Bridge Section Research Articles

Ultimate strength curves of compressive member with box sections in real steel bridges

Ultimate strength curves of compressive member with box sections in real steel bridges

Vertical ground motion influence on seismically isolated & unisolated bridges

In this study, influences of vertical ground motion on seismically isolated bridges were investigated for seven different earthquake data. One assessment of bearing effect involves the calculation of vertical earthquake load on the seismically isolated bridges. This paper investigates the influence of vertical earthquake excitation on the response of briefly steel girder composite bridges (SCB) with and without seismic isolation through specifically selected earthquakes. In detail, the bridge is composed of 30m long three spans, concrete double piers at each axis supported by mat foundations with pile systems. At both end of the spans there exists concrete abutments to support superstructure of the bridge. SCBs which were seismically isolated with ten commonly preferred different lead-rubber bearings (LRB) under each steel girder were analyzed. Then, the comparisons were made with a SCB without seismic isolation. Initially, a preliminary design was made and reasonable sections for the bridge have been obtained. As a result of this, the steel girder bridge sections were checked with AASHTO provisions and analytical model was updated accordingly. Earthquake records were thought as the main loading sources. Hence both cases were exposed to tri-axial earthquake loads in order to understand the effects under such circumstances. Seven near fault earthquake data were selected by considering possession of directivity. Several runs using the chosen earthquakes were performed in order to be able to derive satisfactory comparisons between different types of isolators. Analytical calculations were conducted using well known structural analysis software (SAS) SAP2000. Nonlinear time history analysis was performed using the analytical model of the bridge with and without seismic isolation. Response data collected from SAS was used to determine the vertical load on the piers and middle span midspan moment on the steel girders due to the vertical and horizontal component of excitation. Comparisons dealing with the effects of horizontal only and horizontal plus vertical earthquake loads were introduced.

판별분석을 이용한 고속도로 교량영향권역 교통사고 특성분석에 관한 연구

PURPOSES : The bridge section of the expressway has a worse driving environment than the general section. However, traffic safety countermeasures are focused only on the bridge section. Traffic safety countermeasures on the section before entry to the bridge and the section after exit from the bridge are applied only when the bridge has a long-span section. Accordingly, this study will verify the necessity of extending the application of traffic safety countermeasures to areas that are affected by the bridge. METHODS : This study determines the areas that are affected by the bridge as well as the areas that are affected by locations with frequent traffic accidents and suggests the risk factors by affected areas through canonical discriminant analysis. For the analysis, traffic accident data for 3 years, which occurred on bridge sections in six major expressway lines, were used. RESULTS : The numbers of traffic accidents were 469 before the bridge, 281 on the bridge, and 468 after the bridge. The variables that have impact on the seriousness of accidents are as follows: speeding, excess manipulation of the steering wheel, and failure to secure safety distance for accidents that occurred before the bridge section; speeding, excess manipulation of the steering wheel, and dozing off for accidents that occurred on the bridge; and speeding and failure to secure safety distance for accidents that occurred after the bridge section. CONCLUSIONS : Areas affected by the bridge show higher accident rates than the bridge section; therefore, imposing traffic safety countermeasures on the integrated section of the bridge and the affected areas is required. It is believed that the results suggested in this study could be effectively used in the prevention of traffic accidents by imposing custom-made safety countermeasures for each section.

Bearing Capacity and Assessment of Old Filler-Beam Bridge Decks

Two sections of an old decommissioned filler-beam railroad bridge were test loaded in order to determine their structural performance and ultimate load. The loaded bridges were studied with two kinds of finite element (FE) models to observe how well the design theories of composite structures match the observed behaviour of the almost 100 year old bridge decks. The objects of research were the existence and level of composite action between the steel beams and the concrete slab as well as other factors related to the condition of materials or structural details that could have had an effect on the bearing capacity of the bridge. Comparison of the test results and FE models gave information on the structural behaviour of the loaded filler-beam bridge sections. The results can help in the assessment of other similar structures.

A calamitalean forest preserved in growth position in the Pennsylvanian coal measures of South Wales: Implications for palaeoecology, ontogeny and taphonomy

A newly discovered fossil forest is reported from Lower Pennsylvanian (late Langsettian) strata in the classic Amroth to Wiseman’s Bridge section of Pembrokeshire, South Wales. It comprises nearly two hundred sediment-cast Calamites axes and putative groundcover ferns, preserved in growth position in the deltaic mouth bar deposits of a marine-influenced coastal plain. Vegetation-Induced Sedimentary Structures developed around upright axes imply that dense Calamites thickets promoted localized patterns of sedimentation, and ultimately, stabilized substrates, paving the way for the establishment of mire vegetation. Not long after initial colonization, a short-lived brackish incursion resulted in dieback of the Calamites thickets; however, a few axes survived to recolonise the delta front through adventitious regeneration, implying that calamitaleans were, to a limited degree, saline tolerant. A remarkable feature of the fossils is that many examples preserve an internal pith-cast embedded within a stem-cast. Preservation of both pith- and stem-casts for the same plant allows inference of an ontogenetic growth-series, and shows that these clastic-substrate Calamites were much more substantially ‘woody’ than previously conjectured. This raises the possibility that plastic developmental traits like growth rate and longevity may have been what mainly distinguished these opportunistic Calamites in disturbed clastic settings from their much larger, and even more woody, cousins in adjacent mires. Analysis of the fossils also contributes to taphonomic debates, supporting the hypothesis that upright Calamites axes are mostly preserved as stem-casts (rather than pith-casts, as traditionally believed). As such, the newly discovered fossil forest sheds light on the ecology, ontogeny, and taphonomy of Calamites – an iconic, familiar, yet, insufficiently understood Pennsylvanian plant.

Application of remote sensing and GIS for evaluation of the recent morphological characteristics of the lower Brahmaputra-Jamuna River, Bangladesh

This paper deals with the morphological changes of the lower Brahmaputra-Jamuna River (BJR) in Bangladesh. Within few decades, the planform of the river has been changed abruptly by the combined effect of natural process and human interventions. Morphological features observing in this study were river planform, channel width, bankline migration and channel bed elevation. Eighteen sets of remote sensing data series from 1973 to 2011were analyzed using ERDAS/Imagine and GIS to document the variation of geomorphic elements of the lower BJR. GIS analysis of remote sensing data showed that the changes of channel planform were quite significant over the past 40 years, occurring two major phases of channel development. The changing patterns in the first phase (i.e., between 1973 and 1992) were quite irregular. However, the second phase ranging between 1992 and 2011 was unidirectional (mostly eastward). In general, the studied river reach was widened and the average rate of migration was 225 m y–1 that was three–folds the values of the first phase. The height and slope of sand bars were gradually increasing, showing the highest value around the Jamuna Multipurpose Bridge (JMB) section. The planform characteristics of BJR at the downstream of JMB showed that the river reach was gradually widening and shifting eastwards. However, the reach at the upstream of the JMB showed westward migration. The recent trends of channel changes suggest that the river planform has lost it’s naturally condition and it may, therefore, be predicted that increasing nature of channel width likely to continue in the immediate future.

SPSA Algorithm based Optimum Design of Longitudinal Section of Bridges

The purpose of this study is to determine the optimum design of arch longitudinal no prismatic single-cell section. The FE model of the Cetina open spandrel arch bridge was constructed using the ANSYS. In this present work the optimum design is carried out by taking total material volume of substructure of bridge as objective function. Substructure includes of column and reinforced concrete arch. Finally, the optimization technique is performed by Simultaneous Perturbation Stochastic Approximation (SPSA) algorithm. It is concluded that SPSA can be effectively used in the shape optimization of the bridges.

Experimental study on aerodynamic derivatives of a bridge cross-section under different traffic flows

The presence of traffic on a bridge deck has an important primary impact on the bridge cross-section׳s aerodynamic configuration, which may affect the static force coefficients and the aerodynamic derivatives that will in turn influence the self-excited forces acting on the bridge. Compared to the investigations of the traffic effect on the static force coefficients, its effect on the aerodynamic derivatives is rather rarely studied. In the present study, the forced vibration device is adopted in the wind tunnel to test a scaled bridge section model with vehicle models distributed on the bridge deck considering three simulated traffic flows. The influence of vehicles of different traffic flows under different wind attack angles on the aerodynamic derivatives of the bridge with the reduced wind velocity are investigated based on the experimental results. The measured results show that the influence of vehicles on the aerodynamic derivatives of the bridge cannot be ignored. The impacts of vehicles under different traffic flows on the aerodynamic derivatives are different for different aerodynamic derivatives. The effect of vehicles on the aerodynamic is different for different wind attack angles and different for different traffic flow conditions at a certain attack angle.

Analytic Calculation of Capillary Bridge Properties Deduced as an Inverse Problem from Experimental Data

In this work, we propose an original resolution of Young–Laplace equation for capillary doublets from an inverse problem. We establish a simple explicit criterion based on the observation of the contact point, the wetting angle and the gorge radius, to classify in an exhaustive way the nature of the surface of revolution. The true shape of the admissible static bridges surface is described by parametric equations; this way of expressing the profile is practical and well efficient for calculating the binding forces, areas and volumes. Moreover, we prove that the inter-particle force may be evaluated on any section of the capillary bridge and constitutes a specific invariant.

Some new insights into the identification of bridge deck flutter derivatives

In the identification of flutter derivatives using coupled free vibration technique, the influences of implied approximations are assessed in this study. For a thin flat plate section and three representative deck sections of long-span bridges, KH1∗, KH2∗, KA1∗, KA2∗, K2H3∗, K2H4∗, K2A3∗, and K2A4∗ are demonstrated to be dependent on reduced wind velocity, especially at lower reduced wind velocities. This is contrary to the commonly used assumption of these parameters being constants. Kh is conventionally used to quantify H1∗, H4∗, A1∗, A4∗, and Kα for H2∗, A2∗, H3∗, A3∗. This means the direct components of aeroelastic motions (h1,α2) are comparatively predominant than the incentive cross components (h2,α1). However, this approximation is only valid for weak modal coupling cases at lower wind velocities. Novel perspectives are provided regarding the subtle underlying complexities in extracting flutter derivatives using coupled free vibration technique. The accuracy in identifying flutter derivatives can be effectively improved by setting close frequencies of coupled modes. The mechanical damping ratio, mass, and mass moment of inertia can be artificially increased to postpone the occurrence of flutter and extend the reduced wind velocity region to acquire sufficient flutter derivatives for flutter analysis. This study may serve as a building block for improving the understanding of flutter derivative identification from coupled free vibration responses, and practical strategies are proposed to improve the identification accuracy.

Study on Navigation Technology of Waterway at Hub Downstream and Bridge Area Overlapping

The article has used the technical route of data analysis、physical model test and ship model tests combining, studied the navigation technology of waterway in area below QianWei hydro-junction and bridge sections overlapping in Minjiang River, then proposed the regulation scheme, which effectively improved navigation conditions in the region, finally summarized and put forward the navigable protection technologies and measures in area below hub and bridge area.

Anthropogenic effects and climate change threats on the flood diversion of Erchung Floodway in Tanshui River, northern Taiwan

The Erchung Floodway, one of the successful measures of the Taipei Flood Prevention System, was constructed to mitigate the Tanshui River floods in the Taipei metropolitan area. The Taipei metropolitan area is the most crowded region in Taiwan. More than one-third of the total population of the country resides in this area. However, its function has changed due to urban development and natural alterations over time. The main concerns of this study are to investigate the current diversion capacity and the current vulnerability of the Taipei Flood Prevention System in accordance with influential environmental factors, including anthropogenic effects and climate change threats. Thirty-two scenarios were established for sensitivity analysis using HEC-RAS model. The results indicate that the capacity of the Erchung Floodway diversion has noticeably decreased from 9,200 to 6,300 m3/s under a 200-year recurrence flood. Three vulnerable locations have been identified: Shihtzutou, Shezi, and Wugu. It was also found that the Taipei Flood Prevention System will encounter challenges if the roughness of the riverbed within the Erchung Floodway increases by over 50 %, the roughness of the riverbed within the Tanshui River increases by over 25 %, the water stage at the river mouth rises to 5.03 m, or the 200-year recurrence flood increases to 28,300 m3/s. Two proposed cost-effective mitigation strategies in the present study are: (1) to remain or decrease the riverbed elevation and roughness within the Tanshui River (Taipei Bridge section); (2) to decrease the riverbed roughness by at least 25 % within the upstream and midstream of the Erchung Floodway.

Practical Diagrammatical Technique for 3-DOF Bridge Flutter Analysis

For long bridges with bluff deck sections, the influence of lateral wind loads on flutter performance needs to be carefully investigated. In this paper, an advanced three-degree-of-freedom (3-DOF) analytical framework considering lateral aeroelastic effects is developed to refine bridge flutter analysis. This approach uses high-order nonlinear equations to determine twin critical flutter parameters, i.e., velocity and frequency. An optimization model to determine the critical flutter parameters is developed. A practical diagrammatical technique is proposed to solve this problem, which is an improvement over the traditional optimization techniques. The intuitiveness and effectiveness of the diagrammatical technique is fully verified using a numerical example. The optimization model and diagrammatical technique are applied to the 3-DOF flutter analyses of two bridges with bluff deck sections. It is revealed that the flutter derivatives H5∗, H6∗, A5∗, A6∗, and Pi∗ (i=1,2,…,6) play an insignificant role in flutter performance of both bridges. If H5∗=H6∗=A5∗=A6∗=0, the Pi∗ (i=1,2,…,6) will be paralyzed, and the influence of only the conventional eight flutter derivatives, those related to the heaving and torsional motions, can be considered. On the other hand, if Pi∗=0 (i=1,2,…,4), H5,6∗, A5,6∗, and P5,6∗ will also lose efficacies. These novel findings are first presented, which can be steadily proved by the explicit expression of the optimization model. This study presents a valuable insight into the flutter characteristics of both bridges and explores the roles in the flutter onset played by various parameters. Further, even with bluff deck sections of both bridges, the analytical results of 2-DOF vertical-torsional coupled flutter for the Akashi Kaikyo Bridge and the 1-DOF torsional flutter for the Suramadu Bridge are coincident with the experimental observations. Thus, the effectiveness of analytical framework is again verified.

Indicial functions in the aeroelasticity of bridge decks

This paper presents the development of indicial functions (IFs) for two-dimensional bridge deck sections. A new set of IFs predicted for the cross section of the Great Belt Bridge (GBB) are discussed. Two approaches, based on the time- and frequency-domain descriptions, are applied. In time domain, IFs are determined by imposing an instantaneous change to a system state variable, e.g., the angle of attack (AOA) of air flow to the bridge section. In frequency domain, indicial representation is derived from the aeroelastic (or flutter) derivatives typically used to define the self-excited harmonic forces in an eigenvalue problem and generated by imposing a sinusoidal motion to the bridge section and performing a sweep in the frequency range of oscillations of the section. IFs are thus evaluated by exploiting the reciprocal relations that exist between them and the aerodynamic derivatives. To determine the aerodynamic response of a bridge cross section due to a step change in the AOA and to calculate the flutter derivatives from sinusoidal oscillations, the meshless discrete vortex method implemented in DVMFLOW® is adopted. The results from the proposed work can be applied in the development of reduced-order models (ROM) of aerodynamic loads suitable to investigate fluid–structure interaction (FSI) problems associated with practical analysis of wind effects on long-span bridges, including phenomena such as flutter, vortex-induced vibration, buffeting and galloping. The IFs reported in this paper illustrate the importance of flow separation and vortex shedding and their dependence on the magnitude of the change in a state variable such as, in particular, the AOA for the cases reported herein.

Wind-Induced Performance of Long-Span Bridge with Modified Cross-Section Profiles by Stochastic Traffic

The presence of traffic on a slender long-span bridge (SLB) deck has two types of primary impacts: (1) modification of the bridge cross-section profiles, which may influence the flutter derivatives and in turn, wind-induced aeroelastic loads acting on the bridge; and (2) additional dynamic loads acting on the bridge including dynamic interactions from the vehicles. As compared to the investigations on the impact of traffic as external dynamic loads, those on the impact from the modification of bridge cross-section profiles are rather rare. A scaled bridge section model with vehicle models distributed on the bridge section has been tested in the wind tunnel laboratory. With the FDs obtained from the wind tunnel experiments of various modified bridge cross-section profiles by stochastic traffic, the present study is to numerically evaluate the impact on the wind-induced performance of the long-span bridge, such as the buffeting response and fatigue damage accumulation.

Study and Comparison of Aerodynamic Forces on an Aircraft and Suspension Bridge

Aerodynamic forces are time varying forces experienced by objects undergoing air flow. The effect of these forces depends upon the shape and size of the objects. The aerodynamic force acting on a bluff body like bridge deck is different from that acting on a stream line body like an aircraft.This paper focus on the study and comparison of aerodynamic forces acting on an air craft and a bridge deck. I. INTRODUCTION Researches are booming in the area of aero-dynamics of civil structures, which are not usually designed to influence or accommodate the airflow over them, but rather with other objectives in view. The aero-dynamics of such structures is characterized by separated flow and turbulent wakes exhibiting widely varying degrees of flow organizations. A body immersed in a fluid flow is subjected to surface pressures induced by the flow. If the oncoming flow is turbulent, this will be one of the sources of time dependent surface pressure. If the body moves or deforms appreciably under the induced surface pressure, these deflections, changing as they do the boundary conditions of the flow, will affect the fluid forces, which in turn will influence the deflections. Aero- elasticity is the discipline concerned with the study of the phenomenon wherein aero-dynamic forces and structural motions interact significantly. If the body in the fluid flow deflects under some forces and the initial deflection gives rise to successive deflections of oscillatory and/or divergent character, aero-elastic instability is said to be produced. All aero-elastic instabilities involve aero-dynamic forces that act on the body as a consequence of its motion. Such forces are termed self-excited. A body is said to be aerodynamically bluff when it causes the wind flow around it to separate from its surface leaving a significant trailing wake. In contrast, wind flow around a streamlined body remains tangential and attached to its entire surface, leaving a narrow trailing wake. Most civil engineering structures, including the bridge sections of the long span bridges qualify as bluff bodies, while the shapes of an airfoil belong to the category of a streamlined body. The fundamental aspects of aero-elastic phenomena that need to be taken into account in the design of certain structural members, towers, stacks, tall buildings, suspension bridges, cable roofs piping system and power lines are not completely understood. Without aerodynamics airplanes cannot fly. Thus while considering performance of an aircraft it is no surprise that aerodynamics is a vital aspect. The philosophy of good aerodynamics is primarily derived from low drag. Aerodynamics is dynamics related with flow of air. It is classified into two external aerodynamics and internal aerodynamics. External aerodynamics deals with flow of air over a body. Internal aerodynamics deals with flow of air with in ducts.

Vehicle-bridge coupling vibration analysis based fatigue reliability prediction of prestressed concrete highway bridges

The extensive use of prestressed reinforced concrete (PSC) highway bridges in marine environment drastically increases the sensitivity to both fatigue-and corrosion-induced damage of their critical structural components during their service lives. Within this scenario, an integrated method that is capable of evaluating the fatigue reliability, identifying a condition-based maintenance, and predicting the remaining service life of its critical components is therefore needed. To accomplish this goal, a procedure for fatigue reliability prediction of PSC highway bridges is proposed in the present study. Vehicle-bridge coupling vibration analysis is performed for obtaining the equivalent moment ranges of critical section of bridges under typical fatigue truck models. Three-dimensional nonlinear mathematical models of fatigue trucks are simplified as an eleven-degree-of-freedom system. Road surface roughness is simulated as zero-mean stationary Gaussian random processes using the trigonometric series method. The time-dependent stress-concentration factors of reinforcing bars and prestressing tendons are accounted for more accurate stress ranges determination. The limit state functions are constructed according to the Miner's linear damage rule, the time-dependent S-N curves of prestressing tendons and the site-specific stress cycle prediction. The effectiveness of the methodology framework is demonstrated to a T-type simple supported multi-girder bridge for fatigue reliability evaluation.

Analysis of Thermal Effect on Girder with Side Main Rib Section

According to the common girder with side main rib section of PC cable-stayed bridge with double cable planes, a computational model of two-dimension temperature field is presented. Temperature gradient of main rib, small longitudinal rib, top plate and flange plate was computed respectively, and then the stress and strain of each section are derived through plane cross-section assumption. For the cable-stayed bridge, member structure FEM is applied to compute node equivalent load and displacement, which resulted from both sunshine and seasonal thermal difference. Finally, a case study is analyzed, the results showed: computed and measured deflection of girder that result from thermal effect are very close, therefore, this method is feasible.

Palaeomagnetic and synchrotron analysis of >1.95 Ma fossil-bearing palaeokarst at Haasgat, South Africa

Palaeomagnetic analysis indicates that Haasgat, a fossil-bearing palaeocave in the Gauteng Province of
 South Africa, is dominated by reversed magnetic polarity in its oldest, deepest layers and normal polarity in
 the younger layers. The presence of in-situ
 Equus
 specimens suggests an age of less than ~2.3 Ma, while
 morphological analysis of faunal specimens from the ex-situ assemblage suggests an age greater than
 1.8 Ma. Given this faunal age constraint, the older reversed polarity sections most likely date to the beginning
 of the Matuyama Chron (2.58–1.95 Ma), while the younger normal polarity deposits likely date to the very
 beginning of the Olduvai Sub-Chron (1.95–1.78 Ma). The occurrence of a magnetic reversal from reversed
 to normal polarity recorded in the sequence indicates the deposits of the Bridge Section date to ~1.95 Ma.
 All the in-situ fossil deposits that have been noted are older than the 1.95 Ma reversal, but younger than
 2.3 Ma. Haasgat therefore dates to an interesting time period in South African human evolution that saw
 the last occurrence of two australopith species at ~2.05–2.02 Ma (Sts5
 Australopithecus africanus
 from
 Sterkfontein Member 4) to ~1.98 Ma (
 Australopithecus sediba
 from Malapa) and the first occurrence of
 early
 Homo
 (Sk847),
 Paranthropus
 and the Oldowan within Swartkrans Member 1 between ~2.0 Ma and
 ~1.8 Ma.

Modelling and Control of a Suspended-Span Bridge Section

We study the modelling and flutter suppression of a suspended-span bridge section using aerodynamic control means. The aerodynamic actuators are controllable leading- and trailing-edge flaps fitted to both edges of the bridge deck. The modelling is based on thin aerofoil theory which describes the bridge deck - air stream interactions. The model also consider the mass and inertia effects of the flaps. Passive mechanical controllers are proposed that sense the vertical velocity of the leading- and trailing-edge flap pivots and use these signals to produce control torques and adjust the flap angles accordingly. The control system is insensitive to the wind direction in the case of identical leading- and trailing-edge mechanical controllers. The Akashi-Kaikyo bridge is used as a working example for the numerical simulation evaluation of the control system performance.