Nonlinear Pushover Analysis Research Articles

Target‐drift seismic‐force‐based design of one‐story reinforced concrete precast buildings considering the requirements of the second generation of the Eurocode 8 standard

AbstractResults are presented concerning the force‐based design of a wide range of reinforced concrete, single‐story precast buildings, considering the requirements of the new Eurocode 8 standard. The relevant criterion defining the cross‐sectional dimensions of the columns was the 2% drift limitation. Buildings were designed considering a behavior factor of 3 and a 50% reduction in stiffness corresponding to the gross cross‐section. The design evaluation, using a nonlinear pushover analysis, revealed that all the buildings could expect approximately twice the drift considered in the design with significant second‐order effects, particularly in very tall columns. The main reasons for large discrepancies between the elastic and nonlinear analyses were the arbitrarily selected behavior factor and the arbitrarily selected reduction in stiffness corresponding to the gross cross‐section (the stiffness considered in the design was approximately double what the nonlinear analysis revealed). The analysis revealed that these two quantities are closely correlated. Once the dimensions of the columns had been selected, the force and initial stiffness reduction could not be chosen arbitrarily. Correlations were determined between the column dimensions, theoretical stiffness reduction, seismic force reduction (behavior factor) and second‐order effects. From these correlations, a new target‐drift force‐based design methodology was proposed. All considered buildings were redesigned using the proposed method. The results of the new design and the nonlinear‐pushover‐based analysis correlated well.

Fragility analysis of existing RCC frame structure

This In recent years, number of studies have been carried out for the evaluation of vulnerability of structure during seismic events. Fragility analysis is one of the important probabilistic approach to estimate the damage data at different damage state during seismic events. The G+7 Reinforced Concrete frame structure is considered for analysis. The structure is analyzed in ETABS by Non-linear Pushover Analysis. Fragility curve developed for Non-linear Pushover Analysis from results obtained by capacity spectrum method for different damage states. The fragility curves are derived from analytical method. The fragility points for different damage states are derived from analytical formula. Fragility curve is plotted for probability in Y-axis and spectral displacement in X-axis for 4 different damage states from Non-linear Pushover Analysis. From Incremental Dynamic Analysis fragility curve plotted for probability in Y-axis and peak ground acceleration in X-axis for five different damage state. The behavior of fragility curve after achieving the 100% probability for different damage state is constant.

A simplified load-slip model for composite FRP-to-concrete tie with anchors for lateral performance prediction of strengthened squat RCSWs

This study addresses the critical need to enhance the lateral performance of existing reinforced concrete shear walls (RCSWs) that have become vulnerable to lateral loads due to outdated design codes and seismic activities. The paper introduces a novel tri-linear constitutive model for composite fiber-reinforced polymer (FRP)-to-concrete ties to predict the lateral behavior of RCSWs subjected to lateral loads. A simplified strut-and-tie model (STM) was employed, integrating a novel tri-linear model for FRP-to-concrete ties with the bond-slip and anchorage effects. Non-linear pushover analysis was conducted to simulate the lateral performance of FRP-strengthened RCSWs. The conducted STM was validated through experimental and numerical data from existing studies to assess its accuracy. The tri-linear constitutive model effectively predicted the lateral load and displacement capacities of FRP-strengthened RCSWs, accurately simulating both diagonal shear and flexure failure modes. Moreover, this model is applicable to both cracked concrete substrates and full-scale walls, accommodating various types of FRP composites, and different anchoring configurations, offering a robust tool for the seismic assessment of existing structures. The model was also applied to multi-story buildings, proving robust in handling complex geometry and offering enhanced computational efficiency compared to finite element (FE) analysis. This study confirms the applicability of the proposed model for practical use in assessing and designing FRP-strengthened RCSWs, offering a faster alternative to complex finite element analysis without sacrificing accuracy.

Nonlinear pushover analysis of the mechanical influences under the varied stories and column orientations in RC structures

Nonlinear pushover analysis of the mechanical influences under the varied stories and column orientations in RC structures

Seismic fragility analysis and reliability evaluation for ancient stone pagoda using distinct element method

This study presents an application of performance-based assessment to establish fragility functions and evaluate the seismic reliability of an ancient stone pagoda in Korea. The pagoda was constructed of stone elements which were stacked over each other in layers without bonding material. To account for the discrete nature of this kind of structural configuration, the distinct element method is used to perform the incremental dynamic analysis to develop fragility functions. Three performance levels are specified on the capacity curve which is established based on non-linear pushover analysis. The randomness in seismic demand generation was considered when exciting the pagoda by a set of 23 input ground motion records, which were scaled into different intensity levels. The seismic response of the pagoda under different ground motions at several peak ground acceleration levels shows that the predominant frequency of the excitation is closely related to the behavior of this kind of structure. Ground motions with lower predominant frequency values induce stronger distortion to the pagoda than the ones with higher predominant frequency. The fragility functions estimated by maximum likelihood method show that earthquakes with peak ground motion of 0.469 g have a 50% probability of causing a collapse on the pagoda in the most conservative assessment. The probability of the pagoda collapsing within 50 years is 1.65% for the most earthquake-vulnerable site among the sites considered in the study.

Applying a 2D Variational Rigid Block Modeling Method to Rubble Stone Masonry Walls Considering Uncertainty in Material Properties

ABSTRACT The computational cost of detailed micro-modeling of masonry structures can be minimized with rigid block analysis methods, where a variational formulation is particularly interesting as it allows for nonlinear pushover analysis. This work investigates the accuracy of this modeling method in predicting the response of rubble stone masonry walls in shear compression tests. To this end, we extend the mathematical programming problem by including cohesion, compressive strength, and tensile strength in the formulation and implement an improved pushover procedure, which guards compatibility of the displaced shape and crack patterns at the intersection of elastic and rigid contact models. Additionally, we reduce model uncertainty, introduced through sampling material properties with distributions estimated based on results from tests on mortar masonry joints and on mortar specimens, by correlating the predicted crack patterns with the observed ones. The findings show that (i) model falsification based on crack pattern is an effective method for reducing the parameter uncertainty of stone masonry walls; and that (ii) the improved pushover procedure predicts the pre- and post-peak response of stone masonry walls very well with analysis times of less than 20 minutes for 2D models where stones and mortar are modeled explicitly.

Seismic Assessment of Existing Masonry Buildings Using Damage Mechanics

This paper presents research concerning the numerical simulation of existing masonry buildings when subjected to pushover analysis. A nonlinear static analysis is undertaken using the commercial software ABAQUS standard, in which masonry structures are modelled using damage mechanics. To validate the chosen input parameters, this study compares two different approaches for static nonlinear modelling, the Finite Element Method (FEM) and the Equivalent Frame Method (EFM), for a simple masonry building. The two methods are compared using the guidelines from Part 3 of Eurocode 8. This study identifies the advantages and disadvantages of various modelling approaches based on the results obtained. The results are also compared in terms of capacity curves and damage distributions for the simple case study of a masonry building created to compare numerical methods. Subsequently, nonlinear pushover analyses with ABAQUS (FEM) were performed on the North Tower of Monserrate Palace, Portugal, in which the material parameters were calibrated by considering the results of dynamic characterisation tests conducted in-situ. Regarding the circular body of Monserrate Palace, the damage distribution of the structure is analysed in detail, aiming to contribute to the modelling of such structural configurations through the Equivalent Frame Method.

Seismic performance and cost comparison of RC moment resisting and dual frames using UBC 97 and IBC 2021

The transition from the Uniform Building Code (UBC-97) to the International Building Code (IBC-21) marked a major shift in the definition of seismic hazard. The term “seismic hazard” in the form of peak ground acceleration (PGA) is replaced by spectral acceleration. This paper investigates the effect of using new seismic hazards on the structural performance of reinforced concrete (RC) buildings. It also looks into the financial impact on the capital costs of new buildings. Useful insights are made to understand the structural performance and financial impact of adopting IBC 21 for structural design in contrast to UBC 97. This study was carried out from the perspective of a developing country, Pakistan. Reinforced concrete moment resisting and dual frames are used as the main structural system of a typical 7-story residential building to investigate the aforementioned effect. The frames are assumed to be located in two locations with high and low seismic hazards. The effect on structural performance is investigated via nonlinear pushover analysis. Financial impact is judged mainly through cost estimation for steel and concrete. A detailed discussion is also presented on the seismic design guidelines in both codes.

Drift damage limit estimation based on cracks of concrete gravity dam considering dam-foundation interaction

ABSTRACT This study focuses on estimating the drift limits associated with different damage states of concrete gravity dams, emphasizing the role of cracks along the dam base and the interaction between the dam and its foundation. Employing a comprehensive framework and nonlinear pushover analysis, the research accounts for uncertainties in concrete and foundation material parameters, evaluating three distinct models with varying height-to-base width ratios (1, 1.25 and 1.5) through 20 runs based on central composite design. The findings indicate that as the height-to-base width ratio increases, the concrete gravity dam demonstrates greater resilience against lateral movements, highlighting its ability to withstand larger drifts without incurring damage. Additionally, the study’s proposed mathematical model accurately predicts the drift limits across different levels of damage, facilitating a comprehensive understanding of the structural behavior and its implications for seismic risk assessments. The research underscores the significance of considering the varying degrees of damage and their impact on the concrete gravity dam’s operational capability and safety, offering crucial insights for ensuring the integrity and stability of these essential infrastructures.

An Innovative Retrofitting Technique of an Industrial Prefabricated Building Without Evacuation

This paper presents a seismic retrofit of an industrial-type precast reinforced concrete building structure using friction dampers. The project consisted of retrofitting two precast reinforced concrete buildings, one of which will be presented in this paper. Precast concrete is one of the industrial structures' most preferred construction methods due to its low cost, fast construction, and availability in rural areas. Unfortunately, most structures constructed before “Specification for Buildings to be Built in Seismic Zones(TBDY 2018)[5]” are not sufficiently engineered and are expected to perform poorly when exposed to a significant seismic event. The general characteristic of precast reinforced concrete buildings built before TBDY 2018 is their relatively high concrete quality (compared to cast-in-place reinforced concrete buildings) and better reinforcement workmanship. But they have some characteristic weaknesses as well. Weak beam-column connections, high drift ratios due to heavy beams, instability problems, and lack of frame behavior can be considered primary weaknesses. General classical retrofitting techniques include increasing beam/column sections or adding new reinforced concrete or steel members to the system or FRP(fiber-reinforced polymer) wrapping. Mostly classical retrofitting needs additional foundations. All these techniques require a long construction period, causing evacuation and stopping building usage. Because stopping the production cost can be tolerated by the owners, a retrofitting approach that can be assembled during the normal function of the industrial structures is required. As a result of this requirement, friction dampers are selected as the supplemental energy dissipation device. ASCE 41-17 [10] is employed for the building's damper design and performance evaluation. Before the damper study, some instability and weak connection problems are solved by traditional strengthening measures. The most effective damper configuration and capacities are selected after an iterative trial-and-error linear study using the simplified methods developed by PROMER. Nonlinear push-over analyses are conducted after linear prestudies. Finally, a nonlinear time-history analysis is performed for confirmation of the results. , It is shown that the proposed retrofit scheme satisfies the desired performance goals for both DBE and MCE events. Overall, it is considered that the proposed retrofit scheme with dampers provides the optimal solution for the Project stakeholders from a performance, design, constructability, and economic point of view. Some application photos will be presented, and methods will be explained in detail in the paper. The friction damper behavior is based on the rotational friction hinge concept. The dampers increase building damping, causing a decrease in earthquake demand. As a result, dampers provide passive energy dissipation and protect buildings from structural and nonstructural damage during moderate and severe earthquakes.

Experimental Investigations on the Residual Performance of Earthquake-Damaged Low-Rise-Reinforced Concrete Shear Walls

This study investigates the seismic residual performance of reinforced concrete (RC) shear walls with different levels of earthquake damage through reversed cyclic loading tests. The test specimens include slightly damaged walls, moderately damaged walls, and repaired specimens after moderately damaged walls. From the test and analysis results, it is evident that the residual strength and deformation capacity of slightly and moderately damaged RC shear walls do not decrease compared with the undamaged wall. However, the residual stiffness and energy dissipation capacity of damaged walls significantly decrease. The test results are also compared with the reduction factors for residual stiffness, strength, deformation capacity, and energy dissipation capacity in the FEMA 306 and JBDPA post-earthquake assessment guidelines to assess their applicability. Additionally, this study proposes a simplified model to describe residual lateral capacity curves of damaged RC walls at different damage levels for nonlinear pushover analysis, allowing engineers to easily convert the capacity curves of undamaged walls to damaged ones.

Seismic Performance of Infilled Reinforced Concrete Frame with Crumb Rubber Mortar Wall Panel

In this paper, the seismic performance of reinforced concrete (RC) frames with crumb rubber mortar wall panels is reported. The tests of the crumb rubber mortar were conducted to obtain model parameters for equivalent diagonal compression struts. With a higher percentage of sand replacement by crumb rubber, the unit weight, the compressive strength, the tensile strength, and the modulus of elasticity of the crumb rubber cement mortar are decreased. Nonlinear pushover analysis of a simple frame shows that the RC frame with a wall panel with less crumb rubber demonstrates lower lateral deformation ability. The failure modes are affected by the amount of crumb rubber and are dependent on the modeling choice of the equivalent compression strut as the wall panel representative. Finally, the seismic performance of the RC building was studied by the equivalent static approach to explore the influence of the crumb rubber mortar wall panels on internal forces and deformations of the frame. With a higher percentage of crumb rubber, the weight of the infill wall panels and the overall weight of the building are reduced, which meets lower seismic base shear demand. This benefit is, however, traded off with higher lateral deformation and also higher inter-story drift of the studied building frames. Doi: 10.28991/CEJ-2024-010-02-09 Full Text: PDF

Photogrammetry-aided numerical seismic assessment of historical structures composed of adobe, stone and brick masonry. Application to the San Juan Bautista Church built on the Inca temple of Huaytará, Peru

This research presents a cost-effective surveying methodology to assist the seismic assessment of complex heritage buildings, based on terrestrial structure-from-motion (SfM) photogrammetry. The method was applied to the study of the seismic performance of the church of San Juan Bautista – Inca temple of Huaytará, Peru, an emblematic case study due to its complex architecture and coexistence of different construction materials. The geometrical model for the seismic assessment was developed with an error of less than 2 % using SfM photogrammetry. Non-linear static pushover analyses were performed on 3D FEM models of the nave and the towers to evaluate their individual response under seismic loading. Mechanical properties of different structural materials of the church were evaluated based on laboratory experimental tests on mortar and adobe, contemporary and ancient fired brick, Inca stone, colonial stone and rubble stone units. Non-linear pushover analyses were conducted in four directions perpendicular to the perimeter walls, and the response of the structure was compared with the seismic demand specified in Peruvian Standards. The simulations show that damage-prone areas are the western and eastern facades, with cracking at the connections between orthogonal walls, as well as at the interface of adobe masonry with Inca stone masonry. The towers exhibit similar seismic response, with lower strength capacities compared to the main nave. In this case, flexural overturning mechanisms and cracking at the interface between stone and adobe masonry were observed. The displacement-based seismic assessment using the N2 method shows that a peak ground acceleration of 0.21 g could lead to the collapse of the north and south facades of the main nave. The towers showed a much smaller capacity with PGA leading to collapse of approximately 0.09 g. Overall, this study contributes to the understanding of the seismic performance of the Huaytará-Huancavelica church, highlighting vulnerabilities and providing valuable information for its preservation and future interventions. Future investigations should focus on on-site tests that will allow the estimation of the effect of existing damage on the structural response and their incorporation in the numerical model.

Nonlinear Pushover Analysis of the Influences on RC Footing for the External Elevator Well

Nonlinear Pushover Analysis of the Influences on RC Footing for the External Elevator Well

Slab Reinforcement Contributions to Negative Moment Strength of Reinforced Concrete T-Beam with High Strength Steel at Exterior Beam-Column Joints

Previous studies have revealed that the contribution of slab reinforcement to the T-beam flexural strength in negative moment regions are not negligible for the seismic capacity design. An effective slab width (i.e., effective width of flanged section) has been proposed, within which the slab reinforcement needs to be included in the calculation of the beam nominal flexural strength in negative moment regions. These studies mainly focused on the cases using normal-strength steel in moment resisting frames. However, recently high-strength steel has been widely used in reinforced concrete moment resisting frames in high seismic regions to avoid congestion near beam-column joints. The use of high-strength steel may affect the beam stiffness due to the fact that it will require less amount of reinforcement, and result in a different normal stress distribution compared to the case with normal-strength steel. Therefore, this paper investigates the slab reinforcement contribution to the flexural strength of the reinforced concrete T-beam designed with high-strength steel in negative moment regions at exterior beam-column joints, for which nonlinear pushover analyses were conducted. Beam reinforcement grade was considered as a primary parameter with several other design variables including slab thickness, height, and span length of the beam. Analytical results show that the use of high-strength steel can result in a wider effective slab width than the case of normal-strength steel for calculating the beam nominal flexural strength under the negative moment. Based on these results, new design equations were proposed.

Non-Linear Pushover Analysis Of RCC Framed Structure By Providing Fluid Viscous Dampers At Different Locations

The increasing need of shelter in urban cities due to overpopulated spaces and land inadequacy people are forced to keep space and their needs strictly limited. High-rise buildings are the best solution for providing people spaces for living and to work on. In this age of urban development and rapid modernization the need of high-rise structures is rapidly increasing. As structures have become higher, structural engineering has become more difficult to achieve appropriate stability criteria. In tall buildings, stiffness is the key to sustainability. Fluid Viscous Dampers (FVD) are one of the efficient solutions for tall structures. These are hydraulic devices that, when stroked, dissipate the energy placed on a structure by seismic events. The viscous dampers convert the kinetic energy of the structural movement into heat and then dissipate that energy into the air, thereby obeying the laws of physics through the conservation of energy. To determine effectiveness of FVDs as well as determine best location for FVDs in high-rise buildings subjected to seismic loads, the current research is being carried out.In this study twelve (12) RCC framed structures of 15 storeys of which four (4) are square shaped in plan, four (4) are rectangle shaped in plan with sides of ratio 1.5:1 and the other four (4) are rectangle shaped in plan with sides of ratio 2:1. These three (3) different shaped buildings considered are having approximately same plan area and damper positions. A floor-to-floor height 3m is taken. The buildings are located in Zone III. By using ETABS 2017 software, which helps to analyse and design the models, the analysis method used for this study is the Push Over analysis. This research work presents the results of an investigation on different parameters like Base shear, Modal mass participation, Time period, Storey Drift, Storey Shear and Storey Stiffness.

Nonlinear modelling parameters for performance-based seismic evaluation of existing wood light-frame buildings in Canada

The mechanical behaviour of wood light-frame shearwalls is difficult to explain unless system-level performance is taken into account. Although the behaviour of wood light-frame shearwalls with wood structural panels is consistent with and represented by the behaviour of the panel to framing nail joints, comprehensive seismic evaluation guidelines for Canadian practice are currently lacking. This study presents a critical review of the available literature on the performance-based seismic evaluation of wood light-frame buildings through nonlinear analysis approach. To verify the applicability of these standards in Canada, the procedure outlined in these documents is compared to available experimental testing. Nonlinear pushover analysis is performed on two representative wood light-frame buildings in Montréal and Vancouver. Results are compared, and further discussion is provided on the adequacy of each document to Canadian practice.

Comparative numerical study to simulate masonry with bed joint reinforced repointing

Bed joint reinforced repointing is a retrofitting technique for unreinforced masonry structures that is commonly applied in the Netherlands to repair settlement-induced damage. Using this technique, the bed joints of masonry walls are reinforced with steel rebars that are embedded in a high strength repair mortar. Due to the increase of induced seismic events in the northern part of the Netherlands, an experimental study was carried out at Delft University of Technology to investigate the performance of this retrofitting technique for combined settlement and seismic loading. This paper aims to simulate the experimental results, with a focus on the comparison of different finite element modelling approaches for studying both un-strengthened and strengthened full-scale tested walls. To that end, three different models are investigated – comprising both macro (continuum) and simplified and detailed micro (brick-to-brick) modelling approaches. The bricks and mortar joints are modelled as one homogenous continuum in the macro model, whereas in the two brick-to-brick models these structural components are modelled separately, with the detailed model including interface elements to simulate the brick–mortar bonds. Nonlinear pushover analyses are subsequently carried out using all three modelling approaches, for both monotonic and cyclic loading cases. Based on these analyses, the detailed brick-to-brick model was found unsuitable to simulate the strengthened wall because cracks in the model mainly occur in the form of opening of the brick–mortar bond interfaces, while smeared cracking in the plane stress elements of the mortar joints is very limited. Similarly, the continuum damage model was found to be inaccurate when pre-existing damage in the experiment needed to be taken into account. The continuum damage model also showed lower axial stresses in the rebars, compared with the simplified brick-to-brick model, as the former does not allow for the direct assignment of material properties for the high strength repair mortar in the strengthened joints.

Machine learning approaches for lateral strength estimation in squat shear walls: A comparative study and practical implications

This study investigated the influence of input parameters on the shear strength of RC squat walls using machine learning (ML) models and finite element method (FEM) analysis. The analyses were conducted on the largest currently available dataset of 639 squat RC walls with a height-to-length ratio of less than or equal to 2.0. The findings suggest that ensemble learning models, specifically XGBoost, CatBoost, GBRT, and RF, are effective in predicting the shear strength of RC short shear walls and using Bayesian Optimization for hyperparameter tuning improves their performance. The axial load had a greater influence on the shear strength than reinforcement ratio, and longitudinal reinforcement had a more significant impact compared to horizontal and vertical reinforcement. The performance of XGBoost model significantly outperforms traditional design models such as ACI 318-19, ASCE/SEI 43-05, and Wood 1990. Additionally, reducing the number of input features from 13 to 10, 8, or 6 still yields reliable predictions with high accuracy. The finding suggests that the use of XGBoost models provides not only comparable accuracy to FEM simulations with non-linear pushover analysis but also the first one can predict the lateral strength in the case of incomplete data which could not be done by FEM. A web application incorporating XGBoost model with various input features can provide valuable insights for predicting the lateral strength of squat shear walls in building structures.

Performance-based plastic design of high-strength steel framed-tube structures fused with replaceable shear links

This study proposes high-strength steel framed-tube structures fused with replaceable shear links (HSS-FTSLs) to improve the seismic performance and post-earthquake reparability of traditional steel framed-tube structures. The conventional seismic design commonly uses the capacity design method, which primarily focuses on the ductility of the structures, resulting in localized damage concentrated on individual floors. An improved performance-based plastic design (I-PBPD) method is proposed for HSS-FTSLs based on the energy balance concept, target drifts, and preselected failure mechanisms. The proposed I-PBPD method considers the influence of post-yield stiffness of the structures. The seismic performance objectives for HSS-FTSLs are categorized into four levels, accompanied by the interstory drifts and residual interstory drifts corresponding to these objectives. The capacity curve for HSS-FTSLs is assumed as a tri-linear form to correspond with the failure modes. Three HSS-FTSL prototype structures with various heights are designed through the I-PBPD method. Nonlinear pushover and dynamic analyses were carried out to investigate their seismic performance. The results indicate that the HSS-FTSL structures designed using the I-PBPD method can achieve the expected failure modes and performance objectives under earthquakes of varying intensities, exhibiting exceptional seismic performance.