Three-dimensional Nonlinear Dynamic Analysis Research Articles

Fragility and comfortability curves development and seismic risk assessment of a masonry building under earthquakes induced by geothermal power plants operation

This research is an attempt to estimate the seismic risk of geothermal power plants (GPPs) operation on the masonry buildings located in the vicinity of these infrastructures through a probabilistic framework. In this regard, a typical masonry building in Germany is considered. In the first part, the fragility and comfortability curves of this building are established. For this purpose, a set of 30 ground motions recorded due to GPPs activity are used for performing elaborated three-dimensional nonlinear incremental dynamic analysis to construct the fragility and comfortability curves. In the second part of the research work, by using the Monte-Carlo simulation technique and adopting the hazard model capable of simulating both seismological characteristics and ground motion intensities, the required number of probable hazard scenarios are generated for different ranges of GPPs injection flow rates. Afterward, the seismic risk imposed on the masonry building is evaluated by considering the developed fragility and comfortability curves. The outcomes highlight that the risk of facing structural damage is not significant; however, the disturbance of buildings’ residents is highly probable and can lead to considerable seismic risk. In addition, in the close vicinity of the earthquake epicenter (less than 5 km), the estimated risk increases tangibly in comparison with the larger distances (more than 15 km).

A comprehensive approach for bridge performance evaluation under rockfall impact integrated with geological hazard analysis

Rockfall is one kind of major hazard that seriously threatens the safety of bridge structures passing through mountainous areas. The complexity of geological conditions in mountainous areas makes it difficult to determine the initial impact parameters of falling rock in the bridge performance analysis. At present, the subjective and deterministic methods are adopted to get the initial motion parameters of the falling rock for evaluating the structural responses. In this paper, the probability distributions of falling rocks collision parameters are obtained by the rockfall Monte Carlo simulations. Then the characteristic values from the probability distribution of rock motion parameters are taken as the input parameters in the dynamic simulation of bridge structure. Finally, three-dimensional nonlinear dynamic analysis is employed to evaluate the safety of the bridge structure under rockfall hazards. The residual resistance index (RRI) is presented for quantifying the post-impact performance of bridge pier and girder under rock collision. The structural safety is mainly dominated by the impact mass and translational velocity of the falling rock rather than the rotational velocity and impact angle. The rock shape also has non-negligible influence on the structural dynamic responses and performance, and the cube-like rock induces more severe structural damage than other shapes. According to the RRI and probability distribution of rock mass, the non-exceedance probability of RRI is obtained which can be used for the risk analysis of rockfall impacting on bridges. The proposed comprehensive approach for bridge performance evaluation considers the uncertainty of rockfall characteristics, and it provides more reasonable solution to investigate the impact performance of bridge structure under rockfall disasters.

Three-Dimensional Nonlinear Dynamic Analysis of Base Isolated Cylindrical Steel Tank

Failure of a tank during an earthquake can result in significant financial, human, and environmental losses. Thus, their lack of resiliency against strong earthquakes may result in refinery disruption. This has the potential to have a considerable impact on any economic system. As a result, more research into the seismic performance of tank structures is required to attain the highest possible level of resistance against strong earthquakes. In this paper, we aim to look into the installation of seismic isolation systems in cylindrical steel storage tanks. A nonlinear 3D finite element model is developed with ANSYS software. Moreover, tank wall material nonlinearity, fluid-structure-interaction, and sloshing components are considered. The bilinear hysteretic LRB is used for modal and time-history analysis. In this work, three tanks with varying aspect ratios are studied: "Model A", "Model B", and "Model C". Furthermore, the fixed tank's fundamental frequencies were compared to the analytical results of the American API 650 Standard. Subsequently, the dynamic behavior response of the researched tanks to the horizontal component of the El-Centro 1940 earthquake with PGAs of 0.34g and 0.5g is investigated. As a result, the dominating frequency of the seismic isolation system is within the effective frequency range of seismically isolated systems. The results illustrate that the base isolation limits the tank wall movement with a large displacement in the isolators; the mode shape is a cantilever beam in all isolated circumstances. The total seismic response reduction in the slender tanks is greater as compared to the broad case in the base-isolated tanks. The sloshing displacement increases with an increase in the tank aspect ratio. Additionally, the isolation device eliminates tank buckling at the base and top of the tank shell during seismic excitation (elephant foot and diamond buckling). It can be concluded that the seismic isolation technique has a more significant impact on reducing the dynamic response of ground-supported tanks, particularly in taller tanks as compared to broad tanks. Doi: 10.28991/CEJ-2022-08-06-013 Full Text: PDF

Kinematic response of single vertical and batter piles to bidirectional ground motions in liquefiable soil

Kinematic responses of single fixed head vertical and batter piles in liquefiable soil under bidirectional ground motions have been studied with fully-coupled three-dimensional nonlinear dynamic analyses. Pressure dependent multi-yield constitutive model has been adopted for modeling the liquefiable sand behavior. The variable permeability of saturated sand during the process of liquefaction process has also been considered. The analyses are carried out for combinations of bidirectional earthquake loading conditions. For this, combination of longitudinal and transverse ground motions as well as combination of longitudinal and vertical motions are considered. The responses of the soil-pile systems under liquefying ground conditions, subjected to these bidirectional ground motions, are compared with the unidirectional loading conditions. Further, the effect of sloping ground on the response of the piles under bidirectional ground motions is also investigated. The developed sectional forces in both vertical and batter piles are lesser under bidirectional motions in comparison to unidirectional ground motion in both level and sloping grounds. However, the pile displacement is more in case of sloping ground under bidirectional ground motions comparing to unidirectional motion.

Analytical Fragility Curves for Seismic Design of Glass Systems Based on Cloud Analysis

Given the growing spread of glass as a construction material, the knowledge of structural response must be ensured, especially under dynamic accidental loads. In this regard, an increasingly popular method to probabilistically characterize the seismic response of a given structure is based on the use of “fragility” or “seismic vulnerability” curves. Most existing applications, however, typically refer to construction and structural members composed of traditional building materials. The present study extends and adapts such a calculation method to innovative structural glass systems, which are characterized by specific material properties and expected damage mechanisms, restraint details, and dynamic features. Suitable Engineering Demand Parameters (EDPs) for seismic design are thus required. In this paper, a major advantage is represented by the use of Cloud Analysis in the Cornell’s reliability method, for the seismic assessment of two different case-study glass systems. Cloud Analysis is known to represent a simple and immediate tool to analytically investigate a given (glass) structure by taking into account variations in seismic motions and uncertainties of structural parameters. Such a method is exploited by means of detailed three-dimensional (3D) Finite Element (FE) numerical models and non-linear dynamic analyses (ABAQUS/Standard). Critical issues and typical failure mechanisms for in-plane seismically loaded glass systems are discussed. The validity of reference EDPs are addressed for the examined solutions. Based on a broad seismic investigation (60 records in total), fragility curves are developed from parametric results, so as to support a multi-hazard performance-based design (PBD) procedure.

Progressive Collapse Analyses of Buildings Subjected to Earthquake Loads

Progressive collapse is a partial or total failure of a building that mostly occurs when the build-ing loses primary structural elements (typically columns) due to accidental or natural hazards. The failure of structures due to an earthquake is one of the most important and frequent types of progressive collapse. In this study, the finite element method is used to assess the response of multistory reinforced concrete buildings subjected to column loss during an earthquake. Three-dimensional nonlinear dynamic analyses are carried out using SAP2000 V.20 program. The ef-fects of different parameters on the progressive collapse behavior are investigated, namely: the location of the removed column within the ground floor; the method of column removal (sudden, in two-steps, and in four-steps) and the removal timing during the earthquake. It is demonstrated that the collapse occurs when all or most of the hinges at the bases of the ground floor columns reach their collapse level. The chosen column removal timing and policy affect the structural behavior considerably. It is realized that, the risk of building collapse increases when the removal timing harmonizes with the peak ground acceleration timing. Based on the adopted earthquake characteristics and building configurations, it is found that, the two steps removal scenario is the most dangerous one.Keywords:Progressive collapse, Concrete buildings, Seismic load, Nonlinear dynamic analysis, Plastic hinge.© 2014

Three-dimensional nonlinear dynamic analysis of slack cable structures using node Relaxation method

This study proposes a robust technique for large displacement analysis of slack cable structures subjected to dynamic loadings using a novel method, entitled Node Relaxation. Ordinary numerical methods are usually unable to analyze cable structures due to singularities arising from large displacements and rotations following any alteration of the applied loads. When dynamic loads are considered, handling these singularities in numerical analyses becomes even more challenging. In this paper, an effective iterative method is proposed for three-dimensional large-displacement dynamic analysis of structures consisting slack cables as the primary load-bearing system. The cable structure is modeled using a set of nonlinear springs with properties that are constantly updated as the structural form gradually responds to the applied loads. The large changes in the cable forms are captured by considering an impedance relation that is used to determine the displacement magnitude in the directions where the structure does not have an appreciable stiffness. The method is verified against closed-form solution of wave transfer phenomenon. The effectiveness of the method is also demonstrated by solving several numerical examples.

Upgrading the seismic performance of underground structures by introducing lead-filled steel tube dampers

Central-column failure can cause large underground structures to collapse during strong earthquakes. The use of lead-filled steel-tube dampers (LFSTDs) in the seismic design of such structures is proposed to mitigate or prevent such an eventuality. Three-dimensional nonlinear dynamic analyses of the Daikai subway station with and without LFSTDs under the action of the Hyogoken–Nambu earthquake has been performed, considering soil-structure interaction. The feasibility of the proposed method was verified from four aspects—force, deformation, damage, and energy dissipation. The effects of variability in seismic inputs, strength ratio, and arrangement mode of dampers on the structural dynamic response characteristics have been discussed. Results reveal that the application of LFSTDs to large underground structures remarkably reduces the force, deformation, and damage associated with the central column under seismic loading. Additionally, a strength ratio of 0.4 is recommended when using LFSTDs, whereas in cases without LFTSTDs, the strength of the central column must be appropriately enhanced.

Progressive collapse vulnerability assessment of irregular voided buildings located in Seismic-Prone areas

Nowadays, many special architectural forms of voided buildings such as hotels, commercial complexes, etc. are constructed in famous cities. In this paper, the effects of opening in the volume of low- and mid-rise irregular voided structures with low to high seismic resistance on the progressive collapse vulnerability are investigated. The structures are three and nine stories high, seismically designed with a steel moment frame system based on the AISC seismic code, and are located in sites with high, moderate, and low levels of seismicity. Detailed three-dimensional nonlinear dynamic analysis is performed to investigate spatially distributed damage to frame members and the structural robustness against abnormal loads according to the GSA 2016 guidelines. The response quantities are expressed in the form of the displacement of the node above the removed column, the spatially distributed formation of plastic hinges, the stress growth in nearby columns after progressive collapse occurrence, and the connection robustness analysis. The results show moment connections that govern the robustness of the structure and they are the most critical components in the structure. In addition, larger openings and proximity of the column removal scenario to position of the opening play a significant role in reducing the progressive collapse vulnerability of voided structures. However, in the scenarios of removing the internal column away from the opening, the progressive collapse mechanism of the structures with or without opening does not differ. Therefore, in the structural robustness analysis, internal columns away from opening of the voided buildings should be considered as critical and controllable elements in the progressive collapse capacity of structures. Among the modeled buildings, only the buildings located in high seismic areas can pass progressive collapse analyses and the seismicity level of the site is the most important parameter in robustness of the structure in comparison with the height or irregularity of the structure. Increasing the height of structures also reduces the amount of stress growth in the columns adjacent to the demolished column and the taller structures are safer structures in this regard.

Effect of incidence angle on the seismic performance of skewed bridges retrofitted with buckling-restrained braces

This study examines the effect of ground motion (GM) incidence angles on the seismic response of skewed bridges retrofitted with buckling-restrained braces (BRBs) under far-field and near-field ground motions (FFGMs and NFGMs). Bridge models for a three-span reinforced concrete bridge with skew angles of 0°, 18°, 36°, and 54° are used as a case study. Three-dimensional nonlinear dynamic analyses are performed with scaled GMs under 11 incidence angles (from 0° to 180°) to obtain the maximum bridge response parameters on the maximum considered earthquake hazard level. This study demonstrates the effectiveness of a BRB retrofit to reduce the influence of GM incidence angle. The results indicate that skewed bridges are less sensitive to the GM incidence angle and BRBs further decrease the incidence effect. Also, the seismic response under different GM incidence angles is more predictable when the bridge is subjected to FFGMs. In general, the maximum response of skewed bridges could be estimated by applying the scaled principal GMs along the bridge’s longitudinal axis and its orthogonal direction (i.e., 0° and 90°), regardless of GM characteristics, skewed angle, and BRB retrofit.

Peak seismic response of a symmetric base-isolated steel building: near vs. far fault excitations and varying incident angle

Since the peak seismic response of a base-isolated building strongly depends on the characteristics of the imposed seismic ground motion, the behavior of a base-isolated building under different seismic ground motions is studied, in order to better assess their effects on its peak seismic response. Specifically, the behavior of a typical steel building is examined as base-isolated with elastomeric bearings, while the effect of near-fault ground motions is studied by imposing 7 pairs of near- and 7 pairs of far-fault seismic records, from the same 7 earthquake events, to the building, under 3 different loading combinations, through three-dimensional (3D) nonlinear dynamic analyses, conducted with SAP2000. The results indicate that near-fault seismic components are more likely to increase the building\'s peak seismic response than the corresponding far-fault components. Furthermore, the direction of the imposed earthquake excitations is also varied by rotating the imposed pairs of seismic records from 0° to 360°,with respect to the major construction axes. It is observed that the peak seismic responses along the critical incident angles, which in general differ from the major horizontal construction axes of the building, are significantly higher. Moreover, the influence of 5% and 10% accidental mass eccentricities is also studied, revealing that when considering accidental mass eccentricities the peak relative displacements of the base isolated building at the isolation level are substantially increased, while the peak floor accelerations and interstory drifts of its superstructure are only slightly affected.

Damage assessment and collapse investigation of three historical masonry palaces under seismic actions

Abstract The preservation (in terms of inhibition of failures and collapses) of architectural heritage against horizontal loads (such as earthquakes) requires an accurate assessment of the non-linear response up to failure: to this aim, the use of advanced numerical tools to perform three-dimensional non-linear dynamic analyses is fundamental. This paper investigates the performance (up to the activation of local failures and under horizontal loads) of three historical masonry palaces of the outstanding cultural heritage in Mantua (Northern Italy) after the 2012 Emilia earthquake. Despite the unquestionable importance of the three case studies, until now these palaces have not been studied with advanced numerical simulations; moreover, the recent seismic sequence and the consequent significant cracks patterns observed in the post-earthquake survey phase have pointed out their vulnerability even to small seismic actions. The first part of the study was addressed to an accurate knowledge of the three palaces, focusing especially on the information gathered during on-site surveys, bibliographical and historical research: the data collected were employed to detect the complex three-dimensional geometry of the palaces under study and to define the cracks patterns. In the second part of the study, detailed and representative three-dimensional finite element (FE) models of the structures were developed and non-linear dynamic analyses were carried out to obtain a deep numerical insight into the seismic response of the three palaces, identifying the most vulnerable elements for each structure. The comparison between the numerical results and the damage survey showed that the numerical approach used in this study may be an adequate tool to properly evaluate the seismic response of historical masonry buildings. A comparative assessment of the results obtained for the different palaces was performed in terms of predicted damage distributions, energy density dissipated by tensile damage and maximum displacements registered for the different macro-elements.

Seismic Response of Nonseismically Designed Reinforced Concrete Low Rise Buildings

In this paper, the time-history responses of a square plan two-story reinforced concrete prototype building, considering the elastic and inelastic behavior of the materials, were studied numerically. ABAQUS software was used in three-dimensional (3D) nonlinear dynamic analysis to predict the inelastic response of the buildings. Concrete Damage Plasticity Model (CDPM) has been used to model the inelastic behavior of the reinforced concrete building under seismic excitation. The input data included geometric information, material properties, and the ground motion. The building structure was designed only for gravity load according to ACI 318 with non-seismically detailing requirements. The prototype building was subjected to El Centro 1940 NS earthquake at different amplitudes (PGA=0.05g, PGA=0.15g, and PGA=0.32g). The elastic and inelastic responses of the 3D numerical model of the same building were evaluated. The differences between the elastic and inelastic displacements and base shear forces were analyzed. It was found from the results that base shear responses are significantly more sensitive to the numerical model of analysis than displacement responses. The evaluation showed that the base shear force and displacement responses of a two-story R.C. building subjected to severe earthquake excitation are very sensitive to the numerical model used whether it is elastic or inelastic.

Seismic performance of reinforce concrete buildings designed according to codes in Bangladesh, India and U.S.

This paper focuses on the comparison of seismic design provisions in Bangladesh (BNBC-1993), India (IS-1893), and the U.S. (ASCE 7-10) in relation to analysis, design, and seismic performance of reinforced concrete buildings on the basis of the type of allowable analysis procedures, zoning system, site classification, fundamental vibration period of the structure, response reduction factor, importance factor, minimum design lateral force, allowable story drifts, and design response spectra.Three geometrically similar commercial reinforced concrete buildings in high seismic regions of Bangladesh, India, and U.S. were designed and detailed per the respective codes. Three-dimensional nonlinear dynamic analyses of the designed structures were conducted. Each structure was subjected to a pair of orthogonally applied artificial ground motions compatible with the design response spectrum for each building code. The structural performance of each building was compared in terms of roof displacements, inter-story drifts, load-carrying capacity of beams and columns, and overall energy dissipation characteristics. The comparisons allowed an in-depth evaluation of the differences in the seismic performance of buildings designed according to ASCE 7-10, BNBC-1993, and IS-1893 codes. The Indian code performed better when subjected to the ground motion that is intended to represent the Indian design response spectrum.

Nonlinear dynamic and bilinear fatigue reliability analyses of marine risers in deep offshore fields

ABSTRACTDepleting oil reserves in shallow water are opening the avenues of new ventures in deep sea conditions. India is no exception; deep sea explorations are highly recommended and exercised. As part of the design process, there are requirements of structural failure criteria, such as rupture by over loading, fatigue failures, buckling or an unstable fracture. Three-dimensional nonlinear dynamic analysis of riser is obtained in time domain using finite-element solver ABAQUS/Aqua. The response histories so obtained are employed for the study of fatigue reliability assessment of risers. Fatigue model is based on a bilinear relationship that gives the crack growth linked failure criterion to describe the interaction between fracture and plastic collapse. Uncertainty modelling, especially fatigue crack growth parameters, is undertaken with the help of recently published data in support of bilinear crack growth relationship. Results pertaining to fatigue reliability and fatigue crack size evolution are presented using Monte Carlo simulation. The bilinear crack growth model is found to lead to higher fatigue life estimation as compared to linear fracture mechanics model. Sensitivity behaviour pertinent to limit state adopted has been thoroughly investigated. These findings implicate inspection schemes for components of the marine structures to ensure minimisation of the surprises due to wide scatter of the fatigue phenomenon in marine environment.

A Parametric Study on the Progressive Collapse Potential of Steel Buildings under Truck Collision

In this paper, the initiation and propagation of structural damage in a building due to the truck collision to one of its corner columns were investigated. For this purpose, a three-dimensional 4-story moment resisting steel frame with intermediate ductility was considered. The structure was designed using ETABS software under standard dead, live, and earthquake loads, and then impact loading was applied on the structure using ABAQUS software. The effect of truck collision with different weights and speeds was simulated conducting three-dimensional nonlinear dynamic analyses. The internal stresses and forces created in the directly impacted column, as well as other parts of the structure, were obtained. Using appropriate plasticity models, the shear failure of a steel material was considered. A parametric study was performed in order to investigate the effect of different parameters on the possibility of progressive collapse. To validate the procedure of impact modeling, some available experimental vehicle to column collision tests were simulated. The results revealed that the mass and speed of the impactor had a significant effect on the response of the structure. So that, for high-momentum impactors, the traditional column removal method may yield a good approximation of the behavior of the structure. However, for low-momentum impactors, a time-history analysis without removing the hit column is needed.

Dense Granular Columns in Liquefiable Ground. II: Effects on Deformations

AbstractDense granular columns can be used to mitigate liquefaction hazards through a combination of densification, increases in lateral stress, reinforcement, and drainage effects. Three-dimensional (3D) nonlinear dynamic finite-element analyses are used to examine the effectiveness of dense granular columns for reducing liquefaction-induced deformations in the event that the triggering of liquefaction in the native soils is not prevented. The finite-element analyses consider unit cells with dense granular columns (improved case) and without granular columns (unimproved case). Parametric analyses are used to isolate aspects related to the different improvement mechanisms. The parametric studies consider a range of area replacement ratios, shear modulus ratios, diameter of granular columns, liquefiable soil depth, hydraulic conductivity, surface pressures, slope angle, penetration resistances in the native soil, and spatial variations in those penetration resistances. A set of 10 acceleration time histori...

Progressive collapse assessment of multistory reinforced concrete structures subjected to seismic actions

Progressive collapse is a catastrophic partial or total failure of a structure that mostly occurs when a structure loses a primary component like a column. Some international standards have started to consider progressive collapse resistance in various approaches. In this study, the ‘Unified Facilities Criterion’ guidelines were used in assessing the structure; these guidelines represent one of the codes that discuss progressive collapse using sophisticated approaches. Three-dimensional nonlinear dynamic analyses using the ‘Applied Element Method’ were performed for a structure that lost a column during a seismic action. A parametric study was made to investigate the effect of different parameters on progressive collapse. In this study, a primary structural component was assumed lost during an earthquake. The studied parameters were the location of the removed column in plan, the level of the removed column, the case of loading, and the consideration of the slabs. For the study cases, it was concluded that the buildings designed according to the Egyptian code satisfies the progressive collapse requirements stated by ‘Unified Facilities Criteria’ (UFC) guidelines requirements with a safety factor of 1.97. Also, it was found that losing a column during a seismic action is more critical for progressive collapse than under gravity load. Finally, this study elaborated the importance of considering the slab in progressive collapse analysis of multistory buildings in order to include the significant catenary action developed by the slabs.

Development of diaphragm connector elements for three-dimensional nonlinear dynamic analysis of precast concrete structures

Diaphragm connector elements were developed for three-dimensional finite element models of precast concrete structures used in nonlinear time history analyses. The use of discrete elements for the diaphragm connectors permits the direct evaluation of local force and deformation demands, information needed in calibrating design factors for a new diaphragm seismic design methodology. This article describes the element formulation. The connector elements consist of assemblages of standard elements readily available in most finite element software libraries. The connector element calibration is based on full-scale testing of common precast diaphragm connectors. In these tests, the connector exhibited hysteretic pinching, stiffness/strength degradation, and slip mechanisms. The diaphragm connector elements were constructed to capture these behaviors to an accuracy sufficient for establishing viable design factors, while still appropriate for insertion into large degree-of-freedom models. The models are validated against the results of simulation-driven tests for critical precast diaphragm joints and a half-scale shake table test.

Nonlinear Seismic Analysis of Reinforced Concrete Bridges Using the Force Analogy Method

Abstract In this paper, a three-dimensional nonlinear dynamic analysis framework for RC bridges is established based on the force analogy method (FAM). Two biaxial local plastic mechanisms, rotation hinge (RH) and slide hinge (SH), are proposed based on the fundamental concept of FAM to simulate the nonlinear flexure-shear interactive behavior of RC piers, a critical consideration for seismic performance assessment of RC bridges. The RHs located at the ends of RC piers express the relationships of moment versus plastic rotation, whereas the SHs are assigned to simulate the shear versus plastic shear deformation behaviors of RC piers. Coupling the presented biaxial local plastic mechanisms with FAM, the nonlinear response of RC bridges under bidirectional earthquakes can be evaluated. Because only constant initial stiffness matrices are used throughout the whole analyzing process, the state space integration formulation can be used for solving the equations of motion, which makes the computational process ...