Steel Girder Research Articles

Simulation of concrete structures deformation affected by alkali–silica reaction considering environmental conditions and multiaxial stress state

In this study, the expansion and deformation of alkali–silica reaction (ASR)-affected concrete structures under natural environment and multiaxial stress state are predicted. The performance of the ASR model proposed in previous research is quantitatively investigated in terms of relative humidity, multiaxial stress, and temperature dependencies based on experimental results. The simulation results indicate that the relative humidity-dependent expansion caused by the ASR can be simulated effectively by slightly modifying the relative humidity threshold in the model. In a simulation focusing on stress dependency, the insufficient consideration of the relationship between compressive stress and ASR gel absorption into pores in the model by previous research resulted in discrepancies between the simulation and experimental results. The performance of the model by previous research in simulating temperature dependency is improved by referring to the relationship between the expansion rate and temperature recorded from specimens exposed to the real environment. An exposure experiment of reinforced concrete (RC) slab on steel girders is simulated using the modified model. The results show that the modified model can reproduce the tendency of three-dimensional deformation of RC slab, while model improvement considering time-dependent and stress-dependent phenomena should be needed for long-term quantitative predictions.

Reliability evaluation of twin steel box girder bridges using a simplified method

The objective of this study is to comprehend the performance of twin steel box girder (TSBG) bridges after complete fracture of one girder and to establish an outline of an approach for reliability analysis required for assessing their levels of structural redundancy. The earlier work has concluded that the main mode of failure for the bridge in such case is a failure in the deck. This conclusion obtained through a series of experimental and numerical studies significantly reduces the efforts for assessing the safety of TSBG bridges. For the purpose of developing an approach for reliability analysis, a simply-supported single-span bridge tested at the University of Texas (UT) at Austin was selected as a baseline model. The results of the current study through an extensive finite element analysis confirmed the earlier findings that concrete deck failure is the dominant failure mode of the bridge after the occurrence of a fracture in one of the girders. Building on the work at UT, an improved simple and unified yield line analysis method was developed to determine the bridge deck capacity. For the first time, a comprehensive and coherent reliability approach was used to assess the safety of TSBG bridges after the complete fracture of one steel girder. Though the developed safety assessment approach was applied to one example bridge, nevertheless, the method described in this paper could easily be extended to evaluate other TSBG bridges. Although the results of this study cannot readily be generalized for all TSBG bridges without further evaluation, this study shows that simply supported twin steel box girder bridges could indeed be safe and potentially removed from the fracture critical list.

Moment and shear estimations in steel girder highway bridges using committees of artificial neural networks and finite element models

Moment and shear estimations in steel girder highway bridges using committees of artificial neural networks and finite element models

Effect of shear span-to-depth ratio on behavior of sandwich core steel girder with corrugated web

Girders with corrugated steel web are preferred and widely used in recently constructed bridges and industrial buildings. Sandwich core girders with corrugated web are constructed by adding two plates (skins) to the corrugated web. This study aims to investigate the shear span-to-depth ratio impact on the performance of sandwich core steel girders with corrugated web. Three span-to-depth ratios (a/d): 1.0, 1.833 and 2.5, were examined. The test includes three girders with sandwich web thickness of 30 mm, three girders with 60 mm sandwich web thickness, and three girders with conventional flat webs. A total of nine simply supported steel girders subjected to a concentrated load were fabricated and tested up to failure. The responses of the examined girders are presented in term of the load deflection curves, the ultimate load, and the maximum displacement. Among the conclusions drawn in this study that girders with sandwich core thickness of 30 mm demonstrate higher ultimate load capacity than girders with sandwich core of 60 mm, the maximum difference in the ultimate load capacity was about 20% and can be seen at a/d equals to 1.0. The results also pointed out that the behavior of the beams was noticeably impacted by the shear span-to-depth ratio.

Structural Performance and Engineering Application of a Long Lasting Weathering Steel Composite Bridge with Tubular Flanges

A study of the structural performance and engineering application of a long lasting composite bridge with tubular steel flanges was carried out. The flexural, shear and torsional resistance of high-performance composite girders with tubular flanges were analysed comparatively based on tests and finite element simulation. Based on the research and design rules achieved above, the first two typical composite girder bridges with rectangular tubular flanges using high-performance weathering steel have been constructed in China. The structural performances were compared of a composite girder bridge with tubular flanges and a composite girder bridge adopting traditional I-shaped steel girders. A long-term performance evaluation was conducted for a weathering steel composite bridge with tubular flanges, which included an in situ inspection and rating assessment of the patina and life cycle cost evaluation of the whole bridge. Learned from the application experience and evaluation results, weathering steel composite girder bridges with tubular flanges revealed superior long lasting structural performance including improved torsional stiffness and resistance, fewer web stiffeners and cross beams, fast construction, and easy and less maintenance during the in-service stage.

Experimental investigation on flexural behavior of a precast slab joint with perfobond strips and steel fiber-reinforced mortars

This study aims to present a joining method for precast concrete slabs in the replacement work of the degraded concrete slab in existing steel girder bridges. The joint uses perfobond strips along with steel fiber-reinforced mortars, which is expected to be smaller and to offer a short construction time compared with traditional loop joints. Firstly, an optimized mixture of the steel fiber-reinforced mortar with both early strength development and high tensile strength is developed based on material tests. Then, eight joint specimens are fabricated and tested under flexural loads, considering the effects of various parameters associated with the layout, the perforation diameter of perfobond strips, and the curing age of joint materials. Detail discussions on load–deflection relationships, crack patterns, strain behaviors of joint components, and joint resisting mechanisms are presented. It is observed that the flexural behavior of the joint is correlated with the shear behavior of the perfobond strips, which is both significantly affected by the examined parameters. Finally, a simplified estimating method for the joint flexural capacity is then proposed according to the shear capacity of perfobond strips. The results obtained by the proposed method show a good agreement with ones from the experimental results.

Tension forces in stud connectors between concrete slabs and steel girders under transverse bending moments

In steel–concrete composite bridges, stud connections between steel girders and concrete slabs can be subjected to transverse bending moments, where noticeable tension forces may arise in stud connectors near transverse stiffeners of steel webs. Wider cantilevers further enhance these effects. This paper seeks to propose a practical calculation method of tension forces in stud connectors under transverse bending moments and clarify the influential factors on tension forces. Firstly, the equilibrium equation of moments is established for the stud connection considering the contributions of tension forces (T), contact forces ©, and prying forces (p). Thereafter, the relations between T and p are built through a cantilever beam model, and the position of c is determined by extensive finite-element (FE) analysis. Subsequently, an engineer-friendly calculation procedure is introduced and validated against FE results, and the effects of various parameters are discussed through a parametric analysis. Results indicate that the proposed method reveals satisfactory accuracy and produces safe predictions in most cases. It also successfully captures the influences of geometric parameters of the stud connection and the stud’s tensile stiffness. By reducing the longitudinal and transverse spacings between studs, and increasing the thickness of top flange, the maximum tension force (T11) can be significantly decreased by up to 33%, 36%, and 46%, respectively. Reductions in stud’s tensile stiffness can also lower T11, while the effects are relatively minor with the largest drop of 10%. Decreases in the distance from the stud to the stiffener can enlarge T11 by 63% at most.

Parametric investigations on shear behavior of perforated transverse angle connectors in steel–concrete composite bridges

The perforated transverse angle connectors (PTACs), that posses excellent shear capacity and good ductility, have been proposed to address the casting obstruction of the bottom concrete decks in prestressed composite (PC) box-girder with corrugated steel webs (CSPWs). The structural performance of steel–concrete composite bridges largely depends on the behavior of the mechanical shear connectors. In this study, numerical analyses on the shear behavior of the PTAC were performed. The finite element (FE) model was developed using ABAQUS and validated by comparing its predictions with test data available in the literature. The comparisons indicated that the numerical model could reflect the experimental results closely. Parametric studies were then carried out to determine the influential factors on the PTAC shear capacity. It was found that the shear strength of the PTAC increased linearly with the increase of the concrete strength. The flange and web thickness had great effect on the PTAC shear capacity, while the flange and web height slightly influenced. The group PTAC arrangement had a significant influence on the shear strength and this effect can be ignored when the spacing was more than 400 mm. In addition, the perforating rebar contributed little to the shear capacity but obviously enhanced the ductility. The FE analysis results were used to verify the applicability of the current design provisions for the PTAC shear strength. It was noted that the formulas in these provisions conservatively predict the shear strength due to the effect of the flange welded on the steel girder was ignored. An empirical formula was developed to evaluate the shear strength of angle shear connectors. The mean of the ratio of the predicted results to test ones ranged from 0.981 to 1.018, which denoted the proposed design formula could accurately be used to predict the PTAC shear capacity.

Behavior of steel girder bridges damaged by vehicular collision

Vehicles often collide with girders of low-clearance bridges, yet there is a knowledge gap in understanding the behavior of damaged steel girders. This paper addresses this gap by performing non-destructive field testing on four damaged steel girder bridges. The focus is on two- and three-span continuous multi-girder steel bridges for which an exterior girder has sustained Category T damage, i.e., torsion about the longitudinal direction. The behavior of damaged girders, symmetric undamaged girders, and adjacent girders under quasi-static truck loading is monitored using digital image correlation (DIC). Specifically, the measured strains of damaged girders are compared to the strains of corresponding symmetric undamaged girders to investigate the effect of the damage on behavior for each bridge. Strain gauges were used to monitor the behavior of one bridge under quasi-static truck loading, as well as speed and crawl tests. The strain gauge readings are also used to validate DIC strain measurements for field monitoring of bridges. The measured strains are used to validate finite element (FE) numerical models. A parametric study investigates the effect of varying shapes and locations of damage on the load-deflection behavior of a single girder as well as two- and three-span continuous bridges. Overall, this study found that measured strains in all girders are less than 200 microstrain or approximately 40.0 MPa (5.80 ksi). Results indicate that vehicular damage may affect composite behavior, bridge railings participate in carrying live load, damaged girders may have increased live load amplification factors, and damage at the center of a span with a large rotation angle of the web results in the greatest loss of stiffness.

Optimum Design of Fully Composite, Unstiffened, Built-Up, Hybrid Steel Girder Using GRG, NLR, and ANN Techniques

Composite steel beams are commonly used element in multistorey steel buildings to enhance floor economy and serviceability and provide more clear height. Due to the low level of stress in the webs of such beams, hybrid sections are used where the flanges have higher strength than the webs. A lot of earlier research was carried out to optimize the design of the hybrid and nonhybrid composite steel beams under both static loading and dynamic behavior. However, there is still a need to develop a more practical optimization method. The aim of this research is to develop simple and practical equations to determine the optimum cross section dimensions for both shored and unshored, simply supported, hybrid and nonhybrid, composite steel beam under static loads. To achieve that goal, a research program of two phases was carried out. The first phase was generating a database of 504 composite beams with different steel grades for flanges and webs, subjected to different values of bending moment. The cross section of each beam in the database was optimized using GRG technique to minimize the cost considering the unit price of each steel grade. In the second phase, the generated database was divided into training and validation subsets and used to develop two predictive models using Nonlinear Regression (NLR) technique and Artificial Neural Network (ANN) technique to predict the optimum cross section dimensions and hence the optimum weight and cost. The accuracies of the developed models were measured in terms of average error percent. NLR and ANN models showed average error percent of 16% and 11%, respectively.

Finite Element Modeling on Shear Performance of Grouted Stud Connectors for Steel–Timber Composite Beams

Steel–timber composite (STC) systems are considered as an environmentally friendly alternative to steel–concrete composite (SCC) structures due to its advantages including high strength-to-weight ratio, lower carbon footprint, and fully dry construction. Bolts and screws are the most commonly used connectors in STC system; however, they probably make great demands on the accuracy of construction because of the predrilling in both the timber slabs and steel girder fangles. To address this issue, the STC connections with grouted stud connectors (GSC) were proposed in this paper. In addition, stud connectors can also provide outstanding stiffness and load-bearing capacity. The mechanical characteristic of the GSC connections was exploratorily investigated by finite element (FE) modeling. The designed parameters for the FE models include stud diameter, stud strength, angle of outer layer of cross-laminated timber (CLT) panel, tapered groove configurations, and thickness of CLT panel. The numerical results indicated that the shear capacity and stiffness of the GSC connections were mainly influenced by stud diameter, stud strength, angle of outer layer of CLT panel, and the angle of the tapered grooves. Moreover, the FE simulated shear capacity of the GSC connections were compared with the results predicted by the available calculation formulas in design codes and literatures. Finally, the group effect of the GSC connections with multiple rows of studs was discussed based on the numerical results and parametric analyses. An effective row number of studs was proposed to characterize the group effect of the GSC connections.

Comparative Study of Seismic Design for Different Bridges Structures

The main objective of this study is to compare the structural members capacity between different types of bridges structures under seismic load. The results of seismic modal analysis showed that the models of box girder bridge, precast T girder bridge, and U steel girder bridge had the higher values of natural frequency comparing with others bridges structures under seismic load. Pushover analysis in transvers direction showed that bent No. 2 of bridges structures which was located in the middle of bridges superstructure was displaced in transvers direction more than bent No. 1 and bent No. 3. In longitudinal direction, Precast I girder bridge had higher value of longitudinal displacement comparing with others bridges structures, and it was more than the maximum value of transvers displacement. The results of demand and capacity ratio showed that bent No. 2 was the critical structural member which had values of demand/capacity ratio more than 1.0 or near from it especially precast I girder bridge, precast T girder bridge, and U steel bridge, indicating that these types of bridges will be subjected to failure in bent No. 2. Therefore, there was needing to redesign the bents of these types of bridges by increasing the numbers of piers, using high strength materials in construction of bents, and increasing of dimensions of piers and pier caps. The results of internal forces showed that bent No. 2 was subjected to the maximum values of axial force, horizontal shear, and bending moment for all types of bridges structures. Also, it can be seen that the models of precast I girder bridge, precast T girder bridge, and U steel bridge had the higher values of forces comparing to others models, indicating that these results agree with results of demand/capacity ratio and pushover analysis method.

Demountable Bolted Shear Connector for Easy Deconstruction and Reconstruction of Concrete Slabs in Steel–Concrete Bridges

Welded headed studs are used to connect steel girders and concrete slabs in steel composite bridges. However, environmental problems related to welded shear connectors have been reported, including noise and dust generation during the replacement and demolition of damaged or worn concrete slabs. To overcome these issues, demountable shear connectors that enable easy replacement of damaged or worn concrete slabs must be developed. However, conventional bolted shear connectors mainly use embedded nuts, which cannot be used in structures such as bridges because initial slip occurs and the stiffness and shear resistance strength are relatively low. To address these issues, this paper proposes a bolted shear connector that integrates the embedded nut part into the stud bolt and has a tapered shape at the bottom of the expansion column. For performance verification in regard to static shear strength and slip displacement, push-out tests were performed according to Eurocode-4, and the performance of the proposed stud bolt was compared to those of conventional welded headed studs and embedded nut-style bolted shear connectors. In addition, an analytical review was performed using the ABAQUS program for the 1/4 axisymmetric model of the push-out test. As a result of applying the material nonlinear model and the surface contact analysis, the load-slip displacement of each analysis model showed a tendency extremely similar to the experimental results. The proposed demountable bolted shear connector exhibited excellent shear performance and can be used as a satisfactory replacement for conventional welded studs because it meets slip displacement and ductility standards.

Field-Deployable Fiber Optic Sensor System for Structural Health Monitoring of Steel Girder Highway Bridges

Structural health monitoring of highway bridges is a vital but currently challenging aspect of infrastructure engineering due to the number of sensors required, power requirements, and harsh environmental conditions. The purpose of this study is to develop a structural health monitoring system using fiber optic sensors based on fiber Bragg gratings that addresses these issues and is field deployable. Prototype systems were installed on two steel girder bridges. The first bridge used sensors adhered to the web and flange. The second bridge used a flange-only array of mechanically mounted sensors. The results demonstrated the accuracy of the fiber Bragg grating sensors and indicated that fewer multiplexed fiber optic cables and loosely routed cables were needed to maintain signal integrity. Adhered sensors were prone to lose their bond due to the curing conditions in the field. The findings suggest that the proposed system may be best used in a hybrid deployment, where a diagnostic field test with conventional sensors is used to determine the baseline bridge response and fiber optic sensors are periodically installed for short-term monitoring.

Discrete optimisation of steel-concrete composite sections in simple girder bridges

In this study, the optimisation design problem of steel-concrete composite sections in simple girder bridges is developed. Design variables including the thickness of the desk and the dimensions of the girder section are discrete variables to reflect the realistic design works. The total cost of the desk and the steel girder is the objective function that is minimised. The design requirements of the geometry, load-carrying capacity, and deformation provided in the TCVN 11823:2017 standard are used as the optimisation constraints. The above discrete optimisation is solved by using the Harmony Search (HS) algorithm. A 42(m) simple girder is studied. The numerical results show that the optimal designs save about 15% compared to using the conventional design method. It can be concluded that applying the optimisation in the design of steel-concrete composite beams brings high efficiency and it is easily applied in practice.

Mixed-mode fatigue crack growth analysis of I-shaped steel girders with trapezoidal corrugated-webs

In bridge industry, the composite box-girder with corrugated steel webs and concrete flanges is quite a common practice over recent years. However, this innovation encounters fatigue-sensitive details not fully investigated, especially in the research area of mixed-mode fatigue crack growth. This study addresses the mixed-mode fatigue crack growth analysis of an I-shaped corrugated web girder associated with the represented web-to-flange detail. A linear elastic fracture mechanics (LEFM) based numerical framework was established to simulate the mixed-mode crack propagation. For comparison, a semi-analytical weight function framework was also introduced to predict the pure Mode-I crack propagation life of the same detail. Experimental results of a full-scale inclined corrugated web girder were employed to evaluate these two proposed frameworks. A parametric study was presented based on the proposed frameworks to investigate the effect of initial crack depth and crack shape on fatigue crack propagation life. By comparing the simulation results with test results, the applicability of the proposed LEFM-based numerical framework to the simulation of mixed-mode fatigue crack propagation behaviour in corrugated web girders was discussed.

Effects of vertical ground acceleration on the seismic moment demand of bridge superstructure connections

Vertical ground accelerations are not always considered in bridge design practice, which is partially due to the lack of consistent recommendations in the design codes and standards. However, undeniably, the vertical ground acceleration component in an earthquake can be large. While the effects of vertical ground acceleration on bridges have been studied in the past, the focus has mostly been on performance of the substructure, especially columns. This study thus investigates the effects of large magnitude of vertical ground accelerations on the response of bridge superstructures as it can experience significant impact, particularly in the connections and bearing forces. To quantify the effects of vertical ground accelerations and compare the outcomes with existing design recommendations, an analytical study is undertaken on the seismic response of straight, skewed, and curved steel bridge superstructures with drop pier caps. The results show that the vertical accelerations can amplify the superstructure moment demands at the midspan and support locations by as much as above 100%. It is further shown that the current design practice to account for vertical ground acceleration effect is not sufficient for earthquakes with high vertical ground accelerations. Although the superstructure used in this study incorporated steel girders, the results are also applicable to bridges with concrete superstructure.

Ultimate Bending Strength Evaluation of MVFT Composite Girder by using Finite Element Method and Machine Learning Regressors

This paper has evaluated the bending performance of a novel prefabricated MVFT steel-concrete composite girder. 9 meters pilot MVFT girder was analyzed by validated finite element model. In the pilot test, the height of web, the length of grouted concrete in the girder and net spacing between webs were parametrically modeled to discuss their effect to the bending strength. An ultimate bending strength formula has been obtained, which was based on the regression of parametric results. In the meantime, the two Machine Learning (ML) models, BP neural network and Least Squares Support Vector Machine, have been also implemented to train and then predict the ultimate strength of MVFT girder. Three factors were selected as input in ML models: the distance between steel girder’s Tensile Centroid(TC) and slab’s Compressive Centroid(CC), the distance between steel girder’s TC and its CC, the compressive area of steel girder. After the completion of the ML training, the ultimate strength predictions of 30 meters MVFT girder by BP model and the formula have been compared, which agrees well with each other and validates their accuracy.

Spatial Numerical Simulation of Locally Corroded Steel Plate Girder with Various End Panels

Field inspections indicate that corrosion damages steel bridge girders more at the ends as compared to the central region. Any significant loss of metal around the bearing region of the girder may cause an abrupt change of failure behavior and strength loss. The present numerical study is focused to evaluate the response of local corrosion damage at steel plate girder, with different end panels, that is, no end post, nonrigid, and rigid end post. Local corrosion damage was considered by reducing the bearings stiffener and adjacent web uniformly for a maximum damage depth of 100 mm with various corrosion damage levels (i.e., 75%, 50%, and 25%). The numerical analysis was performed on a computer package ABAQUS, using modified Riks analysis. A 4‐node shell element (S4R) with reduced integration was used to simulate the model. The study concludes that local corrosion damage is more critical in nonrigid end post than in rigid end post. Furthermore, the steel girder with no end post is more susceptible to crippling failure due to local corrosion damage as compared to the other types of end post.

Precise dynamic disintegration of concrete structures by controlling wave motion

By applying more safely usable electric discharge impulses and based on the theory of wave and fracture dynamics, we try to establish more effectively controllable techniques for precise partial disintegration of concrete structures. The models experimentally examined in the field and numerically studied in the laboratory include (un)reinforced concrete blocks, realistically large concrete slabs and steel-concrete composite structures. In order to guide three-dimensional wave interaction and ensuing dynamic fracture development in the models exactly as desired, we make use of free surfaces and pre-existing planes of weakness such as interfaces between concrete, reinforcing steel bars, steel girders and headed stud shear connectors. We also introduce, in addition to blast holes containing energy sources and emitting waves, empty dummy holes and slits in the models, and find that the development of fracture network and the final structural disintegration pattern depend sensitively on the geometrical settings of the above inhomogeneities. Our ultimate goal is to crush and remove only concrete material while other parts of structures like headed stud shear connectors and steel girders remain undeformed for later renovation work, even in densely populated urban areas.