Badie S.S.,George Washington University |
Morgan Girgis A.F.,E.construct United States LLC |
Tadros M.K.,University of Nebraska - Lincoln |
Nguyen N.T.,Ho Chi Minh City University of Architecture
Journal of Bridge Engineering | Year: 2010
The AASHTO LRFD Bridge Design Specifications state that the spacing between the shear connectors for steel girders should not exceed 610 mm (24 in.). This decision was made based on research conducted more than three decades ago. The goal of this research is to investigate the possibility of extending this limit to 1,220 mm (48 in.) for stud clusters used with full-depth precast concrete deck panels installed on steel girders. This paper presents the history of the 610 mm (24 in.) limit, various formulas developed to calculate fatigue and design capacity for stud clusters and concerns about extending the current LRFD limit. This paper also presents information on the first phase of the experimental investigation, which is conducted on push-off specimens to validate extending the limit to 1,220 mm (48 in.). © 2010 ASCE.
Nguyen V.-H.,Ho Chi Minh City University of Architecture |
Remond S.,University of Lille Nord de France |
Gallias J.-L.,Cergy-Pontoise University
Cement and Concrete Research | Year: 2011
The influence of water to cement ratio, HRWRA content and viscosity modifying admixture content on the rheological characteristics of cement grouts considered as Herschel-Bulkley fluids is studied experimentally. Results show that cement grouts without chemical admixtures and cement grouts containing only a viscosity modifying admixture present a shear-thinning behaviour with an approximately constant value for the exponent n of Herschel-Bulkley model. On the contrary, grouts containing a HRWRA content near the saturation point exhibit quasi Binghamian behaviour. The Herschel-Bulkley model describes properly the rheological behaviour of cement grouts without chemical admixtures. It can be applied correctly to grouts containing HRWRA and/or viscosity modifying admixture in a shear rate range comprised between 4 s- 1 and 100 s- 1 and can be used to predict satisfactorily the Marsh cone flow time of cement grouts of widely varying compositions. © 2010 Elsevier Ltd. All rights reserved.
Dao N.D.,Ho Chi Minh City University of Architecture |
Ryan K.L.,University of Nevada, Reno
Journal of Structural Engineering (United States) | Year: 2014
A full-scale earthquake simulation of a five-story steel moment frame building at E-Defense, the world's largest single shake table facility in Miki, Japan, in August 2011 provided realistic data to improve and validate current modeling approaches for steel structures with composite floor systems. In this paper, computational models of the tested fixed-base specimen and the specimen isolated with triple pendulum bearings were developed and validated using the test data, and the influence of various modeling assumptions on the accuracy of the numerical prediction was investigated. The results demonstrate that the displacement of the isolation system can be predicted accurately without a well calibrated superstructure model. However, the response of the isolated structure, especially when subjected to 3-dimensional motions, is quite sensitive to the frame modeling assumptions and the superstructure damping model. The modeling assumptions that most accurately predict the response of the tested specimen are described in this paper. © 2014 American Society of Civil Engineers.
Vu T.-V.,Ho Chi Minh City University of Architecture |
Lee H.-E.,Korea University |
Bui Q.-T.,University of Siegen
Structural Engineering and Mechanics | Year: 2012
This paper presents a spatial catenary cable element for the nonlinear analysis of cablesupported structures. An incremental-iterative solution based on the Newton-Raphson method is adopted for solving the equilibrium equation. As a result, the element stiffness matrix and nodal forces are determined, wherein the effect of self-weight and pretension are taken into account. In the case of the initial cable tension is given, an algorithm for form-finding of cable-supported structures is proposed to determine precisely the unstressed length of the cables. Several classical numerical examples are solved and compared with the other available numerical methods or experiment tests showing the accuracy and efficiency of the present elements.
Valizadeh N.,Bauhaus University Weimar |
Bui T.Q.,University of Siegen |
Vu V.T.,Ho Chi Minh City University of Architecture |
Thai H.T.,Hanyang University |
Nguyen M.N.,Ruhr University Bochum
International Journal of Applied Mechanics | Year: 2013
Buckling, free and forced vibration analyses of orthotropic plates are studied numerically using Isogeometric analysis. The present formulation is based on the classical plate theory (CPT) while the NURBS basis function is employed for both the parametrization of the geometry and the approximation of plate deflection. An efficient and easy-to-implement technique is used for imposing the essential boundary conditions. Numerical examples for free and forced vibration and buckling of orthotropic plates with different boundary conditions and configurations are considered. The numerical results are compared with other existing solutions to show the efficiency and accuracy of the proposed approach for such problems. © 2013 Imperial College Press.
Ryan K.L.,University of Nevada, Reno |
Dao N.D.,Ho Chi Minh City University of Architecture
Journal of Structural Engineering (United States) | Year: 2016
This paper focuses on a horizontal-vertical coupling effect observed in a full-scale shake table experiment of a 5-story moment frame building isolated with triple pendulum bearings. A significant increase or amplification of the horizontal floor accelerations was observed during three-dimensional (3D) shaking compared to XY (horizontal only) shaking with comparable input motions. The coupling phenomenon is explained by analytical and numerical simulation of a single degree-of-freedom (rigid mass) structure and multistory cantilever structure subjected to simplified sinusoidal motions, both isolated with triple pendulum bearings. The results of the simplified numerical study are extended to explain the horizontal-vertical coupling in the full-scale experiment, which are also validated by numerical modeling of the test structure. The vertical component of ground acceleration is shown to introduce a high-frequency component into the base shear that can excite higher modes of the base-isolated structure. The phenomenon is possible in any multistory structure isolated with friction bearings, and should be evaluated on a case-by-case basis. © 2015 American Society of Civil Engineers.
Nam J.-H.,Korea University |
Le T.-H.,Ho Chi Minh City University of Architecture
Journal of Marine Science and Technology (Japan) | Year: 2012
The interior of superyachts is either designed by an expert or modeled on previous layouts that have been successfully designed. Changing one arrangement to the other is challenging and has not been tried without the buyer's request, mostly dissuaded by the current manual design procedure. In this work, an approach to determine the interior space arrangement is introduced. Space arrangement is performed by considering various design constraints that are expressed in terms of numerical values such as space occupation, shapes of spaces, and distance of stairs connecting relevant spaces, and a combination of those. The genetic algorithm is adopted to yield the space arrangement formulated as an optimization problem containing multiple objectives. The solution to the space arrangement problem has proven that the designer is able to generate a specific result due to the degree of freedom allowed by the formulation. The proposed design approach has led to efficient layouts for general arrangement of mid-sized superyachts. These possible candidates help the designer to choose a right arrangement based on his or her design concept or intention, which will make the interior arrangement task much easier and faster. © 2012 JASNAOE.
Tran P.V.,Kanazawa University |
Tran P.V.,Ho Chi Minh City University of Architecture |
Maegawa K.,Kanazawa University |
Fukada S.,Kanazawa University
Computers and Geotechnics | Year: 2013
This study uses a numerical procedure, previously validated with data from full-scale experiments, to investigate the performance of a modified prototype wire-rope fence to provide protection against rockfall. The cost-reducing modifications are increased post spacing and fewer wire netting layers. The numerical procedure provides the nonlinear response of the prototype under various impact conditions and insights into each component's role in dissipating impact energy. A simple but effective method to increase fence capacity is also developed. Finally, the use of two units of the prototype to protect a wide area is investigated employing the numerical procedure. © 2013 Elsevier Ltd.
Nguyen L.D.,Florida Gulf Coast University |
Nguyen H.T.,Ho Chi Minh City University of Architecture
Construction Research Congress 2012: Construction Challenges in a Flat World, Proceedings of the 2012 Construction Research Congress | Year: 2012
Construction activities are repetitive from floor to floor in multistory building construction. Labor productivity may neither reach 100 percent of the normal level at the very first floors nor the very top floors. Nevertheless labor productivity may follow a certain pattern as construction activities progress. This research aims at exploring the relationship between floor number and labor productivity in multistory structural activities, namely formwork installation and rebar fabrication/installation. The case study methodology and learning curve theory are adopted for this research. Records from the structural works of an apartment building were analyzed to calculate floor number-based labor productivities for the two investigated activities. The unit rate of the formwork activity reduced more than 50 percent in the first five floors. If the first cycle (floor 2) is omitted, the straight-line learning curve model shows a learning rate of 83.5%. Productivity of the formwork activity tended to level off in the remaining thirteen floors. The unit rate of the rebar activity was prone to reduce in the first fifteen floors. If the first two cycles are omitted, the straight-line learning curve model indicates a learning rate of 83.6%. If only the first cycle is omitted, the learning rate of the rebar activity is 87.9%. Productivity of the rebar activity tended to decrease in the last three top floors though data points were not adequate to confirm such pattern. © 2012 ASCE.
Lan T.T.H.,Ho Chi Minh City University of Architecture
Jordan Journal of Civil Engineering | Year: 2013
The approximate solutions of stresses and displacements were obtained for fixed-fixed anisotropic beams subjected to uniform load. A stress function involving un-known coefficients was constructed, and the general expressions of stress and displacement were obtained by means of airy stress function method. Two types of the description for the fixed end boundary condition were considered. The introduced unknown coefficients in stress function were determined by using the boundary conditions. The approximate solutions for stresses and displacements were finally obtained. Numerical tests show that the solutions agree with the FEM results. These solutions are achieved by using Maple software. © 2013 JUST. All Rights Reserved.