In this paper, the seismic performance of existing masonry arch bridges is evaluated by using nonlinear static analysis, as suggested by several modern standards such as UNI ENV 1998-1 2003, OPCM ...3274 2004, and FEMA 440 2005. The use of inelastic pushover analysis and response spectrum approaches becomes more difficult when structures other than the framed ones are investigated. This paper delves into the application of this methodology to masonry arch bridges by presenting two particular case studies. The need for experimental tests in order to calibrate the materials and the dynamic properties of the bridge is highlighted, in order to correctly model the most critical regions of the structure. The choice of the control node in the pushover analysis of masonry arch bridges and its influence on seismic safety evaluation is investigated. The ensuing discussion emphasizes important results, such as the unsuitability of the typical top node of the structure for describing the bridge seismic capacity. Finally, the seismic safety of the two bridges under consideration is verified by presenting an in-depth vulnerability analysis.
The adequacy of the structural performance of a wharf in withstanding seismic loads is of paramount importance. Therefore, this research aims to conduct an accurate pushover analysis on the adequacy ...of a wharf located in North Sulawesi, Indonesia. The study provides a comprehensive overview of the seismic performance of the wharf by examining displacement and strain parameters of its plastic hinge components under various loading conditions. To simulate accidental torsion, the wharf structure was analyzed by introducing variations in the eccentricity offset of the lateral pushover load of -5%, 0%, and 5% from the center of mass. The analysis of the torsion behavior involved a comprehensive examination of four control points located at each corner of the wharf plan. Additionally, the investigation took into account, the crucial aspect of soil-structure interaction by considering the equivalent fixity depth of the pile, which was used to evaluate the fixity length of the structure. In order to determine the target displacement of the wharf, analysis was performed in accordance with the established methodologies outlined in FEMA 356. It is also important to note that the seismic performance of the wharf was evaluated based on acceptance criteria in the form of strain limits imposed on various components, including concrete elements, reinforcing steel, and steel pipes, as prescribed by ASCE 61-14. In this study, a total of 30 models were examined, and the obtained results showed that the structure exhibited controlled and repairable damage even when subjected to a 475-year earthquake return period (CLE: Contingency Level Earthquake). Following this, the analysis of variations in displacement control point served to determine the inherent torsion exhibited by the structure, and the introduction of different lateral load eccentricity offsets and variations in pushover loading direction were found to contribute to the increased displacement and strain in the plastic hinge components.
Destruction of reinforced concrete (RC) structures, particularly non-ductile RC structures, in recent earthquakes demonstrate their vulnerability under lateral forces generated in an earthquake. ...Despite the extensive literature on the subject and the wide variety of strengthening techniques available, there is no consensus on the efficiency of these techniques in improving the seismic performance of RC structures. In this study, a five-storeyed RC-framed building is considered to evaluate its seismic performance through static non-linear pushover analysis. To examine the effect of various cases encountered in practice, the pushover analysis is carried out on the RC frame for various cases, i.e. a bare RC frame, an RC frame with masonry infills but with an open ground storey, and RC frames with shear walls with a variety of thicknesses and steel reinforcement ratios. Further, to investigate the effect of retrofitting, the RC frame is strengthened using local jacketing and bracings. From the results, it is observed that the initial stiffness and base shear of masonry infilled RC frame with an open ground storey exhibit an increase of 2.6%, and 19%, respectively, as compared to the bare frame. The use of shear walls increases the initial stiffness and base shears, and they increase by 6–14% and 8–20%, respectively, with an increase in the reinforcement ratio in the shear wall. Retrofitting with the use of both diagonal bracings causes the base shear to increase by a factor of 7.7 as compared to that of the open ground storey. Finally, the probability of damage to the RC frame in all cases was compared using seismic fragility curves.
•Review of Earthquake Effects on the Reinforced Concrete Structures.•Numerical Modeling of G+5 Reinforced Concrete Structures.•Seismic Interventions to Enhance Performance of RC Structures.•Pushover Analysis on a Variety of RC Frames with Seismic Interventions.•Comparison of results from various Seismic Rehabilitation Techniques.
This study evaluates the seismic performance of the steel frame with self-centering viscous-hysteretic devices (SC-VHD frame) and investigates the effect of design parameters of the SC-VHD, preload, ...loading stiffness, unloading stiffness and viscous damping ratio, on seismic performance through conducting nonlinear static pushover analysis, fragility analysis and risk assessment on 4-, 8-, and 12- story SC-VHD frames with different design parameters. Results indicate that the maximum normalized base shear and the ultimate roof drift ratios of the SC-VHD frames increase by more than 13.3% and 42.9%, respectively, compared with the conventional frames. The SC-VHD frames have acceptable low probabilities of collapse and probabilities exceeding considered residual drift under the maximum considered earthquake (MCE) and during a 50-year period. Accordingly, the most sensitive parameter regarding the probabilities of collapse is loading stiffness, followed sequentially by unloading stiffness, viscous damping ratio and preload. While for the probability exceeding considered residual drift under the MCE, the parameters of ring springs, preload, loading stiffness and unloading stiffness, have a significant effect on the 4- and 8-story SC-VHD frames, and the viscous damping ratio of the viscous damper has the most significant effect on the 12-story SC-VHD frame. For the probability exceeding considered residual drift during a 50-year period, the most sensitive parameter is the viscous damping ratio.
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•Ductility capacity and seismic load-carrying capacity of SC-VHD frames are investigated.•Accuracy and efficiency of different fragility analysis methods are compared.•Collapse risk of SC-VHD frames is assessed.•Risk exceeding considered residual drift of SC-VHD frames is assessed.
•Comparison among different approaches for the seismic vulnerability of masonry aggregates.•Local analyses with a new upper-bound limit analysis based on NURBS and mesh adaptation.•Global pushover ...analyses with the Equivalent Frame Method and 3D FEM with damaging materials.•Nonlinear dynamic analyses on detailed 3D FE mesh with CDP model for masonry.•All approaches confirm the high vulnerability and provide information on collapse modes.
Recent seismic events in Italy have emphasized the high vulnerability of masonry buildings in historical centers, which were generally erected in continuity to each other over time, resulting in aggregates of constructions. The study of the seismic behavior of masonry aggregates can turn into a very difficult task, usually because of the difficulties to achieve a complete knowledge of geometrical evolutions, state of the connections between structural units, and interventions carried out in the course of time. A wide number of local collapses has been observed after recent earthquakes in Italy, highlighting that collapse under horizontal loads may take place mainly through failure mechanisms of single portions of the aggregate. According to Italian Code, both global and local analyses can be adopted in the seismic assessment of single structural units. Therefore, the aim of this study is to investigate different approaches for the evaluation of the seismic vulnerability of historical masonry aggregates. A masonry aggregate located in the historical center of Arsita (Central Italy), which was hit by the 2009 L’Aquila earthquake, has been chosen as a representative case study and a wide set of local and global analyses has been carried out. Local analyses have been conducted through a new upper-bound limit analysis based on NURBS and mesh adaptation, and a kinematic limit analysis applied to the most common local mechanisms. Global analyses have been performed through pushover analyses using the Equivalent Frame Method, and pushover and nonlinear dynamic analyses on a detailed FE model with appropriate constitutive laws. Finally, a discussion about the effectiveness of the different analysis approaches is presented with reference to the results obtained in this study.
Safe design of the structure in earthquake increases the ability to absorb and dissipate energy by the bracing system. Also, one of the new methods to reduce earthquakes is the formation of plastic ...hinges in the flexible members of the structure. By creating plastic hinges in structural, the distribution of forces in other structural members is improved. Therefore, in the current research, using a questionnaire (6 criteria), the opinions of university professors and doctoral students were collected about the most important criteria for evaluating the plastic performance. The data was analyzed and prioritized by hierarchical analysis method in Expert Choice software. The plastic hinge with a statistical weight equal to 0.424 was introduced as the most important plastic criterion. Then, 10 bracing systems of steel structure including diagonal, gate, V, invert V, knee, rhombus, forward concentrically, zipper, cross, concentrically and steel moment frame were modelled with Sap2000 software. Steel frames have 4 and 8 story. The structures were analyzed and finally compared with nonlinear static analysis. The results showed that concentrically braces (4-story) and zipper (8-story) have the greatest ability to create plastic hinges. The use of all bracing systems in the steel frame increased the number and performance level of plastic hinges. Increasing the height of the structure increased the effects of braces on the steel frame.
