nonlinear model was prepared using OpenSees (Version 3.7.1), and the nonlinear behavior of the structure was only considered at joints using the backbone curves introduced in ASCE 41-13. Six different study cases were analyzed, varying joint strengths and ductility. The fragility curves were determined from a static pushover analysis (SPO) using SPO2FRAG (V1.1), considering the performance levels established in ASCE 41-13. The seismic hazard of the building’s site is estimated through a probabilistic seismic hazard analysis (PSHA), and the seismic performance of each case is determined by computing the probabilities of exceedance of the considered limit states. Analysis results show that wood braced-frame structures with low structural redundancy (and fewer main joints to dissipate energy), such as those obtained from topology optimization algorithms, exhibit a markedly brittle behavior with almost no displacement ductility. This undesirable behavior does not improve by providing more deformation capacity to this structure’s reduced number of main joints. Currently, the Chilean standard for seismic design requires a unique response modification factor R for wood structures. This research suggests that this requirement should be revisited, specifying different R values depending on the wood structure’s redundancy, considering that its displacement ductility comes almost exclusively from the nonlinear deformation capacity of joints. Full article

This study investigated the seismic performance and assessed the seismic fragility of an existing pentapod suction-bucket-supported offshore wind turbine, focusing on the amplification of earthquake ground motions. A simplified suction bucket–soil interaction model with nonlinear spring elements was employed within a finite element framework, linking the suction bucket and soil to hypothetical points on the OWT structures at the mudline. Unlike conventional approaches using bedrock earthquake records, this study utilized free-field surface motions as input, derived from bedrock ground motions through one-dimensional wave theory propagation to estimate soil-layer-induced amplification effects. The validity of the simplified model was confirmed, enabling effective assessment of seismic vulnerability through fragility curves. These curves revealed that the amplification effect increases the vulnerability of the OWT system, raising the probability of exceeding damage limit states such as horizontal displacement of the tower top, tower stress, and horizontal displacement at the mudline during small to moderate earthquakes, while decreasing this likelihood during strong earthquakes. Comparisons between the Full Model and the simplified Spring Model reveal that the simplified model reduces computational time by approximately 75%, with similar seismic response accuracy, making it a valuable tool for rapid seismic assessments. This research contributes to enhancing seismic design practices for suction-bucket-supported offshore wind turbines by employing a minimalist finite element model approach. Full article

Coseismic surface displacement can cause major damage to buildings located on faults. Therefore, it is important to quantitatively evaluate the future surface displacement of active faults. The commonly used deterministic evaluation methods often tend to overestimate surface displacement values, so researchers are working toward probabilistic fault displacement hazard analysis (PFDHA). However, the PFDHA assumes that earthquakes occur equally in time, which is not consistent with the physical mechanism of earthquake occurrence. Elastic rebound theory and paleoseismic research results show that the accumulation and release of energy in the crustal medium have cyclical characteristics. In this study, using two parameters, the strong earthquake recurrence period (T_RP) and strong earthquake elapsed time (t_et), of active faults, the displacements of active faults with different T_RP and t_et under different exceedance probabilities are obtained. The calculation results indicate that the surface displacement hazard of the weakly active and extremely weakly active faults in the Holocene does not need to be considered; for the moderately and strongly active faults in the Holocene, the surface displacement result is lower than that provided by the deterministic method. According to the importance of the project, the calculation results of the PFDHA-td method under different exceedance probabilities are selected. Full article

The membrane structure or membrane roofing system is lightweight and flexible, with wind being the primary cause of structural and membrane material failure. To evaluate the disaster prevention and mitigation capacity of the membrane roofing system and enhance the wind disaster risk management capabilities, this paper studies the exceedance probability evaluation method for different wind resistance requirements of membrane roofs. Taking Hangzhou in China as an example, the design wind speed risk curve fitted by polynomial is obtained by referring to the PEER performance-based seismic design method and considering the randomness of the wind field. A polynomial fitting method is employed to obtain the design wind speed hazard curve. Considering the nonlinear characteristics of the membrane roof structure, the relationship between the roof’s wind resistance requirements (vertical displacement limits) and wind speed spectrum values is approximated using a power function. An annual average exceedance probability expression is derived for different normal deformation demand values of the membrane roofs under wind load. Based on this, a wind resistance probability evaluation method for membrane roofs considering aerodynamic stability is proposed, along with specific steps and related analytical formulas. The results indicate that polynomial fitting provides an effective simplification for deriving the annual average exceedance probability expression for the wind resistance demand of membrane roofs. The performance-based wind resistance probability evaluation method allows for obtaining exceedance probability values for different displacement requirements with minimal structural analysis, which enriches the wind resistance design theory of membrane roofs and further ensures the structural safety of tension membrane roofs under wind load. Full article

The structural integrity of buried pipelines is threatened by the effects of Permanent Ground Deformation (PGD), resulting from seismic-induced landslides and lateral spreading due to liquefaction, requiring accurate analysis of the system performance. Analytical fragility functions allow us to estimate the likelihood of seismic damage along the pipeline, supporting design engineers and network operators in prioritizing resource allocation for mitigative or remedial measures in spatially distributed lifeline systems. To efficiently and accurately evaluate the seismic fragility of a buried operating steel pipeline under longitudinal PGD, this study develops a new analytical model, accounting for the asymmetric pipeline behavior in tension and compression under varying operational loads. This validated model is further implemented within a fragility function calculation framework based on the Monte Carlo Simulation (MCS), allowing us to efficiently assess the probability of the pipeline exceeding the performance limit states, conditioned to the PGD demand. The evaluated fragility surfaces showed that the probability of the pipeline exceeding the performance criteria increases for larger soil displacements and lengths, as well as cover depths, because of the greater mobilized soil reaction counteracting the pipeline deformation. The performed Global Sensitivity Analysis (GSA) highlighted the influence of the PGD and soil–pipeline interaction parameters, as well as the effect of the service loads on structural performance, requiring proper consideration in pipeline system modeling and design. Overall, the proposed analytical fragility function calculation framework provides a useful methodology for effectively assessing the performance of operating pipelines under longitudinal PGD, quantifying the effect of the uncertain parameters impacting system response. Full article

Seismic risk expresses the expected degree of damage and loss following a catastrophic event. An efficient tool for assessing the seismic risk of embankments is fragility curves. This research investigates the influence of embankment’s geometry, the depth of rupture occurrence, and the underlying sandy soil’s conditions on the embankment’s fragility. To achieve this, the response of three highway embankments resting on sandy soil was examined through quasi-static parametric numerical analyses. For the establishment of fragility curves, a cumulative lognormal probability distribution function was used. The maximum vertical displacement of the embankments’ external surface and the fault displacement were considered as the damage indicator and the intensity measure, respectively. Damage levels were categorized into three qualitative thresholds: minor, moderate, and extensive. All fragility curves were generated for normal and reverse faults, as well as the combination of those fault types (dip-slip fault). Finally, the proposed curves were verified via their comparison with those provided by HAZUS. It was concluded that embankment geometry and depth of fault rupture appearance do not significantly affect fragility, as exceedance probabilities show minimal differences (<4%). However, an embankment founded on dense sandy soil reveals slightly higher fragility compared to the one founded on loose sand. Differences regarding the probability of exceedance of a certain damage level are restricted by a maximum of 7%. Full article

The suction bucket foundation equipped for offshore wind turbines was a promising solution for sandy seabed locations. However, its typically short embedment depth presented additional challenges when installed in seismic zones. These challenges pertained not only to structural response but also to the seismic motion itself, which was strongly influenced by soil characteristics. This study examined the uncertainty of equivalent shear-wave velocities to explore the variability in input seismic motion characteristics and investigated their impact on the structural response in terms of tower-top displacement, mudline displacement, and acceleration amplification factor at the hub height of 3 MW and 5.5 MW suction bucket-supported offshore wind turbines (OWTs). Additionally, the influence of equivalent shear-wave velocities on the exceedance probabilities of various damage states, using fragility curves for tower-top and mudline displacement, was analyzed. The results indicated that equivalent shear velocities of soil significantly impacted the seismic performance of suction bucket-supported offshore wind turbines. These effects were closely related to the intensity of the seismic motion, highlighting the importance of carefully considering the correlation between site-specific shear velocities and earthquake intensities. Full article

Landslide hazard mapping is important to urban construction and landslide risk management. Dynamic landslide hazard mapping considers landslide deformation with changes in the environment. It can show more details of the landslide process state. Landslides in highly vegetated areas are difficult to observe directly, which makes landslide hazard mapping much more challenging. The application of multi-InSAR opens new ideas for dynamic landslide hazard mapping. Specifically, landslide susceptibility mapping reflects the spatial probability of landslides. For rainfall-induced landslides, the scale exceedance probability reflects the temporal probability. Based on the coupling of them, dynamic landslide hazard mapping further considers the landslide deformation intensity at different times. Zigui, a highly vegetation-covered area, was taken as the study area. The landslide displacement monitoring effect of different band SAR datasets (ALOS-2, Sentinel-1A) and different interpretation methods (D-InSAR, PS-InSAR, SBAS-InSAR) were studied to explore a combined application method. The deformation interpreted by SBAS-InSAR was taken as the main part, PS-InSAR data were used in towns and villages, and D-InSAR was used for the rest. Based on the preliminary evaluation and the displacement interpreted by fusion InSAR, the dynamic landslide hazard mappings of the study area from 2019 to 2021 were finished. Compared with the preliminary evaluation, the dynamic mapping approach was more focused and accurate in predicting the deformation of landslides. The false positives in very-high-hazard zones were reduced by 97.8%, 60.4%, and 89.3%. Dynamic landslide hazard mapping can summarize the development of and change in landslides very well, especially in highly vegetated areas. Additionally, it can provide trend prediction for landslide early warning and provide a reference for landslide risk management. Full article

A proposal to control the structural pounding hazard imposed on multistory reinforced concrete (RC) structures is presented. The main goal is to guarantee the seismic performance of a structure with an acceptable (predefined) risk-targeted parameter without the need to eliminate structural pounding collisions. The key target parameters of this study are the annual probability of exceeding an engineering demand parameter (EDP) capacity level and the separation distance d_g between adjacent structures. In this direction, a method that ensures the performance level of critical EDPs due to structural pounding conditions is proposed. The new method involves two decision frameworks that define (a) the optimal separation gap distance $\left({\mathrm{d}}_{\mathrm{g},\mathrm{m}\mathrm{i}\mathrm{n}}^{{\mathrm{P}}_{\mathrm{t}}}\right)$ at a targeted value of pounding risk (probability per year) P_t (Decision A) and (b) the minimum acceptable structural pounding risk ${\mathrm{P}}_{\mathrm{m}\mathrm{i}\mathrm{n}}^{{\mathrm{d}}_{\mathrm{g},\mathrm{t}}}$ at a targeted value of separation gap distance d_g,t (Decision B). The demand parameters that are incorporated in the proposed method are the peak relative displacement δ_max at the top level of colliding without considering pounding conditions and any other critical EDP due to the structural pounding effect. The overall method is based on two distinct acceptable performance objectives, the POs-δ_max and the POs-EDP, defined as a function of P vs. d_g. For this purpose, a seismic hazard curve compatible with Eurocode’s 8 hazard zone is adopted, and the corresponding demand hazard curves of δ_max and EDP are developed. The proposed method is implemented to study the floor-to-floor structural pounding hazard of an eight-story RC frame taking into account different risk-targeted scenarios. The results show that the seismic risk (probability per year) of exceeding the EDP’s capacity level is significantly increased due to structural pounding in comparison to the case of no pounding. Calibration of the structural pounding risk can be obtained by adjusting the separation gap distance d_g between the adjacent structures based on the acceptable POs. The POs-δ_max is not always an accurate criterion for verifying the capacity level of the critical EDP. Finally, with the proposed method, a variety of POs-EDPs can be used to control the structural pounding risk in terms of ${\mathrm{d}}_{\mathrm{g},\mathrm{m}\mathrm{i}\mathrm{n}}^{{\mathrm{P}}_{\mathrm{t}}}$ and/or ${\mathrm{P}}_{\mathrm{m}\mathrm{i}\mathrm{n}}^{{\mathrm{d}}_{\mathrm{g},\mathrm{t}}}$. Full article

The overhead gas-insulated transmission line (GIL) in ultra-high-voltage converter stations, distinct from traditional buried pipelines, demands a thorough investigation into its seismic behavior due to limitations in existing codes. A refined finite element model is established, considering internal structure, slip between various parts, and the relative displacement at the internal conductor joint. Seismic analysis reveals the vulnerability of the GIL at the corner of the pipeline height change, with two failure modes: housing strength failure and internal conductor displacement exceeding the limit. Furthermore, the acceleration amplification coefficient of the support generally exceeds 2.0. Two retrofit methods, namely increasing the fundamental frequency of all supports and fixing the connections between all supports and the housing, have been proposed. The results indicate the effectiveness of both methods in reducing the relative displacement. Fixing all the supports effectively reduces the stress, whereas the other one yields the opposite effect. The seismic performance of a GIL is determined not by the dynamic amplification of supports, but by the control of relative displacement between critical sections, specifically influenced by the angular deformation of the pipeline’s first-order translational vibration mode along the line direction. Seismic vulnerability analysis reveals a reduction of over 50% in the failure probability of the GIL after the retrofit compared to before the retrofit, with the PGA exceeding 0.4 g. Full article

The effect of an intensity measure’s (IM’s) sufficiency property on the probabilistic assessment of reinforced concrete (RC) structures due to floor-to-floor structural pounding conditions is examined. In the first part of this investigation, efficiency and sufficiency properties of 23 scalar IMs are verified. Then, the magnitude M_w and the distance R_rup are examined as elements in a vector with an efficient scalar IM to evaluate whether they have any significant effect on the structural response. Subsequently, probabilistic seismic demand models (PSDMs) are developed using linear regression analyses based on a scalar IM and a vector-valued IM. Fragility curves are developed based on these PSDMs, and the influence of M_w and R_rup on the evaluation of the minimum required separation gap distance d_g,min due to the pounding effect is examined. More than two hundred nonlinear time history analyses are performed based on the Cloud Analysis method. Seismic displacement demands that control of the global state of the structure, as well as the probability of structural pounding, are examined. The results of this research indicate that once M_w or R_rup is increased, fragility curves are shifted to greater values of IM, and the probability of the exceedance of a certain performance level is reduced. Also, the predictive power of R_rup seems to be greater than the one of M_w. On the other hand, it is revealed that M_w and R_rup induce variabilities in the demand solutions for adequate separation gap distance between the adjacent structures. Therefore, variation in M_w or R_rup may lead, in some cases, to unacceptable evaluations of the pounding effect in the capacity levels of structures. Full article

In this work, a tied braced frame (TBF) was developed to achieve uniform inelastic deformation in an eccentrically braced frame (EBF) by connecting links across the entire frame height with tie members. Herein, a TBF design method is proposed, considering a new lateral force distribution pattern. To better evaluate the seismic performance, and verify the design advantages of the TBF, nonlinear time-history analysis and fragility analysis were conducted using 6-, 10-, and 20-story TBF models designed using this method, as well as EBF models for comparison. It was found that the maximum inter-story displacement angles of the TBF model were reduced by 10%, 3.3% and 6.3% at the 84th percentile at 6, 10 and 20 stories, respectively, and the DCF values were also reduced by about 5.5%, indicating that the design of the TBF structure is more reasonable. The results revealed that the TBF models featured more uniform distributions of the normalized link shear forces and inter-story drift ratios, resulting in a better damage distribution and more ductile behavior. Furthermore, under earthquakes, the tie axial forces were similar to those calculated using the design equation, thereby indicating the reliability of the design method. Under the same seismic conditions, the PGA values of the TBF structure are about 10~15% lower at 50% exceedance probability compared to the EBF structure; the CMR values of the 6-story, 10-story, and 20-story models are 1.12, 1.09, and 1.06 times higher than those of the EBF structure, respectively. Notably, based on a comparison of the exceedance probability from the fragility analysis results for the TBF and EBF models, the TBF model exhibited better anti-collapse performance. Full article