Applied Mechanics and Materials Vols. 178-181

Abstract: The experiment which based on the stress performance of unbonded and bonded prestressed concrete beam, has made a systematically research on the stress and strain variation law of pretressing tendon in the aforementioned reinforcement prestressed concrete structure. When the bonded prestressed concrete beam bearing load, there is a larger variation in stress and strain of prestressing reinforcement along the length. The maxima of stress and strain of prestressing reinforcement in bonded prestressed concrete beam appears in midspan, it is achieved the yield stress and yield strain, the minima appears in bearing, the stress and strain of prestressing reinforcement in bonded prestressed concrete beam is proportional to the distortion. The stress and strain of prestressed reinforcement in unbonded prestressed concrete beam is almost the same along the length.

Abstract: Error sensibility analysis of finite element model is widely used to obtain high-accuracy model, which is very important for structure simulation, damage identification and health diagnosis. ANSYS finite element software is used to build the initial model of three-span concrete-filled steel tubular arch bridge, and calculate the dynamic and static response value which is the basic compare parameters. Impact of different modeling factors to local dynamic and static response value of model is researched and the sensitivity of each response error to different modeling factors is summarized. In all the factors of modeling, the most important factor influencing the dynamic and static response of this bridge is the synergy between steel tubular and concrete. The result can be the reference when the concrete filled steel tubular arch bridge model is built.

Abstract: Prestressed concrete bridge, once completed, will inevitably generate a lot of cracks.These cracks seriously impact on the use of the bridge function. Cited a variety of cracks in prestressed concrete bridges, and from the cracks of prestressed concrete structures and components, described the causes of the prestressed concrete bridge cracks ,thus proposed a crack-effective preventive measures and treatment measures.

Abstract: Bridge construction is the national important foundation construction of bridge engineering, is the relationship between society and economy to coordinate development of lifeline engineering. Bridge construction of rapid development, huge capital investment, the economic society of the prominent role, making it to the bridge's safety, durability, more and more attention. Based on the analysis of detection results of existing bridges, bridge on the future work state of speculation, pointed out the possible development trend for the future to provide advice, bridge maintenance. As the bridge reinforcement and reconstruction to provide accurate and comprehensive data. The results of this study, can be formed quickly, economy of bridge health monitoring technology for bridge health security situation in the initial judgement; through the acquisition of the data of bridge health security archives; acquisition project archives data and webGIS docking platform form a" bridge based on webGIS project archives management system " for the future highway bridge maintenance and strengthening of decision making the corresponding reference. The project also has safety, economy, practical, convenient, and many other characteristics suitable for road and Bridge Health census and safety risk assessment.

Abstract: A variety of conventional weapons equipped with explosive are used to destroy the significant long-span arch bridge. Because of the special function of the weapons and the complexity of the arch bridge, the damage results with the features of uncertainty and fuzzy are assessed with fuzzy theory. Combined with the standards for technical condition evaluation of highway bridges and wartime specific requirements, the fuzzy mathematical model based on the fuzzy mathematics theory and method is established to judgment comprehensively the arch technical condition. The hirarchy fuzzy comprehensive evaluation method is applied to determine the technical state grade of the damaged arch bridge. The method of damage evaluation provides the effective reference for the emergency repairmen of the arch bridges.

Abstract: In EN1991-1-7 Eurocode 1: Part 1-7 Accidental Actions structural robustness is defined as ‘the ability of a structure to withstand events like fire, explosions, impact or consequences of human error without being damaged to an extent disproportionate to the original cause’. Accordingly, the principle of structural robustness is that local damage is acceptable, provided that it will not endanger the structure and that the overall load-carrying capacity is maintained during an appropriate length of time to allow the necessary emergency measures to be taken. For different structures the practical ways to achieve robustness are different. Lots of through arch bridges with hangers have been built throughout the world. However, the structural collapse may happen due to the hanger's damage or failure if the bridge is not designed appropriately. In this paper, the structural robustness of the through arch bridges with vertical hangers are discussed and verified by an example. Based on this study, a few practical suggestions are put forward to achieve the structural robustness for the future through arch bridges' design.

Abstract: Prestressed concrete (PC) box-girders with corrugated steel webs are one of the promising steel concrete composite structures applied to highway bridges. Although the basic structural characteristics including bending, shearing and torsion, etc., have been paid much attention, few researches on the seismic performance of this type of bridges are found, especially when the span of this type of bridges becomes larger and larger. In this paper, the seismic performance of one long-span PC box-girder bridge with corrugated steel webs is studied and compared with a conventional box-girder bridge with concrete webs, based on response spectrum analysis using ANSYS. The results show that, the vertical and transverse displacements of the box-girder with corrugated steel webs are slightly less than those of the box-girder with concrete webs, but the longitudinal displacement reverses, under the same earthquake excitation. The bending moments of representative sections of the box-girder bridge with corrugated steel webs are only about 70% ~ 90% of those of the corresponding conventional PC girder bridge. The results indicate that the box-girder bridge will have better seismic performance if the corrugated steel webs are adopted instead of the concrete webs, but it could also fulfill the tasks such as displacement control which resulted from stiffness reduction.

Abstract: A novel simplified vehicle model i.e. arbitrary moving mass-spring systems model, which can be simplified into moving loads model, is put forward and proved to be capable of analyzing the vertical dynamic responses of bernoulli-euler beam. Based on the matlab platform, a simply supported beam with a span of 40 m serviced in Beijing-Shanghai High-speed Railway is selected as the case study. The similarities and differences of vertical dynamic responses of the bridge based on this two vehicle models are compared. On this basis, the effects of vehicle speed and bridge damping ratio on the bridge’s dynamic magnification factor is studied. The computation results show that this new vehicle model is effective and reliable in its practical application.

Abstract: For the reliable assessment of bridge health and safety conditions, it is crucial to identify fundamental frequencies of suspender real time and automatically from random vibration signal that is weak and interfered with noise when suspender tension is measured online by frequency method. According to the characteristics of vibration signal spectrum, auto-power spectrum combined with autocorrelation function method which result was periodic distribution of spectral information in frequency domain. Plus from the spectrum the resonant peak of suspender was highlighted to reduce the noise disturbance which helped identify fundamental frequency and improved identification effect and result precision. In addition a field experiment in a tied arch bridge was carried out to analyze the collected vibration data. The practical application shows that this kind of measurement method is feasible and useful.

Abstract: Stone arch bridge was divided into three substructures. They were main arch, vertical wall and vice arch or carriageway board. Probabilistic neural network was applied to substructural damage identification. Static displacement and low-order frequencies were taken as input parameters of the network training. A numerical model was developed to simulate the process of substructural damage identification of stone arch bridge. The effects of noise data to training and recognition were researched. The results show that it is feasible and effective to use probabilistic neural network in substructural damage identification of stone arch bridge.