Snehash Patel

Bio: Snehash Patel is an academic researcher. The author has contributed to research in topics: Call graph & Earthquake engineering. The author has an hindex of 1, co-authored 1 publications receiving 11 citations.

Earthquake resistant design of low-rise open ground storey framed building

Abstract: Presence of infill walls in the frames alters the behaviour of the building under lateral loads. However, it is common industry practice to ignore the stiffness of infill wall for analysis of framed building. Engineers believe that analysis without considering infill stiffness leads to a conservative design. But this may not be always true, especially for vertically irregular buildings with discontinuous infill walls. Hence, the modelling of infill walls in the seismic analysis of framed buildings is imperative. Indian Standard IS 1893: 2002 allows analysis of open ground storey buildings without considering infill stiffness but with a multiplication factor 2.5 in compensation for the stiffness discontinuity. As per the code the columns and beams of the open ground storey are to be designed for 2.5 times the storey shears and moments calculated under seismic loads of bare frames (i.e., without considering the infill stiffness). However, as experienced by the engineers at design offices, the multiplication factor of 2.5 is not realistic for low rise buildings. This calls for an assessment and review of the code recommended multiplication factor for low rise open ground storey buildings. Therefore, the objective of this thesis is defined as to check the applicability of the multiplication factor of 2.5 and to study the effect of infill strength and stiffness in the seismic analysis of low rise open ground storey building. Infill walls can be modelled in commercial software using two-dimensional area element with appropriate material properties for linear elastic analysis. But this type of modelling may not work for non-linear analysis since the non-linear material properties for a two-dimensional orthotropic element is not very well understood. Seismic evaluation of an existing reinforced concrete (RC) framed building would invariably require a non-linear analysis. Published literature in this area recommends a linear diagonal strut approach to model infill wall for both linear (Equivalent Static Analysis and Response Spectrum Analysis) and nonlinear analyses (Pushover Analysis and Time History Analysis). An existing RC framed building (G+3) with open ground storey located in Seismic Zone-V is considered for this study. This building is analyzed for two different cases: (a) considering both infill mass and infill stiffness and (b) considering infill mass but without considering infill stiffness. Two separate models were generated using commercial software SAP2000. Infill weights were modelled through applying static dead load and corresponding masses considered from this dead load for dynamic analyses. Infill stiffness was modelled using a diagonal strut approach. Two different support conditions, namely fixed end support condition and pinned end support condition, are considered to check the effect of support conditions in the multiplication factors. Linear and non-linear analyses were carried out for the models and the results were compared. The analysis results show that a factor of 2.5 is too high to be multiplied to the beam and column forces of the ground storey of low-rise open ground storey buildings. This study conclude that the problem of open ground storey buildings cannot be identified properly through elastic analysis as the stiffness of open ground storey building and a similar bare-frame building are almost same. Nonlinear analysis reveals that open ground storey building fails through a ground storey mechanism at a comparatively low base shear and displacement and the mode of failure is found to be brittle. Linear and nonlinear analyses show that support condition influences the response considerably and can be an important parameter to decide the force amplification factor.

Uncovering Steady State Executions in Java Microbenchmarking with Call Graph Analysis

Abstract: Developers often use microbenchmarking tools to evaluate the performance of a Java program. These tools run a small section of code multiple times and measure its performance. However, this process can be problematic as Java execution is traditionally divided into two stages: a warmup stage where the JVM's JIT compiler optimizes frequently used code and a steady stage where performance is stable. Measuring performance before reaching the steady stage can provide an inaccurate representation of the program's efficiency. The challenge comes from determining when a program should be considered as in a steady state. In this paper, we propose that call stack sampling data should be considered when conducting steady state performance evaluations. By analyzing this data, we can generate call graphs for individual microbenchmark executions. Our proposed method of using call stack sampling data and visualizing call graphs intuitively empowers developers to effectively distinguish between warmup and steady state executions. Additionally, by utilizing machine learning classification techniques this method can automate the steady state detection, working towards a more accurate and efficient performance evaluation process.

Seismic Risk Assessment of RC Framed Vertically Irregular Buildings

Abstract: The area of vertically irregular type of building is now having a lot of interest in seismic research field. Vertical irregularity arises in the buildings due to the significant change in stiffness and strength. The typical OGS and stepped types of irregularities are considered in the present study. For OGS buildings, the Magnification factors (MF) are suggested by the design codes. The present study focus on the performance of typical OGS buildings designed considering various magnification factors as well as the stepped type buildings with different geometry configurations using fragility analysis. The critical inter-storey drift is considered as an intensity measure. Various heights (6, 8 &10 stories) are considered for the present study. Fragility curves are developed for each type of buildings as per the methodology introduced by Cornell (2002). PSDM models are developed for each frames and the corresponding fragility curves are generated. It is observed that in terms of performance, a building with infill walls in all stories is equally comparable with an OGS framed building with MF of about 1.5. Performance of the OGS frame increases with the increase in MF, but it makes the adjacent storey vulnerable. The study is extended to the seismic reliability for all the considered buildings. The reliability is found out by combining a fragility curve with a seismic hazard curve of the region. The seismic hazard curve for the present study is chosen from the study conducted by Pallav et. al (2012). The performance of the buildings is assessed by comparing the reliabilities achieved with the target reliabilities suggested as per ISO 2394 (1998). It is observed that the frames without any infill walls failed to achieve the target reliabilities whereas the buildings with infill walls achieved the target reliabilities. The stiffness of infill walls is a significant factor that improves the performance of buildings during earthquakes.

Seismic Behaviour of Open Ground Storied Building

Abstract: The concept of open ground building (OGS) has taken its place in the Indian urban environment due to the fact that it provides the parking facility in the ground storey of the building. The cost of construction of this type of building is much less than that of a building with basement parking. Surveys of buildings failed in the past earthquakes show that this types of buildings are found to be one of the most vulnerable. The majority of buildings that failed during the Bhuj earthquake (2001) and Gujarat earthquake were of the open ground storey type. Many low-rise and medium rise framed buildings have been constructed in the recent past, without proper attention paid in their design for wind or earthquake loads. The collapse mechanism of such type of building is predominantly due to the formation of soft-storey behavior in the ground storey of this type of building. The sudden reduction in lateral stiffness and mass in the ground storey results in higher stresses in the columns of ground storey under seismic loading. Therefore it is need of time to take immediate measures to prevent the indiscriminate use of soft first storey in buildings. With the availability of fast computers, so that software usage in civil engineering has greatly reduced the complexities of different aspects in the analysis and design of projects. In the dissertation work a parametric study is performed on multistoried building with soft first storey, located in seismic zone III. The study is carried out on a building with the help of different mathematical models considering various methods for improving the seismic performance of the building with soft first storey. Analytical models represent all existing components that influence the mass, strength, stiffness and deformability of structure. It is intended to describe the performance characteristics such as storey drift, inter-storey drift, shear force, bending moment, base shear, time period and frequency. The response spectrum and time history analysis is carried out on the entire mathematical 3D model using the software SAP2000. The objective of this study is to identify an efficient retrofitting method for open ground story reinforced concrete frame buildings. The effect of window opening is also considering. The results are compared and conclusions are made in view of IS-1893 (2002) code. Keywords—Clay brick infill wall, Autoclaved Aerated Concrete, Soft Storey, Equivalent Diagonal Strip Method.

Seismic Comparison of Commercial Building between Equivalent Static Analysis and Response Spectrum Analysis

Abstract: Earthquake is very severe problem nowadays. As the commercial building are having large amount of rush daily so such type of the building should be earthquake resistant. We are going to study the behaviour of commercial building against seismic load. A comparison is done using ETABS software in different seismic zones using response spectrum method and equivalent static analysis method, then it is finally concluded that which method is effective and economic. Different parameters are compared using graphical and tabular form. Keyword: ETABS, Equivalent Static Analysis, Response Spectrum Analysis, Commercial Building

Structural analysis of traditional Batak Karo house against earthquake

Abstract: The Karo traditional house studied was gerga sepulu dua jabu in Lingga village. The structure is modelled into frames and 3D models. Structural irregularity will be analyzed and spectral response analysis were carried out with SAP 2000. Earthquake resistance is determined based on period, base shear force, friction between rock with piles, story drift and appearance analysis. Horizontally the Batak Karo traditional house is regular but vertically has an irregularity that is mass irregularity, vertical geometry, discontinuity in the direction of holding horizontal force. From the SAP 2000 analysis, a period of 0.107993 seconds was obtained, a basic shear of 94.884 kN, a friction force between the rock with piles a 94.884 kN, story drift of 8.068 mm. Column axial force 152,755 kN, beam bending moment 16,372 kNm and beam shear force 47,982 kN. The upper limit of the period is 0.4676 seconds, dynamic shear force of 80.561 kN, rock friction with 368.55 kN, and 37 mm deviation. Column compressive force 1864.01 kN, beam bending moment 36,277 kNm, and beam shear force 380,725 kN. Based on that, it can be concluded that the Karo traditional house is safe from earthquakes.

Study of Soil-Structure Interaction and Vertical Irregularity on Open Ground Storey Building

Abstract: Open ground storey buildings are usually used for parking in urban areas. During the past earthquakes the vulnerability of these buildings became clear. Bare frame analysis is used for designing the OGS buildings. These underestimates the inter-storey drifts. A Multiplication Factor (MF) was introduced in order to avoid the above problem while calculating design forces. The multiplication factor used varies with various international codes. Present study focuses on the evaluation of seismic performances of regular and vertically irregular OGS buildings designed with various soil conditions. Also this work helps in understanding the effect of earthquake with various soil conditions. In this work effect of vertical irregularity in open ground storey building is also studied. For the modelling of the building the software ETABS is used and the analysis is done using response spectrum method.