Response Reduction Factor Research Articles

Modification of response reduction factors of overhead water tanks based on ductility factor

In the earthquake-resistant design of overhead tanks, this research dealt with the determination of the response reduction factor applicable to overhead water tanks performing beyond the elastic limit. Eight existing water tanks were selected for the investigation and 127 ground accelerations due to 10 Indian earthquakes were selected. The magnitude of the earthquakes selected ranges from 4.5 to 7.2. Initially, 10.16 million nonlinear dynamic data of response reduction factor had been produced using Newmark’s β method by varying parameters. From the results obtained, multi-linear regression analysis was made to arrive at the empirical formula relating the parameters and it was found that ductility factor was the most significant factor among others such as damping ratio, pre-post stiffness ratio, natural period, and soil types, in influencing response reduction factor. Eventually, It is concluded that the values of the response reduction factor to be adopted in the dynamic analysis of Overhead water tanks should be based on the desired value of the ductility factor.

Response Reduction Factor for Structures with Significant Irregularities on Different Soil Stratum

The ability of a structure to dissipate energy through inelastic behavior is reflected in the response reduction factor (R), which is influenced by redundancy, ductility, and overstrength. Accurate determination of R is crucial for seismic design. This study focuses on determining the response factor for reinforced concrete (RC) structures with various irregularities. Non-linear static pushover analysis using SAP2000 was employed for numerical simulations to assess the impact of soil-structure interaction (SSI). The analysis included elevational and in-plan irregularities, revealing that buildings with irregular vertical geometries have lower inelastic seismic capacities compared to regular buildings. Consequently, R should be reduced by 15–40% from the ECP 2020 standard before the design phase for such structures. Irregularity was found to have a significant impact on weak soil conditions (C), leading to a reduction in R of 20.3% and 13.1% for fixed and isolated supports, respectively, on loose soil. Additionally, stiffer base soils were associated with higher R values for the same structure. Doi: 10.28991/CEJ-2024-010-03-07 Full Text: PDF

Response Reduction Factor for Structures Irregularities in Plan and Elevation Taking into Account Soil-Structure Interaction

The structure's ability to release energy through inelastic behaviour is reflected in the response reduction factor (R). It results from a combination of redundancy, ductility, and over strength. Thus, determining R with accurate values plays a critical function in the process of seismic design. This study aims to determine the response factor of structures of reinforced concrete (RC). With different structural irregularities, additionally, determine the impact of the interaction between soil and structure (SSI) using non-linear static pushover analysis was adopted in numerical simulation by using SAP2000. The selected irregularities included elevational and in-plan changes It was determined that, in comparison to regular buildings, buildings with irregular vertical geometries had poorer inelastic seismic capacities. Therefore, R is less than that which is stated in the ECP 2020, so it ought to be reduced by 15–40% before the design stage. The outcomes demonstrated that It isn't concluded that irregularity has a considerable effect on weak soil (C). The reduction in R, considering (SSI), reached 20.3% and 13.1% for fixed and isolated supports, respectively, in case of loose soil. Moreover, it became obvious that for the same structure the stiffer the base soil the greater the R's value.

Performance assessment of RC frame buildings with open ground storey

Buildings with open ground storey (OGS) evidenced catastrophic failure in past earthquakes. Building code provisions usually: (i) avoid designing such buildings (e.g., ASCE 7–16), (ii) provide structural walls up to 2% plan density (e.g., IS 1893–1) and (iii) design by amplifying the demand at ground storey using modification factor (e.g., Eurocode 8) or reducing the response reduction factor using an irregularity factor (e.g., NTE-E030). Hence applicability of these provisions is checked with a set of 2D RC frame buildings; it includes (i) a simple OGS building (OGS1), (ii) OGS building with structural wall at ground storey, IS 1893–1 (OGS2), (iii) OGS buildings designed as per NTE-E030 (OGS3) and Eurocode 8 (OGS4). Their inelastic behaviour is obtained using nonlinear static and dynamic analysis, including infill walls as an equivalent strut. OGS2 suffered the least (damage in struts), and OGS3 sustained more damage (in struts, beams and columns). It is mandatory to provide structural walls at the ground storey rather than designing for amplified force demands. A parametric study is conducted (for OGS using IS 1893–1): (a) by varying the height of the building, and (b) including structural walls in 1, 3 and 5 bays. Increasing height or providing structural walls in more bays increases damage in struts and no damage in other elements. The response reduction factor (R) for OGS3 is more than OGS1, OGS2 and OGS4, as it shows more damage; it is necessary to avoid damage in OGS buildings. Also, the R-value reduces with building height and increases with structural walls in more bays; thus, a single R-value is not applicable to all buildings.

Determination of the seismic vulnerability of infilled RC buildings according to the Quadrants assessment method

The earthquake vulnerability of the buildings has become more important after significant structural damages due to seismic events. The Quadrants assessment method is one of the effective procedures for the determination of the earthquake performance of the buildings. In this study, the impact of the infill walls on the structural vulnerability of reinforced concrete (RC) buildings was investigated using this method. Five different building models are designed such as bare RC frame, RC frame with strut infill as per field test (open ground story), RC frame with strut infill as per ASCE-41-06 (open ground story), full RC frame with strut infill as per field test (fully infilled), and full RC frame with strut infill as per ASCE-41-06 (fully infilled). All structural analyses were performed using an adaptive pushover analysis in the SeismoStruct software. The infills in the studied RC buildings were modeled as an equivalent strut as per field test or ASCE-41-06 code. The influence of different building models on the performance point, overstrength factor, response reduction factor, and ductility reduction factor was evaluated. The performance point is calculated as per the ASCE-41-06 code which is based on the “displacement coefficient method” and the application of the performance point is used to decide on the intervention/retrofit of RC structures through the “Quadrants assessment method”. In this study, the results depict that the strut width of the infill as per ASCE-41-06 is underestimated as compared to field test. Thus, the impact of the strut width is quantified on the seismic design parameters. It is concluded that there is a need for intervention/retrofit of the bare frame and open ground story RC infilled frame based on the “Quadrants assessment method” due to the absence of infills and the calculated values of the response reduction factor (R) obtained for the infilled RC building models are higher than the bare frame structure due to presence of infills.

Analytical investigations of seismic performance of different joint details for composite RCS frames

AbstractComposite RCS frames, comprising of Reinforced Concrete (RC) column and Steel (S) beam are gaining popularity as an attractive alternative to traditional steel moment frames for mid to high‐rise buildings as well as conventional RC construction for low‐rise buildings. The prime concerns with RCS frames are constructability and load transfer at beam‐column connections. Over the last 30 years, several joint details, viz. face bearing plates, erection steel columns, vertical joint reinforcement, and steel band plates have been proposed for RCS frames. The moment‐rotation behavior of these joints was established through quasi‐cyclic experimental programme. The moment‐rotation characteristics of RC column‐S steel beam joint significantly affect seismic performance of the overall frame. The objective of this paper is to evaluate the seismic performance of low and mid‐rise RCS moment resisting frames with different connection details, available in published literature. The nonlinear analyses of differently jointed RCS moment resisting frames is carried out and performance assessed in terms of collapse capacity and the available response reduction factor, Ravl. Seismic collapse risk of RCS frames is estimated to understand performance under uncertain ground motion.

Response Reduction Factor of Steel – RC Hybrid Structure

Civil Engineering structures should have sufficient strength and stiffness to control deflection and prevent possible collapse of the structure during a seismic event. The design force levels currently specified by most seismic codes are calculated by dividing the base shear for elastic response by the response modification factor (R). Seismic codes consider a reduction factor in designing the loads in order to cause the structure to enter into the nonlinear behavior region and then use the advantages of its energy dissipation. The seismic response of such mixed structure having different structural system at different floor levels is entirely different to the response of the pure steel or RC structure. During an earthquake excitation, upper steel stories behave as a structure built upon a fixed base RC structure. So, the response of such structure needs to be studied and the computation of appropriate response reduction factor is required in order to minimize the risk.

Vibration response analysis of footbridge based on pedestrian perception

This article aims to study the influence of random crowd loading on the perceived vibration response of pedestrians. Firstly, a vertical vibration response analysis method considering pedestrian perception was established based on the random crowd walking model. Secondly, change rules of maximum vibration response of pedestrians, occurrence time and position interval under different random walk models were compared and analyzed. Finally, the vibration response reduction factor was defined by studying the correlation between the maximum vibration response of pedestrians and the peak acceleration of the structure, and the approximate calculation method of the maximum vibration response of pedestrians was proposed. The results show that the maximum acceleration perceived by pedestrians obeys the normal distribution under the four crowd walking models, the response distribution of ordered arrangement model (OAM) is larger than that of the other three models; The location and occurrence time of the maximum response depend on the distribution of pedestrian locations on the footbridge, and there is no significant change with the increase of population density. In addition, the distribution of OAM and stochastic arrival model (SAM) are consistent, which is concentrated in the middle of the total time-history. In contrast, the distribution of stochastic distribution model (SDM) and dynamic equilibrium model (DEM) are relatively uniform. The maximum error between the calculated acceleration maximum value and the actual acceleration value felt by the pedestrian is less than 5%. These results can provide reference for quantitative evaluation of pedestrian-induced vibration comfort.

Selection of Response Reduction Factor Considering Resilience Aspect

The selection of an adequate response reduction factor (R) in the seismic design of a reinforced concrete building is critical to the building’s seismic response. To construct a robust structure, the R factor should be chosen based on the building’s resilience performance. Since no background was provided for the selection of R factors, the study focuses on the right selection of R factors in relation to the building’s functionality, performance level, and resilience. In this study, a high-rise building with multiple R factors (R = 3, 4, 5, and 6) is developed. Five potential recovery paths (RP-1 to RP-5) that matched the realistic scenario were used to estimate the building’s functionality. The building was subjected to uni and bi-directional loadings, and two design levels, Design Basic Earthquake (DBE) and Maximum Considered Earthquake were used to monitor the building’s response. According to the findings, a decrease in the lateral design force with the highest R results in a high ductility requirement and a substantial loss of resilience. The maximum R factor can be recommended under uni-directional loading up to 6, in which the building’s resilience is almost 50%, whereas under bi-directional loading and taking the recommended R factor decreased from 6 to 4.

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 Comparative Study of Overhead Tank Subjected to Seismic Forces in Different Zones

Overhead tank are generally classified as Ordinary Moment Resisting Frame (OMRF) and Special Moment Resisting Frame (SMRF) supported response reduction factor. Generally, the Overhead tank consists of structural members like slabs, beams, columns, and footings, where the subjected loads are transferred between the structural members and eventually transferred to the Sub-grade of the soil. The behavior of the Overhead tank is different for various sorts of loadings (Dead, Live, Wind, and Seismic) within the analysis and of overhead tank usefully Indian standards codes suggest various loads combinations supported probability of Occurrence. There are around 52 load combinations and IS codes suggest the lateral load (wind and seismic) acts independently but the load governing the planning of structural members is to be acknowledged. and therefore the present study to research the consequences of wind and seismic forces on Overhead tank structures of heights (15m) are considered in seismic zones II, III, IV, V where length and width of the structures are kept constant. An earthquake load is calculated as per IS and wind pressure calculated as per IS 875-1987. The analysis is done the use of STAAD.pro software.

Seismic hazard analysis of Silchar city located in North East India

North East India is a highly seismically active zone of India due to the collision tectonics between the Indian and the Eurasian plate in the north and subduction tectonics along the Indo-Myanmar range (IMR) in the east. It is utmost important to investigate the seismicity of this region along with uniform hazard spectra (UHS). In this paper, seismic hazard study has been performed at the Silchar district headquarters of Assam state, located in North East India. The earthquake data have been collected from various agencies from 1762 to 2020 and the fault data has been collected from seismotectonic atlas (SEISAT). Earthquake and fault data are superimposed on the Northeast India map using MapInfo software. The fault zone is defined based upon the earthquake’s density near the fault. Seismicity parameters and maximum magnitude have been estimated using Gutenberg-Richter (G-R) relationship. The best-fitted ground motion equation is considered. The outcome is represented in terms of controlling source, seismic hazard curve and UHS for Silchar city with varying ground motions. Finally, the results are presented as PGA based upon DSHA and PSHA methods. The effect of Importance Factor (I) and Response reduction factor (R) have been investigated by comparing UHS with IS: 1893-2016 code response spectra.

Accounting for Resilience in the Selection of R Factors for a RC Unsymmetrical Building

Several design codes consider the non-linear response of a building by using one of the most important seismic parameters, called the response reduction factor (R). The lack of a detailed description of the R factor selection creates the need for a deeper study. This paper emphasises a methodology for the selection of a proper R factor based on resilience aspects. Unsymmetrical/irregular buildings have become the most common in recent times due to aesthetic purposes. However, because of the complexity due to the torsional effect, the selection of the R factor is even more difficult for this type of building. Therefore, a high-rise G+10-storey L-shaped building is herein considered. The building has re-entrant corners based on the structural/plan arrangement. Different R factors were used in the building design, considering buildings subjected to both unidirectional and bidirectional seismic loading scenarios. The building response with respect to various R factors (R equal to 3, 4, 5 and 6) in terms of its performance level, functionality, damage ratio and resilience was assessed at two design levels, i.e., design basic earthquake (DBE) and maximum considered earthquake (MCE). The study concludes that, considering the above criteria along with the resilience aspect, a maximum R factor up to 4 can be recommended for unidirectional loading, whereas for bidirectional loading, the maximum recommended R factor is 3.

Comparative analysis and design of structure in accordance to Indian and American standards

Comparing and analyzing the seismic loads applied to Special Moment Resistant Frame (SMRF) structures is the study's main objective using Indian (IS: 456 and IS: 1893) and American Standard Codes (ASCE 7–10 and ACI 318). Additionally, both codes load factors and load combinations were examined. For this purpose, The SMRF building is analyzed according to both codes. In this study, an SMRF structure designed utilizing Indian (IS: 456–2000, IS: 1893–2016) and American main codes iscompared (ACI 318 2014 and ASCE 7–10 2014). This study compares seismic design regulations for reinforced concrete buildings in India (IS-1893–2016) and the United States (ASCE 7–10) based on the types of allowable analysis methods, zoning systems,fundamental vibration periods of the structures, important factors,response reduction factor, design response spectrum, and minimum design lateral forces. In order to analyze the seismic performance of building models, dynamic analysis was used to understand earthquake (EQ) considerations. Base shear coefficient (BSC), which displays EQ models, is used to compare seismic performance when the damping ratio is set at 0.05.

Seismic Capacity Estimation for Composite Multi-storeyed RC buildings

Seismic hazard happens to be one of the most devastative natural hazards to be faced by mankind. In view of urbanization and knowledge gained from past natural hazards, several urban cities have seen a transformation in building their habitats. These range from regular, irregular multistoried Reinforced Concrete (RC) buildings to several composite multi storeyed RC buildings due to certain inherent functional benefits (viz., ventilation, parking space, ease of construction etc.,). The existing seismic code regulations provided by BIS (Bureau of Indian Standards) do not specify any approach to arrive at appropriate design seismic forces and capacity for composite multi storeyed buildings. Therefore, it is imminent to assess the structural behaviour of these multistoried composite RC buildings under earthquake forces at the site location to provide a safe and functional configuration. Hence an attempt has been made in this study to analytically compare regular and composite RC building models having similar Plan and Height. The multistoried RC building configurations considered in this study comprises of regular RC building as well as RC building frame coupled with steel joists at certain locations to represent a composite structural system. These models are further analyzed to arrive at inherent nonlinear seismic capacity, ductility and design seismic forces necessary to be considered during design of RC building structure. Hence, a typical hypothetical G+5 regular and composite multistoried buildings were modelled and analysed using the nonlinear static (pushover analysis) approach. The outcomes of these analyses clearly portrays the variation in dynamic characteristics of the building frames represented in terms of its time period, inelastic capacity and response reduction factor (R). Moreover, the present study emphasizes to analytically evaluate the design seismic forces necessary for earthquake resistant design of composite buildings in any urban environment albeit the changes in structural configurations.

Comparative study of seismic analysis and design of residential structure using Indian and British standards

Earthquake is a natural and unpredictable disaster that damages life and the economy drastically. In this study, seismic analysis and design of a (G + 3) residential structure were performed through ETABS. The whole analysis was performed for different parameters such as story-drift, displacement shear force, and base shear were studied through Indian standard (IS 1893) and British standard (Eurocode 8). The findings of this study revealed that the value of base shear calculated through Eurocode 8 is higher than the IS 1893 due to the lesser value of the response reduction factor in Eurocode 8. However, the Y-direction base shear is greater than the X-direction. Furthermore, a pattern is seen that as the number of storeys rises, the displacement difference between the standards also rises, leading to the conclusion that the Indian code offers greater displacement capacity for seismic loading than the Euro code without compromising strength and stiffness.

Role of resilience in selection of R factors for an RC building

In the seismic design of a reinforced concrete building, selecting appropriate response reduction factor (R) is vital for the building’s seismic response. Indian Standard (IS) 1893-2016 provides R values of 3 and 5 for ordinary moment resisting frames and special moment resisting frames, respectively. As R factors are used to incorporate the building’s non-linearity, R factor selection should be based on the building’s performance in terms of resilience. Since IS does not provide any clause on the background for selecting R factors for the design aspects, the study emphasizes the appropriate selection of R factors with respect to a building’s functionality, performance level, and resilience. In this study, a high-rise building was designed with various R factors (R = 3, 4, 5, and 6). To estimate the building’s functionality, five different recovery paths (RP-1 to RP-5), which match the real scenario, were used. The response of the building in each case was observed at two design levels, Design Basic Earthquake (DBE) level and MCE level. Variations in ductility demand, performance level, and resilience for each building case at each design level were observed. The R factor was used to obtain lateral design force at the DBE level by reducing the actual base shear placed on the structure. The reduction in the lateral design force with maximum R yielded high ductility demand and high loss of resilience. The result shows that the considered building can be designed with a maximum R of 6 since its resilience is almost 50%; hence, recovery is possible at a high cost. The performance level of the building at R = 6 lies at CP-C for the MCE design level. Considering the building’s resilience and performance level aspects, the maximum R factor was found to be 6. This helps the stakeholder and designer in the selection of R, based on the requirements of building functionality, performance level, and resilience.

Estimation of response reduction factor for Indian standard code designed reinforced concrete frames considering nonlinear soil-structure interaction effects

To incorporate the advantages of inelastic behaviour in design of civil engineering structures under seismic excitations, contemporary seismic design codes adopt a factor, termed as response reduction (or modification) factor ( R ). This factor is considered to calculate the seismic demand of a structure by estimating the inelastic base shear from its linear counterpart. This study first evaluates the adequacy of R values provided in Indian seismic codes by performing numerical studies on different reinforced concrete (RC) frame buildings, which are designed following the provisions of contemporary Indian seismic codes. In particular, to assess the values of R for multi-storey RC frames, the present work utilises rigorous incremental dynamic analysis (IDA). Next, in order to understand the influence of flexible base conditions on R values, elastic and inelastic soil-structure interactions (SSI) are incorporated in the analysis. In flexible base condition, Type II (medium) and Type III (soft) soil conditions (as per Indian seismic code) are considered to characterise the base soil and for designing the isolated footings of the frame structures considered in this study. It has been observed from this study that for both fixed and flexible base conditions, the code specified R value may not be conservative in some cases.

Solution to the problem of bridge structure damage identification by a response surface method and an imperialist competitive algorithm

To increase the efficiency of structural damage identification (SDI) methods and timeously and accurately detect initial structural damage, this research develops an SDI method based on a response surface method (RSM) and an imperialist competitive algorithm (ICA). At first, a Latin hypercube design method is used for experimental design and selection of sample points based on RSM. Then, a high-order response surface surrogate model for the target frequency response and stiffness reduction factor is established. Finally, analysis of variance is performed to assess the overall goodness-of-fit and prediction accuracy of the established model. Then the results obtained are combined with structural dynamic response data to construct objective functions; furthermore, the optimal solution of parameter vector in the objective function is solved based on the ICA. Then damage positioning and quantification can be achieved according to location and degree of change in each parameter; finally, the RSM-ICA-based SDI method proposed is applied to damage identification of high-dimensional damaged simply-supported beam models. To verify the effectiveness of the proposed method, the damage identification results are compared with the results obtained from traditional optimization algorithms. The results indicate that: average errors in the structural stiffness parameters and natural frequency that are identified by the proposed method are 6.104% and 0.134% respectively. The RSM-ICA-based SDI method can more accurately identify the location and degree of damages with more significantly increased identification efficiency and better precision compared to traditional algorithms. This approach provides a novel means of solving SDI problems.

“Analysis of Seismic Behaviours of RC Frame Structure With Bracing System and Without Bracing System”

Abstract: This work time history analysis is carried out for G+23 storey steel frame building with different pattern of bracing system. The member property of beams 300mm X 400mm and columns 300mm X 500mm and ISLB250 sections are used to compare for same patterns of beam, column and bracings. A software package ETABS SOFTWARE is using for the analysis of steel buildings and different parameters are compared. The property of the section is used as IS 456:2016 and per IS 800:2007 which is analysis for various types of bracings like X, V, inverted V, Eccen Forward, Eccen Back and without bracing and Performance of each frame is carried out and studied the comparatively through Response Spectrum Method as per IS:1893:2016. In this study model a G+23 with Square Shape building Plan 52m X 52m, height of each floor is 3.2m and Structure in Etabs software by Response Spectrum Method and Analysis the Earthquake analysis of the Structure in seismic zones III with soil Medium conditions. Parameter Using:Type of Building: RC buildings with and without Steel Bracing System Number of Floors: G+23 (Square Shape Building)Section Property: Beam size 300X400mm, Column size 300X500mm, and ISLB250 sections. Seismic Zone- III, Soil Site factor 2 for Medium Soil, Damping = 5% (as per table-3 clause 6.4.2), Zone factor for zone III, Z=0.16), Importance Factor I=1.5 (Important structure as per Table-6), Response Reduction Factor R=5 for Special steel moment resisting frame Table-7), Sa/g= Average acceleration coefficient (depend on Natural fundamental period)Grade of concrete is considered M25, Grade of Rebar is considered Fe-415, Grade of Steel –Fe-345,Dead Load for Wall = (3.2-0.4) X 0.23X20= 12.88 KN/m