Top Floor Displacement Research Articles

Parametric Analysis of Moment-Resisting Timber Frames Combined with Cross Laminated Timber Walls and Prediction Models Using Nonlinear Regression and Artificial Neural Networks

The light weight and moderate stiffness of multistorey timber buildings make them susceptible to increased lateral displacements and accelerations under service-level wind loading. Therefore, the fulfilment of serviceability requirements is a major challenge. In this study, linear elastic finite element analysis was used to perform a parametric study of moment-resisting timber frames combined with cross laminated timber walls. In the parametric study, various mechanical and geometrical parameters were varied within practical ranges. The results of the parametric study were used to derive simplified analytical expressions and to train artificial neural networks which can be used to estimate fundamental frequency, mode shape, top floor displacement, maximum inter-storey drift, and wind-induced acceleration. The analytical expressions and the artificial neural networks can be used for the preliminary assessment of serviceability performance of moment-resisting timber frames with and without cross laminated timber walls, under service-level wind loading.

On the optimization of Tuned Mass Damper Inerter (TMDI) systems for buildings subjected to real ground motions using slime mould algorithm

This paper proposes a novel optimization framework for the optimal design of Tuned Mass Damper Inerter (TMDI) devices to mitigate the excess vibration of multi degree of freedom (MDOF) buildings under earthquake ground motions. Minimizing the H∞- norm of the top floor displacement transfer functions is considered as the objective function for the optimization process. A Tuned Mass Damper Inerter (TMDI) is employed in which a TMD is placed at the top floor of a building connected via inerter. The top floor displacement of the building under eighteen (18) real earthquake ground motions classified in terms of low, intermediate and high frequency contents, is minimized using three optimization algorithms, particle swarm optimization (PSO), slime mould algorithm (SMA) and Harris Hawks optimization (HHO). The effectiveness of different algorithms is assessed using the RMS (root mean square) based values and the reduction ratio. The optimised parameters of the TMDI (mass ratio, frequency ratio, damping ratio and inertance ratio) obtained using the slime mould algorithm (SMA) are found to be better than the other optimization algorithms for the numerical example carried out in this paper. The results show that, the optimised TMDI has significant effect on the suppression of top floor displacement, acceleration with a lightweight TMD. The optimal parameters of TMDI shows a remarkable potential in suppressing maximum displacement reduction ratios of 0.83, 0.85 and 0.86 in response to low, intermediate and high frequency content earthquake ground motion, respectively. Based on the numerical results, the passive TMDI unveils a promising vibration calming system for damped elastic structure.

Site-Specific Aseismic Design of Multi-Storeyed Buildings Using Optimum Tuned Mass Damper Inerter

ABSTRACT The effectiveness of the tuned mass damper inerter (TMDI) in reducing the vibration of building structures under site-specific earthquake excitation is investigated. The site is Guwahati, Assam, which lies in the most severe seismic intensity zone in India. In this paper, the optimization of the TMDI design parameters is carried out for the site-specific input derived for the building site by a modulated Clough-Penzien (C-P) spectrum fitted to the power spectral density function obtained from a strong motion model of the site. All possible topologies of the TMDI, with one terminal of the inerter being connected to the damper mass attached to the top storey of the example buildings, and the other terminal being connected to any other floor, are investigated. The structure-TMDI system is analyzed both in the frequency-domain and in the time-domain. A numerical study is conducted with two example building structures. Optimization of design parameters of the TMDI is carried out using the technique of simulated annealing in the frequency-domain using the site-specific modulated Clough-Penzien spectrum as input. The performance of the optimal TMDI cases is evaluated by subjecting the example structures to 10 site-specific synthetically generated accelerograms. Results indicate that the TMDI is superior to the TMD for all topologies of the TMDI in case of the 3-storieed structure; and for topologies of the TMDI in which the inerter spans more than 4 floors for the 8-storied structure, with improved reductions in top-floor displacement, acceleration, and stroke length.

Estimating the robust optimal parameters of tuned mass damper

The tuned mass damper (TMD) is one of the oldest and most extensively used passive vibration control systems in dynamically excited buildings. However, the uncertainties or randomness in the loading and the primary structure parameters (i.e., stiffness and damping coefficient) significantly affected the TMD performance. In this framework, Robust Design Optimization (RDO) technique is advantageous, aiming to simultaneously minimize the performance function’s mean and variance. Simulation-based RDO techniques are particularly effective at solving difficult nonconvex and multimodal issues. Therefore, in the present study, a stochastic simulation-based approach is proposed for the RDO of TMD. The performance function’s mean and variance are considered robustness measures. The TMD’s frequency and damping ratios are considered design parameters. TMD attached to a Multiple-Degree-of-Freedom (MDOF) structural system is analyzed to demonstrate the efficacy of the proposed approach. The top floor displacement variance ratio of the protected structural system to that of the unprotected structural system is adopted as the performance function. The simulation results show that the proposed strategy successfully identifies the optimal design for all levels of uncertainty. The necessity of considering the uncertainties is well highlighted. In conclusion, the proposed approach is found to be effective and offers the designer more information for an optimal design decision.

Influence of masonry infills on blast response of earthquake-resistant reinforced concrete buildings

The present study investigates the influence of masonry infill strength on the blast performance of earthquake-resistant reinforced concrete (RC) buildings under surface burst. These buildings, having three-dimensional RC moment resisting frames, are designed to withstand different levels of seismic demand. The masonry infills are modelled as an equivalent diagonal strut using a macro-modelling approach to account for its in-plane strength and stiffness. The blast-induced loads are directly applied as nodal loads on the exposed beam-column joints, and nonlinear time history analyses are then performed to obtain the various response quantities such as top floor displacement, interstory drift ratio, and base shear. The comparative matrices of various response quantities are developed to examine the effect of infill’s nonlinearity. Further, the influence of the infill strength and seismic design level of the considered buildings is probabilistically assessed by developing the blast fragility curves using an uncoupled approach. It is observed that the consideration of infill’s nonlinearity influences the blast response up to a certain scaled distance only. Moreover, increasing the infill strength does not necessarily enhance the blast performance; however, designing the building to higher seismic demand results in improved blast performance. In addition, proper insight into seismic design level and infill strength of any RC building is required prior to plan and design them with suitable blast-mitigation measures.

Parametric study on response of multi-storied building equipped with viscous and visco-elastic dampers subjected to ground motions.

Viscous and viscoelastic dampers are passive energy dissipation devices that are used in multi storied buildings to reduce the effect of lateral vibrations arising from earthquakes and wind. Passive devices are those that require no energy to function. The performance of such devices can be affected by many factors like seismic zone, building height, soil type and placement of dampers. In this paper, the effect of using viscous and visco-elastic dampers on response of multi-story building was investigated. For this purpose, multi-story building was modelled in Finite element software. Various parameters like height of building, seismic zone, soil type and placement of dampers were varied in the FEM model. To investigate the seismic response, non-linear time history analysis was performed by subjecting the building to ground motion (Imperial Valley 1940). Seismic responses of the models were studied and compared in terms of results like top floor (roof) displacement, storey drift and ground floor level (base) shear. It was found that viscous dampers are more effective in dissipating energy. Optimum position of dampers was also found out. All the parametric results were obtained and plotted in graphs.

Seismic Response Of Multi-storey Building Using Artificial Neural Network

The different parameters like base shear, drift, and top storey displacement of G+7 building is evaluated by using time history analysis and response spectrum analysis for the purpose of comparative study of both the analyses using MATLAB and an artificial neural network (ANN). The main objective of present work is to analyse earthquake of different locations like Bhuj, Kobe, Victoria and Elecentro, for time history analysis building is not connected with actuator and it is analysed during seismic motion of building using a MATLAB software. Base shear, drift and top storey displacement is evaluated during this analysis. For response spectrum analysis, first building relates to actuator at top floor. And during seismic motion of building different parameters like base shear, drift and top floor displacement are evaluated using MATLAB software and for evaluation of control force of a design actuator artificial neural network (ANN) is used. From time history analysis, response spectrum analysis test results and graphs for G+7 building it is clear that, when actuator is not connected with building it does not dissipate the energy of seismic motion and base shear of building , drift , and top floor displacement is very high, and in second case when building is connected with actuator at optimal place it gives considerable response during seismic motion of building and base shear of building, drift, and top floor displacement are can considerably reduce using control actuator system.

Velocity Tracking Control Algorithm for Semiactive Control of Building Frames

A new control algorithm called velocity tracking control (VTC) is presented for the semi-active control of partially observed building frames using magneto-rheological (MR) dampers. The novelty of the control algorithm relies on the use of special features of the semi active control using MR dampers in which the time history of voltage to be applied to the MR damper can be generated with the help of feedback information from the observed states only; it does not require the estimation of the full state from the measured ones which introduces some errors in the estimated control force generated in the MR damper. The algorithm is developed based on a physical reasoning, which is validated by the Lyapunov stability condition of the first order filter used in the modified Bouc-wen model that models the MR damper. The efficiency of the control algorithm is compared with the passive on control for a number of earthquakes. The response quantities of interest, for which percentage reductions in responses are compared, include the peak top floor displacement, peak inter-story drift and maximum base shear. The results of the study show that the proposed control algorithm provides the maximum percentage reduction in peak inter-story drift in comparison to passive on control. Further, the efficiency of the proposed control algorithm, defined by the percentage reduction of responses per unit control force, is found to be more as compared to the passive on control.

Seismic Assessment of Multistorey building of plan irregularity with varying A/L ratio (Re-entrants corners)

Buildings with re-entrant corners are used when maximum utilization is done over minimum available space. These re-entrant corners come under the plan irregularities of the structures. Plan irregularity (or) Vertical irregularity makes vulnerable under seismic loading. Structural irregularities are an important factor in that structure’s seismic performance structure. This study aims to gain the seismic behaviour of the building with an L-shape floor plan by checking the irregularity of re-entrant corners by seismic response demands that is been measured with varying A/L ratios. The response includes top floor displacement, interstory drift, Story Stiffness, and base shear. The study consists of 5 models with varying A/L ratios with 3 sub-divided models of various seismic positions of the shear wall (i.e.) a model without a shear wall, a model with a shear wall at the centre, a model with a shear wall at the periphery. 15 models are made for a clear study of the seismic behaviour and the effective position of the shear wall with varying A/L ratios. The models are analysed with ETABS using the Equivalent static method (ESL) and Response Spectrum (RS) methods. The results prove that the model with a lesser A/L ratio satisfies the analysis even without the shear wall excluding the lift RCC wall, whereas when the A/L ratio increases the model is effective only when the shear wall is provided at the periphery. Thus, the economical and effective seismic position of the shear wall is found with varying A/L ratios and satisfies the seismic demand for the structure. As the building with re-entrant corners are more vulnerable the building plan must be of regular configuration to possess significant seismic resistance.

Optimization of TMD Parameters in Frequency Domain Including SSI Effect by Means of Recent Metaheuristic Algorithms

This study presents the application of three recent metaheuristic optimization algorithms to design the tuned mass damper (TMD) for a high-rise building structure, taking into account the effect of soil–structure interaction (SSI) in the frequency domain. The algorithms used in this study were grey wolf optimizer (GWO), moth–flame optimization (MFO), and whale optimization algorithm (WOA), and the obtained results were compared with the well-known particle swarm optimization (PSO) and genetic algorithm (GA). The TMD optimization problem was formulated with two objective functions: the H2 and the H∞ norms of the top floor displacement. The frequency, the mass, and the damping ratio of the TMD were optimized within defined bounds for a 40-story benchmark structure. Unlike in previous research, the optimization in this study was performed for different mass ratios. First, the efficiency of the obtained optimum parameters was plotted in the frequency domain and then tested in the time domain by presenting the top floor displacement of the same benchmark structure. The time domain analysis was carried out using the El Centro and Petrolia earthquakes as external disturbances. It was found that the optimal TMD parameters are affected by the soil type. The GWO algorithm reached the optimal solutions faster and more efficiently than the other algorithms. GA limitations were pointed out.

Research on damping performance and parameter influence of new frame-MRD-core tube composite structural system

The position of the plastic hinge is uncertain due to the design and construction of the frame-core tube structural system, causing problems such as reduced collapse resistance and difficulty in repairing after an earthquake. To address these problems, this paper proposes a new type of frame-magnetorheologicaldamper (MRD)-core tube composite damping structural system. In this system, the frame and the core tube are two independent structures connected by MRD. Based on the instantaneous optimal control algorithm, the semi-active control strategy of MRD is designed. The relative motion between structures is used to provide damping force, and the vibration control equation is established. In this paper, a 10-story reinforced concrete frame-MRD-core tube composite structural system is taken as an example, and the El Centro (NS, 1940) ground motion with the peak acceleration of 220 cm· S-2 is used as the lateral load for horizontal seismic time-history analysis. MATLAB is employed to perform numerical simulation calculations to investigate its damping effect and related influence parameters. Compared with the traditional frame-core tube structural system, the new system can reduce the top floor displacement and the maximum interstory drift by more than 50% and reduce the top floor acceleration of the frame and core tube by 65% and 40%, respectively. Furthermore, reasonably optimizing the position of the control floor can reduce the number of dampers. When the interstory control is implemented, the total control force of dampers can be reduced by 18% compared to the full-story control. This article provides a new damping idea and theoretical reference basis for the engineering design and application of the frame-core tube composite structural system.

A Study on Seismic Response of RCC Buildings on Hill Slopes Using STAAD.Pro

Abstract: The majority of India's hilly regions are prone to earthquakes. A building on a steep slope is distinct from other structures. That is to say, structures that are to be constructed on hilly terrain have a higher risk factor of falling prey to seismic activities as compared to their counterparts built on a rather plainer terrain. The numerous floors/storeys of such a structure step back towards the hill slope, and buildings may also have setbacks. As such, the column of a hill structure sits at different heights on the angle of the terrain; its analysis differs from that of buildings on level ground. The current study looked at G+3 and G+4 structures with different slope angles, such as 00 , 7.50 , 150 , 22.50 , and 300 . Both Step back and Step back & set back types of building configurations have been studied in this paper. The earthquake forces are calculated according to IS: 18932002; the structures are situated in seismic zone IV, with a damping ratio of 5%. Linear Static and Linear Dynamic methods were employed to conduct the seismic study. To investigate the influence of shifting column heights in the ground level due to sloping ground, a 3-dimensional analytical model of building plan was created and the same was studied using the structural analysis application "STAAD.Pro." To quantify the effects of diverse sloping terrain, response parameters like top storey displacement, base shear, shear in bottom storey column, and time period were thoroughly studied. It has been discovered that short columns on the elevated side of the terrain/slope experience a greater shear force as compared to columns of increased height on the lower side of the terrain. Under earthquake stresses, Step back & Setback structures showed better resilience to seismic forces as compared to Step back buildings. Step back setback buildings have substantially lower base shear and top floor displacement than setback buildings on sloping land. Keywords: Earthquake, Slope, STAAD.Pro, Step back, Step back & set back

Stochastic seismic response of building with shape memory alloy damper

The present study focuses on the estimation of response of building structure supplemented with the superelastic shape memory alloy (SMA) damper under the stochastic seismic excitation. To this end, the stochastic response has been determined using the stochastic linearization method under random earthquakes and the control efficiency of the SMA damper is compared with the yield damper. As the response output, top floor root mean square (rms) acceleration and displacement are presented here in this study. Response analysis results show the presence of optimal values of damper strength which minimizes the responses. As observed, in this optimal condition of damper strength, compared to the yield damper, the SMA damper provided 17 % and 49 % improvements in the values of top floor rms acceleration and displacement. In the end, the parametric study has been performed under the varying strength and stiffness of the damper, time period of the structure, and earthquake excitation to establish the superior control efficiency of SMA damper over yield damper.

Multi-objective optimal design of SC-BRB for structures subjected to different near-fault earthquake pulses

The purpose of this research is to propose a two-objective optimum design technique of self-centering buckling restrained brace (SC-BRB) characteristics based on a multi-objective cuckoo search (MOCS) optimization algorithm for structures subjected to pulse-like near-field seismic excitations. The optimal geometric specifications of shape memory alloy (SMA) and buckling-restrained brace (BRB), including the length of SMA bars, BRB core, area of SMA, and BRB core, are optimized with the aim of simultaneous reduction of the maximum displacement and acceleration of the floors of structures. The numerical analyses are then performed on 3-story and 6-story frames that have been modeled in OpenSees software under pulse-like near-fault earthquakes. The optimized SC-BRB using MOCS considerably reduces the seismic responses of both structures. The SC-BRB also performs better than BRB in severe earthquakes with a shorter fault distance and a larger moment magnitude. Furthermore, SC-BRB has a steady energy dissipation capacity due to more energy absorption in SMA. In terms of maximum top floor displacement and acceleration, the 3-story SC-BRB frame (SC-BRBF) results are reduced the values of 28.3% and 20.1% than the BRB frame (BRBF) for all considered near-fault earthquake pulses, respectively. Moreover, the optimized SC-BRB is considerably capable of reducing the hazards originating from residual drifts and deformations.

Optimum Double Mass Tuned Damper Inerter for Control of Structure Subjected to ground motions

Tuned mass damper inerter (TMDI) is commonly reported to be a lightweight tunable device that can significantly reduce buildings' seismic response. However, the backward action produced by the inerter and returned to the building in conventional TMDIs may either reduce the device performance or limit the inerter potential. This study proposes and investigates a novel control scheme using large physical mass ratios generated by lightweight inerters. Hence, a double mass tuned damper inerter (DMTDI) is formulated. The proposed control scheme consists of two TMDs placed at the roof of the building and connected via an inerter. Thus, the inerter backward action is transmitted to the secondary mass instead of the building. Both TMDI and DMTDI parameters are optimized using a genetic algorithm (GA). The top floor displacement transfer function's H2- norm is considered as the objective function for minimization. The optimally tuned devices are then tested under one hundred (100) near and far-field ground motions. The results obtained show a significant response improvement in peak displacement, acceleration, and base shear. The structure energy is also investigated; the lowest energy response in the studied structure is observed while using the proposed DMTDI scheme.

A tuning algorithm for a sliding mode controller of buildings with ATMD

This paper proposes an automatic tuning algorithm for a sliding mode controller (SMC) based on the Ackermann’s formula, that attenuates the structural vibrations of a seismically excited building equipped with an Active Tuned Mass Damper (ATMD) mounted on its top floor. The switching gain and sliding surface of the SMC are designed through the proposed tuning algorithm to suppress the structural vibrations by minimizing either the top floor displacement or the control force applied to the ATMD. Moreover, the tuning algorithm selects the SMC parameters to guarantee the following closed-loop characteristics: (1) the transient responses of the structure and the ATMD are sufficiently fast and damped; and (2) the control force, as well as the displacements and velocities of the building and ATMD are within acceptable limits under the frequency band of the earthquake excitation. The proposed SMC shows robustness against the unmodeled dynamics such as the friction of the damper. Experimental results on a reduced scale structure permits demonstrating the efficiency of the tuning algorithm for the SMC, which is compared with the traditional Linear Quadratic Regulator (LQR) and with the Optimal Sliding Mode Controller (OSMC).

A control scheme for AMD in the presence of time-delays and SSI effects for tall buildings

The present study addresses the issue of seismic control of active mass damper (AMD) devices in the presence of time-delay for the tall buildings taking into account soil-structure interaction (SSI) effects. Considering the simultaneous effects of the time-delay and SSI, a control scheme of linear quadratic regulator (LQR) controller with a new form of the weighting matrices is proposed. Then, a design procedure based on a particle swarm optimization (PSO) algorithm is proposed to find the optimal weighting matrices of the controller. The numerical studies are conducted on a benchmark tall building. The validity of the proposed LQR controller is demonstrated for the structure subjected to 44 well-known earthquakes. It is concluded that ignoring the SSI and time-delay effects may give an incorrect estimation of the seismic demands of the building. By increasing the soil softness, the structural responses are often increased. Furthermore, it is found that the proposed controller gives a worthy performance in mitigation of maximum top floor displacement for different soil conditions in the presence of time-delays. However, in the presence of long time-delay, a significant increment may achieve for maximum floor acceleration, especially for the soft and medium soils. However, the maximum drifts of the floors remain within the allowed ranges.

Relative Performance of Linear Quadratic Regulator and Pole Placement Technique for Active Seismic Control of Structures

This paper presents the study conducted on the comparison of the performance of the two popular active control algorithms viz. Linear Quadratic Regulator (LQR) and Pole Placement technique in terms of their capability to alleviate the response of a structure to an earthquake. To compare the performance of the two control algorithms, a ten story regular shear building frame with three active tendons located in 1st, 4th and 5th Storys and subjected to an El Centro earthquake has been considered. A comparison of the numerical results shows that the reductions of maximum top floor displacement, maximum story drift and base shear obtained using LQR control algorithm are 71.48%, 59.70% and 62.7% while the reductions obtained using Pole Placement technique are 73.77%, 73.14% and 77% respectively. The percentage reduction of the three performance parameters per unit control force obtained using the two methods have also been estimated and compared. Pole placement technique gives higher reduction while the LQR algorithm gives more reduction per unit control force.

A Study on the Effects of Vertical Mass Irregularity on Seismic Behavior of BRBFs and CBFs

Today, architectural application and economic constraints require that vertical-irregular structures be constructed in urban areas. Proposing methods to minimize damage to these structures during earthquakes is therefore crucial. Strict regulations have been enforced for the design and analysis of irregular structures given their higher vulnerability to damage compared to that of regular structures. The present study aimed to evaluate eight regular and irregular 10-story and 15-story steel structures with buckling-restrained braces frames (BRBFs) and concentric braced frames (CBFs) in terms of their responses to twelve far-field earthquakes. According to the obtained results, the mean value of maximum drift, top floor displacement and floor acceleration were higher in both regular and irregular structures with BRBFs than in those with CBFs.

Optimal placement of friction dampers in building considering nonlinearity of soil

It is well known fact that, supplemental damping is one of the best way to improve the performance of building during seismic event. Out of many supplemental damping devices, friction dampers are widely used as they are easier to install and independent of temperature like viscous dampers. Generally, these devices are designed assuming fixed base conditions. Even for achieving optimal number and location of friction dampers, fixed base conditions are assumed. But, when the soil–structure interaction is considered in analysis, degradation in the capacity of structure is observed. Hence, in this paper a methodology is proposed for optimal placement of friction dampers considering nonlinear soil-foundation system. The numerical study on G + 6 storey building is done to evaluate the efficiency of proposed methodology with the use of 4, 8 and 12 friction dampers. For optimization, performance objectives based on maximum base shear, top floor displacement and energy dissipation are used. From the study, it is seen that proposed approach yields targeted performance, even with less number of friction dampers when the nonlinearity of soil is considered.