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Effect of Contractor – Subcontractor Relationship on the Performance of Construction Project: A Case Study of Dire Dawa Construction Projects
Elias Defalgn Debelo,
Zerihun Berhane Weldegebriel
Issue:
Volume 10, Issue 2, March 2022
Pages:
31-42
Received:
21 February 2022
Accepted:
1 April 2022
Published:
9 April 2022
Abstract: Because of the common practice of subletting construction work into smaller packages, subcontracting has become an attractive technique in the construction business. Effective subcontractor selection and monitoring reduce the problem while also determining the performance of construction firms. The engagement of a subcontractor in a building construction project results in relationships with the main contractor, which will influence the project's success. The purpose of this study was to look at how main contractors choose subcontractors and to analyze the effect of the main contractor–subcontractor relationship on project performance. This research used a descriptive survey method to look at the underlying characteristics that influence the relationship between the main contractor and subcontractors and their effect on the performance of construction projects. The findings of the study confirmed that most contractor depends on subcontractors for the execution of their work and therefore procurement and management of subcontractors highly affects the performance of the construction project. It was also discovered that the subcontractor often performs 20 percent to 50 percent of the work. Main contractors used subcontractors primarily to offer skilled labor, lower overhead expenses, and relieve work and financial burden on themselves. The major causes of issues between the main contractor and the subcontractor include the main contractor's delay in releasing payments, the subcontractor's shortage of trained personnel, and scheduling conflicts among the subcontractors on a given project. To eliminate antagonistic relationships, the study advises a trust-based cooperative partnership that incorporates subcontractors into a partnering strategy. Furthermore, for optimal construction project performance, simpler and complete subcontract documents would improve the interaction between the main contractor and the subcontractor.
Abstract: Because of the common practice of subletting construction work into smaller packages, subcontracting has become an attractive technique in the construction business. Effective subcontractor selection and monitoring reduce the problem while also determining the performance of construction firms. The engagement of a subcontractor in a building constr...
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Stability Analysis of Tunnel by External Force Increment Method
Issue:
Volume 10, Issue 2, March 2022
Pages:
43-48
Received:
5 March 2022
Accepted:
11 April 2022
Published:
20 April 2022
Abstract: A new tunnel stability analysis method is proposed which is the external force increment method (EFIM) to transform the traditional tunnel stability ratio (N). The EFIM can be defined as the field stability raito (Nf), which consists of two newly defined parameters, namely the natural stability ratio (Nn) and the critical stability ratio (Nc). The relationship between the field stability ratio (Nf) and the change of external force is given. The tunnel stability plane and tunnel stability analysis plot are constructed. Based on this, the relationship between the field stability ratio (Nf) and the critical stability ratio (Nc) when the initial tunnel is stable or unstable is determined. According to the field stability rate (Nf), the critical stable state can be achieved with the tunnel by increasing two ways: one is to increase the external load to act on the external force on the tunnel, and the other is to reduce the internal support force of the tunnel. The relations for reaching the critical stability ratio (Nc) of the two EFIM are given respectively. The upper bound solutions of single tunnel, twin tunnels with the same diameter and twin tunnels with different diameters are analyzed by this method. The results show that the EFIM is reasonable and feasible for stability analysis of tunnel.
Abstract: A new tunnel stability analysis method is proposed which is the external force increment method (EFIM) to transform the traditional tunnel stability ratio (N). The EFIM can be defined as the field stability raito (Nf), which consists of two newly defined parameters, namely the natural stability ratio (Nn) and the critical stability ratio (Nc). The ...
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Elastic-plastic Buckling Analysis of Q690 High Strength Steel Tubes Under Global Bending
Kapnang Franky,
Lei Chen,
Du Mengxing,
Ngalle Itoumbou Christina Joyce
Issue:
Volume 10, Issue 2, March 2022
Pages:
49-54
Received:
18 April 2022
Published:
20 April 2022
Abstract: In recent years, high-strength steel has been used extensively for infrastructures because of its many advantages, such as its ductility and strain-hardening properties, which are inferior to those of ordinary structural steel, and the small dimensions of the structural elements, which lead to greater freedom and elegance in design, resulting in lighter structures. In practice, imperfections such as residual stresses due to the welding process and pre-buckling mode imperfections are inevitable in cylindrical structures made of high-strength steel. A small imperfection amplitude can lead to a disproportionate reduction in buckling strength. Therefore, imperfection sensitivity should be considered when studying the buckling behaviour of the shell. The influence of the combined residual stress and pre-buckling mode imperfection on the buckling behaviour of Q690 high strength steel cylindrical shell under global bending has not yet been investigated and described for all dimensions. In this paper, the combined imperfections influences on the buckling behaviour of high-strength steel cylindrical shell in global bending in the elastic-plastic range are investigated. Using the ABAQUS fine elements software, perfect cylinders with a constant length to thickness ratio equal to 7 and a radius to thickness ratio in the range 10≤ r/t ≤700 were considered to perform the linear bifurcation analysis (LBA) and the geometric nonlinear analysis (GNA). The non-linear analysis with imperfections (GNIA) and the geometric and material non-linear analysis with imperfections (GMNIA) were then performed considering imperfection amplitudes between 0.01 and 2 to derive the critical buckling loads known as bifurcation point for the models with different aspect ratio. The influences of the combined imperfections show that moderately and very thin cylinders are very sensitive to the increase of the pre-buckling mode imperfection amplitude and their buckling strength is insensitive to plasticity. For thick cylinders, the effect of plasticity is more consistent, while the buckling strength is not significantly affected by the increase in pre-buckling mode imperfection amplitude. The main objective is to predict the buckling sensitivity of cylinders under the influence of combined residual stress and pre-buckling mode imperfection. The obtained results, comments and conclusions intend to allow for safer.
Abstract: In recent years, high-strength steel has been used extensively for infrastructures because of its many advantages, such as its ductility and strain-hardening properties, which are inferior to those of ordinary structural steel, and the small dimensions of the structural elements, which lead to greater freedom and elegance in design, resulting in li...
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The Effect of the Expected Time-to-Purchase on the Acceptable Price Premium for Green Buildings
Shoshi Ofek,
Andrea Ghermandi,
Boris Portnov
Issue:
Volume 10, Issue 2, March 2022
Pages:
55-63
Received:
13 February 2022
Accepted:
7 March 2022
Published:
20 April 2022
Abstract: Green buildings help to mitigate the impacts of construction on the environment by reducing the use of natural resources and limiting the emission of air pollutants associated with building construction and maintenance. Homebuyers who understand the life-cycle benefits of green buildings (such as lower operating costs, better indoor environment and reduced environmental impacts) are often willing to pay an additional price premium for such buildings. Although several studies examined the factors affecting the acceptable size of green building price premium, how the expected time to home purchase might affect the acceptable size of such premium remains unexplored. Here, we attempt to answer this question by using data from a countrywide survey carried out in Israel, in which responses from 390 potential homebuyers were collected and analyzed. We find that the willingness to pay a price premium for green buildings changes significantly with time to purchase and is the lowest for respondents who state that they do not plan to buy a home anytime in the near future. We explain this rather unexpected result by arguing that people who have no immediate home buying intention, might have only limited knowledge about contemporary housing market trends and thus do not consider green building as a viable alternative to traditional construction.
Abstract: Green buildings help to mitigate the impacts of construction on the environment by reducing the use of natural resources and limiting the emission of air pollutants associated with building construction and maintenance. Homebuyers who understand the life-cycle benefits of green buildings (such as lower operating costs, better indoor environment and...
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Nonlinear Stability Analysis of Elastic High Strength Steel Tubes Under Global Bending
Ngalle Itoumbou Christina Joyce,
Lei Chen,
Kapnang Franky
Issue:
Volume 10, Issue 2, March 2022
Pages:
64-69
Received:
26 April 2022
Published:
28 April 2022
Abstract: A recent computational study has found unique zones of stability behaviour in elastic High-strength steel tubes under global bending with different geometrical lengths. A situation under which the most compressed fiber approaches the buckling stress for uniform axial compression is the initial estimation of elastic buckling strength in bending. Cylinders with sufficient length develop a fully developed ovalization of the cross-section and fail by local buckling around the Brazier prediction. Under global bending regimes, typical buckles are fairly modest and extend across a very tiny region, accompanied by global bending extending the crucial value. The situation under which the major compressed fiber approaches the buckling stress for compression bending is the initial estimate of the elastic buckling strength in bending. In this study, the nonlinear behavior of short to long tubes under global bending is studied, with specific and different dimensions, radius-to-thickness ratios, and boundary conditions according to Europe an Standard 1993-1-6. Both the crucial buckling Eigenmode and the geometrically nonlinear elastic analysis are investigated. Because of a buckling stress state dominated by local harmony bending, it is confirmed that the cylinder length takes part in a crucial part in finding this behavior. A failure behavior of this type of material is then going to be investigated.
Abstract: A recent computational study has found unique zones of stability behaviour in elastic High-strength steel tubes under global bending with different geometrical lengths. A situation under which the most compressed fiber approaches the buckling stress for uniform axial compression is the initial estimation of elastic buckling strength in bending. Cyl...
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Assessment of Stabilized Earth Blocks (STEB) Strength to Sandcrete Blocks Used in Housing Construction
Ezemerihe Anthony Nnamdi,
Nnadi Ezekiel Oluwaseun Ejiofor,
Okwu-Delunzu Virginia Ugoyibo
Issue:
Volume 10, Issue 2, March 2022
Pages:
70-78
Received:
15 March 2022
Accepted:
31 March 2022
Published:
28 April 2022
Abstract: Shelter has been considered as the basic physiological need of a man after food and clothing. The use of stabilized earth soil as construction materials have solved and sustained the housing need of most communities because of its affordability prior to the use of the recent sandcrete block work in our modern construction technology. The research work aimed at collecting and running test samples of red earth soils at minimum of five different location i.e. one per state in the south eastern geopolitical zone of Nigeria, to carry out comparative analysis of stabilized red earth soil blocks and sancrete blocks’ strength in the each of the five states of south east as materials for walls in housing construction. The test samples were mixed with ordinary Portland cement and water at stated proportion, moulded and cured for fourteen (14) days. The weight, force and compressive strength of each of these blocks were tested at seven (7) days, fourteen (14) days, twenty one (21) days and twenty-eight (28) days. This is to ascertain the rate at which they gain strength and their ultimate strength in twenty-eight (28) days. The test sampled crushed at standard organization of Nigeria (SON) workshop laboratory at Enugu Office. The result of the compressive strength shows that all the tested samples attained above 1.50N/mm2 at twenty-eight (28) days but varies with the selected collection sample location. The graph/histogram of their respective weight, force and strength were plotted against period of gaining strength. The result also shows that the stabilized earth blocks with mix proportion of 1:12 yield twice the quantity of blocks compared to solid sandcrete blocks (SSB). The strength of the stabilized earth blocks (STEB) compared favourably to solid sancrete blocks (SSB) and can be used as substitute for housing construction for low income group in the area.
Abstract: Shelter has been considered as the basic physiological need of a man after food and clothing. The use of stabilized earth soil as construction materials have solved and sustained the housing need of most communities because of its affordability prior to the use of the recent sandcrete block work in our modern construction technology. The research w...
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