Seismic Performance Levels Research Articles

Evaluation of deformation-based seismic performance of RECC frames based on IDA method

Engineered Cementitious Composites (ECC) is a typical High Performance Fiber Reinforced Cement-based Composite (HPFRCC), which possesses the characteristics of ultra-high tensile ductility and energy dissipation capacity. One of the potential applications of ECC is to replace conventional concrete in the seismic resistant structures. However, to date, the investigation on seismic performance of ECC at the structural level is still limited. This paper aims at evaluating the seismic performance of RECC frame on the basis of Performance-based Seismic Design (PBSD) concept and discussing the feasibility and practicability of applying ECC in structures for improving the seismic performance. The non-linear behavior of ECC material was simulated especially considering the strain hardening behavior in tension. By using the Incremental Dynamic Analysis (IDA) method, three types of frames, consisting of a normal RC frame, a RECC frame and an RECC/RC composite frame, were analyzed to evaluate the structural dynamic behavior of the frames. Comparative studies on the deformation limit states at five levels of seismic performance for these three different types of frames validated that RECC frames have superior deformation capacity comparing to traditional RC frames under high intensity earthquake. Comparison results also indicated that rationally applying ECC in key region of the structures can not only improve the seismic performance and deformation capacity of structures but also control the construction cost.

Preliminary assessment approach to predict seismic vulnerability of existing low and mid-rise RC buildings

This article presents an approach to rapidly predict the seismic vulnerability existing of low-to mid-rise residential reinforced concrete (RC) buildings. In this procedure, Capacity Index is computed considering the cross-sectional orientation and size and material properties of the components of the structural system. This index is modified considering the several coefficients of possible negative impacts of structural irregularities, which are frequently found in RC buildings. Accuracy of the proposed approach has been tested considering 196 RC buildings subjected to earthquakes. The procedure categorizes the buildings either as safe or as unsafe according to whether they meet the life-safety target performance requirement. The analytical results indicate that the consistency of the proposed approach in this paper is about over 90%. Therefore, the proposed approach can be used to asses the seismic performance and vulnerability levels of existing RC buildings.

Experimental and analytical studies of sub-standard RC frames retrofitted with buckling-restrained braces and steel frames

Existing reinforced concrete (RC) buildings designed according to outdated codes may lack sufficient strength, stiffness or ductility to meet the seismic performance criteria of current codes. To enhance the system stiffness and re-centering capability, an elastically designed supplementary steel frame (SF) is installed in parallel with the BRBs. Near full-scale cyclic tests are conducted on such retrofit schemes for performance evaluation. The retrofitted specimens showed stable hysteretic behavior up to the retrofit target story drift of 1/150 as proposed in the Japanese seismic regulations. Tests demonstrate that the proposed system is feasible and increases both strength, ductility, and damping to an adequate seismic performance level while the elastic steel frame is effective in providing post-yield stiffness and re-centering capability even when the RC frame is subjected to moderate inelasticity. Special emphasis is placed on the composite behavior of RC members and SF. A simplified composite interaction model is proposed and results from the developed model show good agreement with the experimental data. Ductility demands are shown to concentrate in the BRBs as per the design intent.

Quantitative Definition of Seismic Performance Levels for Precast Bridge Piers with Continuous Reinforcement

For construction sites within cities, which require fast construction because of restrictions in road occupation time, or for other occasions where construction period is an important factor because of similar reasons, application of a modular construction method using precast members is efficient in terms of shortening the construction period. The substructures of bridges are normally constructed using cast‐in‐place, which has been a major cause of delays in construction. Application of a modular construction method could decrease the occupation time in the sites. A prime example is the Accelerated Bridge Construction (ABC) by the Texas Department of Transportation (TDOT) and Federal Highway Administration (FHWA). Precast members are the key components of ABC. The main purpose of this paper is to provide clear seismic performance standards for precast bridge piers. Current seismic design codes require force‐based design checks and provide qualitative evaluation of the overall structure. They do not provide specific qualitative criteria for individual structures with particular types. Previous research has been focused on reinforced‐concrete bridge piers, while lacking on research towards prefabricated bridge piers with continuous reinforcements. In order to quantitatively evaluate the seismic performance level of prefabricated bridge piers, the seismic performance was quantitatively suggested in accordance with the classification of four which are operational, immediate occupancy, life safety, and collapse prevention. These criteria are cracking of cover concrete, crushing of cover concrete, yielding of axial steels, and fracture of axial steels. Based on the given seismic performance evaluation criteria, evaluation and verification were conducted on four prefabricated bridge piers with continuous reinforcement that have undergone quasistatic cyclic experiments. The moment‐curvature analysis model was constructed for the parametric study and verified through experimental results. Based on the developed M‐Phi model, prefabricated bridge piers with continuous reinforcement, which were designed force‐based using response correction factor, were evaluated. In addition, parametric study was also conducted focusing on concrete strength, magnitude of prestress, and transverse reinforcement. Depending on the level of individual performance produced by ranges of these variables within possible runs on actual piers, the impact of 3 variables was analyzed. Furthermore, in response to changes in each variable, the impact on the relevant seismic performance level was verified through response spectrum analysis.

Eşdeğer Deprem Yükü Yöntemi Kullanılarak Tarihi Bir Yığma Yapının Sismik Performans Düzeyinin Belirlenmesi

Tarih boyunca Anadolu toprakları, birçok medeniyete ev sahipliği yapmıştır. Bu sebeple ülkemizde tarihi yapılar azımsanmayacak sayıdadır. Bununla birlikte ülkemizin, aktif deprem kuşağı içerisinde yer alması sebebiyle birçok tarihi yapı, meydana gelen depremlerden zarar görmüş veya yıkılmıştır. Kültür mirası açısından önem arz eden tarihi yapılarımızın, gelecek kuşaklara güvenle aktarılabilmesi için sismik performans seviyelerinin doğru ve hızlı bir şekilde belirlenerek gerekli müdahalelerin yapılması oldukça önemlidir. Çalışma kapsamında örnek olarak ele alınan Tarihi Yanıkoğlu Camisinde yapılan ölçümler ve gözlemlere dayalı olarak yapının analitik modeli oluşturulmuştur. Yapı konumuna özel olarak seçilen deprem spektrumları ile eşdeğer deprem yükü hesaplanmıştır. Yapının kendi ağırlığı ve hesaplanan deprem kuvvetleri altında yapılan analizlerden elde edilen sonuçlara bağlı olarak yapının sismik performans düzeyi 2017 yılında Vakıflar Genel Müdürlüğünce yayımlanan Tarihi Yapılar İçin Deprem Risklerinin Yönetimi Kılavuzuna göre belirlenmiştir. Bu çalışma ile tarihi yığma yapıların sismik performanslarının değerlendirilmesinde eşdeğer deprem yükü yöntemi kullanılarak pratik bir yaklaşım ortaya konulmuştur.

Using concentric and zipper steel braces by comparison of effect on improved seismic performance level of concrete moment frame structures with moderate ductility

Recent earthquakes have revealed that, in many cases, the design codes may not guarantee the integrity of all structures for the life safety performance level. Therefore, it seems necessary to study the performance of designed buildings in order to complete, develop and amend the codes. In this paper, the performance level was investigated using the nonlinear static analysis in concrete buildings with moderate ductility and designed according to the latest regulations. Then, as the life safety performance level was not achieved and due to the ease of implementation of steel braces, the concentric chevron brace was used to improve the performance level of these buildings in large bays, and the zipper steel brace was used. The results show that the zipper brace used for strengthening the reinforced concrete structures will increase the performance as well as the stiffness, without the need to strengthen the beams and columns.

Prediction of Seismic Performance Levels of Corroded Reinforced Concrete Columns as a Function of Crack Width

Abstract An experimental study was conducted for the prediction of the seismic performance levels of corroded reinforced concrete (RC) columns as a function of the initial corrosion crack widths. A full-scale accelerated-corrosion pool was used to corrode 25 full-scale RC columns. The initial crack widths at different levels of corrosion were measured for three different concrete strength levels: 9, 27, and 37 MPa. The seismic performance levels of corroded RC columns under combined cyclic lateral-displacement excursions at two different axial-load ratios (0.20 and 0.40) were measured. The corrosion levels obtained for the initially measured corrosion crack widths were used for establishing a correlation with the lateral-displacement capacities of the RC columns according to an energy-based method. Three empirical models were developed. The first was for predicting the cross-sectional area reduction of reinforcement bars according to the initial corrosion crack widths. The second model was for predicting the percentage of energy capacity of RC columns as a function of the drift ratio and corrosion levels. The third model was for predicting the seismic performance levels of RC columns as a function of the initial corrosion crack widths and was used for an in situ structural assessment. The experimental test results showed that above a 2% drift ratio, all uncorroded RC columns (regardless of the concrete strength levels) exhibited a sudden reduction in energy capacity, and their total energy capacity was consumed. In the case of corrosion, the energy capacity of concrete with high strength levels was prematurely exhausted above a 1.4% drift ratio because of the effects of the corrosion products under the high strength levels of the concrete.

Effects of openings on the seismic behavior and performance level of concrete shear walls

Effects of openings on the seismic behavior and performance level of concrete shear walls

Applications of hysteretic steel dampers for controlling the seismic damage in steel frames

The aim of seismic design is not intended to make earthquake-proof structures that will not experience any damage even during a strong earthquake; such structures will be too costly. However, controlling the damage to the desired level is a necessity for buildings with a particular purpose such as hospital, fire and police station, nuclear facilities, buildings that contain hazardous material, and other building that is critical for emergencies and defense. In this paper, a four-story steel frame, both with and without hysteretic steel damper are investigated in order to account the effect of stiffness ratio, and SR (ratio between steel damper and braces stiffness to the bare frame stiffness) in the global structural damage. For these purposes, three ground motions which are compatible to the design spectrum response in the Indonesian building code were selected to be applied to the structure with a stiffness ratio (SR) of 2, 3, 4 and 5 using a non-linear dynamic time history analysis. In this context, the damage index based on the works of Park and Ang is used as the criteria to define global structural damage, while story drift index is used as the criteria to measure the seismic performance level. The results demonstrated that the use of steel damper not only enhances the seismic performance, but it also reduces the damage index of the investigated structure. Furthermore, the damage index and story drift index are influenced by the stiffness ratio, in which the stiffness ratio of 4 (four) provides the smallest damage index and inter-story drift index. Moreover, the damage index and inter-story drift index were also affected by ground motions characteristics.

Quantifying local seismic amplification from regional charts and site specific numerical analyses: a case study

Three levels of seismic microzonation are considered in the Italian guidelines: 1st level allows to qualitatively recognise those areas characterised by the same seismic performance, while 2nd and 3rd levels quantify the modification of the reference signal due to the specific site conditions. The paper summarises and compares the results of 2nd and 3rd level seismic microzonation studies for the Dovadola urban area (Emilia-Romagna, Italy). The site was selected due to the availability of in situ and laboratory investigations for the definition of a detailed geotechnical seismic model of the subsoil. The 2nd level study was conducted adopting the regional charts for the quantification of the stratigraphic amplification phenomena and the regional procedures for assessing the influence of topography. The 3rd level analysis was developed through mono- and two-dimensional seismic site response analyses adopting a numerical non-linear approach. Amplification factors for the peak ground acceleration and for the velocity spectrum intensity (i.e. the integral of the pseudo-spectral velocity of a ground motion from 0.1–0.5 to 0.5–0.1 s) were determined along two geotechnical sections of the site, both characterised by a central large and surficial valley bordered by irregular topography. The study indicates a general satisfactory match between the results of the simplified regional approach and the advanced numerical tool, especially when one-dimensional seismic site conditions prevail. Further comparative studies are encouraged to validate the 2nd level microzonation as a reliable tool for seismic risk mitigation.

Seismic performance assessment of plain concrete arch bridges under near-field earthquakes using incremental dynamic analysis

In the railway network of Iran, a large number of masonry arch bridges exist which most of them was constructed 80 years ago. Despite these types of bridges have shown an appropriate behavior under the influence of gravity (vertical) loads, they have not been designed seismically. Concerning to the seismic hazard zoning map of Iran, most of these railway infrastructures are placed in the very high seismicity zones and constructed near the major faults. So the seismic assessment of these types of bridges has become a significant subject for the engineers to explain the failure and seismic performance levels of these structures. Thus, they can be rehabilitated or removed if it is found required. Among various methods for seismic estimation of the capacity of the structures under seismic loading, the non-linear dynamic method or the incremental dynamic analysis (IDA) may be mentioned as the most precise and complete method for near-field excitations. For this purpose, by selecting 28 near-field earthquake records, this study has seismically surveyed two railway masonry arch bridges, which are respectively placed in the kilometers 23 (2L20 bridge) and 24 (5L06 bridge) of the old railway of Tehran-Qom. The macro-modeling approach was used in the finite element method. In total, 316 non-linear dynamic analyses have been carried out for the seismic assessment of the masonry arch bridges under near-field ground motion. The results found from the IDA analysis specified that the near-field seismic performance of the masonry arch bridge with lower span length (i.e., 5L06 bridge) is safer than the bridge with longer span length (i.e., 2L20 bridge). Mostly, it has to decide to retrofit the masonry bridge with longer span length to improve their performance since the seismic behavior of those has been found inappropriate under near-field earthquakes.

Seismic Performance Levels of a Large Underground Subway Station in Different Soil Foundations

ABSTRACT With the soil constitutive model developed for the dynamic large deformation of soft soil, a finite element model was constructed to simulate the soil–underground structure static and dynamic coupling interaction system, in which the dynamic contact between soil and underground structure and the dynamic damage of reinforced concrete were considered. The seismic performance and damage mechanism of the large underground subway station in different soil foundations were investigated and evaluated in detail. It was proven that the interaction mechanism between the soil and underground structure would change with the type of soil foundation and the peak acceleration of input ground motion, which can be evaluated by the interaction coefficient between the soils and underground structure. At the same time, some regulations on the seismic performance of underground structure in China code are already unsuitable for evaluating the seismic performance of a large underground subway station in the soft soil foundation or subjected to a strong earthquake, which should be investigate by the specialized time–history analysis method instead. In this study, five seismic performance levels were firstly defined by the inter-storey drift angle of underground structure and corresponding earthquake damage states.

Effect of Partition Weight on the Seismic Performance of Reinforced Concrete Frame Buildings

Reinforced concrete frame (RCF) buildings are widely used around the world and they are present in most urban areas. This situation has occurred because they are cost-efficient, have good seismic performance and because the materials and technologies required for their construction are available in many countries. One of the decisions during the design stage of new buildings based on this structural system is selecting the type of partitions. So far, in most developing countries the use of masonry brick walls to separate habitational spaces is still the predominant choice for most new projects. This situation stems from the fact that the selection of partition elements is often motivated by architectural, economic and cultural reasons, and because there is lack of information about the potential impact of the weight of partition elements on the seismic performance. This paper presents the evaluation of the effect of the partition weight on the seismic performance of RCF buildings. For this purpose, a six-story building was designed considering three different types of partitions: a) drywall, b) expanded-reinforced polystyrene and c) traditional clay partitions. Each building design was modelled in three-dimensions using fiber elements and subjected to nonlinear analyses. Based on these results, fragility curves were calculated for different seismic performance levels. The results of these evaluations show that seismic performance improves when lighter partitions are used, particularly in the nonlinear range. These buildings showed higher performance at the life-safety and collapse levels. All things considered, the results of this research show that the weight of partitions has a notable impact in seismic performance, and it suggests that it should be given careful consideration to its choice during the design phase of a project, and that cities planners should promote the use of lightweight partitions for new buildings.

Evaluasi Kinerja Seismik Rangka Beton Pemikul Momen Khusus dengan PERFORM-3D

Seismic performance of reinforced concrete frame Buildings which have been designed as Special Moment Resisting Frames in accordance to three Indonesian codes (SNI 1727-2013, SNI 1726-2012 and SNI 2847-2013) can be evaluated using nonlinear dynamic analysis. Criteria related to strength such as component plastic rotation capacity, lateral displacement as well as criteria related to damage of elements in the structures were used to evaluate the seismic performance of the buildings. Assessment to the moment and curvature capacities of the cross sections of beams and columns were done using XTRACT. The global seismic performance of the structures depends on the seismic performance of components in the structures. In nonlinear model of the structures, the degrading strength of the components were modeled to take into account the gradual reduction of the contributed components to the resistance of the structures. PERFORM-3D is one of the software that can be used to generate nonlinear model of structures. Seismic performance level of structures can be obtained from the results of the nonlinear dynamic analysis using PERFORM-3D. The Seismic performance level can be utilized for: (1) detecting any weaker part in the structures, and (2) evaluating the improved design of the structures for enhancing the seismic performance of structures.

A new method for the evaluation of the ultimate seismic capacity of rectangular underground structures

The ultimate seismic capacity of underground structures should be known to provide a sufficient seismic resistance during the seismic design, due to the irreparable and difficulty of reconstruction after collapsed. However, existing single-factor evaluation methods, including inter-story drift ratio, stress, strain, etc., only present the serviceability seismic capacity and cannot reflect the seismic damage mechanism of underground structures. This paper proposes a performance-based evaluation method to assess the ultimate seismic capacity of rectangular underground structures by considering both the characteristics of the structure itself and earthquake loadings. Ultimate horizontal deformation capacity envelope and failure ratio, derived from the seismic collapse mechanism of rectangular underground structures, are the key assessment parameters of the ultimate seismic capacity. Because the horizontal deformation capacity of the underground structures affected by the vertical loads was taken into account, the obtained ultimate seismic capacity is a band range and expressed with the PGA of earthquakes. The detailed procedure of the evaluation method is demonstrated step by step. Afterwards, a case study is presented to evaluate the ultimate seismic capacity of Daikai station influenced by the spectral characteristics and duration of earthquakes. The predominant periods of earthquakes which the structure might be sensitive to are discussed. The proposed method provides a detailed understanding of the performance-based seismic evaluation of rectangular underground structures and can be extended to characterize other seismic performance levels of the rectangular underground structures in the future work.

An investigation into the effect of soil-foundation interaction on the seismic performance of tunnel-form buildings

Great weight and stiffness can potentially intensify the forces induced to the tunnel-form buildings during seismic events. To overcome the adverse effects of these two parameters on the seismic reliability of buildings benefitting from this structural system, it appears critically essential to account for the soil-structure interaction (SSI) in the modeling process. Accordingly, this paper aims to assess the level of seismic performance as well as the safety condition of buildings against sliding and overturning phenomena. For this purpose, the soil underlying two tunnel-form buildings with 5 and 10 stories was modeled using the linear springs and then, the analysis results were captured for two cases of rigid and flexible base. Based on the results, as the building height and earthquake intensity increases, the SSI effects on the structural responses such as the shear forces and storey drifts and location of damage initiation became profounder. Comparatively, probability of reaching the primary damage levels along with sliding and overturning increased by at least 30 and 10%, respectively in the case of flexible base. In sum, it is concluded that in seismically active areas formed by soft soil, the SSI effect can hinder tall buildings from achieving the predefined performances.

Structural rehabilitation of a middle byzantine ruin and the masonry building constructed above the ruin. Part II: The building

The objective of this study, which consists of a pair of articles, is the structural rehabilitation of a vaulted ruin located on the historical peninsula of Istanbul, dated to the Middle Byzantine period, and a masonry building constructed at a later date on top of the structure. The first article, which constitutes the first part of the study, examined the seismic performances of the historical ruin considering the states; (i) before the construction of the masonry building, (ii) after the construction of the masonry building and (iii) after the strengthening of the masonry building. The present article, which constitutes the second part of the study, presents the seismic assessment of the masonry building's current state located on the historical ruin and a strengthening method proposed for the building in order to achieve its target seismic performance level. Fieldwork and numerical analyses were conducted to this end. The effectiveness of the proposed method is revealed by modal analysis, pushover analysis and kinematic limit analysis in order to determine the global & local failure mechanisms and the seismic performance levels of the current and strengthened states of the masonry building. The findings of the study are significant in terms demonstrating the interaction between historical ruins and buildings constructed above them, and in defining the necessary strengthening applications required to achieve seismic safety in such structures. In addition, by adopting a holistic approach to the structural analysis and strengthening proposal, it is expected to serve as an important tool for the preservation of ruins dated to the Middle Byzantine period.

Earthquake loss assessment of steel moment-resisting frames designed according to Eurocode 8

Current design and assessment guidelines define several seismic performance levels, aiming to ensure that structures exhibit adequate behaviour at different seismic intensity levels. Typically, the acceptance criteria at different performance levels are met by ensuring that local deformation demands are lower than pre-defined capacities. Despite the proven effectiveness of such an approach, it provides an ambiguous measure of the performance of the building, which, in most cases, is neither meaningful nor appropriate for building owners, stakeholders or decision-makers. The main objective of the research presented in this paper is to evaluate the expected direct economic seismic losses of steel moment-resisting frame structures designed according to Eurocode 8 (EC8). A set of 120 archetype buildings, representative of the current building stock in Portugal, were designed according to Part 1 of EC8 using three different behaviour factors, q: a) code-prescribed upper bound limits for medium and high ductility classes; b) behaviour factor defined according to an Improved Force-Based Design (IFBD) procedure. The PEER-PBEE methodology with the improvements proposed by Ramirez and Miranda [1] was employed for the estimation of expected seismic losses evaluated for the seismic intensity levels considered in Part 3 of EC8. The results obtained indicate that the buildings designed in accordance with EC8 comply with the non-collapse criteria. However, the level of damage could imply significant repair costs. Importantly, the results also highlight that a rational selection of the behaviour factor can result in a reduction of steel weight but still ensuring acceptable levels of expected annual losses.

Seismic response mitigation of structures with a friction pendulum inerter system

Introducing a tuned mass damper (TMD) into the friction pendulum system (FPS) has been proven to be an effective approach for improving the seismic performances of base-isolated structures. However, its seismic response mitigation effect is related to the quality of the mass employed, which unavoidably requires a necessary large mass under the requirement of a high seismic performance level. To avoid introducing the extra mass of the tuned mass damper (TMD) in the friction pendulum system (FPS) of a base-isolated structure, we herein introduce a lightweight inerter subsystem that has a series-parallel layout; comprises an inerter, a spring, and a damping element; and adds almost no mass. A structure isolated by the proposed friction pendulum inerter system (FPIS) was studied by nonlinear stochastic response analysis within a probabilistic framework, and an optimal design method for a structure with the FPIS was developed to simultaneously reduce the base shear force and the base isolation floor displacement. Based on the stochastic analysis results, parametric studies and a robustness analysis were conducted, and the impact of the FPIS’s mechanical layout on the seismic response mitigation effect was investigated. The analysis results demonstrated that the FPIS significantly reduced structural responses under different types of seismic excitations. Using the proposed optimal design method, target base shear force can be achieved at a minimized cost to the base isolation floor displacement. Compared to the FPS system with a TMD, the proposed FPIS enhances the seismic response mitigation effect by avoiding the extra mass that increases the seismic energy input to the base isolation floor.

Time-dependent Seismic Performance Assessment of Corroded Reinforced Concrete Frames

In this study, effects of reinforcement corrosion such as reinforcement cross section reduction, steel yield strength and concrete compressive strength reduction on RC member capacity decrease are studied. Next, a two-dimensional reinforced concrete moment resistant frame is modeled to evaluate the effects of moderate and severe intensity corrosion on moment-curvature behavior of elements and structure seismic response under nonlinear analysis. Structure capacity curves in push-over analysis and failure curves resulted from IDA for both the structure without and with corrosion are obtained and the effects of reinforcement’s corrosion on the reinforced concrete frame seismic performance are determined through comparing the results. The results revealed that in terms of amount, place and type of corrosion in the reinforced concrete frame, value of the reduction resisting moment of elements is different. Furthermore, the outcomes of nonlinear analyses showed that the capacity of structure is reduced and its seismic performance level is changed as a result of corrosion.