Plastic energy evaluation of bilinear SDOF systems with fluid viscous dampers

Current seismic practices are more concerned with dissipating a significant portion of seismic input energy than with lateral load resistance, as well as with determining seismic demands of structures using response spectra. This study aims to improve the knowledge of the plastic energy spectra ( $E_P$) of single-degree-of-freedom systems (SDOF) equipped with fluid viscous dampers (FVDs). This type of dampers is characterized by its supplemental damping ratio ${\xi }_{\mathit{add}}$ and velocity power $\alpha$. Using nonlinear dynamic analyses, the $E_P$ and its ratio to the input energy ( $E_P/E_I$) are determined using near-field-pulse, near-field-non-pulse and far-field ground motions. Parametric studies are conducted to investigate the effect of ground motion types, original system features and FVD characteristics on $E_P/E_I$ spectra. The results show that ground motion types have a considerable influence on the $E_P/E_I$ for systems with FVDs, while they are not effective for systems without FVDs. Increasing FVD nonlinearity (decreasing α) is more effective to reduce the $E_P/E_I$ under near-field-non-pulse and far-field motions than under near-field-pulse ground motions for structures with $T_n$ > 1 s. The paper further developed a prediction equation for estimating $E_P/E_I$for SDOF systems without and with FVDs, which can serve as a useful tool to analyse structural damage for energy-based seismic design.     

Hybrid rubber-concrete isolation slab system with various shape factors for structures subjected to horizontal and vertical vibrations

The present framework proposed the development of a Hybrid Rubber-Concrete Isolation Slab System (HRCISS) to support building structures subjected to horizontal and vertical vibration due to ground motion and machine or equipment operation in the structure. Given that the effect of the shape factor on both horizontal and vertical stiffness has yet to be reported, the proposed composite system was comprised of two layers under the nodal points of the upper layer near the slab corners with four High Damping Rubber (HDR) components positioned between the slab layers to dissipate multidirectional (horizontal and vertical directions) vibrations. The ABAQUS software was utilized to model the finite element model (FEM) and simulate the HRCISS subjected to cyclic horizontal and vertical displacements. For the optimal HDR design, the model was applied in five 3-story buildings, and the effect of distinct shape factors (0 $<$ S $<$ 2) of the HDR bearings—the ratio of bearing's loaded area to unloaded area (free to bulge)—within the hybrid system was evaluated. For each building with a specific HDR shape factor, the HRCISS was installed in the first, second, and third stories, separately, to investigate the influence of the installation level of the isolation system on the overall structural performance. The multistory buildings were subjected to two types of vibration loads: the interior machine-induced vibrations, and the exterior seismic-induced vibrations in the horizontal and vertical directions. Based on the results, the FEM results proved the significant influence of the shape factors on the dynamic response of the HRCISS under both interior and exterior 3D vibrations when applied in multistory buildings. The lateral drift of the three-story one-bay buildings decreased with the decrement of shape factor with buildings of HRCISS installed in 1st story recording more reduction. Moreover, the deflection in the structural slab under the HRCISS decreased for lower shape factor bearings. Nevertheless, the reduced deflection was less affected by the level of the machine-equipped story. The rubber layer also stiffened in shear and compression directions with a higher shape factor.     

Special all-round fillet weld for anchor rods of base-plate T-stub connections

The eccentricity between connected steel parts and the anchor rods in base-plate T-stub connections makes base plates the weaker components in tension and compression. Additionally, the oversized holes in base plates lead to irregular placement of anchor rods, resulting in an unsymmetrical shear behavior. Thus, this paper aims to develop a special all-round fillet weld to connect the anchor rods beneath the base plate concentrically to the steel part, removing the base plate from the load-transferring chain. Accordingly, design criteria were first developed based on Eurocode's directional method considering all the potential failure modes. Next, results were validated by conducting experimental work. The digital image correlation technique (DIC) was also used to capture the strain distribution developed over the tested specimen till failure. Consequently, numerical analysis was carried out to investigate the fracture strength and the fracture angle and compare the special fillet weld with its equivalent standard one, which has the same weld volume. The results indicated that the proposed design criteria produced safe strength prediction for the developed special all-round fillet weld. Furthermore, the results revealed that using a special all-round fillet weld instead of the equivalent standard one can increase the strength by about 8% and improve the ductility of the weld. However, it decreases the stiffness of the weld by about 21%. The fracture surface occurred at $15°$ from the face of the anchor rod, which produced a higher strength than the predicted tensile strength calculated according to the theoretical throat plane.     

A study of external mass transfer effect on biodegradation of phenol using low‐density polyethylene immobilized Bacillus flexus GS1 IIT (BHU) in a packed bed bioreactor

The impact of external mass transport on the biodegradation rate of phenol in a packed bed bioreactor (PBBR) was studied. A potential bacterial species, Bacillus flexus GS1 IIT (BHU), was isolated from the petroleum‐contaminated soil. Low‐density polyethylene (LDPE) immobilized with the B. flexus GS1 IIT (BHU) was used as packing material in the PBBR. The PBBR was operated by varying the inlet feed flow rate from 4 to 10 mL/min, and the corresponding degradation rate coefficients were found to be in the range of 0.119–0.157 L/g h. In addition, the highest removal rate of phenol was obtained to be 1.305 mg/g h at an inlet feed rate of 10 mL/min. The external mass transfer was studied using the model . A new empirical correlation for the biodegradation of phenol in the PBBR was developed after the evaluation at various values of K and n.     

Research on a personalized targeted air supply device based on body movement capture

Unlike general ventilation, personalized ventilation can improve thermal comfort and conserve energy based on individual differences. It can also provide every individual the ability to control fresh air exposure and ensure good indoor air quality. However, determining how to improve air supply efficiency while avoiding a draft sensation is still a difficult question. This paper introduces a body movement-based personalized targeted air supply device. Two indices, size target value and velocity target value , are introduced to evaluate the degree to which the created flow field reaches the desired level. Additionally, the air supply effect of the device is compared with that of other devices. This research shows that the personalized targeted air supply device can successfully deliver air to the target area and improve air supply accessibility in the target area. The multinozzle coupling air supply mode produces a flow field air velocity of approximately 0.3 m/s, thus effectively avoiding a draft sensation. Compared with that of other personalized nozzles, the energy consumption is reduced significantly, by 88.2%, while the air supply accessibility can be increased by 48% with equivalent energy consumption.     

The impact of urban street layout on local atmospheric environment

The investigation was carried out to reveal the impact of urban street layout on local atmospheric environment through computational fluid dynamics (CFD) numerical simulations using standard k$k$–ε$\epsilon$ turbulence model. Different street canyon configurations are considered and the flow regimes summarized according to the aspect ratio of the leeward building height and the street width H1/W$H1/W$ and the aspect ratio of the leeward building height and the windward building height H1/H2$H1/H2$. Three regimes are defined to denote the vortices and characteristics of pollutant dispersion in street canyons according to the parameters H1/W$H1/W$ and H1/H2$H1/H2$. It is found that the pollutant transport and diffusion is strongly dependent upon the type of flow regime inside the canyon and exchange between canyon and the above roof air. The study indicated that there is a strong influence of the street layout on the wind field and the pollutant dispersion in the street canyon mainly depends on the vortex structure in the canyon. The results are validated against an extensive wind tunnel experimental (Meroney and Rafailidis) [Journal of Wind Engineering and Industrial Aerodynamics, 1996;62:37–56; http://www.mi.uni-hamburg.de] and the simulated results concluded by Sini [Atmospheric Environment 1996;30:2659–77] and Sang [Atmospheric Environment 2002;36:1137–45].     

A field study on determination of preferences for windows in office environments

We aimed to determine the preferences for windows in office spaces and discover the underlying reasons which may affect design decisions. We conducted a field study on office buildings in Izmir–Turkiye. The research findings indicated that majority of users (48.6%; n=107$n=107$) have preferred firstly window-wall, which has the largest window area, secondly horizontal window (35%; n=77$n=77$) and thirdly square window types (10.9%; n=24$n=24$) for their own workspaces. Although having equal surface areas in the preference scale, square-shaped windows have been preferred much more than the rectangular and round shaped ones and horizontal shaped windows than the vertical ones. The window type, gender, quality of office job and quality of view created significant differences in determining prior factors behind window preferences.     

Effect of porous hedge on cross ventilation of a residential building

Examined here are the effects of cross-ventilation when a porous hedge is placed ahead of a residential building. Parametric studies include the hedge porosity (0?η?1.0)$(0?\eta ?1.0)$, the space between the hedge and the building (0.25?L/2H?3.0)$(0.25?\mathrm{L}/2\mathrm{H}?3.0)$ and the hedge height (0.1?h/2H?1.0)$(0.1?\mathrm{h}/2\mathrm{H}?1.0)$. A computational fluid dynamics (CFD) simulation is carried out to predict the airflow characteristics around both the porous hedge and the building. Results show that the porous hedge could modify the flow structures behind it, and thus can alter the cross ventilation of the building. In addition, the shelter effect of the porous hedge is increased when the hedge porosity is decreased. It is also discovered that there exists a critical hedge porosity below which the cross ventilation in the building becomes inverse.     

Interaction between the mixing and displacement modes in a naturally ventilated enclosure

Experiments are carried out to study for the first time interactive phenomena in buoyancy-induced natural ventilation in a full-scale enclosure with upper and lower openings on one of the sidewalls. The interaction between the mixing and the displacement ventilation modes is revealed by opening the lower vent to different heights while the upper vent is kept fully open. Both the transient process and steady state interaction are explored. Measurements include temperature differences between inside and outside and air velocity through the upper opening. The level of the neutral plane at the upper vent, defined here as the plane separating between inflow and outflow, decreases with R^*$R^{*}$, the ratio between the opening heights (and areas) of the lower and upper vents. Experiments show that when 0*<0.27$0<R^{*}<0.27$ the mixing and displacement modes interact through a new combined ventilation mode. For 0.53*?1$0.53<R^{*}?1$, the displacement mode dominates whereas in the intermediate range, 0.27?R^*?0.53$0.27?R^{*}?0.53$, either the combined or the pure displacement mode takes place. The experiments are in qualitative agreement with a previous theoretical model.     

Numerical analysis of the street canyon thermal conductance to improve urban design and climate

Built environment is increasingly dependent on the scientific knowledge which integrates urban design and climate. In the work presented here, the canyon thermal conductance which quantifies the heat transported outside of a canyon street, is analyzed to improve on understanding of how to accomplish this integration. A two-dimensional, steady, k$k$–ε$\epsilon$ turbulence model is used to study the influence of a windward heated wall on the air flow circulation in a street canyon with building height-to-street width ratio (aspect ratio) from 0.7 to 1.5. The numerical results presented here suggest that the air flow regime is strongly affected by buoyancy and three configurations are predicted: (I) and (II) with high Froude numbers (≈10¹$\approx {10}^1$) result in one or two stable counter-rotating vortices, with an intenser upper vortex; air flow regime (III), with low Froude numbers (≈10^-1$\approx {10}^{-1}$), is dominated by the lower vortex whose intensity is enhanced by a strong upward current close to the heated surface confining the upper vortex to a strict leeward zone of the canyon. Transitional Froude numbers are found as a function of canyon aspect ratio for transitions between regimes. The relevance of the results for urban design are quantified and analyzed in terms of canyon thermal conductance. The main conclusion is that, for one vortex skimming air flow regime, the canyon thermal conductance linearly increases with wind intensity, being larger streets more exposed to thermal losses. Multiple vortices in the air flow regime significantly decrease the canyon thermal conductance and, therefore, narrow streets provide protection from heat losses on windy and cloudy days and nights.     

Determination of user profile at city parks: A sample from Turkey

A survey study conducted randomly in the cities of Erzurum, Erzincan and Kars included 360 subjects interviewed face to face. It was aimed to detect the subjective features of the participants such as gender, marital status, age, educational status and income level and the reflections of these features on the city parks. Conclusively, it was determined that those who are male, unmarried, at the age of between 19 and 24, university graduate and with a monthly income of 65–125 USD use the parks in majority. In the statistical analysis, the SPSS software was used and variables were compared. Chi-square (χ²) test was used to determine the independency correlations. According to the analysis, gender and income had no significant effect on the use of city parks, but marital status, age and education status had significant effects at 5% significance levels (*p<0.05$p<0.05$, χ²: 27.805; *p<0.05$p<0.05$, χ²: 44.073; *p<0.05$p<0.05$, χ²: 39.998, respectively).     

Removal of endosulfan in a sequencing batch reactor: addition of granular activated carbon as improvement strategy

A granular activated carbon‐sequencing batch reactor (GAC‐SBR) was used to assess the removal of organochlorine endosulfan pesticide. The reactor operated in three stages: (I) starter and stabilization; (II) addition of 4 mg/L of endosulfan in feed; and (III) a single addition of 1 g/L of GAC to mixed liquor. During the 249 days of operation, the removal efficiency of COD was 96 ± 2%; for ‐N 72 ± 1%; and for PO₄^?3‐P 48 ± 13%. Was eliminated the 79% of endosulfan in stage II and 99% in stage III, not found its metabolite (endosulfan sulphate) in the reactor effluent. A consortium of eight bacterial strains was identified in the reactor stages, assessing five of them in the presence of 4 mg endosulfan/L by growth kinetics. According to the results, the joint action of the consortium and GAC addition is the responsible of eliminating the pesticide.     

Scale model study of airflow performance in a ceiling slot-ventilated enclosure: Non-isothermal condition

Scale-model study of a non-isothermal ceiling slot-ventilated enclosure was investigated in both airspeed and thermal fields. Results of airflow pattern, centerline velocity and centerline temperature decay, velocity and temperature profile, airflow boundary layer and thermal boundary layer growth, floor velocity, and floor temperature difference were analyzed to establish semi-empirical prediction equations. Results also compared with previous researches to validate the physical behavior of air-jet. Data of centerline velocity decay showed similar airflow characteristics as isothermal air-jet with Archimedes number (Ar)<0.004$(\mathit{Ar})<0.004$, which performed as pseudo-isothermal airflow. Air-jet fell on entry with Ar>0.018$\mathit{Ar}>0.018$. A single circulation airflow existed at 0.004<Ar<0.011$0.004<\mathit{Ar}<0.011$ and two-circulation airflow occurred at 0.011<Ar<0.018$0.011<\mathit{Ar}<0.018$. The centerline velocity decay was fitted well as similar form of an isothermal condition. The centerline temperature decay was fitted well as the form of centerline velocity decay in both ceiling and floor regions. Both the velocity and temperature profiles agreed with results obtained from literature. Both airflow boundary layer and thermal boundary layer growths increased with traveling distance of air-jet. Maximum floor velocity and floor temperature difference were fitted well with different parameters. Analysis of airflow performance in a non-isothermal condition makes progress in predicting air quality inside the enclosures and guides the design concepts of ventilation system for an indoor environment.     

Simultaneous microbial removal of carbon,nitrogen, and phosphorus in a modified anaerobic/aerobic (A/O) bioreactor with no phosphorus release

A modified anaerobic/aerobic (A/O) bioreactor that simultaneously removed carbon, nitrogen ( ‐N) and phosphorus ( ‐P) was continuously run and debugged. After 34 days of reactor operation, the removal efficiencies of ‐N, carbon (glucose) and ‐P reached 99.26, 95.81 and 94.35%, respectively. Notably, the ammonium removal with no accumulation of nitrite ( ‐N) and nitrate ( ‐N) in the anaerobic part supported the occurrence of simultaneous nitrification and denitrification and no ‐P was released during the removal process of phosphorus. Moreover, the principal component analysis and response surface methodology based on the Box–Behnken design were applied to determine the optimal removal conditions for volatile suspended solids (VSS) (335 mg/L), ‐N (60 mg/L), glucose (900 mg/L) and pH (7). Finally, phylogenetic analysis of the bacterial consortium was conducted by denaturing gradient gel electrophoresis, which demonstrated that Clostridium and Proteobacteria were the potential functional groups in the anaerobic tank of the A/O bioreactor.     

Exergoeconomic analysis and optimization of a solar-assisted heating system for residential buildings

In this study, an exergoeconomic model was developed for analysis and optimization of solar heating systems with residential buildings. The optimum collector area (_Ac$A_{\mathrm{c}}$) and storage volume (V$V$) for solar-assisted heating system in the Elaz??, Turkey (38.7^°N)$(38.7^{°}\mathrm{N})$, weather conditions were obtained using MATLAB optimization toolbox. The energy and exergy losses in each of the components of a solar heating system with seasonal storage were also determined. The results showed that the exergy loss and total cost increased with increasing per house collector area for the trapeze and cylindirical tanks. It was found that the total cost of the cylindrical tank system was higher than that of the other trapeze tank system. The exergy loss at the cylindrical tank was 19.8%, while the exergy loss at the trapeze tank was 8.3%.     

The effects of road salt application on the accumulation and speciation of cations and anions in an urban environment

This study aimed to assess the quality of road runoff in heavy traffic and residential areas of Hamedan province, in the western region of Iran. To investigate the effects of salt pollution, 14 runoff samples were collected from streets during the winter and spring of 2009. Streets received different amounts of deicing salt depending on the traffic density. Results showed that deicing salt has major affects on sodium (Na⁺), calcium (Ca²⁺), magnesium (Mg²⁺), chloride (Cl^?), bicarbonate (), sulfate () and phosphate () pollution. This is important because this type of watercourse contamination can lead to serious problems, such as eutrophication. We also found an increase in lead (Pb²⁺) concentration, which was not attributable to the application of deicing agents, but that was due to the combustion of leaded gasoline. Speciation of Ca, Mg, Pb and P chemical species in the samples was calculated using Visual Minteq 2.6 program. The results indicated that Ca and Mg were mainly present as free ions, Pb was mainly present as PbCO₃ (aq), while the dominant P species were and .