Single Girder Research Articles

Embodied CO2 Reduction Effects of Composite Precast Concrete Frame for Heavily Loaded Long-Span Logistics Buildings

For heavily loaded long-span (HLS) logistics buildings, embodied CO2 (ECO2) of a structural frame accounts for more than 80% of the CO2 emissions of the entire building. To realize a sustainable structure from the CO2 perspective, an innovative construction method that reduces ECO2 of a structural frame is required. Through studies conducted over several years, we have developed a SMART (Sustainable, Measurable, Attainable, Reliable, and Timely) frame that is a steel connected composite precast concrete (CPC) frame that significantly reduces not only construction time and cost but also ECO2. If a SMART frame is applied to HLS logistics buildings, ECO2 reduction effects are expected to be substantial. To prove this, this study aims to analyze ECO2 reduction effects of the CPC frame for HLS logistics buildings. An HLS logistics building constructed with the existing precast concrete (PC) frame was selected as a case project. Thereafter, the typical PC girder was redesigned using the SMART frame; then, analysis was conducted on the quantity take-off of resources, such as form, rebar, steel, and concrete, as well as on ECO2 and production cost. As a result of the analysis, in the case of a single typical girder of the SMART frame, 730 kg-ECO2, which accounts for 9.52% of the CO2 emissions, was reduced compared to that of the existing PC frame. If only the typical girders of the case project are applied, a relatively larger quantity of 465 ton-ECO2 will be reduced. The results of this study will contribute in securing structural stability, as well as achieving a sustainable structure that leads to an unprecedented reduction of ECO2.

Fire Performance of Continuous Steel-Concrete Composite Bridge Girders

This paper presents a detailed investigation in to fire resistance along with failure mode in continuous steel-concrete composite twin I-shaped bridge girders under different localized fire through considering fire severity and fire exposure positions namely; mid-span zone in one of the two span, hogging moment zone and side-support zone. A 3-D finite element (FE) model, built utilizing the computer program ANSYS, is used to track structural fire performance in a typical two span of continuous composite twin I-shaped bridge girders (fabricated with twin I-shaped plates supporting a concrete slab) dependent on thermomechanical coupled analysis. The model validation is undertook through comparison of temperature and deflection response attained from a scaled composite single I-shaped girder tested exposed to ISO834 fire. The numerical analysis results show that the developed model can be favorably used to analyze the behavior and failure mode of continuous steel-concrete composite twin I-shaped bridge girders during entire range of fire exposure. Fire severity and fire exposure positions present critical influence in to the fire resistance of continuous composite bridge girders. Fire exposure prevention on hogging moment zone can significantly extend failure time of continuous girders, and further hold back progressive structural collapse. Web buckling based failure criterion can be applicable to calculate fire resistance of realistic continuous girders under simultaneous structural loading together with localized fire. Continuous composite bridge girders subjected to localized fire present highly significant local deformation response in the fire exposed bridge girder span.

Ultimate strength of horizontally curved I-girders with round concrete-filled tubular flange

Concrete-filled tubular flange girders (CFTFGs) are a composite member which replaces the flat-plate flange of the conventional I-girder with a concrete-filled tubular one. As a single axisymmetric girder, the bending, torsion, and warping geometric equations of curved CFTFGs, as well as the balance equations in and out of the plane, are coupled. These problems make it sophisticated to settle the ultimate strength of curved CFTFGs. Besides, the existing current design specifications do not involve a calculation method of the ultimate strength of individual curved CFTFGs. Therefore, the present study focuses on the ultimate strength and behaviour of curved round concrete-filled tubular flange girders (CRCFTFGs) under concentrated load at mid-span. Based on the verified finite element (FE) model, the elastoplastic behaviour of CRCFTFGs is analysed. Subsequently, the theoretical analysis model of CRCFTFGs is established, and the calculation methods of the elastic lateral-torsional buckling (LTB) moment and the full plastic bending moment on the cross-section of CRCFTFGs are proposed. The comparison between the theoretical and FE results indicated that they are in good agreement. Lastly, based on the ECCS formula and the theoretical analysis model of CRCFTFGs, the calculation formula of the ultimate strength of CRCFTFGs considering the effect of curvature is suggested. The accuracy of the presented formula is verified through comparisons with the FE and existing experimental results. The suggested formula for calculating the ultimate strength of CRCFTFGs can provide theoretical guidance for the code formulation.

Analysis of RCC T-beam and prestressed concrete box girder bridges super structure under different span conditions

A bridge is a structure that provides passage over an obstacle without closing the path below. The required crossing may be for a road, rail, pedestrian, canal, or pipe. For constructing the bridges has many types of sections among which Tee beam and Box girder bridges have selected. T-beam bridges are cast-in-situ bridges, popular for short spans and economical. Similarly, the widely used box girder bridge selected which is economical for long spans, that may be either single or multi-celled girder. The type of bridge is concerned with providing maximum efficiency of material and construction technology. As the span increases, the dead load that is an important growth factor also increases. To reduce dead load, unnecessary material, which not used to its full potential, is removed from this section, which can be in the shape of box girders or cellular structures depending on whether the shear deformations neglected or not. In the present study, a two-lane simply supported RCC Tee beam girder and prestressed concrete box girder bridge analyzed and designed for dead load and IRC moving loads, where the considered moving load is of the tracked vehicle of class A-A loading. Courbon's method adopted for analysis and designing. Dead load and live load calculations have done manually. Shear force and bending moment for a vehicular load have calculated. Piguead's curves used for bending moment calculations. The main objective of this paper is to check whether both the T and box girder bridges have adopted for the assumed data with different span conditions.

Numerical study of wake and aerodynamic forces on a twin-box bridge deck with different gap ratios

Two-dimensional Delayed Detached Eddy Simulation (DDES) was carried out to investigate the uniform flow over a twin-box bridge deck (TBBD) with various gap ratios of L/C=5.1%, 12.8%, 25.6%, 38.5%, 73.3% and 108.2% (L: the gap-width between two girders, C: the chord length of a single girder) at Reynolds number, Re=4x104. The aerodynamic coefficients of the prototype deck with gap ratio of 73.3% obtained from the present simulation were compared with the previous experimental and numerical data for different attack angles to validate the present numerical method. Particular attention is devoted to the fluctuating pressure distribution and forces, shear layer reattachment position, wake velocity and flow pattern in order to understand the effects of gap ratio on dynamic flow interaction with the twin-box bridge deck. The flow structure is sensitive to the gap, thus a change in L/C thus leads to single-side shedding regime at L/C󖼩.6%, and co-shedding regime at L/C󖼳.8% distinguished by drastic changes in flow structure and vortex shedding. The gap-ratio-dependent Strouhal number gradually increases from 0.12 to 0.27, though the domain frequencies of vortices shedding from two girders are identical. The mean and fluctuating pressure distributions is significantly influenced by the flow pattern, and thus the fluctuating lift force on two girders increases or decreases with increasing of L/C in the single-side shedding and co-shedding regime, respectively. In addition, the flow mechanisms for the variation in aerodynamic performance with respect to gap ratios are discussed in detail.

Girder Lattice Model and Single Beam Model In Load Test of Continuous Box Bridge Computational Comparison and Analysis

The static load test of a three-span continuous box girder in Huzhou City, Zhejiang Province is analyzed and calculated by using the grillage method and the single main girder method. The rationality of the two calculation models is compared with the field load test data. The calculation results show that the results of grillage method are more consistent with the experimental results than that of single girder method, and the safety of the calculation results is higher. Therefore, in the load test of multi-compartment box girder bridge, the grillage method is more reasonable and can better reflect the mechanical characteristics of the bridge structure.

Structural analysis of single girder overhead crane using SS400 and ST52-3 steel plate

This paper is aimed to review the structure of single girder overhead crane using finite element analysis (FEA) technique. The strength and stiffness of existing single girder overhead crane with the capacity of 10 tons SWL and a span of 14 meters are calculated. The existing structure using SS400 steel plates is evaluated and compared with a new design using ST52-3. The stress and deformation of the existing structure are analyzed using Ansys software and a new design is proposed. Further, the effect of girder weight reduction to the decreasing of power required by the long-traveling motor is identified. The analysis shows the reduction of structure mass on the new design is 0.8 tons and the decrease in required traveling power is 1 kW. The maximum stresses of the existing and the new structure are 25 percent and 23 percent of the yield strength of the SS400 and ST52-3. The percentages of the maximum deformation to the allowable deflection limit are 43 percent and 58 percent, respectively.

Study on the Seismic Performance of Different Combinations of Rubber Bearings for Continuous Beam Bridges

Rubber isolation bearings have been proven to be effective in reducing the seismic damage of bridges. Due to the different characteristics of isolation bearings, the mechanical properties of bridges with different combinations of rubber bearings are complex under the action of earthquakes. This paper focuses on the application of combinations of rubber isolation bearings on seismic performance of continuous beam bridges with T‐beams. The seismic performances of continuous beam bridges with different combinations of rubber isolation bearings, pier height, and span length were studied by the dynamic time history analysis method. It was found that the bridges with natural rubber bearings (NRBs) have the largest seismic responses compared to the other types of bearings. The continuous beam bridge with isolation bearings, such as lead rubber bearings (LRBs) and high damping rubber bearings (HDRBs), has approximately 20%∼30% smaller seismic response than that with NRBs under the action of earthquakes due to the hysteretic energy of the bearings, indicating that the isolation bearings improve the seismic performance of the bridge. The continuous beam bridges with both NRBs and LRBs or NRBs and HDRBs have larger seismic response of the piers than those with a single type of isolation bearings (LRBs or HDRBs) but smaller seismic response of the piers than those with only NRBs. For a continuous beam bridge with shorter span and lower pier, it is not economical to use LRBs or HDRBs underneath every single girder, but it is more reasonable to use cheaper NRBs underneath some girders. The larger difference in stiffness of the bearings between the side and middle piers leads to the more unbalanced seismic response of each pier of the bridge structure. The results also show that with increasing pier height and span length, the difference in the seismic response value between the cases gradually increases.

Differences between hollow slab Grillage model and single beam model in design and analysis

Hollow slab girder bridge has the advantages of factory prefabrication, fast construction speed, small girder height and low cost. It is one of the main types of small and medium span bridges in China. In this paper, a hollow slab bridge with an effective span of 10.22m is taken as the research object. The Grillage method and single girder method of MIDAS/Civil finite element software are used to model and calculate the bridge, and comparing the difference between the results of two models in design analysis. The calculated value of single beam model is larger than that of Grillage model, and more insecure. The difference of stress calculation between the two models can be up to 1.2 MPa. For safety reasons, two kinds of modeling methods can be used for analogy in design, but when the structure is more complex, the model of the Grillage model should be closer to the actual situation.

Discussion on the installation checking method of precast composite floor slab with lattice girders

Based on the installation checking requirements of China’s current standards and the international norms for prefabricated structural precast components, it proposed an installation checking method for precast composite floor slab with lattice girders. By taking an equivalent composite beam consisted of a single lattice girder and the precast concrete slab as the checking object, compression instability stress of upper chords and yield stress of slab distribution reinforcement at the maximum positive moment, tensile yield stress of upper chords, slab normal section normal compression stress and shear instability stress of diagonal bars at the maximum negative moment were checked. And the bending stress and deflection of support beams, strength and compression stability bearing capacity of the vertical support, shear bearing capacity of the bolt and compression bearing capacity of steel tube wall at the bolt were checked at the same time. Every different checking object was given a specific load value and load combination. Application of installation checking method was given and testified by example.

A design approach of integral-abutment steel girder bridges for maintenance

Integral abutment bridges (IABs) have no joint across the length of bridge and are therefore also known as jointless bridges. IABs have many advantages, such as structural integrity, efficiency, and stability. More importantly, IABs have proven to be have both low maintenance and construction costs. However, due to the restraints at both ends of the girder due to the absence of a gap (joint), special design considerations are required. For example, while replacing the deck slabs to extend the service life of the IAB, the buckling strength of the steel girder without a deck slab could be much smaller than the case with deck slab in place. With no deck slab, the addition of thermal expansion in the steel girders generates passive earth pressure from the abutment and if the applied axial force is greater than the buckling strength of the steel girders, buckling failure can occur. In this study, numerical simulations were performed to estimate the buckling strength of typical steel girders in IABs. The effects of girder length, the width of flange and thickness of flange, imperfection due to fabrication and construction errors on the buckling strengths of multiple and single girders in IABs are studied. The effect of girder spacing, span length ratio (for a three span girder) and self-weight effects on the buckling strength are also studied. For estimation of the reaction force of the abutment generated by the passive earth pressure of the soil, BA 42/96 (2003), PennDOT DM4 (2015) and the LTI proposed equations (2009) were used and the results obtained are compared with the buckling strength of the steel girders. Using the selected design equations and the results obtained from the numerical analysis, equations for preventing the buckling failure of steel girders during deck replacement for maintenance are presented.

Three-dimensional finite element temperature gradient analysis in concrete bridge girders subjected to environmental thermal loads

A thermal finite element study was carried out to investigate the temperature gradients in bridges with precast concrete girders that subjected to the daily and seasonal environmental variations of solar radiation and air temperature. The proposed finite element model was used to simulate the three-dimensional thermal behavior considering the extreme thermal loads of the region of Gaziantep, Turkey. Two construction stages were studied, the single girder and the girders-deck slab superstructure before surface topping. The results show that the maximum temperature gradient at the top surface was greater for the unsurfaced superstructure by about 6 °C. The predicted extreme temperature gradient distributions for the two construction stages were compared with the current American Association of State Highway and Transportation Officials (AASHTO) gradient model. The comparison showed that the current AASHTO temperature gradient distribution agreed well with the predicted gradient of the single girder, while a higher deviation was noticed when compared with the predicted gradient of the bridge superstructure. Moreover, the current AASHTO gradient model slightly overestimated the maximum predicted gradient of the single girder, while it underestimated the maximum gradient of the bridge superstructure.

Design and Stress Analysis of Single Girder Jib Crane

Design and Stress Analysis of Single Girder Jib Crane

Seismic response study on a multi-span cable-stayed bridge scale model under multi-support excitations. Part II: numerical analysis

In recent years, local component destruction, collapse failure and the control of long-span cable-stayed bridges under strong multi-support excitations have received increasing attention. In this paper, two kinds of nonlinear finite element (FE) models are established to simulate the seismic responses and failure modes of a multi-span cable-stayed bridge scale model under multi-support excitations. One is the single girder model which is used to simulate the seismic response during four wave excitations. It can be concluded that the FE analysis results of the scale model are a good fit with those from the shaking table tests. The other one is the explicit dynamic FE model which is used to simulate the collapse and failure mechanisms of the scale model during strong earthquakes. The aggressive failure processes of the scale model under two different types of wave excitations were compared to reproduce the mechanisms in which the bearing at the middle tower failed under the El Centro (EC) wave (4.0 m/s2), and we also observed the connection failure of the cables and towers, and the elements failure of the upper beam in the middle tower, which occurred successively under a Jiangxin (JX) wave (4.0 m/s2). This simulation may be referenced as the basis for the collapse failure of a cable-stayed bridge with a large span during a strong earthquake.

경골형 교량거더의 비틀림에 의한 말뚝연결부 응력저감기법

조립식지그재그 형태의 단일거더시스템이 적용되는 경골형 교량은 비틀림에 취약한 구조이다. 특히 거더와 PHC(Pretensioned spun High strength Concrete) 말뚝의 고정 연결부는 비틀림 하중에 의한 과도한 응력이 집중되는 취약부이므로 이를 저감시키기 위한 방안이 요구된다. 본 연구에서는 연결부에 발생하는 과도한 응력을 저감시키기 위한 다양한 보강재 형식의 효율성을 수치해석적으로 평가하였다. A fish-bone type bridge is vulnerable to the torsional behavior due to the single girder system with planar zigzag conformation. The fixed connecting area between the girder and pier is the special weak point because the torsional load creates excessive stress concentration. Therefore, the method to reduce the stress concentration is required. In this study, the reduction efficiency of various reinforcing types to reduce the excessive stress occurring at the connecting area is evaluated by using numerical analyses.

Effects of slip on eccentrically loaded multiple-ply girder timber trusses

Recent roof failures in South Africa, of multiple ply nail plated trusses, have necessitated a rethink about the way in which timber trusses are analysed. The authors believe that the relative slip between plies caused by a torsional moment as a result of eccentric loading is a possible reason for some of the failures. The design assumption in South Africa and America is that all the plies share the applied load equally; Eurocode 5 (BS EN 1995-1-1:2004) does not cover the design of multiple ply trusses; and BS 5268-3:2006 recommends additional load factors to be applied to eccentrically loaded truss components with the outer ply being loaded more than the inner plies, as a result of the torsion induced by an out-of-plane eccentricity. In this paper, a matrix stiffness method is used to show that, by ignoring the eccentric loading and relative slip between the trusses, the member and plate force may be underestimated by a factor in excess of two for a three ply girder truss. A single three-ply girder truss test is used to illustrate the merits of the method. The required load factors calculated also show that the magnification factors in BS 5268-3:2006 are lower than they should be.

Experimental Study on Structural Behavior of Precast PSC Curved Girder Bridge

교통수요의 증가에 따른 교통혼잡을 피하기 위하여 고가도로와 고속도로, 경전철 등이 활발히 건설되고 있으며, 이에 따라 접속부 등과 같은 곡률반경이 작은 곡선교 구간의 발생이 증가하고 있다. 초기에는 직선형의 주형을 연결하여 곡선을 이루는 방법을 사용하였으나, 공사비의 증가와 미관성 측면에서 용이하지 않아 강재를 사용한 곡선주형이 개발되어 적용되고 있다. 강재의 특성상 기하학적인 형상을 구현하는데 상대적으로 손쉽기 때문에 대부분의 곡선교에서는 강재를 이용한 강박스 거더교를 주로 사용하고 있다. 그러나 강박스 거더교는 초기 공사비가 고가이고, 도장과 같은 지속적인 유지관리가 필요한 문제점을 가지고 있다. 최근에는 I형 강재 플레이트 거더를 사용하는 방법이 활발히 연구되고 있으나 곡선 I형상의 특성상 개단면이고 얇은 플레이트를 사용하기 때문에 비틀림 강성이 매우 작아 안전성에 문제가 있는 것으로 지적되고 있다. 이러한 곡선강교의 대안으로 경제성과 안전성이 확보되는 프리캐스트 PSC 곡선거더가 제시되고 있다. 이에 본 연구에서는 프리캐스트 PSC 곡선거더를 효율적으로 제작할 수 있는 스마트 몰드 시스템을 개발하고 이를 적용한 2주형 40m 실물교량의 정적 휨 파괴 실험을 통하여 안전성을 확인하고자 한다. 제작단계에서 단일 거더는 곡률반경에 의해 거더의 전도에 대한 안정성이 문제가 있으나 가로보로 연결된 멀티거더는 하중분배가 적절히 이루어지며 안정성이 확보되는 것으로 나타났다. 정적구조 실험결과에서는 균열하중(1,400 kN)이 설계하중(450 kN)의 약 3배 이상 높은 것으로 나타났으며, 허용처짐량에 해당하는 하중은 설계하중의 4배인 1,800 kN에서 발생하여 사용성과 안전성이 모두 확보되는 것으로 나타났다. Recently, many overpasses, highway, and advanced transit systems have been constructed to distribute the traffic congestion, thus small size of curved bridges with small curvature such as ramp structures have been increasing. Many of early curved bridges had been constructed by using straight beams with curved slabs, but curved steel beams have replaced them due to the cost, aesthetic and the advantage in building the section form and manipulating the curvature of beams, thereby large portion of curved bridges were applied with steel box girders. However, steel box girder bridges needs comparatively high initial costs and continuous maintenance such as repainting, which is the one of the reason for increasing the cost. Moreover, I-type steel plate girder which is being studied by many researchers recently, seem to have problems in stability due to the low torsional stiffness, resulting from the section characteristics with thin plate used for web and open section forms. Therefore, in recent studies, researchers have proposed curved precast PSC girders with low cost and could secured safety which could replace the curved steel girder type bridges. Hence, this study developed a Smart Mold system to manufacture efficient curved precast PSC girders. And by using this mold system a 40 m 2-girder bridge was constructed for a static flexural test, to evaluate the safety and performance under ultimate load. At the manufacturing stage, each single girder showed problems in the stability due to the torsional moment, but after the girders were connected by cross beams and decks, the bridge successfully distributed the stress, thereby the stability was confirmed. The static loading test results show that the initial crack was observed at 1,400 kN when the design load was 450 kN, and the load at the allowable deflection by code was 1,800 kN, which shows that the safety and usability of the curved precast PSC bridge manufactured by Smart Mold system is secured.

Double Girder Bridge Crane with Double Cycling: Scheduling Strategy and Performance Evaluation

This paper introduces a novel quay crane design, double girder bridge crane (DGBC). DGBC is capable of handling containers of two adjacent bays simultaneously, avoiding crane collisions, saving travelling and reposition cost, and eventually improving terminal efficiency. This problem is formulated as a resource-constrained project scheduling with objective to minimize the maximum completion time. A two-stage heuristic algorithm is proposed in which an operating sequences on each bay is obtained by double cycling, and the integrated timetable for both bays is constructed by solving resource conflicts using the proposed minimum cost strategy. We examine effectiveness and performance of applying DGBC with double cycling. A case study is presented to illustrate how DGBC works with the two-stage method. Three extreme cases with respective conflict types are investigated to develop the performance bounds of DGBC with double cycling. The results show that DGBC can significantly improve terminal productivity, and outperforms single girder crane in both makespan and the lift operation percentage. The highest DGBC efficiency does not require maximum double cycles in two bay schedules; rather the integrated timetable for two bays is the main contribution to the DGBC performance as it yields better cooperation between two spreaders and the driver.

사인형 주름웨브보의 이산화 최적구조설계

박스형 거더나 박공형 철골조 프레임에서 주름웨브보의 사용은 최근 많이 늘어가고 있다. 그 이유는 얇은 주름웨브보를 사용함으로서 압연형강이나 용접을 이용한 조립보에 비해 중량을 크게 줄일 수 있으며, 박판의 좌굴은 주름이 막아줄 수 있기 때문이다. 자동생산기술의 향상으로 인해 주름웨브를 가진 단위 부재를 양산할 수 있게 되어 적용분야가 확장되고 있으며, 주름웨브보의 부재 제원을 고려한 최적설계의 구현이 필요하게 된다. 이를 위해 본 논문에서는 주름웨브보의 생산부재 데이터를 고려한 이산화 최적구조설계 프로그램을 개발하여 집중하중과 등분포하중을 받는 주름웨브 단순보에 대해 적용하였다. 최소중량을 목적함수로, 세장비, 응력 및 처짐을 제약조건으로 채택하고, 전역최소값을 탐색하기 위해서 유전자 알고리즘을 채택하였으며, 생산부재의 번호를 불연속설계변수로 이용하였다. 최종적으로 해석설계의 검증을 위해서 이산화 최적설계 결과를 연속일 때의 결과와 비교하였으며, 최적단면 특성에 대해 분석하였다. The use of sinusoidal corrugated web girder for the box-type girders and gable steel main frames has recently been increasing very much. The reasons are that the thin web of the girder affords a significant weight reduction compared with rolled beam and welded built-up girder, and that corrugation prevents the buckling failure of the web. Improvements of the automatic fabrication process makes mass production of the corrugated web and unit possible, and applications of this girder have been extended considerably. Thus, the research for the optimum design processer considering the production data is needed practically. For doing this research, we develope the discrete optimum structural design program in consideration of production list data for the research, and the program apply to the single girder under the uniform load and the concentrated load as numerical example. We consider objective function as minimum weight of the girder, and use slenderness ratio, stress of flanges and corrugated web, and the girder deflection as the constraint functions. And also the Genetic Algorithms is adopted to search the global minimum point by using the production list as a discrete design variable. Finally, to verify the optimality of the design, we conduct a comparison of the results of the discrete optimum design with those of the continuous one, and also analyze the characteristics of the optimum cross-section.

Designing Simply Supported R.C. Bridge Decks Subjected to In-Plane Actions: Strut-and-Tie Model Approach

The evaluation of the effects of seismic action on the decks of multi-girder bridges is often neglected by practitioners because it is thought that seismic code prescriptions (i.e., deck elastic behavior and minimum reinforcement) in addition to ultimate limit state reinforcement dimensioning for permanent and variable load, do not justify more accurate analyses aimed at checking and/or optimizing reinforcement layout. With the aim of verifying the reliability of this kind of approach, this article proposes a step-by-step procedure, based on the Strut-and-Tie Model, for the design of R.C. girder bridge decks subjected to in-plane seismic actions. As a first application, the proposed approach is used for a single span girder bridge deck. The influence on the model of geometry and supports of the bridge deck as well as the layout of girders and cross-beams is also investigated.