Journal of Bridge Engineering

The Shandong Binzhou Yellow River Highway Bridge is a three-tower, cable-stayed bridge in Shandong Province, China. Because the stay cables are prone to vibration, 40 magnetorheological (MR) fluid dampers were attached to the 20 longest cables of this bridge to suppress possible vibration. An innovative control algorithm for active and semiactive control of mass-distributed dynamic systems, e.g., stay cables, was proposed. The frequencies and modal damping ratios of the unimpeded tested cable were identified through an ambient vibration test and free vibration tests, respectively. Subsequently, a series of field tests were carried out to investigate the control efficacy of the free cable vibrations achieved by semiactive MR dampers, “Passive-off” MR dampers and “Passive-on” MR dampers. The first three modal damping ratios of the cable incorporated with the MR dampers were also identified from the in situ experiments. The field experiment results indicated that the semiactive MR dampers can provide significantly greater supplemental damping for the cable than either the Passive-off or the Passive-on MR dampers because of the pseudonegative stiffness generated by the semiactive MR dampers.

The lack of safety of deck slabs in bridges generally causes frequent repair and strengthening. The repair induces great loss of economy, not only due to direct cost by repair, but also due to stopping the public use of such structures during repair. The major reason for this frequent repair is mainly due to the lack of a realistic and accurate assessment system for bridge decks. The purpose of the present paper is therefore to develop a realistic assessment system which can estimate reasonably the safety, as well as the service life of concrete bridge decks, based on the deterioration models that are derived from both the traffic loads and environmental effect. A deterioration model due to chloride ingress is first established. The damage models due to repetitive traffic loads considering the dry and wet conditions of deck slabs are proposed. These models are used to calculate the remaining life of a bridge deck slab. A prediction method for service life of deck slab due to loading and environmental effects is developed based on material, as well as structural evaluation. The proposed method includes the assessment of corrosion in material level, and the analyses of flexure, shear, and fatigue in structural level. Finally, an assessment system for prediction of safety and remaining service life is developed based on the theories established in this study. The developed assessment system will allow the correct diagnosis of damage state and the realistic prediction of service life of concrete decks in girder bridges.

Plain and fibrous latex modified concrete and microsilica concrete overlays with acceptable laboratory strength and durability characteristics were installed on a full-scale prototype bridge deck for field performance evaluation. After $1\text{year}$ of exposure to drying shrinkage, temperature variations, and freeze–thaw cycles, no cracking or debonding were observed in the overlays. The bond strengths at $28\text{days}$ and at $1\text{year}$ were acceptable for all overlay types due to the excellent curing and surface preparation using water-jet blasting. The prototype bridge was then statically tested before and after applying low-cycle fatigue loading simulating AASHTO HS20 truck service load, overload, and ultimate load. Minor bond strength deterioration at the maximum negative moment region and slight bridge stiffness degradation were observed after each load case. Significant enhancement in the bridge stiffness was observed after installation of the overlays. Also, the overlay with synthetic fibers showed better crack bridging action than the overlay with steel fibers.

Light gauge metal sheeting is often utilized in the building and bridge industries for concrete formwork. Although the in-plane stiffness and strength of the metal forms are commonly relied upon for stability bracing in buildings, the forms are generally not considered for bracing in steel bridge construction. The primary difference between the forming systems in the two industries is the method of connection between the forms and girders. In bridge construction, an eccentric support angle is incorporated into the connection details to achieve a uniform slab thickness along the girder length. While the eccentric connection is a benefit for slab construction, the flexible connection limits the amount of bracing provided by the forms. This paper presents results from the first phase of a research study investigating the bracing behavior of metal bridge deck forms. Shear diaphragm tests were conducted to determine the shear stiffness and strength of bridge deck forms, and modified connection details were developed that substantially improve the bracing behavior of the forms. The measured stiffness and strength of diaphragms with the modified connection often met or exceeded the values of diaphragms with conventional noneccentric connections. The experimental results for the diaphragms with the modified connection details dramatically improve the potential for bracing of steel bridge girders by metal deck forms.

Sealing of bridge expansion joint systems is important to protect the structural components below the joint. An elastomeric foam-type joint sealant has been developed for sealing small-movement bridge expansion joints. Laboratory tests including tension, compression, shear, bonding, stress relaxation, cure rate, tack-free time, and water tightness were performed on this sealant. In addition, loading-unloading behavior in tension and compression and effects of immersion in saturated saltwater solution on its engineering properties were investigated. The silicone foam sealant showed an increase in volume of $\sim 70$ % on curing and attained approximately 80% of the 21-day curing strength in the first 7 days. Tack-free time for the foam sealant was below $1.5\mathrm{h}$ and comparable to that for the solid sealant. The mechanical test results indicated lower stiffness, greater extensibility, and better bonding associated with the foam sealant compared to the solid (unfoamed) sealant. The foam sealant exhibited smaller loss in extensibility at failure due to saltwater immersion compared to the solid sealant. While in tension both sealants exhibited similar rates of stress decay, in compression the foam sealant was found to relax faster than the solid. Neither sealants exhibited any water leakage during a $96\text{-}\mathrm{h}$ test period.

An existing mountable safety barrier system, previously crash tested successfully on a wood bridge deck, was evaluated for use on a fiber reinforced plastic (FRP) bridge deck. In an attempt to avoid expensive full-scale crash testing, components of the existing system were evaluated using worst case conditions on two dynamic bogie crash tests and a series of computer simulations using nonlinear finite-element analysis. Simulation results closely approximated the physical results, with both displaying similar deformation, damage, and force levels. Both testing and simulation demonstrated that the barrier should function sufficiently if used on the FRP deck system. Further, the development of an accurate model makes it possible to evaluate the potential success of the existing system for use on other bridge decks. As an example, a more rigid bridge deck, similar to reinforced concrete, was evaluated. Results showed that due to the stiffer deck, more of the impact energy must be absorbed by the posts and attachment hardware, resulting in significantly more deformation than when used on the flexible FRP deck.

Simplified moment redistribution procedures based on shakedown have recently been approved by AASHTO LRFD Bridge Design Specifications (AASHTO 2004). These procedures are currently only applicable for homogeneous girders, and thus, the objective of this study is to evaluate whether these procedures can be further applied for hybrid HPS 485W girders. A parametric study is carried out using validated three-dimensional finite-element (FE) analyses to study the inelastic behavior of hybrid HPS 485W girders in negative bending for this purpose. The effective plastic moments obtained from the FE studies are compared with those from the proposed prediction equations, where good correlation is observed. A design example of a three-span slab-on-girder bridge with hybrid HPS 485W girders using both elastic design and the simplified moment redistribution procedures is also presented, where it is shown that the use of moment redistribution procedures results in a negative bending section that is 13% lighter than the corresponding elastic design.

Special attention is required in the construction of horizontally curved steel I-girder bridges due to coupled effects of primary bending and torsional forces. Misguided steel erection procedures can lead to undesired stresses, deflections, and rotations in these types of bridges, resulting in a structure with misaligned geometry and in an unknown state of stress. Further complicating the issue, little guidance related to curved bridge behavior during construction is provided by current design codes, leaving contractors and designers uncertain as to the most appropriate steps to take to achieve an efficient, safe structure. A horizontally curved, six-span steel I-girder bridge located in central Pennsylvania that experienced severe geometric misalignments and fit-up complications during steel erection was studied to investigate curved girder behavior during construction. The structure was monitored during corrective procedures intended to realign it with the design geometry, and field data used to calibrate a three-dimensional computer model generated via SAP2000. The techniques and assumptions proven in the calibration process were used to create a numerical model of a three-span continuous portion of the bridge, which was the subject of several analyses exploring the effects erection sequencing, implementation of upper lateral bracing, and use of temporary supports had on the final deformed shape of the curved superstructure. Findings indicated that using paired girder erection produced smaller radial and vertical deformations than single girder techniques for this structure, and that the use of lateral bracing between the fascia and adjacent interior girders and the placement of temporary shoring towers at span quarter points are both effective means of further reducing levels of deflection.

Horizontally curved, steel girder bridges are often used in our modern infrastructural system. The curve in the bridge allows for a smother transition for traffic, which creates better road travel. However, some of the disadvantages of horizontally curved bridges are that they are more difficult to analyze, design, and sometimes construct in comparison to conventional straight bridges. This study focuses on a three-span, curved steel I-girder bridge which was tested under three boundary condition states to determine it’s response to live load. The measured live-load strains were used to calibrate a finite-element model. The finite-element design moments and distribution factors for the three condition states were then compared with the results based on the V-load method. These different boundary conditions provided the researchers a unique opportunity to evaluate the impact that these changes had on the bridges behavior. It was found that while the V-load method produced positive bending moments that were close to the finite-element moments for some of the girders, this was a result of the V-load moment being unconservative and the distribution factor being conservative.

Horizontally curved steel I-girder bridge systems tend to deflect and rotate out of plane under the action of gravity. Oftentimes, this response will lead to a condition wherein the subsequent girder cross-sectional orientation is one where the web is out of plumb. Currently, there exists little guidance concerning what effect this web out of plumbness has on structural performance. As a result of this lack of guidance from design specifications, there is tendency within current practice to work to alleviate the out of plumb condition through various detailing and erection strategies, since the performance implications of its presence within the structure are poorly understood. The present research employs nonlinear finite-element modeling strategies to study the various effects that web out of plumbness has on flange tip stresses, vertical and lateral deflections, cross-sectional distortion, and cross-frame demands. The focus of the present work is the construction stage, and thus steel dead load is the governing loading condition treated. Web out of plumbness magnitudes of up to 5° are considered.

Reinforced concrete (RC) structural elements with box sections are commonly used in the horizontal and vertical structures of bridges. Reinforced concrete structures in bridges have often failed under the combined forces of bending, axial load, shear, and torsion caused by wind and earthquake. It is very important to find out the failure mechanism and to give a unified failure expression of RC box sections under these combined forces. In this paper, a theoretical study and deduction of the unified failure expression on the reinforced concrete members with box sections under combined bending, shear, axial force, and torsion were carried out with a stress equilibrium assumption. The results of a theoretical analysis were compared with the experimental results of reinforced box girders under torsion, bending, and shear forces. Both the theoretical results and the test results showed a good correlation, thus demonstrating that the unified failure expression for reinforced concrete members with box sections can be used in the static calculation of such bridge members.

Damage fragilities describe the probability that a bridge will incur certain (discrete) damage states conditioned on the intensity of the earthquake it may experience. Reinforced concrete box girder highway overpass bridges are prevalent among the total inventory of bridges in California. For this class of bridges, a method for computing damage fragilities for three damage states (concrete cover spalling, longitudinal bar buckling, and column failure) based on the bridge force reduction factors ( $R$ -factors) is derived in this paper. Bridge damage fragilities are described by equations relating the median intensity and uncertainty of ground motion to discrete damage states of column concrete cover spalling, column bar buckling, and column failure using the bridge $R$ -factor as the principal parameter describing the bridge structure. Such damage fragility equations are furnished for earthquake intensities measured using pseudospectral acceleration $\left(Sa\right)$ and cumulative absolute displacement (CAD) in both the bridge longitudinal and transverse directions.

This study presents an experimental program to investigate the shear capacity of precast reinforced concrete box culverts. Each culvert was subjected to monotonically increasing load through a $254\mathrm{mm}\times 508\mathrm{mm}$ $(10\mathrm{in.}\times 20\mathrm{in.})$ load plate in order to simulate the HS20 truckload per AASHTO 2005. Instrumentation included strain gauges, high-resolution laser deflection sensor, and automated data acquisition. Four tests were conducted on $1.22\mathrm{m}\times 1.22\mathrm{m}\times 1.22\mathrm{m}$ $(4\mathrm{ft}\times 4\mathrm{ft}\times 4\mathrm{ft})$ box culverts. The location of the load plate was varied to identify the position, which introduces the maximum shear stresses. Laser sensor data and dial gauge readings were recorded to measure the deflection profile of the box culvert. Strain gauges were placed on the steel reinforcement to measure axial strain at locations of maximum positive and negative bending moments. The test results include reporting the loads at which each crack initiated and propagated. The displacement profile of the top slab from the laser instrumentation output along with the load versus maximum deflection for each culvert is also reported.

The simplified equations available at present to predict the collapse loads of single-cell concrete box-girder bridges with simply supported ends are based on either space truss analogy or collapse mechanisms. Experimental studies carried out by various researchers revealed that, of the two formulations available to predict the collapse load, the one based on collapse mechanisms is found to be more versatile and better suited to box sections. Under a pure bending collapse mechanism, the existing formulation is found to predict collapse load with high accuracy. However, in the presence of cross-sectional distortion, there are significant errors in the existing theoretical formulation. This paper attempts to resolve this problem, by proposing a modification to the existing theory, incorporating an empirical expression to assess the extent of corner plastic hinge formation, under distortion–bending collapse mechanism. The modified theoretical formulations are compared with the experimental results available in the literature. New sets of experiments are also conducted to validate the proposed modified theory to estimate the collapse load. In all cases, it is seen that the modified theory to predict the collapse load match very closely with the experimental results.

The isolation bearings are widely used in earthquake prone areas to protect the structure from seismic forces. The isolation bearing consists of an isolator to increase the natural period of the structure away from the high-energy periods of the earthquake, and a damper to absorb energy in order to reduce the seismic force. The most common isolation bearings used are lead–rubber bearings. They combine the function of isolation and energy dissipation in a single compact unit, giving structural support, horizontal flexibility, damping, and a centering force in a single unit. The relation between the horizontal force and horizontal displacement of the isolation bearings is nonlinear; to calculate the stiffness and the damping constant, which correspond to effective design displacement, the nonlinear behavior is expressed by bilinear behavior. This technical note presents new relations to calculate yield force, horizontal displacement, and damping.