A New Composite Truss Bridge and a Study on Its Dynamic Characteristics with FE and Experimental Methods

Xiaoli Xie,Yang Huang,Xia Qin 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.3

Improvements to the dynamic characteristics and stiffness of composite girder bridges are necessary to expand their applications and capabilities. The natural frequency of a bridge directly reflects the dynamic characteristics of a structure. From the calculation principle for the natural frequency, the natural frequencies of a bridge can be significantly increased if the load increases slightly while the structural stiffness increases significantly. Based on this, a new type of concrete-steel composite truss bridge is proposed. The new bridge has a reasonable new arrangement for the position of the concrete and steel, according to the bending moment law for continuous girders. The mechanical analysis of the new bridge shows that it has the characteristic of adding a small amount of load at a reasonable position, which can significantly improve the stiffness. Therefore, it is possible to achieve the purpose of improving the dynamic characteristics so that they are far better than those of a conventional composite truss bridge. To further study the dynamic characteristics of the new composite truss bridge, the finite element (FE) method was used to analyse the new bridges, and the results are compared with those of conventional composite truss bridges. Furthermore, several parameters that influence the dynamic characteristics of the new composite truss bridge were studied. Finally, the dynamic characteristics of the small-span new bridge were studied by finite element analysis (FEA) and experiment. The results show that the new composite truss bridges with different span arrangements and different second-stage dead loads always have better natural frequencies and stiffness advantages. Therefore, the new composite truss bridge is suitable for girder bridges with strict requirements for their stiffness and dynamic characteristics, especially for super-long span high-speed railway girder bridges.

An Experimental Study on Negative Bending Behavior of Composite Bridge Decks with Steel-Fiber-Reinforced Concrete and Longitudinal Bulb-Flat Ribs

Chunlei Zhang,Changyu Shao,Qing-Tian Su,Changyuan Dai 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.3

Orthotropic steel–concrete composite bridge deck is a structure composed of an orthotropic steel bridge deck and a cement-based rigid overlay. In recent years, it has been increasingly used to strengthen existing steel decks and build new bridges. Although composite decks with various structural forms and materials have been widely used, studies on the structural behavior of composite bridge decks are still somewhat lacking, and the design approach has not been fully clear. In this study, the mechanical behaviors of a composite bridge deck composed of 80 mm steel-fiber-reinforced concrete (SFRC) and longitudinal bulb-flat ribs were investigated under negative bending. Loading tests of two full-scale composite decks were carried out to study the variations of stiffness, concrete cracks, and structural strain during the loading process. The elastoplastic cross-sectional analysis method and the rigid-plastic analysis method were used in theoretical calculation and the results were compared with the experimental results. It was found that when the composite bridge deck was subjected to negative bending, both the structural deformation and strain variation showed two stages, i.e., elastic stage and elastic–plastic stage, indicating good ductility. In the ultimate failure state, the longitudinal bulb-flat ribs buckled, and the adverse effect of the buckling on bending resistance was revealed. The contribution of the tensile strength of SFRC to the bending resistance was also studied. Furthermore, a new calculation method for the negative bending resistance of this type of composite decks was proposed.

Prediction of vibration and noise from steel/composite bridges based on receptance and statistical energy analysis

Quanmin Liu,Linya Liu,Huapeng Chen,Yunlai Zhou,Xiaoyan Lei 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.37 No.3

The noise from the elevated lines of rail transit has become a growing problem. This paper presents a new method for the rapid prediction of the structure-borne noise from steel or composite bridges, based on the receptance and Statistical Energy Analysis (SEA), which is essential to the study of the generation mechanism and the design of a low-noise bridge. First, the vertical track-bridge coupled vibration equations in the frequency domain are constructed by simplifying the rail and the bridge as an infinite Timoshenko beam and a finite Euler-Bernoulli beam respectively. Second, all wheel/rail forces acting upon the track are computed by taking a moving wheel-rail roughness spectrum as the excitation to the train-track-bridge system. The displacements of rail and bridge are obtained by substituting wheel/rail forces into the track-bridge coupled vibration equations, and all spring forces on the bridge are calculated by multiplying the stiffness by the deformation of each spring. Then, the input power to the bridge in the SEA model is derived from spring forces and the bridge receptance. The vibration response of the bridge is derived from the solution to the power balance equations of the bridge, and then the structure-borne noise from the bridge is obtained. Finally, a tri-span continuous steel-concrete composite bridge is taken as a numerical example, and the theoretical calculations in terms of the vibration and noise induced by a passing train agree well with the field measurements, verifying the method. The influence of various factors on wheel/rail and spring forces is investigated to simplify the train-track-bridge interaction calculation for predicting the vibration and noise from steel or composite bridges.

Three Dimensional Modeling for Steel-Concrete Composite Bridges using Systems of Bar Elements - Modeling of Skewed Bridges

Ioannis Vayas,Theodoros Adamakos,Aristidis Iliopoulos 한국강구조학회 2011 International Journal of Steel Structures Vol.11 No.2

A new improved way for modeling steel composite straight bridges has been presented (Vayas, 2009; Vayas, 2010). The proposed model is based on the representation of steel I-girders through the use of equivalent trusses. The concrete slab is suitably represented by a set of bar elements. Diaphragms and stiffeners may also be taken into account. In contrast to the grillage model, which is usually used for the analysis of bridges, the recommended three dimensional model allows for a more reliable prediction of deformations and internal forces. This paper discusses the extension of the model to skewed composite bridges. The presence of skew makes the analysis complicated and for this reason the grillage analysis is not always recommended. Phenomena like differential deflections of the main girders during concreting and lateral displacements of the flanges can be adequately predicted using the proposed model. The new way for modeling composite bridges, using a spatial system of beam-like structural elements, can also be used for stability analysis of skewed bridges. Worked examples are provided to illustrate the set up procedure of the proposed modeling and to compare the different ways of analysis.

Web Stress Development Mechanism Critical for the Fatigue Limit State in Horizontally Curved Steel Bridges

Mehran Jalali Moghadam,Justin D. Marshall,James S. Davidson 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.2

Although the nominal strength of modern steel bridges that involve increasingly slender elements has been well defined through extensive research and testing, fatigue concerns have not been thoroughly investigated. The out-of-plane displacements of slender webs result in secondary bending stresses at the web boundaries connections, i.e., flange and stiffeners. The so-called “web breathing” phenomenon potentially leads to fatigue crack initiation at the web boundary connections and has been studied for straight girders. Curved steel girders experience large deflection and rotations during construction and service that can intensify the web breathing effect. In addition, the curvature-induced lateral forces pushing and pulling slender curved webs develop mechanisms that can lead to critical web boundary stresses that do not typically occur in straight bridges. This paper aims to define the slender web behavior of composite curved steel bridges essential for the fatigue limit state. It focuses on capturing the distortion-induced web stresses from the construction stage through service using 3D finite element analyses. An advanced technique was applied to simulate the non-composite and composite stages to quantify the continuous web stress development due to geometric nonlinearities. Three different web panels under high shear, high moment, and high shear-moment combination were studied. The stress ranges due to the AASHTO fatigue truck is presented for composite bridges with varying curvature radii. The mechanism involved in curved bridges is defined and the stress magnitudes are compared to that of equivalent straight bridges to understand the role of curvature in intensifying the critical fatigue stress ranges.

Evaluation of multi-lane transverse reduction factor under random vehicle load

Xiaoyan Yang,Jinxin Gong,Bohan Xu,Jichao Zhu 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.19 No.6

This paper presents the two-, three-, and four-lane transverse reduction factor based on FEA method, probability theory, and the recently actual traffic flow data. A total of 72 composite girder bridges with various spans, number of lanes, loading mode, and bridge type are analyzed with time-varying static load FEA method by ANSYS, and the probability models of vehicle load effects at arbitrary-time point are developed. Based on these probability models, in accordance to the principle of the same exceeding probability, the multi-lane transverse reduction factor of these composite girder bridges and the relationship between the multi-lane transverse reduction factor and the span of bridge are determined. Finally, the multi-lane transverse reduction factor obtained is compared with those from AASHTO LRFD, BS5400, JTG D60 or Eurocode. The results show that the vehicle load effect at arbitrary-time point follows lognormal distribution. The two-, three-, and four-lane transverse reduction factors calculated by using FEA method and probability respectively range between 0.781 and 1.027, 0.616 and 0.795, 0.468 and 0.645. Furthermore, a correlation between the FEA and AASHTO LRFD, BS5400, JTG D60 or Eurocode transverse reduction factors is made for composite girder bridges. For the two-, three-, and four-lane bridge cases, the Eurocode code underestimated the FEA transverse reduction factors by 27%, 25% and 13%, respectively. This underestimation is more pronounced in short-span bridges. The AASHTO LRFD, BS5400 and JTG D60 codes overestimated the FEA transverse reduction factors. The FEA results highlight the importance of considering span length in determining the multi-lane transverse reduction factors when designing two-lane or more composite girder bridges. This paper will assist bridge engineers in quantifying the adjustment factors used in analyzing and designing multi-lane composite girder bridges.

Free vibration characteristics of horizontally curved composite plate girder bridges M.Y.

M.Y. Wong,S.A. Osman,N.E. Shanmugam 국제구조공학회 2010 Steel and Composite Structures, An International J Vol.10 No.4

This paper is concerned with free vibration characteristics and natural frequency of horizontally curved composite plate girder bridges. Three-dimensional finite element models are developed for the girders using the software package LUSAS and analyses carried out on the models. The validity of the finite element models is first established through comparison with the corresponding results published by other researchers. Studies are then carried out to investigate the effects of total number of girders, number of cross-frames and curvature on the free vibration response of horizontally curved composite plate girder bridges. The results confirm the fact that bending modes are always coupled with torsional modes for horizontally curved bridge girder systems. The results show that the first bending mode is influenced by composite action between the concrete deck and steel beam at low subtended angle but, on the girders with larger subtended angle at the centre of curvature such influence is non-existence. The increase in the number of girders results in higher natural frequency but at a decreasing rate. The in-plane modes viz. longitudinal and arching modes are significantly influenced by composite action and number of girders. If no composite action is taken into account the number of girders has no significant effect for the in-plane modes.

Life-cycle Cost Analysis of a TPSM Applied Continuous Composite Girder Bridge

( Sang Hyo Kim ),( Jun Hwan Kim ),( Chi Young Jung ),( Jin Hee Ahn ) 한국강구조학회 2010 International Journal of Steel Structures Vol.10 No.2

Transverse cracks in composite girder bridges are repeatedly reported because the tensile stresses in the concrete deck induced by the negative bending moment at the intermediate supports of continuous composite girder bridges. The occurred transverse cracks rapidly deteriorate the concrete deck, giving rise to frequent need for maintenance work. Prestressing methods are usually utilized in this kind of situation for the concrete structures, however no effective and feasible method has yet been proposed for steel-concrete composite structures. A new type of prestressing method entitled Thermal prestressing method (TPSM) has been proposed for innovative construction of continuous composite girder bridges, as effective prestressing method to prevent the occurrence of the tensile transverse crack of the concrete deck at the negative bending moment regions. In this study, the methodology for the economic analysis of TPSM applied bridges and case studies are introduced based on the lifecycle cost, considering initial construction cost and maintenance cost, to demonstrate the financial viability of the TPSM applied bridges compared to conventional continuous composite girder bridges.

합성형교 활하중 횡분배 거동의 실험 및 해석적 연구

박영훈 부천대학 2002 論文集 Vol.23 No.-

본 연구에서는 실제 공용중인 합성 Ⅰ 형교와 합성 강상자형교의 활하중 횡분배 거동을 평가하여 실제 설계에 있어서 기초자료를 제시하고자 현장재하시험 결과중 전 거더가 측정된 교량을 대상으로 교량 난간부를 기준으로 작용 활하중의 횡방향 거리인 차량외측거리의 변화와 거더 간격, 그리고 경간장의 변화에 따른 외·내측, 거더의 응력과 처짐의 분배율변화 양상을 실험적으로 평가하였으며, 합성형교의 활하중 횡분배 거동을 해석적으로 평가하기 위하여 바닥판의 활하중횡분배 기능과 강성비의 효과가 고려되는 구조해석 모델을 이용하여, 외측강성, 하중의 종류 및 재하위치, 거더 간격의 영향을 연구하였다. 또한, 활하중 횡분배의 2차적인 영향인자중 상대적으로 중요한 합성 Ⅰ 형교의 브레이싱의 영향 또한 해석적으로 평 가하였다. The results of field loading test is analyzed to investigate the parameters affecting live load transverse distribution behavior of composite bridge. Thus, the effects of vehicle edge distance, girder spacing on the transverse distribution behavior were evaluated in the field loading test results of composite I girder bridges and composite steel box bridge. From this study, the variation effects of vehicle edge distance and girder spacing were smaller in composite steel box bridge than in composite I girder bridge due to the relatively higher torsional rigidity of composite steel box bridges. At the results of analytical evaluation on the effect of edge stiffness in composite bridge, it was investigated that the stiffness ratio variation effect and girder spacing variation effect were added parameters which affect live load transverse distribution behavior in the same edge stiffness ratio.

복합적층 박스거더의 유효폭 산정을 위한 기초연구

천경식 ( Kyoung Sik Chun ),지효선 ( Hyo Seon Ji ),박원태 ( Won Tae Park ) 한국복합신소재구조학회 2015 복합신소재구조학회논문집 Vol.6 No.3

The domestic and foreign specifications presented the effective width based on flange length to width ratio only. The existing paper on the effective width grasped of the effect of span, load type and cross-section properties, but localized steel bridges. Recently, The studies are going on in progress for the application of fiber reinforced composite material in construction field. Therefore, it is required to optimum design that have a good grasp the deformation characteristic of the displacements and stresses distribution and predict variation of the effective width for serviceability loading. This research addresses the effective width of all composite material box girder bridges using the finite element method. The characteristics of the effective width of composite structures may vary according to several causes, e.g., change of fibers, aspect, etc. Parametric studies were conducted to determine the effective width on the stress elastic analysis of all composite materials box bridges, with interesting observations. The various results through numerical analysis will present an important document for construct all composite material bridges.