Research



Nguyen Dang Khoa, Msc

Email: dangkhoa@lhu.edu.vn

Employment: Lecturer, Faculty of Civil Engineering, Lac Hong University, Viet Nam

1. Limit Analysis Solutions for Stability Factor of Unsupported
Conical Slopes in Clays with Heterogeneity and Anisotropy
, International Journal of Computational Materials Science and Engineering, Dec 2021.

Abstract: The novel stability solution of unsupported conical slopes in anisotropic and nonhomogeneous clay utilizing lower bound (LB) and upper bound (UB) finite element limit analyses (FELA) are proposed in this paper. The anisotropic undrained shear (AUS) model and linear increasing undrained shear strengths are employed to determine the anisotropic and nonhomogenous soil behaviour respectively. The stability factor N is obtained with the variation of dimensionless parameters including the ratio of anisotropic (re), the rate of increasing undrained shear strength (m), the ratio between the height and the radius at bottom slope (H/b) and the inclination angle of slope (b) provided in sample charts. The failure patterns of conical slopes considering the effected parameters are also performed and described.

Keywords: Unsupported conical slope, Lower bound and Upper bound analysis, Anisotropic and nonhomogeneous clays, Stability.

2. Vertical Uplift Capacity of Circular Anchors in Clay by Considering Anisotropy and Non-Homogeneity, Transportation Infrastructure Geotechnology, Aug 2021.

Abstract: New numerical analyses of the vertical uplift capacity of circular anchors embedded in anisotropic and non-homogenous clay are presented in this paper. These analyses are derived based on the lower bound and upper bound finite element limit analysis under an axisymmetric condition. The anisotropic undrained shear (AUS) failure criterion is applied in these analyses. The undrained shear strength of clay increases linearly with depth. The anisotropy is adopted by changing of the ratios between undrained shear strengths determined from triaxial compression test and extension test. The variation of uplift factor (Fc) and shape of failure pattern with three parameters including embedment ratio (H/B), ratio of increasing undrained shear strength with depth (m), and the ratio of anisotropic parameters (re) are verified and investigated. These analyses will provide reliable results in order to improve the engineering calculation for plate anchor embedded in anisotropic and non-homogenous clays.

Keywords: Uplift capacity · Anchor · Anisotropic · Non-homogenous · Limit
analysis.

3. Analyzing the Influence of Diaphragm Wall on the Bending Moment and Settlement of Pile Raft Foundation, Journal of Science of Lac Hong University, Jun 2020.

Abstract: Assessing the degree of influence of the diaphragm wall on the bending moment and settlement of pile raft foundation is very necessary in foundation design. In this studying, finite element method (Plaxis 3D) was employed to analyze the behavior of pile raft foundation for a real project, which the pile raft was opted for foundation design solution. The raft was in the medium dense sand layer of Ho Chi Minh geological stratum. The investigated cases included: The pile raft foundation didn’t consider the influence of the diaphragm wall and considering the influence level of the diaphragm wall in several cases of different stiffness of connected plate between raft and diaphragm wall. The results showed that the settlement of raft raft was reduced by 12%, axial load of pile decreased by 18% considering the influence of the diaphragm wall. And the stiffness of connected plate did not significantly affect the settlement and moment of raft and axial load of pile at the raft central.  

Keywords: Diaphragm wall; pile raft foundation; influence on the bending moment; axial load of pile.

4. Finite Element Modeling of Concrete-Filled Double Steel Tubular Column under Axially Compression, Viet Nam Journal of Science and Technology, Jun 2020.

Abstract: Concrete-filled double skin steel tubular columns (CFDST) have drawn many attractions from research community, as they are promising in construction of bridges and buidings. CFDST column is a composite structure that has one concrete core being confined by one steel layer inside and one steel layer outside. Compared with CFST columns, the structure of CFDST columns has lower self-weight, while the confinement effect, which helps to increase compressive strength of concrete, is preserved. In this paper, a simple finite element model is developed, based on the software ABAQUS, to analyze the non-linear behavior of CFDST columns under axial compression. The current model is used to analyze the behaviour of two types of CFDST columns: straight columns and tapered columns. Results obtained by the present model is compared with experimental data reported by other authors in literatures, showing good agreement.

Keywords: Concrete-filled double skin steel tubular columns, CFDST, confinement effect, axial compressive load capacity, finite element model.

5. Enhance Effectiveness when using MS Project in Management of Construction Project Bridge and Highway, Vietnam Journal of Bridge and Road, 2019.

Abstract: Today, MS Project software is widely used in scheduling and construction management in Viet Nam. But there are propleMS, MS Project  offers do not suit the way people work and understand the management of construction projects in Viet Nam; such as: overtime work and the cost be calculated by MS Project. Users need to understand the correct management of their work accurately delivers high efficiency in the process of the construction project management.

Keywords: Transportation  project, scheduling, project management.

6. Enhance Effectiveness when using MS Project 2007 in the Establishment Scheduling and Management of Construction Project, Vietnam Journal of Bridge and Road, 2018.

Abstract: A new highlight in MS Project 2007 is the feature that allows users to present reports in the form of charts and graphs. However, users need to understand the calculation part of MS Project for effective management.

MS Project 2007 has many advantages but also MS project outputs are not suitable for use in construction project management in Vietnam. In this article, the authors will share their certain knowledge about MS Project 2007 for individuals who have the need to use MS Project in construction schedule and project management, in order to bring about the effectiveness of the project. the use of MS Project software in your work.

Keywords: Construction  project, scheduling, project management.

7. Nonlinear Static Procedures for Estimating Seismic Demands of Buckling-Restrained Braced Frames, Journal of Science of Lac Hong University, 2017.

Abstract: An essential component of evolving performance-based design methodologies is the accurate estimation of seismic demand parameters. Nonlinear static procedures (NSPs) are now widely used in engineering practice to predict seismic demands in building structures. This paper aims to investigate comparatively the bias and accuracy of adaptive modal combination (AMC), modal pushover analysis (MPA) and standard pushover analysis (SPA) procedures when they are applied to buckling-restrained braced frame (BRBF) buildings. Three-, 6-, 10-, and 14-storey concentrically BRBF buildings were analyzed due to two sets of strong ground motions having 2% and 10% probability of being exceeded in 50 years. The assessment is based on comparing seismic displacement demands such as target roof displacements, peak floor/roof displacements and inter-storey drifts. The NSP estimates are compared to results from nonlinear response history analysis (NL-RHA). The response statistics presented show that the AMC, MPA procedures can accurately estimate critical demand parameters such as roof displacement and interstory drift while the SPA can reasonably use in low buildings. Moreover, the AMC tends to more consistently estimate seismic demands than the other NSPs investigated in the study especially at lower stories of tall buildings.

Keywords: buckling-restrained braced frame (BRBF), Nonlinear static procedures (NSPs), adaptive modal combination (AMC), modal pushover analysis (MPA), standard pushover analysis (SPA), nonlinear response history analysis (NL-RHA).

8. Factors Resulting in Conflicts of Transportation Project, Vietnam journal of Bridge and Road, 2017.

Abstract: This paper presents, analyzing the factors causing conflict in the process of transportation  projects. Research results can make reference to the investors,  project  management, construction units and units set up consultancy projects, the state management agencies and individuals and units related to the transportation  projects in determining the factors  causing conflict during project execution, to take measures to prevent conflict in order to  improve  the  efficiency of project implementation.

Keywords: Transportation  project, influence, conflict, the project implementation.

9. An application of Earned Value Method in Transportation Project Management, Vietnam journal of Bridge and Road, 2016.

Abstract: Earned Value Method (EVM) is analyze cost/schedule analysis method. Analyzing Earned Value is a system of measuring the specific implementation of project management. It assesses the situation objectively to assist analyzers to forecast and alert the project status. EVM also provides a whole picture of the project. This paper provides the basis of EVM and a practical application in Vietnam.

Keywords: Project, Earned value, Transportation Project Management.

11. Analyze Post-Tension Mat Foundation Structures on Elastic Background, Journal of Science of Lac Hong University, 2015.

Abstract: The  prestressing  force  is  sized  in  general  for  precompression  requirements  and/or  load  balancing criteria. Practical experience recommends effective prestress values in the range from 0,75  to  1,5  MPa,  balancing  50%  to  100%  of  the  permanent  loads.  The  proposed  values  are generally  appropriate  to  control  slab  deflections and  improve  punching  shear  resistance,  being moderate enough to avoid excessive camber or slab shortening. Analyse the influence of prestressing  force on uniform  soil  pressure  distribution when we change subgrade reaction in the diffirent cases of load balancing force to correspond with subgrade factor.

Keywords: Post-tension mat foundation; Balancing force; Subgrade reaction.


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