Plan Irregular Buildings 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.

Seismic evaluation of plan irregular reinforced concrete building equipped with comb teeth metallic passive damper

Active and passive damping devices exhibit significant energy dissipating behavior under seismic loads and are being used to control vibration in buildings worldwide. Comb Teeth Damper (CTD) is one of the most promising recent types of passive dampers which consist of steel plates with multiple teeth designed to dissipate seismic energy by in-plane flexural yielding. In this study, the CTD was modeled and analyzed under lateral cyclic load using the finite element analysis software, ABAQUS. The first phase of this investigation was a comprehensive parametric study on CTD with two different numbers of teeth, namely 4 teeth (4 CTD) and 5 teeth (5 CTD); each model with six different thicknesses, namely 5, 10, 15, 20, 25, and 30 mm. The parametric study showed that by increasing the number of teeth, the load-carrying capacity, initial stiffness, and energy dissipation capacity have increased considerably. A similar trend was observed when the thickness of the damper was increased. From the results of the parametric study, 5CTD with 15 mm thickness damper model was identified as a suitable model for utilizing in Reinforced Concrete (RC) buildings using optimization algorithm. In the second phase, a G + 14 storey plan irregular RC building was modeled in the structural engineering software ETABS and subjected to six different strong earthquake ground motions. The non-linear time history analysis was performed on the building with and without identified CTD and found that the building equipped with dampers reduced 56% top displacement, 60% inter-storey drift, and 33% energy dissipation.

Seismic Analysis of Re-Entrant Corner Plan Irregular Buildings with Roof Openings Using STAAD Pro: A Case Study for Zone III Earthquake Intensity

Seismic Analysis of Re-Entrant Corner Plan Irregular Buildings with Roof Openings Using STAAD Pro: A Case Study for Zone III Earthquake Intensity

Comparative Study of G+6 Irregular Multistoryed Building of Different Shape of Diaphragm

Abstract: This study investigates the effectiveness of incorporating openings in the roof of re-entrant corner plan irregular buildings at different locations under earthquake loads. Five models with varying degrees of diaphragm discontinuity were analysed using STAAD Pro software. Node displacement, storey shear in X and Z directions, stress values, and maximum bending moment were evaluated to assess structural performance. Results indicate that models with higher diaphragm discontinuity exhibit increased node displacements, storey shear, and stress levels. Model M3, with 17% diaphragm discontinuity, consistently demonstrates superior performance in terms of lower displacements and stress values compared to other models. However, final model selection should consider specific project requirements and design considerations.

Comparative Study of G+6 Irregular Multistoryed Building of L Shape of Diaphragm Discontinuity

Abstract: This study investigates the effectiveness of incorporating roof openings in re-entrant corner plan irregular buildings at various locations under earthquake loads. Three models L-shaped diaphragm discontinuity were analyzed using STAAD Pro software. Node displacement and storey shear in both the X and Z directions were evaluated to assess structural performance. The results indicate that models with square diaphragm discontinuity exhibit increased node displacements and storey shear compared to those with L-shaped diaphragm discontinuity. The model with L-shaped diaphragm discontinuity consistently demonstrates superior performance in terms of lower displacements and shear stress values. However, the final model selection should take into account specific project requirements and design considerations.

Vibration control of seismic forces using viscous dampers and buckling restrained braces in irregular composite buildings

This study addresses the effectiveness of buckling restrained braces (BRBs) and viscous dampers (VDs) in dissipating seismic energy and increasing the seismic performance of irregular composite buildings during earthquake events. The seismic response of steel-concrete composite moment resisting frames of 15 stories with concrete filled steel tubes (CFST) as columns and composite beams was examined with and without seismic protection devices by employing ETABS software using the response spectrum method as per IS 1893:2016 for seismic zone V. Regular and irregular plans characterised the structures. The plan irregular buildings include C and L-shaped buildings. The BRBs and VDs were installed on all the buildings in two configurations: corner bays and centre bays throughout the height. The results showed BRBs and VDs excellent energy dissipation capabilities. VDs contributions were 5%-8% more than BRBs and, therefore, more efficient. Centre bays placement of VDs was most efficient for regular buildings reducing time-period by 60%, maximum story displacement by 57%, base shear by 37%, and maximum interstory drift ratio by 70%. Corner bays placement of VDs was most efficient for C and L-shaped buildings reducing time-period by 55%-60%, maximum story displacement by 63%-65%, base shear by 30% and 13%, and maximum interstory drift ratio by 78%-80%, respectively, making viscous dampers an excellent choice for midrise composite buildings.

Investigating Seismic Vulnerability in Buildings with Plan Irregularities

This study aims to investigate the seismic behaviour of structures with vertical irregularities. The project employs Response Spectrum Analysis (RSA) to assess a vertically irregular reinforced concrete (RC) building. The investigation encompasses the modelling of both a regular and an H-shaped plan irregular building, excluding the ground floor, resulting in a G+7 storey structure. The seismic response of the framed building under consideration during simulated earthquake motions is influenced by the distribution of stiffness, strength, and mass in both horizontal and vertical planes. The primary objective of this research is to conduct a study of the structure's stiffness by examining Regular Structure and Plan Irregular Structure, each with different vertical irregularities. The entire set of building frames is modeled and analysed using Staad.Pro V8i software, and various seismic responses such as base shear, frequency, and node displacement are obtained.

A case study on an innovative seismic performance evaluation procedure for irregular RC buildings

Assessing the structural capacity of an irregular structure requires an appropriate and robust representation of the analytical model. Conventional procedures are flawed because they lack the reversal effects of higher modes. Therefore, more robust procedures have been tested to accurately capture the capacity of irregular building-type structures. Some of these may be classified as adaptive pushover techniques in which the lateral load vector is revised instantaneously. These adaptive techniques generally refer to SRSS as a modal combination rule to superpose the maximum values of the modal quantities. However, this results in an overestimated capacity value. Furthermore, the reversal effects of the modes are not included in the evaluation process. Hence, in this research, a force-based adaptive multimode pushover method was tested on a plan-irregular building using a code developed and implemented into ZEUS-NL. First, an eigenvalue analysis was used to obtain the modal quantities of the considered building, and subsequently, the modal story shear forces were obtained using the modal story forces. Furthermore, the lateral load patterns were calculated at each iterative step. Finally, the structure was pushed using this calculated lateral load pattern up to a previously calculated target displacement value using a three-step adaptive pushover analysis. The first step is to run an adaptive single-mode pushover analysis considering the first mode. After comparing the fundamental period with a constant threshold limit, it is then decided whether to run an adaptive multimode pushover analysis considering the first two modes or to run two adaptive multimode pushover analyses considering the contribution of both the second and third modes. Neither SRSS nor CQC was used to obtain the maximum response quantities; instead, the use of the envelope response is suggested. After evaluating the capacity diagram of the considered building, the story drifts were determined. The outcomes of the adaptive pushover analyses were later checked with the nonlinear dynamic results. It can be concluded that the result of the tested procedure is in good correlation with the dynamic results. Furthermore, the top displacement–time traces were plotted to check which ground motion record reveals the maximum values. Using the ground motion record, interstory drift ratio–time graphs were developed for each story level and compared with the code limit. Base shear–time history traces were then obtained and compared with the tested FAP. Lastly, story shear–interstory drift relations were plotted to investigate the absorbed energy level as an indicator of damage. As a result, for irregular RC structures, the tested procedure was found to be more accurate. However, in its current form, the procedure reflects the seismic behavior of irregular midrise buildings.

Rational decisions for seismic collapse-prevention design of low-rise asymmetric RC buildings considering deterioration properties

This research points to an essential need to develop a well-defined design method considering the deterioration properties of structural elements. Although the seismic design provisions have changed over the past decades, they ignore the deterioration effects and the collapse probability of frames designed to the latest specifications still exceed the expected norms. The issue becomes more significant for asymmetric buildings where the lateral load-resisting elements behave differently. To this end, several sensitivity analyses are performed using a new index to show the importance of deterioration sources on the seismic performance of analysis models. The evaluation showed that the deterioration effects depend on the torsional flexibility of asymmetric models. The results recommended not to adopt a unique design decision for all resisting frames of an asymmetric building. Simple and efficient design strategies were presented to improve the seismic behavior of plan-irregular buildings up to the collapse state, while keeping their seismic performance the least sensitive to the deterioration effects. Among the proposed approaches, those strategies that vary the plastic rotation capacity of elements have a large effect on the deteriorating behavior.

A Seismic Vulnerability and Fragility of RC Conventional and Monolithic Building

Abstract: This thesis aim is to study the modeling and analysis of monolithic building by STAAD PRO modeling of normal framed building and regular monolithic building have to be conducted and analysis and modeling of different plan irregular building, using equivalent static analysis, modal analysis, response spectrum analysis. The earthquake response of the building and damage assessment and are found out by comparing the analysis result. The earthquake parameters of building is comparing in X-direction. In this study the vulnerability assessment is analyzed by DCR method. In this study we compared the RC building and monolithic buildings analysis with two types of seismic zones

A comparative study on seismic analysis of regular and plan irregular buildings resting on different soils

As the occurrence of earthquakes is increasing day by day, understanding and predicting the structural behavior of buildings in seismic-prone regions is a challenging task, particularly when the buildings are plan irregular. The present research work focuses on analyzing a plan irregular building located in Seismic zone-V and for three different types of soil conditions considered according to Indian Standard (IS 1893 (Part 1): 2016). The analysis has been carried out using the Response Spectrum method in ETABS (Extended Three dimensional Analysis of building Systems) software. Steel fibers, high-strength steel and high-performance concrete are used for the earthquake-resistant design of buildings. The results obtained from the numerical analysis of the irregular buildings are compared with that of a plan regular building for hard, medium and soft soils. The various dynamic response parameters like story displacement, story drift, story shear, story stiffness, fundamental time period and modal mass participation ratio are obtained from the numerical analysis and a comparative study is carried out.

The Reduced-Degree-of-Freedom Model for Seismic Analysis of Predominantly Plan-Symmetric Reinforced Concrete Wall–Frame Building

A reduced-degree-of-freedom (RDOF) model for seismic analysis of predominantly plan-symmetric reinforced concrete (RC) wall–frame buildings is introduced. The RDOF model of the wall–frame building consists of elastic beam–column elements with concentrated plasticity used for simulating cantilever walls and predominantly plan-symmetric RC frame buildings that are represented by the improved fish-bone (IFB) model. In this paper, the capability of the RDOF model is demonstrated for two frame buildings and two wall–frame buildings. The RDOF models were defined directly from the building information model. This is an advantage of RDOF models with respect to single-degree-of-freedom (SDOF) models, while the computational robustness of the RDOF models also makes them attractive for the seismic analysis of building stock. The imposed cyclic displacement analyses conducted for the investigated buildings proved that the condensation of the degrees of freedom for RDOF models was appropriate. Consequently, only minor differences were observed for maximum storey drift IDA curves, maximum storey acceleration IDA curves, and seismic fragility functions for different limit states. However, development is needed to make RDOF models appropriate for preliminary seismic performance assessment of plan-irregular buildings.

Material R-factors of buildings with irregularity

R-factor (Response reduction factor) is an important design consideration in seismic design of structures, which is assumed to consider energy dissipation of structures by means of ductility. So, proper estimation of R-factor is required for seismic design of structures which will account for ductile deformation so that suitable detailing of reinforcement can be done. In case of irregular structures, where the torsion effect is the predominant factor, accurate estimation of R-factor is even more difficult. Therefore, in the present study, an attempt has been taken to determine R-factor for plan irregular buildings. A G +7 storied building is considered and irregularity effect has been incorporated by C and L-shaped configuration. The design of the buildings has been done following Indian Standards. Modeling and analysis have been done using SAP2000. Plastic hinges have been considered to represent material nonlinearity. Mander’s confinement model has been considered. Nonlinear Static (Pushover) following FEMA 440 methods with uniform lateral load variations has been done. Initial tangent stiffness has been followed in equal area method during bi-linearization of pushover curve. It can be stated that apart from material strength and geometrical configuration, performance requirement of the buildings is the most important factor for selection of R-factor.

Collapse safety assessment of plan-irregular buildings considering ductility and damage

The current study focuses on seismic fragility analysis and collapse safety assessment of reinforced concrete buildings with re-entrant corner irregularity. This is conducted in a probabilistic framework on the case studies of moment-frame building archetypes with a typical L-shaped plan. A three-dimensional perspective for ductility and damage distributions is addressed for the non-linear models developed. Multi-directional pushover procedures and incremental dynamic analyses have been performed by applying ten near-field and ten far-field earthquake records for each building model. The median collapse capacity is established through developing fragility curves in terms of several earthquake intensity measures and spatially distributed displacement, ductility and damage indices. Available and acceptable collapse margin ratios (CMRs) are measured to judge the safety margin against collapse at the maximum considered earthquake shaking level. The statistics indicate that when the collapse capacity is defined in terms of the drift, ductility or damage, instead of an intensity measure, the collapse uncertainty decreases. Thus, the median collapse capacity is calculated precisely with less variability, resulting in available CMRs that exceed acceptable CMRs. With the perspective of this methodology, a satisfactory collapse safety margin was anticipated in the seismic force-resisting system by the design requirements for the targeted building class.

Seismic analysis of older and contemporary reinforced concrete frames with the improved fish-bone model

The improved fish-bone (IFB) model for seismic analysis of older and contemporary reinforced concrete frames is proposed by introducing a new procedure for the estimation of parameters of structural elements of the fish-bone model. The procedure makes it possible to approximately account for the importance of structural elements on the seismic response of a frame building and the effect of potential redistribution of demands between structural elements of the frame building. Firstly, the IFB model is described. Follows demonstration of its capability by simulating the response history of storey shears, storey drifts and storey accelerations of selected pseudo-dynamically tested frames. Finally, it is shown that the IFB models can provide pushover curves, the corresponding damage states and fragility functions based on response history analysis which are very similar to those obtained by the conventional multi-degree-of-freedom models. The capability of the IFB model with respect to conventional fish-bone model is also demonstrated by the pushover analysis. It can be observed that the IFB model significantly improves the simulation of the older reinforced concrete frames, which do not fulfil the strong column – weak beam concept, and the frames for which the columns or beams of one storey of a frame building differ significantly from each other. Additional research is needed to extend the capabilities of simplified structural models to plan irregular frame building.

Effect of Infill Wall on Plan Irregular Tall Structure

In the present study, the behavior of plan irregular (C, T, I shaped irregular building and regular building) tall building subjected to the seismic load alongwith the importance of infill wall is considered. The modeling and analysis of (G+14) storey structure for seismic zone (III), soil type (II) with importance factor (1) and M20 grade concrete are carried out, by equivalent static and response spectrum method, as per IS 1893-2016(Part-1), using E-tabs 2015 commercially available software.. The results obtained are discussed in terms of base shear, storey displacement and storey drift. Many critical observations are drawn from the analysis. From these critical observations, it is concluded that, in almost all shape of plan irregular tall buildings, storey displacement and storey drift are found to be more in bare frame when compared with infill frame, whereas the base shear will be less in bare frame compared with infill frame. However, the results obtained amongst the different shapes, indicates that C, I and regular shaped tall building are yielding lesser storey displacement and storey drift compared to T shaped building. Presence of infill walls will increase the stiffness of the frame.

Minimization of Torsional Parameters in Dual Asymmetrical Building through Proper Configuration of Centres

Columns are the core lateral load resisting elements in the buildings which do not have any other forms of resisting components. The sectional dimensions of the columns are often judge based upon the gravitational loading or a combined effect of gravitational and lateral loading on the structure. As per the early research on irregular buildings, they are highly vulnerable for damage when subjected to lateral forces (seismic/wind) when compared to regular shaped buildings, due to the presence of torsional forces. It has also been proved that these torsional forces are generated due to structural eccentricities of the system. The centres of stiffness and strength are predominantly dependent upon the configuration of the lateral load resisting elements. In this study, the effect of proper configuration of column’s dimensions on torsional parameters of irregular buildings is carried out. Non-linear Time History analysis on Plan irregular building with dual asymmetry is performed using scaled acceleragrams and the torsional parameters such are diaphragm’s rotation, torsional irregularity ratio, angular acceleration of the diaphragm are compared with the basic model.

Nonlinear Behavior of Building with Varying Percentages of Slab Opening

The work describes about irregular plan geometric forms that are more in metro cities. Irregularities are not avoidable in construction of buildings. In present scenario many buildings have irregular configurations both in elevation and plan. Now a day’s openings in the floors are common for many reasons like stair cases, lighting architectural etc. The present study focuses on the behavior of 10 storey reinforced concrete buildings under seismic zone-v, the plan dimensions is taken as 28 m x 28 m. The plan irregularities such as openings in slab with varying percentages is taken in this study. Study is done on various plan configuration buildings and the action of structural diaphragm on its performance during earthquake is studied. Pushover analysis is performed by using ETABS software, for present work five models are studied 1) building without opening in slab 2) plan irregular building with 10% opening in slab 3) plan irregular building with 20% opening in slab 4) plan irregular building with 30% opening in slab 5) plan irregular building with 40% opening in slab. Output from software consisting of Pushover curve and hinge formation results of all five models which are presented. Plan irregularity find better structural system solution such as in 20% opening shows better base shear.

A 3-dimensional perspective for inter-storey drift, ductility and damage distributions in plan-irregular RC buildings considering seismic orientation effect

Current seismic design of buildings is mostly based on applying earthquake excitation along principal (reference) axes of the building plan and response assessment on the same axes. However there is a challenge, whether or not the seismic excitation is applied on the principal axes, critical responses can take place on non-principal directions. The compound of this challenge with inherent response complexity in nonlinear behaviour of plan-irregular buildings leads to critical responses whose estimation is complicated. Current study proposes a new approach to address these challenges by presenting a 3-dimensional perspective for drift, ductility and damage indices. The concept of spatial response distributions is developed wherein vertical and planar response variations can be assessed. 4-, 8- and 12-storey reinforced concrete moment-frame structures with a typical L-shaped plan are employed in multi-direction pushover and nonlinear response history analyses, using 60 record component pairs of near-field and far-field earthquakes. Based on nonlinear regression analysis, several combination rules and amplification factors are derived for the critical responses polarized on non-principal directions at each storey level. A substantial increase (20%-to-60%) in the responses is observed; it depends on seismic orientation scheme, vertical distribution and planar direction of interest, and response definition.

Pushover Analysis of Plan Irregular RC Buildings with Special Columns

Pushover Analysis of Plan Irregular RC Buildings with Special Columns