Pushover Analysis Research Articles

Dynamic Analysis of Force Redistribution in Small Pile Groups Foundation Subjected to Accidental Lateral Loads

Abstract Designing infrastructure always involves considering potential loads. Beyond anticipated loads, accidental ones can occur, as with the Pedamaran II bridge in Riau, where a ship collision damaged its foundation, breaking a pile and cracking the pile cap. However, this did not lead to structural failure, even though over 30% of the piles in the group were damaged. Initial hypotheses suggest that the use of bracing in the existing bridge might have helped redistribute forces. A numerical model was created using Opensees to simulate lateral loading on the shaft of an elevated pile cap, comparing the effects of bracing and no bracing using elastic elements in a simple 2x2 foundation model. The aim was to understand the correct modeling approach for bracing behavior and its impact on load response. Pushover analysis was performed on one of the shafts, with eccentric loading generating forces in both the x and y axes. Results showed that modeling bracing with elastic elements helped evenly distribute forces across rows of piles, with the greatest distribution occurring in the loaded row. The maximum moment occurred at the lowest bracing connection, highlighting the crucial role of bracing in load distribution, and significantly increasing lateral capacity by about 60%.

Assessment of a Force Method for the Resilient Seismic Design of Special Moment-Resisting Steel Frames with Hysteretic Energy Dissipation Devices

In this paper, the authors present the results of nonlinear dynamic analyses of twelve building models designed according to a methodology based upon the force method, capacity design principles and the concept of structural fuses to achieve resilient seismic designs for special moment-resisting steel frames with hysteretic energy dissipation devices mounted on chevron steel bracing. It is demonstrated that the resilient design mechanism previously checked with pushover analyses is also attained for most studied models with nonlinear dynamic analyses using an acceleration record which is compatible with the elastic design spectrum. Also, it is corroborated that the planned second line of inelastic defense is activated if the seismic action surpasses the considered design spectrum. Based upon the obtained results, it is confirmed that it is possible to perform a resilient seismic design for the studied system under the proposed methodology, even for tall and slender buildings. Therefore, the proposed initial stiffness ratio parameters and the global design parameters previously proposed by the authors to use in a code-oriented force method can be used with confidence for the resilient seismic design of this structural system.

Performance Based Seismic Design of Reinforced Concrete Building

A novel approach is devised for the displacement-based design of diverse buildings, enabling them to withstand the seismic pressures encountered. The suggested approach necessitates figuring out the structure's yield and final displacements. These characteristics are derived from rough empirical relationships for the preliminary design. The inelastic demand spectrum corresponding to the estimated yield strength and the ductility capacity is then used to calculate the necessary strength of the structure. The structural strength required is then determined from the inelastic demand spectrum that coincides with the yield strength estimate and the ductility capacity. By converting it into an analogous single degree of freedom system, the method can be used to systems with many degrees of freedom. A modal analysis is performed on a model of the structure based on its preliminary design in order to determine the final design. For forces distributed according to the first mode, a pushover analysis of the structure now provides improved estimations of the yield and final displacements. The needed strength is then more precisely calculated using these improved estimates. To achieve convergence between the estimated and calculated values of the design displacements, it could be necessary to perform iterations. Lastly, to take into consideration the impact of higher modes on high-rise moment-resistant frames and shear wall systems.

Macro-modelling of GFRG infilled RC frames incorporating pivot hysteretic model

GFRG (Glass Fibre Reinforced Gypsum) panels present a viable alternative to conventional masonry infills in masonry infilled RC frames. Based on the experimental study on the lateral load behaviour of GFRG infilled RC frames, it was understood that the GFRG panels enhance the structural performance of the RC framed structure. To delve further into this, numerical modelling of GFRG infilled RC frames with different fillings inside the cavities of the panel was performed using SAP2000. The GFRG panels were modelled using nonlinear layered shell elements, while the interface between the GFRG web and the infill material was represented using multilinear plastic link elements. The monotonic lateral load–deflection behaviour and the in-plane hysteresis response were simulated by performing monotonic and cyclic pushover analyses. The cyclic pushover analysis incorporated pivot hysteretic models for the materials, hinges and links. Validation of the proposed numerical models was carried out by comparing the results with those obtained from the experimental study. Key parameters such as peak load, initial stiffness, stiffness degradation, and energy dissipation were carefully compared to ensure the accuracy and reliability of the proposed model. It was observed that the proposed numerical model was able to capture the monotonic and cyclic load–deflection behaviour and other performance parameters. The numerical model accurately predicted the peak load in the positive direction but overestimated the corresponding value in the negative direction. Moreover, the overestimation observed in the cumulative energy dissipated for all the specimens is relatively minor and does not significantly affect the overall accuracy of the model.

Behavior of Reinforced Concrete Portal Structures With and Without Brick Wall

Indonesia is an area prone to earthquakes. This has a negative impact on building damage and increases the injury/death rate. Buildings have generally been designed to be earthquake-resistant. However, in planning does not consider the presence of a filler wall in the form of a brick wall. This research takes a study of existing buildings in the form of portals consisting of three floors. The portal was analyzed by pushover analysis method and modeled with no walls and with brick walls using seismostruct software. The results showed that brick walls have a significant influence on the behavior of structures, especially in increasing load-bearing capacity.

Seismic Behaviour of Steel Building with And Without Bracing System by Performance Point

Steel structures have been playing an important role in the construction industry in recent years. It is necessary to create a model that performs well under seismic loading. Seismic performance of multi-storey steel framed buildings is designed as per the provisions of the Indian Code (IS 800 -2007). The ductility of the structure can be increased by adding steel support to the structure. There are different types of support for retrofitting. X-brace, diagonal brace, V-shaped brace, inverted V-shaped brace etc. There are many ways to prepare steel supports such as: The frame of the building is designed with or without different types of connections such as diagonal, X-brace, V-brace and inverted V-brace, which will be considered in this study. The performance of each frame was examined by nonlinear static analysis (pushover analysis) using the ETABS-2021 software package. The comparison of braced and unbraced frames was based on the examination of base shear forces, hinge consequences and lateral displacements of different frames. Compare the response curves and performance points of different frames with and without support systems to know the relationship between the various frames involved.

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.

Modeling of Column Shear Hinges in Pushover Analysis and Experimental Validation

Modeling of Column Shear Hinges in Pushover Analysis and Experimental Validation

Investigation of plastic hinge length in high-ductility reinforced concrete shear walls

In this study, the plastic hinge lengths of reinforced concrete (R/C) cantilever shear walls were analytically determined considering various design parameters. Nonlinear static (Pushover) analyses were conducted on R/C shear wall models and their nonlinear behavior was examined using ABAQUS software. In the study, 72 shear wall models with different parameters were analyzed under the influence of vertical and horizontal loads. Parameters whose effects on plastic hinge length were investigated height/length ratio (Hw/Lw), axial load ratio (N/No), and horizontal web reinforcement ratio (ρsh). The load-displacement graphs of the modelled shear walls were obtained. The plastic hinge height of shear walls was determined according to the heights of the deformations in the concrete and longitudinal steel reinforcement in the section when the shear walls lateral load decreased by 15%. The analytical plastic hinge lengths (Lpz) were determined with respect to the location of the yield occurred at the longitudinal steel reinforcement of the shear wall. The observed plastic hinge lengths (Lp) were determined based on the height of observed the crush as of the foundation top level in the concrete shear wall model. The relationship between the findings of this study and empirical formulas in the literature was determined. It was determined that there is greater closeness between the values obtained from empirical formulas in the literature and the observed plastic hinge length values. It was observed that the plastic hinge length generally increases as the shear span increases. It was observed that the change in ρsh was not a very effective parameter in plastic hinge formation. As the N/No decreases, the plastic hinge length values ​​ generally increase. The Lp/Lpz ratio varied within the range of 0.15-0.50. In addition to ductility (μ) values were determined by using the displacements determined according to both the crushing occurred in the shear wall concrete and the yield observed in the steel reinforcement. The observed that the ductility value depends more on Hw/Lw ratio as N/No ratio decreases.

Seismic Assessment of an Old Historical Unreinforced Masonry Power House Building

Abstract Design of unreinforced masonry buildings is a major concern in seismically active zones in Nepal. The ChandraJyoti Jalvidhyut Power House, a historical landmark in Nepal, represents the nation’s pioneering effort in hydropower generation and signifies its rich cultural heritage. This study comprehensively assesses the structural assessment and seismic performance deficiencies of the ChandraJyoti Jalvidhyut Power House. Material tests on bricks with the individual properties and behaviour of construction materials were done. Utilizing a finite element model in DIANA software V 10.5, the structure’s response under pushover loading conditions is simulated, providing insights into its structural behaviour. Additionally, fragility curves are developed to correlate earthquake intensity with the probability of damage, offering essential information for preservation strategies and seismic risk mitigation. The compressive strength test of bricks, with a value of 9.6 MPa, falls short of the 10 MPa minimum requirement specified by NBC 203:2015, indicating insufficient load-bearing capacity. The building’s pushover analysis shows that the longitudinal direction experiences higher lateral forces (base shear of 945.87 kN) and greater drift ratios exceeding 0.4%, which increases the likelihood of cracks compared to the transverse direction (base shear of 826.77 kN). The analysis also highlights significant nonlinear behavior in both directions, with maximum roof displacements of 35.18 mm (transverse) and 34.4 mm (longitudinal), reflecting the impact of structural irregularities.

Effect of Infilled Frames on Reduction Factor (R) for RC Irregular Structure

Investigating the modification factors as a critical seismic design tool, delineating the anticipated level of inelastic behavior within structural systems during seismic events. Both damping and ductility are included in this factor, particularly at movement nearing maximum capacity. Moreover, it offers valuable insights into buildings' response during earthquakes and the anticipated behavior of structures compliant with building codes during design earthquakes. Essentially, it mirrors the structure's capacity to dissipate energy via an inelastic mechanism. In this research, the infill (RC) structures with various structural irregularities were focused. The selected irregularities included dimension, elevation, and mass. Infill location, number of bays, and seismic zone were the expected R factors for RC frames. Non-linear static pushover analysis was adopted in numerical simulation. The available data gathered from the literature was used to validate the outcomes of the developed models. Additionally, the effects of different types of soil were taken into consideration, and the research results demonstrated that the value of the modification factor (R) for change in stiffness and mass of high-rise buildings for bare and infill (RC) structures is less compared to irregular (RC) structures. It was concluded that the same structure with different types of soil and different parameters has a great effect on the value of R for bare and infill regular and irregular (RC) structures. Furthermore, recommendations for accurate R estimation for RC structures were discussed. Doi: 10.28991/CEJ-2024-010-08-09 Full Text: PDF

An Investigation of Seismic Behaviour of Prestressed Concrete Frame Structures using Pushover Analysis

Abstract: The prestressed concrete system is a prominent material in civil engineering, with applications ranging from buildings, bridges, foundations, piling, silos, stadiums, roadways, and other infrastructure. However, this work is primarily concerned with its applicability to building frame constructions subjected to seismic loading. The prestressed concrete system for frame constructions not only reduces the amount of structural components, but it is also a cost-effective technology that provides outstanding strength and stiffness, as well as quick and simple site erection. Hence, we will be able to use these prestressed concrete components to their full capacity, unlocking engineering and social benefits that were previously impossible. Prestressed concrete designs, as opposed to reinforced concrete designs, can give structures with substantially longer spans, no cracks, or fewer cracks with tiny crack widths. Nonetheless, research on the seismic behaviour of prestressed concrete frame structures is relatively restricted, with the majority of studies focusing on reinforced concrete structures. Finally, the provisional versions of modern building codes such as ACI 318, GB50010, and EC2 do not provide thorough processes for seismic design of prestressed concrete structures. In this work, the seismic design and behaviour of prestressed concrete building frames are explored using the most recent design code. Three model-building codes will be investigated and compared, including ACI 318- 14, Eurocode 2004-2, and Chinese GB500010-2010. The 10-story prestressed concrete frame system is subjected to gravity and seismic loading, and the strong-column weak beam mechanism is archived to conform with the newly implemented building design code. To examine the behaviour of prestressed concrete frame structures, nonlinear static pushover analysis is used to capture the reaction under earthquake loading. The stiffness and strength needed will be designed in compliance with the three major building codes indicated. In addition, the finite element model will be created using CSI Sap200 to capture its actions.

Parametric seismic fragility model for elephant-foot buckling in unanchored steel storage tanks

The parametric seismic fragility model of elephant-foot buckling (EFB) in the tank wall of the unanchored storage tanks is introduced by utilizing the results of a parametric study of eighteen tank-soil configurations. The model can be used to rapidly assess the seismic vulnerability to EFB for a larger number of tanks. The parametric study involved a 1D cloud-based soil response analysis to relate the ground-motion intensity measure at the bedrock with that at the free surface, and a pushover analysis of the refined finite element model of the tank to assess the engineering demand parameter in terms of axial compressive stress in the tank wall and the critical value that triggers EFB. As a consequence, the parametric seismic fragility model can be applied to intensity measures at the bedrock, as it is demonstrated for the spectral acceleration at the tank’s impulsive period, Se,bedrock,EFB, and the peak ground acceleration, PGAbedrock,EFB. The input parameters of the introduced seismic fragility model are the harmonic average shear-wave velocity in the top 30 m of soil, Vs,30, the slenderness ratio of the tank, H/R, the ratio between radius and wall thickness of the tank, R/t, and the standard deviation of log values for the intensity measure causing EFB. The model reliably predicts the median intensity measure causing the onset of EFB in the investigated tank-soil configurations, especially when Se,bedrock,EFB is selected for the intensity measure. However, further investigation is required to enhance the accuracy of predicted intensity measures that trigger EFB by considering the dynamic impact between the base plate and the foundation during an earthquake and accounting for the complete soil-structure interaction effects.

Investigation of seismic resistant structures with various moment-resisting frame systems and pushover analysis

Earthquakes are a serious threat in the construction of multi-storey buildings in Indonesia, which are divided into several seismic design categories. The design of seismic-resistant buildings requires the management of plastic hinges to reduce seismic loads. The aspects of seismic-resistant structural design in Indonesia are regulated by SNI 1726:2019, SNI 1727:2020, and SNI 2847:2019. Intermediate Moment Resisting Frame System (IMRFS) and Special Moment Resisting Frame System (SMRFS) are used based on seismic category and earthquake intensity. Pushover analysis is used to analyze the structures behavior when exposed to seismic loads. This research designs seismic resistant structures with IMRFS and SMRFS at different locations with the aim of assessing structural performance and gaining reinforcement to the concrete ratio, which is relevant for the design and construction of multi-storey buildings in Indonesia. The results of this research are the structural performance levels, reinforcement volume, concrete volume, and the reinforcement to concrete volume ratio. Both IMRFS and SMRFS reached Immediate Occupancy to Life Safe performance levels after the earthquake because their monitored displacement was not significantly different. The structural failure modes of both systems meet the Strong Column–Weak Beam requirements. The distribution of plastic hinges also remains in the Immediate Occupancy category.

A Critical Evaluation of the Coefficient Method, Capacity Spectrum Method and Modal Pushover Analysis for Irregular Steel Buildings in Seismic Zones

A Critical Evaluation of the Coefficient Method, Capacity Spectrum Method and Modal Pushover Analysis for Irregular Steel Buildings in Seismic Zones

Cyclic behavior and pushover analysis of large scale two-bay, two-story reinforced concrete frames infilled with walls with openings

This study presents experimental results on the seismic behavior of a large-scale two-bay, two-story RC frame with RC infill walls, including openings typical of low-rise RC row buildings in Taiwan. The test findings indicated that the specimen failed due to the failure of the vertical members of the first story. Specifically, the critical wall segments located between openings and between an opening and a boundary column and short columns resulting from the presence of these openings were shown to be the main contributors to the failure. Based on the observed phenomenon during the test, an analytical model was verified and proposed for the tested specimen’s pushover analysis. The selection of plastic hinges in the analytical model was determined according to the Taiwan Earthquake Assessment for Structures by Pushover Analysis (TEASPA). Pushover analysis performed by commercially available software indicated that the analytical model could well capture the specimen's behavior regarding peak base shear, initial stiffness, displacement of each story, and development of plastic hinges.

The extended consecutive modal pushover (ECMP) procedure for the seismic assessment of tall dual steel concentrically braced-moment resisting systems and concentrically braced frame (CBF) buildings

The contribution of higher modes to the seismic responses of tall buildings is substantially significant. In recent years, enhanced pushover analyses, developed to account for the effects of higher modes in predicting the seismic demands of tall buildings, have been mostly conducted for moment-resisting (MR) frame buildings. The question is whether these methods can accurately estimate the seismic demands of tall concentrically braced frame (CBF) buildings. Hence, this paper aims to extend the consecutive modal pushover (CMP) procedure for estimating the seismic demands of tall dual concentrically braced-moment resisting systems (CB-MR dual systems) and CBF buildings. In the extended consecutive modal pushover (ECMP) procedure, single-stage and two-stage pushover analyses are performed. Also, the modal properties of the structure are used to modify the displacement increment during the stages of the two-stage pushover analysis. Enhanced pushover methods, including the modal pushover analysis (MPA), modified consecutive modal pushover (MCMP), Extended N2, single-run multi-mode pushover (SMP) and modified upper-bound pushover (MUB) methods as well as the first-mode pushover analysis are implemented for the purpose of comparison. The seismic demands obtained by the pushover methods are compared to those from the most accurate nonlinear response history analysis (NL-RHA). The results demonstrate that although the degree of contribution of higher modes to the seismic demands at the upper storeys of the CB-MR dual systems and CBF buildings is less than the MR frames, this effect should be considered in estimating the seismic demands of this type of mid-rise and high-rise buildings. Furthermore, the ECMP method provides accurate storey drifts for almost all of the CB-MR dual systems and CBF buildings.

ANALISIS KINERJA STRUKTUR PADA GEDUNG BERTINGKAT DENGAN ANALISIS PUSHOVER BERDASARKAN ATC-40

Indonesia is an area prone to earthquakes. Earthquakes can cause infrastructure damage and casualties. Efforts are needed to reduce the risk of earthquake hazards by strengthening earthquake-resistant infrastructure. The design procedures for earthquake-resistant buildings are carried out using a performance-based design approach. Building performance can be estimated through non-linear static pushover analysis. This research takes a case study in Jongke Market, Surakarta. This research aims to determine the capacity curve, performance level, and structure collapse mechanism. The method used is pushover analysis with the capacity spectrum. The result of this analysis is a capacity curve that processed to determine the level of structure performance referring to the drift ratio limitation table in the Applied Technology Council (ATC-40). Based on the results of this research, displacement that occurred in the x direction is 92 mm and in the y direction is 77 mm. Building displacement is good because the displacement that occurred is smaller than the displacement limit (control). The total maximum drift in the x direction is 0.007 and in the y direction is 0.006. The maximum inelastic total drift in the x direction is 0.005 and in the y direction is 0.004. Based on the drift ratio limitation table in the ATC-40 document, this building has an immediate occupancy performance level. Based on the plastic hinge mechanism formed, the existing structure also meets the ideal collapse concept (strong column-weak beam).

Seismic retrofitting optimization model using fiber-reinforced polymer jacketing and NSGA-III

Fiber-reinforced polymer (FRP) is widely used for retrofitting structural elements due to its easy application. However, establishing a retrofit strategy is challenging due to conflicting objectives, such as cost and performance level, requiring optimization for effective decision-making. This study proposes a many-objective optimization model for seismic retrofitting using FRP and the Non-dominated Sorting Genetic Algorithm (NSGA)-III. The model's efficacy was demonstrated through two numerical examples: a reinforced concrete building retrofitted with FRP jackets and a masonry-infilled reinforced concrete building retrofitted with FRP bracings. Each example included three objective functions and multiple constraints. Nonlinear static pushover analysis provided optimal strategies to enhance base shear and energy dissipation while minimizing costs and retrofitting locations. Among the Pareto-optimal solutions, the optimal solution with the minimum Euclidean distance was selected. NSGA-III offered a wider distribution and more Pareto-optimal solutions compared to NSGA-II, demonstrating its potential in addressing many-objective problems related to retrofit decision-making.

Non-linear response of confined concrete beam-column structures under horizontal loading

In this study, a behavior law for confined concrete is considered with the introduction of transverse reinforcement to increase the compressive strength of concrete, using the model of Mander et al. This model integrates the confinement effects provided by transverse reinforcement, enhancing the load-bearing capacity of concrete under compressive stress. A pushover analysis is carried out on a full-scale, four- levels structure, using the N2 method. This advanced technique combines non-linear static analysis with inelastic response spectra. Using this approach, the structure's seismic performance can be estimated, accounting for its ductility and the non-linear effects at each loading stage. The inelastic response spectra are adjusted using reduction factors based on the structure's capacity to dissipate seismic energy through inelastic deformations. By varying the confinement rate of the concrete sections, different performance points of the structure can be obtained. The confinement ratio is a crucial parameter influencing the ductility and strength of confined concrete. Closer spacing of transverse reinforcement increases the confinement ratio, which improves the concrete's deformation capacity and ultimate strength. The results show the effect of the behavior law used to consider concrete confinement on the performance points of the structure. In particular, it is observed that increasing the confinement leads to significant gains in the strength and ductility of the structure. These results highlight the importance of optimally using transverse reinforcement to design structures that ensure their performance and safety under seismic loads.