Bridging Stress Research Articles

Measurement and prediction of local stress in a steel girder bridge

Measurement and prediction of local stress in a steel girder bridge

Procedure Inversion Effect Analysis of Final System Transformation of Prestressed Concrete Continuous Girder Bridge

When the cantilever construction is adopted by the prestressed concrete continuous girder bridge, the order of two key procedures between removing temporary support and tensing remanent prestressed cable is used to be ignored. In order to study the influence of procedure inversion, the influences on bridge shape, stress distribution and prestressing loss were calculated for one common prestressed continuous concrete box girder bridge by MIDAS CIVIL 2006, respectively. The obtained result presents that: the influence on the bridge shape and the prestressing loss are not apparent, but the influence on the stress distribution is serious; the maximal compressive stress of procedure inversion is more 42.3% than common construction procedure only by tensing the remaining steel beams at box girder; especially, the combining area between the box girder and temporary support is easy to pull out. So, the procedure inversion construction method cant be accepted.

Fatigue Threshold R‐curves Predict Fatigue Endurance Strength for Self‐Reinforced Silicon Nitride

There is a need for methods that can help predict and avoid fatigue failures of silicon nitride ceramic components. The fatigue threshold R‐curve has been proposed as potential solution to this problem. In this study, the fatigue threshold R‐curve for small, semielliptical surface cracks was calculated for a silicon nitride ceramic using the published bridging stress distribution developed from fatigue threshold tests on macroscopic crack specimens. To test the accuracy of the endurance strengths predicted using the fatigue threshold R‐curve, fatigue tests were conducted using four‐point bend beams of silicon nitride containing semielliptical surface cracks introduced by Knoop indentation. The effectiveness of the methodology was verified; indeed, 77% of the beams tested at stress levels above the predicted endurance strength failed within 107 cycles and 0% of the beams tested below the predicted endurance strength failed within 107 cycles. Furthermore, using the bridging stress distribution, which is thought to be a material property, the need for prohibitively difficult fatigue threshold experiments on small surface cracks is avoided. Accordingly, this methodology is potentially quite practical for use in the engineering design of ceramic mechanical components.

Fatigue crack growth in fiber-metal laminates

Fiber-metal laminates (FMLs) consist of three layers of aluminum alloy 2024-T3 and two layers of glass/epoxy prepreg, and it (it means FMLs) is laminated by Al alloy and fiber alternatively. Fatigue crack growth rates in notched fiber-metal laminates under constant amplitude fatigue loading were studied experimentally and numerically and were compared with them in monolithic 2024-T3 Al alloy plates. It is shown that the fatigue life of FMLs is about 17 times longer than monolithic 2024-T3 Al alloy plate; and crack growth rates in FMLs panels remain constant mostly even when the crack is long, unlike in the monolithic 2024-T3 Al alloy plates. The formula to calculate bridge stress profiles of FMLs was derived based on the fracture theory. A program by Matlab was developed to calculate the distribution of bridge stress in FMLs, and then fatigue growth lives were obtained. Finite element models of FMLs were built and meshed finely to analyze the stress distributions. Both results were compared with the experimental results. They agree well with each other.

Analysis of Bursting Crack of Bottom Slab and Reinforcement for a Large Continuous Girder Bridge

A large railway bridge is using (46.4 + 64 + 46.4) m double-line prestressed concrete continuous girder. In the construction process, bottom slab concrete in the mid span appears serious bursting crack phenomenon. Through the whole bridge stress analysis and closure segments locally fine finite element stress analysis, it appears tensile stress and large compressive stress in operational stage. Finally the bottom slab reinforcing schemes are proposed. It makes the following conclusions by analysis: (1) through the overall and local analysis stresses meeting the design requirements after reinforcement; (2) according to the domestic and foreign research experience, bursting crack reason of bottom slab is that prestressed pipes deviation from the design positions and anti-collapse steel bars are not set in place.

Effect of initial crack length on the measured bridging law of unidirectional E-glass/epoxy double cantilever beam specimens

In this paper, the effect of initial delamination length is experimentally investigated on obtaining the mode I bridging law of unidirectional E-glass/epoxy double cantilever beam (DCB) specimens manufactured by hand layup method. To this end, an experimental test set-up is established for accurate measurement of crack tip opening displacement (CTOD) using digital image processing method. DCB tests are performed for three different delamination lengths and the corresponding bridging laws are calculated using J-integral approach. Results showed that the maximum bridging stress, the shape of bridging law and energy dissipation in bridging zone are slightly affected by changing initial crack length. In other words, the measured bridging law acts independent of initial delamination length. Therefore, the obtained bridging law can be used with the cohesive elements available in the commercial finite element software to simulate the delamination propagation behavior in unidirectional DCB specimens.

Brittle matrix composites with heterogeneous reinforcement: Multi-scale model of a crack bridge with rigid matrix

Abstract A mechanical multi-scale model describing the relationship between the crack-opening and composite bridging stress in brittle matrix composites with heterogeneous reinforcement is introduced. Unlike currently utilized models, it is able to reflect the heterogeneity of fibrous reinforcement. Mechanical, geometrical and bond properties of individual fibers (e.g. fiber surface roughness, radius, strength) are defined as random variables. The functional dependency between these random variables and the fiber stress within the composite cross-section is introduced using local equilibrium equations. The response of the composite to an applied uniaxial tensile load is evaluated by averaging the fiber stress contributions in a crack bridge. In particular, the model describes the behavior of a single crack bridge in a composite assuming the matrix to be rigid. The fiber bridging action is represented using the shear-lag model. Upon fiber rupture the global load sharing for stress redistribution is considered. With these assumptions the rules for asymptotic Daniels’ fiber-bundle models can be applied for the evaluation of macroscopic crack bridge behavior. We use the model to illuminate the effect of selected sources of heterogeneity (fiber breaking strain, fiber radius and bond strength) on the crack bridge response and to approximately predict the ultimate state of a multiply cracked composite. The model constitutes a basis for the multi-scale simulation of the strain-hardening response of brittle-matrix composites.

Quantification of fibre bridging in Mode I cracked Glare without delaminations

Abstract Glare, a fibre metal laminate (FML), consists of several thin 2014-T6 aerospace aluminium alloy layers alternately bonded with E-glass fibre based composite prepregs in the present work. As cracked Glare is subjected to load, load or fibre bridging over cracks in soft aluminium layers causes diversion of load away from the cracks towards stronger intact fibres in the prepregs resulting in stress reduction or shielding effect at the crack tips. Fibre bridging diminishes if delaminations, caused by the development of interfacial cracks at the interfaces of aluminium and fibre layers, exist in the laminate. The paper investigates the cracked but non-delaminated Glare containing normal Mode I cracks in all its aluminium layers. Different crack lengths are considered in the laminates to examine the influence of crack size over bridging. A theoretical model is presented to determine fibre bridging stress for estimation of fibre bridging stress intensity parameter that quantifies the effect of bridging in the laminate. Crack tip stress intensity parameter is also found. The model is successfully validated by undertaking finite element analysis of series of un-identically cracked Glare laminates without delaminations under critical or fracture loads that are obtained experimentally by subjecting the laminates to load-extension test. Plain aerospace aluminium alloy specimens are also tested for fracture. Fracture toughness values of the laminates are seen to be significantly higher than that of plain aluminium specimens. The phenomenon of fibre bridging in the laminates is well substantiated and quantified by all the adopted procedures.

Numerical Simulation for Progressive Collapse of Continuous Girder Bridge Subjected to Ship Collision Based on Three-Stage Simulation Method

Three-stage simulation method [ was adopted to simulate the collapse process of a continuous girder bridge after being impacted by ship with considering pile-soil dynamic interaction and bridges initial stress before collision. The deformation, distribution of stress and responses of bridge were emphatically analyzed in this paper, which revealed the dynamic response and collapse mechanism of continuous girder bridge under impact load.

Research on Vibration Responses of Railway Steel Bridge Considering Welding Residual Stress

Vibration responses of railway steel bridge considering welding residual stress have been researched. Based on the reasonable heat source model matching the electrical arc welding, the welding residual stress in welding joints of steel bridge has been simulated. Meanwhile, it has been superimposing with the gravity stress and the actual measured dynamical stress of railway steel bridge. Then, acting all actions to the accurate finite element model, the vibration responses of railway steel bridge considering welding residual stress can be analyzed, and the conclusion that the residual stress has a significant contribution to the vibration dynamical stress in welding joints district of railway steel bridge has been obtained.

Behavior Response Analysis of Long Span Rigid-Frame Bridge Considering Construction Error

From the aspect of accumulated construction error of the bridge, the inaccuracy analysis method was put forward. Considering the two kinds of construction error case in construction stage, the inaccuracy response numerical model was built. The error effect to the bridge was researched quantitatively and qualitatively. The results demonstrate that more attention should be paid to the effects of two kinds of construction error on the stress and deformation of bridge. The study of sensitivity analysis of structural damage cases should also be engaged in the design and construction stage for the optimal reliability.

Urban Bridges Temperature Measurement System Based on Fiber Bragg Grating Sensing Technology

In recent years, with the rapid urbanization process and increased accidents of bridge damage and collapse, the research of bridge health monitoring and early-warning technology for the public safety has been promoted. Temperature load is one of the main loads to incur the deformation and the variation of stress of bridges. So temperature measurement is an important component of health monitoring for urban bridges. In this paper, a smart temperature measurement system is described which takes advantage of FBG sensor performance characteristics to improve the bridge temperature measurement. At present, the system has been integrated and applied in the project of main roads bridge Online Safety Monitoring Management System in Hangzhou (Phase II), a web-based urban bridge cluster monitoring system have been established since 2007. According to a tied arch bridge case studies, the one-year measurement data shows that the system not only can accurately collect the bridge temperature information and variety, but also successfully improve the performance benefits such as reduced measurement uncertainty, increased robustness, and failure prediction and detection.

Dynamic Stress Analysis of Coupled Vehicle-Suspension Bridge System in Cross Wind

Dynamic stress computation of long suspension bridges under both railway and wind loading is required for either strength or fatigue assessment. However, the effect of dynamic coupling among bridge, railway vehicle and wind on bridge stress response is not well understood. This paper presents a method for predicting bridge dynamic stress responses with coupling effects included. The bridge model (bridge subsystem) and vehicle model (vehicle subsystem) are established using the finite element method, and they are related to each other through wheel-rail contact conditions. The spatial distribution of both buffeting forces and self-excited forces over the bridge deck surface is considered to facilitate the computation of local stress responses. The Tsing Ma suspension bridge in Hong Kong and the data recorded by a Wind and Structural Health Monitoring System (WASHMS) installed in the bridge are utilized as a case study to verify the proposed method to some extent. The railway loading and wind speed measured by the WASHMS are taken as input for the computation simulation. The computed local stress responses are compared with the measured ones. The results from the case study demonstrate that the proposed method could effectively predict the local stress responses of the coupled traffic vehicles and suspension bridge system in cross winds.

Spatial mechanical behaviors of long-span V-shape rigid frame composite arch bridges

The Xiaolan channel super large bridge is unique in style and with greatest span in the world with a total length of 7686.57 m. The main bridge with spans arranged as 100m+220m+100m is a combined structure composed of prestressed concrete V-shape rigid frame and concrete-filled steel tubular flexible arch. First of all, the author compiles APDL command flow program by using the unit birth-death technique and establishes simulation calculation model in the whole construction process. The creep characteristics of concrete are also taken into account. The force ratio of the suspender, arch and beam is discussed. The authors conduct studies on the three-plate webs\'s rule of shear stress distribution, the box girder\'s longitudinal bending normal stress on every construction stage, meanwhile the distribution law of longitudinal bending normal stress and transverse bending normal stress of completed bridge\'s box girder. Results show that, as a new combined bridge, it is featured by: Girder and arch resist forces together; Moment effects of the structure are mainly presented as compressed arch and tensioned girder; The bridge type brings the girder and arch on resisting forces into full play; Great in vertical stiffness and slender in appearance.

Prediction of size effect and non-linear crack growth in plain concrete under fatigue loading

A new method is proposed that uses inverse analysis to calculate cyclic induced bridging stresses along a dominant crack face in a plain concrete three-point bending single edge notch specimen. Peak to peak low cycle fatigue data is used to back-calculate the bridging stresses and an equivalent crack resistance curve is derived with a weight function. Fourteen specimens were tested under low cycle fatigue and two were tested under high cycle fatigue. The results of this study indicate that the equivalent cyclic crack resistance curve obtained under low cycle fatigue can be used to predict the equivalent cyclic crack resistance under high cycle fatigue and explain the decelerating crack growth phenomenon and size effect in plain Portland cement concrete.

Stress and Deflection Parametric Study of High-Speed Railway CRTS-II Ballastless Track Slab on Elevated Bridge Foundations

Ballastless track slab system (BTS) of China Rail Transit Summit type-II (CRTS-II) is primarily used in China’s Beijing-Shanghai high-speed railway. As a new structural form, CRTS-II has not been extensively tested, and the design and manufacturing processes of CRTS-II BTS systems is not optimized and mature for its load-carrying capacity, structural integrity, deflection, and durability. This study carried out a numerical analysis of stress and deflection responses of the CRTS-II BTS system using SAP 2000. Design parameters include stiffness of the rail fastening, thickness and stiffness of the track slab, the cement emulsified asphalt (CA) mortar cushion, and the concrete supporting layer. Deflection, maximum bending stress, and maximum shear stress of different structural components of the CRTS-II BTS system are investigated under varying design parameters, with the aim to explore an improved set of design parameters. The rail defection is only significantly impacted by the rail fastening stiffness. To reduce the high-speed rail deflection so as to mitigate riding discomfort, higher stiffness of the rail fastening is suggested. To reduce the track slab bending stresses to prevent the high-speed rail from structural failure, the following parameter design strategy can be used: higher track slab thickness, lower track slab stiffness, lower rail fastening stiffness, higher CA mortar, and concrete supporting layer stiffness. All design parameters of the BTS system have negligible influence on the maximum bending stress and shear stress of the elevated bridges. The maximum shear stress of the BTS system is relative low compared with the maximum bending stress of the BTS system, suggesting that the BTS system behaves more like a beam rather than a plate.

A generalized solution to the crack bridging problem of fiber metal laminates

The slow crack growth and high residual strength of fiber metal laminates (FMLs) results from bridging, the transfer of loads from cracked metal layers to intact fiber layers that “bridge” the cracks over delaminations between the laminae. Understanding and improving the structural performance of FMLs therefore depends on characterizing the bridging phenomenon. Previously, mathematical models of bridging load transfer have been developed and verified for simplified circumstances:thin laminates with identical thicknesses and material composition through the laminate, identical crack lengths and delamination sizes, and simple tension loads. These models use a compatibility requirement at the delamination boundary to derive the bridging stress. This paper presents a generalized approach to solving the bridging problem that solves simultaneously for compatibility at every delamination boundary in the laminate, allowing the bridging load distribution to be derived for a laminate of arbitrary layup (different thicknesses and materials) with arbitrary damage (independent crack lengths and delamination sizes and shapes) and subject to arbitrary loading (any combination of applied tension and bending moment). The approach is evaluated by comparing its results to bridging stress distributions derived from finite element analysis. Good agreement was obtained for varied laminate and damage configurations, but some discrepancy exists in the presence of bending.

Space Analysis of Long-Span Continuous Rigid Frame Bridges

With the background of continuous rigid frame bridge,this paper considers the impact of the structural weight and the pre-stressed force in the construction phase,uses the ANSYS finite element analysis program to analyze the stress and strain of an continuous rigid frame bridge in the the largest cantilever state, focuses on different effects of the different radius of curvature and pier height.Through the analysis constructs the control mentality and the corresponding design proposal for the continuous rigid frame bridge had been provided.

Transverse load distribution of skew cast-in-place concrete multicell box - girder bridges subjected to traffic condition

Concrete multicell box-girder bridges are a common choice among the designers for various ranges of bridges. In order to provide safer and greater speed of traffic, the roadway is built as straight as possible. The use of skewed bridges has increased considerably in the recent years for roadway. The skewed bridges have quite different mechanical behavior from the straight bridges, although for skew angles less than 20 degrees, it is reasonably safe to ignore the effect of skew angles and analyze that at the straight bridge. In this study, in developing an analytical solution, an extensive parametric study was carried out to determine the maximum positive and negative stress distribution factors and to calculate the maximum distribution factor of deflection along the mid-span of skewed multicell box-girder bridges. A total of 240 representative bridges numerical models were selected and analyzed using SAP2000 finite element software. It was found that the span length, number of boxes, number of lanes and skew angles significantly affected the distribution factors of stress and deflection. Finally, several equations were proposed for stress and deflection distribution factors of multicell box-girder bridges for the application of American Association of State Highway and Transportation officials load and resistance factor design live loads.

An analytical study on the complete strain hardening process of ultra high toughness cementitious composites under direct tension load

The ideal tensile stress–strain curve of ultra high toughness cementitious composites (UHTCC) shows trilinear stress–strain relationship. And its strain hardening process can be divided into multiple cracking zone and post multiple cracking zone. In this paper, the general expression of the fiber bridging stress laws in the crack plane is presented, and the stress–strain models are established for both zones based on the law. Furthermore, the critical fiber length between fiber pull-out and fiber rupture in the post multiple cracking zone are deduced. And the precondition to guarantee the post multiple cracking zone is deduced.