Applied Mechanics and Materials Vols. 105-107

Abstract: For the effect of nonpre-stressed carbon fiber reinforced polymer (CFRP) Sheet Strengthening concrete beams to improve bending stiffness and crack resistance is not satisfactory, and it is difficult to totally unloading on the actual reinforcement, so in this paper, ANSYS is used to research the strengthened effectiveness and impact factors of pre-stressed CFRP reinforced concrete beams considering the secondary load.

Abstract: A fitting curve of stress-strain relation given is applied in numerical analyzing based on Legendre orthogonal polynomial and least square method. The nonlinear constitutive model is employed to examine the shape of an arch dam. For the asymmetries and high water pressure, the safety of High Arch Dam is one of key issues in the design and construction of High Arch Dam. The simulation results show that the basic mechanical performance index is symmetrical distribution. The dam mainly bears pressure and no obvious tensile stress exists in the dam when water level is normal. Material yields in dam heel when 1.4 times overloading is considered. It can be concluded that the dam is reliable and the safety margin is satisfactory.

Abstract: In this paper, the elasto-plastic dynamic analysis on the steel spatial arch truss with 120 m span and 0.4 rise-span ratio is carried out under earthquake EL-Centro wave with SAP2000 about pin-connected model and rigid truss model. The geometric and material nonlinear effects are considered simultaneously based on the plastic-hinge theory. The study shows that the vertical stiffness of the two models is smaller than horizontal stiffness; the failure mode of the pin-connected truss model under the earthquake action is elasto-plastic dynamic buckling, and the failure mode of the rigid truss model under the earthquake action is between the elasto-plastic dynamic buckling and the strength failure.In order to improve the ductility of the truss, we should enhance the design of joint stiffness in actual structures.

Abstract: Based on solving the problems of pre-camber of the prestressed concrete bridge in construction, the calculation principle of the bridge model constructed in each stage is studied, the relation between forward and backward analysis method is illustrated, and the influencing factors related to characteristics of pre-camber and each controlled point are analyzed. Considering the influencing factors such as the establishment of new elements, the stressing of reinforcement, the shrinkage and creep of concrete in construction, the calculation model is established in accordance with the characteristics of prestressed concrete bridge constructed in each stage. The deformation of each construction segment is calculated with the forward and backward analysis method respectively, so that the pre-camber of each cantilever construction segment is gotten,which is the basis of construction control.

Abstract: The constituents of concrete have a crucial effect on early age cracks of pumping concrete. Based on early age cracking mechanism of pumping concrete, the influence of raw materials, which includes cement, coarse and fine aggregates, mix ratio, admixtures, mineral additives and fibers on cracks are analyzed. The results show that the extent of early age cracking varies with constituents of concrete. It is advised that the appropriate concrete materials should be selected in terms of specific engineering features, not only by the requirements of strength and slump. With regards to the projects that are required crack control strictly, the characteristics of pump construction should be considered and the appropriate composition of concrete, especially the types and dosage of admixtures, mineral additives and fibers, should be determined by experiments.

Abstract: The optimization of the structure of bulk chemical hull (BCH) is derived by the finite element modeling (FEM) which is obtained by Patran and Nastran. In this paper, first of all, a new type of ship, BCH, is introduced. Then, the optimal scenario in theory is indicated by researching the transverse section of cargo holds of an ordinary BCH. And the FEM of the cargo holds of this ship is analysed, including the modeling, the load and the figures of stress and strain. The final conclusion would be obtained by comparing of the results which could verify the assumption forenamed. The simplification of the design is contributed by the new concepts and powerful capabilities of modeling of Patran and Nastran which improved the efficiency of ship designers.

Abstract: Shield tunneling is often adopted in underground engineering such as civil tunnel construction and mine excavation. The program FLAC3D is used to simulate the process of the tunnel excavation through underground structure in Shenyang in this paper. The analysis results show that,(1) the soil below the end wall suffers great displacement, when the shield approaches the end wall of underground framework from different directions, so the soil under the end wall needs to be reinforced. (2) Increasing pressure and volume of grouting can’t significantly reduce the amount of surface subsidence when the drilling of the shield acrosses through the independent foundation. (3) The influences of shielding to the construction are limited because of the constraint function to the surrounding rock above the tunnel by the great entire rigidity of under-ground framework. The results of numerical simulation exactly matches the monitoring data when the stiffness of under-ground frame structure is considered, and it can provide guidance for engineering practice.

Abstract: Single-layer hyperbolic paraboloidal latticed shell dome is adopted in the gymnasium of China University of Petroleum. And the center part of the dome employs crossed web bars in order to increase stiffness of the structure. The 1:12 scale model has been made according to the construction drawings, and the mechanical properties of the model are studied under self-weight load and design load. The regularity of the members' axial force and joints' displacements are obtained. And the results show that the deflection of dome under design load conforms to the requirement of specifications, which verified the correctness of the structure design. It is found that there is no overall instability and local instability, and the behavior of the structure is almost linear.

Abstract: In this paper, a new accelerated test method according to the influence of cement temperature and curing age is developed to detect the 28-day cement strength by using the standard test equipment based on weighted maturity theory. The results show the new method can accurately predict 28-day cement strength, which the mean of (predicted value) / (measured strength) is 0.98 and the COV. is 5.95%.

Abstract: In order to hurdle the limitations of Monte Carlo method and Response Surface method, the advanced Monte Carlo method was shown in this paper. And the system reliability of a one-bay and three-story steel framework structure was analyzed using the improved Monte Carlo method. Results of reliability analysis showed that there were high precision and a short calculating time using the improved Monte Carlo method. Then, the model of optimal design for steel frame based on the system reliability was built in accordance with the improved Monte Carlo method. And the optimal design on the steel frame was shown using the modern optimization method--genetic algorithm. From results, it was proved that optimal design without reliability could make structure have not enough reliability, even would not reach the required level of structural safety of Chinese criterions. It may lead to hidden dangers when only to reach objection on economy but haven’t considering reliability.