Open Ground Storey（OGS） framed buildings where the ground storey is kept open without infill walls, mainly to facilitate parking, is increasing commonly in urban areas. However, vulnerability of this type of buildin...Open Ground Storey（OGS） framed buildings where the ground storey is kept open without infill walls, mainly to facilitate parking, is increasing commonly in urban areas. However, vulnerability of this type of buildings has been exposed in past earthquakes. OGS buildings are conventionally designed by a bare frame analysis that ignores the stiffness of the infill walls present in the upper storeys, but doing so underestimates the inter-storey drift（ISD） and thereby the force demand in the ground storey columns. Therefore, a multiplication factor（MF） is introduced in various international codes to estimate the design forces（bending moments and shear forces） in the ground storey columns. This study focuses on the seismic performance of typical OGS buildings designed by means of MFs. The probabilistic seismic demand models, fragility curves, reliability and cost indices for various frame models including bare frames and fully infilled frames are developed. It is found that the MF scheme suggested by the Israel code is better than other international codes in terms of reliability and cost.展开更多
Due to rapid construction,necessity for raw materials of concrete,especially coarse aggregate,tends to increase the danger of early exhaustion of the natural resources.An alternative source of raw materials would perh...Due to rapid construction,necessity for raw materials of concrete,especially coarse aggregate,tends to increase the danger of early exhaustion of the natural resources.An alternative source of raw materials would perhaps delay the advent of this early exhaustion.Recycled coarse aggregate(RCA)plays a great role as an alternative raw material that can replace the natural coarse aggregate(NCA)for concrete.Previous studies show that the properties of RCA concrete are inferior in quality compared to NCA concrete.This article attempts to study the improvement of properties of RCA concrete with the addition of bacteria named as Bacillus subtilis.The experimental inves-tigation was carried out to evaluate the improvement of the compres-sive strength,capillary water absorption,and drying shrinkage of RCA concrete incorporating bacteria.The compressive strength of RCA concrete is found to be increased by about 20%when the cell con-centration of B.subtilis is 10^(6) cells/ml.The capillary water absorptionas well as drying shrinkage of RCA are reduced when bacteria is incorpo-rated.The improvement of RCA concrete is confirmed to be due to the calcium carbonate precipitation as observed from the microstructure studies carried out on it such as EDX,SEM,and XRD.展开更多
Ureolytic-type bacteria has been used to improve the strength of cement mortar by the precipitation of calcium carbonate.In the present study Bacillus sphaericus has been used to improve the properties of cement morta...Ureolytic-type bacteria has been used to improve the strength of cement mortar by the precipitation of calcium carbonate.In the present study Bacillus sphaericus has been used to improve the properties of cement mortar such as setting time,compressive strength and sorptivity.The setting time is found to be unaffected by the presence of bacteria.It is found that compressive strength at both 7-days and 28-days of mortar cube increases with the increase of bacteria concentration.At the optimum bacteria dosage of 107 cells/ml,the average compressive strength increases by 58%(at 7 day)and 23%(at 28 day)over the control specimen.The sorpitivity coefficient decreases as the concentration of bac-terial cells increases.The mineralogy and morphology of the cal-cium carbonate precipitation have been tested by XRD and FESEM.展开更多
Proven research output on the behavior of structures made of waste copper slag concrete can improve its utilization in the construction industry and thereby help to develop a sustainable built environment.Although num...Proven research output on the behavior of structures made of waste copper slag concrete can improve its utilization in the construction industry and thereby help to develop a sustainable built environment.Although numerous studies on waste copper slag concrete can be found in the published literature,no research has focused on the structural application of this type of concrete.In particular,the variability in the strength properties of waste copper slag concrete,which is required for various structural applications,such as limit state design formulation,reliability-based structural analysis,etc.,has so far not attracted the attention of researchers.This paper quantifies the uncertainty associated with the compressive-,flexural-and split tensile strength of hardened concrete with different dosages of waste copper slag as fine aggregate.Best-fit probability distribution models are proposed based on statistical analyses of strength data generated from laboratory experiments.In addition,the paper presents a reliability-based seismic risk assessment of a typical waste copper slag incorporated reinforced concrete framed building,considering the proposed distribution model.The results show that waste copper slag can be safely used for seismic resistant structures as it results in an identical probability of failure and dispersion in the drift demand when compared with a conventional concrete building made of natural sand.展开更多
文摘Open Ground Storey（OGS） framed buildings where the ground storey is kept open without infill walls, mainly to facilitate parking, is increasing commonly in urban areas. However, vulnerability of this type of buildings has been exposed in past earthquakes. OGS buildings are conventionally designed by a bare frame analysis that ignores the stiffness of the infill walls present in the upper storeys, but doing so underestimates the inter-storey drift（ISD） and thereby the force demand in the ground storey columns. Therefore, a multiplication factor（MF） is introduced in various international codes to estimate the design forces（bending moments and shear forces） in the ground storey columns. This study focuses on the seismic performance of typical OGS buildings designed by means of MFs. The probabilistic seismic demand models, fragility curves, reliability and cost indices for various frame models including bare frames and fully infilled frames are developed. It is found that the MF scheme suggested by the Israel code is better than other international codes in terms of reliability and cost.
文摘Due to rapid construction,necessity for raw materials of concrete,especially coarse aggregate,tends to increase the danger of early exhaustion of the natural resources.An alternative source of raw materials would perhaps delay the advent of this early exhaustion.Recycled coarse aggregate(RCA)plays a great role as an alternative raw material that can replace the natural coarse aggregate(NCA)for concrete.Previous studies show that the properties of RCA concrete are inferior in quality compared to NCA concrete.This article attempts to study the improvement of properties of RCA concrete with the addition of bacteria named as Bacillus subtilis.The experimental inves-tigation was carried out to evaluate the improvement of the compres-sive strength,capillary water absorption,and drying shrinkage of RCA concrete incorporating bacteria.The compressive strength of RCA concrete is found to be increased by about 20%when the cell con-centration of B.subtilis is 10^(6) cells/ml.The capillary water absorptionas well as drying shrinkage of RCA are reduced when bacteria is incorpo-rated.The improvement of RCA concrete is confirmed to be due to the calcium carbonate precipitation as observed from the microstructure studies carried out on it such as EDX,SEM,and XRD.
文摘Ureolytic-type bacteria has been used to improve the strength of cement mortar by the precipitation of calcium carbonate.In the present study Bacillus sphaericus has been used to improve the properties of cement mortar such as setting time,compressive strength and sorptivity.The setting time is found to be unaffected by the presence of bacteria.It is found that compressive strength at both 7-days and 28-days of mortar cube increases with the increase of bacteria concentration.At the optimum bacteria dosage of 107 cells/ml,the average compressive strength increases by 58%(at 7 day)and 23%(at 28 day)over the control specimen.The sorpitivity coefficient decreases as the concentration of bac-terial cells increases.The mineralogy and morphology of the cal-cium carbonate precipitation have been tested by XRD and FESEM.
文摘Proven research output on the behavior of structures made of waste copper slag concrete can improve its utilization in the construction industry and thereby help to develop a sustainable built environment.Although numerous studies on waste copper slag concrete can be found in the published literature,no research has focused on the structural application of this type of concrete.In particular,the variability in the strength properties of waste copper slag concrete,which is required for various structural applications,such as limit state design formulation,reliability-based structural analysis,etc.,has so far not attracted the attention of researchers.This paper quantifies the uncertainty associated with the compressive-,flexural-and split tensile strength of hardened concrete with different dosages of waste copper slag as fine aggregate.Best-fit probability distribution models are proposed based on statistical analyses of strength data generated from laboratory experiments.In addition,the paper presents a reliability-based seismic risk assessment of a typical waste copper slag incorporated reinforced concrete framed building,considering the proposed distribution model.The results show that waste copper slag can be safely used for seismic resistant structures as it results in an identical probability of failure and dispersion in the drift demand when compared with a conventional concrete building made of natural sand.
