Storey RC Frame Research Articles

Comparitive study on RCC frames subjected to blast and earthquake loading

The majority of high-rise structures in the northern part of India are designed to be earthquake resistant. Due to an increase in accidental and intentional explosions these structures are exposed to blast pressures so it is necessary to consider the blast load with the same importance as earthquake load. Blast loading and seismic excitations are the most destructive events a structure can experience during its life and hence, need a significant exploration. In the present study the global response of the structure subjected to blast loading is studied. The impact of different assumptions in the application of blast load to the building and loading area of the frames are studied. Then comparison is made between the response of building subjected to blast and earthquake forces. The study was performed on a 10 storey RC frame and dynamic analysis is carried out using ETABS according to IS 875–1987 & IS 1893 (part 1): 2016. The blast pressures that are, reflected blast pressure and over pressure are determined using IS 4991–1968.According to the source of the explosion, the weight of the explosive and the reaction of the safe distance of the building were found. According to the source of the explosion, the weight of the explosive and the reaction of the safe distance of the building were found to study the structural response. Depending upon the source of blast, weight of charge explosive and response of the building safe stand-off distance is found. The results presented lateral storey drifts generated by the explosive load are significantly larger than those of the seismic drifts. The study concludes that it is important to consider the overall response of the building to explosive loads and that response parameters such as lateral drift should be considered in the building evaluation and design process.

Seismic response control of an open-ground story RC frame building using the negative stiffness device

Seismic response control of an open-ground story RC frame building using the negative stiffness device

Analysis and Design of G+12 Storey Reinforced Concrete Building Using ETABS

Abstract: Extended Three Dimensional Analysis of Building Systems is abbreviated as ETABS. The significant objective of this program is to make multi-story structures in a purposeful way. The productive plan and development of quake safe designs is significant everywhere. ETABS was used to analyse and design a multi-story residential structure with the lateral loading effect of an earthquake. IS 1893-part2:2002 and IS 456:2000 were used to design this project. This analysis takes into account harsh earthquake zones, and reactions are evaluated using soil type-II conditions. Important phrases: Etabs programme , Seismic Analysis of G+12 storey RC frame structure.

Evaluation of R-Factor for 5 Storey RC Frame (IMRF) Building

According to IS 1893 part 1 (2016), the philosophy of earthquake resistant structures allows for some damages and inelastic lateral displacement in the structure for energy dissipation during an earthquake. The non-linear behaviour of elements in the structure plays a crucial role in earthquake resistance. There are three detailed classes for distinct seismic zones in different national codes. In India, the draught IS 13920 advocated the usage of IMRF (intermediate moment resisting frame) in zones II and III. The 5 story IMRF is designed and detailed as per IS 1893 (part 1) 2016, IS 13920 (2016), IS 1893 draft, IS 13920 draft, IS 456 (2000). In addition, nonlinear static pushover analysis was performed on IMRF and SMRF RC frame buildings in accordance with FEMA 356. (Displacement Coefficient method) During the analysis, two distinct load patterns (i) parabolic as per IS 1893 (part 1) 2016 (ii) fundamental mode shape are utilised, and the influence of p-delta is also taken into account when evaluating the response reduction factor. The analysed R-factor for studied frame building for fundamental mode shape loading was found to be near to the initial estimated R-factor during the design.

Effect of Aerocon Block, Reinforced Brick Masonry and RCC Diagonal Struct in Two Dimensional Single Bay Two Storey RC Frame under Cyclic Loading

This paper summarizes the analytical investigation of two dimensional single bays two storeys RC frame with Aerocon block, Reinforced brick masonry and Diagonal Strut under lateral cyclic loading. The paper analytically determines the behaviour of the RC frame with Aerocon block masonry, Reinforced brick masonry and Diagonal Strut under equivalent static lateral cyclic loading conditions. The preliminary test such as compression test on prisms for the infill panels were done experimentally and the values were incorporated in the analytical modeling. Analytical works have been conducted using ANSYS software. The frames were subjected to lateral cyclic loading and the behaviors such as Load carrying capacity of the frames, Load-deflection behaviour, Stiffness degradation, have been determine. The results of all the three frames were compared.

Non-Linear Performance of Strong Column Weak Beam RC Frame Building

Buildings are designed in different methods for resisting the lateral loads, in which strong column weak beam concept is one of the methods of designing, this method is used to avoiding the global failure of the structure In this work 3bay 5 story RC frame building is consider for the analysis, the structures are design strong column weak beam with the help of static non-linear pushover analysis of RC frame building with increasing the percentage of column sizes 20%, 40%, 60%, 80% and 100%. By varying with percentage of columns resistances of structure is increased. The parameters base shear, story displacement, and hinge formations in the structure is obtained from this analysis. The base shear and displacement are increased by increasing the column sizes, these parameters are discussed the results in detail. Comparing the all six model results the base shear in increased by 266.64% when the column size is increased by 100%. From this analysis we can reduce the failure in the structure during the earthquake. Formation of plastic hinges in column changes to beam by increasing the column size, so increase the capacity of structure. The building is analyzed by using SAP2000.

Effect of Soil Structure Interaction on Multi-Storeyed Building with Raft Foundation

This paper addresses the behaviour of multi storey structure considering soil structure interaction i.e. interaction between substructure of the building and soil. For this purpose a sample of 5 storey RC frames is analysed in conventional method with incremental static analysis for various load combinations and determines the parameters displacement, shear force and bending moment. Then a same 5 storey RC frame is analysed in numerical analysis using Finite Element Method (FEM) with raft foundation by assigning the soil properties to substructure and determine the parameters displacement, shear force and bending moment. According to the analysis results the parameters displacements, shear force and bending moment varies from conventional analysis to numerical analysis. Displacements of the structure increases, shear forces of the structure decreases and bending moment of the structure decreases at some points and increases at some points from conventional method of analysis to numerical method of analysis.

Behaviour of Reinforced Concrete Frames with Central Opening Masonry Infill under Lateral Reversed Cyclic Loading.

This paper will describe the seismic behaviour of masonry infilled RC frame with a central opening structure under reversed cyclic lateral loading. To achieve the purpose of this study, four 1/4-scale single story and single bay RC frame specimens were tested, i.e. one bare frame, one clay brick masonry infilled RC frame without opening and two clay brick masonry infills with a central opening in infills. The ratios of opening size to panel area were 25% and 40%. Through reversed cyclic lateral loading tests, the seismic performance of RC frames with a central opening brick masonry infills was investigated. As the results, significant distinctions of failure mechanism, lateral strength, stiffness, and ductility were observed between these specimens. In the case of infills with a central opening, the cracks sprouted and developed at the corners of the opening. Although the presence of the opening in infill reduces the lateral strength and stiffness overall structure, the brick infilled frames with a central opening of 25% and 40% of panel area show better seismic performance as compared to the bare frame.

Seismic performance of reinforced concrete frames retrofitted using external superelastic shape memory alloy bars

Pre-1970s designed and built reinforced concrete frame structures are considered unsafe when subjected to seismic loads. Insufficient anchorage of the beam reinforcement in the beam-column joints of these structures is considered a main deficiency. Newly built frame structures are seismically designed for safety, where high inelastic deformations can occur under moderate to strong earthquakes. Minimizing these inelastic deformations makes the structure repairable. One way to minimize these residual deformations is by using smart materials such as superelastic shape memory alloys (SMAs). In this paper, the seismic performance of RC frames retrofitted using external superelastic SMA bars is investigated and compared to the behaviour of a regular steel RC frame structure. Nonlinear time history analysis is performed for a six storey RC frame structure located in a high seismic region. After performing the analysis, two retrofitted frames are assumed and analyzed at the load intensities causing failure of the steel RC frame. The performance of the retrofitted frames is compared to the steel RC frame in terms of the damage level, the Maximum Inter-Storey Drift (MID) ratio, Maximum Residual Inter-Storey Drift (MRID), Maximum Roof Drift Ratio (MRDR), Residual Roof Drift Ratio (RRDR), and the earthquake intensity at collapse. Analysis results show improved seismic performance for the two retrofitted frames as compared to the original steel RC frame. This improvement was represented by lower level of damage at the same earthquake intensity; small reduction (10–15%) in the MID and MRDR values; significant reduction (50–70%) in the MRID and RRDR; and increased seismic capacity.

Effect of URM infills on inelastic floor response of RC frame buildings

The effect of unreinforced masonry infills on the floor acceleration response of inelastically responding mid-rise RC frame buildings is studied using incremental dynamic analyses. Two structural building configurations, uniformly infilled, and with open ground storey are analyzed by using the FEMA P695 far-field ground-motion suite. It is observed that the effect of structural nonlinearity is much more pronounced in case of infilled RC frame buildings than bare RC frame buildings. Sequential failure of infills results in a significant elongation of period of vibration resulting in the shifting of peaks in floor spectrum towards longer periods. Modified floor spectral amplification functions are presented for both uniformly infilled and open ground storey RC frame buildings. The proposed spectral amplification functions are validated using nonlinear analysis of typical buildings for recorded as well as spectrum-compatible ground-motions and can be used to estimate the floor response spectra directly from the code-based or site-specific design spectra.

Seismic behavior of transfer girder in multi-story building

Urbanization had led to many housing problems in India. Scarcity of land is one such biggest problem in India. This issue is one of the most pivotal issues that need to be provided with a swift and efficient solution if we want to grow as a nation whilst achieving the goals we are aiming at. Hence, there is a rise in many Multi storey and Highrise structure. Rise in car park and open column free space for auditoriums. The study focuses on the study of seismic assessment of the Multi-storey structure with transfer girder. The use of transfer girders in a building will help to a greater extent to minimize the issue regarding the lack of space for car parking. A building prototype model with transfer girder at different level was analyzed using elastic linear response spectrum. Different results such as Base Shear, Time Period, Interstorey Drift and Displacement had been analysed in different model and optimum modeling of Multi storey RC Frame building with transfer girder system using SAP 2000 and also comparison on performance of Multi storey building by placing the transfer girder in different level has been carried out.

Tuning of mass dampers for preventing brittle fracture by employing teaching learning based optimization

AbstractIn design of reinforced concrete structures, a ductile design is needed, because the brittle fracture is sudden. Also, the energy absorbed by the structure is effective for ductile structures during earthquake excitations. In design regulations, especially for vertical supporters such as columns, the shear force and axial force capacity is limited, although the strength of the members is not at the limits. For that reason, the shear forces of structures excited by earthquakes can be reduced by adding a tuned mass damper (TMD), but TMD must be optimized and it must not be heavy. If the mass of the TMD is not optimized, the ductile behaviour constraint about the axial force capacity cannot be provided. The compressive strength of the concrete is a measure for the effective application of a TMD to a reinforced concrete structure. Since the mass is limited by the design constraint, the other design variables of TMD such as period and damping ratio are optimized. Using the formulas for frequency and damping ratio related to a preselected mass may not be sufficient and a precise optimum solution for preventing brittle fracture. Metaheuristic methods can be used by using a specific limit. In this study, Teaching Learning Based Optimization (TLBO) is employed to find optimum TMD parameters. Several earthquake excitations were used in the optimization process. A three storey RC frame structures with different compressive strength of concrete is investigated. Three stopping criteria have been used in the proposed methodology. The first criterion is the reduction of the maxi‐mum shear force value for the most critical excitation to the ductile behaviour limit. The second criterion is the reduction of the ratio of maximum first storey displacements of structure with and without TMD. This value is reduced under a user defined value, but the user defined value can be entered as zero. This value can be iteratively increased for minimization. The last criterion is the reduction of the acceleration transfer function of the structure. The proposed method is feasible on finding optimum TMD ensuring ductility conditions. (© 2016 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Overstrength factors for SDOF and MDOF systems with soil structure interaction

This paper addresses the concept of lateral overstrength; the ratio of actual lateral strength to design base shear force, for both SDOF and MDOF systems considering soil structure interaction. Overstrength factors are obtained with inelastic time history analysis for SDOF systems for period range of 0.1-3.0 s, five different aspect ratios (h/r=1, 2, 3, 4, 5) and five levels of ductility (<TEX>${\mu}$</TEX>=2, 3, 4, 5, 6) considering soil structure interaction. Structural overstrength for MDOF systems are obtained with inelastic time history collapse analysis for sample 1, 3, 6, 9, 12 and 15 storey RC frame systems. In analyses, 64 ground motions recorded on different site conditions such as rock, stiff soil, soft soil and very soft soil are used. Also lateral overstrength ratios considering soil structure interaction are compared with those calculated for fixed-base cases.

Elemental damping formulation: an alternative modelling of inherent damping in nonlinear dynamic analysis

To date, nonlinear dynamic analysis for seismic engineering predominantly employs the classical Rayleigh damping model and its variations. Though earlier studies have identified issues with the use of this model in nonlinear seismic analysis, it still remains the popular choice for engineers as well as for software providers. In this paper a new approach to modelling damping is initiated by formulating the damping matrix at an elemental level. To this regard, two new elemental level discrete damping models adapted from their global counterparts are proposed for its application in nonlinear dynamic analysis. Implementation schemes for these newly proposed models using Newmark incremental method and revised Newmark total equilibrium method is outlined. The performance of these proposed models, compared to existing models, is illustrated by conducting nonlinear dynamic analyses on a four story RC frame designed to Eurocodes. The incremental dynamic analysis study presented in the paper illustrates the fact that both the proposed models seem to produce more reliable results from an engineering perspective in comparison to the global models. It is also shown that the proposed elemental damping models lead to smaller and more realistic damping moments in the plastic hinges. Furthermore, these models could be easily included in existing software frameworks without adding noticeably to the computational effort. The computation time required for these models is approximately equivalent to the one required when using the tangent Rayleigh damping matrix with constant coefficients.

Seismic Evaluation and Preliminary Design of Regular Setback Masonry Infilled Open Ground Storey RC Frame

Current seismic code presents certain stringent factors for defining frame as regular and irregular. Thereby these stringent factors only decide the type of analysis (i.e. equivalent static analysis or dynamic analysis) to be done. On the contrary, development of new simplified methods such as pushover analysis can give lateral load capacity of any structure (e.g. regular or irregular frame etc.) easily. Design by iterative procedure with the help of pushover analysis for serviceability requirement (i.e. inter storey drift limitation) provided by present seismic code, can provide an alternative to present practicing procedure. Present paper deals with regular setback frame in combination with vulnerable layout of masonry infill walls over the frame elevation (i.e. probable case of “Vertical Stiffness Irregularities”). Nonlinear time history analysis and Capacity Spectrum Method have been implemented to investigate the seismic performance of these frames. Finally, recently developed preliminary design procedure satisfying the serviceability criterion of inter storey drift limitation has been employed for the preliminary design of these frames.

SEISMIC PERFORMANCE OF R C BUILDINGS ON SLOPING GROUNDS WITH DIFFERENT TYPES OF BRACING SYSTEMS

Structure are highly susceptible to serve damages in earthquake scenario, so choosing an appropriate lateral force resisting bracing systems will have a significant effect on performance of the structure. So this present study is aimed at evaluating and comparing various types of eccentric steel bracings for 12 storey RC frame building resisting on sloping ground configurations. For this 5 types of bracing systems like X-Bracing, Diagonal bracing, K- bracing, V-bracing and inverted V bracing are considered on the outer periphery of the buildings with step back and set back – step back type configurations are modeled and analyzed. The models are compared for different aspects within the structure, such as the maximum storey displacement, base shear, storey drift and storey shear, the structure is analyzed for seismic zone V and medium soil condition as per IS 1893:2002 using ETABS software. Results conclude that on sloping ground due to irregularity on ground surface, the structures are more vulnerable to earthquakes. Hence use of eccentric steel bracing is an effective and economical way to resist earthquake forces, Inverted V type bracing performs well compared to other bracing types. By using inverted V type bracing in step back buildings types maximum storey displacement of 70% and storey drift of 66% are obtained. Similarly for setback – step back configuration maximum storey displacement of 74% and storey drift of 70% are obtained respectively.

Nonlinear cyclic performance evaluation of soft storey RC frame buildings based on different characteristics of reinforcement

The purpose of this study is to update the non-linear modeling of soft storey RC frame building for performance based design. The qualitative and quantitative assessment of different strength and ductility parameters of tested building components including the different types of reinforcing steel have been presented. The cyclic performance of tested G+2 soft storey RC frame building of ¼ scale is evaluated and the components test results are applied successfully for performance evaluation of prototype soft storey RC frame buildings under different modes of failure. It indicates that the non-linear characteristics of reinforcement used in different components of building frame have significant influence on the global failure pattern particularly assuring a flexure mode of failure.

Plastic Hinge Relocation in Reinforced Concrete Frames as a Method of Improving Post-earthquake Fire Resistance

Post-earthquake fire (PEF) presents a risky situation to buildings that have been partially damaged in a prior earthquake, particularly in urban areas. As most standards ignore the possibility of fire after earthquake, buildings are not adequately designed for that possibility and thus PEF is a high-risk load needed to be scrutinized further, codified and become part of a routine design. An investigation based on sequential analysis inspired by FEMA356 is performed here on a two story RC frame, at the Life Safety performance level and designed to the ACI 318-08 code, after it has been subjected to a spectral PGA of 0.35g. The results show that structures previously damaged by the earthquake and exposed to PEF are considerably more vulnerable than the structures, which have not been damaged previously. A method of strengthening using Carbon Fiber Reinforced Polymer (CFRP) wraps is introduced in order to relocate plastic hinges away from the column faces towards the beams. This method increases the structural load carrying capacity, and thus reduces the potential damage from a potential earthquake, improving the fire resistance. The results show a considerable improvement in the PEF resistance of the frame.

Design Optimization of Reinforced Concrete Frames

In this paper, a design optimization for the reinforced concrete plane frame structure has been done in order to minimize the cost of the concrete and steel for beams and columns by adopting the Artificial Neural Network (ANN) computational model trough the NeuroShell-2 software program. The design procedure conforms to the ACI-318-08 Code. The variables used for design optimization are the width, depth and the area of reinforced steel, including longitudinal reinforcement and shear reinforcement. A three-bay two-story RC frame is modeled with selecting different span length and different load cases. Acceptable design results are obtained from more than 50 examples which are subjected to all the constraints of the ACI Code, using different cross-section sizes and these results are used to train the NeuroShell-2 program. The results obtained demonstrate the efficiency of the ANN procedure for the multi story RC frame design.

A Simplified Numerical Method for Blast Induced Structural Response Analysis

Efficiently and accurately predicting structural dynamic response and damage to external blast loading is a big challenge to both structural engineers and researchers. The conventional numerical treatment to this problem is proved being able to give reliable predictions, however at the cost of enormous computational time and resource. Simplified SDOF approach is popularly used in design as it is straightforward to use and also gives good structural response predictions if the response is governed by a global response mode (shear or bending) and the accurate dynamic deflection curve is available, but it cannot predict the detailed local structural damage. In this study, a new numerical approach that combines the recently proposed two-step method and the static condensation method is proposed to analyze structure response and collapse to blast loads. The two-step method divides the structural response into two phases, i.e. forced vibration phase (blast loading duration) and free vibration phase. Single- Degree-of-Freedom system approach is adopted to solve the structural element responses at the end of the forced vibration phase, and the structural free vibration simulation is carried out using the hydro-code LS-DYNA to calculate the detailed structural response and damage. The static condensation technique is utilized to condense structural components that are relatively away from the explosion center to further reduce the computational effort. To demonstrate the proposed method, the structural responses of a three story RC frame to blast loads are calculated by four approaches, i.e. the traditional detailed FE simulation, the two-step method, the model condensation method, and the new combined two-step and dynamic condensation method. Through the results comparison, the efficiency and accuracy of the proposed combined approach are demonstrated.