Solid Roof Research Articles

Experimental research on load of transversal roof bracing due to geometrical imperfections of truss

The lattice or solid roof girders used in hall systems require transverse stabilization, most often realized with a transverse roof bracing and vertical bracing. The guidelines of EN 1993-1-1 for the design of the transversal roof bracing recommends considering loads resulting from geometric imperfection of the braced chord of the roof girder. According to the guidelines of EN 1993-1-1, the global imperfection of a braced chord is assumed as a bow imperfection with maximum deflection e0 (in the middle of the chord length), while the distribution of the normal force in the chord is simplified to a uniform distribution equal to the maximum compressive force NEd. On the basis of such assumptions, the load acting on the bracing from the imperfected girder is determined as a uniformly distributed load. The article presents theoretical analysis formulated by the author and the results of experimental research that contradict the standard model. The experimental results concern the nodal load acting on the transverse roof bracing and resulting from the influence of the truss girder with geometric imperfection of the compressed chord. The experimental studies were carried out on a semi-natural scale models. The article describes in detail the models and the test stand, as well as the research methodology. The obtained experimental results were compared with the results of theoretical analyses. These results confirm the differences between the standard load acting on the bracing and the real load, and confirm the conclusions resulting from the analysis of the theoretical author's model.

Remembering the Covenants in Song: An Intertextual Study of the Abrahamic and Mosaic Covenants in Psalm 105

Remembering the Covenants in Song: An Intertextual Study of the Abrahamic and Mosaic Covenants in Psalm 105

Cover Chem. Eng. Technol. 4/2016

AbstractCover: BIOGAS PILOT PLANT at the DBFZThe cover picture shows the biogas pilot plant at the DBFZ (German Biomass Research Center). This extends the range of application‐oriented research being carried out at the DBFZ to enhance process understanding and improve the efficiency of biogas production. The dimensioning of the fermenters allows experiments to be conducted on full scale, thereby ensuring good transferability of results into practice. The facility features two independent lines with identical capacity which can be operated as a single‐ or two‐stage system, with optional hydrolysis. The first line is a wet fermentation system with a main fermenter in the form of a continuous stirred tank reactor with a central agitator. The second line can optionally be run with a main fermenter of identical design or with a plug‐flow fermenter. A post‐digester with a flexible rubber gas dome collects the digestate from both lines and after post digestion, they are carried over to the digestate storage tank. The biogas is used in a 75 kWel combined heat and power unit (CHP) to cover the facility's own energy demand. Surplus power can be fed into the DBFZ grid. For substrate supply, small amounts of self‐produced silage can be stored on site. For a precise measurement of the gas production rate the primary fermenters have solid roofs. Terminal units in the pipeline system and at the gas capture point permit sampling and the installation of additional sensors.

When a Tree House No Longer Says ‘House’, Are We Virtually There?

In the spring of 2013, Akira Suzuki, the Japanese architectural critic, editor and Professor of Architecture at Musashino Art University, issued an invitation to three architects to design and self‐build a tree house for HC Andersen Park in the suburbs of Tokyo. He observes how the resulting ephemeral structures, built out of the trees themselves, invited interaction with visitors and, and were ‘less material buildings with solid roofs and walls than “conditions” or “happenings”’. He discerns that the widespread adoption of social media in Japan has resulted in a paradigm shift. This has moved creativity away from the folly, as an object of contemplation, scale‐less and position‐less on the landscape's horizon and solitary in the mind. In its place, the solitary browsing of networks is causing people to meet in actual space, which resists the easy flows of internet connectivity without imposing walls or rooms.

Smoke Management System Design for Airport Terminal

“Open Cabin” includes a solid roof which has enough fire resistance, covers over the entire region whose fire load is relatively high, such as commercial building with a large area. Performance design using “Open Cabin” concept of big space, is to protect areas whose fire load is relatively high from fire using the local fire protection measures (automatic alarm system, automatic sprinkler system, fire compartment and smoke resistance facilities), in order to make up fire protection measures which cannot be set in full range within big space. Then there is no need to separate big space physically for limiting the spread of fire and smoke.

Effects of nonlocal elasticity and slip condition on vibration of nano-plate coupled with fluid flow

Fluid–structure interaction (FSI) problem of a nano-plate under fluid flow is addressed in this article, where this nano-plate together with two rigid walls and a solid roof, is transformed to a fluid-carrying channel. We would analyze static instability (divergence) and dynamic instability for this system. To consider the effect of nano-size of the plate, the nonlocal elasticity theory and the effect of Knudsen number (Kn) in fluid boundary are used. Kn directly affects the velocity correction factor (VCF) defined as the ratio of average sliding velocity of fluid over channel wall to average no-sliding fluid velocity. Classical plate theory (CPT) and Navier–Stokes' continuum equation are used for modeling the FSI problem. The results show that nonlocal parameter could have a higher effect for liquid nano-flow than Kn, in reducing the divergence and flutter critical flow velocities. It is due to small range of variations of Kn for a liquid. Nonlocal parameter could have more effect on reducing the divergence critical liquid velocity of higher modes, specifically coupled-mode flutter. However, the results would be somewhat different from gas nano-flows. The range of variations of Kn for nano-gas flow would be higher and regarding the nonlocal parameter, the effect of Kn would be quite considerable for reducing critical gas velocities.

Qualitative Analysis of the Administrative and Managerial Capacity of Ngaka Modiri Molema District, North West Province, South Africa

This article analyses the administrative and managerial capacity of the Ngaka Modiri Molema District. It identifies two pertinent themes of a functional municipality, namely: (1) administrative viability and (2) managerial know-how, and used them as benchmarks for this analysis. Within the context of this a rticle, administration refers to an activity or work done by officials within the spectrum of local government institutions to enable different local government institutions to achieve their objectives. The activity thus includes processes such as policy-making, organising, financing, personnel provision and utilisation (staffing), determination of work procedures, and control. Management, on the other hand, has to do with the implementation of policies, formulation of procedures, establishment of performance standards, and support of administration services. Quali tative data collection methods and analysis and interpretation techniques were employed in analysing the administrative and managerial capacity of the District. The analysis established that the District was in a state of distress due to lack of administrative and managerial capacity. The findings of this analysis were that in respect of administration, the administrative structures, systems, processes, and procedures in the District were not clearly articulated. It also emerged that administrative decision-making and problem-solving skills were not well-integrated. With regard to management, it was discovered that managerial plans, policies, strategies, and tactics were not well -coordinated. Moreover, it was found that management training and empowerment programmes were not adequate to enable the District to live up to its expectations. Based on these findings, and taking the systems perspective into account, the article recommends the concrete foundation—pillar of strength—solid roof administration and management model , for transforming the District into a vibrant and functional municipality, and thus restoring the confidence of its residents.

The Tortoise and the Hut

The Tortoise and the Hut

Differences in Thermoregulatory Ability Between Slick-Haired and Wild-Type Lactating Holstein Cows in Response to Acute Heat Stress

Animals inheriting the slick hair gene have a short, sleek, and sometimes glossy coat. The objective of the present study was to determine whether slick-haired Holstein cows regulate body temperature more effectively than wild-type Holstein cows when exposed to an acute increase in heat stress. Lactating slick cows (n=10) and wild-type cows (n=10) were placed for 10h in an indoor environment with a solid roof, fans, and evaporative cooling or in an outdoor environment with shade cloth and no fans or evaporative cooling. Cows were exposed to both environments in a single reversal design. Vaginal temperature, respiration rate, surface temperature, and sweating rate were measured at 1200, 1500, 1800, and 2100h (replicate 1) or 1200 and 1500h (replicate 2), and blood samples were collected for plasma cortisol concentration. Cows in the outdoor environment had higher vaginal and surface temperatures, respiration rates, and sweating rates than cows in the indoor environment. In both environments, slick-haired cows had lower vaginal temperatures (indoor: 39.0 vs. 39.4°C; outdoor 39.6 vs. 40.2°C; SEM=0.07) and respiration rate (indoor: 67 vs. 79 breaths/min; outdoor 97 vs. 107 breaths/min; SEM=5.5) than wild-type cows and greater sweating rates in unclipped areas of skin (indoor: 57 vs. 43g.h−1/m2; outdoor 82 vs. 61g.h−1/m2; SEM=8). Clipping the hair at the site of sweating measurement eliminated the difference between slick-haired and wild-type cows. Results indicate that slick-haired Holstein cows can regulate body temperature more effectively than wild-type cows during heat stress. One reason slick-haired animals are better able to regulate body temperature is increased sweating rate.

04/02057 Influence of external surface colour on the periodic heat flow through a flat solid roof with variable thermal resistance: Granja, A. D. and Labaki, L. C. International Journal of Energy Research, 2003, 27, (8), 771–779

04/02057 Influence of external surface colour on the periodic heat flow through a flat solid roof with variable thermal resistance: Granja, A. D. and Labaki, L. C. International Journal of Energy Research, 2003, 27, (8), 771–779

Influence of external surface colour on the periodic heat flow through a flat solid roof with variable thermal resistance

In this research, the influence of external colour on the dynamics of the heat flow through a flat solid roof, with variable thermal resistance, has been studied analytically. The chromatic effect on the density of heat flow through the roof has been analysed using periodic solutions of the heat conduction equation, by means of Fourier analysis. The simulation has been carried out over a period of 24 h, for the summer design day of Campinas, in the State of São Paulo, Brazil, and its composite climate. An almost linear relationship between heat flow amplitudes (Δqi) and the thickness of a concrete roof has been noticeable in the range from 5 to 14 cm for a grey coloured exterior surface and a corresponding white one. Conversely, from 15 cm and more, this relationship starts flattening. It may be concluded that as the thermal resistance of the concrete roof increases (>15 cm), the effect of the exterior colour surface on the periodic heat transfer through the roof is attenuated. As a consequence, the conflict between choosing colour for aesthetics and assuring energy efficiency of opaque building components in hot climates can be mitigated, if building designers make proper use of thermal inertia. Copyright © 2003 John Wiley & Sons, Ltd.

Seismic evidence for a hydrothermal layer above the solid roof of the axial magma chamber at the southern East Pacific Rise

A full-waveform inversion of two-ship, wide-aperture, seismic reflection data from a ridge-crest seismic line at the southern East Pacific Rise indicates that the axial magma chamber here is about 50 m thick, is embedded within a solid roof, and has a solid floor. The 50--60-m-thick roof is overlain by a 150--200-m-thick low-velocity zone that may correspond to a fracture zone that hosts the hydrothermal circulation, and the roof itself may be the transition zone separating the magma chamber from circulating fluids. Furthermore, enhanced hydrothermal activity at the sea floor seems to be associated with a fresh supply of magma in the crust from the mantle. The presence of the solid floor indicates that at least the upper gabbros of the oceanic lower crust are formed by cooling and crystallization of melt in magma chambers.

Heat-Insulating Roofs from Date Palm Fronds

The high tensile and compression strength, low thermal conductivity, light weight, resistance to corrosion and abundance of Date Palm Fronds (DPF) were utilized in producing flat and curved roofs. Solid roofs were produced by incorporating DPF with plain concrete. Light flexible roofs were also produced by using a special non-hardening roofing material with DPF.

The Generation of Granitic Magmas by Intrusion of Basalt into Continental Crust

When basalt magmas are emplaced into continental crust, melting and generation of silicic magma can be expected. The fluid dynamical and heat transfer processes at the roof of a basaltic sill in which the wall rock melts are investigated theoretically and also experimentally using waxes and aqueous solutions. At the roof, the low density melt forms a stable melt layer with negligible mixing with the underlying hot liquid. A quantitative theory for the roof melting case has been developed. When applied to basalt sills in hot crust, the theory predicts that basalt sills of thicknesses from 10 to 1500 m require only 1 to 270 y to solidify and would form voluminous overlying layers of convecting silicic magma. For example, for a 500 m sill with a crustal melting temperature of 850 °C, the thickness of the silicic magma layer generated ranges from 300 to 1000 m for country rock temperatures from 500 to 850°C. The temperatures of the crustal melt layers at the time that the basalt solidifies are high (900–950°C) so that the process can produce magmas representing large degrees of partial fusion of the crust. Melting occurs in the solid roof and the adjacent thermal boundary layer, while at the same time there is crystallization in the convecting interior. Thus the magmas formed can be highly porphyritic. Our calculations also indicate that such magmas can contain significant proportions of restite crystals. Much of the refractory components of the crust are dissolved and then re-precipitated to form genuine igneous phenocrysts. Normally zoned plagioclase feldspar phenocrysts with discrete calcic cores are commonly observed in many granitoids and silicic volcanic rocks. Such patterns would be expected in crustal melting, where simultaneous crystallization is an inevitable consequence of the fluid dynamics. The time-scales for melting and crystallization in basalt-induced crustal melting (102−103 y) are very short compared to the lifetimes of large silicic magma systems (>106 y) or to the time-scale for thermal relaxation of the continental crust (> l07 y). Several of the features of silicic igneous systems can be explained without requiring large, high-level, long-lived magma chambers. Cycles of mafic to increasingly large volumes of silicic magma with time are commonly observed in many systems. These can be interpreted as progressive heating of the crust until the source region is partially molten and basalt can no longer penetrate. Every input of basalt triggers rapid formation of silicic magma in the source region. This magma will freeze again in time-scales of order l02−103 y unless it ascends to higher levels. Crystallization can occur in the source region during melting, and eruption of porphyritic magmas does not require a shallow magma chamber, although such chambers may develop as magma is intruded into high levels in the crust. For typical compositions of upper crustal rocks, the model predicts that dacitic volcanic rocks and granodiorite/tonalite plutons would be the dominant rock types and that these would ascend-from the source region and form magmas ranging from those with high temperature and low crystal content to those with high crystal content and a significant proportion of restite.

A Laboratory Investigation of Assimilation at the Top of a Basaltic Magma Chamber

The fluid dynamic processes affecting the mechanism and amount of assimilation of the roof of a magma chamber have been studied in a series of analogue laboratory experiments. An aqueous solution of $$Na_{2}CO_{3}$$ was first cooled and crystallized at the top of a laboratory tank to form a solid roof layer of prescribed composition. The tank was then drained and refilled with warmer solution, either $$Na_{2}CO_{3}$$ (of the same or different composition) or, in two experiments, $$KNO_{3}$$. The metal top in all cases was held below the eutectic temperature for the system $$Na_{2}CO_{3}-H_{2}O$$. The experiments were continued until substantial crystallization, and in some cases complete solidification, were achieved. Starting with a dense solid roof layer of $$Na_{2}CO_{3}10H_{2}O$$ and ice on the $$Na_{2}CO_{3}$$ side of the eutectic, and a warmer eutectic $$Na_{2}CO_{3}$$ solution below, there was rapid convective cooling of the liquid layer accompanied by melting of the roof, producing a compositionally dense liquid which convected downwards. When the roof was a solid of eutectic composition and the warm input fluid was much denser, a light stable liquid layer formed. The two liquid layers were separated by a double-diffusive interface through which heat was transported rapidly, but through which there was little mass transfer. As the lower layer cooled and crystallized at the bottom, its $$Na_{2}CO_{3}$$ concentration decreased, and the latent heat released by crystallization was transported upwards through the interface and contributed to the heat required for melting at the roof. In an experiment in which the mean compositions of the roof and the input solution were comparable, melting also led to the development of a stable upper liquid layer, as denser $$Na_{2}CO_{3}10H_{2}O$$ crystals fell off, leaving a lighter melt of eutectic composition behind. With a different denser solute ($$KNO_{3}$$) below, the system at first behaved similarly to the $$Na_{2}CO_{3}$$ experiment and produced a light roof layer, but later the densities of the two liquid layers evolved due to cooling and crystallization until they became equal, resulting in overturning and thorough mixing. The implication for a basaltic magma chamber, in which the magma produced by melting of the roof rocks is lighter than the magma below, is that the melted material will remain at the top of the chamber and be chemically isolated from the basaltic magma at the bottom. The process of AFC (assimilation with fractional crystallization) implies that the heat required for assimilation comes from the latent heat of crystallization, and that these two processes occur simultaneously in a single body of well-mixed magma. The melt released forms a light roof layer which may initially mix with some of the underlying basaltic magma, but then mixes very little. As a consequence, assimilation is separated from the crystallization in space and time. The interface between the upper and lower layers still allows rapid thermal transport vertically, so that crystallization at the floor supplies heat to assimilate the roof, but little roof material is incorporated in the lower layer as it crystallizes. At a later stage the contaminated magma at the roof crystallizes so that fractional crystallization follows assimilation, rather than the two processes occurring simultaneously from the same body of magma. True AFC is confined to the lower basaltic layer but is limited by the amount of material which can be transported across the double-diffusive interface which divides the basaltic layer from the melted roof layer. AFC does become important if large numbers of blocks of the roof fall through the upper layer and melt in the lower layer.

Spectral analysis of coal-mine roof vibrations

A study was made of the possibility of assessing coal-mine roof integrity by using audio-frequency-range spectral analysis of the vibrations produced by tapping the roof. Laboratory tests of rock slabs and field tests of mine-roof slabs showed that characteristic bending, torsional, and extensional vibration modes are excited and easily measured. Modes characteristic of a wave bouncing between the face and back of a slab spread and dissipate too rapidly to allow spectral analysis; thus, slab thickness is not measurable by this technique. Solid roofs give broadband, noise-like spectra with little low-frequency energy. “Drummy” roofs give line spectra characteristic of slab vibration modes and usually have considerable energy in the 0–400 Hz range. Spectral analysis can indicate “drummy” versus “nondrummy” but can reveal little about thickness or mounting of a roof slab and can contribute little to practical mine safety. Recommendations are made for better use of normal hearing in mine-roof testing, better protection for those doing the testing, safer mining methods, and for studies of microseismic emissions coming immediately after coal cutting.