Story Stiffness Research Articles

A Comparative Study on Seismic Behaviour of Plan Irregular Buildings

Abstract: Asymmetrical plan irregularities occur when the horizontal layout of a building is non uniform or unsymmetrical in one or more axes. These irregularities may arise from variations in building shape, size, or configuration, leading to nonuniform distribution of mass, stiffness, or load paths throughout the structure. Considering equivalent static analysis (ESA) and response spectrum analysis (RSA) as per IS 1893-Part 1 (2016) considering seismic zones III, structure with square shaped plan performs better than the other shaped models (viz. T, L, H and Plus shapes) with least values of storey displacement and storey drift ratio, and also with higher value of storey stiffness. Thus, square plan shaped structure is seismically more resistant than T, L, H and Plus shaped structures.

Overturning Resistance of Structure Base-Isolated by Laminated Rubber Bearing Considering Pounding Against the Moat Wall

The overturning resistance of structures base-isolated using laminated rubber bearings (LRBs) is crucial to the stability of the structure due to the poor tensile performance of LRBs. Pounding occurs between the structure and moat wall, which can result in a reduction of the overturning resistance of the structure. This study aims to investigate the overturning resistance of a structure base-isolated by LRBs considering pounding against the moat wall based on numerical simulations. The influence of the gap size, pounding stiffness, and the horizontal stiffness of the isolation storey on the overturning resistance of the isolated structure was evaluated through parameter studies. The results indicate that poundings between the structure and moat wall result in short but large pounding forces. Pounding forces would amplify acceleration, inter-storey drifts of the isolated structure, and significantly increase the risk of overturning of the isolated structure. Increasing the gap ratio can improve the seismic performance of the structure. Larger pounding stiffness leads to greater pounding forces generated by the structure, and the risk of overturning of the structure increases. The coefficient of overturning resistance initially decreases, and then increases, as the stiffness of the isolation storey increases.

Comparative Seismic Analysis of Regular and Irregular Multistorey Structures with and without Bracings and Shear wall

Abstract Seismic effect is one of the main factors which has to be considered during the design of structure. Earthquake is one of the supreme hazards for living and assets on earth. It is a natural phenomenon, occurring with uncertainties as a result of sudden release of energy within earth crust in the form of seismic waves. As the earthquake forces affects the stability of the building and about 60% of region in our country is under the influence of seismic forces, the buildings are provided with alternatives to withstand the horizontal forces and to increase the strength, stability and stiffness. Present paper investigates the performance of different structures provided with seismic resisting components. In this paper Shear walls and bracings are incorporated to make the structure moment resisting frame. A comparative seismic analysis of high-rise structures with and without shear walls and bracings is included in this discussion which is done using ETABS 2019 software by Response Spectrum Analysis. The parameters considered for analysis are natural frequency, natural time period, base shear, story stiffness, story displacement and story drift. in constructing both.

Progressive collapse of regular RC structure considering flexibility of slabs under gravity and wind loads

Abstract Progressive collapses are disastrous phenomena which occur in the structure due to manmade incidents or natural disasters. There are not any significant studies considering the flexibility of slabs in the structures, as an alternative to treating them as rigid diaphragms. The present study deals with the progressive collapse of a regular reinforced concrete structure considering flexibility of slabs, comparing the same when the slabs are considered as rigid diaphragms. 20 storey(G+19) building is modeled using ETABS software and nonlinear static analysis is performed under the action of gravity and wind loads. At the outset, the analysis is done for undamaged structure to find the behavior of structure and then the damaged models have been analyzed by removing one of the critical column in different locations at first storey, based on general services administration (GSA) guidelines[16]. Various response parameters such as base force capacity, storey stiffness and storey displacements have been compared for undamaged and damaged structures considering and not considering the flexibility of slabs. From the comparison of the results, it was noticed that the chance of progressive collapse is high when the corner column is damaged and also resistance to wind load is considerably higher when stiffness of slabs is considered for the analysis in both undamaged structure and the four cases of damaged structure (ii), which is about three times higher.

Numerical hybrid simulation assessment of E‐BRBF and E‐FBF systems for mitigating P‐delta effects and enhancing post‐earthquake performance

AbstractThis article investigates the seismic stability of E‐BRBF and E‐FBF systems previously proposed as stability‐enhanced alternatives to conventional BRBF and FBF systems. The E‐BRBF system is a buckling restrained braced frame with an inverted‐V brace configuration in which one of the two braces is a conventional brace designed to remain elastic during a strong earthquake. When the buckling restrained brace (BRB) yields, an unbalanced vertical force develops at the brace‐to‐beam connection, which imposes flexural demand on the beam and creates a positive post‐elastic storey shear stiffness. The E‐FBF system is identical except that the buckling restrained braces are replaced by conventional bracing members constructed with an end friction connection designed and detailed to slip at a predetermined load. At every storey, the beam and the elastic braces are designed such that this post‐elastic stiffness is sufficient to cancel the negative storey shear stiffness resulting from P‐delta effects and introduce a re‐centring mechanism to achieve an enhanced performance in steel buildings subjected to interface subduction earthquakes. Using distributed plasticity numerical models, past studies demonstrated the effectiveness of E‐BRBF and E‐FBF systems in mitigating P‐delta effects, emphasizing the importance of a stable and predictable response of the beam, which is a critical element in the scheme that provides the post‐elastic stiffness of the system. This beam is subjected to axial and flexural demands and must remain near elastic to ensure the global seismic stability of the structure. The response of the beam can be affected by localized yielding and local instability effects resulting from residual stresses, stress concentration near gusset plate connections and geometric imperfections. Employing a refined nonlinear finite element model of the beam element, this article assesses the performance of 10‐storey E‐BRBF and E‐FBF systems utilizing multi‐platform numerical hybrid simulations. The evaluation involves static‐monotonic and dynamic response history analyses, incorporating seismic excitations representing Vancouver, BC's seismic hazard (Crustal, In Slab, and Subduction Interface). In the hybrid simulation model, the most critical member for the proposed system (i.e., first‐storey beam) is sub‐structured in ABAQUS using solid elements, while the remaining frames are integrated using OpenSees using fiber‐based sections. Numerical hybrid simulation dynamic nonlinear response history analyses demonstrate the adequacy of the E‐BRBF and E‐FBF systems in mitigating P‐delta effects with residual drifts within repair limits, unlike conventional systems where instability or excessive drifting occurred. Monotonic Pushover hybrid simulations reveal a more ductile beam behavior compared to standalone models, in which frame members are entirely modeled in OpenSees. The analysis also indicates a ductile plastic hinging beam failure mechanism with no instability failure modes at extreme drifts.

Comparative Study of Conventional Structure and Mivan Structure Using ETABS

Abstract: With rapid urbanization and industrialization, the demand for construction has surged to accommodate this expanding population. However, limited land availability has necessitated vertical construction over horizontal expansion. MIVAN technology has emerged as a viable solution, employing concrete instead of traditional masonry walls, particularly suitable for high-rise buildings. In this study, conventional and MIVAN structures with varying wall thicknesses is analyzed and compared using ETABS software with Response Spectrum analysis. Results show significant decreases in displacements, story drifts and time period in MIVAN structures, particularly with a wall thickness of 300mm for I-shaped structures. Additionally, MIVAN structures with 300mm walls exhibit higher story shear and stiffness, indicating better performance under seismic conditions compared to other shapes. Thus, MIVAN technology with 300mm walls in I-shaped structures offers superior seismic resilience in tall buildings.

A Comparison Analysis of Buildings as per Norwegian and Ethiopia ES-EN1998-1 Seismic Code

An earthquake is one of the most significant and shocking natural disasters ever documented anywhere on the planet. Throughout history, it has claimed millions of lives and wreaked devastation on infrastructure. Because earthquake forces are spontaneous and unpredictable, engineering methods must be honed to investigate buildings under the impact of these forces. The dynamic and static computations of four RC multistory structure prototypes with various elevations in a high seismic zone are compared in this paper. The project under review is modeled as a 3, 6, 12, and 18-story establishment, and it is analyzed employing ETABS vs. 2019. The Equivalent Lateral Force (ELF) Procedure is used for static experimentation, while the Response Spectrum (RS) Procedure is employed for dynamic investigation. Both calculations are performed as per the EUROCODE 8-2004 recommendation. The ELF seismic load practice utilized was for the country of Norway, which has similar parameters to the ES-EN 8-15 seismic regulation Type I target RS, with ag/g = 0.1, spectrum type = I, soil factor S = 1.3 ground type, spectrum period (Tb, Tc, and Td) 0.1 s, 0.25 s, and 1.5 s. For the RS investigation, the parameters employed are as per ESEN-2015, ag/g = 0.1, and the spectrum type = I and ground type = B parameters were involved in the same manner for the RS analysis. The soil factor was set to 1.35; the spectrum period was set to (Tb, Tc, and Td) 0.05 s, 0.25 s, and 1.2 s. The behavior factor = 3.8, the lower bound factor = 0.2, and the damping ratio = 0.05. The results are then compared by employing different components such as displacement, story drift, story stiffness, base story shear, and story moment. Ultimately, a comparison of static and dynamic investigations has been carried out. Compared to the RS approach, the ELF technique produces more additional displacement, total drift, and base shear. As per the findings of this paper, for high-rise and tall buildings, dynamic analysis such as RS should be used rather than static analysis (ELF).

Seismic Analysis of Horizontal and Vertical Irregular RC Multi Storey Building With Effect of Opening in Shear Wall

At present days building a structure with all the regular configurations is not feasible in most of the cases due to the irregular plot dimensions, aesthetic visual and functional requirements in the urban cities. The structure with more irregular configuration either horizontally or vertically are more vulnerable to earthquake which leads to collapses of structure, property loss and casualties. The shear walls are commonly used as a vertical element. Shear walls may have one or more openings for functional reasons such as windows, ventilation and other types of openings in shear wall. Frequently the shear wall is provided with openings thus necessary to study effect of irregular building. The present study was carried out the opening in shear wall with different shape of RC multi-Storey building and Study different building model with Combination of Horizontal & Vertical irregularities. The models were created using the ETABS software with Full Shear walls, Shear walls with a 25% opening. The location of the Shear wall was optimal. Prepared models of G+9 story and Analyze the model by Response Spectrum Analysis and Compare the Result with different buildings layout with parameters like storey Displacement, Storey Shear, Storey Drift, Storey Stiffness, Base shear, Torsion, Time Period and Mode Shape

Performance Assessment of Commercial Building for Symmetric and Asymmetric Plan Configurations in Different Seismic Zones of Bangladesh Using ETABS

Bangladesh is among the nations most vulnerable to earthquakes worldwide. Being a developing country, it has been a challenging issue to ensure commercial prosperity along with safety against seismic hazards. Structural engineers also face difficulties in accurately designing buildings with maximum economy and efficiency. ETABS, a leading global engineering software with BNBC 2020 guidelines plays a vital role in these cases. In this study, analysis of a B+G+6 storied building for Symmetric & Asymmetric Plan configuration has been performed using ETABS software. Both kinds of structures have experienced a range of loads for example- dead loads, live loads, partition loads, wind loads, and seismic loads, as well as load combinations that have been pursued following BNBC 2020 requirements. The objective of this work is to evaluate the seismic impact resulting from varying seismic coefficients for four seismic zones in Bangladesh, given identical symmetric and asymmetric plan arrangements. Four required metrics were evaluated between the structural performances of symmetric and asymmetric structures: storey drift, overturning moment, storey shear, and storey stiffness. The structural software provided the analytical results and parameter computations. The comparison's result demonstrates that the asymmetric structure exhibits greater storey rigidity and less storey drift over the longer axis.

Frequency response function-based closed-form expression for multi-damage quantification and its application on shear buildings

Vibration-based damage identification techniques have gained popularity immensely in the field of structural health monitoring (SHM). Frequency response function (FRF)-based damage quantification is mainly performed based on iterative model updating techniques. Most of these methods are time-consuming and erroneous in higher modes. Spectral element method (SEM) can overcome some of these limitations and can determine FRF expression directly for a broad class of civil structures. However, a closed-form expression for multiple damage severity is not proposed to date. In this study, an FRF-based formulation for quantifying damage has been proposed with the help of SEM in order to bypass the mode shape extraction for damage identification. To determine the effectiveness of the proposed formulation both numerical and experimental studies have been performed. A numerical simulation has been performed on a 14-storey shear building. Damage has been introduced by reducing the storey stiffness at intermediate and adjacent storeys. It has been perceived that damage severity at any storey can be estimated with only 3 sensors, one at the top storey and two others at the adjacent floors of the desired storey. To verify the effectiveness of the proposed expression, an experimental study has been carried out on a 9-storey miniature model. It has been observed that the first resonating peak amplitudes of the responses recorded simultaneously at desired locations of intact and damaged structures are sufficient to estimate the damage intensity. Thus, the proposed formulation is efficient as an output measurement-based approach. The novelty of this study lies in the proposed closed-form FRF-based multi-damage severity expression involving minimum number of sensors and without any information on the input excitation. The results obtained from both numerical and experimental study showcase the robustness, simplicity and applicability of the proposed formulation.

The role of masonry infills on the interstory drift demand of reinforced concrete frames

Most frame buildings, especially those with shear-type moment resistance frames, are affected by masonry infill panels, which change the mechanical properties of whole systems in a big way. In turn, seismic performance varies depending on the infill panel and frame interactions. In conventional structural design practice, such interaction has been overlooked. This study looks at the range of local displacement demands in shear-type frames with and without infill panels. Generic frames are developed by tuning the story stiffness and mass to produce a reasonable period range between 0.2 and 2.0 s. The masonry infill panels are simulated through equivalent diagonal struts. A Bouc–Wen-based hysteretic model is applied to incorporate the post-yielding hysteresis degradations of both columns and masonry panels. The hysteresis loop control parameter values are also given for incorporating masonry infill properties. The correlation analysis between the strength and stiffness of RC frames and masonry infills is supplied as an instrument for calibrating the hysteretic model. In the collection of records, there are a lot of near-fault ground motions, which puts a lot of seismic demands on the buildings. The modification factors via regression analysis are proposed using over 1254 nonlinear response history analyses. This modification factor is figured out by looking at the difference between the mean drift spectrum for a set of generic frames that are both bare and filled. The nonlinear analysis shows that residual drift demands can be reduced in the case of panel effects that exist for masonry-infilled mid-rise RC shear-type frames.

A comparative analysis of RCC and composite buildings using the new plastic deformation (PD) method

Low computational efficiency and non-linearity behaviour make the simulation of the overall building structure problematic to attain with a single dynamic or static method. Thus, this paper uses a plastic deformation (PD) method based on concrete plasticity theory (CPT) for comparative analysis of multi-storey reinforcement cement concrete (RCC) and composite buildings under common and rare earthquake loads. For this purpose, a 15-storey tall building was selected for analysis using ABAQUS software. At first, a possible building model was created and then plastic deformation analysis was performed using the new PD method under both common and rare earthquakes. After that, a nonlinear time history analysis was conducted, and the results of plastic strain distribution, lateral displacement, peak acceleration, storey stiffness, shear force, storey drift, normalised shear, and top deflection of the RCC and composite buildings were studied deeply. The fundamental time period of the RCC model was found to be 5.2 s while the fundamental time period of the composite model was 6 s. Under common and rare earthquake leads, the peak acceleration of the RCC building was 19% and 22% higher than composite buildings, respectively. Under common and rare seismic loads, the top deflections of the composite building were 33% and 36% higher than those of RCC buildings, respectively. In the case of the RCC building, it was found in this study that higher peak acceleration (PA) of the ground motion led to higher storey top displacement, storey drift, shear force and top deflection under both ground motions. Numerical results suggested that the use of composite structure is more durable than RCC structure. It was also concluded that the PD method could also be effectively used for the analysis of RCC and composite buildings under dynamic loads.

Seismic reinforcement effect and vibration test of externally attached substructures in a selected Japan school building

In the long-term seismic work in Japan, an effective seismic reinforcement design system and reasonable seismic reinforcement technology have been developed, which is worth learning from. In this paper, the seismic reinforcement of a school building in Japan is taken as an example. Firstly, an overall reinforcement scheme of external prestressed precast concrete (PC) frame and steel brace is proposed. Then, based on the calculation results of seismic reinforcement and the ambient measurement before and after seismic reinforcement, the effectiveness and rationality of the seismic reinforcement method are analyzed. The results show that the seismic reinforcement method of attached substructures changes the original structural system, and solves the problems of excessive deformation and insufficient seismic performance. The reinforcement method improves the story stiffness of the structure, and the vibration period of simple harmonic motion after the implementation of seismic reinforcement is reduced by 0.845 times at most. The research results can provide reference for seismic reinforcement design and performance evaluation of existing school buildings.

Seismic Response of RCC Buildings on Hill Slopes with Step Back and Step Back - Set Back Configuration

Framed structures constructed on hill slopes have different structural behavior than those on flat ground due to the scarcity of flat land. As these buildings are unsymmetrical, they attract large amounts of shear forces and torsional moments, leading to unequal distribution due to varying column lengths. In this study, the dynamic response of hill buildings has been compared with step back and step back set back building without and with bracing at corner of the building in terms of maximum storey stiffness and storey displacement. Two different types of buildings have been modeled and analyzed using ETABS v 18.0 finite element code. A parametric study has been conducted, in which hill buildings are geometrically varied in height of the structure due to hill slope. All sixteen analytical models have been subjected to seismic forces along and across the hill slope direction and analyzed by using the Response Spectrum Method.
 All 16 models were analysed using ETABS v18. Three dimensional space frame analysis is carried out for four different configurations such as step back buildings with bracings at corner of the building, step back buildings without bracings, step back and set back building with bracings at corner of the building, step back and set back building without bracings. The maximum storey stiffness and storey displacement for the step back and step back-setback buildings with and without bracing are at 15 ͦ and 30 ͦ, respectively, compare with bracing buildings, the value in step back & step back set back building drastically decreases, resulting in the stability of the building.

Initial stiffness estimation method for wooden house considering non‐structural elements using design information and microtremor measurement

AbstractIn this paper, a previously proposed method for story stiffness estimation of steel residential house is extended to estimate story stiffness of wooden residential houses considering non‐structural walls based on the available design information, that is, story weights, wall type, wall length, and wall opening type. Microtremor measurement data of several newly constructed buildings are used to determine unknown model parameters of stiffness estimation function, which minimize the estimation error of eigen frequency. The proposed method can simultaneously estimate the standard stiffness of wall element common to the same specification and the effects of wall opening and wall shape. The validity of the proposed method is examined by using measured actual microtremor records and drawing information of wall types and wall lengths of 19 wooden residential houses.

Influence of torsional effects in seismic retrofit of RC buildings

The nonlinear static procedures are very popular for the design and assessment of buildings subjected to earthquake ground motion in current structural engineering practice. Their application and relative accuracy are very relevant issues, especially in the case of seismic retrofit of irregular and/or high-rise buildings. Many retrofit design procedures are valid for low-rise buildings and/or neglect torsional effects and higher modes contribution. Often, the vibration properties are considered unchanged after retrofit, and the higher modes are neglected. Other ones are based on the proportional stiffness criterion (i.e., lateral story stiffness due to the additive structures is considered proportional to that of the original main structure). Still others rely on the hypothesis that the main structure remains elastic. Often, they neglect the interaction between the main structure and the additive structures used for retrofit. These are very significant drawbacks in the case of plan-asymmetric buildings, where torsional effects are important. In this case, the seismic response is dominated by harmful torsional effects and, thus, the retrofit strategy should significantly modify the dynamic response. To overcome such drawbacks but still keep the simplicity of using equivalent pushover analysis, this paper develops a “two-step” pushover procedure for seismic retrofit of plan-asymmetric buildings using buckling restrained braces based on steel hysteretic dampers (HBF). To this aim, a real case-study school building has been considered in the analyses. A design method has been implemented to size buckling restrained braces to be placed on selected spans and stories of the building. The effectiveness of the retrofit strategy has been finally demonstrated by nonlinear time-history analyses under different sets of earthquake-strong ground motions.

Non-Linear Pushover Analysis Of RCC Framed Structure By Providing Fluid Viscous Dampers At Different Locations

The increasing need of shelter in urban cities due to overpopulated spaces and land inadequacy people are forced to keep space and their needs strictly limited. High-rise buildings are the best solution for providing people spaces for living and to work on. In this age of urban development and rapid modernization the need of high-rise structures is rapidly increasing. As structures have become higher, structural engineering has become more difficult to achieve appropriate stability criteria. In tall buildings, stiffness is the key to sustainability. Fluid Viscous Dampers (FVD) are one of the efficient solutions for tall structures. These are hydraulic devices that, when stroked, dissipate the energy placed on a structure by seismic events. The viscous dampers convert the kinetic energy of the structural movement into heat and then dissipate that energy into the air, thereby obeying the laws of physics through the conservation of energy. To determine effectiveness of FVDs as well as determine best location for FVDs in high-rise buildings subjected to seismic loads, the current research is being carried out.In this study twelve (12) RCC framed structures of 15 storeys of which four (4) are square shaped in plan, four (4) are rectangle shaped in plan with sides of ratio 1.5:1 and the other four (4) are rectangle shaped in plan with sides of ratio 2:1. These three (3) different shaped buildings considered are having approximately same plan area and damper positions. A floor-to-floor height 3m is taken. The buildings are located in Zone III. By using ETABS 2017 software, which helps to analyse and design the models, the analysis method used for this study is the Push Over analysis. This research work presents the results of an investigation on different parameters like Base shear, Modal mass participation, Time period, Storey Drift, Storey Shear and Storey Stiffness.

Seismic Performance Assessment of RCC Building with Podium

With the advancements in structural engineering, seismic performance of buildings can be adjudged on the basis of performance-based techniques. This paper presents the performance based seismic evaluation of buildings with podiums for varying ratios of tower area to podium area. The structural system of the building consists of shear walls and moment resisting frames. Buildings with podiums have been designed and analysed with and without connection between the tower portion and the podium portion for Seismic Zone IV, by carrying out response spectrum analysis as per IS 1893-2016. The structural responses have been compared in terms of diaphragm forces, base shear, time period, storey stiffness, storey shear, storey displacement etc. for the variations in number of podiums i.e., single, double & three podium levels. Performance-based seismic evaluation of the buildings has been carried out with podium and tower as a connected unit with varying ratios of 0.35, 0.45, and 0.55 of tower area to podium area i.e., by keeping the tower area constant and increasing the podium extents. Pushover analysis is carried out and comparison is done for the influence of podium on the non-linear behaviour of the structures.

Analysis of Multi-Storied Buildings with the Use of Coupled Shear Walls

The present study focuses on the use of coupled shear walls with and without dampers for resisting seismic loads. Multistory structures with and without shear walls are analysed. Different parameters, such as the structure's base shear, storey drift, storey displacement, storey stiffness, and storey shear, are evaluated, and a comparative study is performed. It is observed that coupled shear walls with fluid viscous dampers reduce storey drift by 24% and storey displacement by 45% when compared to buildings without shear walls. A coupled shear wall with a damper has a 29% higher stiffness than a coupled shear wall without a damper, thus performing effectively in resisting lateral forces induced by an earthquake.

Experimental Investigate on Seismic Performance of RC Hill-Side Stilted Buildings Affected by Vertical Stiffness Irregularity

ABSTRACT In this study, the ratio of lateral stiffness of the stilted story to that of the second story was proposed as the story stiffness ratio (SSR) to quantify vertical stiffness irregularities of hillside stilted buildings. A quasi-static experiment was conducted on a plane stilted frame with an SSR of 40 in the slope direction. Experimental results were compared with those of a stilted frame with an SSR of 1.01. The results show that SSR is an important factor influencing seismic failure modes of stilted buildings. As SSR decreases, structural ductility and deformation capacity improve, and stiffness degradation decelerates.