Pushover Method Research Articles

Analiza postupnog guranja za procjenu seizmičkih zahtjeva okvira s eliptičnim vezovima

In this paper, an innovative steel bracing system, known as the seismic response of elliptic braced moment resisting frame (ELBRF), is evaluated. ELBRF has a better structural behavior comparing to the other bracing systems and it has an architectural advantage allowing to place openings in walls with less interference. The demand for seismic performance of ELBRF is estimated through different loading patterns by adopting the conventional pushover methods. The pushover results are verified through nonlinear time history analysis (NTHAs) of 3, 5, 7, and 10-story ELBRF frames, which are on type II soil and are affected by 10 scaled earthquake records. These results are also with special moment resisting frames (SMRF) and X-Braced CBF and Inverted V-Braced CBF concentrically braced frames. Story drifts, displacements, and story shears are evaluated. A proportionally accurate estimation is observed through the pushover methods in comparison with NTHAs. Modal Pushover Analysis (MPA) can estimate the seismic demands by overcoming the shortcomings of FEMA load distributions when the higher mode effects are of concern. The seismic performance of the ELBRF system against earthquakes has improved, failure is transmitted to the upper stories, and the response modification factor is increased in ELBRF.

Push-over Analysis of Optimized Steel Frames

The traditional optimization methods are effective when dealing with small-scale problems. However, for large-scale problems, these methods fail to obtain optimal solutions, and after a long operation, several solutions are obtained. New methods, known as metaheuristics, have provided new implementations to be used in many applications. They have enabled the resolution of many complex industrial and technical problems. They have the merits of avoiding local optima and finding optimal solutions, due to their ease of understanding, flexibility, adaptation simplicity, and ability to get out of local optima traps. This article aims to model a 2D metal frame gantry with two spans and two levels already optimized by ROBOT Millennium software in order to show the effect of structural optimization in the pre-design phase and of obtaining its non-linear behavior by the pushover method. Three optimal dimensional configurations of this gantry were taken into account and the best was chosen, one which satisfied an adequate behavior in the non-linear domain while respecting the CM66 and Eurocode3 regulations.

Study on mechanism and influential factors of progressive collapse resistance of base-isolated structure

The progressive collapse of the structure caused by the partial failure of the structure will cause severe consequences and massive losses, and structural progressive collapse resistance has always been a hot topic of current research. In order to study the progressive collapse mechanism of base-isolated structures, the test study and numerical simulation of the base-isolated structures were carried out based on the vertical Pushover method and analysis of the variation rule of the capacity of the remaining structure and influence mechanism. The isolation bearing failure position, the size of the beam of the seismic isolation layer, the type of the isolation bearing, and the horizontal stiffness of the seismic isolation layer on the capacity of the remaining structure were compared and analyzed. The results show that the non-uniformity of the beams and the concentrated loading at the nodes were easy to form a linear catenary mechanism, resulting in more severe beam end damage than mid-span damage. In the case of side isolation bearing failure, due to the lack of sufficient lateral restraint, the capacity was significantly lower than other conditions, which were more likely to cause partly collapse. Therefore, setting more transfer paths to improve the structure’s resistance to progressive collapses was necessary. Increasing the size of the beam of the seismic isolation layer could improve the capacity of the remaining structure of the alternate load path in the base-isolated structure. The changes in the horizontal stiffness of the seismic isolation layer and the type of the isolation bearing have little effect on the progressive collapse resistance capacity of the remaining structure.

Visual Multimedia Intelligent Computing System for Seismic Performance of Bridge Structure Based on Object-Oriented Technology.

In order to further promote the standardization of seismic performance design of bridge structures, one must ensure the quality of bridge design and improve design efficiency. First, based on the basic principle of the probabilistic pushover method, the randomness of the structural pushover curve is attributed to the randomness of plastic hinges. Second, the visualization of seismic performance of bridge structures based on the object-oriented technology is adopted. So that the randomness of seismic action can be considered in the analysis of seismic performance. Finally, the limit state equation of the seismic performance of the structure is used to evaluate the reliability of the seismic performance of the bridge in each limit state conveniently. The results show that the failure probability of the structure in each limit state is less than 0.5 under different basic accelerations from 0 to 0.4 g. The software method is simple in calculation and has a strong adaptability, avoiding the difficulty of seismic reliability analysis caused by large-scale simulation and large amount of calculation of traditional structures. Therefore, this method can be easily applied to the probabilistic analysis of seismic behavior of bridge structures under large earthquakes without evaporative deformation failure criterion.

Seismic behavior of reinforced concrete buildings using chained masonry walls randomly located

The widespread use of masonry infill walls in the most prone zones to earthquakes, for the execution of multistoried reinforced concrete buildings, as well as the recorded damage caused by earthquakes, have forced us to study their influence on the seismic behavior of these buildings. The distribution of masonry infill walls in these buildings is mainly related to their architectural requirements. The purpose of this article is to assess the influence of the various locations of chained masonry walls, which represent a particular type of masonry infill walls without gaps, on multistoried reinforced concrete buildings. This variation has been studied using the SAP finite element software, by the pushover method, analyzing several two-dimensional multistoried reinforced concrete frames infilled by double-leaf hollow brick walls. The proposed frames have been analyzed by varying the position of the chained masonry walls, based on the seismic criteria of the period, elastic base shear, elastic lateral displacement, ultimate base shear, and initial stiffness. The results were compared according to the above criteria. After comparing the results, it is very clear that the position of the masonry walls has a great influence on the seismic response of the reinforced concrete frames. Therefore, it is very important to take into account the position of the infill in the design phase.

Seismic performance indicator and seismic performance levels of rectangular underground structures

The classification of structural performance levels and quantitative definition of performance indicators of underground structures are important parts of performance-based structural seismic design. Four typical underground rectangular reinforced concrete frame structures with different cross sections are taken as the research object, and their seismic performance is analyzed through the pushover method in this study. According to the seismic response characteristics and the failure law, it is determined that the central column is the control section in the seismic performance. Then, based on the capacity curves of these control sections, the performance indicator and the performance levels are determined. Subsequently, through a series of seismic capacity analyses considering the variations in structure type, site condition, structural material property and burial depth, the limits of the structural performance indicator under different performance states are analyzed, and a quantitative division plan of structural performance levels is proposed.

A new modal lateral load pattern for improving pushover analysis to estimate nonlinear responses of structures

ABSTRACT Pushover analysis is a nonlinear procedure that is widely used as the primary tool for the nonlinear analysis of structures. In the conventional pushover method, the fundamental mode of the structure is selected as the dominant response mode of the multi degree of freedom (MDOF) system while neglecting the influence of higher modes. It has been proved that for many structures, higher vibration mode effects should be considered to boost the outcomes of the pushover analysis. In this study, a new Modal Load Pattern (MLP) is developed to improve pushover analysis procedure in estimating nonlinear responses of structures. For this purpose, MLP is defined by the directed algebraic combination of the weighted vibration mode-shape vectors of the structure. The weights of modes are determined using an optimisation algorithm such that the difference between the nonlinear responses of the structure under MLP and1 those of nonlinear time-history analysis is reduced to the minimum possible value. Comparing the outcomes of MLP with some well-known lateral load distributions shows that the proposed method increases the accuracy of responses resulting from pushover analysis. It is illustrated that against elastic behaviour, in the inelastic range of structural behaviour, it is likely that higher modes have a significant effect on the optimal lateral load distribution.

Seismic fragility estimates of steel diagrid structure with performance-based tests for high-rise buildings

During seismic performance-based design for building structures, the accuracy of limit states criteria is directly related to its real damage state and retrofitting measures after the earthquake. As a new type of structures, diagrid structure has a special way of bearing force. Firstly, in order to accurately estimate the deformation capacity and energy dissipation mechanism under horizontal loads, four plane specimens of steel diagrid structure are designed and seismic performance-based tests under horizontal quasi-static cyclic load are carried out. Secondly, according to the yield strength and horizontal ultimate deformation capacity of diagrid structure, combined with pushover method, the limit state values of four performance levels of diagrid structure are determined. Finally, the seismic fragility of a diagrid structure for high-rise building is analyzed. The results suggest that the bottom tilted columns have obvious deformation visible to the naked eye before failure, and some failure warnings can be given in advance. It is difficult to realize the “beam hinge” mechanism in diagrid structure, and the cumulative damage of “column hinge” is its main failure mode. The bottom tilted column is the first place where plastic hinge occurs. In addition, the recommended value of inter-story drift ratio for judging the yield of steel diagrid structure is 1/128 by these experimental results, and the recommended value of inter-story drift ratio for collapse resistance is 1/85. Based on these experimental results, the probability of diagrid structure in each performance state can be estimated reasonably and effectively.

COMPARISON OF MRF AND CBF STRUCTURAL RESPONSE TO EARTQUAKE IN OFFICE BUILDING SURABAYA

Indonesia is a country that prone earthquakes. Therefore, knowledge of earthquake-resistant building construction is needed in reducing the risk of damage caused by earthquakes. There are several methods of earthquake-resistant construction planning, one of which is the pushover analysis method. Pushover is a nonlinear static analysis method in which the structure is subjected to gravity loading and displacement-controlled lateral loads which continue to increase through elastic and inelastic behavior until the final condition. One of the popular construction materials in structural planning is steel construction, which has a uniform structure, lightweight, strong, and easy to work with. In modeling earthquake-resistant structures, several popular models are the MRF and CBF models. MRF is a structural configuration model configured on beams that are firmly connected to columns. Based on a rigid beam-column connection, the moment frame cannot be moved laterally without bending the beam or column depending on the connection geometry. Results The case study on the comparison of the two structural models concluded that in the design of earthquake-resistant steel structures using the pushover method, it was found that the MRF structure had higher ductility than the CBF, namely 2.1:1.6.

Influence of soil to structure stiffness on the accuracy of the pushover method for underground structures

The pushover method for underground structures is a seismic analysis method featured by high calculation accuracy and a simple implementation process. The method has been widely used in seismic design and other related scientific research; however, the influence of different soil-structure flexibility ratios on the accuracy of this method is still not well understood. In this study, we select the cross-section structures beneath the Daikai subway station as the research object and establish 12 finite element analysis models with different soil-structure flexibility ratios using ABAQUS. All models are computed by the dynamic time-history method or the pushover method. Furthermore, the dynamic time-history solution result is taken as the standard solution, and the precision and application of the pushover analysis method are discussed based on the parameters of peak interlayer displacement and peak internal force of the middle column section. The results show that the soil-structure flexibility ratio has a significant influence on the calculation accuracy of the pushover method, and the calculation accuracy of this method is the most ideal when the soil-structure flexibility is equal to 1. The research results can provide significant references for the seismic design of underground structures or the improvement of simplified seismic analysis methods.

Comparison of thickness shear wall against drift floor using pushover method

Lateral load or earthquake disaster can damage the structure of a highrise building. Therefore, calculations are needed to avoid massive damage to the structure when an earthquake occurs and give a load to the structure. One of the efforts that is done to resist the earthquake is using shear wall. On this research, there will be a comparison of shear wall thickness that will be used for the building model. Where there is existing model with the shear wall thickness 400 mm, modified model with the shear wall thickness 350 mm and 300 mm, and model without shear wall. Earthquake standards is using SNI 1726-2019, load standards are using SNI 1727-2013, concrete design is using SNI 2847-2019, and for the structure analysis is using ETABS Program. First step is calculating the Demand Capacity Ratio (DCR) of the structure element to determine if the structure needed to be analyse using non-linear static (pushover) or not. And then there will be drift ratio calculation to determine the building performance level using Federal Emergency Management Agency (FEMA) 356 provisions.

Vulnerability study of a two-story reinforced concrete school building structure in Banda Aceh toward earthquakes and tsunami hazards

Banda Aceh city is an earthquake-prone area. One is the phenomenon that a magnitude 9,3 Mw and subsequent tsunami wave occurred in 2004. The incident caused casualties and damage to facilities including educational facilities such as school buildings. After the 2004 Tsunami, affected school was rebuilt in same location as before, therefore necessary to conduct an assessment of school building to ensure safety and comfort of learning process in affected area. The purpose of this study was to determine structure capacity of reinforced concrete school building structure toward earthquake and Tsunami in Banda Aceh, so it can see contruction vulnerability based on table of damage state. Objects in this study was a typical two-story reinforced concrete school buildings in Banda Aceh. The chosen building were SDN 48 and SDN 8. Structures were modelled by using SAP2000 software. Earthquake load data using the 2004 Sumatera-Andaman earthquake and Puskim earthquake-predictions which were analyzed using pushover method, and tsunami loads based on the height of inundation at location of school building. As a results, it has been developed capacity curve and spectrum capacity curve to determine damage limit and probability due to earthquake and tsunami hazards. It was found that based on spectrum capacity curve both school buildings in slight damage, while based on fragility curve it was found that both school building have a risk of light damage and moderate damage. Based on tsunami load, it has been found that both school building has inter-story drift that exceeds allowable limit, and based on tsunami fragility curve both school building were predicted complete damage.

Comparison of Time History and Pushover Methods in Seismic Base Isolated Structures

Sismik taban yalıtımı günümüzde sismik yüklerin sönümlenmesinde göreli kat ötelemelerini azaltarak yapıların daha az hasarla deprem etkilerinden korunmasını sağlayan özel sistemlerdir. Taban yalıtımlı sistemlerde yapıların dinamik davranışında; kat yükseklikleri, sönümleyici özellikleri ve kullanış biçimleri önem arz etmektedir. Taban yalıtımlı yapıların tasarımına ilişkin en kapsamlı analiz yöntemi gerçek deprem kayıtlarının kullanıldığı zaman tanım alanında analiz yöntemleridir. Artımsal tek modlu itme analizi metodu yapıların mevcut kapasitelerinin belirlenmesinde kullanılan, yapının doğrusal olmayan davranışını ve göçme mekanizmalarının belirlenmesinde kullanılan analiz yöntemlerindendir. Taban yalıtımlı yapılarda ise bu metodun kullanımına literatürde çok az kaynakta rastlanılmıştır. Bu çalışmada da taban yalıtımlı yapı türleri arasında farklı analiz yöntemleri kullanılarak karşılaştırmalı bir değerlendirme yapılması amaçlanmaktadır. Bu kapsamında üç farklı sismik taban yalıtımlı yapı modeli tasarlanmıştır. Taban yalıtımında kurşun çekirdekli kauçuk izolatörler kullanılmıştır. Sismik yalıtımlı yapılarda kat yüksekliklerinin ve katlar arasına yerleştirilen sönümleyicilerin etkileri incelenmiştir. Çalışma sonucunda zaman tanım alanında analiz yöntemi ile sönümleyicilerin doğrusal olmayan davranışlarına ait elde edilen verilerin itme analizlerinden elde edilen veriler ile örtüştüğü görülmüş olup, itme analizi yönteminin de sismik yalıtımlı yapı tasarımında etkili bir şekilde kullanılabileceği değerlendirilmektedir.

Simplified Pushover Analysis for Rapid Assessment of Shear-Type Frames

A simplified pushover method for rapidly assessing the seismic capacity of shear-type frames is presented. The frame global force-displacement capacity is described as a trilinear curve passing through three limit states (LS): Damage LS (DLS), Life safety LS (LLS), and Collapse LS (CLS). The global LSs are obtained consequently to the attainment of story-level, element-level, and section-level LSs. All LS capacities are described through closed-form equations. The validity of the proposed method is verified by applying it on several reinforced concrete (RC) frames with a varying number of stories. The results obtained with such an analytical procedure show a good match with those obtained from pushover based on finite element method (FEM) analysis models, in terms of both global force-displacement capacity curves and story displacements at various LSs. The proposed method has the potential to be conveniently applied in large-scale vulnerability/risk assessment studies, where the quality and quantity of the available data call for the use of simplified yet accurate models. More refined models would in fact require significantly heavier computational efforts, not justified by the quality of the results that are usually obtained. The simplicity of the proposed method in such a context is demonstrated through the development of the fragility curves of a five-story shear-type reinforced concrete frame, starting from a predefined set of mechanical and geometrical features characterizing a building typology.

A new pushover procedure for estimating seismic demand of double-layer barrel vault roof with vertical double-layer walls

Recent investigations indicate that pushover methods have been widely applied for the seismic evaluation of common structures, whereas a limited number of researches have been conducted for the pushover analyses of space structures. In this study, a new and an appropriate approach, named the Dynamic Load Pattern-Based Pushover Analysis (DLP-PA), has been proposed for predicting the seismic demands of walled double-layer barrel vault roofs, referred to herein as DLRWs. In this method, invariant lateral and vertical force distributions are obtained by averaging the level forces from linear time history analyses of the space structures for a set of ground motions. In this procedure, the seismic demands are finally obtained by enveloping the results of conventional first-mode and the DLP-PA approaches. Numerical models with different geometric properties have been employed to study the efficiency of the proposed analysis method. The responses of models, using the proposed pushover analysis, are compared with incremental dynamic analysis (IDA) results. Also, the responses have been compared with those of the modal pushover analysis (MPA), extended N2 (EN2), modified consecutive modal pushover (MCMP), a single-analysis multi-mode pushover (SMP) and non-adaptive displacement-based pushover (NADP) procedures. The obtained results demonstrate that DLP-PA approach provide good estimation of seismic demand parameters.

Stability Analysis of Prefabricated Steel Structure Building Based on Pushover Method

Prefabricated steel structure building is a kind of structural system which is widely used in recent years. It is very necessary to study the stability of it by Pushover method. Through the investigation of a building under construction in Hebei Province, China, the finite element analysis software SAP2000 is used to establish numerical simulation models of four kinds of staggered truss steel structure, so as to calculate its static pushover performance. It includes base shear-peak displacement curves, performance points and plastic hinge development. The main conclusions are as follows: the terminal shear and displacement of the hybrid staggered truss structure are obviously better than that of the Vierendeel staggered truss structure in the process of pushover. The base shear of the structure can be greatly increased and the overall deformation of the frame can be reduced when the side spans is set up. Until the end of the pushover, there is no plastic hinge on the column, which meets the seismic design requirements of “strong column and weak beam”, indicating that the prefabricated steel structure staggered truss system has good seismic performance.

Mechanical-Analytical Soil-Dependent Fragility Curves of Existing RC Frames with Column-Driven Failures

In seismic risk estimation, among the different types of fragility curves used (judgement-based, mechanical, empirical/observational, hybrid), the mechanical ones have the twofold advantage of allowing a better control over the basic parameters and of representing a validation test of the consistency of empirical/observational ones. In this study, fragility curves of RC frames with column-driven failures are obtained from a simplified analytical pushover method implemented in a simple spreadsheet, thus allowing the user to perform a large number of analyses. More importantly, the proposed method introduces the concept that Limit States at the structural level are obtained consequent to the attainment of the same Limit States at the local level, in the columns’ sections. This avoids using additional criteria, such as interstorey drift thresholds. This simple analytical model allows for rapid development of fragility curves, for any Limit State, of different building typologies identified by a set of global quantities (number of storeys, story heights, number of spans and span lengths) and by a set of local quantities (element sizes, reinforcement, and material properties). It also allows for a straightforward treatment of the influence of the soil class on the fragility curves parameters, which is another critical issue addressed in this work that helps when interpreting some literature results using empirical/observational methods.

The axial capacity of a full height rectangular opening castellated steel beam with steel reinforcement stiffeners

The axial capacity of a full height rectangular opening castellated steel beam with steel reinforcement stiffeners is proven to prevent Vierendeel failure mechanism. The effect is an increase in flexural capacity of the structure. Diameter of the steel reinforcement stiffeners is revealed to have an effect on its strength in resisting axial forces occur in the structure. However, size of the diameter is limited to the strength maximum value of the steel flange section in withstanding the moment force. Using optimal design of the castellated steel structure, this research aimed to find out the increase value of the axial capacity. There were two models of steel structures employed in the study, IWF 200x100x5.5x8 and castellated beam 362x100x5.5x8, both were loaded with axial directions. Analyses were conducted using truss and pushover methods. Results of the study showed an increase in both flexural (36.81%) and axial (60.78%) capacities. The increase in the value of structure capacity mainly influenced by the stiffeners shortened the effective length of the structure.

Seismic Design Assessment of Bridge Piers Location Effect on the Structural Capacity of Supports under Earthquake Action

The objective of this study was to assess the seismic performance of two types of bridges structures under effect of earthquake by using different locations and numbers of piers. The results of D/C ratio showed that simply supported I girder bridge appeared higher structural capacity than continuous box girder bridge which was resisted the seismic demand. Continuous box girder bridge had higher seismic demand and lower structural capacity comparing with simply supported I girder bridge. Commonly, the seismic design for two types of bridges models with increasing of piers numbers was suitable to resist the earthquake action for region type B. The results of non-linear static analysis (pushover method) showed that the increasing of piers numbers had significant effects on the seismic design of bridges structures to increase the displacement capacity, force capacity, and decreasing of seismic demand to reduce the effects of earthquake action on the bridges structural members. The bridge type simply supported I girder had higher capacity in longitudinal direction than continuous box girder bridge. Whereas, for continuous box girder bridge appeared higher capacity in transverse direction than simply supported I girder. The performance points which were based on displacement were decreased with increasing the piers numbers for bridges structures supports.

Elastic-Plastic Seismic Performance for Jacket Platform Based on Improved Modal Pushover Method

Elastic-Plastic Seismic Performance for Jacket Platform Based on Improved Modal Pushover Method