scholarly journals Seismic Assessment of Steel MRFs by Cyclic Pushover Analysis

2019 ◽  
Vol 13 (1) ◽  
pp. 12-26 ◽  
Author(s):  
F. Barbagallo ◽  
M. Bosco ◽  
A. Ghersi ◽  
E.M. Marino ◽  
P.P. Rossi
Keyword(s):  
Local Level ◽  
Pushover Analysis ◽  
Nonlinear Dynamic Analysis ◽  
Structural Response ◽  
Strength Degradation ◽  
Structural Members ◽  
Seismic Behaviour ◽  
Ground Acceleration ◽  
Nonlinear Static

Background:Structural members subjected to strong earthquakes undergo stiffness and strength degradation. To predict accurately the seismic behaviour of structures, nonlinear static methods of analysis have been developed in scientific literature. Generally, nonlinear static methods perform the pushover analysis by applying a monotonic lateral load. However, every earthquake input is characterized by several repeated loads with reverse in signs and the strength and deformation capacities of structures are generally related to the cumulative damage. This aspect is neglected by the conventional monotonic approaches, which tend to overestimate the strength and stiffness of structural members.Objective:This paper aims to investigate the possibility that the Cyclic Pushover Analysis (CPA) may be used as a tool to assess the seismic behaviour of structures. During the CPA, the structure is subjected to a distribution of horizontal forces that is reversed in sign when predefined peak displacements of the reference node are attained. This process repeats in cycles previously determined in a loading protocol.Methods:To investigate the effectiveness of the CPA in predicting the structural response, a steel moment resisting frame is designed as a case study building. A numerical model of this frame is developed in OpenSees. To examine the influence of the loading protocols on the seismic response, the CPA is run following the ATC-24 and the SAC protocols. Additionally, the seismic demand of the case study frame is determined by a Monotonic Pushover Analysis (MPA) and by Incremental nonlinear Dynamic Analysis (IDA).Results and Conclusions:The following results are obtained:• Despite the differences between the SAC and the ATC-24 loading protocols, the CPA applied according to those two protocols led to almost the same structural response of the case study frame.• The CPA showed the capability of catching the stiffness and strength degradation, which is otherwise neglected by the MPA. In fact, given a base shear or peak ground acceleration, the CPA leads to the estimation of larger displacement demands compared to the MPA.• During long (or medium) duration earthquakes, the CPA was necessary to estimate accurately the response of the structure. In fact, at a PGA equal to 1 g, the CPA estimated the top displacement demand with an error lower than 10%, while the MPA underestimated it by 18%.• The importance of considering the cyclic deterioration is shown at local level by the damage indexes of the frame. In the case of long earthquakes, given a top displacement of 600 mm (corresponding to a PGA equal to 1 g), the CPA estimated the damage indexes with an error equal to 12%.

scholarly journals Evaluation of p-delta effect in structural seismic response

2018 ◽  
Vol 162 ◽  
pp. 04019 ◽  
Author(s):  
Sardasht Sardar ◽  
Ako Hama
Keyword(s):  
Seismic Response ◽  
Pushover Analysis ◽  
Nonlinear Dynamic Analysis ◽  
Time History ◽  
Steel Structure ◽  
Nonlinear Static Analysis ◽  
Structural Behavior ◽  
Finite Element Software ◽  
History Analysis ◽  
Nonlinear Static

Numerous recent studies have assessed the effect of P-Delta on the structures. This paper investigates the effect of P-Delta in seismic response of structures with different heights. For indicating the effect of P-Delta, nonlinear static analysis (pushover analysis) and nonlinear dynamic analysis (Time history analysis) were conducted by using finite element software. The results showing that the P-Delta has a significant impact on the structural behavior mainly on the peak amplitude of building when the height of the structures increased. In addition, comparison has been made between concrete and steel structure.

scholarly journals Structural Assessment of the Hull Response of an FPSO Unit to Dropped Objects: A Case Study

2019 ◽  
Vol 26 (4) ◽  
pp. 39-46 ◽  
Author(s):  
Ozgur Ozguc
Keyword(s):  
Structural Damage ◽  
Local Buckling ◽  
Structural Response ◽  
Offshore Structures ◽  
Mechanical Equipment ◽  
Structural Members ◽  
Impact Area ◽  
Explicit Dynamic ◽  
The Impact

Abstract Offshore structures are exposed to the risk of damage caused by various types of extreme and accidental events, such as fire, explosion, collision, and dropped objects. These events cause structural damage in the impact area, including yielding of materials, local buckling, and in some cases local failure and penetration. The structural response of an FPSO hull subjected to events involving dropped objects is investigated in this study, and non-linear finite element analyses are carried out using an explicit dynamic code written LS-DYNA software. The scenarios involving dropped objects are based on the impact from the fall of a container and rigid mechanical equipment. Impact analyses of the dropped objects demonstrated that even though some structural members were permanently deformed by drop loads, no failure took place in accordance with the plastic strain criteria, as per NORSOK standards. The findings and insights derived from the present study may be informative in the safe design of floating offshore structures.

Responses and capacity curves of mid- and high-rise wood buildings subjected to seismic excitations

2020 ◽  
Vol 47 (1) ◽  
pp. 63-76 ◽  
Author(s):  
S.C. Yang ◽  
H.P. Hong ◽  
F.M. Bartlett
Keyword(s):  
Pushover Analysis ◽  
Structural Members ◽  
Initial Stiffness ◽  
Seismic Excitations ◽  
Cross Laminated Timber ◽  
High Rise ◽  
Capacity Curves ◽  
Type Construction ◽  
Nonlinear Static ◽  
Gravity System

The design and modelling of 10-, 15-, and 20-storey wood buildings with cross-laminated timber and glulam structural members are presented in the present study. The system is platform-type construction with a cross-laminated timber core, perimeter walls as lateral load resisting system, and glulam columns as the gravity system. The designed buildings satisfy requirements stipulated in applicable design codes in Canada. The hysteretic models and the associated parameters used to model the fasteners for wood members are developed. Assessments of the nonlinear inelastic seismic responses and capacity curves of the designed buildings are carried out using the incremental dynamic analysis (IDA) and nonlinear static pushover analysis (NSPA) methods. The results indicate that the NSPA curve closely approximates the mean capacity curve estimated using the IDA curves for wood buildings. The post-yield stiffness ratio to initial stiffness for the wood buildings ranges from approximately 0.35 to 0.55. The results also show that the effect of the record-to-record variability on the IDA curves is substantial.

Evaluation on Environmental Corrosion Damage of Steel Domes

2010 ◽  
Vol 44-47 ◽  
pp. 163-167
Author(s):  
Bo Chen ◽  
Jian Feng Wei ◽  
Jin Zheng
Keyword(s):  
Natural Frequency ◽  
Corrosion Damage ◽  
Exponential Model ◽  
Nonlinear Static Analysis ◽  
Space Structures ◽  
Structural Members ◽  
Nonlinear Static ◽  
Corrosion Of Steel

The evaluation on environmental corrosion damage of steel domes is carried out in this study through an integration of knowledge in material science and structural analysis. The refined exponential model for estimating corrosion of steel materials is presented based on long-term experimental data available. The formula for relating structural natural frequency sensitivity to structural member thickness is then derived to assess the sensitivity of natural frequency to variation of member thickness due to corrosion. The nonlinear static analysis is conducted to evaluate effects of atmospheric corrosion on the stress of structural members and the safety of steel space structures. A real steel dome built in China is taken as the case study to examine the feasibility of the proposed approach and to assess the potential corrosion damage to the structure..

Evaluation of Nonlinear Static Procedures in the Assessment of Building Frames

2013 ◽  
Vol 29 (4) ◽  
pp. 1459-1476 ◽  
Author(s):  
Rui Pinho ◽  
Mário Marques ◽  
Ricardo Monteiro ◽  
Chiara Casarotti ◽  
Raimundo Delgado
Keyword(s):  
Dynamic Analysis ◽  
Adaptive Capacity ◽  
Nonlinear Dynamic ◽  
Pushover Analysis ◽  
Nonlinear Dynamic Analysis ◽  
Capacity Spectrum Method ◽  
Modal Pushover Analysis ◽  
Spectrum Method ◽  
Capacity Spectrum ◽  
Nonlinear Static

In recent years a number of nonlinear static procedures (NSPs) have been developed and proposed. Such pushover-based seismic assessment procedures are relatively straightforward to employ and are generally chosen over nonlinear dynamic analysis, especially within the realm of design office application. Parametric comparisons between the different NSPs available, however, are still somewhat sparse. In this work, five commonly employed NSPs (the N2 method, capacity spectrum method, modal pushover analysis, adaptive modal combination procedure, and the adaptive capacity spectrum method) are applied in the assessment of 16 frames subjected to a large number of input motions with a view to assess the accuracy level of such approaches through comparison with nonlinear dynamic analysis results. The evaluation shows that all the NSPs are able to accurately predict displacements and to produce reasonable estimates for other response parameters, with limited dispersion. Even though no single NSP tested led to consistently superior results, modal pushover analysis and the adaptive capacity spectrum method seemed to perform slightly better.

scholarly journals Application of Nonlinear Static Procedures for the Seismic Assessment of Regular RC Moment Frame Buildings

2014 ◽  
Vol 30 (2) ◽  
pp. 767-794 ◽  
Author(s):  
Michalis Fragiadakis ◽  
Dimitrios Vamvatsikos ◽  
Mark Aschheim
Keyword(s):  
Pushover Analysis ◽  
Nonlinear Dynamic Analysis ◽  
Single Mode ◽  
Moment Frame ◽  
Seismic Demands ◽  
Frame Buildings ◽  
Moment Resisting ◽  
Nonlinear Static ◽  
Global And Local ◽  
Modal Pushover

The applicability of nonlinear static procedures for estimating the seismic demands of typical regular RC moment-resisting frames is evaluated. This work, conducted within the framework of the ATC-76-6 project, shows the degree to which nonlinear static methods can characterize global and local response demands vis-à–vis those determined by nonlinear dynamic analysis for three RC moment-frame buildings. The response quantities (engineering demand parameters) considered are peak story displacements, story drifts, story shears, and floor overturning moments. The single-mode pushover methods evaluated include the N2 and the ASCE-41 coefficient methods. Multi-modal pushover methods, such as modal pushover analysis and the consecutive modal pushover method, were also evaluated. The results indicate that the relatively good performance of the single-mode methods observed for low-rise buildings rapidly deteriorates as the number of stories increases. The multi-modal techniques generally extend the range of applicability of pushover methods, but at the cost of additional computation and without ensuring the reliability of the results.

scholarly journals Influence of FE Modelling Approaches on Vulnerabilities of RC School Buildings and Proposal of a CFRP Retrofitting Intervention

2019 ◽  
Vol 13 (1) ◽  
pp. 269-287 ◽  
Author(s):  
G. Valentina ◽  
Marina Poiani ◽  
Francesco Clementi ◽  
Giuseppe Pace ◽  
Stefano Lenci
Keyword(s):  
Continuum Model ◽  
Seismic Vulnerability ◽  
School Buildings ◽  
Seismic Behaviour ◽  
Displacement Capacity ◽  
Reinforced Polymer ◽  
Fibre Reinforced Polymer ◽  
Nonlinear Static ◽  
Lumped Plasticity

Background: The vulnerability assessment of existing school buildings against earthquakes represents a priority concern for society. In recent years, several countries promote seismic rehabilitation projects of school buildings, including the allocation of funds to regions with high seismic hazard. Objective: This research aims to highlight some key role aspects related to difficulties encountered in the numerical modelling of RC structures hosting school activities. This work evaluates the seismic vulnerability of school buildings located in the municipality of Trecastelli (Marche, Central Italy) to quantify the effective influence of typical and specific seismic vulnerabilities detected on the global seismic behaviour of each building. The effectiveness of a possible Carbon Fibre Reinforced Polymer (CFRP) local strengthening intervention, for the case study, aimed to confine unconfined beam-column joints is also considered. Methods: Three different numerical models of a Reinforced Concrete (RC) school building are implemented with the lumped plasticity, the distributed plasticity (fibre) and the 3D Continuum Finite Element (FE) approaches. Nonlinear static (pushover) analyses are performed to assess the global seismic behaviour of the structure, and the limitations to represent the reality with different approaches. After the seismic vulnerability assessment of the case study, a CFRP retrofitting intervention is proposed to confine external beam-column joints. Results: The comparison of the numerical results of three models shows that the fibre model is the least suitable means to represent shear problems, while the lumped plasticity model is closer to reality than the previous one even if it does not take into account the concomitance of bending, shear and axial force and the interaction between them in the inelastic response. Of course, the 3D Continuum model is the most accurate representation to describe the complex and combined mechanisms developed in the joint panels. Nonlinear static (pushover) analyses carried out on unreinforced and reinforced structures of Continuum model demonstrate that the Fibre Reinforced Polymer (FRP) strengthening improves the displacement capacity of the structure. Conclusion: This study has highlighted the strengths and weaknesses of different modelling types. The meaningful information about mechanisms developed in joints given by the 3D Continuum FE model is useful to identify shortcomings of the design project and to conceive a retrofitting strengthening intervention. CFRP sheets externally bonded on beam-column joints may improve the seismic frame performances without a significant change of the structural stiffness, promoting a ductile failure mode with a higher displacement capacity than the unreinforced case.

scholarly journals Seismic Vulnerability Assessment and Strengthening Interventions of Structural Units of a Typical Clustered Masonry Building in the Campania Region of Italy

GeoHazards ◽  
2021 ◽  
Vol 2 (2) ◽  
pp. 101-119
Author(s):  
Antonio Formisano ◽  
Nicola Chieffo ◽  
Generoso Vaiano
Keyword(s):  
Seismic Vulnerability ◽  
Structural Response ◽  
Masonry Building ◽  
Structural Behaviour ◽  
Seismic Behaviour ◽  
Structural Units ◽  
Campania Region ◽  
Seismic Vulnerability Assessment ◽  
Before And After

The present paper aims at inspecting the structural behaviour of a typical masonry aggregate located in the historical centre of Cercola, a municipality in the province of Naples. The clustered building under study consists of four structural units mutually connected to each other made of tuff stone and deformable floors. Two distinct structural units, namely in heading and intermediate places, in both isolated and aggregate conditions, are examined to estimate the influence of structural positions on the global seismic response of the examined case study buildings. For this purpose, non-linear static analyses are performed using the 3MURI software. Pushover analyses are conducted to both evaluate the seismic behaviour of examined structural units and improve their earthquake performances while considering proper retrofit interventions on vertical and horizontal structures. The analysis results are plotted in terms of risk factor, stiffness, and ductility. Finally, a set of fragility functions are derived to point out the structural response of the case study buildings before and after retrofit interventions. From the achieved results, it is highlighted that retrofit interventions improve the structural performances of the buildings, especially those of structural units in aggregate conditions.

Seismic Fragility Analysis of a Water Storage Structure

2004 ◽  
Author(s):  
K. Bhargava ◽  
A. K. Ghosh ◽  
S. Ramanujam
Keyword(s):  
Seismic Analysis ◽  
Water Storage ◽  
Structural Response ◽  
Seismic Fragility ◽  
Material Strength ◽  
Structural Damping ◽  
Ground Acceleration ◽  
Storage Structure ◽  
Hydrodynamic Effects

The present paper is concerned with the seismic response and fragility evaluation of a water storage structure. Seismic analysis has been carried out considering the hydrodynamic effects of the contained water. The various parameters that could affect the seismic structural response include material strength of concrete, structural damping available within the structure and the normalized ground motion response spectral shape. Based on this limited case study; the seismic fragility of the structure is developed as families of conditional probability curves plotted against peak ground acceleration (PGA) at the location of interest. The procedure adopted incorporates the various randomness and uncertainty associated with the parameters under consideration.

scholarly journals Seismic Loss Estimation in Pre-1970 Residential RC Buildings: The Role of Infills and Services in Low–Mid-Rise Case Studies

2020 ◽  
Vol 6 ◽  
Author(s):  
Carlo Del Gaudio ◽  
Maria Teresa De Risi ◽  
Santa Anna Scala ◽  
Gerardo Mario Verderame
Keyword(s):  
Case Studies ◽  
Pushover Analysis ◽  
Economic Loss ◽  
Loss Estimation ◽  
Lessons Learned ◽  
Rc Buildings ◽  
Loss Assessment ◽  
Ground Acceleration ◽  
Masonry Infills

The lessons learned after recent earthquakes have highlighted the key role played by infills and services in damage and loss of Reinforced Concrete (RC) buildings. Their influence in seismic performance and loss estimation of selected RC building case studies is thoroughly analyzed here. The case study selection aims to be representative of existing buildings built in Italy before 1970, and covers a different number of stories and design typologies. The seismic responses of the case-study buildings are numerically analyzed by means of non-linear static pushover analysis (PO) considering a lumped plasticity approach with a quadri-linear flexural response for beam/column elements (properly calibrated for RC elements reinforced with plain bars) and a tri-linear compressive-only axial response with diagonal concentric struts for infill panels (empirically derived from experimental data on hollow clay masonry walls). Economic loss estimation is carried out via a component-based methodology that relies on the main repairing activities and resultant costs required for the refurbishment of infills and services for different damage levels. Accordingly, a damage analysis is performed herein, given the intensity measure, based on a comparison between Interstory drift demand from PO analysis and drift-based fragility functions specific for masonry infills. Loss curves, relating the total building repair cost to peak ground acceleration (PGA), are presented and compared for the analyzed case study buildings to show their trends and quantify the incidence of infills and services with respect to the reconstruction cost. A comparison between these outcomes and those recently found in the literature emphasizes the robustness of the considered approach and the reliability of the hypotheses about damage and loss assessment.

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