The paper discusses the seismic vulnerability of structures susceptible to overcrowding due to their intended use. Specifically, it addresses the analysis towards earthquake actions of a masonry ...school located in the Municipality of San Giorgio a Cremano, within the neighbourhood of Naples, providing different reinforcement interventions to ensure its seismic consolidation. After a brief introduction, the description of the analysis representative of the current condition of the structure is performed considering both static and seismic actions. The analysis results determine the seismic risk class of the building, allowing to identify its deficiencies, so to design structural consolidation interventions following the standard code indications. In particular, two retrofit techniques, namely, FRP and FRCM systems, are proposed with the purpose to evaluate their benefits to the school building from a seismic viewpoint. Finally, a comparison between the proposed intervention techniques is made to establish which one guarantees the best upgrading of the seismic condition of the examined building.
The evaluation of the maximum and cumulative response is an important issue for the seismic design of new base-isolated buildings. This study predicts the maximum and cumulative response of a ...14-story reinforced concrete base-isolated building using a set of pushover analyses. In the proposed pushover analysis method, the maximum and cumulative responses of the first and higher modes are evaluated from the nonlinear analysis of equivalent single-degree-of-freedom (SDOF) models. Then, the maximum local responses are predicted by enveloping the two pushover analysis results by referring to the contribution of the first and higher modal responses, while the cumulative strain energies of the lead-rubber bearings and steel dampers are predicted from the cumulative response of the first mode. The results reveal that the responses predicted by the proposed set of pushover analyses have satisfactory accuracy.
Pushover analysis has become one of the most commonly used nonlinear static procedures (NSP) for the seismic estimation of structures in engineering practice. In this paper, a new lateral load ...pattern is presented to enhance the accuracy of conventional pushover analysis (CPA) procedures for evaluating seismic behaviors of asymmetric-plan multistory buildings, which has considered the effect of torsion and higher modes. This spatially distributed lateral load pattern is proposed eventually by introducing and calculating the coefficients of adjustment and distribution respectively. The performance and accuracy of the proposed spatial pushover analysis (SPA) procedure is verified against two distinct multistory buildings with irregular plans subjected to five medium-to-strong ground motions. Furthermore, the peak responses in terms of base shear, roof displacements, interstory drifts, plastic hinge rotations and pushover capacity curves obtained from the SPA method are compared with those from nonlinear time history analyses (NTHA), and CPA procedures. The comparative results indicate that new lateral load pattern agrees very well with the NTHA procedure. The proposed SPA procedure shows its efficiency and overcomes the limitations of current extended pushover methods to assess the seismic responses of asymmetric-plan structures. It is strongly suggested that the new load pattern as an applicable method for pushover analysis of asymmetric-plan structures.
The effect of “April 2015 Gorkha Earthquake” was devastating in terms of loss of life, heritage, buildings and emotions. A residence located at Purano Naikap-13, Kathmandu, built in 2006 was also ...severely damaged amongst many buildings. The building was a three and half story non-engineered reinforced concrete (RC) building. The main objective of this paper is to show the step-by-step process of retrofitting adopted in this building. After the initial survey and structural analysis in ETABS software, a suitable repairing and restoring of the stability of the structure was done which was followed by an appropriate retrofitting techniques. Concrete jacketing and steel jacketing with epoxy chemical grouts in columns were the two main interventions implemented. Pushover analysis was done to assess performance of the retrofitted building. The building was deemed acceptable; the Life Safety level was not exceeded under design basis earthquakes.
•Concrete jacketing and steel jacketing with epoxy chemical grouts.•Pushover analysis was done to assess performance of the retrofitted building.•Life Safety level was not exceeded under design basis earthquakes.•Provide best retrofitting, repair and restoration technique.
This paper proposes a new scaling procedure to consider the inelastic response of structure along with the effect of higher modes in scaling the selected ground motions for seismic response analysis. ...This is done by obtaining the corresponding inelastic Single-Degree-of-Freedom (SDOF) system of the structure through performing a single-run modal pushover analysis with a load pattern consistent with the combined-modal-story-shear profile obtained from response spectrum analysis. Therefore, the effect of the higher modes and interaction between them in the nonlinear phase are reflected in the inelastic SDOF. The scaling process is performed such that the peak displacement of the inelastic SDOF system under the scaled record matches the inelastic spectral displacement (target displacement). The proposed procedure is evaluated through three regular and one irregular tall building. The results demonstrate the superiority of the proposed procedure in estimating the engineering demand parameters of structures with/without important higher modes effects.
•A new pushover-based scaling procedure is proposed for seismic response analysis.•The inelastic response of the structure are considered in the proposed method.•The contribution of the higher modes are considered in the proposed method.•A simple and practical version of the proposed method is introduced.•High accuracy and smaller scatter of the results using the proposed method.
(1) Background: The protection of built heritage in historic cities located in seismically active areas is of great importance for the safety of inhabitants. Systematic care and planning are ...necessary to detect the seismic vulnerability of buildings, in order to determine priorities in rehabilitation projects and to continuously provide funds for the reconstruction of the buildings. (2) Methods: In this study, the seismic vulnerability of the buildings in the historic center of Kaštel Kambelovac, a Croatian settlement located along the Adriatic coast, has been assessed through an approach based on the calculation of vulnerability indexes. The center consists of stone masonry buildings built between the 15th and 19th centuries. The seismic vulnerability method was derived from the Italian GNDT approach, with some modifications resulting from the specificity of the buildings in the investigated area. A new damage–vulnerability–peak ground acceleration relation was developed using the vulnerability indexes and the yield and collapse accelerations of buildings obtained through non-linear static analysis. (3) Results: A seismic vulnerability map, critical peak ground accelerations for early damage and collapse states, and damage index maps for two return periods have been predicted using the developed damage curves. (4) Conclusions: The combination of the vulnerability index method with non-linear pushover analysis is an effective tool for assessing the damage of a building stock on a territorial scale.
This paper proposes a new load–deformation formulation for circular hollow section (CHS) X- and K-joints to be implemented in the pushover analysis of steel frames. The proposed formulation describes ...the load–deformation relationship of the CHS X- and K-joint through a simple function with the coefficients dependent on the ultimate strength and the geometric parameters of the joint. The strength-dependent parameter follows the mean strength equations in the latest IIW recommendations, while the geometric-dependent parameters derive from the finite element results of the CHS X- and K-joints covering a practical geometric range. The proposed joint formulation predicts closely the load–deformation responses for planar CHS X- and K-joints measured in the experiments. The non-dimensional load–deformation formulation developed in the current study provides a calibrated basis in the phenomenological representation of the nonlinear joint behavior in push-over analyses of steel space frames. The experimental results from the large-scale 2-D and 3-D frame tests validate the accuracy of the proposed formulation, which is implemented in a nonlinear pushover analysis as joint-spring elements.
•We propose a new nonlinear formulation to CHS X- and K-joints.•This formulation describes the peak and post-peak responses of the joints.•The proposed formulation derives from calibrated FE analyses for X- and K-joints.•This formulation predicts accurately the failure mechanisms in 2D and 3D frames.
Over the last few decades, the attention on the safety of existing reinforced concrete (RC) structures has significantly increased. RC bridges, in particular, are highly relevant for strategic ...importance. In the Italian context, several of these bridges were built around 1960, when engineering practice commonly ignored or underestimated the presence of seismic actions. Therefore, it is fundamental to quantify as accurately as possible their seismic safety level with state-of-the-art analysis techniques. In this paper, an efficient procedure based on the multi-modal pushover analysis approach is proposed for the risk evaluation of several bridges of the Italian highway network. This procedure, tailored for portfolio level assessment, takes into account the non-linear behavior and the complex dynamic response this type of structure with limited computational effort. Three fundamental aspects are defined for the structural modelling of bridges, i.e., materials’ constitutive law, finite element type and nonlinear hinge models. Flexural and shear nonlinearities of piers are included to account for ductile and brittle damage potential. The standardized procedure guarantees consistent comparisons among different bridges of the same network in the form of risk indexes.
PDF
