Advanced Materials Research Vols. 243-249

Abstract: The capacity of existing RC bridge could decay slowly when exposed to the aggressive environments. In this paper, the probability assessment method was presented. And the probability model of dead effect and vehicle action effect was established. The classification principle of bearing capacity was presented on the basis of reliability index; furthermore, the evaluation method was presented by a lot of calculation about the reliability index and the ratio of vehicle action effect to dead effect. An existing RC beam bridge with 34 years was evaluated; the technology condition is third class according to code for maintenance of highway bridges and culvers (JTG H11-2004). The checking index is 0.947 and the assessment result is also third grade. Comparing of the results indicated that the method is practical and convenient.

Abstract: The concept of frequency coefficient is built up based on theory，the formula between frequency coefficient and strain coefficient is established, and it was revised by the regression relational expression on the base of statistics results of 173 samples. The rational range of frequency coefficient was built by regression equation based on the confirmed range of strain coefficient, the frequency coefficient is regarded as a parameter to evaluate the bearing capacity of bridge structure, and its validity and rationality was proved by real project. The results shows that the structure is secure and with some safety margin when the frequency coefficient is greater than 1.111, the structure is dangerous when the frequency coefficient is less than 1.079, and the bearing capacity needs to be evaluated further when the coefficient is between1.111 and 1.079.

Abstract: In order to improve effect of hybrid ventilation, the paper discussed a solar chimney to enhance natural ventilation. Some factors influencing solar chimney hybrid ventilation in classroom, such as heat sources, air inlet arrangements, air velocity and solar radiation were studied by simulation and validated by experiments. The characteristics of temperature distribution and temperature efficiency in classroom were obtained and analyzed. A low position of air inlet in the room makes high temperature efficiency, the optimal value of the air inlet velocity is about 0.5 m/s. The research provides a better way to enhance hybrid ventilation by solar chimney.

Abstract: Several parameters, including typical loads, deflection, strains of steel bar and fiber- reinforced-polymer(FRP) bar under different sustained loading, were studied. The yield load and ultimate load of cantilever beams strengthened with near-surface-mounted(NSM) FRP bars are improved by 6.0%~15.2% and 55.7%~64.5% compared with non-strengthened beams, respectively. For strengthened beams,sustained loading can weaken the reinforced effect.The flexural behaviors of mounted beams were influenced by the lateral groove .

Abstract: As a common type of bridge, the reinforced concrete simply supported T-girder bridges have some usual disease problems such as web vertical cracks, incline cracks near the supports and diaphragm damage, and so on injured by transportation loads. In Shanxi province most of T-girder bridges appear to be under strength for current vehicle loads because most of which are designed by conventional methods and the old codes so it is important to evaluate how the existing damage influence the ultimate bearing capacity of the bridge. The destructive test is a directive mean of verifying the ultimate bearing capacity of bridges. This paper provides details of a destructive load test of a T-girder bridge called Zuojiabao Bridge. It describes the analysis performed prior to testing, aimed at predicting the response of the structure at both serviceability and ultimate states, and discusses the results obtained.The development rule of strain, deflection and crack and the ultimate bearing capacity of the bridge were obtained through the destructive test process. The results showthat although the old T-girder bridge has enough bearing capacity to satisfy the new vehicle standard, it is strongly recommended to strengthen or retrofit the bridge. And the finite element analysis can be effectively applied to the failure analysis of the reinforced concrete T-girder bridge subjected to destructive load.

Abstract: This paper to bridge safety evaluation as the starting point, the current evaluation method is based on the collection of the Delphi method, the level of analysis, grey cluster theory and the theory of fuzzy evaluation DHGF comprehensive evaluation method is applied to bridge safety evaluation, the establishment of a bridge safety evaluation of the DHGF evaluation model, and based on actual projects will DHGF evaluation method used in the actual concrete bridge safety evaluation, so as to verify the DHGF bridge safety evaluation of the scientific method, accuracy and operability. The main innovation is the first time DHGF evaluation theory is applied to bridge the field of evaluation and the establishment of the corresponding class bridge safety evaluation criteria and indicators in order to achieve the safety of the bridge accurate evaluation.

Abstract: Aiming at state assessment on substructure of the existing bridge with mid-small span, existing main assessing methods are outlined and their merits and shortcomings are commented. The uncertainty evaluation methods, such as uncertain analytical hierarchy process method and fuzzy comprehensive assessment theory, are illuminated to be the trend of new assessing theory systems. Finally, some exigent research orientations are suggested in this paper.

Abstract: The paper suggests a space rigid frame model which is equivalent to the space flexibility of pile-group foundation. Firstly, calculating the flexibility of pile-group foundation with “m” method, then the formulas to calculate geometrical parameters such as height of the rigid frame, length and width of the column section, as well as distance between the columns are deduced. So the equivalent rigid frame is acquired exclusively by these parameters. Finally ,discussing the accurate simulation of vertical flexibility and tensional flexibility. Which are achieved by additional springs.

Abstract: Deformation occurred in the bridge usage process due to the effort of self and external load. These deformations generally occurred in the absolute and relative position change of self and co-component including displacement, settlement, bending, distortion etc. The scope of this paper is to design a bridge geometry detection program system which using based on online PDA (Personal Digital Assistant). In the high speed data acquisition model, it can acquire the data of deflection, horizontal and vertical alignment, horizontal displacement in a real-time and digital way. In the data analysis module, it can evaluate the bridge safety and generate testing report through the comparison of the corresponding curves between the displacement and working positions.

Abstract: Based on scheme of Dalian gulf cross-sea bridge, in this paper, a 3-dimensional FE model for Self-anchored cable-stayed suspension bridge is established with finite element program and pile-soil-structure interaction is simulated by use of the equivalent embed fixation model. Based on the FE model, model analysis is carried out and the effects of pile-soil-structure interaction on dynamic behavior of long-span self-anchored cable-stayed suspension bridge are specially studied. Under vertical excitation, the seismic response analysis result considering that pile-soil-structure interaction was compared with that of without considering such interaction. The analysis result show that interaction reduced longitudinal displacement of stiffening beam in middle of main span and tower at bottom, moment at bottom of tower and auxiliary pier pile, but enlarged the moment of conjoining section between steel and steel beam. The research results provide some theoretical foundation to composite structure system.