Increasing Load Ratio Research Articles

Rheological Properties Of (NR/SBR/CMC/C.B) Nanocomposites

This research focuses on the impact of adding materials such as carbon black and polymer of carboxyl methylcellulose on the the rheological properties of styrene butadiene rubber (SBR) and natural rubber (NR) which was studied as a matrix. The present study was a carried out by two groups according to the loading level of carboxyl methylcellulose (CMC) and carbon black(C.B) its molecular weight (N660) which their used as stiffeners in the composites. on the other side, rheometer tests carried according to ASTM D 2705 For the purpose use these composites in various tire making and fender ship. All composites are consisting of carbon black (C.B) N660 (0, 10, 10, 10, 10) pphr and carboxyl methyl cellulose (CMC) (0, 0, 10, 20, 30) pphr respectively for the first group (A) and (0, 20, 20, 20, 20) pphr for C.B, (0, 0, 10, 20, 30) pphr for CMC for the second group (B). The maximum torque, minimum torque, scorch time, viscosity and Tc90 optimum curing time were checked. The results revealed that the parameters differ according to the level of loading. Viscosity, lower torque, maximum torque and optimal curing were reduced for increasing loading ratio of the C.B and CMC. As well, an optimal curing time of the TC90 burning time was reduced as addition ratios of the carbon black (C.B) and carboxyl methyl cellulose (CMC) increased.

Collapse performances of steel frames against fire considering effect of infill walls

This study numerically investigates effect of infill walls on collapse performances of three-dimensional (3D) steel frames against fire using explicit nonlinear dynamic analysis. Two eight-story, five-span with three-bay composite steel frames were designed, one of which has no infill walls (bare frame) while the other one has infill walls (infilled frame). The fire resistance, load redistribution mechanisms of the structures subjected to single compartment fire are investigated. Frame analysis against traveling fires is also conducted. Moreover, the effect of parameters including load ratio, opening percentage and number of infill walls are also studied. Results indicate that the damaged compartment moves down in fire and drags the other part of the frame, causing overturning deformation in the frame in the short span and the twist of the entire structure. The infill walls decrease the buckling temperature of the heated columns, whereas significantly increase the collapse temperature of the steel frames. The strut action of infill walls drastically changes internal forces within adjacent columns, significantly altering load redistribution path of steel frames against fire. The collapse modes of the steel frames can be greatly altered by the presences of infill walls. The steel frames collapse at a lower temperature with increasing load ratio and opening percentage of infill walls, whereas collapse at a higher temperature with more infill walls. Finally, a preliminary analytical approach is proposed to predict collapse modes of steel frames against traveling fire.

Structural and DC-electrical properties of novel PMMA-PVA nanocomposites reinforced with graphene nanosheets

Polymer-graphene nanocomposites offer interesting opportunities to enhance the properties of polymer nanocomposites. In this study, new nanocomposites with polymethyl methacrylate and polyvinyl alcohol were successfully fabricated for the first time with various loading ratios of graphene oxide nanosheets (GO), with dimethylformamide-co-distilled water used as the developing solution. Fourier-transform infrared spectroscopy (FTIR), optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and DC electrical conductivity tests were conducted to investigate the structure and DC electrical properties of the resulting PMMA-PVA/GO nanocomposites. The OM and SEM images recorded a fine homogenous matrix and good distribution of GO in the nanocomposites, while the FTIR spectra displayed functional groups of all polymers and GO in the nanocomposites, with strong interfacial interaction between GO nanosheets and polymers, as confirmed by shifts in the XRD spectra of the PMMA. The results for conductivity in the DC electrical systems showed improvement after the addition of GO. The value of DC conductivity for PMMA-PVA/GO nanocomposites was 7.86 × 10-15 per ohm-cm at a GO ratio of 0.09%, while an increase in GO loading ratio to 0.27% caused an increase in conductivity to 4.53 × 10-9 per ohm-cm. The values of the activation energy of the nanocomposites were - 6.8%, -24.8%, and -66.91% eV for 0.09%, 0.18%, and 0.27% GO, respectively. These results suggest that such inclusions could allow for the development of better and wider applications for nanocomposites, including solar cells, electrical devices, IR-windows, microwave absorption panels, and sensors.

Behaviour of ultra-high strength concrete encased steel columns subject to ISO-834 fire

Ultra-high strength concrete (UHSC) encased steel columns are receiving growing interest in high-rise buildings owing to their economic and architectural advantages. However, UHSC encased steel columns are not covered by the modern fire safety design code. A total of 14 fire tests are conducted on UHSC (120 MPa) encased steel columns under constant axial loads and exposed to ISO-834 standard fire. The effect of load ratio, slenderness, stirrup spacing, cross-section size and concrete cover to core steel on the fire resistance and failure mode of the specimens are investigated. The applicability of the tabulated method in EC4 (EN 1994-1-2-2005) and regression formula in Chinese code (DBJ/T 15-81-2011) to fire resistance of UHSC encased steel columns are checked. Generally, the test results reveal that the vertical displacement-heating time curves can be divided into two phases, i.e. thermal expansion and shortening to failure. It is found that the fire resistance of column specimens increases with the increase of the cross-section size and concrete cover to core steel, but decreases with the increase of the load ratio and slenderness. The EC4 method overestimates the fire resistance up to 186% (220 min), while the Chinese code underestimates it down to 49%. The Chinese code has a better agreement than EC4 with the test results since the former considers the effect of the load ratio, slenderness, cross section size directly in its empirical formula. To estimate the fire resistance precisely can improve the economy of structural fire design of ultra-high strength concrete encased steel columns.

The influence of the parameters of the running systems of wheeled vehicles on the change in soil density

The movement of wheeled vehicles on soils and grounds leads to a change in their density. The research includes the influence of mass and its distribution along the axes of the wheels on the change in the density of soils and grounds. The substantiation of analytical dependencies for determining the density of compacted and flowing soils and soils from repeated impacts of wheels under various loads is given. The dependence for determining the density of the soil in the general case, including compressed and fluid components of the state of the soil and soil mass, was substantiated.
 The experimental laboratory studies were carried out on the effect of wheels on the soil and the effect of wheel load on soil compaction. The dependences were obtained to determine the compaction of soil with different physical and mechanical properties under different loading modes of the running systems. It was found that the distribution of the mass of a wheeled vehicle along the axles of the wheels affects the depth of the track and the compaction of the soil. The obtained dependences for describing the process of soil compaction are consistent with the results of experiments. It was found that with an increase in the number of axles of the running system, soil compaction decreases. The minimum track depth and soil compaction are observed when the mass of the wheeled vehicle is evenly distributed along the axes of the chassis. With an increase in the number of axles, the influence of the ratio of the pressure of the first wheel to the average pressure on soil compaction decreases due to a decrease in the differential pressure of the wheels that occurs in multi-axle wheel systems. With slight deviations from the unit of the ratio of the front wheel load to the average value of the pressure, the increase in soil density is not perceptible. As the front-to-middle load ratio increases, soil compaction increases significantly compared to an even weight distribution along the axles.

Mining‐Induced Pressure‐Relief Mechanism of Coal‐Rock Mass for Different Protective Layer Mining Modes

The protective layer mining method of the traditional deep coal seam in has been confronted with great challenges, and it is difficult for coal and gas to be extracted together. Taking the occurrence conditions of III1 mining area of Luling Coal Mine located at Huaibei, China, as engineering background, the influence law of the lithology on stress environment in front of the stope was analyzed by theoretical analysis and numerical simulations. The mining‐induced mechanical effect of coal‐rock mass was studied under different protective layer mining modes. The results showed that the peak value of the advanced abutment pressure decreased with the decrease of lithologic strength under the same mining conditions. For simulated geological conditions, the stress concentration coefficient of soft rock and coal seam protective layer mining modes was 1.9 and 1.7, respectively. Under the mining stress path of different protective layers, the ratio of axial stress increase and confining pressure unloading in secondary unloading phase were 2 : 1 and 1.5 : 1, respectively. The axial stress‐strain curves of different protective layer mining modes had similar trends, and they had a volume expansion at the end of unloading (failure stage). In addition, it revealed the pressure‐relief antireflection mechanism of the protective layer mining. Under the same confining pressure condition, the peak stress and peak strain increased with the increase of loading and unloading velocity ratio. The reduced value of the confining pressure increased, while the volume expansion decreased at failure. The results were applied to III1 mining area in soft rock protective layer mining, which created the mining way of traditional coal seam protective layer. Furthermore, the gas control technology of soft rock protective layer working face was put forward for deep coal seam with low permeability and high gas, enriching the pressure‐relief mining theory of protective layer.

Structural fire safety design of square and rectangular tubed-reinforced-concrete columns

The tubed-reinforced-concrete (TRC) columns have gained increasing use in the high-rise buildings and large-span stadiums in China, whereas the structural fire design method for square and rectangular TRC columns is still missing. Finite element analysis of the fire performance of square and rectangular TRC columns was conducted using a sequentially-coupled thermo-stress model. This model yielded good predictions against the experimental results of square TRC columns. Fire tests on two rectangular TRC columns were also conducted and presented in this paper, to further calibrate the model. Parametric studies were then conducted, through which it was found that the fire resistance of square and rectangular TRC columns decreases with the increase of load ratio or slenderness ratio and increases as the sectional dimension enlarges. Sectional aspect ratio has a minor influence on the fire resistance of rectangular TRC columns. A practical design method was proposed, for the first time, to determine the fire resistance of square and rectangular TRC columns with or without fire protection. The buckling reduction coefficient could be determined by the EC3 buckling curve (c) or the JGJ/T471 buckling curve. The heat transfer equations given in the Japanese AIJ recommendation were modified to determine the temperatures of the steel tube and rebars and equations were proposed to determine the equivalent temperatures of the concrete core.

Experimental study and numerical simulation analysis of the fire resistance of high-strength steel columns with rectangular sections under axial compression

Based on the performance of Q550 (yield strength fy = 550 MPa) high-strength steel, mechanical property tests at room temperature and elevated temperatures were first carried out. Second, fire tests were carried out on 8 unconstrained Q550 high-strength steel columns with rectangular sections under axial compression. The mechanical properties and failure modes of high-strength steel columns under fire exposure were revealed. Finally, ABAQUS finite element software was used to establish a refined finite element model of high-strength steel columns, and numerical simulation analysis was carried out to analyse the influence of various parameters on the fire resistance. The results show that (1) the critical temperature and the maximum axial displacement of the steel columns decrease with increasing load ratio n. (2) the smaller the slenderness ratio λ is, the smaller the maximum axial displacement, while the critical temperature changes slightly. (3) there are two failure modes of the specimens: overall buckling and overall and local coupling buckling. (4) the thermal mechanical coupling analysis method can effectively simulate the behaviour of high-strength steel columns under fire exposure. The research in this paper establishes a theoretical foundation for the improvement of the fire resistance design method of high-strength steel columns.

Damage analysis of sandstone during the creep stage under the different levels of uniaxial stress using NMR measurements

AbstractIn this paper, the nuclear magnetic resonance (NMR) measurements are carried out to evaluate the micro‐cracking characteristics of sandstones during the creep stage under the different levels of creep stresses. The variations in the parameters, including transverse relaxation time (T2) spectra distribution, percentage of the pore distribution, incremental value of porosity and ultrasonic P wave velocity are analysed. The results show that, during the creep stage, small pores in the rocks gradually evolve into large pores, resulting in an increase in damage of rocks. With the increase of the loading ratio, the increasing rate of porosity increases sharply, implying that the damage degree becomes more serious under the high loading ratio. When the loading ratio is larger than 0.7, the increasing rate of porosity and the decreasing rate of the P wave velocity both increases rapidly. During the creep stage, the relationship between micro‐crack and macro‐creep characteristics of rocks is established based on the analysis of the deformation and the porosity evolution during creep. It is found that, as the loading ratio increases, the increasing rate of porosity is linear with the creep strain. The NMR method offers a feasible option to identify micro‐cracking process of rocks during the creep stage, which can directly reflect the damage mechanism of rock caused by creep. The porosity of rocks is an effective parameter to evaluate the damage of rocks. The damage evolution of the specimen is highly anisotropic and is heavily related to the loading ratio during the creep stage. The relationship between the damage parameter and the loading ratio is exponential.

Experimental and numerical investigations on seismic performance of RC bridge piers considering buckling and low-cycle fatigue of high-strength steel bars

In order to promote the application of high-strength steel bars (HSSB) in reinforced concrete (RC) bridge structures, the mechanical properties of HSSB as well as seismic performance of high-strength RC piers were investigated by experimental study and numerical analysis. First, monotonic and low cycle fatigue tests of HRB400E and HTRB600 steel with different slenderness ratios (L/D) were conducted to comparatively study their mechanical properties. Then, quasi-static cyclic tests of seven rectangular RC piers were conducted to study the effects of concrete cover, longitudinal reinforcement yield strength, concrete strength and axial load ratio on seismic behavior of RC piers. Finally, a fiber-based beam-column element was used to simulate the mechanical behavior of steel material and nonlinear response of RC piers. Material tests indicate that HTRB600 steel has lower uniform and fracture elongations, as well as inferior low-cycle fatigue performance than HRB400E steel. Increase of the slenderness ratio (L/D) severely weakens low-cycle fatigue life of steel bars, and the low-cycle fatigue parameters of steel can be fitted for each slenderness ratio, respectively. Even though HTRB600 steel has relatively lower ductility and inferior low-cycle fatigue performance, the RC piers with HTRB600 steel still have higher or at least comparable deformation capacity than that with HRB400E steel. This results from the reduction of strain demands of longitudinal bars by the utilization of HSSB in RC piers. Removing the concrete cover neighboring the longitudinal bars in the plastic hinge region has trivial impact on bar buckling and ultimate displacement of RC piers, which confirms that the concrete cover has already spalled off prior to the initiation of longitudinal reinforcement buckling. With identical steel strength and tie configuration, the ultimate displacement of RC pier with C80 concrete is significantly lower than that with C40 and C60 concrete, while the latter two have similar deformation capacity. Increase of axial load ratio (from 0.06 to 0.18) obviously reduces ultimate displacement of RC piers, since the concrete in the compression zone endures greater compressive stress under higher axial load and thus compressive failure occurs earlier. The ReinforcingSteel material model in OpenSees is calibrated by experimental data to accurately simulate the buckling and low-cycle fatigue properties of HRB400E and HTRB600 steel. The fiber-based finite element model (FEM) can predict the strain development of longitudinal bars of RC piers under cyclic loading, and the resulting low-cycle fatigue damage of steel material as well as strength degradation of RC piers. Combined with experimental study and FEM, this paper reveals the influence mechanisms of different factors on the seismic performance of RC piers in detail.

Catalytic pyrolysis of distilled lemon grass over Ni-Al based oxides supported on MCM-41

ABSTRACT In order to disposal the herb residue of Chinese medicine which is easy to decay and harmful to the environment. The residue of lemon grass after extraction (distilled lemon grass, DLG), as an herb residue of Chinese medicine, was pyrolyzed to obtain bio-oil in this study for high-value utilization. Noncatalytic pyrolysis were firstly carried out under nitrogen, ammonia and methanol atmospheres respectively. Methanol atmosphere and a moderate temperature of 450°C were determined as the proper pyrolysis conditions according to the experimental results. Then, catalytic pyrolysis was conducted over Ni-Al layered double oxide/MCM-41 (NiAl-LDO/MCM-41) composites. The results showed that NiAl-LDO/MCM-41 with NiAl-LDO load ratio of 20% increased the yield of bio-oil by ~15% compared to the noncatalytic process and simultaneously changed the composition of the bio-oil. The content of nonaromatic oxygen-containing compounds decreased and the content of aromatic compounds could reach more than 90%. Moreover, the contents of aromatic hydrocarbons and aromatic oxygenous compounds in the bio-oil changed with the increase in NiAl-LDO load ratio. This study showed that pyrolysis of DLG under methanol atmosphere over NiAl-LDO/MCM-41 could obtain a large amount of high value-added chemicals, especially aromatic compounds, which could be expected to become an important way for the utilization of residue of Chinese medicine.

Prospective surveillance for intussusception in Indian children aged under two years at nineteen tertiary care hospitals

BackgroundIndia introduced rotavirus vaccines (RVV, monovalent, Rotavac™ and pentavalent, Rotasiil™) in April 2016 with 6, 10 and 14 weeks schedule and expanded countrywide in phases. We describe the epidemiology of intussusception among children aged 2–23 months in India.MethodsThe prospective surveillance at 19 nationally representative sentinel hospitals from four regions recruited children with intussusception from April 2016 to September 2017. Data on sociodemography, immunization, clinical, treatment and outcome were collected. Along with descriptive analysis, key parameters between four regions were compared using Chi-Square/Fisher’s exact/Mann–Whitney U/Kruskal-Wallis tests. The pre- and post-RVV periods were compared to estimate the risk ratios.ResultsSix hundred twenty-one children with intussusception from South (n = 262), East (n = 190), North (n = 136) and West (n = 33) regions were recruited. Majority (n = 465, 74.8%) were infants (40.0% aged 4–7 months) with median age 8 months (IQR 5, 13 months), predominantly males (n = 408, 65.7%) and half (n = 311, 50.0%) occurred during March–June months. A shorter interval between weaning and intussusception was observed for ragi based food (median 1 month, IQR 0–4.2 months) compared to rice (median 4 months, IQR 1–9 months) and wheat (median 3 months, IQR 1–7 months) based food (p < 0.01). Abdominal pain or excessive crying (82.8%), vomiting (72.6%), and bloody stool (58.1%) were the leading symptoms. Classical triad (abdominal pain, vomiting and bloody stool) was observed in 34.8% cases (24.4 to 45.8% across regions). 95.3% of the cases were diagnosed by ultrasound. 49.3% (10.5 to 82.4% across regions) cases were managed by reduction, 39.5% (11.5 to 71.1% across regions) cases underwent surgery and 11.1% spontaneously resolved. Eleven (1.8%) cases died. 89.1% cases met Brighton criteria level 1 and 7.6% met Level 2. RVV was received by 12 cases within 1–21 days prior to intussusception. No increase in case load (RR = 0.44; 95% CI 0.22–1.18) or case ratio (RR = 0.5; 95% CI 0.3–1.2) was observed after RVV introduction in select sites.ConclusionsIntussusception cases were observed across all sites, although there were variations in cases, presentation and mode of management. The high case load age coincided with age of the RVV third dose. The association with ragi based weaning food in intussusception needs further evaluation.

Numerical analysis on fire performance of steel-reinforced concrete-filled steel tubular columns with square cross-section

This paper presents a study on the fire performance of steel-reinforced concrete-filled steel tubular (SRCFST) columns with square cross-section. The numerical models of SRCFST members, including a heat transfer analysis model and a structural analysis model, are established by ABAQUS to simulate the fire performance. The numerical models are validated against with the experimental data reported previously in terms of temperature field, axial deformation versus time curves, fire resistance and failure modes, and acceptable agreement can be achieved. Sensitivity analyses on contact thermal resistance and transient thermal strain are performed. It can be found that considering transient thermal strain of concrete and thermal resistance across the interface of concrete and steel tube is more realistic and gives accurate assessment for FE models. The fire performances of SRCFST columns, including temperature distributions, the axial deformation-time (Δ-t) curves, axial force distribution and strain are investigated and compared with common CFST columns. The results show that the fire behaviour of SRCFST columns can be further enhanced owing to the embedded profiled steel. Finally, the influences of various parameters on fire resistance, including fire load ratio, material strength, steel tube ratio, profiled steel ratio and slenderness ratio are examined. It is found that a higher profiled steel ratio is more favourable to fire resistance of SRCFST columns assuming the total steel ratio same, and the fire resistance significantly decreases with the increase of fire load ratio and slenderness ratio.

New analytical solutions for shallow cohesive soils overlying trench voids under various slip surfaces

This paper investigates the effects of cover ratio and soil strength parameters (cohesion and friction angle) on the failure mechanisms of cohesive soils overlying trench voids using trapdoor technique. Adaptive finite element limit analyses (AFELA) were conducted to study the failure mechanisms of trapdoors covered with soils of different thicknesses, cohesions and friction angles. It was found that slip surfaces in the cover soil could be in the shape of vertical, trapezoid, spiral or arching, depending on the combination of soil strength parameters and cover ratio. Analytical solutions under various slip surfaces, considering major principal stress trajectories to describe load transfer paths, were further proposed to study the load transfer mechanisms in shallowly embedded trapdoors. The solutions in terms of arching ratios and lateral earth pressure coefficients were validated against the results of previously reported laboratory tests and AFELA. The results show that the modified earth pressure coefficient is greater than 1.0 due to the consideration of the major principal stress trajectory. The vertical stresses acting on trapdoors are in an inverted parabolic distribution, which are lower in the middle. The arching ratio decreases with increasing soil cohesion, friction angle and cover ratio. For cohesionless soils, the arching ratio decreases as the surcharge loading ratio increases, but for cohesive soils, the arching ratio increases with increasing surcharge loading ratios.

Improvement of mechanical and physical performance of poly (lactic acid) biocomposites by application of surface silanization for huntite–hydromagnesite mineral

Silanization process was applied to huntite–hydromagnesite (HH) mineral in for improve its adhesion to poly (lactic acid) (PLA) matrix. Surfaces of HH samples were examined by infrared spectroscopy and energy-dispersive X-ray spectroscopy analysis. HH was compounded with PLA using melt-blending technique. Modified HH incorporations led to nearly 19% and 20% increase in tensile strength and modulus of PLA, respectively. The maximum improvement for tensile strength value is obtained for 15 wt% of modified HH containing composite sample. On the other hand, percentage strain of PLA decreases nearly 22% with the addition of HH. Silane-modified HH-containing composites yield higher impact energy compared to untreated HH. Impact performance of composites increases nearly 18% with the increase in loading ratio of HH. Silane-modified HH displays higher storage modulus than HH, and glass transition temperature of PLA shifts to higher levels with the inclusion of HH. HH-filled composites exhibit no significant difference with melt flow rate value of PLA. Water resistance of silane-treated HH-containing composites are found to be higher than untreated HH attribitued to hydrophobicity of silicon-rich surface. Accordingly, composites that include modified HH are suitable for outdoor applications. Morphological investigations confirm that dispersion homogeneity and strong adhesion are achieved due to the improvement of surface interactions between HH and PLA phases after silane treatment process.

Experimental and numerical studies on axially restrained cold-formed steel built-up box columns at elevated temperatures

Experimental and numerical studies on the fire resistance of cold-formed steel (CFS) columns with built-up box-shape sections were conducted in this paper. A series of coupon tensile tests were also performed before the fire resistance tests of the columns to obtain the stress–strain relationship of the steel plate from 20 °C to 800 °C. As a benchmark, the load-bearing capacity tests of the columns at ambient temperature were conducted first, and then the fire resistance tests were performed for eight specimens considering different load ratios and axial restraining stiffness. Afterward, numerical models, including heat transfer and structural analyses, were developed to reproduce the fire-resistance behavior of the columns and verified via test results. Finally, parametric analyses were performed to investigate the influence of load ratio, axial restraint, and rotational restraint on the fire-resistance behavior of the columns. Results indicated that the primary failure mode of the specimens was a combination of local and global flexural buckling, which was sensitive to the longitudinally non-uniform temperature field. Moreover, the increase in load ratio and axial restraining stiffness led to a significant decrease in the critical temperature and failure time. Moreover, even a low level of rotational restraint could enhance the fire-resistance behavior of the column.

Behavior of thread-fixed one-side bolted T-stubs with backing plates at ambient and elevated temperatures

The tension behavior of Thread-fixed One-side Bolts (TOB) connected T-stubs at ambient and high temperatures was studied experimentally and theoretically. The anchorage force to TOB was provided by the threads on the bolt hole wall which was usually restrained by the limited thickness of the steel plate. The thread length and bending strength of the T-stub flange could be increased by adding backing plates. Two failure modes appeared in ambient temperature tests, which were completely flange yielding and flange yielding accompanied with threads failure. Both steady-state method and transient-state method were used in high temperature test. Test results showed that failure modes might be changed at high temperatures. However, the unfavorable threads failure did not appear at high temperatures which showed the good applicability of TOB. Backing plate was proved to be an effective way to strengthen the TOB connected T-stubs. Tension resistance and initial stiffness of strengthened T-stubs increased obviously while still keeping good ductility in both ambient and high-temperature circumstance. In transient-state test, the increase in load ratio would make the connection more fragile. The failure temperature and failure displacement decreased correspondingly. Design equations for predicting the failure mode and the tension strength of TOB connected T-stubs at high temperatures were proposed, considering effects of large deformation of the T-stub flange at high temperatures. Comparison with test results showed that the proposed design equations could precisely predict the failure mode and the yielding tension strength of strengthened or unstrengthened TOB connected T-stubs at both ambient and high temperatures.

Temperature and moisture effect on laminated rhombic hyperbolic paraboloid

The current work presents a hygrothermal analysis of laminated composite rhombic hyperbolic paraboloids. The cubic variation in displacement field together with cross curvature effects of the shell were used to solve the hygrothermal problem. Because of the parabolic variation of the transverse shear deformation, the shear correction factor was not necessary in this paper. In the mathematical model, the zero conditions of the transverse shear stress at the bottom and top of the shell were applied. The nine-noded curved isoparametric element with seven unknowns in each node was used to implement the present realistic mathematical model. The implementation of the finite element C0 (FE) of the present mathematical model was coded and performed in FORTRAN. The skew hyperbolic paraboloid on which the hygrothermal analysis was conducted had various temperatures, ply orientation, curvatures, moisture concentration, boundary conditions and thickness ratio. The paper shows that with the increase of the skew angle, the non-dimensional deflection decreases, and with the increase of moisture concentration, hygrothermal load and curvature ratio, the deflection increases. The results of the model presented in the paper were compared with other results published in the literature and were found to be consistent with them.

Post-fire seismic performance of SRC beam to SRC column frames

This paper investigates the post-fire seismic performance of steel reinforced concrete (SRC) beam to SRC column frames. Five SRC column to SRC beam planar frame specimens were tested in a program including a loaded fire test and a following horizontal cyclic loading test. Test parameters included heating time and column load ratio. The temperature development, deformation, post-fire hysteretic and skeleton curves, stiffness, ductility and damping coefficient of SRC frames are recorded, calculated and analyzed. The measured post-fire hysteretic curves indicates that the SRC frames exhibit very good energy dissipation capacity after fire exposure. The horizontal load capacity and viscous damping coefficient of SRC frames increase with the increase of column load ratio. However, column load ratio has an adverse influence on ductility as anticipated at normal temperature. One SRC frame specimen failed during the cooling phase, which demonstrates the importance of considering the cooling phase during the fire safety design.

Impact of Electrification and Particle Loading on Velocity Profile of Dusty Fluid Flow Over a Stretching Sheet

The performance of incompressible, laminar, boundary- layer flows over a semi-infinite horizontal stretchable plate is considered. The dusty fluid flow problems are modelled and solved in agreement with two-way coupling model. The particle phase momentum equation in the vertical direction is considered where as that for fluid phase is neglected. Here the electrification term added in not from the supply from outside rather it is the generation due to collision of particles So the effects of particle loading and electrification on velocity profile have been studied. From the result analysis it is concluded that electrification and particle density have significant effect on particle phase velocity, whereas carrier fluid phase has negligible effect. The particle phase velocity increases with increasing of electrification parameter and decreases with increase of loading ratio.