Xiang Fang, Anthony Chun Yin Yuen, Eric Wai Ming Lee, Jiyuan Tu and Sherman Cheung
The purpose of this paper is to investigate the development process of the fire whirl in the fixed-frame facility and focus on the impacts of the fire whirl’s vortex core on the…
Abstract
Purpose
The purpose of this paper is to investigate the development process of the fire whirl in the fixed-frame facility and focus on the impacts of the fire whirl’s vortex core on the formation and flame structure of the fire whirl.
Design/methodology/approach
The complex turbulent reacting flame surface is captured by the large eddy simulation turbulence closure coupled with two sub-grid scale (SGS) kinetic schemes (i.e. the chemistry equilibrium and steady diffusion flamelet). Numerical predictions are validated thoroughly against the measurements by Lei et al. (2015) with excellent agreements. A double maximum tangential velocity refinement approach is proposed to quantify the vortex cores’ instantaneous location and region, addressing the missing definition in other studies.
Findings
The numerical results show that the transition process of the fire whirl is dominated by the vortex core movement, which is related to the centripetal force. The unsteadiness of the fully developed fire whirl was found depending on the instantaneous fluctuation of heat release rate. The steady diffusion flamelet scheme is essential to capture the instantaneous fluctuation. Furthermore, the axial velocity inside the vortex core is the key to determining the state of fire whirl.
Practical implications
Due to intensive interactions between buoyant fires and ambient rotating flow, the on-set and formation of fire whirl still remain largely elusive. This paper focused on the transition process of fire whirl between different development stages. This paper provides insights into the transition process from the inclined flame to the fire whirls based on the centripetal force.
Originality/value
This paper presented and compared two SGS kinetic schemes to resolve the fire whirl development process and the unsteadiness of its vortical structures. The modelling framework addresses the shortcoming of previous numerical studies where RANS turbulence closure and simplified combustion kinetics was adopted. Numerical results also revealed the fire whirl transition process and its relationship to centripetal force.
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Md Delwar Hossain, Md Kamrul Hassan, Anthony Chun Yin Yuen, Yaping He, Swapan Saha and Waseem Hittini
The purpose of this study is to review and summarise the existing available literature on lightweight cladding systems to provide detailed information on fire behaviour…
Abstract
Purpose
The purpose of this study is to review and summarise the existing available literature on lightweight cladding systems to provide detailed information on fire behaviour (ignitibility, heat release rate and smoke toxicity) and various test method protocols. Additionally, the paper discusses the challenges and provides updated knowledge and recommendation on selective-fire mechanisms such as rapid-fire spread, air cavity and fire re-entry behaviours due to dripping and melting of lightweight composite claddings.
Design/methodology/approach
A comprehensive literature review on fire behaviour, fire hazard and testing methods of lightweight composite claddings has been conducted in this research. In summarising all possible fire hazards, particular attention is given to the potential impact of toxicity of lightweight cladding fires. In addition, various criteria for fire performance evaluation of lightweight composite claddings are also highlighted. These evaluations are generally categorised as small-, intermediate- and large-scale test methods.
Findings
The major challenges of lightweight claddings are rapid fire spread, smoke production and toxicity and inconsistency in fire testing.
Originality/value
The review highlights the current challenges in cladding fire, smoke toxicity, testing system and regulation to provide some research recommendations to address the identified challenges.
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K.C. LAM, TIESONG HU, S.O. CHEUNG, R.K.K. YUEN and Z.M. DENG
Modelling of the multiproject cash flow decisions in a contracting firm facilitates optimal resource utilization, financial planning, profit forecasting and enables the inclusion…
Abstract
Modelling of the multiproject cash flow decisions in a contracting firm facilitates optimal resource utilization, financial planning, profit forecasting and enables the inclusion of cash‐flow liquidity in forecasting. However, a great challenge for contracting firm to manage his multiproject cash flow when large and multiple construction projects are involved (manipulate large amount of resources, e.g. labour, plant, material, cost, etc.). In such cases, the complexity of the problem, hence the constraints involved, renders most existing regular optimization techniques computationally intractable within reasonable time frames. This limit inhibits the ability of contracting firms to complete construction projects at maximum efficiency through efficient utilization of resources among projects. Recently, artificial neural networks have demonstrated its strength in solving many optimization problems efficiently. In this regard a novel recurrent‐neural‐network model that integrates multi‐objective linear programming and neural network (MOLPNN) techniques has been developed. The model was applied to a relatively large contracting company running 10 projects concurrently in Hong Kong. The case study verified the feasibility and applicability of the MOLPNN to the defined problem. A comparison undertaken of two optimal schedules (i.e. risk‐avoiding scheme A and risk‐seeking scheme B) of cash flow based on the decision maker's preference is described in this paper.
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K.C. LAM, TIE SONG HU, THOMAS NG, R.K.K. YUEN, S.M. LO and CONRAD T.C. WONG
Optimizing both qualitative and quantitative factors is a key challenge in solving construction finance decisions. The semi‐structured nature of construction finance optimization…
Abstract
Optimizing both qualitative and quantitative factors is a key challenge in solving construction finance decisions. The semi‐structured nature of construction finance optimization problems precludes conventional optimization techniques. With a desire to improve the performance of the canonical genetic algorithm (CGA) which is characterized by static crossover and mutation probability, and to provide contractors with a profit‐risk trade‐off curve and cash flow prediction, an adaptive genetic algorithm (AGA) model is developed. Ten projects being undertaken by a major construction firm in Hong Kong were used as case studies to evaluate the performance of the genetic algorithm (GA). The results of case study reveal that the AGA outperformed the CGA both in terms of its quality of solutions and the computational time required for a certain level of accuracy. The results also indicate that there is a potential for using the GA for modelling financial decisions should both quantitative and qualitative factors be optimized simultaneously.
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G.H. Yeoh, R.K.K. Yuen, E.W.M. Lee and S.C.P. Chueng
This paper presents a comparison of numerical predictions employing a Computational Fluid Dynamics fire model against a series of turbulent buoyant fire experiments recently…
Abstract
This paper presents a comparison of numerical predictions employing a Computational Fluid Dynamics fire model against a series of turbulent buoyant fire experiments recently carried out in a two‐room compartment structure by Nielsen and Fleischmann at the University of Canterbuty, New Zealand. The model incorporates turbulence, combustion, soot generation and radiation due to a fire. An evaluation of the various approaches—volumetric heat source approach or a more sophisticated handling the fire through a combustion model—is carried out. The effect of radiation due to combustion products and soot is also investigated. The model considering combustion with radiation contribution by both the combustion products and soot provides the best agreement between the predicted results and measured data. The presence of soot is seen to significantly augment the global radiation process within the two‐compartment enclosure.
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M. Vishal and K.S. Satyanarayanan
This study delineates the effect of cover thickness on reinforced concrete (RC) columns and beams under an elevated fire scenario. Columns and beams are important load-carrying…
Abstract
Purpose
This study delineates the effect of cover thickness on reinforced concrete (RC) columns and beams under an elevated fire scenario. Columns and beams are important load-carrying structural members of buildings. Under all circumstances, the columns and beams were set to be free from damage to avoid structural failure. Under the high-temperature scenario, the RC element may fail because of the material deterioration that occurs owing to the thermal effect. This study attempts to determine the optimum cover thickness for beams and columns under extreme loads and fire conditions.
Design/methodology/approach
Cover thicknesses of 30, 40, 45, 50, 60 and 70 mm for the columns and 10, 20, 25, 30, 35, 40, 50, 60 and 70 mm for the beams were adopted in this study. Both steady-state and transient-state conditions under thermomechanical analysis were performed using the finite element method to determine the heat transfer through the RC section and to determine the effect of thermal stresses.
Findings
The results show that the RC elements have a greater influence on the additional cover thickness at extreme temperatures and higher load ratios than at the service stages. The safe limits of the structural members were obtained under the combined effects of elevated temperatures and structural loads. The results also indicate that the compression members have a better thermal performance than the flexural members.
Research limitations/implications
Numerical investigations concerning the high-temperature behavior of structural elements are useful. The lack of an experimental setup encourages researchers to perform numerical investigations. In this study, the finite element models were validated with existing finite element models and experimental results.
Practical implications
The obtained safe limit for the structural members could help to understand their resistance to fire in a real-time scenario. From the safe limit, a suitable design can be preferred while designing the structural members. This could probably save the structure from collapse.
Originality/value
There is a lack of both numerical and experimental research works. In numerical modeling, the research works found in the literature had difficulties in developing a numerical model that satisfactorily represents the structural members under fire, not being able to adequately understand their behavior at high temperatures. None of them considered the influence of the cover thickness under extreme fire and loading conditions. In this paper, this influence was evaluated and discussed.
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Jian-Ping Wang, Mei-Ru Wang, Jian-Lan Zhou, Qing-Jun Zuo and Xun-Xian Shi
The purpose of this study is to develop optimal evacuation plan to provide valuable theoretical and practical insight in the fire evacuation work of similar structures, by…
Abstract
Purpose
The purpose of this study is to develop optimal evacuation plan to provide valuable theoretical and practical insight in the fire evacuation work of similar structures, by proposing a systematic simulation-based guided-evacuation agent-based model (GAM) and a three-stage mathematical evacuation model to investigate how to simulate, assess and improve the performance efficiency of the evacuation plan.
Design/methodology/approach
The authors first present the self-evacuation and guided-evacuation models to determine the optimal evacuation plan in ship chamber. Three key performance indicators are put forward to quantitatively assess the evacuation performance within the two fire scenarios. The evacuation model in tower is built to obtain the dividing points of the three different fire evacuation plans.
Findings
The study shows that the optimal evacuation plan determined by the GAM considering social relationships effectively relieves the congestion or collision of evacuees and improves the evacuation uniformity. The optimal evacuation plan not only solves the crush caused by congestion or collision of evacuees but also can greatly shorten the evacuation time for passenger ship fire.
Originality/value
This study establishes the GAM considering the interactive evacuee characteristics and the proportion of evacuees guided by the crew members to make the optimal evacuation plan more time-efficient. The self-evacuation process is simulated to assess the performance of the guided-evacuation strategies, which are used to verify the effectiveness and feasibility of the optimal evacuation plan in this research.
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Mostafa Esmaeili and Asghar Afshari
This study aims to numerically investigate the flow features and mixing/combustion efficiencies in a turbulent reacting jet in cross-flow by a hybrid Eulerian-Lagrangian…
Abstract
Purpose
This study aims to numerically investigate the flow features and mixing/combustion efficiencies in a turbulent reacting jet in cross-flow by a hybrid Eulerian-Lagrangian methodology.
Design/methodology/approach
A high-order hybrid solver is employed where, the velocity field is obtained by solving the Eulerian filtered compressible transport equations while the species are simulated by using the filtered mass density function (FMDF) method.
Findings
The main features of a reacting JICF flame are reproduced by the large-eddy simulation (LES)/FMDF method. The computed mean and root-mean-square values of velocity and mean temperature field are in good agreement with experimental data. Reacting JICF’s with different momentum ratios are considered. The jet penetrates deeper for higher momentum ratios. Mixing and combustion efficiency are improved by increasing the momentum ratio.
Originality/value
The authors investigate the flow and combustion characteristics in subsonic reacting JICFs for which very limited studies are reported in the literature.
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Mohammad Azim Eirgash and Vedat Toğan
Most of the existing time-cost-quality-environmental impact trade-off (TCQET) analysis models have focused on solving a simple project representation without taking typical…
Abstract
Purpose
Most of the existing time-cost-quality-environmental impact trade-off (TCQET) analysis models have focused on solving a simple project representation without taking typical activity and project characteristics into account. This study aims to present a novel approach called the “hybrid opposition learning-based Aquila Optimizer” (HOLAO) for optimizing TCQET decisions in generalized construction projects.
Design/methodology/approach
In this paper, a HOLAO algorithm is designed, incorporating the quasi-opposition-based learning (QOBL) and quasi-reflection-based learning (QRBL) strategies in the initial population and generation jumping phases, respectively. The crowded distance rank (CDR) mechanism is utilized to rank the optimal Pareto-front solutions to assist decision-makers (DMs) in achieving a single compromise solution.
Findings
The efficacy of the proposed methodology is evaluated by examining TCQET problems, involving 69 and 290 activities, respectively. Results indicate that the HOLAO provides competitive solutions for TCQET problems in construction projects. It is observed that the algorithm surpasses multiple objective social group optimization (MOSGO), plain Aquila Optimization (AO), QRBL and QOBL algorithms in terms of both number of function evaluations (NFE) and hypervolume (HV) indicator.
Originality/value
This paper introduces a novel concept called hybrid opposition-based learning (HOL), which incorporates two opposition strategies: QOBL as an explorative opposition and QRBL as an exploitative opposition. Achieving an effective balance between exploration and exploitation is crucial for the success of any algorithm. To this end, QOBL and QRBL are developed to ensure a proper equilibrium between the exploration and exploitation phases of the basic AO algorithm. The third contribution is to provide TCQET resource utilizations (construction plans) to evaluate the impact of these resources on the construction project performance.
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Tharindu Dulshani Jayarathne, Nayanthara De Silva and W. K. U. R. M. K. P. K. Samarakoon
Energy consumption in existing office buildings has been growing in parallel with the rise in occupant energy demand. As a result, many building owners have given smart retrofits…
Abstract
Purpose
Energy consumption in existing office buildings has been growing in parallel with the rise in occupant energy demand. As a result, many building owners have given smart retrofits (SRs) a higher priority. However, the utilisation of suitable SRs from a range of SRs has become a challenging task. The purpose of this paper is to develop a decision-making model to select the most suitable SRs for conventional office buildings and form a set of benchmarks for assessing the performance of SRs.
Design/methodology/approach
A qualitative approach with six case studies was used. Content analysis was carried out using NVivo to explore the factors considered for the selection of SR techniques. A decision-making model for selecting SRs in Sri Lankan office buildings was proposed. SR performance benchmarks were developed by referring to established standards and studies done in tropical office buildings.
Findings
Out of 18 identified SRs from literature, fan cycling, ventilation control and LED luminaires have been recognised as commonly used SRs in Sri Lankan office buildings. Analysis showed that HVAC retrofits saved more energy, while lighting retrofits could be easily implemented in existing buildings. The proposed decision-making model can explore further improvements to enhance the performance of SRs.
Originality/value
The selection of SRs is a comprehensive decision-making process. Metrics were established to benchmark the performance of SRs. The proposed model offers a tool for building owners and facility managers to optimise facility operations.