Theoretical approach with analytical and numerical procedure for determination initial displacement of a reinforced and prestressed concrete members, simple and cantilever beams, loaded by axial forces and bending mom...Theoretical approach with analytical and numerical procedure for determination initial displacement of a reinforced and prestressed concrete members, simple and cantilever beams, loaded by axial forces and bending moments is <span style="font-family:Verdana;">proposed. It is based on the principle of minimum potential energy with</span><span style="font-family:Verdana;"> equality of internal and external forces. The equations for strain internal energy have been derived, including compressed and tensile concrete and reinforce</span><span style="font-family:Verdana;">ment. The energy equations of the external forces with axial flexural dis</span><span style="font-family:Verdana;">placement effects have been derived from the assumed sinusoidal curve. The trapezoid rule is applied to integrate the segment strain energy. The proposed method uses a non</span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">-</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">linear stress-strain curve for the concrete and bilinear elastic-plastic relationship for reinforcement;equilibrium conditions at a sectional level to generate the strain energies along the beam. At the end of this article are shown three specific numerical examples with comparative, experimental (two tests)</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">results with the excellent agreement and one calculation result with a great disagreement, by obtaining results of virtual principle method.</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">With this method is avoiding the adoption of an unsure (EJ), as in the case of underestimating or overestimate initial flexural rigidity.</span></span></span>展开更多
Element stiffness equation is very important in structural analysis, and directly influences the accuracy of the results. At present, derivation method of element stiffness equation is relatively mature under ambient ...Element stiffness equation is very important in structural analysis, and directly influences the accuracy of the results. At present, derivation method of element stiffness equation is relatively mature under ambient temperature, and the elastic phrase of material stress-strain curve is generally adopted as physical equation in derivation. However, the material stress-strain relationship is very complicated at elevated temperature, and its form is not unique, which brings great difficulty to the derivation of element stiffness equation. Referring to the derivation method of element stiffness equation at ambient temperature, by using the continuous function of stress-strain-temperature at elevated temperature, and based on the principle of virtual work, the stiffness equation of space beam element and the formulas of stiffness matrix are derived in this paper, which provide basis for finite element analysis on structures at elevated temperature.展开更多
In a dynamic CT, the acquired projections are corrupted due to strong dynamic nature of the object, for example: lungs, heart etc. In this paper, we present fan-beam reconstruction algorithm without position-dependent...In a dynamic CT, the acquired projections are corrupted due to strong dynamic nature of the object, for example: lungs, heart etc. In this paper, we present fan-beam reconstruction algorithm without position-dependent backprojection weight which compensates for the time-dependent translational, uniform scaling and rotational deformations occurring in the object of interest during the data acquisition process. We shall also compare the computational cost of the proposed reconstruction algorithm with the existing one which has position-dependent weight. To accomplish the objective listed above, we first formulate admissibility conditions on deformations that is required to exactly reconstruct the object from acquired sequential deformed projections and then derive the reconstruction algorithm to compensate the above listed deformations satisfying the admissibility conditions. For this, 2-D time-dependent deformation model is incorporated in the fan-beam FBP reconstruction algorithm with no backprojection weight, assuming the motion parameters being known. Finally the proposed reconstruction algorithm is evaluated with the motion corrupted projection data simulated on the computer.展开更多
Moses算法是桥梁动态称重(BWIM)技术中最可靠的算法之一,是目前各商业BWIM系统的基础。然而,受影响线标定的约束,当前的商用BWIM系统仅适用于短跨径桥梁。针对这一情况,提出了虚拟简支梁法。该方法利用桥梁上的某一区段的隔离应变计算...Moses算法是桥梁动态称重(BWIM)技术中最可靠的算法之一,是目前各商业BWIM系统的基础。然而,受影响线标定的约束,当前的商用BWIM系统仅适用于短跨径桥梁。针对这一情况,提出了虚拟简支梁法。该方法利用桥梁上的某一区段的隔离应变计算车辆的轴重和总重,不受桥梁跨径的限制。建立了跨径为20 m和40 m的简支T梁桥有限元模型,基于车桥耦合振动理论模拟获得桥梁响应,并利用提出的新方法识别了车辆的轴重和总重。分析了路面平整度、车辆行驶速度等因素对识别精度的影响。结果表明:对于较短跨径的20 m T梁桥,常见三轴车的总重识别误差平均值在2%左右,五轴车的总重识别误差平均值低于1%,精度都稍优于传统Moses算法;而对于传统Moses算法不适用的40 m T梁桥,该方法识别车辆总重的误差平均值仍可控制在3%以内,表明该方法不受桥梁跨径的限制,具有更广的应用前景。展开更多
文摘Theoretical approach with analytical and numerical procedure for determination initial displacement of a reinforced and prestressed concrete members, simple and cantilever beams, loaded by axial forces and bending moments is <span style="font-family:Verdana;">proposed. It is based on the principle of minimum potential energy with</span><span style="font-family:Verdana;"> equality of internal and external forces. The equations for strain internal energy have been derived, including compressed and tensile concrete and reinforce</span><span style="font-family:Verdana;">ment. The energy equations of the external forces with axial flexural dis</span><span style="font-family:Verdana;">placement effects have been derived from the assumed sinusoidal curve. The trapezoid rule is applied to integrate the segment strain energy. The proposed method uses a non</span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">-</span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">linear stress-strain curve for the concrete and bilinear elastic-plastic relationship for reinforcement;equilibrium conditions at a sectional level to generate the strain energies along the beam. At the end of this article are shown three specific numerical examples with comparative, experimental (two tests)</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">results with the excellent agreement and one calculation result with a great disagreement, by obtaining results of virtual principle method.</span></span></span><span><span><span style="font-family:;" "=""> </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">With this method is avoiding the adoption of an unsure (EJ), as in the case of underestimating or overestimate initial flexural rigidity.</span></span></span>
基金the National Natural Science Foundation of China(No.50578093)
文摘Element stiffness equation is very important in structural analysis, and directly influences the accuracy of the results. At present, derivation method of element stiffness equation is relatively mature under ambient temperature, and the elastic phrase of material stress-strain curve is generally adopted as physical equation in derivation. However, the material stress-strain relationship is very complicated at elevated temperature, and its form is not unique, which brings great difficulty to the derivation of element stiffness equation. Referring to the derivation method of element stiffness equation at ambient temperature, by using the continuous function of stress-strain-temperature at elevated temperature, and based on the principle of virtual work, the stiffness equation of space beam element and the formulas of stiffness matrix are derived in this paper, which provide basis for finite element analysis on structures at elevated temperature.
文摘In a dynamic CT, the acquired projections are corrupted due to strong dynamic nature of the object, for example: lungs, heart etc. In this paper, we present fan-beam reconstruction algorithm without position-dependent backprojection weight which compensates for the time-dependent translational, uniform scaling and rotational deformations occurring in the object of interest during the data acquisition process. We shall also compare the computational cost of the proposed reconstruction algorithm with the existing one which has position-dependent weight. To accomplish the objective listed above, we first formulate admissibility conditions on deformations that is required to exactly reconstruct the object from acquired sequential deformed projections and then derive the reconstruction algorithm to compensate the above listed deformations satisfying the admissibility conditions. For this, 2-D time-dependent deformation model is incorporated in the fan-beam FBP reconstruction algorithm with no backprojection weight, assuming the motion parameters being known. Finally the proposed reconstruction algorithm is evaluated with the motion corrupted projection data simulated on the computer.
文摘Moses算法是桥梁动态称重(BWIM)技术中最可靠的算法之一,是目前各商业BWIM系统的基础。然而,受影响线标定的约束,当前的商用BWIM系统仅适用于短跨径桥梁。针对这一情况,提出了虚拟简支梁法。该方法利用桥梁上的某一区段的隔离应变计算车辆的轴重和总重,不受桥梁跨径的限制。建立了跨径为20 m和40 m的简支T梁桥有限元模型,基于车桥耦合振动理论模拟获得桥梁响应,并利用提出的新方法识别了车辆的轴重和总重。分析了路面平整度、车辆行驶速度等因素对识别精度的影响。结果表明:对于较短跨径的20 m T梁桥,常见三轴车的总重识别误差平均值在2%左右,五轴车的总重识别误差平均值低于1%,精度都稍优于传统Moses算法;而对于传统Moses算法不适用的40 m T梁桥,该方法识别车辆总重的误差平均值仍可控制在3%以内,表明该方法不受桥梁跨径的限制,具有更广的应用前景。
