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Showing 9 results for Tu

K. J. Tu, Y. W. Huang,
Volume 11, Issue 4 (Transaction A: December 2013)
Abstract

The decisions made in the planning phase of a building project greatly affect its future operation and maintenance (O&M) cost. Recognizing the O&M cost of condominiums’ common facilities as a critical issue for home owners, this research aims to develop an artificial neural network (ANN) O&M cost prediction model to assist developers and architects in effectively assessing the impacts of their decisions made in the planning phase of condominium projects on future O&M costs. A regression cost prediction model was also developed as a benchmark model for testing the predictive accuracy of the ANN model. Six critical building design attributes (building age, number of apartment units, number of floors, average sale price, total floor area, and common facility floor area) which are usually available in the project planning phase, were identified as the input factors to both models and average monthly O&M cost as the output factor. 55 of the 65 existing condominium properties randomly selected were treated as the training samples whose data were used to develop the ANN and regression models the other ten as the test samples to compare and verify the predictive performance of both models. The study results revealed that the ANN model delivers more accurate and reliable cost prediction results, with lower average absolute error around 7.2% and maximum absolute error around 16.7%, as compared with the regression model. This study shows that ANN is an effective method in predicting building O&M costs in the project planning phase. Keywords: Project management, Facility management, Common facilities, Cost modeling.
H. Shahnazari, M. A. Shahin, M. A. TuTunchian,
Volume 12, Issue 1 (Transaction B: Geotechnical Engineering, January 2014)
Abstract

Due to the heterogeneous nature of granular soils and the involvement of many effective parameters in the geotechnical behavior of soil-foundation systems, the accurate prediction of shallow foundation settlements on cohesionless soils is a complex engineering problem. In this study, three new evolutionary-based techniques, including evolutionary polynomial regression (EPR), classical genetic programming (GP), and gene expression programming (GEP), are utilized to obtain more accurate predictive settlement models. The models are developed using a large databank of standard penetration test (SPT)-based case histories. The values obtained from the new models are compared with those of the most precise models that have been previously proposed by researchers. The results show that the new EPR and GP-based models are able to predict the foundation settlement on cohesionless soils under the described conditions with R2 values higher than 87%. The artificial neural networks (ANNs) and genetic programming (GP)-based models obtained from the literature, have R2 values of about 85% and 83%, respectively which are higher than 80% for the GEP-based model. A subsequent comprehensive parametric study is further carried out to evaluate the sensitivity of the foundation settlement to the effective input parameters. The comparison results prove that the new EPR and GP-based models are the most accurate models. In this study, the feasibility of the EPR, GP and GEP approaches in finding solutions for highly nonlinear problems such as settlement of shallow foundations on granular soils is also clearly illustrated. The developed models are quite simple and straightforward and can be used reliably for routine design practice.
Jui-Chao Kuo, Teng-Yi Kuo, Cheng-Han Wu, Shih-Heng Tung, Ming-Hsiang Shih , Wen-Pei Sung, Weng-Sing Hwang,
Volume 12, Issue 2 (Transaction A: Civil Engineering, June 2014)
Abstract

In this study digital image correlation (DIC) technique combined with a high speed video system was used to predict movement of particles in a water model. Comparing with Particle-image velocimetry (PIV) technique, it provides a low cost alternative approach to visualize flow fields and was successfully employed to predict the movement of particles in a water model at different submergence depth using gas injection. As the submergence depth increases, the number of the exposed eye is reduced accordingly. At 26.4 cm submergence depth, an exposed eye was found at 1/3 of the submergence depth, whereas two exposed eyes were observed at 1/2 depth and near the bottom wall at 24 cm submergence depth.
D. F. Cao, W. J. Ge, B. Y. Wang, Y. M. Tu,
Volume 13, Issue 1 (Transaction A: Civil Engineering March 2015)
Abstract

In order to investigate the flexural behaviors of RC beams after freeze-thaw cycles, compressive strength test of concrete cubes after 0, 50, 100, 125 freeze-thaw cycles were made, and static flexural experiment of 48 RC beams after 0, 50, 100, 125 freeze-thaw cycles were made. The relationships of relative compressive strength, mass loss rate, relative dynamic elastic modulus and numbers of freeze-thaw cycles were analyzed. The influences of different numbers of freeze-thaw cycles on the flexural behaviors of RC beams with different concrete grades were studied. The results show that concrete cubes’ mass, relative dynamic elastic modulus and compressive strength decrease with the increasing of freeze-thaw cycles, and high-strength grade concrete could slow down the damage caused by freeze-thaw cycles. Experimental values of test beams stiffness under short-term load were smaller than theory value. Some under-reinforced RC beams occurs over-reinforced failure mode after freeze-thaw cycles. Boundary reinforcement ratio of RC beams after certain numbers of freeze-thaw cycles was derived and its correctness was verified by experiment. Current code for design of concrete structures about crack load and ultimate load are still suitable for RC beams after freeze-thaw cycles.
H. Tekeli, E. Atimtay, M. Turkmen,
Volume 13, Issue 3 (Transaction A: Civil Engineering, September 2015)
Abstract

In this paper, an approximate method is proposed for determining sway of multistory RC buildings subjected to various types of lateral loads. The calculation of both fundamental period and stability index in RC building requires the sway term at each story level. Using approximate method design engineers can estimate sway terms at each story level. The developed analytical expressions are inserted into fundamental period and stability index equations to replace the sway terms, which yields modified equations for fundamental period and stability index without any sway terms. It is fairly easier to employ these equations developed by eliminating all sway terms. Results obtained from the equations are remarkably close to those generated by the related computer program. Consequently, design engineers can reliably use the simple equations to calculate stability index and fundamental period, which enables the determination of these parameters without referring to the complex sway terms. The capability and accuracy of the proposed equations are demonstrated by a numerical example in which computer program results are compared with the proposed methodology.
L. Zeng, Q. Zhou, Ch. Xu, Y. Wu, X. Tu,
Volume 13, Issue 4 (Transaction A: Civil Engineering December 2015)
Abstract

To study seismic performance of concrete-encased composite columns with T-shaped steel cross-section, twelve half-scale columns were tested under quasi-stastic cyclic loading. The result indicates that concrete-encased composite columns with T-shaped steel section possess good seismic performance. The failure modes include bending failure, shear-bond failure, shear compression failure and shear-composition failure. Unsymmetrical phenomenon of positive and negative hysteresis loop was shown evidently. Span ratio has a great influence on failure mode. The ductility performance decreases with increasing of axial compression level. As stirrup ratio increases, ductility and bearing capacity of columns are improved greatly, and energy dissipation capacity after yielding is enhanced. Cross tie can enhance ultimate bearing capacity, and lower strength attenuation and stiffness degradation on the later loading stage


Alemdar Bayraktar, Ahmet Can AlTunişik, Temel Türker,
Volume 14, Issue 1 (Transaction A: Civil Engineering 2016)
Abstract

This paper addresses the ambient vibration based finite element model updating of long span reinforced concrete highway bridges. The procedure includes ambient vibration tests under operational conditions, finite element modeling using special software and finite element model updating using some uncertain parameters. Birecik Highway Bridge located on the 81stkm of Şanlıurfa-Gaziantep state highway over Fırat River in Turkey is selected as a case study. Because of the fact that the bridge is the sole in this part of Fırat, it has a major logistical importance. The structural carrier system of the bridge consists of two main parts: Arch and Beam Compartments. In this part of the paper, the beam compartment is investigated. Three dimensional finite element model of the beam compartment of the bridge is constituted using SAP2000 software to determine the dynamic characteristics analytically. Operational Modal Analysis method is used to extract dynamic characteristics of the beam compartment by using Enhanced Frequency Domain Decomposition method. Analytically and experimentally identified dynamic characteristic are compared with each other and finite element model of the beam compartment of the bridge is updated by changing of some uncertain parameters such as section properties, damages, boundary conditions and material properties to reduce the differences between the results. It is demonstrated that the ambient vibration measurements are enough to identify the most significant modes of long span highway bridges. Maximum differences between the natural frequencies are reduced averagely from %46.7 to %2.39 by model updating. Also, a good harmony is found between mode shapes after finite element model updating.


Jianwei Tu, Guang Que, Bo Tu, Jiayun Xu,
Volume 14, Issue 5 (Transaction A: Civil Engineering 2016)
Abstract

Ship lift is a major navigation structure lifting and lowering ships to shorten the time across the dam. The ship chamber, the key equipment, serves as the carrier for ships. Due to its gigantic body and mass, complicated coupled vibrations occur between the chamber and ship lift structure during seismic process. With the engineering background of the ship lift at the Three Gorges dam, a three-dimensional shell finite element model is established for the ship lift, and then simplified into a three-dimensional truss finite element model through dynamic equivalent principle. And the numerical model of coupled vibration analysis is formed through static condensation, calculating the coupled vibration response between the ship lift structure and the ship chamber. The result shows that no connection and rigid connection between them are both inadvisable. Consequently, three connection devices: spring, viscous liquid damper and magneto-rheological fluid damper are applied to control coupled vibrations during artificial seismic waves. The result shows that the magneto-rheological fluid damper makes better vibration damping effect if suitable semi-active control strategy is applied, in comparison with passive control devices.


ArTur Duchaczek, Zbigniew Mańko,
Volume 15, Issue 4 (Transaction A: Civil Engineering 2017)
Abstract

The paper is presented an attempt to assess service life of steel girders in military bridges (or by-pass temporary bridges) when fatigue cracks are detected in them. A function describing the geometry of fatigue cracks, the so-called crack shape factor Y, for two different, assumed calculated models, was presented. The function was used to plot sample graphs allowing assessing the remaining service life of such structural elements or engineering structures in a simple way. This method of analyzing can be used not only for the military bridges but also for other steel structures with existing cracks. The work is also presented assessments of possible applications of two FEM calculated models using shell elements to test stress and deformation at the top part of a fatigue crack located in a web of a steel girder used in the military bridges. The results of the conducted numerical analyses were compared with the results obtained in experimental research conducted in laboratory conditions using extensometers.



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