Bulletin of Earthquake Engineering最新文献

The pressing need to address seismic risk reduction for built heritage, while ensuring economic and environmental sustainability, highlights the importance of formal design methodologies that achieve prescribed goals. In current practice, the design of seismic retrofitting is predominantly based on the designer’s experience and trial-and-error procedures, primarily focusing on structural performance. However, retrofit interventions have significant social, environmental, and economic impacts that must be integrated into the design process to enable informed decision-making. The absence of formalized criteria, combined with advancements in computational capabilities, has driven the development of structured frameworks to guide the design process. This paper presents a comprehensive literature review of engineered design frameworks for seismic retrofitting of existing structures. The state of the art includes Multi-Criteria Decision-Making (MCDM) frameworks, which rank multiple conflicting design options, and Optimization frameworks, which mathematically formalize the design process by adhering to prescribed constraints. Recent hybrid methodologies are also examined. The review explores these methodologies, traces their research evolution over time, outlines the advantages and limitations of each framework, and identifies gaps that future research must address.

The interaction of environmental aggression and seismic events may significantly reduce the seismic capacity, serviceability, and resilience of aged structures. Considering the deterioration caused by corrosion and earthquake events, it is crucial to account for the current structural state in the procedure for assessing seismic resilience. This paper presents an analytical approach for assessing seismic resilience that incorporates the influence of corrosion and mainshock-induced damages. Within this methodology, the conventional structural functionality formula is modified by incorporating a time-variant function that is dependent on mainshock damage states. An aftershock fragility is generated by the grouped damage data. An approach based on the total probability theorem is introduced to estimate the downtime caused by ageing and aftershock loadings. In the downtime estimation process, a color-tagged scheme is employed to differentiate between repair and rebuild scenarios for the damaged building. Subsequently, the seismic resilience can be evaluated using the acquired functionality, fragility, and downtime. The assessment procedure is implemented on a representative reinforced concrete frame structure to demonstrate its applicability. The results indicate that corrosion and aftershocks together cause a considerable drop in resilience index and an increase in downtime. The coupling effect of these two factors on resilience is larger than that of each individual factor. Taking into account the contribution of aftershocks and corrosion, the downtime resulting from structural damage is approximately 2.7 times longer than that associated with the mainshock alone. For the damage state induced by the mainshock, it is estimated that when the mainshock causes moderate damage to the structure, there is an approximate 22% reduction in seismic resilience, which should be considered when evaluating life-cycle resilience. The obtained results underscore the importance of considering aftershocks and corrosion, as neglecting them would lead to an overestimation of seismic resilience.

Built-up battened columns have been widely used in steel structures mainly because of providing a higher moment of inertia than solid sections with a similar weight. However, previous earthquakes and recent studies have demonstrated the poor seismic performance of these columns. This study proposes a strengthening method for deficient built-up battened columns through chord grouting and wrapping with carbon fiber-reinforced polymer (CFRP). Experimental works and numerical simulations were employed to demonstrate the efficiency of the proposed method. The experimental works included quasi-static cyclic testing of four strengthened built-up battened columns with different batten spacing and chord distances. A comparison was made between the experimental results of the strengthened columns and four similar un-retrofitted built-up battened columns. Besides, the ABAQUS program was used to simulate 54 built-up battened columns with various batten spacing, chord distances, axial stresses, CFRPs layers, and strengthened panels. The results indicated that the proposed method prevented the buckling and bulging of flange and webs, respectively. Besides, the retrofitted columns exhibited a larger lateral strength and displacement capacity.

Common building regulations typically establish the seismic design criteria based on earthquake movements occurring in far-field regions. For the areas close to faults, the codes have introduced specialized criteria or coefficients aimed at incorporating the influence of the related seismic effects into the design spectrum. While the application of these criteria is straightforward, the inherent uncertainty associated with the proposed methodologies hinders the ability to conduct a precise evaluation of the seismic performance of structures. This challenge is more pronounced concerning the distribution of drift and inelastic behavior of buildings in these regions, especially when they are influenced by the concurrent effects of three translational components of an earthquake and the flexibility of the foundation. Consequently, there is a necessity for more comprehensive investigations. In light of this, the present study conducts three-dimensional nonlinear time history analyses of 32 steel building models in OpenSees software, varying in the number of stories (ranging from 3 to 12), structural system types (special cross braced frames, SCBF and special moment resisting frames, SMRF), soil classifications (D and E based on ASCE 7–22), and base conditions (fixed and flexible). The analyses consider the simultaneous influence of three translational components of suitably selected near-field earthquake ground motions. Modeling of the soil flexibility is conducted using the Winkler approach. The comparative study of the fixed- and flexible-base structures indicates that soil-structure interaction significantly contributes to increased inter-story drifts, particularly in taller braced frames, with the first story experiencing increases of as much as 80%. Despite the decrease in the base shear due to the consideration of soil-structure interaction, it is responsible for increasing the plastic hinge rotations and the permanent displacement of the stories, particularly in the SCBF buildings. In the worst-case scenario, for the braces which are the key elements to controlling the seismic performance of the SCBF buildings, the plastic hinge rotations increase by as much as 5 times. Moreover, the permanent lateral displacement of the models can also increase by a factor of 3. In most cases, the maximum increase of the story drift due to base flexibility corresponds to the story where the story drift is the lowest in the fixed-base condition. Using the obtained results, an equation is proposed to convert the lateral displacements of a fixed-base building to those for the flexible-base case.

This study presents a comprehensive evaluation of an all-steel Tube-in-Tube Buckling-Restrained Brace (TnT-BRB) system designed for the seismic retrofitting of substandard reinforced concrete (RC) frames. A significant portion of existing RC buildings, particularly those constructed prior to the adoption of modern seismic design codes, suffer from inadequate ductility, poor joint detailing, and insufficient lateral load resistance. To address these vulnerabilities, this research integrates large-scale cyclic testing of TnT-BRB components with shake table experiments on one-third scale, single-story RC frame specimens. The experimental program involved two geometrically identical frames: one unretrofitted and one equipped with the TnT BRB system. Subjected to progressively scaled horizontal ground motions, the retrofitted frame exhibited pronounced improvements in lateral stiffness, deformation capacity, and energy dissipation. By contrast, the bare frame sustained brittle joint failures, diagonal shear cracking, and considerable residual drift at moderate excitation levels. When subjected to ground motions scaled to replicate the 2023 Kahramanmaraş earthquake, the retrofitted specimen remained structurally intact and stable, with the brace yielding in a controlled manner as intended. These outcomes were validated through detailed strain, acceleration, and displacement histories, as well as through post-test inspections. Field observations from the 2023 Kahramanmaraş earthquake further reinforce the system’s practical feasibility. Collectively, the findings demonstrate the TnT BRB system’s capacity to transform vulnerable RC frames into ductile, seismically resilient structures. The study supports the integration of such systems into performance-based retrofitting frameworks, offering a scalable and repairable solution for improving the seismic safety of existing RC buildings in high-risk regions.

The paper presents the formulation of a shell element, together with appropriate constitutive models, for the predictive simulation of non-planar RC walls. The formulation is used in blind prediction analyses of U-shaped walls recently tested at UCLouvain, in Belgium and the National Laboratory of Civil Engineering, in Portugal. The first blind prediction addressed walls UW1 and UW2, which were subjected to cyclic flexure and torsion. The second one addressed wall UWS1, which was tested dynamically on a shake table. The author’s modelling approach as well as comparisons between experimental and numerical results are presented. Overall good agreement was obtained for UW1 and UW2 specimens in terms of maximum load, hysteretic pinching and post-peak response. For UWS1 both prediction and postdiction results are presented. Comparison with displacements, torsional rotation, maximum inertial forces, tensile strains and residual displacements is provided. Finally, sensitivity analysis of some modelling parameters affecting the response of wall UWS1 is presented.

Two destructive earthquakes on February 6, 2023, in Türkiye, have demonstrated the importance of seismic retrofitting of those structures with weak seismic performance since many reinforced concrete (RC) structures have collapsed or experienced heavy damage. Many structures are seriously damaged in eleven different provinces. According to authorities, almost 250,000 structures suffered severe damage or were destroyed, more than 50,000 people lost their lives, and more than 100,000 people were injured. These two major earthquakes have once again highlighted the need to strengthen RC structures with inadequate seismic performance before or retrofit after earthquakes. Adding a reinforced stucco layer to the masonry infill walls is a preferred, easy-to-apply, cost-effective and less labor-intensive method for strengthening RC frame structures. This study investigates the effect of a masonry infill walls strengthening method for reinforced concrete structural frames and the purpose of the work is to show seismic performance enhancement with the strengthening method. The behavior of three different models is simulated, and seismic performance is observed for classical and strengthened infill walls. Incremental dynamic analysis procedure is applied with earthquake motions from February 6, 2023 events in Türkiye. Earthquake simulation program OpenSees is used for the time history analysis in this study. Results indicate that strengthening infill walls by adding a rebar layer with mortar can enhance buildings’ seismic performance. Also, the seismic collapse probabilities of frames within fifty years are evaluated, and the results of strengthened infill walls are compared with the classical walls. Results indicate that strengthening method can reduce collapse probability of frames in fifty years around 30% depending on structural properties.

This study investigates the relationships among various site-effect proxies collected in the CRISP database (http://crisp.ingv.it/), which archives site characterization data of the Italian National Seismic Network. We analyzed the Horizontal-to-Vertical spectral ratio (HVSR), derived from both earthquake and noise measurements at 320 stations, as a primary indicator of site effects. Our research also explored HVSR’s correlation with topography and site classes, lithology, and magnitude residuals. This extensive dataset allowed us to group the HVSR curves into four distinct clusters based on their shapes, facilitating detailed comparisons between earthquake- and noise-derived estimates. The analysis revealed that: (i) approximately half of the permanent stations exhibit significant amplification, with amplitudes exceeding 2; (ii) although HVSR from noise generally mirrored that from earthquakes, it often showed lower or equal amplitudes of the curves but higher amplitude of resonance frequency, likely due to different wavefield compositions. The correlation between HVSR and other proxies displayed a weak but statistically significant dependence on lithology, site classes and magnitude residuals. Specifically, as soil characteristics degrade, the resonance frequency decreases, and its amplitude slightly increases. Furthermore, local magnitude tends to be overestimated at sites exhibiting HVSR amplification at frequencies below 2–3 Hz. No correlation was found with topographic classes. A significant challenge in clearly distinguishing HVSR behavior among soil categories, as defined by current building codes, arises from the considerable standard deviation observed. Nevertheless, our findings suggest that integrating seismological data, including HVSR curves, fundamental frequency, and amplitude, can substantially optimize soil class definitions within the updated Eurocode 8 framework.

This article presents a revision of empirical ground-motion models (GMMs) for the horizontal components of 5%-damped pseudo-spectral acceleration, peak ground acceleration, peak ground velocity, cumulative absolute velocity, and Arias intensity that were originally developed by the first two authors as part of the NGA-West2 Program. The GMMs were refit using fixed-effects (i.e., no random effects) and mixed-effects regression analyses that include either (1) events as a random or repeatable effect or (2) both events and sites as random or repeatable effects. True estimates of the variance components were obtained using Bayesian inference that incorporates uncertainty in the random effects and within-group errors (i.e., the residuals). As a result, the aleatory standard deviations are larger than those calculated directly from the residuals that ignore this uncertainty. Goodness-of-fit metrics show that the GMMs were improved by adding events as a random effect and improved even further by adding sites as a random effect. We found the variance components other than the between-site standard deviation to be magnitude dependent. We recommend use of the GMM that includes both events and sites as random effects because of its appropriate modeling of repeatable effects and its superior goodness-of-fit metrics.

With the growing use of precast concrete structures in construction, the reliability-based design (RBD) of bending capabilities of precast reinforced concrete (RC) and prestressed reinforced concrete (PRC) beams has become increasingly important. Traditional RBD methods, such as the partial safety factor design (PSFD), suffer from limited precast beam data for calibration and fail to consider the impact of different failure modes on flexural capacity. This oversight can lead to an unreliable estimated flexural design capacity. Hence, a robust RBD approach must account for the unique features of precast beams, including limited sample sizes and failure modes. In this study, a probabilistic failure mode-based design model for evaluating the flexural capacities of precast RC/PRC beams was developed and integrated with the probabilistic confidence-based estimation (PCBE) RBD method, which is suitable for small samples. This combined approach enables reliable estimation of flexural design capacities of precast RC/PRC beams. The proposed resistance design model was validated against the maximum bending moments of 74 RC and 69 PRC beams. Comparative analysis indicates that the predicted flexural capacities align well with experimental results. Furthermore, the validity of the combined method was verified using collected test datasets of RC/PRC beams, and partial safety factors corresponding to different failure modes were provided. The proposed method offers a practical approach for conducting effective reliability analysis of precast RC structures.