Commenced in January 2007
Frequency: Monthly
Edition: International
Paper Count: 467

World Academy of Science, Engineering and Technology

[Structural and Construction Engineering]

Online ISSN : 1307-6892

467 Safety Improvements of Mechanically Stabilized Earth Wall-External Stability

Authors: Reda Farag, Samir Elnaggar, Saleem Al-Saleem, Ibrahim Al-Salamah, Sayed Habib, Abdulrahman Alobaidan

Abstract:

The Mechanically stabilized earth wall (MSE-wall) is distinguished by ease of execution and low cost. The design of this structural system is recently updated to load resistance factor design (LRFD) to improve safety and optimize the cost. The current paper investigates the safety of the external performance of an MSE-wall before and after LRFD. The considered external stability involves; base sliding, overturning, bearing capacity and novel excessive eccentricity. The reliability analysis is performed using the first-order reliability method (FORM) and Monte Carlo Simulation Method (MCSM). The reliability results are presented in a suggested developed safety curve, and judgment evaluation is exercised. Eventually, an intensive parametric study has been introduced. For the considered example, it has been found that the four modes of failure have non-consistent and non-uniform reliability indices. Only the base sliding has a reliability index < 3. Soil parameters, internal friction angle, unit weight and cohesive strength are the most significant variables.

Keywords: MSE-wall, reliability, probability of failure, external stability.

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466 Determination of Significant Factors Affecting On-Site Tracking Process Efficiency in Turkish Construction Industry

Authors: Emir Nuri Yildiz, Hande Aladag

Abstract:

The construction industry is a vital sector in the development of infrastructure and buildings. The efficiency of tracking processes at construction sites plays a crucial role in determining the success of projects and overall productivity levels. To address this issue, this study aimed to provide valuable insights into the factors affecting the efficiency of tracking processes in the construction industry and to support initiatives aimed at improving productivity and project outcomes. The research methodology of this study involved conducting a comprehensive literature review of articles published in the last 20 years, resulting in the identification of 44 potential factors under six main categories that could impact on-site tracking efficiency. These factors were then evaluated and validated through a survey of experts working in the construction industry. The survey results were then analyzed using Relative Importance Index (RII) analysis which is commonly used for determining the significance level of identified factors. The results of the survey emphasized the critical role of resource allocation, technology utilization, and communication in determining productivity levels at construction sites. The findings highlight the importance of considering these factors in the implementation of strategies aimed at improving productivity in the construction industry. The survey also revealed that factors such as low fees and payment delays, lack of construction management skills, and the use of inappropriate equipment were among the most critical issues affecting the efficiency of tracking processes. In conclusion, this study sheds light on the complexities of the construction industry and the need to address the key efficiency factors affecting the tracking processes at construction sites. The results of the survey could guide future efforts aimed at enhancing efficiency in the construction industry and improving project outcomes.

Keywords: construction industry, productivity, relative importance index (RII), site tracking, site management.

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465 DesignChain: Automated design of products featuring a large number of variants

Authors: Lars Rödel, Jonas Krebs, Gregor Müller

Abstract:

The growing price pressure due to the increasing number of global suppliers, the growing individualization of products and ever-shorter delivery times are upcoming challenges in the industry. In this context, Mass Personalization stands for the individualized production of customer products in batch size 1 at the price of standardized products. The possibilities of digitalization and automation of technical order processing open up the opportunity for companies to significantly reduce their cost of complexity and lead times and thus enhance their competitiveness. Many companies already use a range of CAx tools and configuration solutions today. Often, the expert knowledge of employees is hidden in "knowledge silos" and is rarely networked across processes. DesignChain describes the automated digital process from the recording of individual customer requirements, through design and technical preparation, to production. Configurators offer the possibility of mapping variant-rich products within the Design Chain. This transformation of customer requirements into product features makes it possible to generate even complex CAD models, such as those for large-scale plants, on a rule-based basis. With the aid of an automated CAx chain, production-relevant documents are thus transferred digitally to production. This process, which can be fully automated, allows variants to always be generated on the basis of current version statuses.

Keywords: automation, design, CAD, CAx

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464 Combining the Fictitious Stress Method and Displacement Discontinuity Method in Solving Crack Problems in Anisotropic Material

Authors: Bahatti̇N Ki̇Mençe, UğUr Ki̇Mençe

Abstract:

In this study, the purpose of obtaining the influence functions of the displacement discontinuity in an anisotropic elastic medium is to produce the boundary element equations. A Displacement Discontinuous Method formulation (DDM) is presented with the aim of modeling two-dimensional elastic fracture problems. This formulation is found by analytical integration of the fundamental solution along a straight-line crack. With this purpose, Kelvin's fundamental solutions for anisotropic media on an infinite plane are used to form dipoles from singular loads, and the various combinations of the said dipoles are used to obtain the influence functions of displacement discontinuity. This study introduces a technique for coupling Fictitious Stress Method (FSM) and DDM; the reason for applying this technique to some examples is to demonstrate the effectiveness of the proposed coupling method. In this study, displacement discontinuity equations are obtained by using dipole solutions calculated with known singular force solutions in an anisotropic medium. The displacement discontinuities method obtained from the solutions of these equations and the fictitious stress methods is combined and compared with various examples. In this study, one or more crack problems with various geometries in rectangular plates in finite and infinite regions, under the effect of tensile stress with coupled FSM and DDM in the anisotropic environment, were examined, and the effectiveness of the coupled method was demonstrated. Since crack problems can be modeled more easily with DDM, it has been observed that the use of DDM has increased recently. In obtaining the displacement discontinuity equations, Papkovitch functions were used in Crouch, and harmonic functions were chosen to satisfy various boundary conditions. A comparison is made between two indirect boundary element formulations, DDM, and an extension of FSM, for solving problems involving cracks. Several numerical examples are presented, and the outcomes are contrasted to existing analytical or reference outs.

Keywords: displacement discontinuity method, fictitious stress method, crack problems, anisotropic material

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463 Influence of Organizational Culture and Leadership Style on Frequency of Disputes in Commercial Projects in Egypt–A Contractor’s Perspective

Authors: Omneya N. Mekhaimer, Elkhayam M. Dorra, A. Samer Ezeldin

Abstract:

Over the recent decades, studies on organizational culture have gained global attention in the business management literature, where it has been established that the cultural factors embedded in the organization have an implicit yet significant influence on the organization’s success. Unlike other industries, the construction industry is widely known to be operating in a dynamic and adversarial nature; considering the unique characteristics it denotes, thereby the level of disputes has propagated in the construction industry throughout the years. In the late 1990s, the International Council for Research and Innovation in Building and Construction (CIB) created a Task Group (TG-23), which later evolved in 2006 into a Working Commission W112, with a strategic objective to promote research in investigating the role and impact of culture in the construction industry worldwide. To that end, this paper aims to study the influence of organizational culture in the contractor’s organization on the frequency of disputes caused between the client and the contractor that occur in commercial projects based in Egypt. This objective is achieved by using a quantitative approach through a survey questionnaire to explore the dominant cultural attributes that exist in the contractor’s organization based on the Competing Value Framework (CVF) theory, which classifies organizational culture into four main cultural types: (1) clan, (2) adhocracy, (3) market, and (4) hierarchy. Accordingly, the collected data are statistically analyzed using Statistical Package for Social Sciences (SPSS 28) software, whereby correlation analysis using Pearson Correlation is carried out to assess the relationship between variables and their statistical significance using the p-value. The results show that there is an influence of organizational culture attributes on the frequency of disputes whereby market culture is identified to be the most dominant organizational culture that is currently practiced in contractor’s organization, which consequently contributes to increasing the frequency of disputes in commercial projects. These findings suggest that alternative management practices should be adopted rather than the existing ones in an aim to minimize dispute occurrence.

Keywords: construction projects, correlation analysis, disputes, Egypt, organizational culture

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462 Design of a CO₂-Reduced 3D Concrete Mixture Using Circular (Clay-Based) Building Materials

Authors: N.Z. van Hierden, Q. Yu, F. Gauvin

Abstract:

Cement manufacturing is, because of its production process, among the highest contributors to CO₂ emissions worldwide. As cement is one of the major components in 3D printed concrete, achieving sustainability and carbon neutrality can be particularly challenging. To improve the sustainability of 3D printed materials, different CO₂-reducing strategies can be used, each one with a distinct level of impact and complexity. In this work, we focus on the development of these sustainable mixtures and finding alternatives. Promising alternatives for cement and clinker replacement include the use of recycled building materials, amongst which (calcined) bricks and roof tiles. To study the potential of recycled clay-based building materials, the application of calcinated clay itself is studied as well. Compared to cement, the calcination temperature of clay-based materials is significantly lower, resulting in reduced CO₂ output. Reusing these materials is therefore a promising solution for utilizing waste streams while simultaneously reducing the cement content in 3D concrete mixtures. In addition, waste streams can be locally sourced, thereby reducing the emitted CO₂ during transportation. In this research, various alternative binders are examined, such as calcined clay blends (LC3) from recycled tiles and bricks, or locally obtained clay resources. Using various experiments, a high potential for mix designs including these resources has been shown with respect to material strength, while sustaining decent printability and buildability. Therefore, the defined strategies are promising and can lead to a more sustainable, low-CO₂ mixture suitable for 3D printing while using accessible materials.

Keywords: cement replacement, 3DPC, circular building materials, calcined clay, CO₂ reduction

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461 The Innovative In-site Lightweight Foam

Authors: Bishoy Magdy Boshra Abdelmalak, Osama Maher Fahmy Girgis, Amir Nashaat Shokry, Seddik Affifi, Vivian Ayoub Matta, Salem Aziz Selim Cassis

Abstract:

Lightweight foam concrete is a layer that creates a very thick and light insulation surface which is a mix of foam and cement. Energy is at the forefront of the most important issues for all countries today. The constantly growing world population and the expansion of industry have given way to unstoppable energy consumption. Some countries have already started energy-saving measures for various reasons, for example, to improve environmental protection, Pollution, rapid consumption of existing energy resources, and high energy generation costs. Nowadays, the problem of insulation has appeared in order to obtain the desired benefits while consuming less energy, and therefore the importance of insulation has increased. In this study, adding foam (water + blowing agent + air) works. A foam concrete with increased insulation parameters was prepared in a mortar foam generator (cement, water, silica dust, calcite and a mixture of superplasticizers). Aerated concrete has a bulk density of 250 kg/m³ and a thermal conductivity of 0.075 kg/m³. Foam concrete is a type of concrete whose unit mass is reduced by retaining air empty inside. In recent years it has been observed that this material has been favored as a building material, manufactured with a density between 1600 and 400 kg/m³ for use in structural partitions and due to non-load bearing elements, their different properties such as superfluidity, low Weight with minimal internal excess, controlled strength and excellent insulation. The idea of reducing bulk density by foaming to create air bubbles in concrete is said to date back to 1900. In conclusion, it is crystal clear that time consumed to fix the heat insulation sheets is more than three times the time exerted in pumping the mix of the lightweight foam concrete. This method would reduce the cost of heat insulation to more than 50%, and the durability of the insulation layer would be increased greatly to more than double.

Keywords: concrete, foam-concrete, roof-insulation, energy consumption, environmental protection, energy resources, aerated concrete, concrete insulation, thermal conductivity, foaming agent

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460 Climate Benefit of Reusing Concrete Elements in New Buildings: A Swedish Pilot Study

Authors: A. Al-Najjar, T. Malmqvist

Abstract:

This study aims to assess the climate benefit of a pilot building with structural elements of reused concrete from a life cycle perspective focusing on product and construction stages. The focus of this assessment is on implementing different methodological assumptions and discussing the upscaling opportunities of reusing concrete elements from a climate point of view. If a building has to be demolished, reusing the building elements is the highest possible level of circularity, potentially slowing down climate change. Different building demolition projects are both done and ongoing in different places in Europe, including Sweden, instead of extending the building’s lifespan due to different issues. Because of the industrial building method during the post-war period, concrete products dominate the Swedish building stock. On the other side, the technical lifespan of the concrete elements is longer than the economical service life of these buildings. Globally, the demand for cement is increasing, and the old elements could instead substitute for the new production of concrete elements. To highlight the climate benefit of this practice, a comparative and attributional life cycle assessment is done. The use and end-of-life life cycle stages are excluded due to the minor embodied carbon reduction of the studied building. The study case is a real-life demo building with a structural system of reused concrete elements built in Helsingborg within the Horizon 2020-funded project, ReCreate. This building was compared with a similar and hypothetical building but with only virgin building materials. The method of the assessment is based on the European standards’ guidelines. The assessment results show significant avoidance of embodied carbon when reusing concrete elements. Embodied carbon reduction is also obvious even with different assessment scenarios like different system modelling. Finally, the study emphasizes the need for further research in the field of evaluating the climate impact of reusing structural elements to be able to draw general conclusions about the benefits.

Keywords: circular economy, life cycle assessment, reuse, recycle, concrete, buildings, construction material, climate impact, embodied carbon, greenhouse gas emission

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459 Evaluation of Critical Success Factors in Public-Private Partnership Projects Based on Structural Equation Model

Authors: Medya Fathi

Abstract:

Today, success in the construction industry is not merely about project completion in a timely manner within an established budget and meeting required quality considerations. Management practices and partnerships need to be emphasized as well. In this regard, critical success factors (CSFs) cover necessary considerations for a successful project beyond the traditional success definition, which vary depending on project outcomes, delivery methods, project types, and partnering processes. Despite the extensive research on CSFs, there is a paucity of studies that examine CSFs for public-private partnership (PPP); the delivery method, which has gained increasing attention from researchers and practitioners over the last decade with a slow but growing adoption in the transportation infrastructure, particularly, highway industry. To fill this knowledge gap, data are collected through questionnaire surveys among private and public parties involved in PPP transportation projects in the United States. Then, the collected data are analyzed to explore the causality relationships between CSFs and PPP project success using structural equation model and provide a list of factors with the greatest influence. This study advocates adopting a critical success factor approach to enhance PPP success in the U.S. transportation industry and identify elements essential for public and private organizations to achieve this success.

Keywords: project success, critical success factors, public-private partnership, transportation

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458 Sustainability and Energy-Efficiency in Buildings: A review

Authors: Medya Fathi

Abstract:

Moving toward sustainable development is among today’s critical issues worldwide that make all industries, particularly construction, pay increasing attention to a healthy environment and a society with a prosperous economy. One of the solutions is to improve buildings’ energy performance by cutting energy consumption and related carbon emissions, eventually improving the quality of life. Unfortunately, the energy demand for buildings is rising. For instance, in Europe, the building sector accounts for 19% of the global energy-related greenhouse gas (GHGs) emissions, the main contributor to global warming in the last 50 years, and 36% of the total CO2 emissions, according to European Commission 2019. The crisis of energy use demands expanding knowledge and understanding of the potential benefits of energy-efficient buildings. In this regard, the present paper aims to critically review the existing body of knowledge on improving energy efficiency in buildings and detail the significant research contributions. Peer-reviewed journal articles published in the last decade in reputed journals were reviewed using the database Scopus and keywords of Sustainability, Sustainable Development, Energy Performance, Energy Consumption, Energy Efficiency, and Buildings. All contributions will be classified by journal type, publication time, country/region, building occupancy type, applied strategies, and findings. This study will provide an essential basis for researchers working on missing areas and filling the existing gaps in the body of knowledge.

Keywords: sustainability, energy performance, energy efficiency, buildings, review

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457 Exploring the Sources of Environmental Degradation of Heating, Ventilation, and Air Conditioning Systems

Authors: Timothy Frank, Josh Aldred, Justin White, Sophia Boulware, Michelle Cabonce

Abstract:

Materials degrade at different rates in different environments depending on factors such as temperature, aridity, salinity, and solar radiation. Therefore, predicting asset longevity depends, in part, on the environmental conditions to which the asset is exposed. Heating, ventilation, and air conditioning (HVAC) systems are critical to building operations yet are responsible for a significant proportion of their energy consumption. HVAC energy use increases substantially with slight operational inefficiencies. Understanding the environmental influences on HVAC degradation in detail will inform maintenance schedules and capital investment, reduce energy use and increase lifecycle management efficiency. HVAC inspection records spanning ten years from 40 locations across the United States were compiled and associated with the weather conditions to which they were exposed. Fifteen environmental variables were explored in this study. Using a non-parametric feature selection method, the most critical variables were identified. Using the principal features, an environmental degradation model for HVAC systems is proposed. The sensitivity analysis and regression accuracy of the model were explored. Results indicate that environmental harshness plays a meaningful role in HVAC system degradation and can reduce errors in degradation modeling when compared to a model that does not account for differences in environmental conditions.

Keywords: environmental harshness, component degradation, HVAC, feature selection, regression

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456 Development of a Flexible Lora-Based Wireless Sensory System for Long-Time Health Monitoring of Civil Structures

Authors: Hui Zhang, Sherif Beskhyroun

Abstract:

In this study, a highly flexible LoRa-Based wireless sensing system was used to assess the strain state performance of building structures. The system was developed to address the local damage limitation of structural health monitoring (SHM) systems. The system is part of an intelligent SHM system designed to monitor, collect and transmit strain changes in key structural components. The main purpose of the wireless sensor system is to reduce the development and installation costs, and reduce the power consumption of the system, so as to achieve long-time monitoring. The highly stretchable flexible strain gauge is mounted on the surface of the structure and is waterproof, heat resistant, and low temperature resistant, greatly reducing the installation and maintenance costs of the sensor. The system was also developed with the aim of using LoRa wireless communication technology to achieve both low power consumption and long-distance transmission, therefore solving the problem of large-scale deployment of sensors to cover more areas in large structures. In the long-term monitoring of the building structure, the system shows very high performance, very low actual power consumption, and wireless transmission stability. The results show that the developed system has a high resolution, sensitivity, and high possibility of long-term monitoring.

Keywords: LoRa, SHM system, strain measurement, civil structures, flexible sensing system

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455 Seismic Response for a Reinforced Concrete Residential Building According to South American Standards in the Pacific Zone. Case Study for Peru, Chile, and Ecuador

Authors: Henry Antonio Aguilar Chuquimia, Juan Alonso Alvarado Mamani

Abstract:

In the present work, the seismic response of a reinforced concrete building representative of modern multi-family residences of medium height in the southern zone of Peru was estimated. This region was considered because we can find growing urban areas with a variety of altitudes and consequently different seismic conditions, which can be found in the three countries of the case study, in accordance with the seismic standards of the Pacific area corresponding to the current official directives of Peru (E.030, 2018), Chile (NCh433, 2012) and Ecuador (NEC, 2015), using spectral modal analysis with the purpose of highlighting the most relevant aspects in the standards and identifying possible missing parameters that prominently influence the structural demand. The analysis included the estimation of shear forces, spectral acceleration and relative inter-story displacement, including variables such as seismic zoning, soil typology, category of use, structural system, among others; considering the approach of a uniform scheme for the comparison of limits between the relative inter-story displacement established in each standard. The process was carried out from numerical models of a 10-story reinforced concrete building consisting of frames and structural walls; finding, among others, that the highest acceleration demand at surface level in coastal regions for rocky soil (Vs ≥ 900 m/s) corresponds to Peru, followed by Ecuador and Chile. It is concluded in general, that the highest demands and the most restrictive limits for different seismic zones and different soil conditions correspond to the regulatory provisions of Peru.

Keywords: Seismic analysis, lateral displacement, spectral acceleration, seismic response

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454 Capacity of Cold-Formed Steel Warping-Restrained Members Subjected to Combined Axial Compressive Load and Bending

Authors: Maryam Hasanali, Syed Mohammad Mojtabaei, Iman Hajirasouliha, G. Charles Clifton, James B. P. Lim

Abstract:

Cold-formed steel (CFS) elements are increasingly being used as main load-bearing components in the modern construction industry, including low- to mid-rise buildings. In typical multi-storey buildings, CFS structural members act as beam-column elements since they are exposed to combined axial compression and bending actions, both in moment-resisting frames and stud wall systems. Current design specifications, including the American Iron and Steel Institute (AISI S100) and the Australian/New Zealand Standard (AS/NZS 4600), neglect the beneficial effects of warping-restrained boundary conditions in the design of beam-column elements. Furthermore, while a non-linear relationship governs the interaction of axial compression and bending, the combined effect of these actions is taken into account through a simplified linear expression combining pure axial and flexural strengths. This paper aims to evaluate the reliability of the well-known Direct Strength Method (DSM) as well as design proposals found in the literature to provide a better understanding of the efficiency of the code-prescribed linear interaction equation in the strength predictions of CFS beam columns and the effects of warping-restrained boundary conditions on their behavior. To this end, the experimentally validated finite element (FE) models of CFS elements under compression and bending were developed in ABAQUS software, which accounts for both non-linear material properties and geometric imperfections. The validated models were then used for a comprehensive parametric study containing 270 FE models, covering a wide range of key design parameters, such as length (i.e., 0.5, 1.5, and 3 m), thickness (i.e., 1, 2, and 4 mm) and cross-sectional dimensions under ten different load eccentricity levels. The results of this parametric study demonstrated that using the DSM led to the most conservative strength predictions for beam-column members by up to 55%, depending on the element’s length and thickness. This can be sourced by the errors associated with (i) the absence of warping-restrained boundary condition effects, (ii) equations for the calculations of buckling loads, and (iii) the linear interaction equation. While the influence of warping restraint is generally less than 6%, the code suggested interaction equation led to an average error of 4% to 22%, based on the element lengths. This paper highlights the need to provide more reliable design solutions for CFS beam-column elements for practical design purposes.

Keywords: beam-columns, cold-formed steel, finite element model, interaction equation, warping-restrained boundary conditions

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453 Ionic Liquid Desiccant for the Dehumidification System

Authors: Chih-Hao Chen, Yu-Heng Fang, Jyi-Ching Perng, Wei-Chih Lee, Yi-Hsiang Chen, Jiun-Jen Chen

Abstract:

Emerging markets are almost in the high temperature and high humidity area. Regardless of industry or domestic fields, the energy consumption of air conditioning systems in buildings is always significant. Moreover, the proportion of latent heat load is high. A liquid desiccant dehumidification system is one kind of energy-saving air conditioning system. However, traditional absorbents such as lithium chloride are hindered in market promotion because they will crystallized and cause metal corrosion. This study used the commercial ionic liquid to build a liquid desiccant dehumidification system with an air volume of 300 CMH. When the absolute humidity of the inlet air was 15g/kg, the absolute humidity of the outlet air was 10g/kg. The operating condition of a hot water temperature is 45 °C, and the cooling water temperature is 15 °C. The test result proves that the ionic liquid desiccant can completely replace the traditional liquid desiccant.

Keywords: ionic liquid desiccant, dehumidification, heat pump, air conditioning systems

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452 Nondestructive Monitoring of Atomic Reactions to Detect Precursors of Structural Failure

Authors: Volodymyr Rombakh

Abstract:

This article was written to substantiate the possibility of detecting the precursors of catastrophic destruction of a structure or device and stopping operation before it. Damage to solids results from breaking the bond between atoms, which requires energy. Modern theories of strength and fracture assume that such energy is due to stress. However, in a letter to W. Thomson (Lord Kelvin) dated December 18, 1856, J.C. Maxwell provided evidence that elastic energy cannot destroy solids. He proposed an equation for estimating a deformable body's energy, equal to the sum of two energies. Due to symmetrical compression, the first term does not change, but the second term is distortion without compression. Both types of energy are represented in the equation as a quadratic function of strain, but Maxwell repeatedly wrote that it is not stress but strain. Furthermore, he notes that the nature of the energy causing the distortion is unknown to him. An article devoted to theories of elasticity was published in 1850. Maxwell tried to express mechanical properties with the help of optics, which became possible only after the creation of quantum mechanics. However, Maxwell's work on elasticity is not cited in the theories of strength and fracture. The authors of these theories and their associates are still trying to describe the phenomena they observe based on classical mechanics. The study of Faraday's experiments, Maxwell's and Rutherford's ideas, made it possible to discover a previously unknown area of electromagnetic radiation. The properties of photons emitted in this reaction are fundamentally different from those of photons emitted in nuclear reactions and are caused by the transition of electrons in an atom. The photons released during all processes in the universe, including from plants and organs in natural conditions; their penetrating power in metal is millions of times greater than that of one of the gamma rays. However, they are not non-invasive. This apparent contradiction is because the chaotic motion of protons is accompanied by the chaotic radiation of photons in time and space. Such photons are not coherent. The energy of a solitary photon is insufficient to break the bond between atoms, one of the stages of which is ionization. The photographs registered the rail deformation by 113 cars, while the Gaiger Counter did not. The author's studies show that the cause of damage to a solid is the breakage of bonds between a finite number of atoms due to the stimulated emission of metastable atoms. The guarantee of the reliability of the structure is the ratio of the energy dissipation rate to the energy accumulation rate, but not the strength, which is not a physical parameter since it cannot be measured or calculated. The possibility of continuous control of this ratio is due to the spontaneous emission of photons by metastable atoms. The article presents calculation examples of the destruction of energy and photographs due to the action of photons emitted during the atomic-proton reaction.

Keywords: atomic-proton reaction, precursors of man-made disasters, strain, stress

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451 Contractor’s Cash Flow Optimization through the Selection of different Subcontracting Plans

Authors: Helen S. Ghali, Engy Serag, A. Samer Ezeldin

Abstract:

In many counties, the construction industry relies heavily on outsourcing models to execute their projects and expand their businesses to fit in the diverse market. Such extensive integration of outsourced subcontractors is becoming an influential factor in contractors' cash flow management. Accordingly, Subcontractors' price selection and their respective payment plans are important phenomena and pivotal components for the well-being of the contractor's cash flow. Cash flow management is considered one of the most critical areas analyzed by contractors when getting into a project. It is used to show the contractor's cash-out (expenses) and cash-in (received payments) during the project duration. This is established from a pool of interrelated information depending on subcontractors, suppliers, owner payment parameters, and construction schedule. There are two main parameters in payment management, namely the payment lag and payment frequency. These parameters are the building blocks of the contractor's cash-in and cash-out graphs. The purpose of this work is to study the contractor's cash flow with respect to the owner and subcontractor's payment management plans. Accordingly, a model is developed to provide contractors with a decision support tool that assists in selecting the optimum subcontracting plan and minimizes the contractor's negative cash flow and financing limits. The model is built using Microsoft Excel, where the contractor's cash-out S-Curve, cash-in, and overdraft are plotted using the inputted project data. The objective function is to minimize the highest negative overdraft value by selecting among different subcontracting packages. These packages include the subcontractor's price and payment parameters that affect the contractor's cash-out graph. The model is developed on a prototype project which encompasses subcontracted activities and other self-performed works. The results have shown potential outputs in optimizing the contractor's negative cash flow values and, in the meantime, assisting contractors in selecting the suitable subcontracting plan to achieve the objective function.

Keywords: cash flow optimization, payment plan, procurement management, subcontracting plan

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450 Copper Price Prediction Model During COVID-19 & Russian-Ukraine War Time Period

Authors: Haidy S. Ghali, Engy Serag, A. Samer Ezeldin

Abstract:

Copper is a valuable metal used in different industries and an essential raw material in the production of electrical components used in many construction projects, whether commercial, industrial, or mega projects. During the year 2021 & the first half of 2022, the global market suffered from a significant fluctuation in copper raw material prices due to the aftermath of both the COVID-19 pandemic and the Russia-Ukraine war, which exposed both the suppliers and contractors to unexpected risk. Thereto, this paper aims to develop two price prediction models that can forecast the average monthly copper prices traded in the London Metal Exchange for the next 1-month and 3-months in the future. The tool adopted in developing the models is the Long Short-Term Memory network (LSTM) using the Python programming language in jupyter notebook. Historical data of average monthly London Metal Exchange copper prices are collected from January 2009 till July 2022, and also other potential input variables are taken into account and used in the model. The variables considered are the copper raw material prices, the inflation rate and international reserve of the three major exporting countries of copper, the transportation index, and a global market indicator. Before developing the LSTM models, the collected input variables are analyzed with respect to the output variable using correlation, granger-causality, and multicollinearity tests in R software; then, the input variables are further filtered to select the highly correlated variables that influence the output variable. Then, the two LSTM models are developed, and the dataset is divided into training, validation, and testing sets. The models’ performances are assessed using the mean square error and absolute-percentage error. The results show that the performance of the 3-Month prediction model is higher than the 1-Month prediction model; however, both models can act as predicting tools for different time frames of high price fluctuations.

Keywords: copper prices, prediction model, neural network, time series forecasting

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449 A Proper Continuum-Based Reformulation of Current Problems in Finite Strain Plasticity

Authors: Ladislav Écsi, Roland Jančo

Abstract:

Contemporary multiplicative plasticity models assume that the body's intermediate configuration consists of an assembly of locally unloaded neighbourhoods of material particles that cannot be reassembled together to give the overall stress-free intermediate configuration since the neighbourhoods are not necessarily compatible with each other. As a result, the plastic deformation gradient, an inelastic component in the multiplicative split of the deformation gradient, cannot be integrated, and the material particle moves from the initial configuration to the intermediate configuration without a position vector and a plastic displacement field when plastic flow occurs. Such behaviour is incompatible with the continuum theory and the continuum physics of elastoplastic deformations, and the related material models can hardly be denoted as truly continuum-based. The paper presents a proper continuum-based reformulation of current problems in finite strain plasticity. It will be shown that the incompatible neighbourhoods in real material are modelled by the product of the plastic multiplier and the yield surface normal when the plastic flow is defined in the current configuration. The incompatible plastic factor can also model the neighbourhoods as the solution of the system of differential equations whose coefficient matrix is the above product when the plastic flow is defined in the intermediate configuration. The incompatible tensors replace the compatible spatial plastic velocity gradient in the former case or the compatible plastic deformation gradient in the latter case in the definition of the plastic flow rule. They act as local imperfections but have the same position vector as the compatible plastic velocity gradient or the compatible plastic deformation gradient in the definitions of the related plastic flow rules. The unstressed intermediate configuration, the unloaded configuration after the plastic flow, where the residual stresses have been removed, can always be calculated by integrating either the compatible plastic velocity gradient or the compatible plastic deformation gradient. However, the corresponding plastic displacement field becomes permanent with both elastic and plastic components. The residual strains and stresses originate from the difference between the compatible plastic/permanent displacement field gradient and the prescribed incompatible second-order tensor characterizing the plastic flow in the definition of the plastic flow rule, which becomes an assignment statement rather than an equilibrium equation. The above also means that the elastic and plastic factors in the multiplicative split of the deformation gradient are, in reality, gradients and that there is no problem with the continuum physics of elastoplastic deformations. The formulation is demonstrated in a numerical example using the regularized Mooney-Rivlin material model and modified equilibrium statements where the intermediate configuration is calculated, whose analysis results are compared with the identical material model using the current equilibrium statements. The advantages and disadvantages of each formulation, including their relationship with multiplicative plasticity, are also discussed.

Keywords: finite strain plasticity, continuum formulation, regularized Mooney-Rivlin material model, compatibility

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448 Timber Urbanism: Assessing the Carbon Footprint of Mass-Timber, Steel, and Concrete Structural Prototypes for Peri-Urban Densification in the Hudson Valley’s Urban Fringe

Authors: Eleni Stefania Kalapoda

Abstract:

The current fossil-fuel based urbanization pattern and the estimated human population growth are increasing the environmental footprint on our planet’s precious resources. To mitigate the estimated skyrocketing in greenhouse gas emissions associated with the construction of new cities and infrastructure over the next 50 years, we need a radical rethink in our approach to construction to deliver a net zero built environment. This paper assesses the carbon footprint of a mass-timber, a steel, and a concrete structural alternative for peri-urban densification in the Hudson Valley's urban fringe, along with examining the updated policy and the building code adjustments that support synergies between timber construction in city making and sustainable management of timber forests. By quantifying the carbon footprint of a structural prototype for four different material assemblies—a concrete (post-tensioned), a mass timber, a steel (composite), and a hybrid (timber/steel/concrete) assembly applicable to the three updated building typologies of the IBC 2021 (Type IV-A, Type IV-B, Type IV-C) that range between a nine to eighteen-story structure alternative—and scaling-up that structural prototype to the size of a neighborhood district, the paper presents a quantitative and a qualitative approach for a forest-based construction economy as well as a resilient and a more just supply chain framework that ensures the wellbeing of both the forest and its inhabitants.

Keywords: mass-timber innovation, concrete structure, carbon footprint, densification

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447 A Review on Design and Analysis of Structure Against Blast Forces

Authors: Akshay Satishrao Kawtikwar

Abstract:

The effect of blast masses on structures is an essential aspect that need to be considered. This type of assault could be very horrifying, who where we take it into consideration in the course of the design system. While designing a building, now not only the wind and seismic masses however also the consequences of the blast have to be take into consideration. Blast load is the burden implemented to a structure form a blast wave that comes straight away after an explosion. A blast in or close to a constructing can reason catastrophic harm to the interior and exterior of the building, inner structural framework, wall collapsing, and so on. The most important feature of blast resistant construction is the ability to absorb blast energy without causing catastrophic failure of the structure as a whole. Construction materials in blastprotective structures must have ductility as well as strength.

Keywords: blast resistant design, blast load, explosion, ETABS

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446 Finite Element Analysis of Hollow Structural Shape (HSS) Steel Brace with Infill Reinforcement under Cyclic Loading

Authors: Chui-Hsin Chen, Yu-Ting Chen

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Special concentrically braced frames is one of the seismic load resisting systems, which dissipates seismic energy when bracing members within the frames undergo yielding and buckling while sustaining their axial tension and compression load capacities. Most of the inelastic deformation of a buckling bracing member concentrates in the mid-length region. While experiencing cyclic loading, the region dissipates most of the seismic energy being input into the frame. Such a concentration makes the braces vulnerable to failure modes associated with low-cycle fatigue. In this research, a strategy to improve the cyclic behavior of the conventional steel bracing member is proposed by filling the Hollow Structural Shape (HSS) member with reinforcement. It prevents the local section from concentrating large plastic deformation caused by cyclic loading. The infill helps spread over the plastic hinge region into a wider area hence postpone the initiation of local buckling or even the rupture of the braces. The finite element method is introduced to simulate the complicated bracing member behavior and member-versus-infill interaction under cyclic loading. Fifteen 3-D-element-based models are built by ABAQUS software. The verification of the FEM model is done with unreinforced (UR) HSS bracing members’ cyclic test data and aluminum honeycomb plates’ bending test data. Numerical models include UR and filled HSS bracing members with various compactness ratios based on the specification of AISC-2016 and AISC-1989. The primary variables to be investigated include the relative bending stiffness and the material of the filling reinforcement. The distributions of von Mises stress and equivalent plastic strain (PEEQ) are used as indices to tell the strengths and shortcomings of each model. The result indicates that the change of relative bending stiffness of the infill is much more influential than the change of material in use to increase the energy dissipation capacity. Strengthen the relative bending stiffness of the reinforcement results in additional energy dissipation capacity to the extent of 24% and 46% in model based on AISC-2016 (16-series) and AISC-1989 (89-series), respectively. HSS members with infill show growth in 𝜂Local Buckling, normalized energy cumulated until the happening of local buckling, comparing to UR bracing members. The 89-series infill-reinforced members have more energy dissipation capacity than unreinforced 16-series members by 117% to 166%. The flexural rigidity of infills should be less than 29% and 13% of the member section itself for 16-series and 89-series bracing members accordingly, thereby guaranteeing the spread over of the plastic hinge and the happening of it within the reinforced section. If the parameters are properly configured, the ductility, energy dissipation capacity, and fatigue-life of HSS SCBF bracing members can be improved prominently by the infill-reinforced method.

Keywords: special concentrically braced frames, HSS, cyclic loading, infill reinforcement, finite element analysis, PEEQ

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445 Modelling of Structures by Advanced Finites Elements Based on the Strain Approach

Authors: Sifeddine Abderrahmani, Sonia Bouafia

Abstract:

The finite element method is the most practical tool for the analysis of structures, whatever the geometrical shape and behavior. It is extensively used in many high-tech industries, such as civil or military engineering, for the modeling of bridges, motor bodies, fuselages, and airplane wings. Additionally, experience demonstrates that engineers like modeling their structures using the most basic finite elements. Numerous models of finite elements may be utilized in the numerical analysis depending on the interpolation field that is selected, and it is generally known that convergence to the proper value will occur considerably more quickly with a good displacement pattern than with a poor pattern, saving computation time. The method for creating finite elements using the strain approach (S.B.A.) is presented in this presentation. When the results are compared with those provided by equivalent displacement-based elements, having the same total number of degrees of freedom, an excellent convergence can be obtained through some application and validation tests using recently developed membrane elements, plate bending elements, and flat shell elements. The effectiveness and performance of the strain-based finite elements in modeling structures are proven by the findings for deflections and stresses.

Keywords: finite elements, plate bending, strain approach, displacement formulation, shell element

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444 Barriers to E-Tendering Adoption and Implementation in the Ghanaian Construction Industry

Authors: Aynur Kazaz, Yusif Inusah

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In the bid to improve transparency and efficiency as well as to reduce the cost of the public procurement process, Ghana started implementing an electronic Government Procurement System, known as the Ghana Electronic Procurement System (GHANEPS) in November 2019. The implementation of e-tendering technology is new to the stakeholders. Therefore, this research is aimed to identify the critical barriers to e-tendering implementation in the Ghanaian construction industry. Examples of barriers to e-tendering implementation were first identified through a literature review, and questionnaires and interview questions were prepared to gather the data. This study contributes to the in-depth understanding of global e-tendering barriers in the Ghanaian construction industry. The findings could help researchers, practitioners, and governments make strategic investment decisions and overcome e-tendering challenges.

Keywords: barriers, challenges, construction industry, e-procurement, e-tendering

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443 Long Term Impact of Large Infrastructure Projects on Employment: Case Study of The Spanish High-Speed Rail

Authors: Dharashree Sahoo, Sudhir Misra

Abstract:

Large infrastructure projects such as roads, railways, airports etc. play a critical role in the economic development of a region, and are resource-intensive and therefore, need to be evaluated for their profitability in the long-term. High-speed rail (HSR) is a typical example of such projects and has attracted a lot of attention recently as many countries explore investing in HSR due to the variety of economic, social, and environmental benefits it offers. In this study, the Spanish HSR has been used as a case study. The Spanish Labour Force Survey (SLFS), which is carried out by the National Institute of Statistics (INE) and the results of which are available through IPUMS International, is the source of the data used in this study. The data spanning the years 2005 to 2019 has been taken for this analysis. The objective is to evaluate one facet of the economic profitability of HSR in terms employment generated in the short, the medium, and the long run, which have been taken as time spans of up to one year, one to ten years, and more than ten years, respectively, after the commencement of HSR operations for the purpose of this study. The operation of the HSR service is utilized as a treatment in this study, and a modified difference-in-differences (DiD) approach is used to analyze the influence that it has on job prospects over time throughout various cities in Spain. The conventional DiD methodology was modified to account for the fact that the commissioning of HSR stations in various cities of Spain took place in different years. As a result, the amount of time that HSR is operational in a specific city differs from the amount of time it is operational in other cities for any given year. Heterogeneity analysis has also been carried out by the location of stations i.e., whether a station is situated in the center of the city or in the periphery and how that affects the individual employment in short, mid and long run. It was found that:a) an individual living in a city that has a HSR station is more likely to be employed than his counterpart who lives in a city that does not have a HSR station, and this disparity between the probabilities is the highest in the long run. b) with the passage of time, individuals living in cities having peripheral stations have lower and lower probabilities of having employment when compared to individuals living in cities having a HSR station in the city center.

Keywords: employment, high-speed rail, impact evaluation, long term effects.

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442 Policies Promoting the Development of Green Buildings in Sub-Saharan Africa: A South African Case-Study

Authors: Peter Adekunle, Clinton Aigbavboa, Matthew Ikuabe, Opeoluwa Akinradewo

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Contemporary building methods typically pay little attention to the built environment's greater economic, environmental, or social impacts or energy efficiency. Green construction aims to sever ties with these conventions. In order to provide better living and working conditions and lessen environmental consequences, green building today combines numerous building design, construction, and operation and maintenance approaches. As one of Sub-Saharan Africa's most industrialized nations, South Africa has a good number of green building projects. Therefore, this study examines the elements impacting the adoption of green buildings and regulations created to encourage the growth of green buildings using South Africa as a case study. The study has a survey-style design. A total of one hundred fifty (150) questionnaires were distributed to professionals in the construction industry in South Africa, of which one hundred and twenty-four (128) were returned and judged appropriate for investigation. The gathered data was examined using percentage, mean item scores, standard deviation, and Kruskal-Wallis. The findings show that cost and market circumstances are the two main elements impacting the adoption of green construction, while leadership advice is the most important policy. The study concluded that in order to encourage the construction of green buildings, additional Sub-Saharan nations should adopt these suggested policies.

Keywords: green building, Sub-Saharan Africa, building design, environmental conditions

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441 Evaluating the Implementation of Machine Learning Techniques in the South African Built Environment

Authors: Peter Adekunle, Clinton Aigbavboa, Matthew Ikuabe, Opeoluwa Akinradewo

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The future of machine learning (ML) in building may seem like a distant idea that will take decades to materialize, but it is actually far closer than previously believed. In reality, the built environment has been progressively increasing interest in machine learning. Although it could appear to be a very technical, impersonal approach, it can really make things more personable. Instead of eliminating humans out of the equation, machine learning allows people do their real work more efficiently. It is therefore vital to evaluate the factors influencing the implementation and challenges of implementing machine learning techniques in the South African built environment. The study's design was one of a survey. In South Africa, construction workers and professionals were given a total of one hundred fifty (150) questionnaires, of which one hundred and twenty-four (124) were returned and deemed eligible for study. Utilizing percentage, mean item scores, standard deviation, and Kruskal-Wallis, the collected data was analyzed. The results demonstrate that the top factors influencing the adoption of machine learning are knowledge level and a lack of understanding of its potential benefits. While lack of collaboration among stakeholders and lack of tools and services are the key hurdles to the deployment of machine learning within the South African built environment. The study came to the conclusion that ML adoption should be promoted in order to increase safety, productivity, and service quality within the built environment.

Keywords: machine learning, implementation, built environment, construction stakeholders

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440 Feasibility Studies in Public Construction Projects in South Africa: Barriers and Implications

Authors: Kenneth O. Otasowie, Matthew Ikuabe, Clinton Aigbavboa, Ayodeji Oke

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The practice of feasibility studies plays a huge role in the success of construction projects. Feasibility studies according to several research should be the reason for embarking on any project. However, it has been discovered that in South Africa (SA), feasibility studies are mainly done in the private sector construction but skipped in the construction of most public projects. Hence, this study aims to evaluate the barriers to feasibility studies practice in public projects and the implications. A survey design was adopted. A total number of One hundred and fifty (150) questionnaires were administered to Quantity Surveyors, Construction managers, Construction project managers, Project managers, Architects and Civil and Structural engineers in Guateng Province, SA and ninety (90) were returned and found suitable for analysis. Collected data was analysed using percentage, mean item score, standard deviation, one-sample t-test. The findings show that political interference and corruption are the most significant barriers to feasibility studies practice in the public construction projects in SA, while late project completion, poor quality infrastructure are among the implication of not conducting feasibility studies in SA public projects. Therefore, the study recommends the development of a framework for public projects execution that will reduce the interference of the political class in the country, that way the risk of late project completion and poor quality infrastructure will be mitigated.

Keywords: arriers, feasibility studies, public construction, South Africa.

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439 Appraisal of Transaction Cost in South African Construction Projects

Authors: Kenneth O. Otasowie, Matthew Ikuabe, Clinton Aigbavboa, Ayodeji Oke

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Construction project cost are not only made up of production costs. This cost comprises of many other elements such as the preparation of a bidding document, cost estimations, drafting contractual agreements and monitoring that contractual obligations are met. Several studies have stressed the need for transaction costs (TC) to be defined in a way that covers all phases of a project and not only the pre-contract phase. Hence, this study aims to appraise transaction cost in South African (SA) construction projects by assessing what constitutes transaction cost, influencing factors and possible optimisation measures. A survey design was adopted. A total number of eighty (80) questionnaires were administered to quantity surveyors, procurement managers and project managers in Guateng Province, SA and seventy-two (72) were returned and found suitable for analysis. Collected data was analysed using percentage, mean item score, standard deviation, one-sample t-test. The findings show that external technical interaction, uncertainty, human factors are the most significant constituents of TC in SA, while technical competency, experience in similar project type and project characteristics are the leading influencing factors. Furthermore, understanding project characteristics, clear communication and technically competent project teams are most of the significant measures for optimising TC in SA construction projects. Therefore, this study recommends that a competent project team and a clear communication are fundamental to proper management of TC in SA construction projects.

Keywords: construction projects, project cost, South Africa, transaction cost

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438 Barriers to Health and Safety Practices in South African Construction Industry: Subcontractors Perspective

Authors: Kenneth O. Otasowie, Matthew Ikuabe, Clinton Aigbavboa, Ayodeji Oke

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Subcontracting has become a fundamental feature in the construction industry, particularly as most projects in South Africa (SA) are executed by subcontractors. However, the sector in SA contributes to the high level of occupational hazards and injuries recorded, despite Health and Safety (H&S) regulations being enforced in the industry. Hence, this study aims to evaluate the barriers to health and safety practices by subcontractors in SA Construction Industry. A survey design was adopted. A total number of one hundred and forty-four (144) questionnaires were administered to quantity surveyors, construction managers, construction project managers, project managers, architects, and civil and structural engineers, who are owners or work in small and medium enterprises in Guateng Province, SA and eighty-three (83) were returned and found suitable for analysis. Collected data were analysed using percentage, mean item score, standard deviation, and one-sample t-test. The findings show that lack of skilled workers, lack of safety training, and insufficient safety awareness are the most significant barriers to health and safety practices in SA Construction Industry. Therefore, the study recommends the improvement in skills of staff and adequate training for the safe execution of work be provided to all employees and supervisors in these subcontracting firms. These will mitigate the rate of accident occurrence on construction sites.

Keywords: barriers, health and safety, subcontractors, South Africa

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