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The submerged floating tunnel (SFT) is a newly developed traffic structure for crossing the long waterway. On the basis of the vehicle–tunnel coupled vibration, the vortex-induced effect o...

Submerged floating tunnel (SFT) is a novel type of cross-sea traffic structure, which is different from the traditional bridge and immersed tunnel. With the help of its own buoyancy to balance the operational loads, SFT shows great potential for crossing long, large, and deep waterways. Since floating in the underwater environment all year around, SFT has to face a series of vibration problems during the operation. In this paper, some vibration problems of SFT, such as wave-induced vibration, vortex-induced vibration, vibration caused by accidental loading, and vehicle-induced vibration, are summarized. In the meantime, combined with the features of SFT, the test model is designed and manufactured in the work. The geometric scale ratio of the whole model is about 1:100. Some aluminum tubes, connected by the flanges, are used for simulating the main body of SFT. Two plexiglass boxes provide the platform for the model test car to move in the aluminum tubes. The cable force, displacement, and acceleration at the points in the control sections of the tube are monitored during the model test. The whole experimental work provides a meaningful reference and solid foundation for further study on vibration problems of SFT.

The submerged floating tunnel (SFT) is a novel traffic structure for crossing long channels and deep waterways. The dynamic behavior and response of the SFT under seismic excitation is complicated. In order to understand current methods for analyzing seismic response of the SFT and possibility of applying these methods to engineering, this paper reviews the research development of the failure mode and the analysis methods for dynamic response of the SFT under seismic load. Referring to those of bridge engineering and ocean engineering, aseismic measures of SFT are summarized while pros and cons of several kinds of measures are compared. The results show that the interaction merely between fluid and structure under seismic load is basically considered by the present numerical simulation methods. It is necessary to investigate on the behavior of fluid–SFT–soil coupling. At the same time, in view of the lack of comprehensive analysis methods and calculation procedures of SFT subjected to the action of seismic force and wave force, it is put forward that the multi-scale theory model ought to be established and the corresponding experimental researches should be carried out to obtain more accurate analysis results and verify the validity of various aseismic measures.

Based on the vibration mechanism of the anchor cable of submerged floating tunnel (SFT) in water, the partial differential equation of the anchor cable’s vibration with wave and uniform flow is derived. According to the simply supported boundary condition and the difficulty of solving the partial differential equation, the numerical solution is given by Galerkin method and Runge–Kutta method. Taking the design of SFT in Qiandao Lake as the engineering background, the responses of anchor cable vibration are analyzed and studied. The method of measuring and calculating anchor cable force in water is proposed. The results show that when the vortex-induced shedding frequency is close to the natural frequency of the first order of the anchor cable under the action of uniform flow, the cable will produce the corresponding vibration. At this time, the vibration response of the cable displacement arrives to the maximum. Although the third and fifth modes only account for about 1% of the displacement response, their influence on the dynamic bending moment and shear force of the anchor cable can reach 10%. With the same parameters of anchor cable, the vibration frequency of anchor cable in water is lower than that in air, and the difference increases with the increase of anchor cable force. The quadratic function between cable force and frequency of anchor cable in Qiandao Lake SFT is fitted, which can directly guide the monitoring of cable forces of SFT.

Guo, D. and Xiang, Y., 2020. Optimization research on maintenance strategy model for coastal highway bridge based on durability and reliability. In: Liu, X. and Zhao, L. (eds.), Today's Modern Coastal Society: Technical and Sociological Aspects of Coastal Research. Journal of Coastal Research, Special Issue No. 111, pp. 187–191. Coconut Creek (Florida), ISSN 0749-0208.Affected by the environment and load, the durability and bearing capacity of highway bridges in coastal areas have declined to varying degrees, which seriously affects the remaining service life of the bridge. To make optimal use of the maintenance funds of highway bridges in the whole life cycle, this paper studies and optimizes the maintenance plan of the bridge in the long-term service. Considering the coupling effect of marine environment and load, the degradation model of durability index and reliability index is established. The deterioration of highway bridges in coastal areas is studied based on the degradation model with durability and reliability index. The optimization results show that the remaining service life of the engineering example is extended by 6.6 years and 13.8 years, respectively.

Submerged floating tunnels (SFTs) are a novel type of traffic structure for crossing long straits or deep lakes. To investigate the dynamic pressure acting on an SFT under compression (P) wave incidence, a theoretical analysis model considering the effect of marine sediment is proposed. Based on displacement potential functions, the reflection and refraction coefficients of P-waves in different media are derived. Numerical examples are employed to illustrate the effects of the thickness of the sediment layer, the incident P-wave angle, the tether stiffness and spacing, and the permeability of the sediment on the dynamic pressure loading on the SFT. The results show that the dynamic pressure is related to the saturation of the sediment and affected by its thickness. Partially saturated sediment will amplify the dynamic pressure loading on the SFT, and the resonance frequency increases slightly with fully saturated sediment. Besides, increasing the tether stiffness or decreasing the tether spacing will decrease the dynamic pressure. Locating the SFT at greater depth and reducing the permeability of the sediment are effective measures to reduce the dynamic pressure acting on the SFT.

To analyze the dynamic behavior of a submerged floating tunnel (SFT) subjected to moving vehicle loads in an ocean current environment, a theoretical analysis model is proposed. The SFT is simplified as a beam on an elastic foundation, the moving vehicle is modeled as a spring-mass lump, and the current effect is considered as a combination of lift force, inertial force, and hydraulic resistance directly acting on the SFT. The governing equations are solved by the modal superposition method. A finite element method is developed to evaluate the results. The impact effects of the vertical displacement and the bending moment are used to analyze the dynamic responses of the SFT. The effects of some key parameters, such as the current velocity, the buoyancy-weight ratio (BWR), and the inclined angle of the tethers are also investigated. The results show that the behaviors of the structure are amplified under the fluid-vehicle-tunnel interaction. Furthermore, the current and the vehicle velocity will directly affect the impact responses of the SFT by changing the forces on the structure. The BWR and the inclined angle of the tethers will change the vibration characteristics of the SFT and affect the inside state of the structure.

To investigate the dynamic behavior of the submerged floating tunnel (SFT) under moving vehicle load, a SFT experimental model is designed and analyzed. Through typical experiment cases, the effects of cable and vehicle with different parameters on the SFTs are discussed. Besides, the numerical simulation method is proposed in ABAQUS/EXPLICIT module for contrastive analysis. The *VUMAP and the *VDLOAD subroutines are used for implementing the tube fluid force and the moving vehicle load in the numerical model. The results show that the vertical vibration of the SFT is relatively independent to other directions, and the connection between the tubes will partially weaken the overall stiffness of the SFT. In addition, the deviation amplification effect exists in the SFT subjected to moving vehicle load. Increasing the cable inclination angle and the cable diameter can reduce the amplification effect. For the SFT with different cable spacing, the deviation amplification effect of dense cable arrangement is smaller than that of the sparse cable arrangement. But their sensitivities to vehicle velocity are not very different. In the practical project, the cables should provide sufficient strength to the SFT for safety.

With the increase of traffic volume and load, the carrying capacity of the early constructed reinforced concrete multi-ribbed arch bridges are obviously lower, it is necessary to take various measures to strengthen them and enhance bearing capacity of these bridges. This paper proposes a reinforcement method by adding cable tower at the two ends abutments of the arch bridges and the inclined cables to improve behavior of the multi-rib arch bridge. The main idea is that additional bridge towers are set on both sides of the single span ribbed arch bridge abutment to hang stayed cables. Taking a typical reinforced concrete multi-rib arch bridge-Baibu Bridge as engineering background, the design of strengthening project was given. The analysis and field load test of the bridge were finished. The comparison between spatial finite element analysis results and field bridge test values of strengthened bridge has good agreement. It shows the validity of the proposed strengthening method for the rib arch bridge and improves effectively the bearing capacity of arch bridges.

Anchor-cables are critical bearing components of the submerged floating tunnel (SFT). As the accidental cable-breakage incident will seriously threaten the public safety, this paper investigates the global dynamic response of a SFT subjected to an abrupt anchor-cable failure by focusing on the post-breakage behavior. Firstly, an approximate theoretical approach is proposed, in which the analysis model of SFT is simplified and the alternate load path method (AP method) is adopted to simulate the cable-breakage process. Then, the differential equations of the SFT tube are established based on the Hamilton principle, and solved through the fourth order Runge-Kutta method. A finite element analysis in ABAQUS is also performed as a verification of the theoretical results, in which the VUSDFLD subroutine and ABAQUS/Aqua is employed to simulate the stiffness loss of the cable and apply the fluid loads respectively. A good agreement exists between the simplified theoretical model and FE simulation. Finally, the effects of some key parameters are discussed, such as the gravity-buoyance ratio and the damping ratio of the SFT, the breakage time and position of the broken cable, etc. The results show that the structural vibration is intensive after the sudden cable breakage. Also, the remaining anchor-cables close to the cable-loss position are most affected by the cable rupture. The change of gravity-buoyance ratio and damping ratio have notable effects on structural deformation. The SFT is most unfavorable when the cable breakage happens at the mid-span or near the two ends of the tunnel. The vibration amplitude attenuates significantly with the increase of the failure time of anchor-cable.

The submerged floating tunnel (SFT) is a novel traffic structure for crossing long channels and deep waterways. The moving vehicles within the SFT have a remarkable influence on structural vibration response. To analyze the eccentric load effect of vehicles in the SFT, the structure is simplified as a spatial beam on elastic foundation, while the vehicle is simulated as a seven-DOF model with three dimensions. Using the Morison equation to express the effect of nonlinear fluid resistance, the vehicle-tunnel coupling vibration equations under the action of a motorcade running on one lane of the roadway are derived using the Hamilton Principle. Then, with the help of the mode superposition method and the fourth-order Runge–Kutta method, the solution for the equation is obtained. The accuracy of the proposed theoretical derivation and corresponding programming are verified by the finite element method. Based on the analysis, the SFT with a total span of 1000 m is selected as the research object to explore the spatial behavior of the SFT under vehicle-tunnel coupling vibration. The results show that the vertical displacement peak appears at the quarter-span of the tube, whereas the peaks of horizontal displacement and torsional angle appear at the mid-span under the eccentric load of a motorcade. The contribution of high order modes on the structural displacement should be considered. Moreover, the form of the motorcade affects the vertical displacement and torsional angle of the tube, and with the change of motorcade layout and vehicle speed, the resonance effect and vibration elimination effect will appear in the vehicle-tunnel coupling vibration system. Furthermore, the design parameters of the cable have a significant effect on the deformation resistance of the tube, therefore the selection and layout of the cable should take both the anchoring stiffness and material cost into account. For controlling the eccentric load effect, the inclined angle and installation angle of the cable are recommended to be 60° and 75°, respectively.

Abstract In order to analyze the global spatial dynamic response of a submerged floating tunnel (SFT) under the impact load, the tube is treated as a beam on elastic foundation (BOEF) with three degrees of freedom (horizontal displacement, vertical displacement, and torsion angle). The governing differential equations of the tube are derived based on the Hamilton principle considering the non-linear hydraulic resistance. The spatial displacement responses of the SFT are presented by the modal superposition method and Runge-Kutta method. The coupling motion of the horizontal displacement and torsion angle is also investigated. A finite element model of the SFT is established in ABAQUS to verify the results of the BOEF model, and the UAMP subroutine is used to simulate the effect of hydraulic resistance. Finally, the effects of the parameters, such as the anchorage stiffness, inclined angle of the cable, buoyancy-weight ratio, and hydraulic resistance on the impact response are studied. The results show the BOEF model is validated to be a suitable simplified method for the global impact response analysis. The coupling motion between the horizontal displacement and torsion angle has a significant influence on the torsion. The change of buoyancy-weight ratio has effect on displacement results and the natural frequency of the tube. It suggests the reasonable inclined angle of cable is between 45° and 60°. The hydraulic resistance considered in this paper had an effect of more than 20% on the maximum displacement, so it should not be ignored in analyses.

The conventional method (CM) for shear lag analysis of thin-walled box girders supposes that the neutral axis coincides with the centroidal axis of the whole cross section, and thus neglects the axial equilibrium condition. An analytical method considering axial equilibrium and shear deformation, which is referred to as PM, is proposed for overcoming the defect of the conventional method. The longitudinal displacement of the web is introduced to satisfy the axial equilibrium condition and locate the neutral axis automatically. The shear deformation is considered according to the Timoshenko beam theory. Three independent shear lag functions are adopted for describing different shear lag intensities of the top, bottom and cantilever slabs. The governing differential equations for the displacement variables are deduced by means of the virtual work theorem and solved with the relevant boundary conditions. The analytical solution is then derived for the distance from the neutral axis to the top fiber of the cross section. The accuracy of the proposed method is validated by comparisons with the available experimental data as well as the finite element analysis results. Moreover, the distances from the neutral axis to the top fiber, axial forces, and stress difference ratios are analyzed for typical thin-walled box girders to quantify the influence of the axial equilibrium condition. Finally, an extensive parametric study is conducted to examine the effects of various geometric parameters on the stress difference ratio under different load types. The results show that the proposed method can provide good predictions for both deflections and axial stresses, and neglecting axial equilibrium leads to considerable underestimations of axial stresses especially at the top flange-web junctions over the interior support of the continuous box girder.

Submerged floating tunnel (SFT) is a new type of cable-supported structure system for strait crossing. Once the local anchor-cable suddenly fails, it will inevitably cause evident vibration and internal force redistributions of the structure. In order to study the dynamic responses and mechanical behaviors of the SFT subjected to abrupt anchor-cable breakage, a model test is conducted by a set of sensors installed on SFT for cable force, tube displacement and strain measurements. The transient dynamic signals following cable failure are tested and analyzed. Dynamic amplification factor (DAF) and dynamic coefficient (DC) are respectively used to evaluate the impact effect from the cable failure. Meanwhile, finite element simulations are also performed within ABAQUS. The establishments of the finished state of SFT before cable breakage and the dynamic cable failure process are presented both in the model test and FE model. Comparisons between the FE predicted values and the experimental results show a good agreement. On this basis, some influence factors are discussed in different cases of the cable-loss positions and the cable forces of ruptured cable, etc. The results show that the finished state of SFT under dead load (tube redundant buoyancy) after cable-force optimizations is more reasonable than that directly applying dead load without any cable-force adjustments, with more uniform cable force distribution and smaller tube deformation. Although the SFT suffers strong oscillations after sudden cable-breakage incident, no progressive collapse occurs when the safety margin of the rest structure is sufficient. The dynamic effect on remaining cable members due to sudden cable failure can be evaluated by DC method. A DC value of 1.5 is recommended to ensure the safety of SFT anchor-cables. When cable failure happens at the mid span of the tunnel, the deformation of SFT tube is most critical.

Submerged floating tunnel (SFT) is a novel type traffic structure for crossing the long straits. To analyze the vehicle-tunnel coupled vibration of SFT due to tether parametric excitation, Hamilton principle and D'Alembert's principle are applied to establish the theoretical model. The fourth order Runge-Kutta method is carried out to calculate the responses of the system. The proposed model is verified by the beam on the elastic foundation (BOEF) model without considering tether parametric excitation, and the relative difference is less than 2%. If the initial excitation can be controlled in a small range, the influence of the tether vibration on the vehicle-coupled vibration can be efficiently reduced. Meantime, the effects of some factors, such as the gravity-buoyance ratio (GBR), the inclined angle of the tether (IAT), and the vehicle velocity on the dynamic response are discussed. The results show that the dynamic amplification factors (DAFs) of the deflection and the bending moment decrease with the GBR increasing. Besides, the larger IAT results in larger tether tension fluctuation when the vehicle-tunnel coupled vibration of the SFT subjected to tether parametric excitation. And the slower vehicle is more affected by the tether vibration when the vehicle drives in the tunnel.

This paper employs the random decrement technique as an output-only method to detect damage from the acceleration signals under a moving load. The random decrement technique is an especial averaging method that produces Random Decrement Signatures (RDS). For this purpose, Arias Intensity (AI) was employed to calculate the energy content of each RDS and substitute each acceleration signal by a scalar invariant value. Normalizing AIs, all RDSs were then updated so as to show a unique energy along the undamaged structure. Once the normalizing factor was computed for the intact structure, the damage was determined by the absolute difference of normalized AIs obtained from each individual RDS along the structure simultaneously. To verify the proposed method, two experimental models of a simply supported beam and a scaled arch bridge were developed under a moving load (vehicle simulation), and acceleration data were recorded. The results of laboratory models proved that the RDSs can accurately detect the damage location using the normalized AI without applying any further frequency filtering. This method needs neither the damage location nor modal parameters in advance, and could properly work in a noisy environment as well.

This paper provides a simple and direct output-only baseline-free method to detect damage from the noisy acceleration data by using Moving Average Filter (MAF). MAF is a convolution approach based on a simple filter kernel (rectangular shape) that works as an averaging method to smooth signal and remove incorporated noise. In this paper, a method is proposed to employ MAF to smooth acceleration signals obtained from a series of accelerometers and determine the damage location along a steel beam. To verify the proposed method, a simply supported beam was modelled through a 3D numerical simulation and an experimental model under a moving vehicle load. The response acceleration data was then recorded at a sampling frequency of 500 Hz. Finally, damage location was identified by applying the proposed method. The results showed that the proposed method can accurately estimate the damage location from the acceleration signal without applying any frequency filtering or baseline correction.

Large civil structures such as cable-stayed bridge should be periodically inspected to ensure structural integrity. Taking the main span of Chaibu Bridge as an engineering background, this paper summarizes the monitoring strategies and designs of the structure health monitoring system. The whole layout of sensors and the components of the structure health monitoring system are discussed. The study shows the structural health monitoring systems can offer valuable information in evaluating structural integrity, durability and reliability, and ensure optimal maintenance planning and safe bridge operation.

Submerged floating tunnel (SFT) is a kind of long distance flexible sea structure. The dynamic behavior of SFT is bound to be affected by the action of ocean current. According to the typical cross-section of the structure, the two-dimensional plane coupled vibration equations are derived based on Lagrange equations to analyze the cross-flow and torsion coupled dynamic response of SFT in ocean current environment. Meantime, the fourth-order Runge-Kutta method is used to solve the vibration equations. Finally, the effect of some key parameters, such as the height-width ratio, eccentric throw and the current velocity are investigated. The results show that the eccentric throw and the current velocity have obvious effects on the coupled structure vibration. With the increase of the eccentric throw and current velocity, the amplitude of the coupled vibration increases. Moreover, it can guarantee the relatively small vibration amplitude in cross-flow direction and torsion, when the height-width ratio is between 0.5 and 0.6.

The measurement accuracy of the cable tensions in the hanger rods of concrete filled steel tube arch bridges is important for the correct evaluation of bridges condition. Based on Jinpan Bridge-a half through concrete filled steel tube arch bridge with 80 m span in Tiantai, it was put forward the vibration frequency method for testing and evaluate suspender tensions with the help of analysis vibration characters of the suspender. The precision of cable force calculation formula was verified after comparing the practical tension with the designed tension obtained from tension jack method. Then, according to the test results and values predicted by the presented cable force calculation formula, the cable tensions were adjusted. Cable tension test results in the finished bridge show that this method is feasible.

Based on the results of experiment, this paper discusses about the updating and validation of accurate finite element model for damage identification of the steel-concrete composite box girder bridge. Taking a 5 meters long steel-concrete composite box girder bridge as the research object and the finite element model is established. By means of scale model test the updating of the accurate finite element model has been completed and validation is confirmed.

The prestressed concrete deck-tied arch bridge doesn’t only have a long span, good appearance and economy, but also have the characteristics of low requirements to the foundation. It changes traditional tied arch bridge into deck-tied arch bridge, which looks like sunflower-shaped arch and prestressed steel strands are embedded in box girder on the top of the arch. Taking Yingbin Bridge as engineering background, the reasonable analysis model was established and behaviour of the bridge under design load was analyzed. The results shown that the design project is reasonable, prestressing force embedded in box girder can balance horizontal thrust in arch bridge effectively, improving the internal force of the main arch ring.

Taking the four-span 40m simply supported multi-box steel-concrete composite girder bridge in the ProjectⅡ of Qiushi Expressway in Hangzhou as the background, this paper analyzed the static and dynamic behaviour of the bridge by FEM, then finished a field test study for the bridge. Finally, comparing the test values with the results obtained from FEM analysis, it was verified that the rigidity transverse beam method with infinte stiffness is also adaptive to caculating and predicting the load transverse distribution of the multi-box steel-concrete composite bridge. Steel diaphragm and stiffening rib of the multi-box steel- concrete composite bridge can improve the flexural capacity of bridge to some extent, so these contributions should be reasonably considered during the design stage in order to reduce the engineering cost. The measured modes agree well with the results from FEM.

Based on the data from dynamic analysis of a 40m-span multi-box steel-concrete composite bridge and the difference value of its modal curvature before and after the structural damage, this paper detects the damage locations in steel-concrete composite bridge by modal curvature difference method (MCDM). Here we adopt the updated finite element model in last work as analytical model, taking concrete density and elastic modulus as updating parameters and modal frequency+MAC as reference data. The results indicate that the modal curvature difference method can well locate the damages in steel-concrete composite bridge, especially the damage in concrete. But the change rate of frequency as damage index is insensitive to the bridge damage and the method can’t be applied solely for practical.

Calculating wind resistance is an important process in the design of highway bridges. The current codes of many countries include different rules and formulas regarding the calculation of wind resistance. In this paper, the transverse-direction wind loads on long-span girder bridges with tall piers were calculated using six codes from different countries under various terrain, pier height, and girder length conditions. The pier-bottom shear force and moment results of transverse wind loads calculated using these six codes were compared with those obtained using the buffeting frequency domain method. Results showed that, in Class B terrain, wind load results predicated on China’s 2004 general codes for the design of highway bridges and culverts, China’s 2004 wind-resistant design specifications for highway bridges, Japan’s 2007 wind-resistant design manual for highway bridges, and Part 2 of Britain’s 2006 steel, concrete, and composite bridge specifications for loads resembled each other closely. Some difference was found to exist among Classes A, C, and D terrain. The 2007 AASHTO LRFD bridge design specifications and China’s 2001 load codes for the design of building structures showed significant differences from the other four codes on all kinds of terrain. The applicability of the wind load rules in the AASHTO LRFD bridge design specifications to long-span girder bridges with tall piers merits further discussion. China’s wind load calculations of load code for the design of building structures mainly depended on the empirical parameters of architectural structures with large dimensions, and had limited applicability to bridge structures. For long-span girder bridges with tall piers, such as bridges with span length-to-width or -depth ratios exceeding 30, or pier height-to-transverse-width ratio exceeding 10.7, the wind load calculated using these codes was generally underestimated due to the neglect of the effects of aeroelastic forces, which must be taken into account in the design of these kinds of bridges.

Crack width calculation is an important part of concrete structure design. Due to many factors, the calculation formulas for crack width of concrete beam in various national standards are d...

Modern technologies are increasingly facilitating real-time monitoring of urban bridges and transportation networks. The advances in multi-channel fiber optical sensing system for instance, enable practical deployments for large extended bridge structural systems. Sensor data, can be used for long-term condition assessment, traffic-load regulation, emergency response, and seismic safety applications. In this paper, A flexible and scalable urban bridge Cluster Health Monitoring system is being developed and implemented. A typical concrete tied arch bridge was selected to introduce the computer-based automated signal analysis algorithms to process the monitoring data and one-year measurement data obtained from the fiber optical strain and temperature sensors are used for this study. The correlation analysis technique is applied to quantify the effect of temperature on the strain responses. The results show that the linear regression model exhibits good capabilities for mapping the strain responses with temperature.

Structural strain is one of the important parameters of representing structural health condition. Fiber-optic strain sensors have a number of inherent advantages, such as high sensitivity to external environment, small size, light weight, resistance to electromagnetic interference, ability for absolute measurement, superior stability, easy multiplexing and compatibility of being embedded in structures, etc.. In this paper, a novel strain monitoring method using optical fiber Bragg grating (FBG) sensor has been applied to the urban bridge cluster monitoring system, the principle, design and application in the structural health monitoring system are described, two years of normal operation has shown that this kind of strain monitoring and control method is feasible and useful.

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.

Aiming at the features of the articulated hollow slab beam bridges with transverse prestressed force, an assumption that regards the reinforced slab beam bridges as analogy orthotropic plate was proposed. The lateral flexural stiffness and torsional stiffness of the plate bridges per meter width can be calculated approximately as an average value of those of the solid section and the minimum hollow section. The longitudinal flexural stiffness and torsional stiffness per meter width remain the same as the original ones. The modified G-M method for calculating the strengthened bridge was proposed. Example as a typical hollow slab bridges, the lateral load distribution influence-line after strengthening bridge obtained by using modified G-M method. The numerical analysis before and after strengthening bridge by using FEM was complete to gain lateral load distribution influence-line. It shows that the values predicted by the proposed modified G-M were matched with the results by the FEM after strengthening bridge. It shows that the method strengthening articulated hollow slab beam bridges by exerting transverse prestress steel wire on them proved to be effective and the presented modified G-M theory to be right.

There is a strong need in maintenance and management of bridge that analyzes and predicts remaining service life (RSL) of reinforced concrete bridge. Since structural resistance of concrete bridge is generally suffered from environment, load and material etc. factors, which are intercoupled and time-varying. Hence researchers should consider the economic development of road traffic area, environment of operational bridge, variation of load, deterioration law of materials, and maintenance cost of LCC for predicting RSL of bridge. This paper reviews recent model of predicting the remaining service life (RSL) for concrete bridge and serviceability, analyzes model characteristic and defects, and looks forward to future research from the viewpoint of structure durability, reliability and life cycle cost, respectively.

Based on the method of separation of wind speed and direction variable, considering the wind direction frequency function, ascending order to calculate the probability of the actual distribution of the sample, extreme type Ⅰ (Gumbel) and three parameters of extreme type Ⅱ (Frechet) and extreme type Ⅲ (Weibull) probability distribution to fit the sample, this paper has analyzed the weather station observations of 34 consecutive years of the joint distribution of wind speed and direction near to a huge bridge, gained the basic design wind speed in different directions, comparatively analyzed the impact of the sampling interval of change on the basic wind speed as well. The results shows: wind speed in different directions at the same location or different sampling intervals samples of the wind speed sample may be subject to different types of extreme value distribution, should separately fitting; different wind direction frequency of extreme wind speed occurrence and the basic wind speed there are certain differences, taking into account the joint distribution of wind speed and direction is necessary to determine the design basic wind speed of the bridge, and will be conservative without considering the joint distribution; for the same sample wind speed matrix, the shorter the sampling intervals, the optimal distribution of the higher probability model fitting precision, the smaller the basic wind speed, the more economic and reasonable the results.