Journal of Bridge Engineering

Accurate prediction of instantaneous and time-dependent deformation of superstructure in-span hinges is important for preventing a mismatch of bridge decks. Time-dependent deflection of in-span hinges hinge curl in posttensioned bridges depends on the construction sequence and the material time-dependent properties. Structural analysis software is an important tool for estimating time-dependent deformations. Computational modeling was conducted to calculate the hinge curl in posttensioned bridges considering two approaches, the spine model and the three-dimensional finite-element model. Both modeling approaches estimated well the actual deformation behavior of the bridges. Based on the measured and computational data, a new simple method is proposed in this study for estimating the hinge curl during and after construction. The computational results were in good agreement with those estimated using the proposed simple method. Parametric studies on the effect of geometrical changes revealed that horizontal curvature and skew angle have a minimal effect on hinge curl.

Perfobond rib shear connector (PBL) is capable of transferring large internal force between steel and concrete components. It has been widely used in composite bridges as a key load-transferring component. In this paper, the load-transfer mechanism of the PBL shear connector group is investigated theoretically and experimentally. An analytical model was developed based on load-slip characteristics of a single shear connector and load-deformation compatibility of a perforated steel plate and concrete component. The model was validated through full-scale connection loading experiments. Test results indicate that the applied load is unevenly distributed to multiple layers of PBL shear connectors in a connector group in the elastic stage, and the load becomes more evenly distributed as plastic deformation of the connectors takes place. The presented analytical model provides an efficient way for analyzing and designing a PBL shear connector group. The analytical results indicate that increasing the number of connectors in heavily loaded layers helps effectively reduce the load shared by each connector in these layers under design loads.

Precast adjacent box girder bridges have become a preferred solution in several states due to their simple structure, economy, and ease of construction. However, longitudinal cracks often appear along the shear keys between adjacent box girders. With its superior strength and durability, ultrahigh-performance concrete (UHPC) has been used as an alternative grout material to reduce shear key cracking and enhance load transfer. The objective of the present research was to evaluate the performance of UHPC in shear keys using direct shear, direct tension, and flexural tests. Also, this study determined the effectiveness and functionality of shear reinforcement bars by applying direct shear load on specimens with shear reinforcement. In the direct shear test, a steel frame was placed around the specimens to allow the shear key to experience pure shear force. The direct shear test established the cracking threshold and ultimate shear strength of each shear key with and without shear reinforcement bars. The test results show that the average maximum shear capacity for the UHPC shear key without shear reinforcement bars exceeded that determined from past research for any grout material and any shear key configuration. Furthermore, the average maximum shear capacity increased by a factor of 1.81 with shear reinforcement bars. The enhanced shear strength of the UHPC shear key may have an impact on the analysis and design of UHPC connections in bridges.

Bridges are important components of the transportation network that should maintain mobility and accessibility even after severe earthquakes. The current design philosophy of earthquake-resistant bridges requires the disastrous seismic energy to be dissipated in hinges that are formed in the piers, while the deck should remain essentially elastic. However, postearthquake restoration of damaged piers is challenging, time-consuming, and causes traffic disruptions. In this context, this paper proposes a novel resilient hinge (RH), that is cost-effective and has minimal damage during earthquakes. The RH is a versatile substructure that dissipates energy through the yielding of easily replaceable steel bars, thus offering rapid restoration times. It is designed to have recentering capabilities because a number of steel bars remain primarily elastic. Numerical models of single-column piers with the proposed hinge were studied and compared with conventional reinforced concrete piers to investigate the efficiency of the design. It was found that the piers with RHs exhibit a significant reduction in residual drifts when compared with the ones of the conventional piers. Application of the proposed philosophy in irregular bridge models enables a more rational and even distribution of ductility requirements along the bridge piers.

A database of 253 unbonded tendon-reinforced members was assembled and analyzed with a focus on $\Delta f_{\text{ps}}$. Large scatter was observed and gaps were identified in previous databases due to possibly unsuitable inclusion of certain testing programs. The influence of several geometric and material properties was analyzed using a covariance analysis, and significant differences between simple-span and continuous members were observed, although some prediction methods do not differentiate between the two. The assembled prediction models for $\Delta f_{\text{ps}}$ had evaluation statistics ranging from 1.84 < $\lambda$ < 4.11 and 0.06 < R² < 0.16 and indicating relatively poor accuracy and precision. Modifications to the scaled plastic hinge length $\psi$ for different subsets (simple span, continuous, internally unbonded, and externally unbonded) were suggested to provide the most accurate and precise prediction when compared with the available methods. The proposed method, a modified version of the bridge design code prediction, provides the most accurate ($\lambda$ = 1.34) and precise (R² = 0.27) prediction and does not increase complexity.

The current codes and specifications use the equivalent beam-column method to predict the in-plane stability capacity of concrete-filled steel tubular (CFST) arches. Using this method, the effects of the rise-span ratio and the nonuniform moment on the stability capacity of CFST parabolic arches are not considered. This may induce a difference between calculation results and actual structural stability capacity. To study the effects of the rise-span ratio and the nonuniform moment, six fixed CFST parabolic arches, with rise-span ratios of 1/4.5, 1/6, and 1/9, were tested and analyzed in this study. The failure patterns and mechanisms were studied. The confining effect of the steel tube to the concrete at failure was investigated. The influence of the rise-span ratio and loading conditions on the in-plane stability of fixed CFST arches was also considered. A nonlinear elastic-plastic finite-element (FE) model was used to predict the buckling behavior of the fixed CFST parabolic arches. Based on the test and the FE results, a design equation is proposed for the design of in-plane stability of fixed CFST parabolic arches under combined bending and compression.

A new framework for bridge-deflection estimation through inclinometer data is presented in this paper. Whether the structure is damaged or not, deflection could be precisely estimated via the finite-element model (FEM) combined with the partial least-square regression (PLSR) method. In addition, damage localization is achieved at the same time. First, the deflection of a damaged structure is equivalent to that of an undamaged structure but subjected to special virtual loads. Second, the basis functions used in regression are calculated by the FEM of the undamaged structure rather than pure mathematical derivations. Third, the PLSR model is built on the basis of these basis functions and measured inclination data. By solving the PLSR equation, all the nodal inclinations and corresponding nodal loads of the structure could be obtained despite a limited number of measured nodes. Finally, the rotation-displacement transfer matrix is derived to reconstruct deflection from estimated inclinations, and the changes in nodal loads are served as damage indicators. To verify its effectiveness, numerical simulations considering various damage scenarios and different noise levels are performed. The results indicate that the proposed method is quite accurate and reliable in deflection estimation, and it could provide rough damage localization as well, which reveals a great potential in the field of structural health monitoring.

Curved bridges provide a vital benefit to the nation’s infrastructure system by allowing for accessibility and ease of transition in irregular highway layouts. Curved bridges using straight prestressed concrete I-girders with curved decking can fulfill this need. A number of such bridges have been constructed both in seismically and nonseismically active zones. This paper determines the seismic vulnerability sensitivity of the bridges with vastly different configurations via use of conventional fragility-assessment techniques. Experimental design established a statistical setting using core variables to produce a wide variety of hypothetical bridges to represent both as-built and proposed bridge configurations. Each bridge was designed following the strength and serviceability limit states stipulated by current bridge design specifications. As part of the sensitivity analysis, nonlinear time history analyses (NLTHAs) using numerous synthetic ground motions were performed to establish seismic demands on critical bridge components. Using probabilistic seismic demand models (PSDMs), component and system-level fragility curves were generated. The resulting fragility data were scrutinized to explore the effects of the different design parameters on seismic vulnerability of the bridges. The results indicate that the shorter-span bridges with a tighter radius of curvature are less sensitive to seismic excitations than those with straighter decking, indicating that a span length-to-radius of curvature ratio (S/R) for both single and multispan bridges is statistically determined to be the most influential parameter.

Shear keys as sacrificial components are widely used in cap beams and abutments of highway bridges to limit the transverse displacement of superstructures and avoid damage of substructures. To investigate the seismic capacity of bridge exterior shear keys, six exterior shear key specimens were designed on the basis of current Chinese seismic design guidelines of highway bridges and subsequently tested under monotonic lateral loading. The influence of vertical and horizontal reinforcement ratios on the seismic capacity of the bridge shear keys was studied. Two typical failure modes of the exterior shear key specimens, diagonal tension failure and sliding shear failure, were observed during the tests. The reinforcement ratios of the shear key and cap beam have significant influence on the seismic capacity of exterior shear keys. Moreover, different analytical models corresponding to the two failure modes were developed to predict the seismic capacity of the shear key specimens in this paper. Compared with the experimental results, the two analytical models proposed in this study can better predict the load-carrying capacity of the shear key specimens than the classical analytical models.

This paper presents the seismic behavior of hollow-core fiber-reinforced polymer–concrete–steel (HC-FCS) columns. The typical HC-FCS column consists of a concrete wall sandwiched between an outer fiber-reinforced polymer (FRP) tube and an inner steel tube. The inner steel and outer FRP tubes provide continuous confinement for the concrete shell; hence, the concrete shell achieves significantly higher strain, strength, and ductility than unconfined concrete in conventional columns. Three large-scale HC-FCS columns were investigated in this study. Each column had an outer diameter of 610 mm (24 in.) and a height-to-diameter ratio of 4.0. The steel tube was embedded into a reinforced concrete footing with an embedded length of 1.6–1.8 times the steel tube diameter, whereas the FRP tube only confined the concrete wall thickness and truncated at the top of the footing level. In general, the columns exhibited high lateral drift, reaching to 11.6%, and failed gradually as a result of concrete crushing and local steel tube buckling. An equation to determine the steel tube development length of HC-FCS columns was introduced based on an extensive finite-element study. The finite-element analysis was validated with finite-element models. In addition, this paper introduces a quick-repair technique for HC-FCS columns. Guidelines for the preliminary design of HC-FCS columns under seismic loading are also presented to help implement this new technology.

This paper proposes different optimization schemes for enhancing the performance of conventional continuous composite girder bridges with corrugated steel webs. In particular, for the positive moment region, the substitution of a ribbed steel plate for the reinforced concrete bottom flange is proposed for optimizing such bridges. Three-dimensional finite-element analysis was used to preliminarily validate this optimization scheme based on the background project, Dongbaohe Xinan Grand Bridge. An experimental study revealed that the optimization scheme can afford advantages, such as reduced self-weight, avoidance of cracking in the bottom flange, and convenient construction. If the steel plate with proper thickness is used, higher flexural stiffness and load capacity can be achieved as additional advantages due to the enhanced steel ratio of the cross section. For the negative moment region of the bridge, the optimization scheme was implemented in two parts identified as Optimization Schemes I and II. In Scheme I, corrugated steel plate–concrete composite webs were used, whereas a steel–concrete composite bottom flange was further adopted in Scheme II. Compared to the conventional scheme, both Optimization Schemes I and II significantly reduced the shear stress in the corrugated steel web and at the steel–concrete interface due to the lined concrete in the web. Thus, it can be deduced that the applied load corresponding to the yield of the corrugated steel web will be enhanced; namely, the shear capacity will be enhanced. Because shear connection failure was prevented in both optimization schemes, there were remarkable improvements of the load capacity and ductility of the girder. The confining effect of the lined concrete decreased the prestress lead-in ratio, but not significantly. In addition, Optimization Scheme II afforded much greater construction convenience compared to both Optimization Scheme I and the conventional scheme.