Story Drift Research Articles

Seismic response of Special Moment Resisting Frames constructed on plain and sloping ground

Earthquakes are one of the most extinctive natural unpredictable disaster. The major reason of most of the earthquakes are the movement of Tectonic plates and excitation in the earth’s crust. It is observed that many conventional buildings have constructed without considering seismic provisions given by Indian standard codes to escape the disastrous effect of earthquakes which results into the collapse and disintegration of buildings. Therefore, the concept of earthquake resistant building design came into consideration and this is the most crucial aspect when a structure is to be designed for sloping terrain or for the hilly area. This research is carried out to examine the response of structures during the ground oscillations in terms of storey drift, base shear and storey displacement. For research work, 8storey, 12 storey and 16 storey frames are considered which are constructed on plain ground and sloping ground and 20°, 30°and 45° slopes and zone V are considered. All the frames are designed and analyzed using pushover analysis in finite element based software ETABS v-19. Response reduction factor is also calculated for several frames and compared the calculated values with the values given in IS 1893:2016(part- I).

Design and Detailing Recommendations of Slotted-Hidden-Gap Connection for Square HSS Brace Members

The slotted-hidden-gap (SHG) connection eliminates the need to reinforce the slot region of hollow structural sections (HSS) braces of concentrically braced frames (CBFs). However, the existing design approach for SHG connections is rather empirical and limited by the range of the connection geometries and materials that had previously been tested. A general design approach based on the findings of a large-scale parametric study is presented in this paper, where the most critical parameters of the connection were varied. Different weld configurations were investigated to examine the effect of shear lag on the overall performance of the brace. The inelastic performance of SHG-connected braces designed using the proposed approach was validated by means of numerically simulating the resulting braces and connections and subjecting them to a reversed-cyclic loading protocol. The simulated braces were able to attain their yield tensile resistance and fracture away from the connection region while sustaining an axial deformation corresponding to an average story drift of 5.43%. The proposed design and detailing method was, as such, found to be effective in the design of square HSS SHG connection braces ranging in size and steel grade.

Seismic Behaviour of Building with Soft Storey: Review

Abstract: The high-rise building in which ground storey consists of open space is known as building with soft floor. Such floor plays an important role in seismic performance of the building. This is due to the abrupt changes in lateral stiffness and strength caused by such storey. In the present era there is increase in population, finding parking for flats in congested areas has become a significant issue. As a result, erecting multistory structures with an open first floor is now a widespread practice. These Buildings that have all upper storeys enclosed by masonry walls but no infill masonry walls in the ground story are referred to as "Soft Storey" or "Open Ground Storey Buildings." Compared to regular buildings, irregular structures the drift is observed to be effectively reduced by larger columns, while the shear force and bending moment on the first floor are increased. During a violent earthquake, the Soft Storey buildings function poorly. Understanding the behavior of is this study's primary goal to the building in a seismically active area and to assess the effects of Storey overturning moments, Storey drift, displacement, and design Base shear. For comparison, G-15 story building with five completely distinct shapes a square, an L-shaped building, a Tshaped building, a plus shape building and a C-shaped building is used. ETABS 2018 version is used to analyze the entire set of models. Dynamic Analysis has been examined in the current work to assess the deformation of all five-shape building with and without soft storey considering at different level. When the soft story is offered at a higher level, displacement is reduced. Several studies on this subject that have been done in the past are reviewed in this paper. Reviewing research papers let us know about the conclusive results, which served as the basis for the objective of our future study.

Nonlinear Time History Analysis for Seismic Effects on Reinforced Concrete Building

A typical Reinforced Concrete (RC) building frame comprising of RC columns and connecting beams that participates in resisting the earthquake forces. Due to earthquake, reversal tension generates at both faces of a beam and column; and hence damage occur in the frame for the disability of tension carrying capacity of concrete. Therefore, the structural performance of RC building for seismic load has been analyzed by nonlinear time history analysis method for this study. A residential building located in Dhaka, Bangladesh subjected to various types of gravity load and seismic load was considered to analyze using ETABS software as per the guideline of BNBC (2020). According to the guideline of ATC 40 (1996), the seismic performances like maximum displacement and story drift for RC building were evaluated both at structural and element levels by applying El Centro (1940) ground motion at the base of the structure. Formation of plastic hinges is used as the basis to evaluate the local performance and story drift is used to evaluate the global performance. At first, the considered building was designed only for gravity load, and then for both gravity and seismic load according to BNBC (2020). Further studies have been performed on that building considering double height column at a story level. It was observed that the maximum displacement and story drift exceeds the allowable limit for all the considered cases if seismic load is applied on the structure.

Towards seismic performance quantification of viscous damped steel structure: Site-specific hazard analysis and response prediction

With an emphasis on predictable performance, the paramount importance of performance-based earthquake engineering (PBEE) in quantifying earthquake risks and facilitating the better-informed design of the built environment to achieve earthquake resilience has been widely acknowledged. And the uses of damping systems, i.e., structures incorporated with supplemental damping devices, have been recognized as an effective structural development to increase the resilience of structures to earthquakes. This paper presents a uniform hazard spectrum (UHS) based site-specific ground motion selection procedure, to implement the PBEE framework to relate earthquake hazard to structural performance for structures with variable dynamic properties. This ground motion selection procedure accounts for the effect of variable structural dynamic properties on hazard characterization for structures with damping systems. A paradigm building site, on which the site-specific hazard from the probabilistic seismic hazard analysis (PSHA) is consistent with the risk-targeted hazard from the design maps of ASCE/SEI 7-10, is selected for the implementation of the procedure. Three suites of 40 ground motions representing various hazard intensities at the building site are selected for time history dynamic analysis of a prototype structure with nonlinear viscous damping system. Evaluated is the probability distribution of major engineering demand parameters (EDPs) including story drift, residual story drift, floor velocity, and floor acceleration. The results demonstrated that the major EDPs of a building structure with supplemental nonlinear viscous dampers at a paradigm site can be estimated using the lognormal probability distribution, and the proposed UHS-based site-specific ground motion selection procedure is critical to the performance assessment of structures with variable dynamic properties in the PBEE framework.

Stiffening effects-controlling sizing procedure of ADAS dampers in seismic retrofit of frame structures

Added Damping and Stiffness (ADAS) steel dissipators are among the most classical devices installed in dissipative bracing systems for the advanced seismic retrofit of frame buildings. An energy-based sizing procedure is formulated in this study for this class of dampers, where the total number of constituting plates is directly related, without iterative steps, to the supplementary damping energy required to jointly reduce stress states in structural members and storey drifts. The stiffening effects of the dissipative braces are expressly controlled, so as to compensate for the increase in storey shears induced by their incorporation in the frame skeleton. The sizing procedure is demonstratively applied to the retrofit design of a 6-storey reinforced concrete building, to explicate and discuss the use of its analytical relations and relevant limitations in practice. The evaluation of the seismic performance of the structure in retrofitted conditions allows comparing the response of the dissipative bracing system with the hypotheses formulated at the sizing stage.

Rapid seismic fragility curves assessment of eccentrically braced frames through an output-only nonmodel-based procedure and machine learning techniques

A nonmodel and output-only-based framework incorporating an Auto-Regressive model and roof absolute acceleration response are hired in this study to compute a robust wavelet-based damage-sensitive feature (rDSF) and estimate engineering demand parameters (EDPs) of buildings with eccentrically braced frames (EBFs). A large database is recruited to estimate the peak and residual story drift ratios and peak floor absolute accelerations as EDPs. The database comprises cmorfb-fc wavelet-based rDSF, number of stories, building heights, and EDPs of the 4- and 8-story EBF archetypes, resulting from 44 far-field ground motions through incremental dynamic analysis. The capability of both the closed-form equations and machine learning (ML) techniques is investigated to estimate the EDPs. The predictive equations are constructed using ordinary least squares linear regression, Symbolic and Bayesian regressions. To have a more accurate estimation of EDPs, 12 renowned ML-based regression algorithms are also implemented for training, validation, and test datasets. Sensitivity analysis using box-whisker plots on the validation dataset shows that Extreme Gradient Boosted Trees (ExGBT) ensemble has a remarkable efficiency to predict the EDPs and leads to the highest 10-fold correlation coefficient and the lowest root-mean-square error. Moreover, ExGBT has the lowest median absolute relative deviation in different damage states and consequently is selected as the best surrogate algorithm. The predicted EDPs can be further exploited to map rDSF-based fragility curves, a conditional probability at each defined damage state given the value of rDSF. The comparative results for the test data approve that the predicted fragility curves approximately match with those obtained from observed data and can be used for early decision-making in emergency operations.

COMPARATIVE STUDY OF A TALL BUILDING WITH CONVENTIONAL AND FLAT SLAB SITUATED ON SLOPING GROUND UNDER SEISMIC FORCES

The structures are generally constructed on plain surface, but due to scarcity of plain ground in hilly regions leads to construction of building on a sloping ground. One of the biggest challenges of structural engineer is to design an earthquake resistant building on sloping ground. In present study conventional slab & flat slabs with RC building situated on sloping ground without any change of natural terrain have been considered for the analysis. The modeling & analysis of RC building has been done by using structure analysis tool ETABS 2019, to study the behavior of building for earthquake force. The equivalent static analysis and response spectrum analysis apply on building results were obtained in the form of maximum displacement, story drift, story shear, base shear, time period, axial force, shear force, bending moment.

Performance-based active controller design for nonlinear structures using modified black hole optimization

This paper presents a novel approach that facilitates the design of active controllers to mitigate seismically induced damage in structural systems. The proposed method is based on stochastic Modified Black Hole optimization algorithm. Two traditional controllers, namely Proportional-Integral-Derivative (PID) and Linear–Quadratic Gaussian (LQG) controllers were designed, and their performance was demonstrated on a benchmark 20-story steel-framed building. Evaluation criteria were defined to satisfy constraints on various response quantities, including drift, base shear, ductility, residual story drift, and control force. The constraint limits were defined in view of performance-based design requirements for the benchmark structure. The performance of the controllers was contrasted with that of traditional LQG, and significant reductions of all response quantities were achieved for design-level earthquakes.

Seismic Assessment and Retrofit of Pre-Northridge High Rise Steel Moment Resisting Frame Buildings with Bilinear Oil Dampers

This paper presents quantitative information on the effectiveness of seismic retrofit solutions using bilinear oil dampers for seismically deficient existing tall steel buildings. For this purpose, a benchmark 40-story steel space moment-resisting frame building is studied that represents 1970s design practice in North America. Rigorous seismic performance assessment based on ASCE 41 recommendations reveals a high collapse risk for the existing building. The local engineering demand parameters are comprehensively assessed to quantify the impact of seismic retrofit on steel columns and column splices, which are particularly vulnerable due to the time of construction. Multiple retrofit schemes are explored with numerous damping levels and vertical damping distribution methods. The dampers are designed via a recently developed multi-degree-of-freedom performance curves method. A new balanced vertical damping method is proposed to account for the effects of frame inelasticity. This strongly depends on the supplemental damping level, and it determines the effectiveness of the employed vertical damping distribution method. The results indicate that the proposed retrofit strategies can minimize the collapse risk of the tall building. It is shown that the balanced vertical damping distribution method provides the most uniform drift distribution along the building height. Despite the reduction in story drift ratios, the axial force demand in exterior columns remains relatively high in the bottom stories regardless of the seismic retrofit solution. On the other hand, bilinear oil dampers produce relative constant forces despite exhibiting higher velocity demands than expected.

Residual storey drift estimation of the MDOF system with the weak storey under seismic excitations using the BP network

This paper focuses on estimating residual storey drifts of multi-degree-of-freedom (MDOF) systems with the weak storey due to seismic excitations. According to the distribution of yield strength coefficients, MDOF systems are categorized into two types: a uniform MDOF system and a non-uniform MDOF system. Through elasto-plastic time history analysis, typical MDOF systems were analyzed considering the P-Δ effect under 60 earthquake records free of near-fault effects. The influences of various structural parameters on distribution characteristics of residual storey drifts along the height of the MDOF systems were investigated in detail. Finally, a back propagation (BP) network model was proposed to estimate residual storey drifts of the MDOF systems with the weak storey under seismic excitations. The results indicate that the maximum residual storey drift usually occurs at the weak storey for a non-uniform MDOF system while at the bottom for a uniform MDOF system. In addition, the larger the overall yield strength coefficient, the yield strength modification factor or the post-yield stiffness coefficient, the smaller the residual storey drift of the MDOF system on the whole. Moreover, the proposed BP model can sufficiently consider the parameters affecting residual storey drifts of the MDOF system with the weak storey, while having a good accuracy and a high efficiency in estimating the residual storey drifts.

Seismic Analysis of Soft Storey Building in Earthquake Zones

In this paper (G+8) building is modeled like a bare frame, a bare frame with the shear wall, and a bare frame with X bracing by changing the soft storey to different floors. The static analysis effect is determined for all three models with zone IV and zone V using Staad pro-V8i software. The main objective of the research was to assess the impact of a soft storey in various earthquake zones and by varying places of the soft storey from first to the top floor and for frames with different column shapes by seismic analyses in staad pro. The results of variable building models are obtained from the research regarding various parameters such as displacement, storey drift, and base shear. More significantly, comparing different structural systems revealed a reduction in lateral displacement and story drift. The shear wall reduced the Storey Displacement by 98.838% and storey drift by 99.86%. The Steel bracing reduced the Storey Displacement by 97.846 % and storey drift by 92.6%. Finally, it has been found that the Shear wall reduces lateral displacement and storey drift, thus significantly contributing to greater structural stiffness. The analysis results recommended that the shear wall use reinforced concrete frames for the seismic hazard zones and the Steel bracing recommended for the low seismic zones.

Seismic response of RC framed irregular structures

Earthquakes are one of the most unpredictable and deadliest of all-natural disasters; nevertheless, because of their unpredictable character, it is difficult to prevent human deaths and property loss if structures are not designed to withstand earthquake forces. A structure can be classified as irregular if it has an irregular distribution of stiffness, mass, and strength, or because of an irregular geometric configuration. However, previous earthquake records suggest that these constructions have a poor seismic performance. In the present research study, effects of irregularities are compared with regular buildings of different stories in seismic zones II & IV. Irregular buildings with mass irregularity, stiffness irregularity, geometry vertical, and plan irregularity are considered in the present paper. Earthquake analysis is carried out by using linear dynamic analysis i.e. Response Spectrum method. The parameters considered being story lateral loads, story displacement, story drifts, story shear, and story stiffness using ETABS. As a result of the analysis, Story lateral loads, Story shear and Story stiffness were observed to be maximum in regular buildings as compared to irregular buildings. The story displacement and story drifts are maximum in the irregular building as compared to regular buildings. Response spectrum curves are drawn for regular and irregular buildings and concluded that accelerations are greater in zone IV than zone II.0.

Performance analysis of asymmetrical RC structures using different configurations of shear wall

The construction of unsymmetrical or irregular buildings is increasing due to functional requirements and aesthetic considerations. Ductility, lateral strength and stiffness are the major factors which affect the seismic behaviour of all buildings. The irregular shape, dimensions, and geometry of a building have a significant impact during an earthquake. Buildings with simple geometry in the plan have endured strong earthquakes in the past with little damage; however, buildings with asymmetric shapes have been severely damaged. Structural damage and failure in asymmetric buildings during powerful ground motions are due to torsional effects and should be minimised by shortening the distance between the centres of mass and stiffness. In the present study, torsion is minimised according to the centre of mass and rigidity and analysis of the buildings (B1 + G + 10) storey with different irregular (L, H, U and E) shapes considering different shapes of shear walls at different locations. The location of the shear wall is decided according to the centre of mass and rigidity. The analysis has been done in ETABS software tool. Variables such as the torsional effect, displacement, storey drift, stiffness, base shear and time period, and modal mass participation ratio were analysed for several models, and the findings were compared. The results prove that T shape shear wall performs better in all irregular buildings.

Seismic analysis of high-rise building with tuned mass damper and core column

Earthquakes are one of the most vulnerable disasters that effected many countries including India. Due to continuous ground motions caused by an earthquake the structure gets damaged or even collapses causing human loss, property loss and psychological fear among humans. Many techniques are available to resist the structure from seismic loads like base isolation devices, seismic dampers, shear walls, outrigger structure, braces. All of these devices aid in lowering the structure’s responsiveness, but they also have their limitations. Once a major earthquake strikes the structure, these devices must be replaced. The newest technology structures that use Tunes Mass Damper (TMD) and ancient technology Core Column (central pillar or shinbashira) function better during earthquakes. In order to reduce the vibration of the building, the TMD is tuned to the same damping ratio of the main structure, whereas Core Column is placed at the centre of the building throughout the height. In this project, a 40-storey three dimensional RCC building without any devices, with TMD and with Core Column in seismic zones V, with soil type-medium will be modelled and analysed using SAP2000 v.20 software. As to IS 1893: 2016 Part-1, dynamic analysis, such as Time History analysis of Bhuj 2001 earthquake and El – Centro 1940 earthquake will be performed. Maximum displacement, storey drift, and maximum accelerations are recorded as responses to the analysis. The data from the results are plotted using MATLAB software.

Designing a drilled pile foundation in a dual system structure

Drilled pile foundations that have been set in hard soil are generally used for buildings with shear walls. By nature, a drilled pile foundation can withstand moments because of the drilled pile’s dimensions and the amount of reinforcement installed. This study presents a structural analysis of a 10-story building supported by a dual system structure to meet earthquake requirements. The results show that, by using a dual system, the earthquake requirements (natural period, modal, story shear, story drift, and P-Delta) are met. Other results show that the base shear force of the shear wall has a value of 58.76% for the X-direction and 63.72% for the Y-direction. The base shear force value of the frame is 41.23% for the X-direction and 36.27% for the Y-direction. Therefore, the requirements of the dual system are met because the resisted base shear force of the frame is higher than 25%. The dual system provides a normal force value of 24.32% for the shear wall, while the frame carries 75.67%. The bearing capacity of the drilled pile with a safety factor = 2.5 is 162 tons for a diameter of 50 cm, 214 tons for a diameter of 60 cm, 340 tons for a diameter of 80 cm, 493 tons for a diameter of 100 cm, 672 tons for a diameter of 120 cm, and 993 tons for a diameter of 150 cm. The result of the pile driving analyzer test values for a 120 cm diameter range from 988 to 1,232 tons.

The impact of plan irregularity on multistory building response: A pushover analysis

Structural irregularity often stems from a combination of plan and elevation irregularities, as perfect regularity is seldom achieved in real structures. Defining structural irregularities is challenging due to their varying nature. While scientific literature tends to separate plan and elevation irregularities, there's a need to understand the behavior of real structures that possess plan irregularities. This paper investigates the impact of plan irregularities on multi-story building responses through pushover analysis. The study aims to evaluate various parameters such as capacity curves, performance levels, story drifts, and displacements for irregular building models compared to regular ones. Four and eight-story buildings are designed according to Indian standards, and nonlinear static analysis is conducted using a plastic hinge model. Plastic hinges are assigned at possible failure locations, and pushover analysis is performed. Eccentricity is incorporated by shifting the position of live loads and adjusting column dimensions on both sides of the axis of symmetry at eccentricity values of 10%, 20%, 30%, and 40%. Displacement-controlled pushover analysis is conducted, and pushover curves are obtained in the X direction. The performance of building models is compared with a regular reference frame. Capacity curves, performance points, and story response plots are analyzed using ETABS 9.7.0. The results indicate a reduction in base shear capacity with increasing irregularity, with eccentricity showing a greater effect than soft story irregularity. Irregularity also influences the height-wise variation of story drifts differently.

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 analysis of Multi storey Building on Sloping Ground and Flat Ground by using ETABS

Due to urbanization and industrialization, which paved the door for the development of tall, multi-story structures on mountainous terrain, land is scarce in emerging nations like India. Buildings built on hilly terrain differ from those built on flat terrain due of their uneven and asymmetrical vertical and horizontal structures. These buildings are also significantly more vulnerable to earthquake pressures when located in mountainous terrain. The primary goal of the current endeavor is to investigate how structures behave on level and sloping terrain. Hilly places require different construction configurations than level areas. Hill structures vary from those on lowlands in that they are torsionally linked, highly irregular, and asymmetrical in both the horizontal and vertical planes. As a result, they are vulnerable to severe damage when an earthquake strikes. The behavior of a multi-story structure with two distinct slope angles was attempted to be studied in this paper, and a comparison with flat ground was made. by taking Earthquake Zone II into account. Buildings on level ground and buildings on slanted ground are compared. The models are created with the aid of the structural analysis program ETABS. Response spectrum analysis is used for analysis. The analysis’s findings, including storey shear, storey drifts, moments, and displacement, are tabulated and examined.

Comparative Study on Seismic Performance of Steel Building & Composite Building with CFT & CFST Column

In this paper a comparative study is done on Steel building & Composite building with CFT, CFT with stiffeners, CFDST Hollow & CFDST column. Seismic Analysis of (B+G+9) building is done in both Equivalent Static method & Response Spectrum method using ETABS software & Optimum Composite column is obtained from Parameter 1 (Steel Ratio, Buckling Load, Plastic Resistance, H/T Ratio), Parameter 2 (Displacement, Story Drift, Base Shear, Overturning Moment, Story Stiffness), Parameter3 (Moment of Inertia, C/S Area, Total Weight, Total Tonnage).