In the past, concrete arch bridges were built to cross moderate spans, whereas today the alternative of beam bridges is preferred. In view of their aging, it has become necessary to assess carefully the load-carrying capacity of these... more
In the past, concrete arch bridges were built to cross moderate spans, whereas today the alternative of beam bridges is preferred. In view of their aging, it has become necessary to assess carefully the load-carrying capacity of these historic bridges. In the case of the seriously damaged Pontweg bridge, after inspection in 2012, the general opinion concluded that the bridge should be demolished and replaced. Nevertheless, the arch shape, the characteristic nodes and RC-hangers make this bridge a rare heritage structure. However, careful analysis and testing allowed to convince parties involved, that restoring the load-carrying capacity and refurbishment was possible. Both numerical simulation and dynamic testing have demonstrated the necessity to reinforce substantially the lower chord and the floorbeams. Due to the necessity of rebar splices an additional reinforcing beam was connected to the lower chord. The sealing of the arches and hangers was successful, due to the use of micromortar, whereas an unfortunate polymer-containing repair product of the deck, has modified the texture and appearance of these parts. Fortunately, the arches and hangers have kept most of the concrete colour and texture and show the effort made to preserve the bridge. At present a load test is being considered. Replacing the movable bearings required temporary lifting of one side of the bridge. This demonstrates that an adequate type of repair product is important to preserve the characteristic aspect and texture of historic arch structures.
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Steel truss structures are a powerful and reliable type of bridge girders. The complex part of trusses are the nodes, especially if more than 4 members are converging. Such nodes include internal welds; inaccessible after completion. This... more
Steel truss structures are a powerful and reliable type of bridge girders. The complex part of trusses are the nodes, especially if more than 4 members are converging. Such nodes include internal welds; inaccessible after completion. This study assesses whether all of the internal welds are indispensable, or alternatively, what are the consequences if they are omitted. The latter is tested for a particular bridge, consisting of hollow core profiles. After determining the member forces, including bending moments, an alternative load path is indicated, generated if the internal welds are missing. Formulas are given to determine the weld stresses. In ULS some of the welds require a small amount of strengthening if the internal welds are omitted. In addition fatigue resistance was determined. Certainly for this example internal node welds may be left out, although this does not necessarily apply to more complex node cases. This indicates omitting of some internal welds may well be acceptable
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The railway overpass at Lot was built for the crossing of the high-speed railway line from Brussels to Paris over domestic tracks. The superstructure is an assembled mixed structure, consisting of two main composite girders equipped with... more
The railway overpass at Lot was built for the crossing of the high-speed railway line from Brussels to Paris over domestic tracks. The superstructure is an assembled mixed structure, consisting of two main composite girders equipped with an intermediate reinforced concrete deck plate with transverse stiffening ribs. Steel truss elements were subsequently bolted to the upper flanges of the composite girders. The completed girders were transported from workshops to the building site by train. For fixing the truss elements to the precast girders, geometric compatibility between both components had to be achieved. The deformation of the composite girders could be predicted within certain limits. Due to the use of high performance concrete, the time factor appeared almost insignificant.
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Often insufficient attention is given to the compatibility of the deformations of steel bridges during their assembly on the construction site, especially if continuity, due to bending moments, is to be ensured at the level of... more
Often insufficient attention is given to the compatibility of the deformations of steel bridges during their assembly on the construction site, especially if continuity, due to bending moments, is to be ensured at the level of intermediate supports. This does require to compensate during assembly the difference in the angular rotations at the location of the support points. The effect is especially noticeable with longer spans or with flexible superstructures. In the case of the construction of a double railway bridge over the Albert Canal (Belgium), the above was an important issue. The bridges are in the shape of a classic Warren truss girder. An unusual process was followed for the assembling on site. In the first phase, the entire lower chord, including the bridge deck, was built and supported in all nodes of the truss. The sloping diagonal bars are connected to this and the upper member of the truss is then mounted on top. In such construction the diagonal bars tend to twist and bending moments are created in the lower truss nodes. Gaps may appear in the upper nodes, due to the unequal displacements of the members to be connected. Calculations must show whether stress-free corrections can be made for the fabrication of the various bars, thus avoiding stresses due to the erection process. This example clearly shows that the compatibility of the components of steel bridges during their assembly must be determined in detail and that efficient measures are needed to compensate for defects.
Research Interests: Engineering, Structural Engineering, Report, Deck, Girder, and 4 moreBending Moment, Truss, Diagonal, and Truss bridge
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In the past, concrete arch bridges were built to cross moderate spans, whereas today the alternative of beam bridges is preferred. In view of their aging, it has become necessary to assess carefully the load-carrying capacity of these... more
In the past, concrete arch bridges were built to cross moderate spans, whereas today the alternative of beam bridges is preferred. In view of their aging, it has become necessary to assess carefully the load-carrying capacity of these historic bridges. In the case of the seriously damaged Pontweg bridge, after inspection in 2012, the general opinion concluded that the bridge should be demolished and replaced. Nevertheless, the arch shape, the characteristic nodes and RC-hangers make this bridge a rare heritage structure. However, careful analysis and testing allowed to convince parties involved, that restoring the load-carrying capacity and refurbishment was possible. Both numerical simulation and dynamic testing have demonstrated the necessity to reinforce substantially the lower chord and the floorbeams. Due to the necessity of rebar splices an additional reinforcing beam was connected to the lower chord. The sealing of the arches and hangers was successful, due to the use of micr...
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The connection of tubular members, used as bridge hangers or in 3-D coverings, has been widely researched, both for resistance and for fatigue. Such members are also often used in scaffoldings or as lighter bracings. The connection of the... more
The connection of tubular members, used as bridge hangers or in 3-D coverings, has been widely researched, both for resistance and for fatigue. Such members are also often used in scaffoldings or as lighter bracings. The connection of the tube to a single bolted or welded plate consists of a circular end plate, covering the tube’s cross section on which a perpendicular rectangular plate is welded. No analytical approximation is available to calculate stresses in such a circular plate. Hence, FE-models have to be used for each application. As this is time consuming, a systematic survey of normal and shear stress has been conducted, for 6 unity connection forces of the gusset plate. The latter are normal force, shear in 2 directions, torsion and bending moments in 2 directions. The 3 types of stresses are kept separate, to allow for linear superposition, simulating any kind of real situation. The tube diameter and plate thickness have been varied to allow regression and obtain closed ...
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To keep the weight orthotropic bridge decks low, modern designs aims for higher and more slender longitudinal stiffeners and the use of low plate thickness. Because of this, a large part of the torsional rigidity of the closed section... more
To keep the weight orthotropic bridge decks low, modern designs aims for higher and more slender longitudinal stiffeners and the use of low plate thickness. Because of this, a large part of the torsional rigidity of the closed section stiffeners is lost by distortion. This profile distortion has two important implications. First, the reduction of torsional rigidity creates a drastic reduction of the load dispersal in the orthotropic plated deck. Second, the distortional deformations, partially restrained at the connection with the floorbeams foreseen with web cut-outs, results in large stress concentrations in the rib wall, which can result in fatigue cracking. Research has been initiated on this subject. The aim is to study the effect of distortion on the load dispersal behavior and stress concentrations in orthotropic bridge deck plates. This research encompasses an analytical approach, numerical modeling with plate elements and superelements and experimental tests, aiming eventua...
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Arch bridge springs can be connected to concrete abutments either by prestressing bars or by connectors. In both options, the torsional stiffness is substantially reduced, compared to the full arch cross sectional area. The influence of... more
Arch bridge springs can be connected to concrete abutments either by prestressing bars or by connectors. In both options, the torsional stiffness is substantially reduced, compared to the full arch cross sectional area. The influence of this lack of torsional stiffness on arch buckling is being researched, both numerically and experimentally. To reduce any residual stress during tests, wooden rods that simulate the arch were submerged in water and subsequently bent to the desired shape. Imperfections of the arch samples are measured. Two unequal concentrated loads are applied to the samples, thus simulating the effect of movable loads across half of the arch span. During loading, lateral deflections were measured until elastic buckling occurred. The simulation of more flexible rotation of the springs required replacing the cross section by thin equivalent side plates. Since all parameters have not been isolated, the results are limited yet. However, comparing the failure load of sim...
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The contribution of the longitudinal stiffeners to the total resistance of compr essed webs or flanges of a box or beam section is gener ally of minor impor- tance, especially if the stiffened part of the section is not subjected directly... more
The contribution of the longitudinal stiffeners to the total resistance of compr essed webs or flanges of a box or beam section is gener ally of minor impor- tance, especially if the stiffened part of the section is not subjected directly to the ef- fect of traffic loads. Design codes require longitudinal stiffeners to be continuous. However, should the panel be part of an element, which does not carry immediately traffic loads, and should the stiffeners be used for preventing the compressed panel from local buckling only, continuity of the stiffeners does not seem imperative. Inves- tigations and FE-calculations with single and continuous web panels with open stiffen- ers under uniform compression on one hand and continuous box girders on the other hand, were made in order to find which factors may influence the effectiveness of non- continuous stiffening (3)(4)(5). In verifying the loss of buckling strength when increas- ing the gap between the edge of the longitudinal stiffener and the crossbeam or the di- aphragms, laboratory buckling tests on plastic single panel models were carried out. Results of the tests show similar evolutions in the buckling strength as can be calcu- lated for steel panels in comparable edge conditions, thus being a good alternative in verifying theoretical results. In addition, attention is given to the restriction of fatigue strength which may be introduced by non-continuous stiffening. Full-scale fatigue tests of steel models of the complete construction detail were carried out focusing on the way of ending the longitudinal stiffeners, either right or skew, and showing much better fatigue capacity.