A software (EQK_SRC_PARA) has been developed to estimate spectral parameters of earthquake source spectrum, namely: low frequency displacement spectral level (Ω0), corner frequency above which spectrum decays with a ...A software (EQK_SRC_PARA) has been developed to estimate spectral parameters of earthquake source spectrum, namely: low frequency displacement spectral level (Ω0), corner frequency above which spectrum decays with a rate of 2 (fc), the cut-off frequency above which the spectrum again decays (fmax) and the rate of decay above fmax (N). A Brune’s source model [1,2] that yield a fall-off of 2 beyond corner frequency is considered with high cut-off frequency factor presented by Boore [3] that fits well for frequencies greater than fmax. The software EQK_SRC_PARA is written in MATLAB and uses input data in Sesame ASCII Format (SAF) format. The obtained spectral parameters have been used to estimate source parameters (e.g., seismic moment, source dimension and stress drop etc.) and to develop scaling laws for the study region. The cut-off frequency “fmax” can also be studied and interpreted to confirm about its origin.展开更多
It is already well known that the “when, where and how strong” earthquake prediction problem cannot be solved by only analyzing the database from former earthquakes. A possible solution to this problem is proposed h...It is already well known that the “when, where and how strong” earthquake prediction problem cannot be solved by only analyzing the database from former earthquakes. A possible solution to this problem is proposed herein based on the analysis of the physicochemical processes as participants in earthquake preparation and on the characteristic rate of reflection of these processes on the Earth’s surface. The proposed procedure includes monitoring of correlation of electromagnetic fields variations with tidal waves.?This solution provides a way of selecting a complex of reliable earthquake precursors using the Inverse Problem Method for earthquakes which will occur in the region around the monitoring point (radial distance ≈ 700 km) in the next seven-day period [1].展开更多
Past research has focused on the factors that influence liquefaction under normal shaking conditions.However,studies on parameters that influence the reliquefaction potential of saturated deposits during repeated shak...Past research has focused on the factors that influence liquefaction under normal shaking conditions.However,studies on parameters that influence the reliquefaction potential of saturated deposits during repeated shaking events are limited.In this study,an attempt has been made to examine the influence of acceleration amplitude and shaking duration on liquefaction and reliquefaction potential under repeated shaking conditions is conducted.1-g uni-axial shaking table experiments were performed on saturated ground prepared with 40%and 60%relative density.The prepared ground was subjected to alternate longer and shorter shaking durations(40 and 20 s)of repeated incremental 0.1 g,0.2 g,0.3 g and 0.4 g acceleration loading,respectively.The variation in density,excess pore water pressure(EPWP),cyclic resistance ratio(CRR)and surface settlement were estimated.The results showed that due to repeated incremental shaking events,reliquefaction was observed on the prepared ground.During longer shaking duration,the post-liquefied soil showed density improvement with improved soil resistance.However,the application of shorter duration loading followed by longer shaking reduced the beneficial effect of density improvement by disturbing the densified ground.Due to this,the ground was found to be more susceptible to reliquefaction in the subsequent incremental longer shaking event.展开更多
The available models for eff ective periods of site and structure are reviewed in context of frequency tuning in the inelastic seismic response of soil-structure system. The eff ect of seismic intensity and ductility ...The available models for eff ective periods of site and structure are reviewed in context of frequency tuning in the inelastic seismic response of soil-structure system. The eff ect of seismic intensity and ductility demand, on the eff ective periods, is investigated, and inelastic site amplifi cation is shown to be strongly correlated to the normalized eff ective period. Two non-dimensional parameters, analogous to the conventional site amplifi cation factors in codes, are defi ned to quantify the inelastic site amplifi cation. It is shown that the inelastic site amplifi cation factor (i.e. ratio of constant ductility spectral ordinates at soil site to those at rock outcrop) is able to represent the site eff ects more clearly, as compared to the inelastic site amplifi cation ratio (i.e. ratio of inelastic spectral ordinates at soil site to the corresponding elastic spectral ordinates at rock outcrop). Further, the peak in the amplifi cation factor corresponding to the eff ective site period diminishes rapidly with increasing ductility demand.展开更多
Analytical models prepared from field drawings do not generally provide results that match with experimental results.The error may be due to uncertainties in the property of materials,size of members and errors in the...Analytical models prepared from field drawings do not generally provide results that match with experimental results.The error may be due to uncertainties in the property of materials,size of members and errors in the modelling process.It is important to improve analytical models using experimentally obtained data.For the past several years,data obtained from ambient vibration testing have been successfully used in many cases to update and match dynamic behaviors of analytical models with real structures.This paper presents a comparison between artificial neural network(ANN) and eigensensitivity based model updating of an existing multi-story building.A simple spring-mass analytical model,developed from the structural drawings of the building,is considered and the corresponding spring stiffness and lumped mass of all floors are chosen as updating parameters.The advantages and disadvantages of these updating methods are discussed.The advantage is that both methods ensure a physically meaningful model which canbe further employed in determining structural response and health monitoring.展开更多
The impact of earthquakes in urban centers prone to disastrous earthquakes necessitates the analysis of associated risk for rational formulation of contingency plans and mitigation strategies. In urban centers, the se...The impact of earthquakes in urban centers prone to disastrous earthquakes necessitates the analysis of associated risk for rational formulation of contingency plans and mitigation strategies. In urban centers, the seismic risk is best quantified and portrayed through the preparation of 'Earthquake Damage and Loss Scenarios.' The components of such scenarios are the assessment of the hazard, inventories and the vulnerabilities of elements at risk. For the development of the earthquake risk scenario in Istanbul, two independent approaches, one based on intensities and the second on spectral displacements, are utilized. This paper will present the important features of a comprehensive study, highlight the methodology, discuss the results and provide insights to future developments.展开更多
Flat slab system is becoming widely popular for multistory buildings due to its several advantages. However, the performance of flat slab buildings under earthquake loading is unsatisfactory due to their vulnerability...Flat slab system is becoming widely popular for multistory buildings due to its several advantages. However, the performance of flat slab buildings under earthquake loading is unsatisfactory due to their vulnerability to punching shear failure. Several national design codes provide guidelines for designing flat slab system under gravity load only. Nevertheless, flat slab buildings are also being constructed in high seismicity regions. In this paper, performance of flat slab buildings of various heights, designed for gravity load alone according to code, is evaluated under earthquake loading as per ASCE/SEI 41 methodology. Continuity of slab bottom reinforcement through column cage improves the performance of flat slab buildings to some extent, but it is observed that these flat slab systems are not adequate in high seismicity areas and need additional primary lateral load resisting systems such as shear walls. A displacement-based method is proposed to proportion shear walls as primary lateral load resisting elements to ensure satisfactory performance. The methodology is validated using design examples of flat slab buildings with various heights.展开更多
The Himalayan region is one of the major seismic areas in the world.However,similar to many other seismically active locations,there are substantial numbers of unreinforced masonry(URM)buildings;the majority of which ...The Himalayan region is one of the major seismic areas in the world.However,similar to many other seismically active locations,there are substantial numbers of unreinforced masonry(URM)buildings;the majority of which have not been designed for seismic loads.Past seismic events have shown that such buildings are highly vulnerable to earthquakes.Retrofitting of these URM buildings is an important concern in earthquake mitigation programs.Most government school buildings in rural areas of northern India are constructed of unreinforced masonry.These school buildings are socially important structures and serve as a crucial resource for rehabilitation during any disaster.The effectiveness of ferrocement(FC)to create a URM-FC composite is described in this study by estimating the performance and fragility of a URM school building before and after a retrofit.Analytical models,based on the equivalent frame method,are developed and used for nonlinear static analysis to estimate the enhancement in capacity.The capacity enhancement due to retrofitting is presented in terms of the maximum PGA sustained and damage probabilities at the expected level of earthquake hazard.展开更多
Unreinforced Masonry(URM) is the most common partitioning material in framed buildings in India and many other countries.Although it is well-known that under lateral loading the behavior and modes of failure of the fr...Unreinforced Masonry(URM) is the most common partitioning material in framed buildings in India and many other countries.Although it is well-known that under lateral loading the behavior and modes of failure of the frame buildings change significantly due to infill-frame interaction,the general design practice is to treat infills as nonstructural elements and their stiffness,strength and interaction with the frame is often ignored,primarily because of difficulties in simulation and lack of modeling guidelines in design codes.The Indian Standard,like many other national codes,does not provide explicit insight into the anticipated performance and associated vulnerability of infilled frames.This paper presents an analytical study on the seismic performance and fragility analysis of Indian code-designed RC frame buildings with and without URM infills.Infills are modeled as diagonal struts as per ASCE 41 guidelines and various modes of failure are considered.HAZUS methodology along with nonlinear static analysis is used to compare the seismic vulnerability of bare and infilled frames.The comparative study suggests that URM infills result in a significant increase in the seismic vulnerability of RC frames and their effect needs to be properly incorporated in design codes.展开更多
Experimental evaluation of reinforced concrete beam specimens with different characteristics of reinforcement subjected to pushover and cyclic loading is presented.Plastic hinge rotation parameters are determined base...Experimental evaluation of reinforced concrete beam specimens with different characteristics of reinforcement subjected to pushover and cyclic loading is presented.Plastic hinge rotation parameters are determined based on the idealization of pushover and hysteresis curves of reinforced concrete beam specimens constructed in two percentage of reinforcement(0.471%and 0.71%) with different ductile characteristics.The experimental test results provide a clear demarcation of the effect of types of loading and the types of reinforcement on the nonlinear performance characteristics of beam specimens.These results are helpful to update the nonlinear modeling parameters of beam components for the specific type of reinforcement used in the construction of a structure.The updated non-linear modeling parameters of beam components in lumped plasticity model are compared with the values of ASCE/SEI 41-06(2007) used for the performance based design of structures.展开更多
2D finite element models were developed to analyze the effect of improved soft-soil foundation on the efficiency of a base-isolated concrete frame.Static and dynamic analyses were performed for a frame on raft foundat...2D finite element models were developed to analyze the effect of improved soft-soil foundation on the efficiency of a base-isolated concrete frame.Static and dynamic analyses were performed for a frame on raft foundation.Non-improved and improved soft-soil foundation using rigid inclusions were considered,as well as the use of high damping rubber bearing as base isolation.Results show that the use of rigid inclusions increases the efficiency of base isolation;base shear is reduced by 38% and maximum acceleration at the top of the frame by 30%.展开更多
Tire wastes have many properties that are valuable from a geotechnical engineering perspective, such as low density, high strength, thermal insulation, energy absorption capacity, permeability, durability, compressibi...Tire wastes have many properties that are valuable from a geotechnical engineering perspective, such as low density, high strength, thermal insulation, energy absorption capacity, permeability, durability, compressibility, resilience, and high frictional strength. Thus, tire wastes offer good thermal characteristics in resisting frost penetration and have good drainage characteristics, being as permeable as coarse granular soil for fill materials. The many advantages of tire wastes make the material suitable for transportation infrastructure construction in cold regions. Also, tire wastes with high damping property make them a preferable admixture with sand for transportation infrastructures in seismic regions. This study aimed to determine the seismic performance of certain tire waste-sand mixtures in cold regions. A 70% sand-30% tire crumb mixture by weight(TC30) with a very high damping property was selected for analysis as an engineering material for transportation infrastructure. Small-scale shake-table tests were conducted on this material as well as on a sand-only sample under two different temperatures, 0 °C and 20 °C, to simulate cold-region and moderate-temperature performance, respectively. The 1999 ?zmit Earthquake Excitation(EW)(Mw = 7.4) was taken as the input motion. Test results showed that the tire waste-sand mixture at 0 °C showed better seismic performance than that at room temperature, suggesting that a tire waste-sand mixture in cold regions may reduce seismic hazards to infrastructure.展开更多
In the present study,the spatial-temporal distribution of b-value along the five faults area(the Judi fault,Thaple fault,Kathmandu fault,Motihari-Gauri Shanker fault,and Motihari-Everest fault)was investigated after t...In the present study,the spatial-temporal distribution of b-value along the five faults area(the Judi fault,Thaple fault,Kathmandu fault,Motihari-Gauri Shanker fault,and Motihari-Everest fault)was investigated after the Gorkha earthquake(M7.8).The earthquake catalog of 10,500 events was prepared by compiling the published catalogs.The study area is bounded in the central Himalaya from 26.5°to 29°in latitude direction and 84°to 87°in longitude direction.The frequency magnitude distribution shows the variation of the b-value along with fault areas from 0.45 to 0.69,indicating a common characteristic of aftershock sequences.In particular,the Judi fault area,Thaple fault area,and Motihari-Everest fault area are characterized by the low b-values of 0.45±0.02,0.48±0.02,and 0.55±0.04,respectively.These regions could be the source region for future earthquakes.The low b-value observed for fault areas are also consistent with the thrust faulting pattern in the region as indicated by the focal mechanism of mainshock and major aftershocks.The temporal variation of b-value shows inevitable fluctuations during25 April to 12 May 2015.Among the area selected,the Motihari-Everest fault area is in critical strain(mechanically locked)conditions,as indicated by the stepwise energy release pattern.展开更多
Indian Institute of Technology, Roorkee (IITR) is operating a nationwide network of instruments for recording strong ground motion. Total 300 instruments are installed in seismic zone III, IV and V along Himalayan bel...Indian Institute of Technology, Roorkee (IITR) is operating a nationwide network of instruments for recording strong ground motion. Total 300 instruments are installed in seismic zone III, IV and V along Himalayan belt. Primary goal of this project is to acquire strong ground-motion (SGM) data for various studies in the field of earthquake engineering and seismology in general and in particular to understand propagation and site response characteristics of the sediments that underlie and are thought to produce large site amplification and seismic hazard. These data will complement laboratory data to characterize the properties of the soft soils underlying residential area so that engineers and architects can design appropriate earthquake-resistant structures for the region. The successful working of this network has laid the foundation of Earthquake Early Warning System (EEW) in India. A great number of strong motion records have been obtained and utilized to study local site and geological effects. The paper introduces outline of the IITR strong motion network and some of its recent studies.展开更多
With the recent development of digital Micro Electro Mechanical System(MEMS) sensors, the cost of monitoring and detecting seismic events in real time can be greatly reduced. Ability of MEMS accelerograph to record a ...With the recent development of digital Micro Electro Mechanical System(MEMS) sensors, the cost of monitoring and detecting seismic events in real time can be greatly reduced. Ability of MEMS accelerograph to record a seismic event depends upon the efficiency of triggering algorithm, apart from the sensor′s sensitivity. There are several classic triggering algorithms developed to detect seismic events, ranging from basic amplitude threshold to more sophisticated pattern recognition. Algorithms based on STA/LTA are reported to be computationally efficient for real time monitoring. In this paper, we analyzed several STA/LTA algorithms to check their efficiency and suitability using data obtained from the Quake Catcher Network(network of MEMS accelerometer stations). We found that most of the STA/LTA algorithms are suitable for use with MEMS accelerometer data to accurately detect seismic events. However, the efficiency of any particular algorithm is found to be dependent on the parameter set used(i.e., window width of STA, LTA and threshold level).展开更多
Site-specific seismic hazard analysis is crucial for designing earthquake resistance structures,particularly in seismically active regions.Shear wave velocity(V_(S))is a key parameter in such analysis,although the eco...Site-specific seismic hazard analysis is crucial for designing earthquake resistance structures,particularly in seismically active regions.Shear wave velocity(V_(S))is a key parameter in such analysis,although the economy and other factors restrict its direct field measurement in many cases.Various V_(S)-SPT-N correlations are routinely incorporated in seismic hazard analysis to estimate the value of V_(S).However,many uncertainties question the reliability of these estimated V_(S)values.This paper comes up with a statistical approach to take care of such uncertainties involved in V_(S)calculations.The measured SPT-N values from all the critical boreholes were converted into statistical parameters and passed through various correlations to estimate V_(S)at different depths.The effect of different soil layers in the boreholes on the V_(S)estimation was also taken into account.Further,the average shear wave velocity of the top 30 m soil coverV_(S30))is estimated after accounting for various epistemic and aleatoric uncertainties.The scattering nature of the V_(S)values estimated using different V_(S)-N correlations was reduced significantly with the application of the methodology.Study results further clearly demonstrated the potential of the approach to eliminate various uncertainties involved in the estimation of V_(S)30 using general and soil-specific correlations.展开更多
The aim of this research is to assess the seismic performance of reinforced concrete columns under different axial load and transverse reinforcement ratios. These two parameters are very important as for the ductility...The aim of this research is to assess the seismic performance of reinforced concrete columns under different axial load and transverse reinforcement ratios. These two parameters are very important as for the ductility, strength, stiffness, and energy dissipation capacity for a given reinforced concrete column. Effects of variable axial load ratio and transverse reinforcement ratio on the seismic performance of reinforced concrete columns are thoroughly analyzed. The finite element computer program Seismo-Structure was used to perform the analysis of series of reinforced concrete columns tested by the second author and other researchers. In order to reflect the reality and grasp the actual behavior of the specimens, special attention was paid to select the models for concrete, confined concrete, and steel components. Good agreements were obtained between the experimental and the analytical results either for the lateral force-drift relationships or for the damage progress prediction at different stages of the loading.展开更多
文摘A software (EQK_SRC_PARA) has been developed to estimate spectral parameters of earthquake source spectrum, namely: low frequency displacement spectral level (Ω0), corner frequency above which spectrum decays with a rate of 2 (fc), the cut-off frequency above which the spectrum again decays (fmax) and the rate of decay above fmax (N). A Brune’s source model [1,2] that yield a fall-off of 2 beyond corner frequency is considered with high cut-off frequency factor presented by Boore [3] that fits well for frequencies greater than fmax. The software EQK_SRC_PARA is written in MATLAB and uses input data in Sesame ASCII Format (SAF) format. The obtained spectral parameters have been used to estimate source parameters (e.g., seismic moment, source dimension and stress drop etc.) and to develop scaling laws for the study region. The cut-off frequency “fmax” can also be studied and interpreted to confirm about its origin.
文摘It is already well known that the “when, where and how strong” earthquake prediction problem cannot be solved by only analyzing the database from former earthquakes. A possible solution to this problem is proposed herein based on the analysis of the physicochemical processes as participants in earthquake preparation and on the characteristic rate of reflection of these processes on the Earth’s surface. The proposed procedure includes monitoring of correlation of electromagnetic fields variations with tidal waves.?This solution provides a way of selecting a complex of reliable earthquake precursors using the Inverse Problem Method for earthquakes which will occur in the region around the monitoring point (radial distance ≈ 700 km) in the next seven-day period [1].
文摘Past research has focused on the factors that influence liquefaction under normal shaking conditions.However,studies on parameters that influence the reliquefaction potential of saturated deposits during repeated shaking events are limited.In this study,an attempt has been made to examine the influence of acceleration amplitude and shaking duration on liquefaction and reliquefaction potential under repeated shaking conditions is conducted.1-g uni-axial shaking table experiments were performed on saturated ground prepared with 40%and 60%relative density.The prepared ground was subjected to alternate longer and shorter shaking durations(40 and 20 s)of repeated incremental 0.1 g,0.2 g,0.3 g and 0.4 g acceleration loading,respectively.The variation in density,excess pore water pressure(EPWP),cyclic resistance ratio(CRR)and surface settlement were estimated.The results showed that due to repeated incremental shaking events,reliquefaction was observed on the prepared ground.During longer shaking duration,the post-liquefied soil showed density improvement with improved soil resistance.However,the application of shorter duration loading followed by longer shaking reduced the beneficial effect of density improvement by disturbing the densified ground.Due to this,the ground was found to be more susceptible to reliquefaction in the subsequent incremental longer shaking event.
文摘The available models for eff ective periods of site and structure are reviewed in context of frequency tuning in the inelastic seismic response of soil-structure system. The eff ect of seismic intensity and ductility demand, on the eff ective periods, is investigated, and inelastic site amplifi cation is shown to be strongly correlated to the normalized eff ective period. Two non-dimensional parameters, analogous to the conventional site amplifi cation factors in codes, are defi ned to quantify the inelastic site amplifi cation. It is shown that the inelastic site amplifi cation factor (i.e. ratio of constant ductility spectral ordinates at soil site to those at rock outcrop) is able to represent the site eff ects more clearly, as compared to the inelastic site amplifi cation ratio (i.e. ratio of inelastic spectral ordinates at soil site to the corresponding elastic spectral ordinates at rock outcrop). Further, the peak in the amplifi cation factor corresponding to the eff ective site period diminishes rapidly with increasing ductility demand.
文摘Analytical models prepared from field drawings do not generally provide results that match with experimental results.The error may be due to uncertainties in the property of materials,size of members and errors in the modelling process.It is important to improve analytical models using experimentally obtained data.For the past several years,data obtained from ambient vibration testing have been successfully used in many cases to update and match dynamic behaviors of analytical models with real structures.This paper presents a comparison between artificial neural network(ANN) and eigensensitivity based model updating of an existing multi-story building.A simple spring-mass analytical model,developed from the structural drawings of the building,is considered and the corresponding spring stiffness and lumped mass of all floors are chosen as updating parameters.The advantages and disadvantages of these updating methods are discussed.The advantage is that both methods ensure a physically meaningful model which canbe further employed in determining structural response and health monitoring.
文摘The impact of earthquakes in urban centers prone to disastrous earthquakes necessitates the analysis of associated risk for rational formulation of contingency plans and mitigation strategies. In urban centers, the seismic risk is best quantified and portrayed through the preparation of 'Earthquake Damage and Loss Scenarios.' The components of such scenarios are the assessment of the hazard, inventories and the vulnerabilities of elements at risk. For the development of the earthquake risk scenario in Istanbul, two independent approaches, one based on intensities and the second on spectral displacements, are utilized. This paper will present the important features of a comprehensive study, highlight the methodology, discuss the results and provide insights to future developments.
文摘Flat slab system is becoming widely popular for multistory buildings due to its several advantages. However, the performance of flat slab buildings under earthquake loading is unsatisfactory due to their vulnerability to punching shear failure. Several national design codes provide guidelines for designing flat slab system under gravity load only. Nevertheless, flat slab buildings are also being constructed in high seismicity regions. In this paper, performance of flat slab buildings of various heights, designed for gravity load alone according to code, is evaluated under earthquake loading as per ASCE/SEI 41 methodology. Continuity of slab bottom reinforcement through column cage improves the performance of flat slab buildings to some extent, but it is observed that these flat slab systems are not adequate in high seismicity areas and need additional primary lateral load resisting systems such as shear walls. A displacement-based method is proposed to proportion shear walls as primary lateral load resisting elements to ensure satisfactory performance. The methodology is validated using design examples of flat slab buildings with various heights.
文摘The Himalayan region is one of the major seismic areas in the world.However,similar to many other seismically active locations,there are substantial numbers of unreinforced masonry(URM)buildings;the majority of which have not been designed for seismic loads.Past seismic events have shown that such buildings are highly vulnerable to earthquakes.Retrofitting of these URM buildings is an important concern in earthquake mitigation programs.Most government school buildings in rural areas of northern India are constructed of unreinforced masonry.These school buildings are socially important structures and serve as a crucial resource for rehabilitation during any disaster.The effectiveness of ferrocement(FC)to create a URM-FC composite is described in this study by estimating the performance and fragility of a URM school building before and after a retrofit.Analytical models,based on the equivalent frame method,are developed and used for nonlinear static analysis to estimate the enhancement in capacity.The capacity enhancement due to retrofitting is presented in terms of the maximum PGA sustained and damage probabilities at the expected level of earthquake hazard.
文摘Unreinforced Masonry(URM) is the most common partitioning material in framed buildings in India and many other countries.Although it is well-known that under lateral loading the behavior and modes of failure of the frame buildings change significantly due to infill-frame interaction,the general design practice is to treat infills as nonstructural elements and their stiffness,strength and interaction with the frame is often ignored,primarily because of difficulties in simulation and lack of modeling guidelines in design codes.The Indian Standard,like many other national codes,does not provide explicit insight into the anticipated performance and associated vulnerability of infilled frames.This paper presents an analytical study on the seismic performance and fragility analysis of Indian code-designed RC frame buildings with and without URM infills.Infills are modeled as diagonal struts as per ASCE 41 guidelines and various modes of failure are considered.HAZUS methodology along with nonlinear static analysis is used to compare the seismic vulnerability of bare and infilled frames.The comparative study suggests that URM infills result in a significant increase in the seismic vulnerability of RC frames and their effect needs to be properly incorporated in design codes.
文摘Experimental evaluation of reinforced concrete beam specimens with different characteristics of reinforcement subjected to pushover and cyclic loading is presented.Plastic hinge rotation parameters are determined based on the idealization of pushover and hysteresis curves of reinforced concrete beam specimens constructed in two percentage of reinforcement(0.471%and 0.71%) with different ductile characteristics.The experimental test results provide a clear demarcation of the effect of types of loading and the types of reinforcement on the nonlinear performance characteristics of beam specimens.These results are helpful to update the nonlinear modeling parameters of beam components for the specific type of reinforcement used in the construction of a structure.The updated non-linear modeling parameters of beam components in lumped plasticity model are compared with the values of ASCE/SEI 41-06(2007) used for the performance based design of structures.
文摘2D finite element models were developed to analyze the effect of improved soft-soil foundation on the efficiency of a base-isolated concrete frame.Static and dynamic analyses were performed for a frame on raft foundation.Non-improved and improved soft-soil foundation using rigid inclusions were considered,as well as the use of high damping rubber bearing as base isolation.Results show that the use of rigid inclusions increases the efficiency of base isolation;base shear is reduced by 38% and maximum acceleration at the top of the frame by 30%.
文摘Tire wastes have many properties that are valuable from a geotechnical engineering perspective, such as low density, high strength, thermal insulation, energy absorption capacity, permeability, durability, compressibility, resilience, and high frictional strength. Thus, tire wastes offer good thermal characteristics in resisting frost penetration and have good drainage characteristics, being as permeable as coarse granular soil for fill materials. The many advantages of tire wastes make the material suitable for transportation infrastructure construction in cold regions. Also, tire wastes with high damping property make them a preferable admixture with sand for transportation infrastructures in seismic regions. This study aimed to determine the seismic performance of certain tire waste-sand mixtures in cold regions. A 70% sand-30% tire crumb mixture by weight(TC30) with a very high damping property was selected for analysis as an engineering material for transportation infrastructure. Small-scale shake-table tests were conducted on this material as well as on a sand-only sample under two different temperatures, 0 °C and 20 °C, to simulate cold-region and moderate-temperature performance, respectively. The 1999 ?zmit Earthquake Excitation(EW)(Mw = 7.4) was taken as the input motion. Test results showed that the tire waste-sand mixture at 0 °C showed better seismic performance than that at room temperature, suggesting that a tire waste-sand mixture in cold regions may reduce seismic hazards to infrastructure.
基金Tribhuvan University,Nepal for providing sabbatical leave and University Grants Commission(UGC),Nepal for providing financial support in the form of fellowship
文摘In the present study,the spatial-temporal distribution of b-value along the five faults area(the Judi fault,Thaple fault,Kathmandu fault,Motihari-Gauri Shanker fault,and Motihari-Everest fault)was investigated after the Gorkha earthquake(M7.8).The earthquake catalog of 10,500 events was prepared by compiling the published catalogs.The study area is bounded in the central Himalaya from 26.5°to 29°in latitude direction and 84°to 87°in longitude direction.The frequency magnitude distribution shows the variation of the b-value along with fault areas from 0.45 to 0.69,indicating a common characteristic of aftershock sequences.In particular,the Judi fault area,Thaple fault area,and Motihari-Everest fault area are characterized by the low b-values of 0.45±0.02,0.48±0.02,and 0.55±0.04,respectively.These regions could be the source region for future earthquakes.The low b-value observed for fault areas are also consistent with the thrust faulting pattern in the region as indicated by the focal mechanism of mainshock and major aftershocks.The temporal variation of b-value shows inevitable fluctuations during25 April to 12 May 2015.Among the area selected,the Motihari-Everest fault area is in critical strain(mechanically locked)conditions,as indicated by the stepwise energy release pattern.
文摘Indian Institute of Technology, Roorkee (IITR) is operating a nationwide network of instruments for recording strong ground motion. Total 300 instruments are installed in seismic zone III, IV and V along Himalayan belt. Primary goal of this project is to acquire strong ground-motion (SGM) data for various studies in the field of earthquake engineering and seismology in general and in particular to understand propagation and site response characteristics of the sediments that underlie and are thought to produce large site amplification and seismic hazard. These data will complement laboratory data to characterize the properties of the soft soils underlying residential area so that engineers and architects can design appropriate earthquake-resistant structures for the region. The successful working of this network has laid the foundation of Earthquake Early Warning System (EEW) in India. A great number of strong motion records have been obtained and utilized to study local site and geological effects. The paper introduces outline of the IITR strong motion network and some of its recent studies.
基金IIT Roorkee under the Faculty Initiation Grant No.100556
文摘With the recent development of digital Micro Electro Mechanical System(MEMS) sensors, the cost of monitoring and detecting seismic events in real time can be greatly reduced. Ability of MEMS accelerograph to record a seismic event depends upon the efficiency of triggering algorithm, apart from the sensor′s sensitivity. There are several classic triggering algorithms developed to detect seismic events, ranging from basic amplitude threshold to more sophisticated pattern recognition. Algorithms based on STA/LTA are reported to be computationally efficient for real time monitoring. In this paper, we analyzed several STA/LTA algorithms to check their efficiency and suitability using data obtained from the Quake Catcher Network(network of MEMS accelerometer stations). We found that most of the STA/LTA algorithms are suitable for use with MEMS accelerometer data to accurately detect seismic events. However, the efficiency of any particular algorithm is found to be dependent on the parameter set used(i.e., window width of STA, LTA and threshold level).
文摘Site-specific seismic hazard analysis is crucial for designing earthquake resistance structures,particularly in seismically active regions.Shear wave velocity(V_(S))is a key parameter in such analysis,although the economy and other factors restrict its direct field measurement in many cases.Various V_(S)-SPT-N correlations are routinely incorporated in seismic hazard analysis to estimate the value of V_(S).However,many uncertainties question the reliability of these estimated V_(S)values.This paper comes up with a statistical approach to take care of such uncertainties involved in V_(S)calculations.The measured SPT-N values from all the critical boreholes were converted into statistical parameters and passed through various correlations to estimate V_(S)at different depths.The effect of different soil layers in the boreholes on the V_(S)estimation was also taken into account.Further,the average shear wave velocity of the top 30 m soil coverV_(S30))is estimated after accounting for various epistemic and aleatoric uncertainties.The scattering nature of the V_(S)values estimated using different V_(S)-N correlations was reduced significantly with the application of the methodology.Study results further clearly demonstrated the potential of the approach to eliminate various uncertainties involved in the estimation of V_(S)30 using general and soil-specific correlations.
文摘The aim of this research is to assess the seismic performance of reinforced concrete columns under different axial load and transverse reinforcement ratios. These two parameters are very important as for the ductility, strength, stiffness, and energy dissipation capacity for a given reinforced concrete column. Effects of variable axial load ratio and transverse reinforcement ratio on the seismic performance of reinforced concrete columns are thoroughly analyzed. The finite element computer program Seismo-Structure was used to perform the analysis of series of reinforced concrete columns tested by the second author and other researchers. In order to reflect the reality and grasp the actual behavior of the specimens, special attention was paid to select the models for concrete, confined concrete, and steel components. Good agreements were obtained between the experimental and the analytical results either for the lateral force-drift relationships or for the damage progress prediction at different stages of the loading.
