Core Layouts Research Articles

Space Efficiency of Tall Buildings in Singapore

Space efficiency in Singaporean tall buildings results from a complex interplay of historical, architectural, engineering, technological, socioeconomic, and environmental factors. The city-state’s innovative and adaptive approach has enabled it to overcome the challenges associated with skyscraper construction, leading to the development of some of the most advanced and sustainable high-rise structures in the world. However, there is currently a lack of detailed analysis on space utilization in Singaporean high-rise buildings. This study addresses this gap by examining 63 cases. The main findings of this research: 1. Residential functions, central core layouts, and prismatic shapes are the most frequent. 2. Concrete material with a shear-walled frame system is the preferred structural choice. 3. Average spatial efficiency is 80%, and the core-to-GFA (Gross Floor Area) ratio averages 17%. These metrics vary from a minimum of 68% and 5% to a maximum of 91% and 32%, respectively. These insights offer valuable guidance for Singaporean construction professionals, particularly architects, helping them make informed design decisions for high-rise projects.

Space efficiency in timber office buildings

Timber offices indicate a growing field, principally thanks to their potential to offer noteworthy ecological and financial gains over their entire life. Like many other building types, space efficiency is a crucial design parameter in timber structures to ensure a project's feasibility. This factor is especially significant in office buildings, where maximizing rental income reflects effective planning. Currently, there is a lack of exhaustive inquiry providing a thorough insight of space efficiency in modern timber office buildings. This study fills this gap in the literature by collecting data from 33 buildings through literature reviews and case study method to investigate space efficiency with the key architectural and structural factors that influence it. The results showed that: (i) central cores stood out as the prevailing core layouts, while peripheral arrangements were noted as alternative preferences. Prismatic shapes emerged as the most favored options; (ii) timber was extensively used as a primary building material, closely followed by combinations of timber and concrete. Load-bearing systems mainly relied on shear walled frames and configurations; (iii) average space utilization across examined cases was 88 %, with variances ranging from 75 % to 95 % among different instances; (iv) average ratio of core area to GFA was 10 %, showing variations between 4 % and 19 % across various scenarios; and (v) there were no substantial variances noted in the effect of different core planning strategies on spatial efficiency. Similar conclusions were drawn regarding building forms and structural materials. Our paper will assist in crafting design principles customized for diverse stakeholders, including architectural designers of timber offices.

Anticipated transients without scram in an innovative power nuclear reactor of anomalously high power

The article considers the possibility of creating a safe power reactor of anomalously high power. This may be relevant in the transition to large-scale safe and environmentally acceptable nuclear power. The safety justification is carried out based on mathematical modeling of the most dangerous emergency modes from among ATWS (anticipated transients without scram). With the use of a number of innovations (the UN-PuN-U cermets fuel used, a coolant based on lead with a high concentration of the 208Pb isotope, and tungsten fuel cladding), it was possible to ensure the safety of a fast reactor with an electric power of up to 3 GW. In contrast to previously proposed innovations, the article considers core layouts containing fuel pins with claddings made entirely of tungsten. Emergency modes are modeled approximately based on solving three groups of equations: a system of point kinetic equations, a non-stationary heat conduction equation, which, and a reactivity balance equation. The value of the void reactivity effect is estimated based on the solution of the gas-kinetic neutron transport equation. Reserves have been identified in further increasing the power and safety of the power reactor. They are associated with the optimization of the size of granules of ceramic and metal powders in the fuel composition.

Differential group delay behavior in homogeneous weakly coupled multicore fiber under bending and twisting condition

The impacts of core count/layout on the mode effective refractive index (\({n}_{\mathrm{eff}}\)), bend- and twist-induced differential group delay (DGD) of different cores, worst-case DGD, and intercore DGD (\({\mathrm{DGD}}_{\mathrm{IC}}\)), in weakly coupled homogeneous multicore fibers (WC-HMCFs), have been analyzed to select the proper core layout with low DGD value for a particular core count. The core counts such as 3-core, 4-core, 6-core, and 12-core and the core layouts namely linear, triangular, square, rectangular, circular one ring structure (ORS), circular dual ring structure (DRS), hexagonal ORS, and square lattice structure (SLS) have been considered in the investigation. Moreover, in order to calculate the \({\mathrm{DGD}}_{\mathrm{IC}}\) values, the generalized expressions of core pitch (Λ) for the different core layouts have been derived. Further, the impacts of core radius (\(a\)), relative refractive index difference (\(\Delta\)), and Λ on the \({n}_{\mathrm{eff}}\) and DGD levels for the 3-core WC-HMCFs, with linear and triangular core layouts, have been analyzed numerically by using the finite element method-based FemSIM simulation platform, and MATLAB. It is observed that for a certain core count value, the core layout and Λ have significant impacts on the DGD levels, while the variations in the values of \(a\) and \(\Delta\) have no significant impact on the DGD levels. Further, increase in core count normally increases the DGD levels in all core layouts. On the other hand, for the fixed values of core count, cladding diameter (D), and outer cladding thickness (OCT), the core layout which has the lowest core pitch leads to the lowest value of \({\mathrm{DGD}}_{\mathrm{IC}}\), as compared to the other core layouts. The investigations carried out in this work may provide the guidelines in different MCF applications, such as MCF-based multi-parameter sensing and signal processing in microwave photonics.

Analysis of supermode properties in three-core homogeneous strongly coupled multicore fiber

We have investigated the supermode properties, namely, mode effective refractive index (RI) (neff), effective area (Aeff), and chromatic dispersion (CD), in three-core homogeneous strongly coupled multicore fibers (SC-MCFs) for different core RI profiles (step index and RI dip) and in different possible core arrangements (triangular and linear). Further, the impacts of fiber parameters, namely, core radius (a), relative RI difference between core and cladding (Δ), and core pitch (Λ), on the differential group delay (DGD) between different supermodes have also been analyzed for all the considered configurations of SC-MCFs. The analysis presented has been done numerically using the FemSIM simulation platform. It has been observed that core arrangement has significant impact on the levels of neff, Aeff, CD, and DGD, and it also affects the degeneracy of the supermodes in a three-core homogeneous SC-MCF. Further, there exist certain core pitches in which the Aeff values of fundamental supermodes in different core layouts are equal. Furthermore, there exists a certain relative RI difference between the core and cladding (Δ) values in which DGD values in all the considered SC-MCF configurations are equal. On the other hand, over a range of Δ values, DGD in a linear layout is flattened compared to a triangular layout. Incorporating the RI dip structure in the cores of SC-MCFs affects the CD levels significantly. Therefore, by careful control of the fiber parameters and core arrangement, large mode effective area and low and flattened dispersion SC-MCF can be designed that may be suitable in dense wavelength division multiplexing application.

Experimental and analytical behaviour of sandwich composites with glass fiber-reinforced polymer facings and layered fiber mat cores

This paper presents the results of experimental and analytical studies on the behaviour of sandwich beams fabricated with layered cores and glass fiber-reinforced polymer (GFRP) composite facings. The GFRP facings were fabricated using a unidirectional fiberglass fabric and epoxy resin, and the cores were fabricated using a thin non-woven continuous-strand polyester fiber mat with a thickness of 4.1 mm. A total of 30 sandwich beams with the width of 50 mm were prepared tested with five varying core configurations including cores made with one, two, or three layers of the fiber mat core and with or without the inclusion of intermediate GFRP layers. The specimens were tested up to failure under four-point bending at two different spans to characterize flexural and shear properties of the specimens. Two types of failure were observed, namely crushing of the compression facesheet and core shear. The load-deflection, load-strain, and moment-curvature behaviour were analyzed and using the results the flexural stiffness, shear stiffness, and core shear modulus were calculated. An analytical model was also developed to predict load-deflection behaviour and failure loading of sandwich specimens with varying core layouts. After verification, the analytical model was used for a parametric study of cases not considered in the experimental study, including additional GFRP and fiber mat core layers. It was shown that additional fiber mat core layers and the inclusion of intermediate GFRP layers can increase the strength and overall stiffness of a sandwich beam, while additional GFRP layers can only increase the overall stiffness of the system. The analytical model can be used to optimize the configuration of layered sandwich composites for cost effective rehabilitation techniques of culverts, pipelines, and other curved-shape structures where a thin, flexible core is needed to accommodate the curvature of the existing structure.

Worst crosstalk analysis in heterogeneous and trench assisted heterogeneous multicore fiber for different core counts and layouts

In order to obtain appreciably low worst crosstalk level in high core count multicore fiber, heterogeneous MCF with different core configurations and layouts have been investigated analytically using coupled mode equation. The variations in worst crosstalk behavior with respect to the bending radius, core configurations, core layouts, and outer cladding thickness have been analyzed. Further, the core count dependent variations in worst crosstalk level, core pitch, and peak bending radius in different core layouts have been presented. It has been observed that the selection of core configuration, core layout, and outer cladding thickness have significant impact on the reduction in worst crosstalk level. For example, in 12-core normal-index heterogeneous MCF with SLS structure, the core Configuration 1 can provide the worst crosstalk level reduced by 7.09 dB and 16.92 dB in comparison to the other two core configurations, i.e., Configuration 2, and Configuration 3, respectively. Further, for the same core count with TA Configuration 1, SLS core layout can achieve the reduced worst crosstalk level in comparison with circular ORS and DRS, hexagonal ORS and DRS respectively by 24.62 dB, 25.86 dB, 28.87 dB and 30.64 dB.

Simple GDS Estimation Method for Coupled Multicore Fibers with Various Core Layouts

Simple GDS Estimation Method for Coupled Multicore Fibers with Various Core Layouts

Reconstruction of cell homogenized macroscopic cross sections for analyzing fast and thermal coupled cores using the SRAC system

A fast and thermal neutron coupled core adopts blanket fuel assemblies with zirconium hydrides in the core for negative coolant void reactivity. Conventional neutronics calculation methods have been developed for analysis of a fast core or thermal core, in which the coarse-group macroscopic cross sections of fuel assemblies are prepared without including the effect of the surrounding fuel assemblies. However, such methods are not adequate for analyzing fast and thermal neutron coupled cores where the intra-assembly and inter-assembly heterogeneity effects must be precisely taken into account. Recently, a concept of reconstruction of cell homogenized macroscopic cross sections has been proposed to take into account effects of inter-assembly heterogeneities on macroscopic cross sections used in the reactor core analysis and successfully applied based on a Monte Carlo method. In the present study, a reconstruction method of cell homogenized coarse-group macroscopic cross section for analyzing fast and thermal coupled cores is developed based on a deterministic neutronics calculation code system, SRAC. Three types of fixed source calculations for unit assembly cell geometry are performed independently of the specific core layouts and their results are combined with the results of core analysis to produce cell homogenized coarse-group macroscopic cross sections. Numerical results show that the heterogeneity effects can be adequately reflected in the reconstructed macroscopic cross sections with the proposed method. When the number of energy groups is small, the proposed method gives poor results in the transitional energy groups from resonance to thermal energy. Therefore, it is necessary to increase the number of energy groups in this energy range.

Modeling and validation of approach to criticality and axial flux profile experiments at the Missouri S&T Reactor (MSTR)

An MCNP model of the Missouri University of Science and Technology Reactor (MSTR) has been in development since 2007. The MCNP model is based on the best available configuration and composition data for the reactor and is flexible, allowing easy re-configuration to accommodate multiple core layouts. Validation of the model included the simulation of experiments routinely performed at the reactor and comparing the simulation results with the experimental data. These validation experiments include the approach to criticality (predicting critical control rod height) and the determination of the axial flux profile in the core. There is good agreement between the experimental data and the model predictions. The most accurate flux profile was produced when the model included an axial temperature variation. The modeled normalized profile accounting temperature variations matches within 10% at 34 of 49 points with the experimental data and within 30% at 46 of 49 points. The simulated approach to criticality matched with the experimental data with an average difference of 0.59 ± 0.08 in. at all points. One significant source of difference between the simulated and experimental data is that the model uses fresh fuel compositions and does not take into account the 20 years of operation and the consequential burnup and poison buildup. Moreover, the initial model does not consider detailed temperature variations and effects, causing a systematic difference between the simulated critical control rod position and the experimental values.

Modelling the core properties of composite panels based on woven sandwich-fabric preforms

A finite-element preprocessing program was developed to predict the mechanical performance of the cores of woven sandwich-fabric panels. These materials, which are produced from velvet-weave sandwich-fabric preforms, provide a new type of sandwich structure with a high skin-core debonding resistance and the potential for cost-effective sandwich construction. There is a large variety in possible core layouts and thus mechanical performance. To model the core behaviour a detailed geometrical modelling of the core lay-out of unfoamed panels was carried out. A unit-cell of the sandwich-fabric panel under consideration is determined and the shape of the piles and pillars and the resin distribution inside the unit cell are modelled. As inputs, only weaving data and some panel production parameters are required. The predicted microstructure for the cases which were modelled had a good resemblance to reality. For the FE analysis a homogenization principle has been used. Linear static analyses for the basic core properties (flexural shear and flat compression) have been performed. The results for the shear modulus as a function of the pile shape were very good. Model predictions at higher resin contents and for the compression modulus were less accurate.

Mechanical properties of composite panels based on woven sandwich-fabric preforms

An overview of the mechanical properties of the core of woven sandwich-fabric panels is given. These materials provide a new type of sandwich structure with a high skin–core debonding resistance and the potential for cost-effective sandwich construction. The sandwich-fabric preforms are produced by a large-scale textile weaving process (velvet weaving). The basic mechanical properties of the sandwich core (compression and shear) were evaluated and compared with those of other core materials. There is a large variety in possible core layouts and thus mechanical performance for sandwich-fabric panels. Acceptable mechanical properties for cores of higher thickness (higher than 10 mm) can be obtained by weaving part of the pile fibres in the core under angles of ±45°, by creating networks of piles at lower degrees of stretching and sufficient pile density, or by filling the core with foam. There appears to be a strong synergistic effect between pile and foam properties in the sandwich core.

Design status of the HTR 500 power plant and the HTR module power plant

The conceptual designs of the HTR 500 and the HTR-Module reactors are described. The engineering design criteria and the structure of the pebble bed cores in these reactors are discussed, with special reference to the testing of the high temperature components in the AVR and THTR reactors and in the Interatom KVI Test Facility. Other components that are described include heat exchangers, hot gas ducts, helium circulators with magnetic bearings, steel fiber concrete for the PCRV, computer codes for core layouts, and the status of fuel element testing.

Status of Axial Heterogeneous Liquid-Metal Fast Breeder Reactor Core Design Studies and Research and Development

The current status of axial heterogeneous core (AHC) design development in Japan, which consists of an AHC core design in a pool-type demonstration fast breeder reactor (DFBR) and research and development activities supporting AHC core design, is presented. The DFBR core design objectives developed by The Japan Atomic Power Company include (a) favorable core seismic response, (b) core compactness, (c) high availability, and (d) lower fuel cycle cost. The AHC concept was selected as a reference pool-type DFBR core because it met these objectives more suitably than the homogeneous core (HOC). The AHC core layouts were optimized emphasizing the reduction of the burnup reactivity swing, peak fast fluence, and power peaking. The key performance parameters resulting from the AHC, such as flat axial power/flux distribution, lower peak fast fluence, lower burnup reactivity swing, etc., were evaluated in comparison with the HOC. The critical experiments at the Japan Atomic Energy Research Institute’s Fast Critical Assembly facility demonstrate the key AHC performance characteristics. The large AHC engineering benchmark experiments using the zero-power plutonium reactor and the AHC fuel pin irradiation test program using the JOYO reactor are also presented.

Nuclear Performance of Liquid-Metal Fast Breeder Reactors Designed to Preclude Energetic Hypothetical Core Disruptive Accidents

A study of various core designs was conducted to investigate design features pertaining to the preclusion of energetic hypothetical core disruptive accidents. The design data and core layouts for d...