Linear Dynamic Analysis Research Articles

Linear dynamic analysis of axially moving cylindrical nanoshells considering surface energy effect with constant velocity

Linear dynamic analysis of axially moving cylindrical nanoshells considering surface energy effect with constant velocity

Investigation of Building having Shear Wall and Bracings using Linear Dynamic Analysis

Abstract: The design and analysis of earthquake resistant structures play importance factor all over the world. Hilly regions such as Ambikapur, Koriya, Dantewada & Jagdalpur district as a part of Chhattisgarh are more vulnerable in terms of seismic collapse structure in recent years and demand of high-rise structures with irregularity as given below is increasing now day due to high land cost & infrastructure there is much need or require of earthquake stability check. The paper is about analysis of different RCC Frames along with different cases of shear wall and X-bracing. The objectives of this paper are to model the asymmetry frame with different cases in respect to location of retrofitting, to examine seismic parameters such as story shear, displacement, compressive stress, story drift in order to check stability and to validate the best suitable location for asymmetry building and finding out their limitation.

Determination of Seismic Performance Factors for Buildings with Concentrically Braced Frame Systems under the Excitation of Near- and Far-fault Records

Performance coefficients are widely used in seismic design codes to achieve performance objectives. The values of these coefficients have significant importance in achieving pre-specified performance goals. Studies have shown that near-fault earthquakes decrease the ductility and increase the risk of failure in the structures; however, the current codes use the same performance coefficients to design structures against near- and far-fault records. In the present study, 1-, 5-, 10- and 15-story special concentrically braced frame (SCBF) structures designed in the region with high seismic hazard have been evaluated. Non-linear static, linear dynamic, and incremental non-linear dynamic analyses under the influence of two sets of near- and far-fault records extracted from FEMA-P695 have been used to calculate the performance coefficients. Furthermore, the fragility curves are calculated for three performance levels (IO, LS, CP) using a probabilistic assessment of the results derived from incremental dynamic analysis to investigate the relationship between obtained factors with the probability of exceedance from a specified level. According to the mean results of all records, the behavior factor for the steel special concentrically braced frame is 5.92. The mean behavior factor obtained for the near-fault records is 35% less than the far-fault records. Differences in the obtained behavior factor for structures under excitation of two types of earthquake records (near- and far-fault) are observed in the fragility curves related to the probability of exceedance from CP level. However, there is no significant correlation between the resulted behavior factors and the probability of exceeding IO and LS levels.

FE modelling progressive collapse assessment of steel moment frames-parametric study

ABSTRACT Progressive collapse is the failure of primary structural components produced by natural or abnormal events that may result in a total or partial collapse of the structure. In this paper, several structure models, under different column removal scenarios, were modeled and analyzed using the FE program SAP2000 to evaluate the effect of span length, the strength of structural members, and cross-section on the steel building’s resistance against progressive collapse. The Alternative Load Path method was carried out using the linear static and nonlinear dynamic analysis following the GSA 2003 guidelines for this investigation. The material and the geometric nonlinearities must be considered in the nonlinear dynamic analysis. The contribution of span length, steel grade, and cross-section to the response of the structural system was studied through the Demand Capacity Ratio for the linear static analysis. The variation of several parameters, such as bending moments, plastic hinges status and their rotations, displacements, and ductility, was discussed based on the response of the nonlinear dynamic analysis. The main objective of this study is to demonstrate the impact of the latter parameters on the structural enhancement and the reduction of the damage level triggered by the failure of a primary structural component.

Seismic Analysis of Historic Stone Structure: A Review Paper

Abstract: This general report is prepared from the selected 25 papers which are in the area of seismic analysis of structures. An earthquake is the result of a rapid release of strain energy storied in the earth crust that generates seismic waves. Structures are vulnerable to earthquake ground motion and damages the structures. In order to take precaution for the damage of structures due to ground motion, it is important to know the characteristics of the ground motion. The most important dynamic characteristics of earthquake are peak ground acceleration, frequency content, and duration. These characteristics play predominant rule studying the behavior of structures under the earthquake ground motion. The earthquake analysis of multistorey structure is done by linear and nonlinear methods. Response spectrum method of analysis is linear dynamic analysis. For nonlinear dynamic analysis time history method is used. In this paper, response spectrum method is used for linear analysis. For nonlinear analysis, time history method is used.

Progressive collapse resistance of cable net structures

This study investigates the collapse resistance of the cable net structures. Compared to conventional structures, the analysis of the cable net structures is rather complicated due to the highly nonlinear behavior of the cables, which leads to large displacements and instabilities during the analysis. In this paper, 24 prototype structures are modeled with various force density levels, span lengths, and the number of spans. Several collapse scenarios, including the cable rupture, column removal, and restrain failure, are defined, and the prototype structures are analyzed considering 168 collapse scenarios. This paper aims to recognize the critical elements, the weak points, and other decisive parameters to protect the cable net structures against progressive collapse. The collapse analysis is performed using a step-by-step nonlinear pseudo-dynamic procedure considering the backbone curve for the elements to accurately model the rupture phenomenon. To verify the numerical approach, the results for one of the pseudo-dynamic analyses are compared against nonlinear and linear dynamic analyses using the Node Relaxation method. Analysis results indicate that the restrain failure is the most destructive collapse scenario for cable net structures. For multi-span cable nets, it is also concluded that the areas around the corner columns are more vulnerable to local damage.

Influence of the P-delta Effect and Stiffness Irregularity on the Structural Behavior of Reinforced Concrete Buildings

In this research, the influence of the stiffness irregularity and the p-delta effect on the structural behavior of a reinforced concrete building is analyzed. The main objective is to determine the impact of the stiffness irregularity and the p-delta effect on the structural behavior in regular and irregular buildings. First, the linear dynamic analysis procedure is performed in order to determine the structural response in terms of drifts, shear force and moments per floor. Subsequently, we proceed with the nonlinear static analysis procedure to obtain the capacity curve of the structure. The post elastic stiffness and the overall ductility of the structure are determined from the capacity curve. Finally, a comparative analysis of the responses from the linear and nonlinear analysis is carried out to determine the percentage variation of the results. When analyzing the structures that consider the stiffness irregularity and the p-delta effect, variations of up to 16.50%, 11.00% and 14.00% have been obtained in drifts, shear force and moments per floor respectively, which are considerable values. When the p-delta effect is considered in structures with the presence of stiffness irregularity, there is a variation in stiffness of up to 59.85%. With this result it is explained that the p-delta effect produces a greater degradation of the overall stiffness of the structure.

Seismic Performance Assessment of Masonary Infilled RC Frames by Using Staad PRO

Abstract: Now a days construction of the RC frame is common because of the simplicity in construction. The masonry walls are mainly used for partition and insulation purposes rather than for structural purposes. However, during the earthquake, this filling contributes to the response of the structure and the behavior of the filling frame is different from that expected for the structure of the bare frame. The fill acts as a compression strut between column and beam. For this purpose, linear dynamic analysis were carried out on the structure of the RC masonry frame to study the influence of the resistance variation of the structure with n without a infill wall, filling effect on dynamic parameters such as the natural period, displacement and state of the hinge. In this rear-end collision effect high building is studied. All analysis are performed by the STAAD PRO v8i software. building modeling and analysis are performed on STAAD PRO v8i. For the analysis the building with G + 10 RCC frame is modeled. In this analysis the width of the strut is calculated manually according to the expression given in the FEMA-356. The infill panels are modeled as equivalent single diagonal struts. Several equations for calculation are considered for these diagonals. In this study the comparison of time verses acceleration , time verses velocity , time verses displacement with respect to the floor is made . The study shows that the influence of filling on the structure is significant. It increases the rigidity of the structure and makes the structure able to withstand a seismic region with respect to the bare frame. Keywords: Infill walls, Seismic force, base shear , STAAD Pro. , Time History, response spectrum.

Some Issues in the Seismic Assessment of Shear-Wall Buildings through Code-Compliant Dynamic Analyses

Due to their excellent seismic behavior, shear wall-type concrete buildings are very popular in earthquake-prone countries like Chile. According to current seismic regulations, the performance of such structures can be indifferently assessed through linear or non-linear methods of analysis. Although all the code-compliant approaches supposedly lead to a safe design, linear approaches may be in fact less precise for catching the actual seismic performance of ductile and dissipative structures, which can even result in unconservative design where comparatively stiff buildings like reinforced-concrete shear-wall (RC-SW) buildings are concerned. By referring to a mid-rise multistory RC-SW building built in Chile and designed according to the current seismic Chilean code, the paper investigates the effectiveness of the linear dynamic analyses to predict the seismic performance of such kind of structures. The findings show that the code-compliant linear approaches (Modal Response Spectrum Analysis and Linear Time-History Analysis) may significantly underestimate the displacement demand in RC-SW buildings. This is highlighted by the comparison with the results obtained from the Non-Linear Time-History Analysis, which is expected to give more realistic results. A set of ten spectrum-consistent Chilean earthquakes was considered to carry out the time-history analyses while a distributed-plasticity fiber-based approach was adopted to model the non-linear behavior of the considered building. The paper highlights how the risk of an unsafe design may become higher when reference is made to the Chilean code, the latter considering only the Modal Response Spectrum Analysis (MRSA) without even providing corrective factors to estimate the inelastic displacement demand. The paper checks the effectiveness of some amplifying factors taken from the literature with reference to the case-study shear-wall building, concluding that they are not effective enough. The paper also warns against the danger of local soft-story collapse mechanisms, which are typical of reinforced concrete frames but may also affect RC-SW buildings when weaker structural parts made by column-like walls are present at the ground floor.

Seismic Analysis of High-Rise Building Having Lateral Load Resisting Elements with and Without Base Isolation

Abstract: In present work linear dynamic analysis of high-rise building is done and of base isolation is analyzed with lateral force resisting elements like shear wall and bracing, effect of all these structural components is calculated and analyzed on structure having 30,35 &40 Stories. Structure is Located in Earthquake Zone IV. Analysis is done with the help of ETABS 19 software. In base isolation we bifurcate the structure from foundation so the structure remains unharmed from shocks and motion at the time of seismic action. Base isolation is awidely used lateral load resisting system provided to strengthen such buildings but literature survey of Base isolation reveals that Lear Rubber Base isolation is proved tobe determinantal. With the increase in urbanisation use of multi stories building is now in trending because of its high utility in commercial as well as residential. In northern part of India, maximum places are susceptible to earthquake so the basics requirement is to build the safe structure so that no damage to the life takes places. One among various methods of earthquake resistant design is Base Isolation. Various studies were carried out to check the behaviour of different parameters like time period, drift, storey displacement and overturning moment etc. with various types of base isolation. Use of LRB isolation system for high rise buildings was suggested. In thepresent study lead rubber bearing is used for base isolation with structure having shear wall and bracings. G+30, G+35 and G+40 storey structure are analysed. Static, linear dynamic (response spectrum) is performed to study the behaviour of building with lead rubber base isolation system. ETABSv2019 is used to perform the analysis and design. Comparison of fixed base building with LRB is shown and suitability concern is provided. It was observed from the study that Lead Rubber base isolation is more effective for earthquake prone zones.

Influence of Beams Distribution on the Dynamic and Seismic Linear Response of RC Frame Buildings

The present study compares the dynamic properties and seismic performances offered by reinforced concrete frame structures characterized by different beams distribution. The understanding of the influence of beams distribution on spatial frames is not only useful when dealing with the seismic vulnerability assessment of existing buildings that may show unusual layouts of beams, such as alternating beams at each storey, but also when facing the design of new buildings with fluid viscous dampers for which some structural flexibility is required. A systematic study is described in this paper. Four (2-, 3-, 6-, and 10-storey) regular frame buildings with rectangular plan are considered as reference structures. Different models are developed according to various layouts of the primary beams, exploring alternatives to the full three-dimensional organisation of beams and frames. For instance: beams placed along the longitudinal direction at the odd storeys and placed along the transversal direction at the even storeys, and vice versa; alternating beams every one and two storeys; beams just placed along one direction. Modal analysis has been conducted to evaluate the influence of beams distribution on the dynamic properties (periods of vibration and modal participating mass ratios). Response spectrum analysis and linear time-history dynamic analysis have been carried out to assess the effects of beams distribution on the fundamental seismic response parameters (shear forces, bending moments, top-storey displacements, interstorey drifts, and floor accelerations). On the contrary of what could be expected, the results indicate that structures with beams alternating every storey may show interesting advantages in terms of reduced total base shear, almost comparable bending moments and accelerations, within a still balanced overall behaviour along the two directions, with respect to the complete three-dimensional frame. Two effects are recognized: the period effect and the static scheme effect. The former acting basically on the storey shear forces; the latter acting mainly on the bending moments.

Study on Dynamic Behaviour of Irregular R.C Framed Structures with Different Location of Shear Walls

In the recent researches it was found to be the most appropriate loads resisting system in recent and present years is shear walls system. In the high rise building shear walls are of the most achievable and hence commonly used lateral load resisting components. It is supplied in building from foundation level to through the height of the building. The scope of the present work is to find the optimum location of the shear walls in plan irregular structures with shear walls such as in I frame, L frame, T frame for different zones in G+17 stories each storey height of 3.2 m, Shear walls are given at corners and at periphery of the building. And also, the outcome of results in seismic zones as per IS CODE 1893(Part1): 2016 has been presented. The seismic analysis performed is linear dynamic response spectrum analysis utilizing the well-known analysis and design software ETABS 18.1.0. Seismic performance of the building has been examined based on specification such as storey displacement, Storey drift, Storey Shear, Base shear, Time period of modes.

Robust flat‐facet triangular shell finite element

AbstractA flat facet finite element with three nodes and six degrees of freedom per node for linear static and dynamic analysis of thick and thin shells is presented. The membrane response is modeled with constant strain triangles. The bending response treats the transverse shear with an improved version of the discrete‐shear‐gap technique. The main novelty of the present approach is the robust treatment of the drilling rotations: the element internally responds to five degrees of freedom per node, but externally it naturally possesses six degrees of freedom per node. The drilling degree of freedom is decoupled from the bending and twisting, and the undesirable user‐selectable arbitrary stabilization is avoided. The element is shown to be robust for extremely thin shells, and passes tests such as the Raasch hook problem. Performance is illustrated with static and dynamic examples including branched and folded shells.

Model updating of a masonry tower based on operational modal analysis: The role of soil-structure interaction

Vibration-based finite element model (FEM) updating of cultural heritage assets is gaining so much attraction these days since destructive tests are usually not allowed to be performed. In this study, a framework for developing three-dimensional (3D) FEMs is proposed using 3D laser scanners and applied on Slottsfjell tower, a stone masonry tower in Tønsberg, Norway. Operational modal analysis (OMA) was done based on the ambient vibration testing (AVT) data to define the frequency values and corresponding mode shapes of the tower. Mechanical properties of the tønsbergite stone were utilized to derive the base values of the material properties of the homogenized masonry for performing sensitivity analysis and FEM updating. To investigate the effect of the soil-structure interaction (SSI) on the FEM updating results, three FEMs are developed. The fixed-base model is the FEM without considering the SSI effects, and two other FEMs are developed using the substructure and direct methods for simulating the SSI effects. Sensitivity analysis was performed to investigate the effective parameters on the dynamic characteristics of the models. FEM updating was conducted on the three FEMs, and results are compared to each other to show the role of the SSI on the FEM updating results. The resonance effect can cause damages to buildings located even in low seismicity zones. For this aim, the risk of resonance effect has been evaluated for the tower. Finally, linear dynamic analysis was performed on the three calibrated models, and the results were compared to each other.

Linear dynamic analysis of high-rise irregular structures with or without LFRS & frictional damper

This study categorically assists in describing the behavior of Irregular structures consist of G + 20 Storey through linear dynamic analysis for seismic assessment of structures. Linear dynamic analysis or response spectrum analysis helps us to evaluate the several parameters in respect of severe responses in irregular structures. At the time of design, A well analyzed structure shows which fragile part of structure needs to give an attention at the time of design to resist and dissipate the energy of seismic force occur on a structur3e during the earthquake. Response spectrum analysis is a seismic analysis method, which shows the response of structure when a seismic load taken into an account. In this study series of sequential response spectrum analysis of High-rise irregular structures have compared with the similar structures after assigning shear walls, Steel bracings and Frictional dampers respectively, and simultaneously all the purposed structure responses have compared with a regular structure accordingly with same consideration of lateral force resisting system. The complete modelling and analysis have done by the prominent analytical FEM integrated software “ETABS” in the seismic zone IV by considering relevant data for the particular seismic zone by IS 1893 (Part-1) 2016. All the reinforcement criteria for the components of structure has been taken into consideration as per suggested by IS 13920 for the ductile design. The response parameter aims for structures due to seismic loading are in terms of Max. displacement, Storey shear. Ultimately, it was concluded that the shear wall is more desirable than the other for reducing the max. displacement with the average reduction percentage of 61.33%.

Dimension-reduction of stochastic wave forces and probability density evolution analysis of wave-excited pile foundation

This paper discusses the reasonable description and simulation of the continuous stochastic wave force field at probabilistic level. Firstly, in order to overcome the challenge of high-dimensional random variables inherent in the conventional Monte Carlo sampling (MCS), the dimension-reduction (DR) simulations of stochastic processes are addressed based on both the non-deterministic spectral amplitude (NSA) method and the deterministic spectral amplitude (DSA) method. In the proposed method, merely one or two elementary random variables are required to describe the continuous stochastic wave force field at the level of probability density. Simultaneously, the simulation efficiency of the proposed scheme is significantly enhanced by employing the Fast Fourier Transform (FFT) algorithm. In addition, the DR simulations for continuous stochastic wave force field are conducted in accordance with the linear Morison's equation (LME) and the nonlinear Morison's equation (NLME). Finally, the stochastic wave force field acting on a single pile foundation is generated by the proposed method, followed by the refined linear dynamic analysis and reliability assessment of the employed single pile foundation combining the probability density evolution method (PDEM). The effectiveness, accuracy and engineering practicability of the DR methods are sufficiently illustrated by comparison with the MCS methods thereafter. The analysis results also show that the DR methods are of significance robustness in reliability assessment of offshore engineering structures.

Damping formulations for finite difference linear dynamic analyses: Performance and practical recommendations

An in-depth study is presented on some numerical formulations used to reproduce damping of motion in solid continua. The focus is addressed in particular to those formulations that in the finite difference geotechnical code FLAC can be exploited to perform linear analyses. The numerical investigations are performed through a simple 1D model of a homogeneous soil deposit interested by a shear wave motion coming from the bedrock, and a gravity dam model subjected to seismic excitations in presence of dam-water-foundation interaction. The Rayleigh damping method is tested in particular to find an appropriate choice of the control frequency in order to minimize the problems of high-frequency overdamping. The analyses also investigate two other formulations (the local damping and its variant, the combined damping) that present the major advantages in providing a frequency independent action and in needing not significant computational resources. Limits and principal drawbacks of their possible use are highlighted.

Modeling the Mullins effect of rubbers used in constrained‐layer damping applications

AbstractThe benefits of incorporating rubber interlayers in lightweight laminates, such as fiber‐metal laminates, in order to compensate for their usually undesirable dynamic behavior have been studied in previous works [1,2]. In such constrained‐layer damping laminates, the rubber layers undergo large deformations due to their comparably low stiffness. This motivates the consideration of large strain phenomena commonly found in rubbers even when global laminate deformations are small such as in linear dynamic analysis. This work specifically addresses the cyclic softening of filled rubbers commonly known as the Mullins effect. As this effect significantly influences the elastic properties of the material, a change in the dynamic behavior of the laminate is to be expected. A constitutive model based on the work of Dorfmann and Ogden [3] for the prediction of the cyclic softening as well as residual strains upon unloading is presented in this study. Special consideration is given to the implementation of the model for use in a commercial implicit finite element solver by building on the work of Connolly et al. [4]. The model is validated against experimental data and compared to a current state‐of‐the‐art model with regard to its predictive quality and computational efficiency. Furthermore, the experimental identification of material parameters for said model is addressed.

Dynamic response of cracked concrete rehabilitated with composites

Disaster mitigation is one of the ongoing efforts in most of the countries to reduce the impact on people and property. The focus of the present study is to provide design inputs for rehabilitating beam structures using locally available composite materials based on linear and nonlinear dynamic analysis. This study models the tensile zone of a beam structure using finite elements with pre-assigned crack widths and crack depth. In linear modeling, the stiffness is assumed to vary linearly and in nonlinear modeling, bilinear variation of the stiffness is considered for analysis. The linear and non-linear response of cracked beam obtained from the finite element method is given as input for dynamic analysis. The frequency, time-period shift and amplitude are studied for uncracked beam, beams with damage for different types of cracks width and depth and design recommendation for rehabilitation of damaged beam with different types of composites are suggested.

Role of model identification and analysis method in the seismic assessment of historical masonry towers

The seismic assessment of historical monuments typically involves many issues, the most crucial of which are: retrieving geometrical and mechanical data; implementing a suitable numerical model; choosing the more appropriate type of analysis and properly interpreting the results. The more well-managed these issues are the better the reliability of the seismic assessment. The Civic Tower of L'Aquila (Italy) is considered in this paper as a typical case in which lack of data and discrepancy of sources make the seismic assessment hard to be suitably performed. The key role of the identification of the numerical model was firstly evidenced. Different numerical models were implemented to identify the best-fitting geometrical and mechanical properties of the structure. The considered case-study also led to the discussion of some issues concerning the identification of the numerical model of historical towers. Code-compliant linear and non-linear dynamic analyses were then carried out to compare the seismic performance of the tower assessed through the different methods based on regulations. A concrete damage plasticity model for masonry and a set of spectrum-consistent earthquakes were adopted. The stress maps, the horizontal displacement peaks (useful to avoid the pounding phenomenon with the adjacent Margherita palace), and the evolution of damage were investigated. The study highlighted that the widely adopted response-spectrum modal analysis (RSMA) may underestimate -even remarkably-the displacement demand compared to the more rigorous time-history linear analysis (THLA), this being an inconsistency of the code-compliant linear analyses. On the other hand, the results of the non-linear time-history analysis (NLTHA) confirmed the displacement demand predicted by the THLA, while the damage evolution under tensile stress was found in agreement with the crack pattern detected on the structure. The influence of the vertical component of the earthquake was also investigated, founding that the vertical component of the ground motion does not significantly affect the results.