Drift Index Research Articles

Geochemical identification of the source and environment of produced water from CBM wells and its productivity significance: examples from typical CBM wells in eastern Yunnan and western Guizhou

The geochemical information of produced water from coalbed methane (CBM) wells is abundant in geological significance. Based on the conventional ions, hydrogen and oxygen isotopes (δD and δ18O) and trace element tests of 27 produced water samples from CBM wells, the geochemical identification of the source and environment of produced water from CBM wells and its productivity significance have been analysed. The following conclusions have been drawn: CBM produced water can be divided into three categories, namely, polluted water from frac fluids, polluted surface water and formation water. The formation water has low Cl- concentration, low total dissolved solids (TDS) concentration, and light δD and δ18O. The water polluted by frac fluid has high Cl- and TDS concentrationt, and heavy δD and δ18O. The polluted surface water has high SO42- and light δD and δ18O. CBM groun dwate r environments can be divided into confined and unconfined systems. The confined system is characterized by low Na+/Cl- value, high (Cl- - Na+)/Mg2+ value, a general absence of SO42-, high Sr and Ba and low F. The unconfined system is characterized by high Na+/Cl- value, low (Cl- - Na+)/Mg2+ value, low SO42-, low Sr and Ba and high F. Constructing a cross plot with the new D drift index (d') value and Cl- concentration can further identify four types of source-water environments: an unconfined formation water system, an unconfined surface water system, a confined system heavily polluted by frac fluids, and a confined system only slightly polluted by frac fluids. The unconfined system often produces more formation water and has high CBM production. The confined system often produces water more heavily polluted by frac fluids and is low in CBM production. The fitting formulas of hydrochemical productivity have been established for daily CBM and water production of CBM wells.

Fragility Analysis of Infilled Reinforced Concrete Frames Subjected to Near-Field Ground Motions

The present paper deals with the analytical investigation of representative planar masonry-infilled reinforced concrete (MIRC) frames for seismic fragility, performance and demand. The study includes the effect of various patterns of layout for infills panels along the height of reinforced concrete frames. The analytical investigation has been done using non-linear dynamic time-history analysis under collection of forty SAC near-field ground motions using rational hysteretic models for structural components; the results are presented in terms of parameters such as peak inter-storey drift, residual drift and damage index. The outcomes of study are used to develop seismic fragility curves in probabilistic terms for the generic medium-rise MIRC frames. The developed fragility curves can be useful tools in predicting the life and economic losses in the future seismic event. In the current study, efforts are also made to develop curves demonstrating seismic performance and seismic demand for representative MIRC frames.

Applications of hysteretic steel dampers for controlling the seismic damage in steel frames

The aim of seismic design is not intended to make earthquake-proof structures that will not experience any damage even during a strong earthquake; such structures will be too costly. However, controlling the damage to the desired level is a necessity for buildings with a particular purpose such as hospital, fire and police station, nuclear facilities, buildings that contain hazardous material, and other building that is critical for emergencies and defense. In this paper, a four-story steel frame, both with and without hysteretic steel damper are investigated in order to account the effect of stiffness ratio, and SR (ratio between steel damper and braces stiffness to the bare frame stiffness) in the global structural damage. For these purposes, three ground motions which are compatible to the design spectrum response in the Indonesian building code were selected to be applied to the structure with a stiffness ratio (SR) of 2, 3, 4 and 5 using a non-linear dynamic time history analysis. In this context, the damage index based on the works of Park and Ang is used as the criteria to define global structural damage, while story drift index is used as the criteria to measure the seismic performance level. The results demonstrated that the use of steel damper not only enhances the seismic performance, but it also reduces the damage index of the investigated structure. Furthermore, the damage index and story drift index are influenced by the stiffness ratio, in which the stiffness ratio of 4 (four) provides the smallest damage index and inter-story drift index. Moreover, the damage index and inter-story drift index were also affected by ground motions characteristics.

Not-so-working Memory: Drift in Functional Magnetic Resonance Imaging Pattern Representations during Maintenance Predicts Errors in a Visual Working Memory Task.

Working memory (WM) is critical to many aspects of cognition, but it frequently fails. Much WM research has focused on capacity limits, but even for single, simple features, the fidelity of individual representations is limited. Why is this? One possibility is that, because of neural noise and interference, neural representations do not remain stable across a WM delay, nor do they simply decay, but instead, they may "drift" over time to a new, less accurate state. We tested this hypothesis in a functional magnetic resonance imaging study of a match/nonmatch WM recognition task for a single item with a single critical feature: orientation. We developed a novel pattern-based index of "representational drift" to characterize ongoing changes in brain activity patterns throughout the WM maintenance period, and we were successfully able to predict performance on the match/nonmatch recognition task using this representational drift index. Specifically, in trials where the target and probe stimuli matched, participants incorrectly reported more nonmatches when their activity patterns drifted away from the target. In trials where the target and probe did not match, participants incorrectly reported more matches when their activity patterns drifted toward the probe. On the basis of these results, we contend that neural noise does not cause WM errors merely by degrading representations and increasing random guessing; instead, one means by which noise introduces errors is by pushing WM representations away from the target and toward other meaningful (yet incorrect) configurations. Thus, we demonstrate that behaviorally meaningful drift within representation space can be indexed by neuroimaging.

Influencing factors research and performance experiment on droplets deposition at low wind speed

 In view of the droplet drift during aerial spraying, a droplet deposition distribution measurement system was designed to determine the droplet size under different spray pressures using LURMARK-04F80 nozzle. Wind tunnel was used to simulate the natural wind by generating fixed-speed wind. According to the international standard (ISO/FDIS 22856:2008), nozzle was installed at0.6m above the wind tunnel bottom. Deposition drift was assessed by adding fluorescent tracer to the spray mixture and measuring the quantities of droplet deposition on the PE Twines which were installed perpendicular to the wind direction in a vertical and a horizontal array. At2m distant from the static nozzle at downwind direction and0.1m above the wind tunnel bottom, five PE Twines are positioned vertically one above the other at interval of0.1m and seven PE Twines are positioned horizontally one above the other at interval of1m. By analyzing the drift index at different positions, the influences of spray angle, nozzle angle, side wind and spray pressure on the droplet drift were studied. Experimental results show that drift index on the line decreases as vertical and/or horizontal distance increase. Spray pressure and wind speed have great influence on the drift parameter. Droplets drift still exists at7m distant from the nozzle when spray pressure attains 0.4 MPa. Wind speed attains3m/s and spray angle is 0° or wind speed attains5m/s. Spray pressure attains 0.3 MPa and spray angle is 0°. The drift index in the vertical and the horizontal direction when the spray angle is 0° is higher than that of the other spray angles. When spray distance attains4m and nozzle angle attains 0°, the drift index is higher than that of the other nozzle angles. To reduce the droplet drift when the wind speed attains5m/s, spray operation creating droplet size should be adopted and the spray angle should be adjusted. This study provides optimized operation parameter for aerial nozzle and plays a vital role in reducing droplet drift. Keywords: wind tunnel, spray atomization, droplet deposition, drift index, nozzle, spray angle, nozzle angle DOI:  10.33440/j.ijpaa.20190201.0017  Citation: Ding S M, Xue X Y, Qin W C, Gu W, Cai C, Cui L F.  Influencing factors research and performance experiment on droplets deposition at low wind speed.  Int J Precis Agric Aviat, 2019; 2(1): 46–51.

Shell Roof of Tall Buildings in Earthquake Zones

This paper studies and analyzes tall buildings with shell and flat roof responses designed for gravity and earthquake loads in different zones having different soil profiles. These tall buildings having two different heights and different configurations are simulated with different load combinations. The responses of the simulated structural models with flat and shell roofs are studied and analyzed. These responses draw recommendations and guidelines for preliminary design of structurally efficient and reliable tall buildings with shell roof in earthquake zones. Five different earthquake zone factors (Z1 - Z5) along with the five different soil profiles (S1 - S5) are selected in this study. The non-linear dynamic response of buildings was obtained using three simulated models of buildings; square/rectangular, circular, and tube-shaped building. Total of 12 building models, four under each category, are analyzed using the finite element software (STAAD pro) subjected to the gravity as well as earthquake loading defined by UBC and IBC codes. Each building model is analyzed with two different story heights; which are 120 meters for 30 stories and 72 meters for 18 stories respectively. Horizontal and vertical displacement comparison is made among the flat roof and shell roof building for 32 and 18 stories building satisfying the ACI code of design requirement and drift index of 1/500 (0.002). The results showed that the drift index value for all the studied buildings is close to 0.002. All the maximum horizontal and vertical deflections occur under the earthquake zone-5 (0.40 gravitational acceleration) with soil profile-5 (Soft soil). The shell roof slab with less thickness than the flat roof slab did satisfy the horizontal and vertical deflection limits, therefore, it is more economical than the flat roof slab.

Evaluation of behavior and performance of the braced/ unbraced four story of steel frame with semi rigid connection

Structural analysis and design with taken into account the flexibility of the beam to the column connections of steel frameworks takes on importance of the growing development and utilization of new commercial software. However, for design purposes, the beam to the column connection are usually considered to be either pinned or fully rigid, and drastically simplifies the analysis and design procedures. In this paper, a four story of unbraced and concentric braced steel moment resisting frame having different connection stiffness is analysed using linear and nonlinear static procedure. In the finite element modelling, the semi rigid connection is modelled by rotational spring having linear moment and rotation relationship. To account the inelastic behaviour of beam and column members, concentrated plastic hinges based on FEMA 356 are applied for both ends of the member. It was found that, the response quantity of the unbraced frame are influenced by the flexibility connection. However, for the braced frame the effect of the initial connection stiffness parameter on the response quantity can be neglected due to present of the braces. Furthermore, the higher the initial connection stiffness parameter, the smallest the story drift index. Moreover, the present of the braces at the moment resisting frame (braced frame) reduce the sensitivity of the connection stiffness on the behaviour and the performance frame under consideration.

Seismic Performance Assessment of Existing RC Frames with Different Ultimate Concrete Strains

In recent years, because of the older version code, inadequate design, lacks of construction supervision, change in loading pattern, damages and casualties of earthquakes or environmental degradation, buildings at risk need to be investigated frequently for safety purpose. To increase the strength and ductility capacities of deficient reinforced concrete (RC) beams, columns and beam-column joints, retrofitting may require. In this paper, a numerical investigation using nonlinear static pushover analysis is conducted to assess the seismic behavior of existing moment resisting RC frames. In numerical modeling, different plastic hinge lengths as well as different concrete ultimate strain conditions of RC members are considered. Pushover analysis has been carried out with the commercial software ETABS v.9.6.0 to evaluate structural behavior of RC frames located in a seismic region. Hinge properties simulating moment-rotation behavior of frame members considering different plastic hinge lengths as well as concrete ultimate strains are evaluated. Pushover curves are compared with each other to determine the plastic hinge length and strain values which provide better agreement with that of the default properties. Seismic performance criteria in terms of ductility, overstrength as well as response modification factor for frames are determined from pushover curves. From the analyses in general, the load carrying capacity as well as displacement at maximum lateral load and interstory drift index at any floor level of RC frames is assessed.

Application of Hidden Markov Model for avalanche danger simulations for road sectors in North-West Himalaya

Hidden Markov Model (HMM) has been developed for avalanche warning on 10 different road sectors in Pir-Panjal and Great Himalayan mountain ranges of North-West Himalaya. The model uses a data set of nine snow and meteorological variables—average air temperature, snow temperature index, snow drift index, snowfall in 24 h, snowfall in 48 h, snow water equivalent, snowfall intensity, standing snow and snowpack settlement collected during past 20 winters (1992–2012). The HMM is composed of four observations derived from the model input variables and four state variables. The state variables of the model are four levels of avalanche danger (No, Low, Medium and High). Single HMM has been developed to provide avalanche warning for both direct and delayed/wet avalanches with a lead time of two days. The HMM has been validated with (Case-1) and without (Case-2) incorporating delayed/wet avalanches using data collected during four winters (2012–2016) and compared with official Avalanche Warning Bulletin issued by Snow and Avalanche Study Establishment during these winters. The model has been validated through computation of accuracy measures such as percent correct (PC), bias, false alarm rate, probability of detection and Heidke Skill Score. The PC of the HMM for different stations for Case-1 varies from 80.1 to 98.6% for day-1 and 81.2 to 98.3% for day-2 and that for Case-2 from 82.2 to 98.6% for day-1 and 83.3 to 98.3% for day-2.

Performance-based optimisation of RC frames with friction wall dampers using a low-cost optimisation method

Friction-based dampers can be considered as one of the suitable passive control systems for seismic strengthening and rehabilitation of existing substandard structures due to their high adjustability and good energy dissipation capability. One of the main issues in the design of these systems is to obtain the magnitude of the maximum slip force and the distribution of slip forces along the height of the building. In this study, a practical performance-based optimisation methodology is developed for seismic design of RC frame buildings with friction energy dissipation devices, which allows for an accurate solution at low computational cost. The proposed method aims at distributing the slip loads of the friction dampers to achieve a uniform distribution of damage along the height of the building. The efficiency of the method is evaluated through the optimum design of five different low to high-rise RC frames equipped with friction wall dampers under six natural and six synthetic spectrum-compatible earthquakes. Sensitivity analyses are performed to assess the reliability of the method using different initial height-wise slip load distributions, convergence parameters and earthquake records. The results indicate that optimum frames exhibit less maximum inter-storey drift (up to 43%) and global damage index (up to 75%), compared to uniform slip load distribution. The method is then developed to obtain the optimum design solution for a set of earthquakes representing a design spectrum. It is shown that the proposed method can provide an efficient tool for optimum seismic design of RC structures with friction energy dissipation devices for practical purposes.

Effects of Ground Motion Directionality on the Seismic Behavior of Mid-rise Concrete Buildings with Considering Unequal Live-Load Distribution in Height

The incident angle of ground motion is one of the sources of uncertainty in the seismic response of buildings. Moreover, understanding the structural response to the impose ground motion may cause significant changes in the maximum response of buildings. In order to investigate the influence of the spatial distribution of orthogonal components of earthquake strong motion on the structural responses, three 15-story buildings were analyzed in this study using the time-history method. A significant live load (750 kg/m2) is imposed at different vertical levels of the structures. The imposed load was combined with ground motion excitations in the range of 0 to 90 degrees. The response of structure was investigated using roof drift index and inter-story drift ratio. Results demonstrate the orientation of seismic excitation and considering the maximum values of roof drift index, which correspond to the critical direction increase roof drift index between 8 to 12 percent. Furthermore, the inter-story drift ratio increased between 30 to 33 percent due to the orientation of excitation and considering the maximum values of the inter-story drift ratio, which correspond to the critical direction.

Comparison of vertical E × B drift velocities and ground-based magnetometer observations of DELTA H in the low latitude under geomagnetically disturbed conditions

In the present work, we analyzed the daytime vertical E×B drift velocities obtained from Jicamarca Unattended Long-term Ionosphere Atmosphere (JULIA) radar and ΔH component of geomagnetic field measured as the difference between the magnitudes of the horizontal (H) components between two magnetometers deployed at two different locations Jicamarca, and Piura in Peru for 22 geomagnetically disturbed events in which either SC has occurred or Dstmax<−50nT during the period 2006–2011. The ΔH component of geomagnetic field is measured as the differences in the magnitudes of horizontal H component between magnetometer placed directly on the magnetic equator and one displaced 6–9° away. It will provide a direct measure of the daytime electrojet current, due to the eastward electric field. This will in turn gives the magnitude of vertical E×B drift velocity in the F region. A positive correlation exists between peak values of daytime vertical E×B drift velocity and peak value of ΔH for the three consecutive days of the events. It was observed that 45% of the events have daytime vertical E×B drift velocity peak in the magnitude range 10–20m/s and 20–30m/s and 20% have peak ΔH in the magnitude range 50–60nT and 80–90nT. It was observed that the time of occurrence of the peak value of both the vertical E×B drift velocity and the ΔH have a maximum (40%) probability in the same time range 11:00–13:00 LT. We also investigated the correlation between E×B drift velocity and Dst index and the correlation between delta H and Dst index. A strong positive correlation is found between E×B drift and Dst index as well as between delta H and Dst Index. Three different techniques of data analysis – linear, polynomial (order 2), and polynomial (order 3) regression analysis were considered. The regression parameters in all the three cases were calculated using the Least Square Method (LSM), using the daytime vertical E×B drift velocity and ΔH. A formula was developed which indicates the relationship between daytime vertical E×B drift velocity and ΔH, for the disturbed periods. The E×B drift velocity was then evaluated using the formulae thus found for the three regression analysis and validated for the ‘disturbed periods’ of 3 selected events. The E×B drift velocities estimated by the three regression analysis have a fairly good agreement with JULIA radar observed values under different seasons and solar activity conditions. Root Mean Square (RMS) errors calculated for each case suggest that polynomial (order 3) regression analysis provides a better agreement with the observations from among the three.

COMPARATIVE STUDY OF BRACING SYSTEMS FOR IRREGULAR TALL STEEL STRUCTURES BASED IN DIFFERENT CITIES

In a high-rise steel building, bracing system is an essential commodity for inadequate lateral reinforcements in the structure. Therefore, bracing system is a necessary solution for these lateral deflections caused by lateral loads. The resistance to wind and seismic load is one of the factor for the sustainability of the high rise building. For present study, plan irregularity with (A/L) ratio of (40/65) = 0.62 is considered as per IS 1893 (Part 1): 2002. In this study, the steel structure is assumed to be at 4 different cities with different seismic zones those cities are Agra, Bengaluru, Mumbai and Roorkee with five types of bracing systems. All cities are compared with an unbraced model of Roorkee city. A G+14 structure is analyzed for seismic zone II, zone III and zone IV as per IS: 1893-2002 using STAAD pro software. Dead and live loads are sustained by beams and columns whereas; the lateral loads are carried by bracing systems only. The bracings are provided at every corner of the structure. The structure is studied for nodal displacements in X-direction and Z direction in all the floors, axial force and bending moment for the ground level column is compared and finally, drift index and corresponding percentage change in top roof is calculated.

Load Distribution Patterns for Displacement-based Seismic Design of RC Framed Buildings

The behaviour of tall frames is characterized by the influence of higher modes in addition to the fundamental mode and thus the design procedures for Displacement-based Design (DBD) adopt several measures to control higher mode effects. The performances of 4, 9 and 15-storeyed frames, designed by DBD were verified using non-linear time history analyses. Higher values of inter-storey drift and damage index were seen near the top of tall frames, which shows the inefficiency of the design method in accounting for higher mode effect. As the principle of damage-limiting aseismic design is to get uniform damage along the height of the frame, several load distribution patterns were examined and the storey shear distributions were compared to identify the best pattern to get uniform damage. The Chao load distribution was found to give higher storey shear at top and thus the frames were redesigned using this load distribution. The efficiency of Chao load distribution in reducing higher mode effects is demonstrated using non-linear time history analyses.

Structural behavior of conventional and buckling restrained braced frames subjected to near-field ground motions

In this study, nonlinear dynamic analyses were performed in order to evaluate and compare the structural response of different type of moment resisting frame buildings equipped with conventional braces (CBs) and buckling restrained braces (BRBs) subjected to near-field ground motions. For this, the case study frames, namely, ordinary moment-resisting frame (OMRF) and special moment-resisting frame (SMRF) having two equal bays of 6 m and a total height of 20 m were utilized. Then, CBs and BRBs were inserted in the bays of the existing frames. As a brace pattern, diagonal type with different configurations were used for the braced frame structures. For the earthquake excitation, artificial pulses equivalent to Northridge and Kobe earthquake records were taken into account. The results in terms of the inter-story drift index, global damage index, base shear, top shear, damage index, and plastification were discussed. The analysis of the results indicated a considerable improvement in the structural performance of the existing frames with the inclusion of conventional and especially buckling-restrained braces.

Modified Gutenberg–Richter Coefficient for Damage Evaluation in Reinforced Concrete Structures Subjected to Seismic Simulations on a Shaking Table

This paper presents analysis and discussion of the $$b$$ - and ib-values calculated from the acoustic emission (AE) signals recorded during dynamic shake-table tests conducted on a reinforced concrete (RC) frame subjected to several uniaxial seismic simulations of increasing intensity until collapse. The intensity of shaking was controlled by the peak acceleration applied to the shake-table in each seismic simulation, and it ranged from 0.08 to 0.47 times the acceleration of gravity. The numerous spurious signals not related to concrete damage that inevitably contaminate AE measurements obtained from complex dynamic shake-table tests were properly filtered with an RMS filter and the use of guard sensors. Comparing the $$b$$ - and ib-values calculated through the tests with the actual level of macro-cracking and damage observed during testing, it was concluded that the limit value of 0.05 proposed in previous research to determine the onset of macro-cracks should be revised in the case of earthquake-type dynamic loading. Finally, the $$b$$ - and ib-values were compared with the damage endured by the RC frame evaluated both visually and quantitatively in terms of the inter-story drift index.

Comparative Response Assessment of Different Frames with Diagonal Bracings Under Lateral Loading

In this study, nonlinear static and dynamic analyses were performed to compare the structural response of different types of moment-resisting frame buildings equipped with concentric diagonal braces under lateral loading. For this purpose, the existing moment-resisting frames designed according to two different stiffness levels were used as case studies. They were referred to as (a) flexible moment-resisting frames (MRF) and (b) rigid MRFs. The buildings having 4, 8, 12, and 16 storeys consist of the same plan and three bays on both directions. Then, concentric steel braces were inserted in the middle bay of each frame. For the braced frame structures, diagonal type configuration was utilized. Capacity curve, inter-storey drift index, global damage index, variation of storey displacements with height, roof displacement time history, and plastification in the frame members were evaluated for all frame systems. The results exhibited a substantial improvement in the earthquake performance of the frames with the incorporation of concentric diagonal braces, depending on the storey height and especially stiffness level of the frame.

Wind Loads on a Medium-Rise Building by Using Five Major International Wind Codes and Standards

Wind load calculations are done for a medium-rise building with 48 m height locates in an urban area of Sri Lanka. Five different international wind loading standards were selected to calculate wind loads according to prevailing conditions in Sri Lanka. Available 3 second gust wind speed is converted in to mean hourly wind speed and 10 minutes average wind speed to use selected wind loading standards. The difference of wind load calculations is evaluated by using member forces in columns, beams, and shear walls obtained from a 3–D finite element modelling. The comparison displays that both the Australian standards yields higher wind loads compared to other selected standards. The use of higher terrain-height multiplier for cyclone prone zone 1 contributes much larger member forces compared to other cases. None of the standards exceeds the serviceability criteria, which evaluate by means of drift index. ENGINEER, Vol. 47, No. 01, pp. 25-35, 2014

Investigation of Correlations between Seismic Parameters and Damage Indices for Earthquakes of Iran Region

Seismic record of an earthquake contains important and significant data about characteristics of a ground motion. In this study, interdependencies between important seismic parameters and three overall structural damage indices including the Bracci index, the modified flexural damage ratio (MFDR) index and the drift index were determined for several records of earthquakes occurred in Iran. Calculations were done for medium rise concrete frame structures. In next step, seismic parameters that had strongest and weakest interdependencies with three mentioned damage indices were determined by the Spearman and Pearson correlation coefficients. As the final value of damage indices cannot show the process of member degradation, time variations in the Powell and Allahabadi model were calculated to give a good insight into the behavior of structural members during earthquake.

DISEÑO BASADO EN DESPLAZAMIENTOS DE ESTRUCTURAS ESENCIALES

Mediante el uso de sistemas equivalentes de un grado de libertad, se evalúa la pertinencia del uso que actualmente se da al factor de importancia durante el diseño sísmico de estructuras esenciales desplantadas en terreno blando. Dada la alta vulnerabilidad que a partir de sus demandas de distorsión muestran algunos de estos sistemas, se propone una metodología de diseño basada endesplazamientos para la concepción de sistemas estructurales que sean capaces de controlar adecuadamente los niveles de daño estructural y no estructural en instalaciones esenciales. La metodología es aplicable a edificios estructurados con base en marcos rígidos (también conocidos como continuos) y contempla la acción de eventos sísmicos intensos. Para mantener los niveles de daño estructural y no estructural dentro de niveles admisibles, se plantea el control simultáneo de las demandas máximas de rotación plástica y de distorsión de entrepiso. Los ejemplos que se presentan muestran que el uso de la metodología resulta en estructuras esenciales capaces de satisfacer el nivel de desempeño de Ocupación Inmediata ante la ocurrencia del sismo de diseño.