Search Results (69)

The nonlinear static (pushover) procedure for estimating target displacement is incorporated in Annex B of Eurocode 8 and is commonly implemented through the N2 method, originally developed at the University of Ljubljana. While advanced nonlinear dynamic analyses can provide detailed insight into seismic structural behavior, they require sophisticated modeling and significant computational effort. In contrast, simplified procedures are often preferred in engineering practice for preliminary assessment and design verification. This study evaluates the applicability of the N2 method by comparing analytically obtained target displacements with experimentally measured responses of a three-story model building subjected to seismic excitation. The nonlinear capacity curve derived from pushover analysis is transformed into the acceleration–displacement response spectrum (ADRS) domain and evaluated against the demand spectrum to determine the performance point. The experimentally obtained value, reported in a reference study, is used as a benchmark for assessment. The results indicate that the N2 method provides an approximate but rapid estimation of target displacement. The findings highlight both the practical usefulness and the inherent limitations of the N2 approach when applied to structures. Full article

Urban infrastructure in seismic zones demands efficient and scalable tools for damage prediction. This study introduces an attention-integrated progressive transfer learning (PTL) framework for the seismic vulnerability assessment (SVA) of reinforced concrete (RC) frame buildings. Traditional simulation-based vulnerability models are computationally expensive and dataset-specific, limiting their adaptability. To address this, we leverage a pretrained artificial neural network (ANN) model based on nonlinear static pushover analysis (NSPA) and Monte Carlo simulations for a 4-story RC frame, and extended its applicability to 2-, 8-, and 12-story configurations via PTL. An attention mechanism is incorporated to prioritize critical features, enhancing interpretability and classification accuracy. The model achieves 95.64% accuracy across five damage categories and an R² of 0.98 for regression-based damage index predictions. Comparative evaluation against classical and deep learning models demonstrates superior generalization and computational efficiency. The proposed framework reduced retraining requirements across varying building heights, shows potential adaptability to other structural typologies, and maintains high predictive fidelity, making it a practical AI solution for structural risk evaluation in seismically active regions. Full article

In low to medium-seismicity countries, seismic design is often not mandatory. Furthermore, zoning is frequently adopted to justify simplified calculations based on force methods without capacity criteria. However, risk analysis should merge vulnerability, threat, and exposure. So even regions with low seismicity can face potentially high consequences due to earthquakes. This is the case of Brazil, where seismic provisions were lacking until 2006 when the first standard was approved, being updated in 2023. Therefore, this study selected a typical RC frame configuration and focuses on assessing the differences in seismic performance between the provisions outlined in EN1992-1-1/EN1998-1 and ABNT NBR15421. The research highlights how different requirements affect low and medium-seismicity regions. Hence, the methodology and conclusions can serve as a guide for decision-making in other countries regarding impact and effectiveness. There are considered different scenarios of design, seismicity, and ductility class. The nonlinear static Pushover analysis was conducted and also validated with nonlinear dynamic Time-history analysis. The assessment of the results is based on the design assumptions, capacity curves, collapse mechanism, IDA curves, PSDM, damage limit states and cost-benefits. Non-seismic design structures had a premature brittle collapse. The global ductility condition was the main key to changing into a ductile mechanism, and seismic detailing was the variable that addresses the ductility level. Full article

Earthquakes remain among the most destructive natural hazards, causing severe loss of life and property in seismically active regions such as Nepal. Major events such as the 1934 Nepal–Bihar earthquake (M_w 8.2), the 2015 Gorkha earthquake (M_w 7.8), and the 2023 Jajarkot earthquake (M_L 6.4) have repeatedly exposed the vulnerability of Nepal’s built environment. In response, the Ready-to-Use Detailing (RUD) guideline (NBC 205:2024) was introduced to provide standardized structural detailing for low-rise reinforced concrete buildings without masonry infill, particularly for use in areas where access to professional engineering services is limited. This study was motivated by the need to critically assess the structural performance of buildings designed according to such rule-of-thumb detailing, which is widely applied through owner–builder practices. Nonlinear pushover analyses were carried out using finite element modelling for typical configurations on soil types C and D, under peak ground accelerations of 0.25 g, 0.30 g, 0.35 g, and 0.40 g. The response spectrum from NBC 105:2020 was adopted to determine performance points. The analysis focused on global response, capacity curves, storey drift, and hinge formation to evaluate structural resilience. The maximum story drift for the linear static analysis is found to be 0.56% and 0.86% for peak ground acceleration of 0.40 g, for both three and four-storied buildings. Also, from non-linear static analysis, it is found that almost all hinges formed in the beams and columns are in the Immediate Occupancy (IO) level. The findings suggest that the RUD guidelines are capable of providing adequate seismic performance for low-rise reinforced concrete buildings, given that the recommended material quality and construction standards are satisfied. Full article

This article presents a numerical study of the influence of applied nonlinearities on the response of a flat slab–column structure under progressive collapse conditions. A key aspect of the work is the extension of nonlinear static analysis by considering cases of material nonlinearity combined with both linear and nonlinear geometry, using a corotational formulation and a damage-based elasto-plastic concrete model. A multi-layer shell element implemented in the OpenSees platform is used to distinguish between the strength characteristics of the concrete and reinforcement, with particular attention given to the modeling of the slab–column connection in nonlinear analyzes involving both shell and beam elements. The applied vertical pushover analysis enabled the derivation of load–displacement curves and the identification of the sequence in which plastic hinges can be formed. The development of membrane action resistance, expressed through the formation of compressive and tensile rings, is observed numerically when both material and geometric nonlinearities are simultaneously considered. Moreover, the transition from compressive membrane action to tensile membrane action occurs once the deflections reach the value equal to the effective depth of the slab. This insight may serve as an important guideline for the development of future revisions to design standards related to progressive collapse. Full article

Conventional seismic design regulations, even when rigorously adapted to local conditions, often fail to ensure the resilience of reinforced concrete buildings. Code-based prescriptive methods rely on simplified assumptions that do not fully capture the complex nonlinear behavior of structures during strong earthquakes, potentially underestimating seismic demands and structural vulnerabilities. This study evaluates the seismic performance of a 44-story reinforced concrete building designed per the EN-2015 code, currently adopted in Ethiopia. The building was analyzed using Response Spectrum Analysis (RSA), Linear Dynamic Time History Analysis (LDTHA), and Classical Modal Analysis in ETABS v19, with 11 ground motions from the PEER database. Ground motion scaling was performed using SeismoMatch and ETABS. Results indicate that LDTHA predicts 25.68% higher maximum story displacement, 26.49% greater inter-story drift ratios, 15.35% higher story shear, and 27.5% greater overturning moments compared to RSA. The fundamental time period for the first mode was found to be 3.956 s in Classical Modal Analysis, 3.806 s in RSA, and 3.883 s in LDTHA. These discrepancies highlight the limitations of code-based design and underscore the necessity of performance-based seismic design for achieving safer, more resilient structures in high-seismic regions. Full article

Performance-based seismic design (PBD) has emerged as a key approach for rationalizing prescriptive code provisions and improving the explicit assessment of structural performance. In Chile, where reinforced concrete shear wall buildings are the predominant structural typology, evaluating their seismic response beyond traditional linear methodologies is crucial. This study assesses the seismic performance of a representative Chilean shear wall residential building using the ACHISINA manual’s performance-based seismic design framework. A nonlinear static (pushover) analysis is performed to verify compliance with prescribed design criteria, incorporating capacity design principles and a moment envelope approach to prevent premature yielding in upper stories. The results confirm that the building meets the performance objectives for both Immediate Occupancy and Additional Deformation Capacity limit states. The application of capacity design effectively controls shear demand, preventing brittle failure, while the flexural design ensures the formation of the yielding mechanism (plastic hinge) at the intended critical section. Additionally, the study highlights the limitations of pushover analysis in capturing higher-mode effects and recommends complementary nonlinear time-history analysis (NLTHA) for a more comprehensive assessment. The computed response reduction factors exceed those used in the prescriptive design, suggesting a conservatively safe approach in current Chilean practice. This research reinforces the need to integrate performance-based methodologies into Chilean seismic design regulations, particularly for shear wall structures. It provides valuable insights into the advantages and limitations of current design practices and proposes improvements for future applications. 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 numerically investigated retrofitted transmission towers subjected to static wind loads using nonlinear pushover analysis, emphasizing enhanced structural resilience and safety. Transmission towers are critical infrastructure that must withstand extreme wind conditions. However, aging structures and increasing load demands necessitate effective retrofitting strategies. The nonlinear pushover analysis employs advanced finite element modeling to simulate the nonlinear inelastic behavior of towers under incremental static wind loads until failure. Six retrofitting methods are presented and compared to identify the most effective retrofitting approach for the considered tower. The findings reveal that retrofitting significantly improves the capacity, ductility, and stiffness of transmission towers under static wind loads, delaying buckling and failure. The proposed retrofit method enhances tower capacity by at least 10% compared to the non-retrofitted configuration. Full article

The 7.7 and 7.6 magnitude Pazarcık and Elbistan earthquakes that struck Kahramanmaraş on 6 February 2023 caused widespread structural damage across many provinces and are considered rare in seismological terms. While many reinforced concrete (RC) buildings designed under current earthquake regulations sustained significant damage, some older RC buildings with outdated designs sustained only moderate damage. This study aims to analyze the seismic performance of such older RC buildings to understand why they did not collapse or suffer severe damage. An 8-story RC building in Adıyaman province, damaged by the earthquake, was considered for analysis. The region’s seismicity and local site conditions were assessed through borehole operations, geotechnical laboratory tests, and seismic field tests. The soil profile was modeled, and one-dimensional seismic site response analyses were performed using records from nearby stations (TK 4615 Pazarcık and TK 4612 Göksun stations) to determine the foundation-level earthquake record. Nonlinear static pushover analysis was carried out via SAP2000 and STA4CAD, utilizing site response analysis and test results taken from the reinforcement and concrete samples of the building. The findings, compared with the observed damage, provide insights into the performance of older RC buildings in this region. Full article

Terrestrial laser scanners (TLS) are widely employed in structural health monitoring (SHM) of large objects due to their superior capabilities compared to traditional geodetic methods. TLS provides rapid and detailed data on the geometric properties of objects, enabling various types of analyses. In this study, TLS was utilized to examine the minaret of the Bjelave Mosque, located in Sarajevo, Bosnia and Herzegovina. The inclination of the minaret was assessed using principal component analysis (PCA) and linear regression (LR) applied to sampled data from four edges of the minaret’s body. The geodetically determined inclination values were used as input data for subsequent static and pushover analyses conducted in DIANA FEA, where the minaret was modeled. The analyses indicate that the inclination increases stress and strain, leading to larger cracks and reduced structural capacity, as demonstrated by the pushover analysis curves. This study highlights the combined impact of structural inclination, water infiltration, and settlement on the minaret’s integrity and proposes these findings as a basis for future maintenance and strengthening measures. Full article

The Castle of Lanjarón is a 16th century stronghold located in Andalucía, Spain. After losing its military function, the castle was abandoned, leading to significant decay. Designated a national heritage site in 1985, recent efforts have sought to preserve its historical and cultural value. This study outlines an inspection and diagnosis campaign carried out on the castle. Non-destructive tests (NDTs) were employed to characterize the properties of the masonry, using both mechanical and wave-based methods. Dynamic identification was performed to determine dynamic and modal properties of the structure, which were used to develop and calibrate a three-dimensional (3D) finite element model (FEM) of the west wall, based on homogenized masonry material. Limit analysis and non-linear static (pushover) analysis under various boundary conditions were conducted to determine the maximum relative load factor in the out-of-plane direction. The results were compared to the expected peak ground acceleration (PGA) of the area, showing that the maximum load capacity of the wall exceeds local seismic demands with a safety factor of 1.39. The study highlights the efficacy of pairing a homogenized macro-modeling approach with wave-based and dynamic identification methods, particularly for resource efficiency. Finally, recommendations for future conservation efforts have been provided. Full article

Despite the many advantages of tube systems with braces, known as trussed tubes, no specific seismic design criteria exist in the current regulations to design them, and practitioners utilize common methods used for common building structures to deal with designing such systems. The aim of this study is to investigate the performance of a 31-story steel trussed-tube building designed according to the customary design provisions. To evaluate the performance of the code-conforming designed structure, a three-dimensional nonlinear static (pushover) analysis is employed, and the acceptance criteria corresponding to different performance levels are examined. The obtained performance-based results are then compared with the design based on the customary guidelines, and the shortcomings of common design regulations in the design of trussed-tube buildings are highlighted. By observing the state of the plastic hinges, as well as force-controlled joints at two distinct earthquake hazard levels, it is found that the structure under study, which was loaded, analyzed, and designed exactly in compliance with the requirements of the regulations and standards, does not satisfy the performance criteria. In a typical nonlinear brace hinge, for instance, the results indicate that the LS acceptance criterion has been exceeded by approximately 30 percent at the BSE-1 hazard level. Also, the drifts surpass the 1% limit at specific levels, with the maximum drift reaching approximately 1.4%. As a result, the design of trussed-tube systems based on common codes and regulations can lead to an unsafe design that lacks the expected performance intended in their service life. Full article

The procedure of estimating the seismic displacement capacity of piles under each performance level in current wharf practices involves monitoring the material strains specified in the design criteria during nonlinear static pushover analysis with a complex numerical model. Thus, a simplified procedure for concrete piles is proposed by developing closed-form formulas for displacement ductility capacity and yield displacement of piles, while the displacement capacity is the product of ductility capacity and yield displacement. The ductility capacity assures that the pile material strain limits specified in the criteria are not exceeded. The basic form of the formula for ductility capacity is established by using the equivalent cantilever concept to model the pile–soil interaction. Then, large quantities of moment–curvature analyses of sections and pushover analyses of concrete piles were conducted to determine the related parameters in the formula by considering numerous influencing factors. The results show that the ductility capacity can be expressed as a function of the curvature ductility capacity of pile sections at the selected performance level and parameter ψ. Based on the outcomes of curvature and pushover analyses, a set of practical formulas are proposed to determine the curvature ductility capacity, which depends on the longitudinal or transverse reinforcement ratios and axial force level, along with ψ, which depends on the aforementioned factors as well as the unsupported length of the pile. Full article

In earthquake-prone regions, the seismic performance assessment of reinforced concrete (RC) continuous bridges is critical for ensuring their resilience and safety. This study proposes a fragility curve developed through a hybrid pushover–incremental dynamic (PO-ID) analysis to accurately evaluate the seismic vulnerability of RC continuous bridges. The proposed method integrates the advantages of pushover analysis, which provides insights into the bridge’s capacity, with incremental dynamic analysis, which captures the bridge’s response under varying earthquake intensities. The resulting fragility curves offer a more comprehensive understanding of the likelihood of bridge failure at different seismic intensities. Incremental dynamic analysis (IDA) effectively illustrates a bridge’s response to increasing seismic demands but does not account for ultimate displacement under static lateral loads. Pushover analysis (POA) is useful for capturing maximum displacement capacity under static forces, yet it falls short of addressing the dynamic effects of near-fault ground motions. The hybrid approach combines the strengths of both IDA and POA, and this hybrid method’s heightened sensitivity to damage states allows for earlier detection and conservative displacement estimates, improving seismic assessments, informing design and retrofitting practices, and enhancing safety by addressing transverse displacements and weak axis vulnerabilities. Full article