Journal of Bridge Engineering

A segmental precast posttensioned (SPPT) bridge pier is an economic recentering structural system. Understanding the seismic behavior of a SPPT system is an important step toward its application in high seismic zones. This paper presents a detailed three-dimensional finite-element (FE) model that was developed using the ABAQUS platform. A brief description and discussion of cyclic tests on eight large-scale SPPT piers is also presented. Four of the piers were constructed and tested to a predefined degree of damage. Then, these piers were retrofitted and retested. The FE models developed and presented in this paper predicted the backbone curves of the piers that were tested directly after construction with an average error of 7% for drift angles smaller than 2.5%. For drift angles greater than 2.5%, the average error reached 13%. For piers that were retrofitted and retested, the error in predicting the backbone curve depended on the state of damage before the retest. When preexistent microcracks were not severe, the FE models were able to predict the backbone curves with an error of approximately 12%. However, the error significantly increased and reached a value of approximately 31% when the preexistent microcracks were severe. In addition, the FE models confirmed the experimental observations and showed that the SPPT pier system is able to withstand large lateral drift angles with minimal damage. Finally, sensitivity analyses using the FE model showed that the model is sensitive to the softening behavior of the concrete material constitutive law.

Fatigue strength of welded structures is typically estimated through several approaches, including experimental S-N curves, the hot spot stress approach, and fracture mechanics. Recent work on the local stress field singularity of the weld toe has provided analytical expressions for the stress intensity factor of a crack emanating from the weld toe. Invoking the Paris law for fatigue crack growth together with the stress intensity factor expressions allows fatigue life to be evaluated in closed form. The fracture mechanics solution takes the same power-law form as the S-N curves and produces accurate lower bound estimates to the experimental fatigue data of stiffeners and attachments. The results show a strong relationship between the fracture mechanics, S-N curve, and hot spot approaches to fatigue that is based on two or more parameters from the local weld toe stress field. The two parameters may be tabulated as functions of weldment geometry and loading conditions for improved fatigue design and assessment calculations.

Ultrahigh performance concrete (UHPC) is an advanced cementitious composite material that has been developed in recent decades. When compared with more conventional cement-based concrete materials, UHPC tends to exhibit superior properties such as increased durability, strength, and long-term stability. This computational investigation focused on modeling the structural behaviors of UHPC components including prestressed UHPC AASHTO Type II girders. The concrete damaged plasticity model was tailored to model UHPC within a commercially available finite-element analysis package. This manuscript focuses on modeling three UHPC I-girders tested under flexural or shear loading configurations. The concrete damaged plasticity model was demonstrated to replicate both linear and nonlinear structural responses of I-girders reasonably well. A set of UHPC constitutive properties were developed that facilitate the model replication of the local and global responses observed in the series of physical tests.

Fatigue tests of full-scale orthotropic steel decks were recently conducted to evaluate the fatigue performance of rib-to-deck partial-joint-penetration (PJP) groove welded joints. The test results indicated that rib-to-deck joints are more prone to fatigue cracks in the deck plate than in the rib wall. A shallower weld penetration (for example, an 80% PJP) also appeared to have a slightly higher fatigue resistance than a deeper one (for example, a 100% weld penetration). These PJP welds were also more vulnerable to cracking initiated from the weld toe than from the weld root. Finite-element analyses of the test specimens, using the effective notch stress method, were performed to supplement the laboratory testing and provide additional information on the behavior of these welded joints. The analysis results showed a good correlation with the observed crack patterns. A parametric study also showed that the fatigue resistance of the PJP joint can be significantly influenced by the transverse loading location, deck plate thickness, and the weld penetration ratio. Increasing the deck plate thickness was effective in reducing the stresses, while the rib wall thickness had a little effect. A shallower weld penetration at the PJP joint appeared to have a positive effect in enhancing the fatigue resistance.

Displacement coefficients and profiles have been proposed as objective indexes for bridge structural condition evaluation by many researchers. In this paper, experimental data of the following type were collected for structural identification (St-Id) of a deteriorated bridge: (1) static displacement and strain measurements taken under proof-load level and (2) multireference impact testing (MRIT) data from one of the spans of a three-span, cast-in-place reinforced concrete T-beam bridge (Smithers Bridge). The MRIT was used to generate the modal data for computation of the modal flexibility and displacement profiles. Several significant obstacles were encountered during the St-Id of the Smithers Bridge including high damping level (which led to difficulties in identifying and selecting the poles), finite-element (FE) model updating challenges, and correlation of the MRIT results with truck load test measurements. The first challenge was addressed through the use of the complex mode indicator function method of modal identification, which is capable of identifying highly damped modes. Then the updating of the FE model was accomplished using the Strand7 FE analysis package coupled with the MATLAB application programming interface. Finally, to allow for direct comparison of the MRIT and truck load results, two strategies were employed. The first involved the redistribution of truck load force to the MRIT degrees of freedom and the second utilized interpolation functions for modal expansion of the MRIT results to include the truck tire locations. The St-Id procedure used during this application was designed to mitigate blatant human error and epistemic uncertainty in the data interpretation process. Successful results from the MRIT demonstrated the reliability of the applications for bridge condition assessment based on impact testing.

Railway traffic volumes in China have increased dramatically with the fast development of the Chinese economy in the past 20 years. The load frequency spectra of bridges have also changed as a result. Therefore, it is necessary to update the fatigue damage coefficient used in the railway bridge design code accordingly. This paper discusses the updating work that involved a series of analyses and calculations based on the information obtained from a nationwide investigation of various railway lines. The newly updated fatigue damage coefficient has been recommended for the Chinese railway bridge design code.

The conformity between predicted and actual configurations of a suspension bridge is examined through a field survey with the compensation of temperature effects. The tension in the main cable is estimated from the surveyed configuration utilizing force equilibriums at the cable junction nodes. The measured hanger tensions and rigorous dead load information are also incorporated. The as-built configuration of the bridge shows fairly good agreement with the designed shape. The reproducibility of the dynamic properties is also examined for dominant vertical modes. The only tuning in the connection conditions of bearings produces natural frequencies that are in good agreement with the measured values.

The introduction of steel reinforcing bars having yield strengths exceeding 517 MPa (75 ksi) and often approaching 827 MPa (120 ksi) may allow for significant economies to be realized, particularly when used in conjunction with high-strength concrete. One implication of the adoption of higher-strength reinforcing steel is that reinforcing bar stresses (and therefore strains and consequently crack widths) at service load levels are expected to be greater than when conventional bars [having a yield of 414 MPa (60 ksi)] are used. A study of flexural crack widths of beams reinforced with high-strength ASTM A1035 reinforcing steel is presented. Discussion focuses on the behavior at loads corresponding to longitudinal reinforcing bar stresses of 248, 414, and 496 MPa (36, 60, and 72 ksi), representing service load levels (i.e., 0.6$f_y$) for steel having $f_y$ = 414,690, and 827 MPa (60, 100, and 120 ksi), respectively. Average measured crack widths obtained from a series of flexural beams having reinforcing ratios ranging from 0.007 to 0.023 are found to be below the present AASHTO de facto limits for Class 1 and Class 2 exposure. The demonstrated conservativeness of existing ACI and AASHTO crack control provisions allows present specifications to be extended to the anticipated higher service level stresses associated with the use of high-strength reinforcing steel.

Calculating wind resistance is an important process in the design of highway bridges. The current codes of many countries include different rules and formulas regarding the calculation of wind resistance. In this paper, the transverse-direction wind loads on long-span girder bridges with tall piers were calculated using six codes from different countries under various terrain, pier height, and girder length conditions. The pier-bottom shear force and moment results of transverse wind loads calculated using these six codes were compared with those obtained using the buffeting frequency domain method. Results showed that, in Class B terrain, wind load results predicated on China’s 2004 general codes for the design of highway bridges and culverts, China’s 2004 wind-resistant design specifications for highway bridges, Japan’s 2007 wind-resistant design manual for highway bridges, and Part 2 of Britain’s 2006 steel, concrete, and composite bridge specifications for loads resembled each other closely. Some difference was found to exist among Classes A, C, and D terrain. The 2007 AASHTO LRFD bridge design specifications and China’s 2001 load codes for the design of building structures showed significant differences from the other four codes on all kinds of terrain. The applicability of the wind load rules in the AASHTO LRFD bridge design specifications to long-span girder bridges with tall piers merits further discussion. China’s wind load calculations of load code for the design of building structures mainly depended on the empirical parameters of architectural structures with large dimensions, and had limited applicability to bridge structures. For long-span girder bridges with tall piers, such as bridges with span length-to-width or -depth ratios exceeding 30, or pier height-to-transverse-width ratio exceeding 10.7, the wind load calculated using these codes was generally underestimated due to the neglect of the effects of aeroelastic forces, which must be taken into account in the design of these kinds of bridges.

A new beam element has been developed for the static and dynamic analysis of incrementally launched bridges. The element can describe the deformation subjected to a transverse constraint at an arbitrary point on the beam, thus enabling direct simulation of the superstructure with a continuously position-varying support during the incremental launching of bridges. This element significantly simplifies the finite-element modeling of launched bridges and greatly reduces the computational cost. Some numerical examples are given to show the superiority of the proposed element.