Transverse Load Distribution Research Articles

Live Load Testing of NEXT-D Bridges to Determine Distribution Factors for Moment

AbstractLive load tests were conducted on an in-service bridge containing decked Northeast Extreme Tee (NEXT-D) girders. The purpose of the tests was to evaluate transverse load distribution and to...

Transverse distribution of concentrated loads in timber–concrete floors: Parametric study

Furniture and partition walls are commonly imposed loads on building floors. At the design stage, such concentrated loads are usually associated with the beam over which they are applied, disregarding the possibility of transversal distribution in slab-type structures. This article presents a comprehensive numerical study aimed at understanding the parameters that mostly affect the transverse load distribution for point and line loads on timber–concrete floors. A set of parameters that might affect the behaviour of these composite floors was formed and their limits of variation were established. Using a numerical model developed and validated by the authors, several modelling tasks were performed and the results, in terms of vertical displacements, support reactions and longitudinal bending moments, were analysed. The span, the concrete thickness and the structural system were found to be the parameters with a higher effect on the manner in which load is transversally distributed through floor beams. Also, the ‘degree of oversizing’ of timber sections should be taken into account when designing this type of composite floor, given its influence on the load distribution.

Design and field evaluation of a hybrid FRP composite – Lightweight concrete road bridge

The innovative hybrid idea of a FRP composite – lightweight concrete structural system for vehicular bridges has been proposed. Due to the lack of commonly accepted design procedures, the whole designing process was based on FEA and strongly supported by testing. Also, the result – a demonstrative vehicular bridge – was the subject of investigation focused on evaluating the bridge performance under proof load. A prototype hybrid structure with the span length of 21.0 m was subjected to a series of static and dynamic loading tests. The results obtained from the investigation were used to verify the applied design procedure by determining the key behaviour characteristics: stiffness, strength, load transverse distribution, degree of composite action, and dynamic performance and comparing them with design predictions. Linear FEA was found to predict accurately the flexural behaviour of hybrid bridge systems in the elastic range. With respect to the static and dynamic performance, the novel hybrid bridge system fully conformed to design requirements of relevant standards. However, the field test results indicated that the design assumptions seem to be conservative because a significant margin of safety was revealed, particularly in terms of FRP strength. Therefore, some implications of field evaluation results for future designs of hybrid FRP-concrete bridges have been presented in the paper.

Vehicle weight identification for a bridge with multi-T-girders based on load transverse distribution coefficient

It is still an issue to identify the vehicle weight for bridges with multi-T-girders which is essential in bridge operation management. In this study, a vehicle weight identification method is proposed for bridges with multi-T-girders. To consider the load transverse distribution effect, first the separation variable method is adopted to separate the spatial influence surface function of vehicle load into the product of two single-valued functions. Then the procedures of the vehicle weight identification method are proposed using the measured strain responses of the T-girders caused by the passing vehicle accordingly. A numerical example of a bridge with five T-girders and an experimental example of a bridge with two T-girders are conducted to verify the feasibility and effectiveness of the proposed method. Furthermore, the performance of the proposed method is compared with the typical existing method in which the load transverse distribution effect is not considered.

Ritz variational method for bending of rectangular kirchhoff plate under transverse hydrostatic load distribution

Ritz variational method for bending of rectangular kirchhoff plate under transverse hydrostatic load distribution

Experimental Verification of Concentrated Load Transverse Distribution in Shear

An ability of reinforced concrete slabs to distribute concentrated load in transverse direction is an important property for their verification. Several methods for the assessment of transverse distribution (effective width) were proposed but they were not incorporated in the current standards. This paper deals with an experimental analysis of the effective width for shear verification of slabs subjected to concentrated load. Shear resistance of the slab specimens subjected to concentrated load obtained from tests has been compared with resistance of the slab strips loaded by uniform shear. Based on this check, the effective width has been evaluated. Experimental results were also compared with results of models introduced in relevant standards.

A Study on Calculation Theory and Method of Transverse Distribution Coefficient of the Corrugated Steel Web Box Girder Based on the "Modified Rigid Jointed Beam Method"

Abstract: The PC box girder Bridge with corrugated steel web, as a new kind of bridge structure, has different mechanical properties from that of the ordinary concrete box girder bridge. Due to the late development of the corrugated steel web pre-stressed box girder structure, the domestic experts have made little research on the transverse load distribution of PC box Girder Bridge with corrugated steel webs. Whether the method of calculating the transverse distribution coefficient in the classical box girder theory can be applied to the corrugated steel web composite box girder and how to further improve the calculation theory and method of the transverse load distribution of the steel box girder bridge need urther study. method of the transverse load distribution of the steel box girder bridge need further study.Based on the "traditional rigid jointed process and the programming ideas of the transverse distribution coefficient of corrugated steel web composite box girder of the "modified rigid jointed beam method".beam method" and the existing research, this paper proposes the "modified rigid-jointed beam method" in combination with the specific internal force distribution of corrugated steel web composite box girder. The computational scheme and formula of mechanics, the calculation process and the programming ideas of the transverse distribution coefficient of corrugated steel web composite box girder of the "modified rigid jointed beam method".

Effect of sensor system noise and load positioning on the precision of load testing and rating of highway bridges: a case study

This paper discusses the load testing of a three-span simply supported multi-girder/stringer bridge superstructure in northern New York. The first part of the testing deployed a custom developed wireless sensor system (WSS) measuring high-rate real-time strain measurements on all three spans of the steel superstructure. Controlled progressive damage was introduced to one of the three spans for the second part of testing where the span was monitored using wired strain transducers mounted at the top and bottom flanges of each girder at midspan. A single test vehicle was used to apply prescribed loads to the structure to acquire estimates of neutral axis (NA) and transverse load distribution factors (DF), two common parameters typically measured for a load rating. A sensitivity analysis was conducted using the peak-to-peak noise in the measurement signals. As expected, the farther the axle loads were positioned from the measured girder, the lower the measurement signal. In certain cases, this produced significant uncertainty in the NA measurement. On the other hand, the peak-to-peak noise did not appear to affect the DF estimates. This data was combined to illustrate the variation in the overall inventory and allowable stress design (ASD) load rating of the steel superstructure.

The rescue of small rolled beams embedded in concrete bridge in Germany

Iron sections embedded in concrete have been known from the beginning of the nineteenth century. This technology has been widely applied ever since and has proven to be a reliable technique for bridges with small spans. Nevertheless, the consideration of the bond between steel and concrete and the transverse load distribution of such structures has remained a broadly discussed topic among engineers. Demolition of a small German road bridge constructed in 1949 with this method was looming, as a conventional reassessment failed to provide the required load-bearing capacity. In an effort to save this historic bridge, the actual structural behaviour of the bridge was investigated by in situ testing. Displacement transducers and strain gauges mounted on selected steel beams recorded the behaviour during the application of static as well as travelling loads. Based on these results, the model for the transversal load distribution could be revised; thus, the bridge fulfilled the requirements after all.

Rozdział poprzeczny obciążeń ruchomych w belkowo-płytowym moście drogowym z dźwigarami kompozytowymi FRP

The paper presents an analysis of the parameters of live load transverse distribution in the span of a road bridge that is made of four box FRP composite girders and a composite deck slab made of lightweight concrete. The parameters were determined experimentally and computationally using the orthotropic plate model included in the Cusens-Pam solution and also the numerical FEM model. The measured values of load transverse distribution factors and influence lines were determined during bridge load testing. A comparison of the measured and calculated load transverse distribution factors is shown on the basis of the analysis of the girders' deflection in their cross-section in the middle of the bridge span. As a result of this comparison, it was proved that the analytical model of the orthotropic plate and also the numerical shell-solid FEM model have a high compliance of load transverse distribution with the distribution obtained from the measurements. In addition, computational analysis and tests showed a sufficient flexural rigidity and high torsional rigidity of the bridge span (the bridge construction belongs to a group of structures with a low overall rigidity of k = 300 kN/mm), confirming that the FRP composite girders that were used for its construction can be an alternative to the concrete and steel girders that are commonly used in the construction of bridges.

Analysis of load test on composite I-girder bridge

This paper showcases the importance of field testing in efforts to deal with the deteriorating infrastructure. It shows that when tested, bridges do not necessarily behave as expected under load, particularly with respect to boundary conditions. This is demonstrated via a load test performed on a healthy but ageing composite reinforced concrete bridge in Exeter, UK. The bridge girders were instrumented with strain transducers and static strains were recorded while a four-axle, 32 tonne lorry remained stationary in a single lane. Subsequently, a 3-D finite element model of the bridge was developed and calibrated based on the field test data. The bridge deck was originally designed as simply supported, however, it is shown (from the field test and calibrated model) that the support conditions were no longer behaving as pin-roller which affects the load distribution characteristics of the superstructure. Transverse load distribution factors (DFs) of the bridge deck structure were studied for different boundary conditions. The DFs obtained from analysis were compared with DFs provided in Design Manual for Roads and Bridges (DMRB) Standard Specification. Having observed in the load test that the ends of the deck appeared to be experiencing some rotational restraint, a parametric study was carried out to calculate mid-span bending moment (under DMRB assessment loading) for varying levels of restraint at the end of the deck.

Transverse distribution of internal forces in timber–concrete floors under external point and line loads

Some aspects of the structural behaviour timber–concrete floors are still not fully known. This is the case of transverse load distribution for point and line loads. This article presents a study on timber–concrete floors subjected to point and line loads.A set of composite floors, each comprising five beams, was tested in order to evaluate how some parameters might affect the load distribution. These results were compared to those obtained with a numerical model developed by the authors.Typically, the beam underneath the load takes the highest percentage of the applied load and the distribution for the remaining beams is significantly affected by the span. For composite slabs with medium spans (L=4.00m), when the load is applied at the central beam midspan only 37% of the load is received by this beam, with 69% of the load being carried by the composite T-beams adjacent to the middle one and the remaining share (about −6%) resulting from the relieving in the load received by the outer beams.

Evaluation of Torsional Stiffness in Beam and Slab Bridge Decks Based on Load Testing

In this paper, evaluation of torsional stiffness in beam and slab bridge deck elements is presented. A beam and slab bridge decks structurally behave as a grillage. A grillage has an efficient transverse load distribution due to transverse asymmetric load. In the case of bridge deck without transverse beams in the span, transverse load distribution depends on the torsional stiffness of longitudinal beams, transverse beams over the. supports and deck slab. The results of load testing conducted on series of bridges in Croatia is compared with results obtained on different numerical grillage models in which torsional stiffness of main structural elements was varied. Five different numerical models for each tested bridge is used. To evaluate torsional stiffness of main structural elements of the bridge the transverse distribution coefficients are introduced. The design value of the coefficients of torsional stiffness reduction for verification of the serviceability limit state (SLS), with assumption of normal probability distribution is determined. The same coefficient is calculated using recommendation for torsional stiffness reduction in concrete elements defined by Model code CEB-FIB 1990 (MC 90). According to conducted analyses the design value of the coefficient of torsional stiffness reduction for verification of the serviceability limit state of main structural elements of beam and slab bridge deck is proposed.

Development and study of deck joints in prefabricated concrete bulb-tee bridge girders: Experimental evaluation

This paper presents a new bridge deck slab flange-to-flange connection system for precast Deck Bulb Tee (DBT) girders. In prefabricated bridge system made of DBT girders, the concrete deck slab is cast with the prestressed girder in a controlled environment at the fabrication facility and then shipped to the bridge site. This system requires that the individual prefabricated girders to be connected through their flanges in order to make it continuous for transverse live load distribution among girders. Two types of moment-transferring connection and two types of intermittent-bolted connection, besides one moment-transferring connection provided by lateral restraints to girder rotation, were developed. Five actual-size bridge panels were fabricated and then tested up-to-collapse to qualify these joints for use in acceleration bridge construction. The effect of the detailing of the moment-transferred connection along with the level of the fixity of the connecting steel plates of intermittent-bolted connection were examined. The developed joint was considered successful if the experimental wheel load satisfied the requirements specified in North American Bridge Codes. It was concluded that the type and detailing of the deck slab joint affected the ultimate load carrying capacity of the developed connections. The successful connection systems can be used by bridge engineers in order to design bulb-tee girder system to accelerate bridge construction.

Test Study of Transverse Prestressed Tendons (TPTS) on the Mechanical Performance of Hollow Slab Bridge

Structural defects and heavy traffic make the hollow slab bridge serious diseases, such as “Single Beam Bearing”. Transverse prestressed tendons (TPTS for short) is an effective methods to solve this problem. A detailed test study of hollow slab bridge modeled by plexiglass with TPTS is done in this article. The analysis parameters include the TPTS’ layout and the value of prestress. The test results show that TPTS can effectively even the transverse load distribution, and improve the integrity of bridges.

Transverse Distribution Calculation and Analysis of Strengthened Yingjing Bridge

Box-girder has been adopted to strengthen bridge as large border girder, in which the original girders can be unloaded with box-girder bearing most loads. However, the load transverse distribution calculation method for it is still imperfect thus a modified calculation method is specially proposed to calculate the load transverse distribution in this case basing on existed methods. An engineering example is introduced to describe the calculation process and corresponding FEM model is established to validate the feasibility and applicability of this calculation method. Besides, comparisons between the load transverse distribution before and after strengthened are conducted which further proves that adding box-girder to the original bridge is an effective strengthening way.

Numerical Analysis on Changing Regularity of Transverse Load Distributions with Different Crack Lengthens of Plate-Girder Hinge Joint

The finite element software ABAQUS is used to analyze the influence of hinge joint crack on transverse load distribution of prefabricated concrete hollow core slab bridge, including single-side crack and two-side crack. The relationship between hinge joint crack length and load transverse distribution was built by using the Regression Analysis. Equivalent Area Method was adopted to bring out the critical crack length. The paper introduced a correlative method to illustrate single plate phenomenon and suggested the critical hinge joint crack lengthens for prefabricated concrete hollow slab bridge, which provided a technical basis for the quantitative assessment of single plate phenomenon in the technical inspection practice of bridges. In the end, critical crack lengths of hinge joint were determined based on a criterion of the “Single Plate Load Effect”, that is, the critical crack length of single-side crack is 100% of the total span length of the bridge, while that of the two-side cracks is 67%. This result will lead to further research on the failure mechanics of prefabricated hollow core concrete slab beam bridges and their retrofit techniques.

Effects of Transverse Prestressed Tendons (TPTS) on the Mechanical Performance of Hollow Slab Bridge

There are some common diseases occurred on hollow slab bridge often, such as large deflections and Single Beam Bearing caused by insufficient strength of hinge joints, and so on. Transverse prestressed tendons (TPTS for short) is an effective methods to solve the above diseases. A detailed analysis of hollow slab bridge with TPTS is done by FEM in this article. The analysis parameters include the TPTS layout and the value of prestress. The results show that the TPTS can effectively even the transverse load distribution, and improve the integrity of bridges.

Recommendations for the Shear Assessment of Reinforced Concrete Slab Bridges from Experiments

Upon assessment of existing reinforced concrete short-span solid slab bridges according to the recently implemented Eurocodes that include more conservative shear capacity provisions and heavier axle loads, a number of these structures were found to be shear-critical. The results from recent experimental research on the shear capacity of slabs indicate that slabs benefit from transverse load distribution. Recommendations for the assessment of solid slab bridges in shear are developed on the basis of these experiments. A load spreading method for the concentrated loads is proposed and the applicability of superposition of loading is studied. The resulting most unfavourable position for the design trucks is provided and implemented in the so-called Dutch “Quick Scan” method (QSEC2). Cases of existing bridges are studied with the previously used QS-VBC as well as with the QS-EC2 that includes the recommendations. As a result of the assumed transverse load distribution, the shear stress to be considered at the support based on the recommendations becomes smaller.

Calculation of Bridge Transverse Load Distribution Coefficient Based on Generalized Rigid Cross-Beam Method

Rigid cross-beam method is one of the most widely used calculation strategy for bridge transverse load distribution coefficient, which is based on grillage theory. However, the shear deformation of the main girder and the difference of transverse load distribution in longitudinal direction are ignored in the calculation process. In this paper, a generalized rigid cross-beam method are proposed based on the displacement beam theory and torsion theory of thin-walled bars, which can take account of the influence of shearing deformation, the difference of the transverse load distribution in longitudinal direction, and torsional behavior of the beam. Numerical simulation demonstrated that the proposed method possesses favorable accuracy and applicability.