Load Of Girders Research Articles

The effectiveness of CFRP strengthening of steel plate girders with web opening subjected to shear

The present study is experimental by nature; it involves applying shear buckling test on seven steel-plated girders that are subjected to shear loading. Four of these girders represent the strengthened girders whereas the other three are reference girders. One of the latter type of girders has a square web opening; the second has a diamond web opening while the last one has no opening at all. The webs of the strengthened girders were adhesively attached to CFRP sheets of different patterns. This step was carried out to evaluate the most effective strengthening scheme by CFRP composite. The study aims at examining the effect of several parameters on the behavior of web girders. It further examines the percentage of increase in the ultimate shear capacity of the perforated girders that have a fixed location and size where the latter is equal to 40 percent of the web depth. Results have shown that, first, the ultimate shear load of the CFRP-strengthened girders with square web opening is higher than that of the reference girder with a square web opening; ranging from 8.7% to 15.7%. The obtained ranges depend on the orientation of the CFRP strips. Second, the ultimate shear load of the CFRP-strengthened girders with a diamond web opening is higher than the reference girder with a range of 9.8% to 21.5%. Again, the obtained ranges depend on the orientation of the CFRP strips. Analytically speaking, Von Mises stresses have been used to predict the ultimate shear load of girders with square and diamond web openings and without web opening.

Elastična kritična sila ploča i limenih nosača pod dejstvom lokalizovanog opterećenja

The determination of the elastic critical load (buckling load) is an important element of the assessment of the ultimate load of plate girders according to Eurocode 3 for design of steel structures. An analysis of the critical load of a plate corresponding to the web of an I-girder for different boundary conditions and the critical load of the I-girder itself subjected to patch load is given in the paper. Conclusions regarding their correspondence are given. Also, experimentally determined ultimate loads of I-girders are compared with predictive values according to Eurocode 3 for the models used in this analysis. A modified procedure for the ultimate load determination is proposed by following the Eurocode 3 algorithm and changing only buckling coefficient. In order to improve the ultimate load prediction, it is suggested to calculate the buckling coefficient also as a function of patch load length.

멤브레인형 LNG선박의 리퀴드 돔 체어 구조개발

A membrane type LNG cargo tank is equipped with a pump tower and a liquid dome for loading and unloading of LNG. However, the membrane running continuously on the tank wall to prevent leakage of LNG is interrupted by the liquid dome, hence care should be taken in the design of liquid dome and its substructures. In case of GTT NO96 membrane type cargo containment system, chair structure is arranged along the periphery of the liquid dome targeting to support the membrane which is exposed to the both hull girder and thermal load. This paper proposes a new and simple chair structure, which outperforms traditional design from productivity point of view maintaining same level of structural safety. Strength assessment on the new design was performed to guarantee the structural safety of the new design, which includes strength, fatigue and crack propagation analysis.

Parametric study on buffeting performance of a long-span triple-tower suspension bridge

The triple-tower suspension bridge is a brand new type of structural form that is equipped with a dominant mid-tower. The dynamic characteristics of this multiple main-span suspension bridge present a significant difference with that of the conventional single main-span suspension bridge. Hence, taking the Taizhou Yangtze River Bridge as an example, the buffeting performance of a long-span triple-tower suspension bridge under strong winds is comprehensively investigated via finite element method. Specifically, the sensitivity of structural buffeting performance to some major structural parameters, aerodynamic parameters as well as parameters of turbulence inputs is analysed in time domain. It was found that the structural buffeting performance heavily depends on the dead load of the main girder, sag-to-span ratio of the main cable, longitudinal stiffness and structural type of the mid-tower. Also, appropriate selection of aerodynamic admittance function, power spectrum model of fluctuating wind and the spatial coherence coefficient is important in the buffeting analysis. Besides, the self-excited forces have small impact on the calculation of buffeting responses of such a bridge. The analytical results can provide references for the buffeting analyses and wind-resistant design of similar long-span triple-tower suspension bridges.

Load and deflection recovery capacities of PSC girder with unbonded PS H-type steel

Load and deflection recovery capacities of PSC girder with unbonded PS H-type steel

Barrier Effect on Transverse Load Distribution for Prestressed Concrete Segmental Box Girder Bridges

AbstractBarriers are purposely omitted from the structural analysis for bridge design or load rating. They are not considered as primary structural members because, after a forceful collision, they may sustain some structural damage and would no longer strengthen the bridge deck. However, when completely intact, these secondary structural members do affect the distribution of applied loads, which is of interest to permitting agencies, such as the Florida Department of Transportation (FDOT). For a prestressed concrete segmental box girder bridge, both design and load rating (for oversized load permits) are determined by longitudinal and transverse analyses without considering the influence of the barriers. For the transverse analysis, the maximum moment generated from the live load is traditionally calculated from Homberg charts. These influence surfaces are based on plate behavior and idealized support conditions and are generally conservative. This moment estimation and the lack of consideration for the ...

Design safety margin of a 10,000 TEU container ship through ultimate hull girder load combination analysis

Assessment of the ultimate longitudinal strength of hull girders under combined waveloads can be of particular importance especially for ships with large deck openings and low torsional rigidity. In such cases the horizontal and torsional moments may approach or exceed the vertical bending moment when a vessel progresses in oblique seas. This paper presents a direct calculation methodology for the evaluation of the ultimate strength of a 10,000 TEU container ship by considering the combined effects of structural non-linearities and steady state wave induced dynamic loads on a mid ship section cargo hold. The strength is evaluated deterministically using non-linear nite element analysis. The design extreme values of principal global wave-induced load components and their combinations in irregular seaways are predicted using a cross-spectral method together with short-term and long-term statistical formulations. Consequently, the margin of safety between the ultimate capacity and the maximum expected moment is established.

Experimental and numerical investigations on plate girders with perforated web under axial compression and bending moment

While plate girders with perforated web are commonly used in ships, aircraft applications for their high efficiency. In spite of numerous papers in the literatures on plate girders with perforated web subjected to web crippling, the ultimate capacity load of plate girders with perforated web subjected to plate buckling has not been exhaustively examined. In this study, experimental and numerical studies are performed to investigate the failure behavior of plate girders with perforated web under axial compression and bending moment, which is the typical action pattern arising from cargo weight and water pressure together with hull girder motions in ships and ship-shaped offshore structures. Six specimens with one oval hole are tested to investigate the failure modes and ultimate load capacities of plate girders with perforated web. Test results show that computational model can predict the failure behavior of plate girders with perforated web, and an extensive numerical study is conducted to investigate the influence of hole location. It showed that hole location have more influence on ultimate capacity load of plate girders when hole close to the middle of the web, particularly. Based on the experimental and numerical investigations, an influence curve is proposed to account for effects of hole location.

A new predictive model for restrained distortional buckling strength of half-through bridge girders using artificial neural network

Half-through girders are not affected by conventional lateral-torsional buckling. I-section beams of simply supported half-through girders experience compression in their top flanges and tension in their bottom flanges. In this condition, the compression flange is restrained only by the stiffness of the web, and the buckling mode is generally restrained distortional. In this study, new and efficient model is derived to predict the Restrained Distortional Buckling (RDB) strength of half-through I-section bridge girders utilizing an Artificial Neural Network (ANN). The model is developed based on a reliable database obtained from the nonlinear finite element (FE) method. To verify the accuracy of the derived model, it is applied to estimate the RDB strength of parts of the FE analysis results that were not included in the modeling process. A sensitivity analysis has been also developed to determine the importance of each input parameters. ANN model is further compared to the some existing design codes. The results indicate that the proposed model is effectively capable of evaluating the RDB load of the half-through girders. The prediction performance of the ANN model is markedly better than prediction of the AISC/LRFD and the AS4100 specifications. The ANN-based design equation can reliably be employed for pre-design applications.

식재기반을 담는 RDT 거더교의 구조성능 검증

RDT(Reversed Double T) 거더교는 생태교 맞춤형으로 개발된 PSC 교량 형식이다. 모음 ㅛ형상과 유사한 단면형상이 가장 큰 특징이며 거더 내부 공간에 흙을 담을 수 있어 상부 구조 전체 높이를 획기적으로 낮추고 시공성과 경제성이 우수하여 생태교로써 적용이 활발할 것으로 기대되는 공법이다. 새로 제안된 RDT 거더교의 실적용을 위해서는 공용 중 안전성 검증이 필요하다. 본 연구에서는 RDT 거더교의 실물모형 실험체를 설계 및 제작하여 정적재하 실험을 수행하였다. 실험결과와 변형률적합법을 이용한 비선형 해석 결과를 바탕으로 거동을 평가하고 구조성능을 검토하였다. 검토 결과, RDT 거더교는 사용하중의 2배 이상 균열 안전성을 확보하고 있으며 우수한 휨 성능을 보유하고 있는 것으로 나타났다. The proposed RDT(Reversed Double T) girder bridge is suitable to eco corridor, because of its cross section which resembles Korean alphabet vowel "ㅛ". The total height and cost of bridge would be reduced for its inner space containing some of plant soil. In this study, the performance of the RDT girder was assessed by comparing results of static test with those of nonlinear analysis. The cracking load of the RDT girder was evaluated more than two times of design load.

Parameter sensitivity study on flutter stability of a long-span triple-tower suspension bridge

The flutter instability is the most hazardous wind-induced vibration for the long-span suspension bridge. In this study, the first-built long-span triple-tower suspension bridge in China, the Taizhou Yangtze River Bridge, is taken as an example. The three-dimensional flutter stability analysis of the bridge is conducted based on ANSYS, and the parametric analysis on the structural flutter stability is performed. The parameters studied in this paper include the sag-to-span ratio, the stiffness of the main girder, the dead load of the main girder, the rigid central buckle, the longitudinal stiffness of the middle tower and the cable system. The result shows that the torsional stiffness of the main girder, the sag-to-span ratio of cables, the central buckle and the cable system has significant influence on the flutter stability of the bridge. Among the sensitive parameters found in this paper, the influence of the cable system is prominent. However, the influences of the stiffness of the main girder, the longitudinal stiffness of the middle tower and the dead load of the deck are limited. The results can provide the reference information for wind resistance design of long-span triple-tower suspension bridges in the future.

Parametric Analysis on Incrementally Launched Construction for Concrete Box Girder

The structural behavior of incrementally launched bridges in the construction stages depends on different parameters. Internal force of main girder is influenced by the dead load and stiffness of main girder, the length and stiffness of launching nose. Parametric analysis on the effect of internal force of an 8×60m-span concrete continuous box girder bridge was carried out. The results show that bending moment increases following the increase of weight and stiffness of corresponding segment of main girder. The phenomenon is even more obvious in the negative bending moment region of main girder segment nearby the launching nose. The bending moment of main girder reduces significantly when the stiffness ratio among launching nose and main girder is less than 0.15. While, the negative bending moment of main girder reduces significantly when the length ratio among launching nose and main span is more than 0.58.

A practical method to apply hull girder sectional loads to full-ship 3D finite-element models using quadratic programming

Interest in the seakeeping loads of vessels has increased dramatically in recent years. While many studies focused on predicting seakeeping loads, little attention was given on how loads are transferred to 3D finite-element models. In current design practice, methods for predicting seakeeping motions and loads are mainly based on the potential flow theory, either strip theory methods or 3D-panel methods. Methods based on strip theory provide reasonable motion prediction for ships and are computationally efficient. However, the load outputs of strip theories are only hull girder sectional forces and moments, such as vertical bending moment and vertical shear force, which cannot be directly applied to a 3D finite-element structural model. Methods-based 3D panel methods can be applied to a wide range of structures, but are computationally expensive. The seakeeping load outputs of panel methods include not only the global hull girder loads, but also panel pressures, which are well suited for 3D finite-element analysis. However, because the panel-based methods are computationally expensive, meshes used for hydrodynamic analyses are usually coarser than the mesh used for structural finite-element analyses. When pressure loads are mapped from one mesh to another, a small discrepancy at the element level will occur regardless of what interpolation method is used. The integration of those small pressure discrepancies along the whole ship inevitably causes an imbalanced structural finite-element model. To obtain equilibrium of an imbalanced structural model, a common practice is to use the ‘inertia relief’ approach. However, this type of balancing causes a change in the hull girder load distribution, which in turn could cause inaccuracies in an extreme load analysis (ELA) and a spectral fatigue analysis (SFA). This paper presents a practical method to balance the structural model without using inertia relief. The method uses quadratic programming to calculate equivalent nodal forces such that the resulting hull girder sectional loads match those calculated by seakeeping analyses, either by strip theory methods or 3D-panel methods. To validate the method, a 3D panel linear code, MAESTRO-Wave, was used to generate both panel pressures and sectional loads. A model is first loaded by a 3D-panel pressure distribution with a perfect equilibrium. The model is then loaded with only the accelerations and sectional forces and moments. The sectional forces and moments are converted to finite-element nodal forces using the proposed quadratic programming method. For these two load cases, the paper compares the hull girder loads, the hull deflection and the stresses, and the accuracy proves the validity of this new method.

Nonlinear Analysis on the Anchor Board of the Cable-Girder Anchorage Zone of a Cable-Stayed Bridge

The cable-girder anchorage zone of cable-stayed bridge is vital to the safety of the entire structure. Aiming at uniformly conveying the vehicle and populaiton load as well as the load of the main girder to the cables, this zone shows unique characters with concentrated and massive loads, complex structures, comprehensive load paths and non-uniformly stress distributions. This paper established the 3D finite element modal for the Ronggui Cable-Stayed Bridge. A nonlinear analysis on its anchorage zone has been conducted to provide reasonable references for future design and optimization.

Research on the Fatigue Design Load of Orthotropic Steel Box Girder for Long Span Suspension Bridge

Traffic composition and the vehicle load were statistically analyzed and a fatigue vehicle load model was established according to the law of equivalent fatigue damage. Based on the MATLAB programming language and the Statistics Toolbox, vehicle fatigue load spectrum was simulated for accurately assessing actual fatigue stress of existing bridge under traffic loading. And the fatigue load could be used in the design for suspension bridge steel box girder.

Mechanical Behavior of Composite Girder with Perfobond Shear Connector under Hogging Moment

The mechanical behavior of the support regions for continuous composite girders with tensile stresses in the concrete slab and compressive stresses in the lower steel profile becomes strongly nonlinear under negative bending moments. A static test on four half-scale model of a steel and concrete composite girders with different shear connectors including studs and PBL under hogging moments was conducted and observed to evaluate the influence of shear connector on inelastic behavior such as flexural stiffness reduction, crack initiation and development in concrete slab. From the test results, the flexural stiffness and loading capacity of the composite girders were improved by PBL shear connector. Higher initial cracking load and crack resistance stiffness of composite girders with PBL shear connector under serviceability limit state was obtained during crack development process. The test specimen could be assumed as full composite section until the ultimate state from load-slip relationship of shear connector. Analytical and experimental studies can serve as a basis for continuous composite bridges design.

Research on Mechanical Behavior of Reinforced RC Beams Strengthened with Anti-Arch Method

We analyze the mechanical property of strengthening RC beam by using the method of arch pasting with carbon fiber and directly pasting CFRP through numerical simulation and model test. It explains that strengthening RC girder by using the method of arch can solve the influence of beam's loading by the second time which exists in the method of pasting CFRP in strengthening reinforced concrete beams and it can improve the girder's load when it cracks and the carrying capacity; decreasing the deflection deformation and crack width and gap when the girder carries load; It can make the most use of the character of carbon fiber's high strength. The results play very important role of guiding to engineering.

Probabilistic presentation of the total bending moments of FPSOs

The widespread practice for presentation of the still water loads acting on the hull structure of a floating production storage and offloading facility (FPSO) is to use the individual amplitude statistics. When the probability density function of the loads is built, its integration provides the probability of exceeding any given level of loads. Also, once it is available, one can apply the principles of extreme value statistics to obtain the highest value in any number of cycles. The individual amplitude statistics are used in fatigue strength calculations, while the extreme value statistics can be used in ultimate strength calculations. An example is given for the probability density functions of a sample FPSO when the two approaches are applied for assessment of the total hull girder load that can be applied for calculation of its ultimate strength.

Challenges and possible solutions of the time-variant reliability of ship's hull girder

The main theme of the paper centres on the use of probabilistic methods to assess the hull girder bending capacity to be used in a risk-based inspection planning framework. The effect of corrosion wear on hull girder geometric properties is also discussed, and the annual probabilistic distributions and the probabilistic distributions for given time period are built. A new procedure is then proposed for the probabilistic presentation of the still water and wave-induced hull girder hogging and sagging loads as a single phenomenon. Lastly, the rules of the composition law of the constituent variables are used to build the probabilistic distribution of the total hull girder load and the corresponding total hull girder bending stresses. Thus, it becomes possible to calculate the probability of exceeding any given limit of the total hull girder stresses.

Challenges and possible solutions of the time-variant reliability of ship's hull girder

The main theme of the paper centres on the use of probabilistic methods to assess the hull girder bending capacity to be used in a risk-based inspection planning framework. The effect of corrosion wear on hull girder geometric properties is also discussed, and the annual probabilistic distributions and the probabilistic distributions for given time period are built. A new procedure is then proposed for the probabilistic presentation of the still water and wave-induced hull girder hogging and sagging loads as a single phenomenon. Lastly, the rules of the composition law of the constituent variables are used to build the probabilistic distribution of the total hull girder load and the corresponding total hull girder bending stresses. Thus, it becomes possible to calculate the probability of exceeding any given limit of the total hull girder stresses.