Department of Earthquake Engineering (1991 - Present)
Civil Engineering, Structures
, Delhi Technology, India
Civil Engineering
, India, India
Civil Engineering
, India, India
This study presents the impact of near-field and far-field earthquakes on the seismic design of Intermediate Moment Resisting Frame (IMRF) and Special Moment Resisting Frame (SMRF) structures through FEMA (Federal Emergency Management Agency) P695 methodology to highlight the importance of probabilistic collapse as well as seismic performance factors of these structures. The purpose of this study is to investigate the collapse performance of steel intermediate and special moment resisting frame systems as the most common structural systems in urban areas in order to assess the seismic performance factors used for the design using nonlinear static and dynamic analysis methods. In this regard, as the representatives of low-rise
The effect of mass and stiffness vertical irregularities on the collapse mechanism and resistance of steel high-rise structures is investigated using 3-D numerical simulations. Simulations are carried out utilizing a verified modelling approach in which the collapse processes of a regular and four irregular structures are studied under 11 earthquake records. It is indicated that the utilized finite element model, related considerations and calibrations present a reliable and efficient technique for collapse simulation. The findings show that vertical irregularities adversely affect the collapse resistance and mechanism of steel high-rise buildings. Especially, mass vertical irregularity with concentration in the lower half of the structure
In this research the effect of diameter to thickness of pipe ratio (D/t), depth of burial to diameter (H/D) ratio, conditions of surrounding soil and different grades of steel on the seismic answer of straight buried steel pipelines is investigated within a probabilistic context. The results of incremental dynamic analysis of 15 pipeline models are used to evaluate the capacities of performance limit, the mean annual frequency (MAF) of exceeding structural limit states and levels of confidence of achieving seismic performance goals. It is obtained that for the pipes with the ratios of D/t over 39.9, increasing the ratio of D/t decreases the IM capacity, increases MAF of exceeding the performance objectives and reduces the confidence level
In this paper, three new performance indices are proposed which can be used in order to determine the global performance of a given structure. The ASCE41-13 standard and the FEMA350 guidelines are used as representatives of, respectively, an element-oriented and a system-oriented performance-based assessment algorithm. Two ten-storeyed special steel moment frames, consisting of a regular and an irregular structure, are designed and assessed using these two algorithms. The results show that the element-oriented assessment algorithm significantly underestimates the seismic demand and capacity, especially in the case of the immediate occupancy and collapse prevention limit states. This underestimation can cause a significant drop in the estima
In conventional engineering practice, the use of stiffeners and flanges on both faces of stiffened web panels for I-shaped link beams provides fully restrained boundary conditions. In tubular link beams, however, the stiffened web panels possess simply supported boundary conditions due to the use of single-sided stiffeners and flanges.This study investigates the boundary condition effects of stiffened web panels in tubular and I-shaped link beams on their rotation capacity assuming similar area, moment of inertia, length and stiffener spacing. Based on the numerical results, I-shaped link beams demonstrated an approximately 78% higher rotation capacity compared to tubular link beams under the same conditions which could be due to the better
Diagrid system has emerged as an innovative structural system with an aesthetic view in the design of tall buildings. In this study, seismic performance of 36-story diagrid structures with varying angles are evaluated using pushover and nonlinear time history analysis. Furthermore, in order to evaluate the effect of diagrid core on behavior of structures, interior gravity frames are replaced with diagrid frames. The results of pushover analyses demonstrate that diagrid core can enhance the hardening behavior of structures when the angles of perimeter panels are lower or equal than those of the core compared to the conventional diagrids. In addition, core diagrids provide safe margins between the damage states under lateral loading. Nonlinea
In this research, the probabilistic seismic performance of asymmetric reinforced concrete wall-frame buildings with different strength distributions incorporating foundation flexibility effects is examined. By using probability-based performance evaluation approach, it is possible to provide a more accurate prediction of the different strength distribution effect on the seismic performance of asymmetric buildings and find the most efficient strength distribution for meeting each performance level. These efficient distributions can be adopted in the performance-based design of asymmetric buildings. For this purpose, first, the regression analysis and the concepts of efficiency and sufficiency were used to determine an optimal intensity measu
This paper presents a comprehensive structural assessment of the fire-induced progressive collapse of Plasco Building, in January 2017. The assessment employs a three-phase approach: a) field investigation to collect data about the building and the event, b) structural evaluation against service loads, c) progressive collapse analysis. A collapse scenario is proposed, which is simulated using finite element modelling and numerical analysis. The results showed the adequacy of the building for service loads, while its significant vulnerability against progressive collapse. The vulnerability was mainly due to the lack of adequate continuity, ductility, and redundancy to resist the spread of damage. The weakest link in the structural system was
Elevated water tanks are categorized as strategic components of water supply systems in modern urban management. Past earthquake events have revealed the high vulnerability of these structures. This paper investigates the development of rocking isolation (RI) to these structures as a response mitigation technique. Using an analytical approach, a dynamic model is developed for two isolation cases: (1) at the pedestal base and (2) under the tank. The model incorporates a simplified analogy for simulating the liquid-tank system which is modified for a tank under rocking motions. Based on the dynamics of rocking structures, the equations of motion, impact, and uplift transitions are derived. Then, free vibration and seismic response history ana
Spectrum compatibility is commonly used as a tool for ground motion record selection in order to perform dynamic analysis. Conditional mean spectrum calculation, which can be used as a target spectrum, requires obtaining correlation coefficients between spectral acceleration values at multiple periods. To date, the correlation coefficients have not been evaluated exclusively from ground motions recorded in Iran. This study represents results obtained from the calculation of correlations for spectral acceleration values from Iranian ground motion data and Zagros and Alborz-central Iran seismic regions, separately. The obtained results can be used for conditional mean spectrum calculations at Iranian sites. The observed correlation coefficien
{Lifelines are essential for human life and economic development. Buried steel pipelines are the sort of lifelines that their strength under extreme events, such as earthquakes, is very essential. One of the causes of failure of buried pipelines is seismic wave propagation. Buried steel pipelines are vulnerable in extreme events such as earthquakes. In this study vulnerability of buried steel pipelines was evaluated using the results of incremental dynamic analysis (IDA). Several IDA analyses of three buried steel pipe models with a different diameter to thickness and burial depth to diameter ratios and different soil properties, were performed using far-field earthquake ground motion records. The models were designed based on American Life
The tubular structures are having the capability of resisting wind and earthquake loads with the exterior tube system. Tube systems consist of closely spaced exterior columns and deep beams around the corner of the plan that provides sufficient rigidity and stability for tall/high-rise buildings. Another advantage of the tubular system is the significant reduction in the building materials and increasing the architectural space in the internal plan. The mentioned cases have increased the popularity of this kind of structural system. But the most important problem in the tube system is the shear lag. Shear lag is the non-uniform distribution of stress on the face columns when the tube system is subjected to lateral loads. Shear lag can occur
The effects of irregularities along the height of structure on the basis of mass, stiffness, strength, and the combination of stiffness-strength are investigated in this study by means of dual steel structures consisting of special steel moment frame and special concentric braced frames. The Performance-based earthquake engineering has been implemented in the form of probabilistic confidence level by means of incremental dynamic analysis in order to obtain seismic demand and capacity. A set of ten-storeyed steel moment frames is taken into consideration with different irregularity cases along the height of structure. All considered structures are first carefully designed based on 4th edition of the Iranian practice for seismic-resistance de
The effects of irregularities along the height of structure on the basis of mass, stiffness, strength, and the combination of stiffness-strength are investigated in this study by means of dual steel structures consisting of special steel moment frame and special concentric braced frames. The Performance-based earthquake engineering has been implemented in the form of probabilistic confidence level by means of incremental dynamic analysis in order to obtain seismic demand and capacity. A set of ten-storeyed steel moment frames is taken into consideration with different irregularity cases along the height of structure. All considered structures are first carefully designed based on 4th edition of the Iranian practice for seismic-resistance de
In this paper economic seismic risk analysis of API 5L buried steel gas pipelines is carried out through incremental dynamic analysis using an ensemble of 20 ground motion records. Multiple performance limit states for buried steel pipelines are proposed. Fragility curves of 15 pipeline models of various diameter to thickness (D/t) ratios, burial depth to diameter (H/D) ratios, assumed soil conditions and steel grades are plotted for damage states corresponding to the defined limit states. Expected global economic loss of 1?km length of the pipelines for a given peak ground velocity is obtained using the fragility curves, a pipeline repair ratio as well as costs of leakage repairing and break-induced pipe replacement. The mea
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