Journal of Bridge Engineering

Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing speculation, on a civil engineering topic of general interest and relevance to the readership of the journal. The views expressed in this Forum article do not necessarily reflect the views of ASCE or the Editorial Board of the journal.

A 9.4-m-long, full-scale glued laminated bamboo (glubam) bridge model was constructed to duplicate a prototype truckload bridge. The soffit of the 600-mm-deep and 120-mm-wide glubam girders was further enhanced with carbon fiber–reinforced polymer (CFRP) sheets. The midspan deflections of the bamboo girders were obtained over the course of 3.7 years from creep tests under the gravity load of the bridge. The results indicate that the average creep deflection of the girders after 3.7 years was within the acceptable range. It was found that the creep deflection was affected by seasonal humidity and temperature. After 3.7 years of creep loading, the bridge model was loaded with sandbags and cast iron weight blocks until failure. The final failure mode was identified as the flexural failure of a section where a finger joint of one layer of the glubam girder was located.

The recently completed Aizhai Bridge in the west of Hunan Province in China is a long-span suspension bridge across a deep canyon. In view of the particular problems posed by the surrounding landscape and geologic conditions, and to minimize the impact of the bridge on the natural environment, a novel pylon-girder detached suspension structure was adopted, in which there is a large difference in the span between the main cable and the stiffening girder. As part of the design process, a method for stability analysis of the combined system of pylon, anchorage, tunnel, and rock cliff was developed. In addition, to solve the problems involved in the transportation and erection of the stiffening girder of such a long-span suspension bridge in a mountainous area, a novel girder-conveying track cable method was developed.

Finite-element (FE) simulations of the deformation behavior of a 5.4-m-long, 8-m-wide, and 0.27-m-thick stress-laminated timber bridge deck were conducted. The simulation results were compared with full-scale test results when using a load resembling an axle load placed near the edge and when cycling the load between a high and low value. Two separate approaches to nonlinear FE modeling were used. The first FE model simulates a frictional slip between the glulam beams with an elastic-plastic material model. The second FE model simulates a frictional slip by modeling each discrete contact surface between each beam in the deck. The results show good agreement between simulation and test results and reveal that the simulation model that models contact surfaces produces slightly better results at the expense of a greater modeling effort and increased computational time. Hysteresis in the load versus deformation curves is clearly visible and was due to significant slip between the glulam beams, which was successfully simulated.

An experimental program was conducted to investigate the application of headed glass fiber-reinforced polymer (GFRP) ribbed bars at the barrier wall-deck anchorage. Six full-scale barrier models of 1,200 mm in length were erected and tested under static monotonic loading to determine their ultimate load-carrying capacities and failure modes with respect to the barrier wall-deck anchorage. Four PL-2 barrier specimens were cast: two of them were of tapered face and the other two specimens were of parapet type with constant thickness. Each set had a steel-reinforced specimen as the control model and a GFRP-reinforced specimen. In addition, two PL-3 GFRP-reinforced specimens were erected with different spacing of GFRP bars. Each specimen was loaded laterally until collapse. This paper presents the results from these tests in the form of crack pattern, deflection history, and ultimate load-carrying capacity. Experimental results were compared with the design values specified in the Canadian bridge code for barrier anchorage into the deck slabs, showing a large margin of safety for the proposed GFRP-reinforced barriers. In addition, a parametric study was undertaken using finite-element analysis to investigate the applicability of resultant design loads prescribed by the Canadian bridge code for the design of the barrier wall-deck anchorage. The key parameters considered in this study were deck overhang length and thickness and barrier length. The data generated from this parametric study were used to develop set of empirical expressions for the factored applied moment at the barrier-deck interface, as well as the factored tensile force required to design the deck slab cantilever.

In recent years, horizontally curved bridges have been widely used in congested urban areas, where multilevel interchange structures are necessary for modern highways. In bridges with light curvature, the curvature effects on bending, shear, and torsional stresses may be ignored if they are within an acceptable range. Treating horizontally curved bridges as straight bridges with certain limitations is one of the methods to simplify the design procedure. Bridge design specifications and codes have specified certain limitations to treat horizontally curved bridges as straight bridges. However, these limitations do not differentiate between bridge cross section configurations, in addition to being inaccurate in estimating the structural response. Moreover, these specifications were developed primarily for the calculation of girder bending moments. To investigate the accuracy of these limitations, a series of horizontally curved, braced concrete slab-over steel I-girder and slab-on-concrete I-girder bridges were analyzed, using three-dimensional finite-element modeling, to investigate their behavior under dead loading. The major internal forces developed in the members were determined, namely, girder longitudinal bending stresses, vertical deflections, vertical support reactions, and bridge fundamental flexural frequencies for different degrees of curvature, span length, bridge width, and span continuity. Empirical equations for these straining actions were developed as a function of those for straight bridges. The stipulations made in bridge codes for treating a curved bridge as a straight bridge were then correlated with the obtained values from the finite-element modeling. Results proved that such code limitations were unsafe. Based on the data generated from this parametric study, sets of empirical expressions were developed to determine such limitations more accurately and reliably.

This paper presents details of the 2007 novel repair of a RC marine bridge that involved removal of concrete cover on each of the bridge’s seven crosshead beams and subsequent replacement of the cover with one of five different self-compacting concrete (SCC) options. Details of an on-site research initiative of this kind have not been published in the literature to date. It is anticipated that in time the bridge will yield valuable information relating to the marine durability of different SCC options. However, in the short term, there is a recognized need for data relating to the marine durability of SCC, a concrete technology that is becoming increasingly popular in bridge construction. To this end, this paper also presents details and results of a laboratory-based study aimed at investigating the marine durability of the five Ferrycarrig Bridge SCC options. The results of the laboratory study are also used, together with real marine bridge data, to make tentative predictions as to the time to corrosion initiation in the Ferrycarrig Bridge crosshead beams.

Reduced-order models (ROM) are computationally efficient techniques, which have been used widely for predicting unsteady aerodynamic response of airfoils and wings. However, they have not been applied extensively to perform unsteady fluid dynamic analysis of super long–span bridges. This paper discusses the application of a reduced-order computational fluid dynamics (CFD) model based on the eigensystem realization algorithm (ERA) in the aerodynamic analysis of three well-studied long-span bridges. The aerodynamic impulse responses of the Great Belt Bridge (GBB) and Stonecutters and Messina Strait Bridges were used to construct the aerodynamic ROM, and then the aerodynamic forces due to arbitrary inputs and their corresponding flutter derivatives were evaluated and compared to those of the model coupled with an advanced CFD code. Results demonstrate reasonable prediction power and high computational efficiency of the technique that can serve for preliminary design, optimization, and control purposes. The methodology described in this paper has wide application in many civil engineering problems where flexible structures interact with unsteady fluid mechanical phenomena.

The integration of large infrastructure with energy-harvesting systems is a growing field with potentially new and important applications. The possibility of energy harvesting from ambient vibration of bridges is a new field in this regard. This paper investigates the feasibility of energy harvesting for a number of trains considering their passage over a bridge. The power that can be derived from an energy-harvesting device due to a train crossing a bridge at different speeds is compared against typical demands of small wireless devices and is found to be adequate for powering such devices. These estimates of harvested energy also relate to the individual signatures of trains. In this work, the modeled dynamic responses of a bridge traversed by trains are compared against full-scale experimental analysis of train–bridge interactions. A potential application in structural health monitoring (SHM) using energy harvesting has also been demonstrated and compared with laboratory experimental data. Consistent and monotonic damage calibration curves have been constructed using estimated harvested energy.

The forces a walker exerts to an oscillating floor differ significantly from those exerted to a fixed floor. This is because of a natural and unconscious gait modification, deriving from the necessity of minimizing energy consumption while maintaining balance. Among other factors, these forces depend on the frequency and amplitude of oscillation of the floor, and this dependency is claimed to be responsible for most of the large amplitude vibrations observed on flexible footbridges. This paper reports the results of an extensive experimental campaign carried out using an instrumented treadmill, and aimed at evaluating the characteristics of the lateral force exerted by pedestrians when walking on a floor driven into a harmonic lateral motion with varying frequency and amplitude. The total measured force is separated into motion-dependent or self-excited components proportional to the floor velocity and acceleration, respectively, and an external excitation, which is independent of the floor motion. The variation of the acceleration- and velocity-proportional forces together with the characteristics of the spectra of the external excitation is discussed.