Dynamic Response Of Tall Buildings Research Articles

EFFECTIVE POSITION OF SHEAR WALL FOR HIGHER RISE FOR TIME HISTORY ANALYSIS

The abstract of the study that is titled "Effective Position of Shear Wall for Higher Rise for Time History Analysis" focuses on the investigation of the best placement of shear walls in tall buildings in order to improve the seismic performance of these buildings via the use of time history analysis. By doing this research, the researchers hope to find a solution to the essential problem of establishing the most effective location of shear walls in high-rise structures in order to reduce the effects of seismic forces. Evaluating the dynamic response of tall buildings under earthquake loading circumstances is the purpose of this work. This evaluation is accomplished through the utilisation of sophisticated numerical simulations and time history analytic methodologies. In order to conduct a full analysis of the structural behaviour, the investigation takes into account a number of parameters, including the height of the building, the configuration of the shear wall, and the seismic intensity. Additionally, the study analyses the influence of varied shear wall placements on key performance measures including base shear, story drift, and acceleration responses. The purpose of this research is to determine the ideal position and configuration of shear walls for higher buildings by means of systematic analysis and comparison of the results. This will help to reduce the structural vulnerability of the building and increase its seismic resilience. Those structural engineers and designers who are involved in the seismic design of high-rise structures will find the findings of this study to have significant implications. These findings provide valuable insights into effective strategies for improving the earthquake resistance of tall buildings through optimized shear wall placement. Keywords: Shear walls, High-rise buildings, Seismic analysis, Time history analysis, Structural optimization, Finite element analysis, Seismic performance, Building dynamics, Structural stability, Optimal placement.

Methodology to minimize the dynamic response of tall buildings under wind load controlled through semi-active magneto-rheological dampers

This paper proposes a methodology to evaluate and optimize the dynamic response of tall buildings under wind loading, controlled through semi-active Magneto-Rheological dampers (MR dampers). For this, a tall building, modeled as a 2D frame, is taken as case study and three structural control configurations are proposed. The original structural configuration of the building is the first configuration analyzed, called Uncontrolled Original (C1). In the second configuration, called Uncontrolled Optimized (C2), the fundamental frequency of the building is optimized via PSO algorithm as a function of its mass. Then, in the third configuration, Controlled Optimized (C3), a set of MR dampers with behavior formulated via the modified Bouc-Wen rheological model and controlled through the Linear Quadratic Regulator associated with the Clipped Optimal control strategy (LQR-CO) is applied to the structure. Finally, the dynamic response of the three scenarios under wind action is analyzed and compared to performance criteria established in the literature. The results demonstrate that the C3 configuration is the only one able of satisfying all the established performance criteria, proving that the proposed methodology y that combines structural optimization with MR dampers is a powerful tool for vibration control.

Formulation of justifiable wind loading distributions up tall buildings derived from HFFB measurements

For the general case of non-linear and combined sway and twist mode shapes, analysis of HFFB measurements gives rise to serious challenges and various techniques have been developed using significant assumptions. This is because it is not possible to directly obtain the distribution of varying fluctuating wind loads throughout the height of tall buildings. This paper proposes a straightforward HFFB-based wind load/twist distribution approach in the time domain to predict the wind-induced dynamic response of tall buildings. Using this framework, it is possible to overcome the deficiencies of mode shape correction factor approach, and the complexity and impracticality of alternative approaches for tall buildings. Two 1:300 scale rigid models of benchmark tall buildings, IAWE Buildings A and B, have been selected to perform a detailed wind tunnel investigation as subjects to evaluate this proposed HFFB approach study. Building A has complex 3D mode shapes combining sway and twist, whereas the simpler Building B has uncoupled linear mode shapes in sway and twist. The high frequency pressure integration (HFPI) wind tunnel technique was utilised to measure surface pressure information in separate tests to obtain the reference wind loading for validation of the HFFB predictions. Furthermore, a commonly used HFFB mode shape correction factor approach was used to estimate the dynamic wind responses which were compared to those from the proposed approach. From the comparison between the aerodynamic and dynamic wind results from proposed HFFB approach and reference HFPI results, it is found that the proposed HFFB approach can predict the vertical distributions of the wind forces and torque (wind loads) with acceptable accuracy for carrying out the conceptual stage of tall building design.

Generalized Damped Outrigger Systems for Suppressing Multimode Vibrations of Tall Buildings

Damped outrigger is a viable means for reducing dynamic responses of tall buildings. This study focuses on generalized damped outrigger (GDO) systems. A GDO is composed of a damper for energy dissipation, a negative stiffness device and an inerter for damping enhancement. The GDO system incorporates GDOs at different floors of the tall building optimized to varied structural modes. Frequency equation of a tall building simplified as a cantilever beam with multiple GDOs is first derived by complex modal analysis. A finite different model of such a system is used for verification. Parametric analyses are then performed to compare damping effects of different GDO systems. It is found that a negative stiffness damped outrigger (NSDO) or inerter damped outrigger (IDO) needs to be optimized for maximizing damping of a specific mode. GDOs, respectively, tuned to different modes can largely improve the multimode damping effects. The optimal parameters of the GDOs are slightly different from those in the case when they are installed separately. With both negative stiffness and nonzero inertance, a GDO still needs to be tuned to a specific mode because multimode damping is sensitive to the damper coefficient. The combination of an NSDO optimized to the first mode and an IDO tuned to a higher mode seems the best solution. The IDO additionally improves the first mode damping provided by the NSDO and the two-mode damping is not sensitive to the damper coefficient of the NSDO. The findings are confirmed through seismic response analyses of a tall building with different GDO systems.

Shear wall analysis and optimised design for high rise buildings using ETABS

Increased population density in India necessitates the development of urban areas in particular. Structural engineers in seismic zones around the planet also put pressure on multistory structures to be built with inconsistencies in stiffness, because they realize that these structures will be subject to seismic loading. In comparison to prior high-rise buildings, today's high-rise skyscrapers are more appealing and thin, which contributes to the chance of more sway. The dynamic response of tall buildings will be monitored by developing basic methodologies for tall buildings. With more appropriate construction types, such as shear walls and tube structures, as well as improved material qualities. The integrated structural operation of floor and roof structures with walls is overall project standard of current wall construction frameworks for behavior walls. The floor structure distributes vertical and lateral stresses to the walls, which are then transferred to the foundation, which acts as a diaphragm. Shear walls that are comparable to lateral charge method resist lateral forces from wind and earthquakes. Shear resistance and resistance to overturning allow these shear walls to transmit lateral stresses to the base. The current study covers a 45-story building with a platform up to the fourth floor level.

Study of the dynamic response of a CAARC building by the synthetic wind method and comparison with different approaches

Purpose This paper analyzes the effect that is generated in the dynamic response of a Commonwealth Advisory Aeronautical Council building for different types of power spectra. This article also compares synthetic wind method (SWM) results with wind tunnel tests and other numerical approaches.Design/methodology/approach One of the main methodologies developed in Brazil, the SWM, is employed to determine the dynamic wind loads. The Davenport, Lumley and Panowski, Harris, von Karman and Kaimal model are used in SWM to generate the resonant harmonics. Lateral pressures are calculated by the wind speed deflection profile for 30, 35, 40 and 45 m/s. The structure is processed in Autodesk Robot Structural Analysis with numerical analysis in FEM by the Hilber–Hughes–Taylor method. To corroborate the synthetic wind with experimental results, displacement curves are developed for wind tunnel experimental results, Davenport method, Eurocode and NBR 6123, together with the SWM.Findings Results show that for 30 m/s, the lowest convergence of the power spectra models was presented and that the greatest difference found was below 10%. In addition, it was shown that Eurocode 1-4 can lead to oversizing, while NBR 6123 can lead to undersizing, compared with the experimental results. Finally, results by the Davenport method, wind tunnel test and synthetic wind showed good accuracy.Originality/value By carrying out this comparative analysis, this work presents an important contribution in the field of calculating the dynamic response of tall buildings. Studies with these comparisons to corroborate the SWM had not yet been carried out.

Mitigation Strategies of Cyclonic and Heavy Winds on Structures: A Review

India is one of the most vulnerable areas to tropical Cyclones, which experiences an average of 4-5 tropical cyclones every year. As per the definition of the World Meteorological Organisation (WMO, 1976), the wind speed which exceeds ‘Gale Force’ (minimum of 34 knots or 63 kmph) is considered a Cyclone. Cyclones are usually associated with high-speed winds followed by heavy rains, which leads to untold misery to the populace and devastation to properties, especially buildings. Therefore, it is necessary to have adequate knowledge of cyclone prediction systems and Cyclone resistant structures. This review Journal discusses cyclone-warning systems and various techniques adopted for Cyclone resistant structures by studying wind behaviour for different shaped structures. The findings conclude that shape modification, corner modification (especially chamfer and round shape) have shown reasonable results for improving the longevity of structures subjected to high wind speeds. Further, dynamic response of tall buildings can be minimised by increasing the structural stiffness, shear walls in appropriate location and use of viscous dampers, tuned mass dampers (TMD) etc.

Dynamic Response of Tall Building with Base Isolation Subjected to Earthquake Forces

In the fast-paced contemporary world, new inventions with rapid construction techniques came across usually built to resist the lateral forces. Among them, the demand for tall buildings has put a revolutionary impact on society. In this study, base isolation as an earthquake resisting design technique was utilized which substantially dissociate a superstructure from its substructure and increase flexibility resisting on the ground vibration areas by providing the different types of base isolators. Lead rubber bearing (LRB) isolator is a passive structural vibration control technique. In this research study, seismic behaviour of tube in tube system steel tall building in square, circular, hexagonal, and octagonal plan configurations with varying frame sections with and without LRB base isolation was analyzed for the comparative analysis on the basis of base shear, overturning moment, time period, storey displacement, storey drift and storey acceleration according to IS 1893 (part 1):2016 and UBC 1997 Earthquake code in E-TABS software by non-linear time history analysis. From the results, Octagonal shape was found to be the best option for tall buildings whereas the hexagonal shaped building showed poor performance during an earthquake.

Use of fluid viscous dampers in structural control: a case study

This study focuses on the assessment of the buildings dynamic response under wind loads. It is known that any structure inherently dissipates and absorbs energy due to external loads thanks to the combination of its deformability, strength and flexibility. An improvement of this capacity could be achieved using fluid viscous dampers, concentrating mainly on their nonlinear behaviour; a case study will illustrate the major impact of these devices on a RC tall building, subjected to wind turbulence. Wind have a great impact on the dynamic response of tall buildings, with its dynamic and random nature, it plays an important role in the design of civil structures. In this paper, the simulation of wind time histories is discussed, in order to fully cover all wind components to end up with proper results.

Smart outrigger damper system for response reduction of tall buildings subjected to wind and seismic excitations

The outrigger damper system has recently been proposed to reduce the dynamic response of tall buildings subjected to lateral loads. Previous studies have shown that the outrigger damper system could effectively increase the response reduction capacity of tall buildings. The outrigger damper system was used not only for a response reduction of tall buildings, but also for adjusting the differential column shortening. When an outrigger damper system is designed optimally for wind or earthquake loads, it shows good control performance against each target excitation. On the other hand, the outrigger damper system designed for the wind load cannot effectively control the seismic responses and vice versa. This study examined the control performance of a smart outrigger damper system for reducing both the wind and seismic responses. The smart outrigger damper system was comprised of magnetorheological dampers. A fuzzy logic control algorithm, which was optimized by a multi-objective genetic algorithm, was used to control the smart outrigger damper system. Numerical analysis showed that the smart outrigger damper system could provide superior control performance for the reduction of both wind and earthquake responses compared to the general outrigger system and passive outrigger damper system.

Computer-based model for the transient dynamics of a tall building during digitally simulated Andrews AFB thunderstorm

Thunderstorm downbursts are near ground-level meteorological hazards, exhibiting transient, non-synoptic, short-duration and high intensity wind velocities. Winds can induce nonstationary loads and large-amplitude dynamic response in a slender vertical structure. The thunderstorm-induced response against non-synoptic wind loads is extremely complex and cannot be investigated by conventional wind analysis approaches. This study examines the thunderstorm-induced dynamic response of tall buildings. The wind load is based on the observation of the Andrews Air Force Base (AFB) thunderstorm. The main objectives are to: (i) reconstruct the Andrews thunderstorm wind speed record and replicate structure, lifecycle and the fundamental wind parameters, (ii) digitally synthesize the non-turbulent and turbulent velocities to derive aerodynamic loads on a reference tall building, (iii) formulate the thunderstorm-induced dynamics of the tall building subjected to the Andrews thunderstorm-induced downburst loads, and (iv) investigate the response of a tall building by considering two different plausible scenarios. Some unanswered scientific questions are investigated: uncertainty in vertical wind velocity profiles, abrupt change of wind direction angles and influence of crosswind velocities. Three amplitude modulation functions are employed to simulate the transient turbulent field observed during the Andrews thunderstorm. Numerical simulations analyze the dynamic response of the 183-m CAARC tall building.

Dynamic Response Evaluation of Damped-Outrigger Systems with Various Heights

Outriggers are a proven and effective system used to reduce the dynamic response of tall buildings. By inserting dampers into the outriggers, providing supplementary energy dissipation, further improvements in the dynamic response can be achieved. The aim of this study is to develop analytical methods for the dynamic response evaluation of a single-damped-outrigger system and determine the optimal outrigger locations and damper sizes to minimize response. Changes in the mode shape, damping, natural period and seismic response were studied parametrically using complex eigenvalue analysis of a continuous cantilever model, and the accuracy verified by comparison with a member-by-member model. A simplified single-degree-of-freedom model was then constructed and studied using an assumed lateral displacement curve and the principle of virtual work. Finally, a practical method for determining optimal outrigger location and damper size based on this simplified model was proposed.

Dynamic Response of Tall Buildings on Sedimentary Basin to Long-Period Seismic Ground Motion

Characteristics of long-period seismic ground motion and response of tall buildings are investigated in this paper to promote earthquake proof countermeasures considering the damage caused by the 2011 Tohoku earthquake. 3D finite difference method and the reciprocal theorem are used to examine the effect of sedimentary basin structures on seismic wave amplification. Natural period and damping of tall buildings are evaluated by ambient vibration tests and earthquake response observation during construction or demolition of the buildings. The effects of dynamic soil-structure interaction on response amplification of tall buildings are confirmed applying wave propagation theory to a continuum building model. Finally, a newly built base-isolated building with an isolated rooftop laboratory is introduced for full-scale long-period shaking experiment by installing actuators and jacks. Experience of long-period shaking in the building is also available with virtual reality view of indoor damage, which is effective for promotion of seismic countermeasures such as fixing furniture and safe evacuation.

아웃리거 댐퍼시스템의 감쇠와 강성 변화에 따른 지진응답제어 성능평가

In recent years, an outrigger damper system has been proposed to reduce dynamic responses of tall buildings. However, a study on outrigger damper system is still in its early stages. In this study, time history analysis was performed to investigate the dynamic response control performance of outrigger damper. To do this, a actual scale 3-dimensional tall building model with outrigger damper system has been developed. El Centro earthquake was applied as an earthquake excitation. The control performance of the outrigger damper system was evaluated by varying stiffness and damping values. Analysis results, on the top floor displacement response to the earthquake load, was greatly effected by damping value. And acceleration response greatly was effected by stiffness value of damper system. Therefore, it is necessary to select that proper stiffness and damping values of the outrigger damper system.

Effect of outrigger-belt truss location on the dynamic response of high-rise building subjected to blast loading

Purpose– Nowadays, with the expansion of terrorist operations around the world and also the dangers of accidental explosions, the need to design structures resistant to this phenomenon for the protection and safety of its citizens is inevitable. Tall buildings are one of the most important issues because of which those behavior should be investigated against the blast loading.Design/methodology/approach– In this paper, the authors used a simple method for investigating the dynamic response of tall buildings with the combined system of framed tube, shear core and outrigger-belt truss located at different heights of the building’s that were subjected to blast loading. This proposed model is based on the development of a continuum model and the ruling equations that have been obtained using the energy principle predict the whole structure idealized as a shear and flexural cantilever beam with rotational springs at the belt truss location.Findings– The mathematical procedure shows a good understanding of the structural behavior and is suitable for a quick evaluation during the preliminary design stage, which requires less time. Moreover, it was concluded that the present blast load idealization can be used to reasonably assess the response of tall buildings subjected to blast load.Originality/value– The comparative analysis in this paper could give other engineers a simple analysis method for the preliminary analysis and design of tall building analysis. Numerical example is given to illustrate the ease of application and the accuracy of the suggested model.

Una metodología de cálculo para la determinación de la respuesta dinámica longitudinal de estructuras altas bajo la acción del viento

The optimization of computing methods along with the advance of construction technology of civil structures, allow nowadays to design and build lighter and low stiffness and damping structures, turning them into elements of high sensitivity against wind-induced dynamic effects. The purpose of this work is to describe and to apply a simple calculation methodology that enables the determination of the longitudinal dynamic response of tall buildings in time domain. The wind velocity field is reproduced by velocity series that incorporate the coherence function which then are transformed into fluctuating nodal forces using the quasi-static loading model. Furthermore, to include the effect of imperfect averaging associated with the discretized nodes, the aerodynamic admittance function is added.Through the proposed methodology two structures widely studied by other authors are analyzed: a steel tower and the CAARC Standard Tall Building. The results thus obtained show agreement with those reported in the literature.

The effect of soil–foundation–structure interaction on the wind-induced response of tall buildings

The aim of this work is to provide a contribution towards the qualitative and quantitative assessment of soil–foundation–structure interaction effects on the dynamic response of tall buildings founded on relatively rigid rafts, and subjected to wind loading. The mechanical response of the soil–foundation system is modeled using two different approaches: in the first, the (visco)elastic system response is defined in terms of impedance coefficients; in the second, an inelastic, 6 DOF macroelement recently proposed for shallow foundations on coarse-grained soils is adopted. The macroelement approach allows to account for the non-linear and irreversible behavior of the soil–foundation system, and to consider the experimentally observed coupling between the different degrees of freedom in the inelastic regime. The results of a series of numerical simulations highlight the importance of considering SFSI effects in the analysis, and allow to identify the effects of the different constitutive assumptions made for the soil–foundation system. In particular, it is found that the permanent displacements and rotations accumulated at the foundation level in the inelastic simulations can give rise to significant permanent displacements at the building top. Moreover, significant differences are observed on the predicted forces and moments distribution at the building base for the two SFSI approaches considered.

High-frequency force balance technique for tall buildings: a critical review and some new insights

The high frequency force balance (HFFB) technique provides convenient measurements of integrated forces on rigid building models in terms of base bending moments and torque and/or base shear forces. These base moments or forces are then used to approximately estimate the generalized forces of building fundamental modes with mode shape corrections. This paper presents an analysis framework for coupled dynamic response of tall buildings with HFFB technique. The empirical mode shape corrections for generalized forces with coupled mode shapes are validated using measurements of synchronous pressures on a square building surface from a wind tunnel. An alternative approach for estimating the mean and background response components directly using HFFB measurements without mode shape corrections is introduced with a discussion on higher mode contributions. The uncertainty in the mode shape corrections and its influence on predicted responses of buildings with both uncoupled and coupled modal shapes are examined. Furthermore, this paper presents a comparison of aerodynamic base moment spectra with available data sets for various tall building configurations. Finally, e-technology aspects in conjunction with HFFB technique such as web-based on-line analysis framework for buildings with uncoupled mode shapes used in NALD (NatHaz Aerodynamic Loads Database) is discussed, which facilitates the use of HFFB data for preliminary design stages of tall buildings subject to wind loads.

Dynamic response of tall buildings to wind loads by reduced order equivalent shear-beam models

Two equivalent beam models are proposed in order to estimate the dynamic response of tall buildings affected by wind loads. The first model is based on the Timoshenko beam, which assumes bending and shear stiffness to be in series. The second model considers bending and shear stiffness to be in parallel. The parameters of the two equivalent beams are calibrated using the data of a complete structural system and imposing both the value of suitable displacements (static approach) and the value of the first natural frequencies (dynamic approach). Numerical analyses are performed using wind tunnel loads and FEM models. The accuracy of the dynamic response of the two equivalent beam models is assessed by comparison to a complete FEM model describing the structural system of a case study tall building. Furthermore, the ability of the equivalent shear-beam models to describe the random features of dynamic response is assessed using the first four statistical moments of the dynamic response.

Natural frequency coalescing and amplitude dependent damping in the wind-excited response of tall buildings

During the analysis of data from the full scale monitoring of the dynamic response of tall buildings, it has been observed that under certain conditions the fundamental natural frequencies of the structure can coalesce for moderate wind excitation. Together with this phenomenon, the dependency of damping on the amplitude of the response was also noted. Recently, a detailed description of this amplitude dependency has been made possible by a new generation of concept-based damping models, developed following the boom in the collection of full scale data from the monitoring of tall buildings. In light of this new knowledge, this paper investigates the possibility that the amplitude dependency of damping could be at the root of the frequency coalescing phenomenon. To this end, a concept-based probabilistic damping model is coupled with a reduced order two-degrees-of-freedom system that reproduces the two coalescing modes of a building. For this system, the analytical time-invariant conditions under which the frequency coalescence can occur are firstly identified. Then, the inherent variability of the amplitude dependent damping, described by the concept-based model, is considered as a means for instantaneously satisfying the aforementioned conditions. By exciting the reduced system through experimentally determined wind loads, the direct observation of the phenomenon—through time–frequency wavelet analysis—is achieved.