Journal of Bridge Engineering

This study reported fatigue test results of 300-mm-wide specimens with three details: 80% partial joint penetration (80%PJP), weld melt-through (WMT), and both. The specimens were cut out from full-scale orthotropic deck specimens of 16-mm-thick deck plate. In the fatigue test, the deck plate was subjected to cyclic bending loading and the rib was free from loading. The fatigue fracture surfaces showed that the presence of WMT may affect the initiation of fatigue cracks. A propensity to root cracking rather than toe cracking was observed. Plotting fatigue test results in an S-N diagram showed that the specimens with WMT seemed to have slightly lower fatigue strengths than the 80%PJP specimens, but the difference is more likely to be within a usual scatter of test data, which means that both details have comparable fatigue strength. The present test results satisfied the S-N curves of JSSC-E (80 MPa at $2\times {10}^6$ cycles) or AASHTO-C (89 MPa at $2\times {10}^6$ cycles).

Most studies on shear lag effect in box girders are only concerned about concentrated loads and uniformly distributed loads. In this paper, a finite-element method based on the variational principle is presented to analyze the effect of prestressing on shear lag in box girders. The procedures and main steps are listed to demonstrate how to use the proposed FEM, which is verified by the analytical method and the numerical examples. The shear lag effect in box girders with different types of support conditions under prestressing is analyzed in detail. The shear lag effect in box girders under prestressing is more apparent than that under uniformly distributed loads or vertical concentrated loads. The values and distributions of shear lag coefficients are relate to the anchorage locations of prestressing and the distributions of internal forces along the girder under the combined uniformly distributed load and prestressing. Among the conclusions of the study is that negative shear lag under the uniformly distributed load and prestressing may occur both at the midspan of a simply supported box girder and at the fixed end of a cantilever box girder.

Existing buffeting theories and methods for dealing with skew winds are summarized. A modified version of the mean wind decomposition method is described that directly uses wind monitoring data from structural health monitoring systems. A method for time-domain buffeting analysis is presented and implemented in ANSYS, in which self-excited forces are modeled as elemental aeroelastic stiffness and damping matrices by element Matrix27. The entire numerical procedure is implemented in MATLAB and ANSYS, and the buffeting responses can be conveniently computed with very concise input data. This method is applied to the buffeting analysis of the Runyang Suspension Bridge during Typhoon Matsa. The measured data of wind characteristics are used to predict the buffeting responses of the bridge with a finite-element model. The predicted buffeting responses are compared with those from field measurements. A reasonably good agreement between the calculation and the measurement validates the effectiveness of the method. Finally, the characteristics and mechanism of buffeting responses of long-span bridges are discussed to provide references for further studies.

The use of short-term load data to extrapolate or project remote future maximum load has been practiced in structural design code development and/or calibration. However, this approach has not been adequately evaluated or validated because of the absence of long-term data, which is important for the structures’ safety governed by these codes. In this paper, the application of such extrapolations to highway bridge design is studied by taking advantage of available long-term truck weight data obtained from the weigh-in-motion technique. A new extrapolation method is proposed from the understanding of the importance of the load probability distribution’s high tail. This approach significantly reduces the mathematical length of the extrapolation/projection and thus increases its reliability. Also presented in this paper are application examples. In addition, the extrapolation process proposed is evaluated with quantitative indexes. The application of a temporal extrapolation/projection can now be evaluated by using these indexes for its reliability and appropriateness.

A number of older bridges were constructed with floor systems consisting of a noncomposite concrete slab over steel girders. A potentially economical means of strengthening these floor systems is to connect the existing concrete slab and steel girders with postinstalled shear connectors to permit the development of composite action. This paper presents the results of an experimental investigation of this concept. Five large-scale noncomposite beams were constructed, and four of these were retrofitted with postinstalled shear connectors and tested under static load. The retrofitted composite beams were designed as partially composite with a 30% shear connection ratio. A noncomposite beam was also tested as a baseline specimen. Test results showed that the strength and stiffness of existing noncomposite bridge girders can be increased significantly. Further, excellent ductility of the strengthened partially composite girders was achieved by placing the postinstalled shear connectors near zero-moment regions to reduce slip demand on the connectors. The test results also showed that current simplified design approaches commonly used for partially composite beams in buildings provide good predictions of the strength and stiffness of partially composite bridge girders strengthened using postinstalled shear connectors.

This paper presents a detailed numerical algorithm for time-domain flutter analysis of elongated bridges, emphasizing in particular some problematic issues with regard to the application of the indicial functions involved wherein. Some typical characteristics of the indicial functions adopted early in airfoil aeronautics and those in bridge aerodynamics are first reviewed. The paper then presents the indicial-function-expressed aerodynamic forces and the recursive functions involved in the integral of the memorial terms in them. The theoretical description and numerical results indicate that the aeroelastic forces expressed with indicial functions are, if the model parameters are well identified, equivalent to those with flutter derivatives. However, this is merely an equivalence of frequency spectrum, and the transient characteristics of the indicial functions so identified, therefore, may not be physically true. This may result in excessively distorted aeroelastic forces and extraordinary time-consuming attenuation of the incorrect transient responses. To avoid such problems, a methodology of linear searching of the indicial-function parameters in predefined ranges is developed, on the basis of which the influence of some important factors, such as the time step size and numerical ranges of model parameters, are investigated. Numerical results show that large time step size may induce nonnegligible additional phase differences between the simulated aeroelastic forces and the structural motions and thus affect the total work accumulation and, consequently, the flutter threshold. Therefore, care should be taken in selecting an appropriate time integral step size.

A simplified approach for modeling soil and foundation system supported bridge bents is applied to three bridges that represent three pile types and three superstructures. This point-of-fixity approach is applied by modeling the bridge bent substructure as an elastic frame. The models are compared with more refined analyses in FB-MultiPier, with SAP as an independent verification tool, using pile sections with nonlinear soil, pile, and pile cap material properties. The results for simple pile bents show that an equivalent frame model provides similar moment, shear, and displacement values as those obtained from both the SAP and MultiPier nonlinear analyses. Analysis results also indicated that the equivalent frame model parameters are particularly sensitive to the comparable selection of both axial and lateral loads. If lateral loads used to develop the equivalent model are higher than experienced, the axial and lateral deflections and moments will also be higher. For design purposes, this is conservative.