Journal of Bridge Engineering

Tests on twelve bridges (six along Interstate 55 and six along Interstate $70∕270$ in Illinois) were performed to determine the validity of certain provisions for calculating bearing forces in the load and resistance factor design (LRFD) and the load factor design bridge specifications. The bridges were selected to be typical of Illinois interstate highway bridges and maintain a range of parameters to study. These bridges were instrumented on their beam webs with three strain gauge rosettes installed on each beam to measure shear stresses caused by loads. Static tests and slow moving 8 km/h $(5\mathrm{mi}/\mathrm{h})$ tests with a loaded truck in specified locations were performed. Dynamic tests at highway speeds were also completed. Finite-element models were developed and compared to the test results. The study shows that the LRFD specification procedures closely approximate the shear distribution factors determined by finite-element analysis and testing.

For a long-span coastal bridge structure, the corrosion initiation time is controlled by the speed of chloride ions transfer and the depassivation process within the structure. These processes are significantly influenced by the actual variation of the environmental conditions on the concrete surface throughout its service life. From the regional climate characteristics through local climate conditions, the microclimate variation on the concrete surface is studied in this research. A set of realistic environmental condition profiles is proposed, based on the exposure conditions and the material properties of the components. Moreover, a 2D integrated corrosion performance assessment model is constructed to capture the change in environmental conditions and simulate the coupled diffusion process and the corrosion performance in the time domain. Two typical locations (Hong Kong and Michigan) are chosen as numerical examples for implementing the proposed corrosion performance assessment model, and control of the environmental factors of the various chloride exposures is highlighted. These factors are used to construct an integral empirical equation together with the general critical material and geometrical parameters.

This paper presents the development of a comprehensive bridge management system that optimizes repair decisions considering multiple bridge elements and large networks of bridges. The strength of the system stems from its integration of project-level decisions of the best repair strategies to use on the elements of each bridge, and network-level decisions of the most beneficial repair year for each bridge. These decisions, however, represent complex optimization problems that traditional optimization techniques are often unable to solve. To handle such a large problem, the proposed system uniquely segments the problem into smaller sequential optimizations that are solved using the genetic algorithms technique. The system uses a year-by-year optimization formulation to maximize the benefit/cost ratio of the repairs, and to maximize the overall network condition. The paper provides a description of the multiple-element system, its life-cycle formulation, and its related models for deterioration analysis and repair cost estimation. System implementation and an example application are then presented to demonstrate the practicality of the system and its performance on different sizes of bridge networks.

Global monitoring of civil structures is a demanding challenge for engineers. Acoustic emission (AE) is one of the techniques that have the potential to inspect large volumes with transducers placed in strategic locations of the structure. In this paper, the AE technique is used to characterize the structural condition of a concrete bridge. The evaluation of AE activity leads to information about any specific part of the structure that requires attention. Consequently, more detailed examinations can be conducted once the target area is selected. In this case, wave propagation velocity was used as a means to evaluate, in more detail, the condition of the region indicated by the AE analysis.

The XY-friction pendulum (XY-FP) bearing is a modified Friction Pendulum (Earthquake Protection Systems, Inc., Vallejo, Calif.) bearing that consists of two perpendicular steel rails with opposing concave surfaces and a connector. The connector resists tensile forces, provides for independent sliding in the two principal directions of the isolators, and ideally, permits unhindered rotation about its vertical axis. Experimental studies on an XY-FP seismically isolated truss-bridge model were undertaken to study response under tridirectional excitations and to evaluate the use of XY-FP bearings for bridges. A truss bridge model was tested on a pair of earthquake simulators using acceleration orbits and near-field earthquake histories. The experimental results demonstrated the effectiveness of the XY-FP bearings as an uplift-prevention isolation system: the XY-FP bearings simultaneously resisted significant tensile loads and functioned as seismic isolators. The bidirectional horizontal response of the small-scale XY-FP isolation system was coupled due to the internal construction of the small-scale connectors that joined the two rails of each XY-FP bearing and the limited free-to-rotate capacity of the XY-FP bearings due to misalignment of the isolators during installation.

Rooted in structural dynamics theory, two approximate procedures for estimating peak responses of linearly elastic “ordinary” bridges crossing fault-rupture zones are presented: response spectrum analysis (RSA) procedure and a linear static analysis procedure. These procedures estimate the peak response by superposing peak values of quasi-static and dynamic responses. The peak quasi-static response in both procedures is computed by static analysis of the bridge with peak values of all support displacements applied simultaneously. In RSA, the peak dynamic response is estimated by dynamic analysis including all significant modes, which is simplified in the latter procedure to static analysis of the bridge for appropriately selected forces; usually only one mode—the most dominant mode—is sufficient in the RSA procedure. Appearing in these procedures is the “effective” influence vector that differs from the influence vector for spatially uniform excitation, and the response spectrum used in the RSA procedure differs from the standard California Department of Transportation (CALTRANS) spectrum. Both of these simplified procedures provide estimates of peak response that are close enough to results of the “exact” response history analysis to be useful for practical application.

Rooted in structural dynamics theory, three approximate procedures for estimating seismic demands for bridges crossing fault-rupture zones and deforming into their inelastic range are presented: modal pushover analysis (MPA), linear dynamic analysis, and linear static analysis. These procedures estimate the total seismic demand by superposing peak values of quasi-static and dynamic parts. The peak quasi-static demand in all three procedures is computed by nonlinear static analysis of the bridge subjected to peak values of all support displacements applied simultaneously. In the MPA and the linear dynamic analysis procedures, the peak dynamic demand is estimated by nonlinear static (or pushover) analysis and linear static analysis, respectively, for forces corresponding to the most-dominant mode. In the linear static analysis procedure, the peak dynamic demand is estimated by linear static analysis of the bridge due to lateral forces appropriate for bridges crossing fault-rupture zones. The three approximate procedures are shown to provide estimates of seismic demands that are accurate enough to be useful for practical applications. The linear static analysis procedure, which is much simpler than the other two approximate procedures, is recommended for practical analysis of “ordinary” bridges because it eliminates the need for mode shapes and vibration periods of the bridge.