Prestressed Concrete Box Girder Bridge Research Articles

Propagation Effect Analysis of Existing Cracks in Box Girder Bridges Based on the Criterion of Compound Crack Propagation

Cracking in concrete box girder bridges will have a significant impact on the safety and durability of the structure, and many box girder bridges which are in service have undergone varying degrees of cracking. Currently, the safety design of actual bridge projects place an emphasis on the stress or the load value of a cross section at the limit value specified in the code for safety control. This design method assumes that the member itself is of uniform and continuous material and is internally undamaged. However, the bridge structure is more or less cracked to varying degrees during the period from casting to construction to operation of the concrete members. In this paper, a finite element computational model of a three-span prestressed concrete box girder bridge with existing cracks is established based on the fracture mechanics theory, and the critical parameters of crack extension are introduced to evaluate the extension state of cracks. At the same time, the extended stability of the existing cracks of the box girder bridge is analyzed by considering the temperature effect, vehicle loading, and prestressing loss, and the sensitivity of crack extension under each working condition is investigated. The results show that, with the increase in crack length and depth, the crack expansion is promoted, but the effect is relatively small, and the maximum stress intensity factor is only 6.48 MPa mm1/2. Under the multi-factor coupling effect, the cracks show a composite crack expansion dominated by type I cracks, the longitudinal cracks of the existing base plate are in a stable state, the maximum value of the crack expansion critical parameter of the vertical cracks of the webs reaches 1.087, and there is a tendency to expand locally. The maximum value of the critical parameter for crack extension of the vertical crack in the web plate reaches 1.087, and there is a tendency towards local expansion. The crack extension evaluation criteria proposed in this paper have a certain reference value for crack extension research on similar concrete box girder bridges and provide a scientific basis for the optimized design of similar bridges.

Experimental and numerical investigation on deck system of a 102 m simply supported prestressed UHPC box-girder highway bridge

To address two main challenges (excessive mid-span deflections and numerous cracks in the main girder) in long-span prestressed concrete (PC) box-girder bridges, this paper proposes a long-span simply-supported UHPC box-girder bridge. In comparison to conventional PC box-girder bridges with three-dimensional prestress, the proposed UHPC box-girder consists only one-dimensional (longitudinal) prestress, and the thickness of the bottom/top plate and web of the UHPC box-girder are relatively thin and are strengthened with dense diaphragms and stiffening ribs. The 4th Beijiang River Bridge adopts this type of bridge with a span of 102 m, which is the longest span simply supported prestressed UHPC box-girder highway bridge in the world. Considering the fact that the thickness of the top plate of the UHPC box-girder is relatively thin (only 20 cm) and the transverse prestress is removed from the top plate, thus, under the direct action of wheel loads, the risk of bridge deck cracking may correspondingly increase. To investigate the mechanical behavior of the deck system of UHPC box-girder bridges, a 1:2 scaled experimental specimen associated with the field bridge is tested. The mechanical behavior of the new deck system is investigated and discussed. It is found that because the support strength of the stiffening rib is significantly weaker than that of the web, the UHPC deck slab should still be regarded as a two-way slab rather than a one-way slab in the elastic stage. In addition, although the test load location is unfavorable to the UHPC deck slab and the first crack appears on the UHPC deck slab, this deck system finally suffers from bending failure of the transverse rib. Furthermore, finite element analysis is carried out to study the mechanical behavior of this new deck system. Parametric analysis considers some factors including the reinforcement ratio in the transverse rib, the height of the transverse rib, and the space between transverse ribs. The results provide a good reference for design and optimization in the new deck system of UHPC box-girder bridges.

Dynamic characterization of a curved nine-spans pre-stressed concrete box girder bridge with half-joints

In recent years, the failure of many bridges has pressed governments all over the world to increase investments and to enact new monitoring regulations. In the Italian context, the Ministry of Infrastructure and Transport answered to that challenge by enacting the new Guidelines on Risk Classification and Management, Safety Assessment and Monitoring of Existing Bridges, in 2022. In this new regulation, Structural Health Monitoring (SHM) plays a fundamental role, complementing traditional periodic inspections by carrying out low intrusive non-destructive analyses. In this field, Operational Modal Analysis (OMA) is a vibration-based method consisting in the processing of the ambient accelerations recorded on the structure in order to extract and track its modal features. The final goal of continuous OMA is the timely identification of possible damage-induced persistent variations in the modal features of the monitored structure. This is why one of the most recent advances in OMA algorithms is related to the development of continuous Automated OMA embedded in high-potential software, to enable the infrastructure management authorities to realize large-scale monitoring of bridge networks. Many road bridges are however long multi-span bridges which require numerous sensors for their monitoring, thus making automated OMA especially challenging from the computational point of view. The aim of the work is to contribute to a more computationally affordable automated OMA for long bridges, by proposing to subdivide the OMA task considering suitable selections of subgroups of sensors. The proposed approach is illustrated in a case study consisting of a curved nine-spans pre-stressed concrete box girder bridge with 10 half-joints and equipped with more than 50 sensors.

Damage mechanism and damage evaluation of PC box girder bridge subjected to overheight vehicle impact

AbstractAccidental collisions from overheight vehicles often result in significant damage of bridges. To ensure the safety of the bridge structure, it is essential to develop a method to evaluate the damage caused by these impact loadings. This study aims to investigate the damage mechanism of a prestressed concrete (PC) box girder bridge subjected to overheight vehicle impact using the finite element analysis method. Parametric analyses were performed to study the effects of various factors on the impact force and deformation performance of the bridge. In addition, a damage assessment formula, based on the vertical residual bearing capacity, is proposed to evaluate the damage state of the impacted PC box girder. A mass–velocity (m–v) curve is developed to characterize the damage levels of the impacted PC girder under different vehicle velocity and mass conditions. Then, a theoretical equation for predicting the maximum impact force during the vehicle‐bridge collision is developed. The numerical analysis results show that vehicle‐related parameters have a significant influence on both impact force and local damage of the PC box girder bridge. The proposed mass–velocity (m–v) curve can be used to evaluate the damage state of the PC box girder by relating the performance levels of the girder to each damage index. Moreover, the predicted maximum impact force can be used as an important index to assess the extent of the local damage of the PC box girder.

Time-Dependent Reliability Assessment of Long-Span PSC Box-Girder Bridge Considering Vehicle-Induced Cyclic Creep

The neglect of the cyclic creep of concrete induced by vehicles may overestimate the deflection reliability of long-span prestressed concrete (PSC) box-girder bridges and increase structural safety risks. In this paper, a novel method considering the combined effects of the shrinkage, static creep, and cyclic creep of concrete and the stress relaxation of prestressed tendons is proposed to assess the time-dependent deflection reliability of PSC box-girder bridges. By employing the Kelvin chain model, the conventional integral-type method for calculating the static creep of concrete is converted to rate-type creep analysis, which has a higher computational efficiency and can consider various nonlinear effects. The cyclic creep of concrete is estimated by the fatigue mechanics-based model and integrated into the quasi-elastic incremental constitutive model. The proposed constitutive model is implemented in a general finite-element program DIANA, in which the mechanical behavior of the thin-walled box girder is described by the composite degenerated shell elements. An importance sampling method is applied when estimating the deflection reliability to balance the computational accuracy and efficiency. The proposed method is applied to a long-span PSC box-girder bridge with a main span of 150 m. The results indicate that the cyclic creep of concrete may accelerate the reduction of the deflection reliability indexes, which may fall below the target level before the expected service life of the bridge. In addition, heavy trucks passing in pairs have a significant impact on the deflection reliability. The research findings can be used for the reliable design and optimal maintenance of long-span PSC box-girder bridges.

Analysis on the causes of cracking and excessive deflection of long span box girder bridges based on space frame lattice models

Long-span prestressed concrete box girder bridges (continuous girder and rigid frame bridges) tend to have some apparent diseases. On the one hand, cracks in various directions appear in different positions of different slabs of the box girder; on the other hand, the deflection of the structure develops for a long time, which significantly exceeds the design expectation eventually. This paper intends to use the space frame lattice model, combined with the complete stress index system, to analyze the causes of cracks in different forms in an actual bridge. Unlike the single beam model and the transverse frame model under the guidance of the existing code system, the space frame lattice model that discretizes an entire box girder section into individual slabs can more precisely simulate the load that exceeds the code but exists. In addition, the complete stress index system enriches the design of box girder bridges and can well explain the cracking causes of old bridges. This paper also discusses the effect of the difference in creep and shrinkage caused by the difference in thickness among slabs on the deflection.

Dynamic Response and Impact Force Calculation of PC Box Girder Bridge Subjected to Over-Height Vehicle Collision

The dynamic response of a prestressed concrete box girder bridge under the impact of an over-height vehicle is studied using the numerical simulation method. The finite element analysis software LS-DYNA is used to simulate the collision between the bridge superstructure and an over-height truck. Further, a parametric analysis is carried out to investigate the influence of six factors, i.e., girder configuration, vehicle speed, vehicle mass, impact angle, concrete strength and strand prestress, on both local damage and overall performance of the bridge. The numerical analysis results show that the girder configuration, vehicle speed, vehicle mass and impact angle have obvious effects on both local damage and the overall behavior of the PC box girder bridge. Whereas, the concrete strength and strand prestress only have a certain effect on the local damage at the impact area with very limited influence on the overall behavior of the bridge. In addition, based on the results obtained from the numerical simulation and parametric analysis, a formula for predicting the peak and average impact force of the prestressed concrete box girder bridge under the over-height vehicle impact is developed. The proposed impact force formula comprehensively accounts for the influence of the vehicle speed, vehicle mass and impact angle and can accurately predict the impact force generated under different working conditions, which confirms the promising prospect of the proposed formula in practical applications.

Construction monitoring of a long-span prestressed concrete continuous box girder bridge with variable sections

The structural behaviors in each construction stage were monitored and analyzed against the background of a long-span prestressed concrete continuous box girder bridge with spans of 55+100+55 m. At first, the formwork erection elevation and pre-camber of the bridge in each stage, as well as stress values of key cross-sections were determined by simulating the whole construction process using the finite element software. Then, the design parameters were identified and the model was corrected by field data collection and considering various influencing factors, so as to ensure effectiveness of the model. Finally, the formwork erection elevation was adjusted according to the stress and altitude in each construction stage, followed by closure of the bridge. According to field monitoring and adjustment, the measured alignment and stress of the bridge conform to the design and the error meets the requirements of specification, indicating a favorable monitoring effect. The research can provide reference for construction of similar bridges.

Analysis of The Working Performance of Large Curvature Prestressed Concrete Box Girder Bridges.

Based on numerical shape functions and the structural stressing state theory, the mechanical properties of the curved prestressed concrete box girder (CPCBG) bridge model under different loading cases are presented. First, the generalized strain energy density (GSED) obtained from the measured strain data is used to represent the stressing state pattern of the structure; then, the stressing state of the concrete section is analyzed by plotting the strain and stress fields of the bridge model. The stressing state pattern and strain fields of the CPCBG are shown to reveal its mechanical properties. In addition, the measured concrete strain data are interpolated by the non-sample point interpolation (NPI) method. The strain and stress fields of the bridge model have been plotted to analyze the stressing state of the concrete cross-section. The internal forces in the concrete sections are calculated by using interpolated strains. Finally, the torsional effects are simulated by measuring the displacements to show the torsional behavior of the cross-section. The analysis and comparison of the internal force and strain fields reveal the common and different mechanical properties of the bridge model. The results of the analysis of the curved bridge model provide a reference for the future rational design of bridge projects.

Long-term performance of a continuous box-girder bridge constructed using precast segments with wet ultra-high-performance concrete (UHPC) joints

Although the precast segmental construction (PSC) technique can relieve age-dependent difficulties and accelerate bridge construction as compared to the cast-in-situ construction (CSC) technique for long-span prestressed concrete box-girder bridges (LSPCBB), the ordinary concrete joints between adjacent precast segments are risky. In order to improve the bond strength at the joint interface and enhance structural reliability, ultra-high-performance concrete (UHPC) can be used to fill joints as a new cementitious material with high strength, ductility, and durability. Thus, the effect of the naturally cured UHPC shrinkage and creep on the bridge's long-term performance should be evaluated. The present study numerically investigates the long-term bridge performance constructed by the PSC technique with wet UHPC joints. One cast-in-place segment using the CSC technique is replaced by one precast segment and one cast-in-place UHPC joint using the PSC technique in the bridge model. A creep coefficient equation in an existing code and a shrinkage strain equation fitted from the test data for the UHPC are verified, and an equivalent temperature drop method is used for simulating pretension forces of the prestressing strands in the numerical model. Through comparison with the CSC technique, the technical advantages in reducing long-term deflection, rotation, prestress losses, and improving normal cross-sectional stresses are quantitatively highlighted for the UHPC enhanced PSC bridge.

Analysis of Bonding Performance of Grouting Corrugated Pipes in Fabricated Bridge Structures

Prefabricated bridge structures are highly popularized due to their simple construction, economy, and environmental protection. Relying on the prefabricated prestressed concrete box girder bridge project of Rongwu Expressway Section 6, this research studies the structural mode of grouting bellows and the mechanical properties of joints under different design parameters. The laboratory test was carried out by adjusting the two design parameters of aperture ratio and material properties, and the test data of joint mechanical properties under the influence of different factors were analyzed with the help of grey relational theory. The result goes like this: when the size of the metal bellows is certain, the aperture ratio becomes smaller, the internal space of the specimen becomes smaller, the internal restraint is weakened, and the bonding performance of the reinforcement becomes worse. When D/d = 2.6, the performance of the specimen is better. Comparing the grouting materials with different characteristics, the performance of the metal bellows specimen increases with the enhancement of the properties of the grouting material, but as the aperture ratio becomes smaller, the influence of the grouting material on the performance of the specimen becomes weaker. The comprehensive analysis is carried out with the grey relational theory and the correlation degree of the influence of the two factors on the specimen, and the correlation degrees γ 1 = 0.66 and γ 2 = 0.67 are obtained. Both of them have a strong correlation with the performance of the specimen, and the degree of influence is roughly similar. Based on the engineering application requirements and related design requirements, the construction method of selecting 100 MPa high-strength grouting material which is higher than the general standard, 65 mm corrugated pipe, and 22 mm steel bar is finally put forward. This research relies on engineering theoretical and experimental studies, which provide important theoretical support and technical guarantee for the research on the joint structure of prefabricated structures.

Structural Systems Comparison of Simply Supported PSC Box Girder Bridge Equipped with Elastomeric Rubber Bearing and Lead Rubber Bearing

This study compares the influence of elastomeric rubber bearing (ERB) as the regular bearing support and lead rubber bearing (LRB) as the seismic isolation device on the seismic performance of a seven-span simply supported prestressed concrete (PSC) box girder bridge, which was analyzed using nonlinear time history analysis (NLTHA) with the OpenSees software. The results showed that the maximum pier responses and damage were smaller in models with LRB than with ERB. The bridge model using ERB occurred the slightest damage at levels II, while the one using LRB was at levels I. In addition, the highest seismic performance level in the model with ERB was at the operational limit. Meanwhile, the seismic performance in the model with LRB was at the fully operational limit. Thus, LRB was a good preference for improving the seismic performance and mitigating the damage due to the seismic excitation with a slender pier.

Simplified Method for Lateral Distribution Factor of the Live Load of Prefabricated Concrete Box-Girder Bridges with Transverse Post-tensioning

Transverse post-tensioning arrangement in prefabricated prestressed concrete (PC) box-girder bridge can effectively improve the transverse connection's performance to avoid stress concentration. The number of transverse post-tensioning tendons and the transverse post-tensioning force are crucial factors determining the live load's lateral distribution. Four prefabricated PC box-girder model tests were carried out to calculate the lateral distribution of the live load. Based on experimental results, the recommended values of the reduction factors of contact interfaces considering the effective longitudinal transfer length of transverse post-tensioning were given, and a simplified method of lateral distribution factor was proposed. The proposed simplified method results were compared with the PCI code, experiments, finite element method, articulated plate method, and rigid-plate method. The results showed that the lateral distribution factor calculated by the simplified method agreed with the results of experiments and the finite element method. The average relative differences were less than 8%. In comparison, the relative differences were more than 15% for the PCI code, articulated plate method, and rigid plate method. Thus, the proposed method could meet the engineering application and be adopted to calculate the lateral distribution factor of bridges with transverse post-tensioning.

Finite-Element Analysis of Adjacent Concrete Box Girders Transversely Post-Tensioned at the Top Flanges Only

A three-dimensional non-linear finite-element model (FEM) was constructed using a commercial software (ATENA-Studio) to investigate the transverse load distribution behavior of adjacent precast prestressed concrete box-girder bridges. An innovative connection between box girders was used, where transverse post-tensioning was applied at the top flanges only eliminating the need for intermediate transverse diaphragms. The FEM was validated in terms of deflections, strains, cracking and ultimate loads against experimental results previously reported by the authors. The validated FEM was then used to perform a parametric study investigating the influence of adding concrete topping, load location, and bridge width on the transverse load distribution behavior of the newly developed connection. The results of the FEM demonstrated the efficiency of concrete topping in limiting mid-span deflections up to 25%. Additionally, the maximum live load moment distribution factors (LLMDFs) for different load locations and bridge widths were evaluated.

Vehicle Bump Testing Parameters Influencing Modal Identification of Long-Span Segmental Prestressed Concrete Bridges.

In-service prestressed concrete box girder bridges have received increasing attention in recent years due to a large number of bridges reaching decades in service. Therefore, the ageing of infrastructure demands the development of robust condition assessment methodologies based on affordable technology such as vehicle-induced vibration tests (VITs) in contrast with more expensive existing technologies such as tests using hammers or shakers. Ambient vibration tests (AVTs) have been widely used worldwide, taking advantage of freely available ambient excitation sources. However, the literature has commonly reported insufficient input energy to excite the structure to obtain satisfactory modal identification results, especially in long-span concrete bridges. On the other hand, the use of forced vibration tests (FVTs) requires more economic resources. This paper presents the results of field measurements at optimally selected locations in VITs consisting of a 32-ton truck and a springboard with a height of 50 mm. AVTs using optimal sensor placement (OSP) provide similar results to VITs without considering OSP locations. Additionally, the VIT/AVT cost ratio is reduced to 2 since a shorter data collection time is achieved within a one-day (8 h) test framework, which minimizes temperature effects, thus leading to improvements in AVT identification results, especially in vertical modes.

Additional Shear Stresses in Webs of Segmental Concrete Bridges due to Anchorage of Cantilever Tendons

The balanced cantilever method is the most widely used technique for the construction of large-span segmental prestressed concrete box-girder bridges. In order to control shear cracks at the service limit state, the principal tensile stresses in the webs are analyzed for all segmental bridges. Web shear cracking may occur for a number of reasons, one of them is the ignoring of shear stresses induced by the anchorage of cantilever tendons during the cantilevering process. This study aims to provide a clear understanding of anchorage-induced shear stresses in the webs of segmental box-girder bridges, including the underlying mechanisms, mechanical models, adverse effects, and design considerations. Case studies show that the peak shear stresses in the webs might have a significant increase due to this localized effect, while it cannot be captured by the beam-element analysis and is usually not considered in the routine design. To solve this problem, a practical approach is developed for evaluating the anchorage-induced shear stresses in the webs of segmental concrete box-girder bridges.

Probability analysis of web cracking of corroded prestressed concrete box-girder bridges considering aleatory and epistemic uncertainties

Reasonable assessment of web cracking probability is essential to ensure the service performance of corroded prestressed concrete (PC) bridges. In this paper, a time-dependent prediction model of effective prestress for different prestress tensioning techniques and a corrosion propagation model are established. Meanwhile, an assessment approach of web cracking probability considering both aleatory and epistemic uncertainties is proposed. The case analysis results show that the doubled-tensioned prestress technique is obviously more effective in decreasing the web cracking probability than the traditional prestress tensioning technique. The existing probabilistic method that only considers the aleatory uncertainty may greatly underestimate the probability of web cracking. In comparison, the fastest time to reach the threshold value of web cracking probability when considering the epistemic uncertainty is over 11% earlier than that of using the existing methods. Additionally, the epistemic uncertainty of the chloride diffusion coefficient among the selected corrosion parameters has a most significant impact on the probability of web cracking. Therefore, the epistemic uncertainty of corrosion parameters, especially for the chloride diffusion coefficient, should be minimized as much as possible in this assessment process.

Analysis of continuous PC box girder bridges with CSWs by using equivalent computational model

The widespread usage of prestressed concrete (PC) box girder with corrugated steel webs (CSWs) can be attributed to its many remarkable merits over traditional concrete box girders, such as significantly reducing the deadweight of the girder, speeding up the construction process, avoiding the problem of web cracking and increasing the prestress introduction efficiency. Numerous previous studies were conducted to investigated the mechanical properties of CSWs as well as simply supported box girder bridges with CSWs, whereas very few studies focused on the FE modeling methods of continuous PC box girders with CSWs. In addition, experimental work on scale bridge models or full-scale bridges adopting the box girder with CSWs is very limited. In this paper, an equivalent orthotropic web (EOW) model was developed for CSWs and used to analyze the performance of the continuous PC box girder bridges with CSWs. To verify this model, a one-tenth-scale bridge model was developed for an existing continuous PC box girder bridge with CSWs. Both static and dynamic tests were carried out on this scale bridge model. The results obtained from the bridge finite element (FE) model with EOWs were compared to the results obtained from the bridge FE model with CSWs and also the experimental results from the scale bridge model. Good agreement was achieved between these results, indicating that the EOW model can provide a trustworthy and convenient tool in the FE analysis of PC continuous box girder bridges with CSWs.

Deflection-based multilevel structural condition assessment of long-span prestressed concrete girder bridges using a connected pipe system

Several long-span prestressed concrete (PSC) girder bridges have exhibited excessive deflection over time that can affect their normal use and safety. Thus, monitoring the time-dependent deflections of PSC girder bridges is required to ensure a timely warning of deficient bridge conditions. This study measured the deflections of a PSC box-girder bridge using a connected pipe system to provide health monitoring and condition assessment. A deflection-based, multilevel assessment approach was proposed wherein the individual deflection components (traffic-induced, temperature-induced, and long term) were used to evaluate the bridge state. The assessments of each component were fused using the Dempster–Shafer evidence theory to achieve an integrated outcome. Results show that a connected pipe system can accurately monitor the real-time deflection of long-span girder bridges. The proposed multilevel assessment approach makes full use of the structural condition information from the acquired deflection data, demonstrating the effectiveness and practicality of the fusion algorithm.

Computation of Deflections for PC Box Girder Bridges with Corrugated Steel Webs considering the Effects of Shear Lag and Shear Deformation

Prestressed concrete (PC) girders with corrugated steel webs (CSWs) have received considerable attention in the past two decades due to their light self-weight and high prestressing efficiency. Most previous studies were focused on the static behavior of CSWs and simple beams with CSWs. The calculation of deflection is an important part in the static analysis of structures. However, very few studies have been conducted to investigate the deflection of full PC girders or bridges with CSWs and no simple formulas are available for estimating their deflection under static loads. In addition, experimental work on full-scale bridges or scale bridge models with CSWs is very limited. In this paper, a formula for calculating the deflection of PC box girders with CSWs is derived. The longitudinal displacement function of PC box girders with CSWs, which can consider the shear lag effect and shear deformation of CSWs, is first derived. Based on the longitudinal displacement function, the formula for predicting the deflection of PC box girders with CSWs is derived using the variational principle method. The accuracy of the derived formula is verified against experimental results from a scaled bridge model and the finite element analysis results. Parametric studies are also performed, and the influences of shear lag and shear deformation on the deflection of the box girder with CSWs are investigated by considering different width-to-span ratios and different girder heights. The present study provides an effective and efficient tool for determining the deflection of PC box girders with CSWs.