The present practice in Bangladesh for erection of girders is placing the girder directly on the bearing pad and joining the adjacent two spans in deck slab level by adopting expansion joints, as the bridges are prese...The present practice in Bangladesh for erection of girders is placing the girder directly on the bearing pad and joining the adjacent two spans in deck slab level by adopting expansion joints, as the bridges are presently designed as simply-supported beam bridge. The main disadvantage of this type of bridges is that, the seismic resistance is weak, and under the external force beyond the design range, the bridges are more likely to fall in danger because of failure in girders. Also they have expansion joints for each span, which affects the comfort of driving and the overall integrity of the bridge deck is poor [1]. Therefore, design and construction of the bridges have been revised to establish continuity between girders of two adjacent spans and transform the bridge as simply supported continuous beam bridge [2]. Temporary bearing (sandbox) method is proposed in this paper to solve the system transformation of continuous beam bridges. Design of the temporary bearing is very simple and can be manufactured at site. This method has been proved in construction of Arial Kha Bridge and can be applied for other similar bridges in Bangladesh.展开更多
Rutting is a chronic disease in asphalt pavements despite several mitigation measures. Although many attempts have been made by both researchers and practitioners to develop rutting prediction models, each model, howe...Rutting is a chronic disease in asphalt pavements despite several mitigation measures. Although many attempts have been made by both researchers and practitioners to develop rutting prediction models, each model, however, has certain inherent limitations due to assumptions and data used during the development of the model. Placement of an asphalt overlay is the most common method used in Zambia to rehabilitate existing asphalt pavements. The objective of this research is to go towards developing a national rutting prediction model for use in tropical hot climates based on default finite element creep and elasto-visco-plastic analysis tools in ABAQUS. Dynamic modulus and repeated load tests are conducted on overlay mixtures designed based on the pavement residual structural adequacy from deflection tests to provide material properties for the constitutive rutting model. Unified, three dimensional linear viscoelastic boundary value problems were formulated for each five national representative pavement sections. In general, the FE （finite element） creep and elasto-visco-plastie rutting evolutions were in agreement with the measured laboratory scaled one third mobile load simulators. Performance ranking of the validated models revealed optimal pavement system combination suitable for calibration. The study recommends future directions for local adoption of the South African mechanistic-empirical design method currently being developed.展开更多
This article studies the effects of limestone powder on rheological properties of cement - fly ash mortar with RHEOLAB QC type rotation viscometer. The Bingham fluid model is introduced to fit the yielding stress and ...This article studies the effects of limestone powder on rheological properties of cement - fly ash mortar with RHEOLAB QC type rotation viscometer. The Bingham fluid model is introduced to fit the yielding stress and plastic viscosity of the mortar. The POWER LAW fluid model is introduced to fit the rheological index of the mortar. The results show that, adding limestone powder and fly ash to the cement mortar significantly decreases the yield stress of the mortar, changes the plastic viscosity of the mortar, increases the rheological index, decreases the degree of shear thinning of the mortar, and thereby improves the mortar＇ s workability. In the case of cement - fly ash mortar, with the increase of limestone powder content, both the yield stress and plastic viscosity of the mortar increase. When the limestone powder content is not higher than 14%, the increase of yield stress is not significant. When the limestone powder content is lower than 8%, the increase of plastic viscosity is not significant. When the content of limestone powder is higher than 22%, the rheological index of the mortar decreases and the degree of shear thinning increases. The effects of limestone powder＇ s packing density, shape and size, specific surface area, and fluid volume, are found to be the four major factors responsible for the changes ofrheological properties of the mortar.展开更多
Traditional methods for water table prediction have such defects as extensive calculation and reliance on the presupposition of a homogeneous and regular aquifer.Based on the fundamentals of the general regression neu...Traditional methods for water table prediction have such defects as extensive calculation and reliance on the presupposition of a homogeneous and regular aquifer.Based on the fundamentals of the general regression neural network(GRNN),this article sets up a GRNN model for water level prediction.Case study indicates that this model,even with limited information,has satisfactory prediction accuracy,which,coupled with a simple model structure and relatively high calculation efficiency,mean a vast application prospect for the model.展开更多
In the present paper, cost control existing in stages of decision making, drawing design, construction bidding, construction, completion settlement, product sales of real estate development are analyzed and solutions ...In the present paper, cost control existing in stages of decision making, drawing design, construction bidding, construction, completion settlement, product sales of real estate development are analyzed and solutions for cost control in each stage are provided.展开更多
Le pré sent article donne une introduction complète à l'environnement d'investissement et aux avantages d'investissement du Ghana, et présente des propositions pour les activités d...Le pré sent article donne une introduction complète à l'environnement d'investissement et aux avantages d'investissement du Ghana, et présente des propositions pour les activités d'investissement au Ghana.展开更多
文摘The present practice in Bangladesh for erection of girders is placing the girder directly on the bearing pad and joining the adjacent two spans in deck slab level by adopting expansion joints, as the bridges are presently designed as simply-supported beam bridge. The main disadvantage of this type of bridges is that, the seismic resistance is weak, and under the external force beyond the design range, the bridges are more likely to fall in danger because of failure in girders. Also they have expansion joints for each span, which affects the comfort of driving and the overall integrity of the bridge deck is poor [1]. Therefore, design and construction of the bridges have been revised to establish continuity between girders of two adjacent spans and transform the bridge as simply supported continuous beam bridge [2]. Temporary bearing (sandbox) method is proposed in this paper to solve the system transformation of continuous beam bridges. Design of the temporary bearing is very simple and can be manufactured at site. This method has been proved in construction of Arial Kha Bridge and can be applied for other similar bridges in Bangladesh.
文摘Rutting is a chronic disease in asphalt pavements despite several mitigation measures. Although many attempts have been made by both researchers and practitioners to develop rutting prediction models, each model, however, has certain inherent limitations due to assumptions and data used during the development of the model. Placement of an asphalt overlay is the most common method used in Zambia to rehabilitate existing asphalt pavements. The objective of this research is to go towards developing a national rutting prediction model for use in tropical hot climates based on default finite element creep and elasto-visco-plastic analysis tools in ABAQUS. Dynamic modulus and repeated load tests are conducted on overlay mixtures designed based on the pavement residual structural adequacy from deflection tests to provide material properties for the constitutive rutting model. Unified, three dimensional linear viscoelastic boundary value problems were formulated for each five national representative pavement sections. In general, the FE （finite element） creep and elasto-visco-plastie rutting evolutions were in agreement with the measured laboratory scaled one third mobile load simulators. Performance ranking of the validated models revealed optimal pavement system combination suitable for calibration. The study recommends future directions for local adoption of the South African mechanistic-empirical design method currently being developed.
文摘This article studies the effects of limestone powder on rheological properties of cement - fly ash mortar with RHEOLAB QC type rotation viscometer. The Bingham fluid model is introduced to fit the yielding stress and plastic viscosity of the mortar. The POWER LAW fluid model is introduced to fit the rheological index of the mortar. The results show that, adding limestone powder and fly ash to the cement mortar significantly decreases the yield stress of the mortar, changes the plastic viscosity of the mortar, increases the rheological index, decreases the degree of shear thinning of the mortar, and thereby improves the mortar＇ s workability. In the case of cement - fly ash mortar, with the increase of limestone powder content, both the yield stress and plastic viscosity of the mortar increase. When the limestone powder content is not higher than 14%, the increase of yield stress is not significant. When the limestone powder content is lower than 8%, the increase of plastic viscosity is not significant. When the content of limestone powder is higher than 22%, the rheological index of the mortar decreases and the degree of shear thinning increases. The effects of limestone powder＇ s packing density, shape and size, specific surface area, and fluid volume, are found to be the four major factors responsible for the changes ofrheological properties of the mortar.
文摘Traditional methods for water table prediction have such defects as extensive calculation and reliance on the presupposition of a homogeneous and regular aquifer.Based on the fundamentals of the general regression neural network(GRNN),this article sets up a GRNN model for water level prediction.Case study indicates that this model,even with limited information,has satisfactory prediction accuracy,which,coupled with a simple model structure and relatively high calculation efficiency,mean a vast application prospect for the model.
文摘In the present paper, cost control existing in stages of decision making, drawing design, construction bidding, construction, completion settlement, product sales of real estate development are analyzed and solutions for cost control in each stage are provided.
文摘Le pré sent article donne une introduction complète à l'environnement d'investissement et aux avantages d'investissement du Ghana, et présente des propositions pour les activités d'investissement au Ghana.
