Effect of Building Configuration on Overstrength Factor and Ductility Factor

It is important for the structure to be economical and still have a high level of life safety. The lateral force sustained by the structures during a large earthquake would be several times larger than the lateral force for which the structures are designed. This is opposite to the fact that design loads such as gravity in codes are usually higher than the actual anticipated load. It is based on the probability that the occurrence of large earthquakes is quite rare and the capacity of the structure to absorb energy. The co-factors of response reduction factor which is the overstrength factor and ductility factor reduce the design horizontal base shear coefficient. A total of 36 low-rise residential buildings having different storey, bay and bay lengths are selected and analysed in this paper. NBC 105: 2020 is selected for the seismic design of RC buildings while provision provided in FEMA 356:2000 is used to carry out non-linear pushover analysis. The results indicated that between the different structures, the value of overstrength factor and ductility factor has a high deviation.

Response Reduction Factor for Lateral Load Resisting Frames with Vertical Discontinuity of Asymmetrical Structure

In recent times, the RC building construction with vertical discontinuity that is floating column structures are unavoidable feature and increases trends day by day. To reduce lateral forces the earthquake resistance structures are designed so the response reduction factor (R) is used to determine these lateral forces by using base shear values. The R factor depends upon the overstrength factor, ductility factor, redundancy factor also the sizes of columns, types of soil, zones and load transferring path, etc. The IS code provides response reduction factor only for OMRF and SMRF along with other structures like Braced frame system, Structural wall system, Dual system, Flat slab structure wall system, etc. so there are no codal provisions for floating column structures. Thus it is essential to study the real behaviours of RC buildings with discontinuity in load transferring path through non-linear static analysis, so the present research work is done on trying to find R factor for vertical discontinuous asymmetrical structure for different soil conditions and different positions of floating column using moment resisting frames. And the structure is analyzed by response spectrum analysis and non-linear static analysis using SAP2000 software.

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.

Seismic Performance of Elevated Reinforced Concrete Water Tanks

Most of the codal provisions used worldwide for the design of elevated water tanks incorporates the nonlinear response through reduction factor that considers overstrength, ductility and redundancy. The majority of these codes provide a value which incorporates the demand of their geological condition and construction industry. In Nepal, there is lack of own guidelines and codes for the seismic design of elevated water tanks. In the present work, seismic performance of elevated reinforced concrete (RC) Intze type water tank is evaluated and value of the response reduction factor (R) for the design of such tank is determined. In this research work 34 models of elevated reinforced water tank were analyzed using SAP 2000 to evaluate the seismic performance with varying tank filling condition and staging height for 450 cumec and 225 cumec capacity. Based on the results, it is concluded that single value of response reduction factor cannot be justified for all heights and capacity of elevated RC water tank. So, for economical design purpose, estimation of response reduction factor with exact analysis is preferred.

Seismic Evaluation and Retrofit of Reinforced Concrete Buildings with Masonry Infills Based on Material Strain Limit Approach

The seismic evaluation and retrofit of reinforced concrete (RC) structures considering masonry infills is the correct methodology because the infill walls are an essential part of RC structures and increase the stiffness and strength of structures in seismically active areas. A three-dimensional four-storey building with masonry infills has been analyzed with nonlinear static adaptive pushover analysis by using the SeismoStruct software. Two models have been considered in this study: the first model is a full RC-infilled frame and the second model is an open ground storey RC-infilled frame. The infill walls have been modeled as a double strut nonlinear cyclic model. In this study, the “material strain limit approach” is first time used for the seismic evaluation of RC buildings with masonry infills. This method is based on the threshold strain limit of concrete and steel to identify the actual damage scenarios of the structural members of RC structures. The two models of the four-storey RC building have been retrofitted with local and global strengthening techniques (RC-jacketing method and incorporation of infills) as per the requirements of the structure to evaluate their effect on the response reduction factor (R) because the R-factor is an important design tool that shows the level of inelasticity in a structure. A significant increase in the response reduction factor (R) and structural plan density (SPD) has been observed in the case of the open ground storey RC-infilled frame after the retrofit. Thus, this paper aims to present a most effective way for the seismic evaluation and retrofit of any reinforced concrete structure through the material strain limit approach.

Analytical Investigation of Response Reduction Factor (R) for R.C. Elevated Water Tank with Non-linear Static (Pushover) Analysis

In the present work, an attempt is made to investigate response reduction factor (R) values of different soil types by using nonlinear static (Pushover) analysis for R.C. elevated rectangular water tank structure. All the parameters were investigated by varying properties of soft, medium and hard soils to cover a method of nonlinear static (Pushover) analysis. The zone factor (Z) kept constant Z – III for pandharpur site location and capacity of 150 m3 tank full in condition. This has resulted into SAP 2000 finite element software. The analysis of response reduction factor (R) value was done under three different soil conditions i.e. soft soil properties, medium soil properties, and hard soil properties. Response reduction factor (R) values indicate that R.C. elevated rectangular water tank structure without soil properties behaves quite the one value as per codal provisions.

Development of Indian standards in EQ resistant design of bridges – past, present and future prospects

<p>Evolution of seismic design provisions in various Indian Standards over the last 50 years have been reviewed in this paper. Seismic provisions of Bureau of Indian Standards (BIS) code (IS 1893), Indian Road Congress (IRC) standard (IRC:6 &amp; IRC:SP:114) and Indian Railway standards (IRS code) are compared. Design parameters for comparison include the seismic zone factor / peak ground acceleration, importance factor, local soil condition, design spectra and response reduction factor.</p>

Effect of Lintel Beam on Seismic Response of Reinforced Concrete Buildings with Semi-Interlocked and Unreinforced Brick Masonry Infills

The primary focus of this study is to evaluate the nonlinear response of reinforced concrete (RC) frames with two types of brick infills viz., unreinforced brick masonry infill (URM) and semi-interlocked brick masonry infill (SIM) together with lintel beams, subjected to seismic loads. The seismic response is quantified in terms of response reduction factor and base shear. Infill walls are modeled using double strut nonlinear cyclic element. Nonlinear static adaptive pushover analysis is performed in the finite element program SeismoStruct. The response reduction factor (R) is computed from adaptive pushover analysis and performance for all models is obtained. The results showed that the average R factor of the RC framed structure with semi-interlocked masonry (SIM) is 1.31 times higher than the RC frame with unreinforced masonry (URM) infill. The R value of the bare frame with the lintel beam is found to be less than the corresponding value recommended in the Indian Standard Code. The results obtained in this study highlight that if the impacts of lintel beams and various brick infill scenarios are considered in the RC frames then the R values used for the design of RC frame buildings with infills would be underestimated (i.e., the evaluated R values are greater than the R values used for the design purpose).

Evaluation of Response Reduction Factor of Existing Masonry Infilled RC-Buildings in Pokhara

Most of the structural designer do not consider masonry infill walls during design process due to a lack of modeling guidelines in design standards and are treated as non-structural elements. In fact, the interaction effect between bounding frames and infill masonry is a complicated issue in nonlinearity of structures. The current seismic codes indirectly incorporate the nonlinear response of structure through linear elastic approach by considering the response reduction factor ‘R’ without comprising infill. In this context, this study evaluates the response reduction factor of existing engineered designed RC frame structures that are designed based on Indian standard codes. For this, three existing RC buildings were selected and performed non-linear pushover analysis. The structural response was examined in terms of natural period, base shear, strength, stiffness, ductility and response reduction factor. The results specify that the buildings with infill walls significantly influence on ‘R’ value of structures. Additionally, study shows that the variation of ‘R’ value mainly depends on the percentage of infill inclusion.