Response Of Girder Research Articles

Numerical and experimental investigation into the mid- and high-frequency vibration behavior of a concrete box girder bridge induced by high-speed trains

Concrete box girder bridges exhibit mid- and high-frequency (> 20 Hz) dynamic responses due to train excitations, which result in problems of noise radiation and track deterioration. This study presents a numerical model for box girder vibration prediction. Significant attention is focused on the mid- and high-frequency responses via introduction of a detailed track/bridge subsystem model. A hammer impact test was used to determine the model parameters. The model was then validated using a homologation test. The results show that the wheel/rail force and box girder mobility are the two principal factors that influence box girder vibration spectral characteristics and amplitudes. The box girder responses at cross-sections with similar dynamic characteristics vary little, as they increase moderately with the train speed. The application of a fastening system with low stiffness and high damping can effectively reduce box girder vibration. However, the elastic modulus and damping of the cement–asphalt mortar, and the thickness of the track slab and bearing base exert the smallest influences on the vibrations. The box girder slab thickness should be designed appropriately because its dynamic behavior is closely associated with the slab characteristics.

Dynamic Response of Steel Box Girder under Internal Blast Loading

This paper aims at investigating the dynamic response of the steel box girder under internal blast loads through experiments and numerical study. Two blast experiments of steel box models under internal explosion were conducted, and then, the numerical methods are introduced and validated. The dynamic response process and propagation of the internal shock wave of a steel box girder under internal blast loading were investigated. The results show that the propagation of the internal shock wave is very complicated. A multi‐impact effect is observed since the shock waves are restricted by the box. In addition, the failure modes and the influence of blast position as well as explosive mass were discussed. The holistic failure mode is observed as local failure, and there are two failure modes for the steel box girder′s components, large plastic deformation and rupture. The damage features are closely related to the explosive position, and the enhanced shock wave in the corner of the girder will cause severe damage. With the increasing TNT mass, the crack diameter and the deformation degree are all increased. The longitudinal stiffeners restrict the damage to develop in the transverse direction while increase the crack diameter along the stiffener direction.

Inelastic moment-rotation response of 690 MPa grade steel I-section girders

Recent specifications have adopted moment-rotation relationships for I-section girders with yield strengths up to 485 MPa to realize adequate and reliable ductility and the development of strength significantly greater than the yield moment. In this study, experiments were performed in order to verify the inelastic moment strength and examine an equation that appropriately expresses the inelastic moment-rotation response of high-strength steel I-section girders in the negative moment region. Three test girder specimens were fabricated and tested to their ultimate bending strengths up to failure. The test results were compared with the maximum strengths predicted for I-girders by finite element analysis and the nominal moment-plastic rotation curve in the specifications. A sufficiently redundant shakedown behavior was revealed by the comparison, which experimentally confirmed the adequacy of the current design equation for the moment-plastic rotation curve to 690 MPa grade steel I-girders. Based on the experimental results, conclusions were drawn regarding the inelastic moment-rotation behavior.

Wind-induced Buffeting and Vibration Reduction Control Design of Qingshan Extra Large Span Cable-Stayed Bridge

In order to reduce the maximum cantilever construction state and completed bridge state buffeting effect of Qingshan extra large span cable-stayed bridge, the vibration reduction control design of the bridge is carried out. Through the numerical calculation and wind tunnel test, the wind-induced response of the bridge is obtained, under the maximum cantilever construction state and completed bridge state. The vibration reduction control design of the two states is conducted. And the bridge comfort index is determined. The results show that the buffeting response of the main girder is larger under the maximum cantilever construction and the completed bridge state. MTMD is used to design the vibration reduction control of the bridge, and the MTMD reducing effect is obvious. After the vibration reduction control design, the bridge can meet the construction and bridge safety requirements.

Thermo-mechanical behavior of prestressed concrete box girder at hydration age

Excessively elevated temperature can lead to cracks in prestressed concrete (PC) continuous bridge with box girder on the pier top at cement hydration age. This paper presents a case study for evaluating the behavior of PC box girder during the early hydration age using a two-stage computational model, in the form of computer program ANSYS, namely, 3-D temperature evaluation and determination of mechanical response in PC box girders. A numerical model considering time-dependent wind speed and ambient temperature in ANSYS for tracing the thermal and mechanical response of box girder is developed. The predicted results were compared to show good agreement with the measured data from the PC box girder of the Zhaoshi Bridge in China. Then, based on the validated numerical model three parameters were incorporated to analyze the evolution of the temperature and stress within box girder caused by cement hydration heat. The results of case study indicate that the wind speed can change the degradation history of temperature and stress and reduce peak value of them. The initial casting temperature of concrete is the most significant parameter which controls cracking of PC box girder on pier top at cement hydration age. Increasing the curing temperature is detrimental to prevent cracking.

Experimental Investigation on Flexural Response of Hybrid Steel Plate Girder

Flexural tests were conducted on five full scale I-shaped steel beams, three hybrid and two homogeneous, with two aims: 1) validate the inelastic flexural behavior of hybrid girder that is manufactured using lower grade steel 2) simplify finite element (FE) analysis procedure, for further parametric studies, by neglecting residual stresses when symmetrical welding sequence is adopted. Effect of material properties and member slenderness on flexural strength, ductility, and failure mode shapes is discussed. It is also found that failure mode shape and expansion of plastic field are mainly influenced by slenderness of member. Load-deflection and moment rotation response in tests are closely matching with non-linear finite element study. Close match is also observed in failure mode shapes and plastic field expansion. Considerable reduction is observed in residual stresses in symmetrically welded sections as compared to sections welded without proper sequence. This validates non-linear FE analysis procedure by neglecting residual stresses. Test results are compared with prediction equations for flexural strength, rotation capacity available in literature. Test results are also compared with provisions in EN 1993-1-1 and IS 800. Moment gradient (3-P) and uniform moment (4-P) loading have been considered to ensure that results are equally applicable in both cases.

Enhancing Fire Resistance of Steel Bridge Girders Using External Fire Insulation

Fire in steel bridges can be a significant hazard; however, no provisions are specified for fire resistance of bridge structural members in current codes and standards. This paper presents results from numerical analysis on the response of steel bridge girders under fire conditions. A finite element model is developed to evaluate the fire resistance of typical steel girders in bridges using fire insulation with different configurations and thicknesses. The first configuration comprised of applying fire insulation on the web plate of the steel girder, while in the second configuration, the steel section is insulated. Results from numerical analysis indicate that fire resistance and failure mode in steel bridge girders is highly influenced by the insulation configuration and thickness. Applying 25.4mm fire insulation on web plate of steel bridge can increase the fire resistance up to 53 minutes, while applying same insulation thickness on steel section can result in 110 minutes fire resistance.

Effect of local instability on fire response of steel beams

Purpose This purpose of this paper is to quantify the effect of local instability arising from high shear loading on response of steel girders subjected to fire conditions. Design/methodology/approach A three-dimensional nonlinear finite element model able to evaluate behavior of fire-exposed steel girders is developed. This model, is capable of predicting fire response of steel girders taking into consideration flexural, shear and deflection limit states. Findings Results obtained from numerical studies show that shear capacity can degrade at a higher pace than flexural capacity under certain loading scenarios, and hence, failure can result from shear effects prior to attaining failure in flexural mode. Originality/value The developed model is unique and provides valuable insight (and information) to the fire response of typical hot-rolled steel girder subjected to high shear loading.

Response of fire exposed composite girders under dominant flexural and shear loading

PurposeThis paper aims to present results from numerical studies on the response of fire exposed composite girders subjected to dominant flexural and shear loading. A finite element-based numerical model was developed to trace the thermal and structural response of composite girders subjected to simultaneous structural loading and fire exposure. This model accounts for various critical parameters including material and geometrical nonlinearities, property degradation at elevated temperatures, shear effects, composite interaction between concrete slab and steel girder, as well as temperature-induced local buckling. To generate test data for validation of the model, three composite girders, each comprising of hot-rolled (standard) steel girder underneath a concrete slab, were tested under simultaneous fire and gravity loading.Design/methodology/approachThe validated model was then applied to investigate the effect of initial geometric imperfections, load level, thickness of slab and stiffness of shear stud on fire response of composite girders.FindingsResults from experimental and numerical analysis indicate that the composite girder subjected to flexural loading experience failure through flexural yielding mode, while the girders under shear loading fail through in shear web buckling mode. Further, results from parametric studies clearly infer that shear limit state can govern the response of fire exposed composite girders under certain loading configuration and fire scenario.Originality/valueThis paper presents results from numerical studies on the response of fire exposed composite girders subjected to dominant flexural and shear loading.

Influence of Nonsymmetric Steel Sandwich Panel Joints on Response and Fatigue Strength of Passenger Ship Deck Structures

Present paper investigates the factors contributing to the stress response of steel sandwich panel deck joints when applied into the hull girder of modern passenger vessel. The emphasis is put on the fatigue analysis, which is the critical design criterion in application of these structures to ships. Two types of joints are considered, i.e., a symmetrical and a nonsymmetrical prismatic joint with respect to the geometrical midplane of the sandwich panel. Stiffness properties are derived for the joints in order to enable the modeling of sandwich structures as part of the hull girder finite element model. The influence of sandwich joints to hull girder response is studied. Notch stress analysis is used for the fatigue strength estimation. The applicability of notch stress method for steel sandwich panels is validated with experiments. The investigation shows that the fatigue strength of steel sandwich panels does not depend only on local stress concentration factors at details, but also on the global stiffness of the structural hull girder system, the sandwich panels, and thus the joint response must be taken into account.

COMPREHENSIVE STUDY ON UNDERSLUNG GIRDER BRIDGE UNDER DIFFERENT LOADING CONDITIONS

The comprehensive study on the structural behaviour of underslung girder bridge is examined in this study through both numerical modelling and experimental 3D model tests. The structural design of steel bridges in many cases is governed by their ability to withstand asymmetric loading conditions. Three different symmetric and asymmetric load cases were investigated to capture the deformational and flexural response of the main girder. It was found that under distributed load the structural response of underslung girder bridge was similar to beam-column with intermediate elastic supports. The numerical model was validated against experimental data with good agreement perceived, allowing an extensive parametric study to be performed. The observed influence of initial geometric imperfections and nonlinearities are discussed. It was found that symmetric load governs the ultimate limit state. However, the asymmetric one takes over in the case of serviceability. Finally, the study presented herein summarises experimental investigations, numerical simulations and design proposals obtained through the recent few years research program, carried on to deepen the knowledge on the structural behaviour of underslung girder bridges.

Evaluating fire resistance of prestressed concrete bridge girders

This paper presents an approach for evaluating performance of prestressed concrete (PC) bridge girders exposed to fire. A finite element based numerical model for tracing the response of fire exposed T girders is developed in ANSYS. The analysis is carried out in three stages, namely, fire temperature calculation, cross sectional temperature evaluation, and then strength, deformation and effective prestress analysis on girders exposed to elevated temperatures. The applicability of the computer program in tracing the response of PC bridge girders from the initial preloading stage to failure stage, due to combined effects of fire and structure loading, is demonstrated through a case study, and validated by test data of a scaled PC box girder under ISO834 fire condition. Results from the case study show that fire severity has a significant influence on the fire resistance of PC T girders and hydrocarbon fire is most dangerous for the girder. The prestress loss caused by elevated temperature is about 10% under hydrocarbon fire till the girder failure, which can lead to the increase in deflection of the PC girder. The rate of deflection failure criterion is suggested to determine the failure of PC T girder under fire.

Evolutionary power spectral density analysis on the wind-induced buffeting responses of Sutong Bridge during Typhoon Haikui

Recent field measurements on long-span bridges during typhoon events have captured strong nonstationary features in the buffeting responses. In this study, the buffeting responses of Sutong Bridge during Typhoon Haikui in 2012 recorded by structural health monitoring system are analyzed to represent the nonstationary characteristics. As an accurately measured state variable, the acceleration response of the main girder is first selected to evaluate its own original stationarity in different time intervals using the run test method. The acceleration response of the main girder can be regarded as a zero-mean nonstationary random process which is in demand to extract its transient features in time–frequency domain. Hence, the evolutionary power spectral density (EPSD) of the acceleration responses, which can present the local turbulence energy distribution in both frequency and time domains, is estimated using the wavelet-based method. Also, an average wavelet spectrum is obtained by averaging the square values of wavelet coefficients along the time axis, and the comparison between the average wavelet spectrum and Fourier spectrum shows a great conformance which indirectly verifies the validity of the obtained evolutionary power spectral density. The results of this study exhibit that there are strong nonstationary characteristics existing in the buffeting responses of Sutong Bridge during Typhoon Haikui, and it is essential to incorporate the nonstationary features of winds in the analysis or design of long-span bridges from an aerodynamic viewpoint.

Modeling parameters for predicting the postbuckling shear strength of steel plate girders

Bridge fires are becoming an increasing concern, and for steel plate girder bridges in particular, web shear buckling is one of the failure mechanisms that can make it necessary to replace the girder after the fire is extinguished. The objective of this study is to evaluate the web shear buckling response of two experimental plate girder specimens subject to fire conditions, and also to determine how complex computational models must be to accurately characterize the web shear buckling response of steel plate girders subjected to fire. Three parameters are evaluated: boundary conditions representing the flange, representation of thermal gradients, and composite action with the slab. To meet this objective, finite element models with varying parameters are compared to each other and to experimental results. Results show that the presence of a composite slab significantly increases the shear capacity of the plate girder. The presence of thermal gradients makes finite element modeling of the flange more sensitive to the results compared to a uniform temperature distribution. Modeling the girder with a uniform temperature equal to the temperature of the web leads to similar results as modeling with thermal gradients.

Behavior Comparison of Prestressed Channel Girders from High-Performance and Ultrahigh-Performance Concrete

In response to the demand for sustainable and improved bridge design practices, the development of emerging materials like ultrahigh-performance concrete (UHPC) is at the forefront of structural innovation. UHPC offers significant advantages to bridge superstructure design as it provides advanced mechanical and durability properties, including high compressive strength and increased tensile capacity. With the introduction of high-strength steel fibers into mixture proportions, postcracking tensile and flexural tensile capacities are increased. These increased tensile capacities provide greater ductility and reduce or possibly eliminate the need for mild steel reinforcement. The present research investigated the behavioral response of full-scale prestressed bridge girders subjected to four-point flexural loading. Two channel-shaped girders were designed to provide equal design moment capacities to facilitate comparative analyses of performance. The first of these girders was designed with high-performance concrete [HPC; 9.5 kips per square inch (ksi; 66 MPa)] and mild steel reinforcement typical of that used in New Mexico bridge designs. The second girder used nonproprietary UHPC [20 ksi (138 MPa)] mixture proportions consisting primarily of local materials, local mixing procedures, and a local curing regimen, all of which were developed at New Mexico State University, Las Cruces. Digital image correlation was used to capture deformations throughout the testing. This information creates a full field of displacements that captures tensile and compressive strain behaviors in the pure moment region. This investigation demonstrated the advantages and improved performance of UHPC and the contribution of steel fiber reinforcement to postcracking strength and flexural capacity.

An experimental study on the dynamic response of a hull girder subjected to near field underwater explosion

An experiment of hull girder model subjected to near field underwater explosion at midship is implemented. High-speed photography is applied to achieve the time history of hog displacement of the hull girder model subjected to shock wave of undex. The determination method of hog distortion using these show-motion pictures is presented. The experiment also achieves the local plate distortion of the hull girder model. Based on these works, the damage mechanism and mode of hull girder subjected to near field undex at midship are discovered. Finally, the coupling effect between whole motion of hull girder and distortion of local structure is discussed.

Global Responses of Struck Ships in Collision With Emphasis on Hydrodynamic Effects

Hydrodynamic effects in ship collisions are usually considered by increased inertia force in the form of the equivalent added mass. It is necessary to reasonably estimate the equivalent added mass to calculate energy absorbed by ships in collisions. In this paper, motion equations in the horizontal plane for the struck rigid ship are first established considering hydrodynamic effects in the form of added mass, linear, and quadratic damping. The equivalent added mass are obtained in three ways and analyzed. It is shown that the equivalent added mass for the sway motion depends on not only the duration of collision impact, impact force, but also the collision position, while the equivalent added mass for the yaw motion could be assumed to be independent of the collision position. In addition, a simple formula is proposed to relate the equivalent added mass for part of the vessel to that of the whole vessel, provided that the underwater area of the transverse section is known. As a consequence, it is possible to estimate rigid hull girder responses based on the simplified methodology, which could be used in design and probabilistic collision analyses. In the end, the hull girder responses are estimated considering both a flexible and rigid vessel. Comparisons are made between rigid and flexible hull girder responses.

Analysis of the influence of geometric, modeling and environmental parameters on the fire response of steel bridges subjected to realistic fire scenarios

This paper studies bridge fires by using numerical models to analyze the response of a typical girder bridge to tanker truck fires. It explains the influence of fire position, bridge configuration (vertical clearance, number of spans) and wind speed on the bridge response. Results show that the most damage is caused by tanker fires close to the abutments in single span bridges with minimum vertical clearance and under windless conditions. The paper provides new insights into modeling techniques and proves that bridge response can be predicted by FE models of the most exposed girder, which saves significant modeling and analysis times.

Shear response of lean duplex stainless steel plate girders

Carbon steel plate girders have been used on a large scale in the building industry. Nowadays, Lean Duplex Stainless Steel (LDSS) plate girders are gaining popularity as they possess greater strength and are more impervious to corrosion than those that are constructed from carbon steel. Regardless of their popularity, there is very limited information with regards to their shear behavior. In this paper, the non-linear finite element analysis was employed to investigate the shear behavior of LDSS plate girders. Parameters considered were the web thickness, the flange width, and the girders aspect ratio. The analysis revealed that although the shear behavior of the LDSS girders was no different from that of carbon steel plate girders, it had obviously been affected by the non-linearity of the material. Furthermore, the selected parameters were found to pronounce effect on the shear capacity of the LDSS girders. That is, the shear capacity increased considerably with web thickness, and increased slightly with flange width. However, it was reduced as the aspect ratio increased. Comparisons between the finite element analysis failure loads and those predicted by the current European Code of Practice revealed that the latter underestimated the shear strength of the LDSS plate girders.

Evaluación de la resistencia a abolladura por cortante de vigas armadas híbridas de acero según la norma venezolana COVENIN 1618:1998

In this paper, an in-depth analysis of the structural response of hybrid steel plate girders subjected to shear forces is presented. The analysis is focused on the Venezuelan Code for Steel Structures COVENIN 1618:1998. The study is based upon a review of experimental tests as well as upon a numerical study carried out by the authors. Both experimental and numerical results are compared with the results provided by the aforementioned Code. Likewise, other relevant Codes such as EN1993-1-5 and AISC-AASHTO are employed for the sake of comparison. The results obtained show that the values given by COVENIN 1618:1998 concerning the shear resistance of hybrid steel plate girders are particularly conservative. A design proposal that may enhance the current COVENIN formulation in this particular topic is presented accordingly.