Pushover Analysis Research Articles

Seismic behavior of steel frames with H-shaped damper

This paper investigates the effect of dampers on the seismic performance of steel frames with unequal depth beam-column (UDBC) joints. First of all, the finite element (FE) models of the UDBC joint and steel frame were regenerated by ABAQUS and verified by experimental results. Secondly, the design method for three H-shaped dampers with different web perforation forms (vertical, elliptical, and diamond) was provided. Finally, five steel frames were built using ABAQUS, and pushover analysis and dynamic time-history analysis were performed on them. The results indicated that dampers could decrease the maximum vertex displacement and inter-story shift angle of steel frames with UDBC joints under three seismic waves by 4.47% to 17.17% and 7.71% to 23.88%. The effect of H-shaped dampers was similar to that of T-shaped connectors. Under the action of the Kobe wave and the Qian'an wave, the H-shaped damper exhibited more excellent seismic performance. Compared with frames with T-shaped connectors, the maximum vertex displacement and the maximum inter-story shift angle of frames with H-shaped dampers decreased by 3.44% to 12.39% and 9.55% to 16.15%. The web perforation form of H-shaped dampers somewhat affected the seismic behavior of steel frame structures. Among them, diamond dampers could minimize structural deformation.

Analisa Level Kinerja Struktur Pada Bangunan 12 Lantai Dengan Metode Pushover

There have been many earthquakes in Indonesia, especially West Sumatra. There was a fairly large earthquake, one of which was in 2009 with a magnitude of 7.6 on the Richter scale centered in Padang Pariaman, causing damage to vulnerable structures and loss of life. Therefore, evaluating the seismic vulnerability of buildings before an earthquake occurs is an important step in preventing damage to buildings and loss of life. In this study, a pushover analysis was carried out to determine the level of structural performance. The method used is a 12-storey building where both the existing building and its detailed properties are known, modeled using the Software Structural Analysis Program (SAP2000) Version 23. From the analysis results, the structure of the 12-storey building will experience the first yield point when given the 3rd pushover load, both at in the X-direction and Y-direction and the building structure will collapse when given the 10th pushover load in the X-direction and the 8th in the Y-direction. The performance level of the 12-story building structure is included in the Damage Control (DO) category level for the X-X direction, which means the transition between Immediate Occupancy (IO) and Life Safety (LS). Meanwhile, in the Y-Y direction, the structure is included in the Immediate Occupancy (IO) category level. Thus, in this case the building is still able to withstand the burden of the earthquake that occurred, the building can also be used again when it has received the earthquake load and the risk of human casualties is relatively small.

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

Conservativeness Study on the Seismic Analysis Method for Research Reactor Plant Structure Based on TMSR-LF1

The seismic performance analysis of research reactor plants is crucial for ensuring the safety of the entire reactor system. This paper analyzes the plant structure seismic performance of the 2WMt Thorium Molten Salt Reactor-Liquid Fuel 1 (TMSR-LF1) at the Shanghai Institute of Applied Physics, Chinese Academy of Sciences under the action of frequent earthquakes, fortification earthquakes, and rare earthquakes was analyzed by finite element software PKPM based on the seismic design method of civil code +1°. On this basis, a comparison was made between the seismic responses of structural pushover analysis and elastoplastic time history analysis under the action of rare earthquakes, and the conservatism of these two commonly used methods for elastoplastic analysis was systematically analyzed. The results indicate that the TMSR-LF1 plant structure exhibits well bearing and deformation capacity. It meets the seismic design goal of “no damage under small earthquakes,” “no unrepairable damage under medium earthquakes,” and “no collapse under large earthquakes (using static pushover analysis),” and the critical regions are entirely within the elastic range. Furthermore, the analysis reveals that the elastoplastic time history analysis method produced a significantly higher seismic response than the pushover analysis method, which indicates the conservativeness of the time history method. Therefore, it is recommended to use the elastoplastic time history analysis method to evaluate the seismic performance of research reactor plants under rare earthquake actions. The research in this paper provides important references for the seismic performance analysis of other Class II research reactor plants.

The “M and P” Technique for Damage Identification in Reinforced Concrete Bridges

The seismic damage in reinforced concrete bridges is identified in this study using the “M and P” hybrid technique initially developed for planar frames, where M signifies “Monitoring” and P denotes “Pushover analysis”. The proposed methodology involves a series of pushover and instantaneous modal analyses with a progressively increasing target deck displacement along the longitudinal direction of the bridge. From the results of these analyses, the diagram of the instantaneous eigenfrequency of the bridge, ranging from the health state to near collapse, is plotted against the inelastic seismic deck displacement. By pre-determining the eigenfrequency of an existing bridge along its longitudinal direction through “monitoring and frequency identification”, the target deck displacement corresponding to the damage state can directly be found from this diagram. Subsequently, the damage can be identified by examining the results of the pushover analysis at the step where the target deck displacement is indicated. The effectiveness of this proposed technique is evaluated in the context of straight multiple span bridges with unequal pier heights, illustrated through an example of a four-span bridge. The findings demonstrate that the damage potential in bridge piers can be successfully identified by combining the results of a monitoring process and pushover analysis.

Investigation of reinforcement curtailment in tall lightly reinforced structural concrete walls

SummaryRecent studies have investigated the impact of minimum longitudinal reinforcement limits on the ductility of the plastic hinge region of reinforced concrete (RC) walls, resulting in revised minimum reinforcement limits in design standards. The objective of this research was to investigate the influence of the longitudinal reinforcement distribution or termination rules for the additional reinforcement at the end regions of the wall up the wall height on the response of taller lightly RC walls. A model utilizing a displacement‐based fiber element was developed and validated against tested walls with a range of longitudinal reinforcement contents. Pushover analyses were then conducted on a 20‐story wall prototype to investigate the sensitivity of key design parameters, including axial load pattern, curtailment heights of the longitudinal reinforcement in the plastic hinge region, reinforcement content at wall base, reinforcement strain‐hardening ratio, and the length over which the reinforcement curtailment occurred. The results indicate that the current minimum reinforcement provisions in ACI 318–19 are insufficient to prevent reinforcement yielding outside the plastic hinge region at the wall base.

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.

The Assessment of the Influence of Soil Type on the Nonlinear Seismic Response of a Corroded Reinforced Concrete Portal Frame

Background: Most researchers have focused on the effect of rebar corrosion on the seismic behaviour of reinforced concrete (RC) columns. On the other hand, the influence of chloride corrosion of reinforced concrete in combination with soil type on the seismic behaviour of RC columns has not been investigated. Objective: This paper investigates the influence of soil characteristics on the seismic vulnerability of reinforced concrete structures. The case study in focus is a reinforced concrete portal frame with columns exhibiting corrosion at ground level. Methods: Chloride ingress initiates corrosion and reduces the cross-sectional area of the corroded concrete steel. In addition, this research considers two different soil types, namely rocky and loose, as relevant factors in the analysis. Firstly, the seismic loads are determined according to the Moroccan seismic building code RPS2011. Then, the evaluation of the evolution of the diameter of corroded bars due to chloride induced corrosion is investigated. Finally, pushover analysis is used to determine the location of the performance point on the capacity curve. Results: The study also includes an investigation of the ductility characteristics of corroded reinforced concrete structures and the inter-storey displacement in different soil conditions. The results show that the inter-storey displacement decreases with increasing age of the structure. In addition, it is observed that the base shear force and roof displacement at the point of failure are more sensitive in loose soils compared to rocky soils. Conclusion: The results indicate that consideration of soil type can significantly alter the expected seismic performance, resulting in higher vulnerability values.

Verification of adequacy of structural elements dimensions and Analytical Investigation of structural behaviour of Masonry Infilled and Ferrocement infilled G+2 storied existing structure and through Pushover analysis

Pushover analysis of an existing structure located at Bangalore is carried out to evaluate its available strength. Analysis was carried out in different stages such as modelling for a bare frame structure and infilled with brick masonry and ferrocement with the consideration of openings such as doors and windows. The analysis outcome revealed that the few of the structural members was insufficient to carry external forces for various seismic zone intensities and demanded the retrofitting and thus revision of the structural dimensions were suggested and further analytical studies showed that base shear carrying capacity and displacement parameters significantly affects for different types of infilled materials and bare frames.

Seismic performance factors of quarter-elliptic-braced steel moment frames (QEB-MFs) using FEMA P695 methodology

One of the newest lateral load-resisting systems is quarter-elliptic-braced steel moment frames (QEB-MFs). The elliptical geometry of this bracing system not only resolves the shortcomings of conventional concentrically braced frame systems but also leads to greater energy absorption. The QEB-MF system's seismic performance factors (SPFs) are specified in this paper using the FEMA P695 approach. To this end, a three-dimensional group of 2-, 4-, 6-, and 8-story archetypes in two distinct seismic design categories (SDC Cmax and Cmin) were designed according to presumed SPFs. The adjusted collapse margin ratio (ACMR) for each archetype was calculated utilizing the results of non-linear static (pushover) analysis and incremental dynamic analysis (IDA) under far-field ground motion (FFGM) records. In order to confirm presumed SPFs, ACMRs were compared to FEMA P695's acceptable values. The results indicate that the ACMR values for the QEB-MF systems that were designed with a response modification factor of 6.5 are acceptable. In addition, the deflection amplification factor and the over-strength factor have been acquired to be equal to 6.5 and 2.5, respectively.

Time-dependent seismic fragility analysis of reinforced concrete columns subjected to chloride-induced corrosion

This paper presents a stochastic methodology to perform time-dependent seismic fragility analysis for reinforced concrete (RC) columns subjected to chloride attacks. Numerical modelling methods considering the increasing variability of reinforcement mechanical properties were proposed based on the stochastic constitutive model for corroded steel bars. Depending on the finite element model validated by test data for uncorroded and corroded RC columns, two novel stochastic cases and a traditional deterministic case were introduced and then applied to pushover analysis, incremental dynamic analysis and seismic fragility analysis. The results of damage limit states (DLSs) determined by stochastic pushover curves indicated that the seismic capacity/DLSs for columns along the service life were time-dependent and followed lognormal distributions. The incremental dynamic analysis curves and seismic fragility curves implied that chloride-induced corrosion typically led to a substantial increase in the failure probability of columns. In comparison with the correlated stochastic method, considerable underestimations of component level fragility across different damage limit states were obtained using the deterministic approach, which highlighted the importance of accounting for the variability of mechanical properties of corroded steel bars in the time-dependent seismic fragility analysis.

Seismic performance and vulnerability analysis for bifurcated tunnels in soft soil

This paper investigates the seismic performance of complex comprehensive interchange underground structures. As an example, the seismic performance of Nanjing underground bifurcated tunnels constructed in soft soil is analyzed. A three-dimensional (3D) numerical finite element analysis model is established considering soil-tunnel interaction to analyze the seismic response characteristics and failure mechanism of the bifurcated tunnels. The results show that the tunnel damage degree is closely associated with the deformation response, and that the inter-story drift ratio of the lower layer is significantly greater than that of the upper layer. The pushover analysis method is used to obtain the seismic performance curve of the tunnel, and inter-story drift ratio limits are defined. The IDA procedure is then used to conduct multiple non-linear dynamic time history analyses based on the 3D finite element model, and IDA curve clusters are drawn with peak ground acceleration (PGA) as the earthquake intensity measures and the peak inter-story drift ratio as the damage measures of tunnels. The corresponding IDA percentiles lines are calculated, and the seismic fragility curves of the bifurcated tunnels are established. The post-earthquake functional failure probability of the bifurcated tunnels is obtained under different seismic fortification performance level.

Pushover Analyses of Slender Cantilever Bridge Piers with Strength and Ductility Degradation

Reinforced concrete bridge piers are often subject to spatially non-uniform deterioration which typically produces strength and ductility degradation. When piers are subject to deterioration, the sectional response is no longer uniform and the determination of the pushover curves from sectional response is no longer immediate. This paper proposes a simplified procedure to accomplish this task for RC bridge cantilever piers. The method is simplified only with respect to geometric nonlinearities and yields an accurate estimate of the ultimate displacement, free of numerical issues typical of fiber-based finite elements. The procedure is based on an iterative approach to enforce the element equilibrium under P-Delta effects induced by vertical loads and can consider arbitrary deterioration patterns through the specification of different moment-curvature response along the elevation. After validating the approach with experimental results, a parametric analysis of the influence of sectional strength and ductility degradation is carried out for the case study of a rectangular hollow RC pier. Results show that significant variations of the pier equivalent plastic hinge length can be expected because of the occurrence of deterioration in the lower part of the pier. Moreover, paper provides quantitative measure of the extent of the strength and ductility degradation.

Bidirectional seismic performance and design approach of RC infill wall with PVC tubes

In some regions, masonry infill walls are replaced by cast-in-situ reinforced concrete (RC) infill walls to effectively solve problems such as leakage, long construction periods, and high out-of-plane vulnerabilities. However, these high-stiffness RC infills impose excessively high constraints on the adjacent structural components, leading to disadvantageous seismic responses. Therefore, a flexible connection is required to isolate the infill walls and main structures. However, flexibly connected RC infill walls are not widely used in practical engineering because they are weakly supported by relevant standards and codes and have an insufficient calculation basis, especially for evaluating out-of-plane seismic properties. This study considers a type of RC infill wall with a common layout of polyvinyl chloride (PVC) tubes for coupled shear wall systems. The in-plane and out-of-plane seismic performances of the system are studied using quasi-static loading tests and finite element analysis, respectively. The system exhibits satisfactory seismic properties during the test because the PVC tubes provide effective flexible isolation. Out-of-plane pushover analysis and bidirectional loading are successively simulated with different parameters to study the out-of-plane reliability of the infill walls with and without openings. Finally, a seismic design approach for such infill walls, considering both in-plane and out-of-plane resistances, is proposed and validated using novel and concise design formulas. The accuracy of the design approach is verified using finite element calculations.

Parametric study on seismic response modification factor of strap-braced cold-formed steel systems

While cold-formed steel structures have been extensively studied for seismic-resistant construction, existing regulations, and implementation guidelines do not comprehensively address the impact of key design parameters on the seismic behavior of CFS strap-braced shear wall systems. This study investigates the lateral resistance and seismic behavior factor of strap-braced shear walls and compares them with code values, and tries to fully understand the effect of different design parameters on the seismic R-factor of these systems. The effect of parameters such as the strap cross-sectional area, aspect ratio, and distance between the studs is studied using ANSYS finite element software to create datasets for various configurations. The pushover analysis results obtained from this analysis are utilized to perform incremental dynamic analysis, under a set of 22 ground motion records, to evaluate the seismic response modification factor for different residential buildings. For this purpose, one to four-story residential buildings are designed based on four seismic hazard zones: low, moderate, high, and very high and then, they are analyzed. Results of pushover analysis show that increasing the strap cross-sectional area and aspect ratio increases capacity, but changing the distance between studs does not have a significant effect, and the R factor presented by codes is conservative. Incremental dynamic analysis results also indicate that the behavior of studied buildings varies depending on the structure and selected record and the suggested R factor by codes for diagonal straps braced cold-formed steel structures is acceptable for buildings up to three stories in low, medium, and high seismic zones, and for buildings up to two stories in very high seismic zones. Overall, this study shows that strap-braced cold-formed steel shear walls have the potential to achieve higher seismic R-values in comparison to design codes.

Seismic Resilience of Concrete Moment Frames with Fibrous Rubberized Beam-Column Joints

ABSTRACT Ensuring resilience through rapid buildings recovery in seismic zones has been placed at the forefront of recent studies. However, studies that compare the relative resilience of buildings constructed with different materials are lacking. This paper focuses on a comparative resilience analysis of concrete moment frames where beam-column connections are made with varying types of concrete mixtures. The connections are made with normal strength concrete (NSC), rubberized concrete (RbC), steel fiber rubberized concrete (STFRC), synthetic fiber rubberized concrete (SYFRC), and high strength concrete (HSC). Nonlinear static pushover and incremental dynamic analysis (IDA) are utilized to understand system response and the level of damage sustained following an earthquake. Subsequently, seismic fragility functions are constructed for the five considered frame types. The frames are subjected to different seismic scenarios, and the corresponding losses, recovery time, and resilience are quantified. A comparison between the five frame types is carried out to examine the optimal concrete mixture to be used to reduce damage probabilities, total direct losses, and recovery time and subsequently enhance resilience. The results show that rubberized concrete strengthened with steel and synthetic fibers can reduce economic losses by up to 19% and increase building resilience by up to 37% compared with the frames constructed with normal strength concrete.

Structural Assessment of a Masonry Arch Bridge before and after a traditional inner arch retrofitting technique

To assess the structural behaviour of masonry arch bridge and identify the occurrence of damage reliable numerical models to perform accurate nonlinear structural analyses are needed. The innovative strategy known as Discrete Macro-Element Model (DMEM) is here employed to simulate the performance of a masonry arch bridge before and after a traditional structural retrofitting. The adopted numerical strategy assures a geometrically consistent model characterized by a very low computational burden and reliable results. As case study, a masonry arch bridge located in Maletto (Italy), belonging to the rail network, around Etna volcano, called Ferrovia CircumEtnea (FCE). The bridge has been built in 19th century and was subjected to a structural retrofitting in 1984, because of a light settlement of the central pier due to landslide. The bridge was reinforced with the introduction of a supplemental thin inner reinforced concrete arch, at the intrados of the existing stone arches, externally confined by an external steel corrugated thick plate also used as formworks. In this paper the HiStrA bridge software, where the DMEM is implemented, is used for providing a structural assessment of the bridge in its original configuration and after the structural retrofitting. Both push-down and push-over analyses are performed clearly showing the efficacy of the adopted traditional retrofitting strategy.

The choice of the control displacement in pushover analysis of bridges: a case study

Seismic assessment of existing bridges requires consideration of the structural inelastic behaviour. Non-linear static methods (i.e., pushover) have become a standard tool in civil engineering practice for the analysis of various structural typologies, including bridges, due to simplicity compared to non-linear dynamic analysis. Nevertheless, the extensions of the applicability of pushover methods to bridges seem to show peculiar relevant questions. This work presents a case study of non-linear static analyses of an existing reinforced concrete (RC) highway beam bridge. Among the numerous proposals available, traditional pushover analysis has been chosen as the analysis method. The simply supported beams bridge has a total length of around 706 m, with 16 spans of 43 m each; the simple deck is made of reinforced concrete beams pinned over the multiple stem piers, whose height varies regularly from 11 m to 5.5 m. Non-linear behaviour of bearing devices, soil-abutment interaction system and expansion joints (closure) have been accounted for. The analysis has been performed in both longitudinal and transverse directions, subjecting the structure to the following load distributions: (i) constant along the deck and (ii) one that considers the contribution of the modes according to the response spectrum analysis. The case study seems to confirm the importance of the reference point selection in the bridge seismic assessment via pushover method. The pushover has been compared with the results of dynamic non-linear analysis.

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

Seismic Assessment of RC Frame Structure by Nonlinear Static Pushover Analysis.

Seismic Assessment of RC Frame Structure by Nonlinear Static Pushover Analysis.