•A practical methodology is presented to assess the seismic resilience of corroded RC frame structures under mainshock-aftershock sequences.•An economic loss ratio is introduced in a piecewise ...resilience function to determine the threshold of the replacement strategy of the damaged structure.•A comprehensive analysis of seismic fragility and resilience is conducted for corroded RC frame structures subjected to mainshock-aftershocks sequences.•The coupling and individual effects of corrosion and aftershock on structural fragility and resilience are examined and compared.
Numerous existing structures exposed to an aggressive environment would also face to a threat from potential strong earthquakes. The coupling effect of environmental aggression and earthquakes could significantly increase the structural damage and failure probabilities of aging buildings. This paper presents a practical methodology of seismic resilience assessment for the corroded reinforced concrete (RC) buildings under mainshock-aftershocks. In this methodology, a piecewise resilience function is introduced, and the structural resilience will drop to zero when performing replacement. An economic loss ratio is adopted to determine the boundary point in the piecewise resilience function. Moreover, a vector-valued approach is employed to evaluate the structural fragility under mainshock-aftershock sequences. To illustrate the proposed methodology, a RC frame building designed according to Chinese codes is used as an example, and four cases with no, low, moderate, and high degrees of corrosion damage are considered with the corrosion rates (ηs) of 0%, 5%, 10% and 15%, respectively. A set of 662 real mainshock-aftershock sequences are selected as the input ground motions from PEER database. The resilience curves are then developed for the uncorroded and corroded RC frame cases under mainshocks alone and mainshock-aftershock sequences. The results show that the coupling effect due to both corrosion and aftershocks lead to a more significant reduction on the structural resilience (ΔR) than the individual effect due to either corrosion or aftershocks. For the condition of ηs = 15% and the PGV of aftershock equals to 0.1 m/s, it is found that there is a 95% of increase on the ΔR due to the coupling effect which is larger than either aftershock (31.6%) or corrosion alone (70%). Moreover, the reduction scale of the structural resilience due to both factors is even larger than the summation of those due to any individual factor alone. The results of this study highlight the importance to consider the two scenarios of aging and aftershocks simultaneously when evaluating the seismic resilience of structures in the lifespan.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The estimation of building seismic risk and loss utilising response history analysis is challenging, especially because the final objective is the seismic loss estimation for building stock. In this ...paper, this challenge is addressed by developing a simplified nonlinear structural model, which is capable of simulating the seismic response of predominantly plan‐symmetrical reinforced concrete frame buildings subjected to ground motions in both horizontal directions. The simplified structural model is plugged into the direct seismic risk and loss estimation methodology. Its capabilities are then demonstrated by estimating the seismic risk and losses for a four‐storey office building and a five‐storey school building. For the analysed buildings, it is shown that the frequency of collapse, the expected annual loss and the frequency of exceedance of a given loss can be simulated with the same level of accuracy as in the case of the conventional structural model, but with greater numerical robustness and computational efficiency. Research is needed to better define the limitations of the introduced simplified model and extend the capabilities of simplified nonlinear models to more complex structural systems of plan‐asymmetrical buildings.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Numerous aging structures are currently confronted with a seismic crisis due to successive earthquakes. Previous mainshock damage and material deterioration significantly impact the capacity of ...structures to resist future aftershocks. Conducting resilience analyses, taking into account the current damage state, is crucial to assess the safety of these buildings. In this paper, an analytical methodology is presented for deriving state-dependent resilience curves while considering the coupling effect of corrosion and aftershock. This methodology reforms the structural functionality and introduces a state-dependent resilience function conditional on the mainshock damage state. The aftershock damage data is grouped by the structural response under mainshocks. Then, the state-dependent aftershock fragility and seismic resilience are generated based on the grouped dataset. To demonstrate the proposed methodology, a case study is conducted on a seismic-designed reinforced concrete frame building with varying degrees of corrosion damage. Results show that the proposed methodology effectively evaluates the resilience levels of buildings, considering various mainshock damage states. The mainshock damage significantly influences the aftershock resilience results. A severe mainshock damage can cause a 34 % reduction in seismic resilience compared to an undamaged structure. Furthermore, the reduction in structural resilience caused by the combination of corrosion and aftershock exceeds the sum of the reductions caused by the individual effects of each factor. The findings of this study also emphasize the importance of considering the scenarios involving corrosion and aftershocks when assessing the resilience of structures throughout their service life.
•A practical methodology is presented to assess the state-dependent aftershock resilience of corroded RC frame structures.•A reformed structural functionality formula is introduced to develop a state-dependent resilience function.•A comprehensive analysis of aftershock resilience is performed for corroded RC frame structures.•The effects of mainshock damage, corrosion, and aftershock on seismic resilience are examined and compared.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Geri kazanılmış agrega kullanılarak üretilen betonun (sürdürülebilir beton) yeni inşa edilecek betonarme
çerçeve veya perde + çerçeve olarak projelendirilmiş binalarda dikkate alınmasını inceleyen bu ...çalışmada,
geleneksel beton ve sürdürülebilir betondan elde edilen binaların şekildeğiştirme temeline dayalı performans
değerlendirmesi yapılmıştır. Çalışma kapsamında %30 oranında geri kazanılmış agrega içeren sürdürülebilir
beton ve C30/37 dayanım sınıfına sahip geleneksel beton kullanılarak üretildiği kabul edilen 8 katlı ve 5
açıklıklı yapılar Türkiye Bina Deprem Yönetmeliği’ne (TBDY 2018) göre doğrusal olmayan statik itme
analizi yöntemi ile analiz edilmiştir. Yapılan analizler sonucunda taşıyıcı sistem elemanlarında kat
seviyelerinde oluşan kesme kuvvetleri ve katlar arası göreli ötelenme değerleri belirlenmiştir. Sürdürülebilir
betondan elde edilen yapıların geleneksel betonlu yapılar gibi deprem etkilerine karşı gereken performansı
sağladığı görülmüştür. Ayrıca sürdürülebilir betonun geleneksel betona göre daha elastik bir davranışa sahip
olması nedeni ile Türkiye Bina Deprem Yönetmeliğinde yapıların üretildiği beton malzeme farklılığının
dikkate alınarak, yapının özellikle geri dönüşümlü beton kullanılarak inşa edildiği durumlarda, daha elastik
olarak tasarlanması gerektiği önerilmektedir.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
AbstractThe paper deals with the dynamic characterization of a reinforced concrete (RC) frame school building in central Italy before and after the seismic retrofitting, obtained by coupling the ...building with an innovative patented seismic dissipative protection system. Before the retrofit, ambient vibration tests were performed to evaluate frequencies and mode shapes for developing finite-element (f.e.) models describing the school dynamic behavior in operational conditions. Several finite-element models with increasing level of detail are presented, from the bare frame model, based on the assumptions and simplifications usually adopted for design purposes, to an upgraded model taking account of secondary and nonstructural elements (e.g., internal and external walls, screeds, roofing, floor tiles, and plasters) as well as the interaction between structure and retaining walls. The latter was used to develop the design model of the seismic retrofitting system, which aims to assure the immediate occupancy of the building in the case of severe earthquakes limiting damage to nonstructural components. Tests were repeated after the retrofit to check consistency with numerical design predictions. Comparisons between experimental and numerical modal parameters are shown discussing the usefulness of ambient vibration tests.
► We analyse the performance of a RC frame building under sudden column removal. ► Linear static, linear dynamic and nonlinear dynamic analyses were performed. ► All approaches indicate no ...progressive collapse although plastic hinges were formed.
The problem of structural progressive collapse has been investigated using a real-scale reinforced concrete flat-slab frame building, which has survived collapse after two of its central columns had been physically destroyed. The numerical study undertaken considers three loading scenarios, in which alternately three different columns are being instantaneously removed, and in each case the structural response of the frame is calculated. A finite-element linear static analysis has first been conducted. To account for severe dynamic effects occurring during fast dynamic events, such as explosions or impacts, dynamic linear and nonlinear time history analyses have next been performed. For each scenario the results have been processed in terms of demand-resistance ratios at critical cross-sections, and thus it has been assessed whether the building would be susceptible to progressive collapse according to certain allowance criteria prescribed in technical guidelines. In this respect, three definitions of dynamic factors are introduced and their effective applicability is assessed in view of actually calculated and guidelines-suggested values. Results show overall that the approaches of linear static and dynamic analyses would have produced progressive collapse conditions. The nonlinear dynamic analysis predicts no mechanism which might lead to progressive collapse, even though several plastic hinges would be formed. Merits of using static or dynamic, linear or nonlinear analyses are discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
AbstractNonductile reinforced concrete (RC) frame buildings were found to be vulnerable to earthquakes. Thus retrofitting of these buildings is necessary, as addressed in the recent retrofit program ...of Los Angeles. A potential retrofit strategy is base isolation, which has many advantages but is not yet routinely used in the United States because of its high cost. To determine whether base isolation is economical when the advantages and costs are compared, seismic performance assessment and cost-benefit analysis are performed on two nonductile RC frame buildings before and after being numerically retrofitted with base isolation, which makes consideration of uncertainties. Location of the buildings is assumed to be Los Angeles, CA. Aftershock ground motions are generated to examine the influence of aftershock hazard. Direct loss, downtime, fatalities, and total loss for each of the buildings are investigated. Results suggest that base isolation can reduce the seismic loss, downtime, and fatalities effectively. Besides, the benefits can outweigh the retrofit costs. The effect on the results caused by indirect losses from downtime and fatalities is quantified and shown to be substantial. Aftershock hazard is also found to be at a relatively significant level.
Robust seismic vulnerability assessment for a building under expected earthquake ground motions necessitates explicit consideration of all-important sources of uncertainty in structural model ...idealization. This paper presents a machine learning-based methodology for reliably predicting the seismic response and structural collapse classification of ductile reinforced concrete frame buildings under future earthquake events by accounting for component- and system-level modeling uncertainties. The proposed methodology uses two different types of machine learning methods—regression-based and classification-based methods—to achieve the goal of this study. Machine learning techniques with boosting algorithms (i.e., adaptive boosting and extreme gradient boosting) are the best methods for both response prediction and collapse status classification of modern code-compliant reinforced concrete frame buildings. Finally, the effect of uncertain modeling parameters on the response and collapse identification is examined. The reinforced concrete beam modeling-related parameters (i.e., plastic deformation properties) of ductile, low-to mid-rise frame buildings are significant predictors of seismic response due to capacity design principles.
•Propose the data-driven approaches for structural collapse risk of a building.•Utilize the regression-based machine learning techniques to infer the damage state of a building.•Identify the optimal machine learning-based procedure for collapse status classi_cation.•Quantify the e_ect of uncertain modeling parameters on the response and collapse identi_cation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The susceptibility of concrete beam-column joints in reinforced concrete (RC) frame structures to progressive collapse can result in severe damage or collapse. High-performance fiber-reinforced ...cementitious composites (HPFRCCs), as a strain-hardening material, can be used instead of ordinary concrete to improve RC frame buildings' performance. This study evaluates the effects of using HPFRCC in beam-column joints on the behavior of RC frame structures subjected to progressive collapse. Five RC buildings with moment-resisting frame systems were studied for this purpose, one with ordinary concrete beam-column joints and the others with HPFRCC beam-column joints and varying quantities of reinforcement on beams and columns. The buildings were evaluated using 3D modeling with OpenSees finite element software and removing a corner column using the alternative load path method (ALP) per GSA regulations. The results show that using HPFRCC in beam-column joints can improve the robustness of RC frame buildings to progressive collapse by increasing beam-column joint stiffness, load-bearing capacity, and the ability to withstand large deformations. Furthermore, damages caused by the sudden removal of corner columns in buildings reveal that the use of HPFRCC in beam-column joints results in a reduction in damages, even in buildings with a reduced quantity of reinforcements (buildings H1 and H2), even though a significant decrease in the number of longitudinal reinforcements of beams and columns in the building with HPFRCC beam-column joints (building H3) can result in severe damage to the connections.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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