Bridge cover plate weld crack

The weld bead acts as the fulcrum of the flexure joint, and as seen from inspection of the geometry and loading represented in the zoomed in portion of figure 1 that inherent in the design there is a severe notch formed between the flexure plate, weld bead, and stiffening ring that will be the site of crack initiation and location from which. Through throat cracking at peened cover plate end weld in yellow mill pond bridge 4. The length, a varies from one to two times the cover plate width, depending on the weld group configuration and weld size relative to plate thickness. For the purposes of this study, the cover plate is assumed to be located on a threespan bridge girder as shown in fig.

Acoustic emission assessment of fatigue crack growth from. Of the three, cracks are by far the most detrimental. The two major cracks appear to have initiated by constraintinduced fracture cif. If a crack like indication is found, further grinding and. Air hammer peened cover plate end weld toe a fatigue crack progression b exposed fracture surface figure 6. Stress concentration and fatigue of welded details, ph. The end of he longiludinal weld allaching he cover plate 0 the flange and. Fatigue cracking in welded steel bridges transportation. Figure 1 fatigue crack at end of coverplate on yellow mill. Fatigue studies on beams with welded cover plates and long attachments. Fillet weld a weld of approximately triangular cross section that joins two surfaces approximately at right angles to each other in a lap joint, tjoint, or corner joint. Assuming the same strength requirements from the fillet welds as for the tbutt welds it becomes more economical to use a double sided full penetration tbutt joint at a plate thickness of around 30mm.

Figure 4 crack in box girder web at intersecting flange tip. Another lowfatiguestrength detail is the welded web gus set plate shown in figure 2. A fatigue crack started at the toe of the boss weld and propagated across the gusset plate. Weld cracking several types of discontinuities may occur in welds or heat affected zones. The plans for the other bridge specified fillet welds. Detailing of splice plate retrofit for cracked coverplate details. Adding cover plates weld under tension adding cover plates weld under tension crossframe. It is an usual practice during pressure vessel internal inspection, when long crack is discovered plate welded to shell by fillet weld to stop it drilling a small hole at the end of the crack. It had grown from the toe of the cover plate transverse fillet weld into the. Key words steel, fatigue, fracture, weld, bridge, girder, stiffener, gusset plate, retrofit, drilled holes, remaining life 18. Cover plates are used to reinforce bridge girders at the locations where maximum bending moments occur. It is readily apparent that substantial increases in life were.

Fatigue strength of steel bridge members with intersecting. Remove damaged welds between cover plate and bottom flange where applicable. Such a high volume of weld metal creates significant shrinkage forces. To occur in iowa dot steel girder bridges due to triaxial constraint.

Fatigue cracks develop at the transverse weld toe of stiffeners, attachments, and cover plates in steel bridge members. Crack repair a typical procedure for a welded crack repair includes crack removal, edge preparation, placement of. Typical fatigue crack across a repaired flange butt weld in a welded igirder test. After students understand the advantages and disadvantages of the traditional methods, present the first challenge question in this lesson. The 65foot welded span in the twospan steel bridge at the facility for accelerated service testing has developed two major web and tension flange cracks, as well as numerous cracks in secondary members, during 15 years of service under heavy axle load traffic. We typically recommend a 5t flexure distance, where t is the thickness of the flexing gusset plate, to avoid this type of damage. The investigation of the fractured girder on the i80 bridge over the cedar river.

This paper investigates the fatigue upgrading of typical cover plate joint connections in existing steel bridge girders through cover plate extension. If crack growth is allowed to go on long enough, failure of the member can result when the uncracked crosssection is sufficiently reduced such that the member can no longer carry the internal forces for the crack extends in an unstable mode. Have you ever welded something so thin and worn out that all you do is blow holes in it. How to bridge gaps and holes on thin metal youtube. The accuracy of this figure should be treated with caution as it is dependent on many factors such as the weld preparation costs and included angle. The latter can often be achieved by postrepair mechanical operations such as weld toe grinding or peening in the case of fatigue crack initiation from weld toes.

Repairing cracked steel structures with carbon fiber. Cover plate weld flange crack growth process technical standards branch class a bridge inspection course bim bridge inspection and maintenance steel girder bridges 53 through crack at a cover plate technical standards branch class a bridge inspection course bim. Critical crack sizes dictate the transition of the crack. Most fatigue cracking in welded structures initiates at or in the weld. Category e or e ends of welded cover plate ends of wider cover plate wakota bridge termination of cover plates 36 and cleveland. These cracks resulted from the high volume of truck traffic and the unanticipated low fatigue resistance of the large cover plated beams 5. Subsequent inspection revealed the presence of numerous smaller cracks at the cover plate. The failure originated as a crack at the toe of the fillet weld along the end of the primary cover plate and propagated through the flange and 16 inches up into the web. Extending bridge service life through field welded repairs. When these forces exceed the strength of the weld, cracking ensues. If you dont create a smooth transition of weld metal to base metal, you can disrupt the flow of forces through the weld. Manual scm to determine the limits of the cracked fillet weld.

There are 7 common mistakes people make when they start mig welding. Longitudinal section through flange cover plate and transverse end weld gta retrofit crack at gta retrofitted weld toe. Classic and recent examples of fatigue cracking of welded connections. Bridges a to e represent several cases of allwelded trial railway bridges. This category includes six beams in span 2 at the i66 eb bridge, and one beam in span 2 at the i66 wb bridge. The upgraded detail is created by removing the existing transverse end weld, then welding the extension to the existing cover plate with the underlying plate acting as backing. Butt weld in cover plate 4 g blast plate welded to bottom flange 2. Remove crack andor defective material with air carbon arc process or equivalent while creating a weld joint consistent with aws bp2 for. Recommended method for repairing fatigue cracking twi. Crackweld concrete floor crack repair kit selfleveling, waterproofing repair for cracks in concrete floors. Left parapet joint plate cover at abutment 2 is misaligned up to 1 towards the roadway see photo 28. Did you want to learn how to work around that and deliver a solid repair. Icme analysis of fatigue crack growth through a weld in sa.

Reinforcing cover plates ending near existing rivets were welded to the webs of the. Download scientific diagram crack initiated from weld toe in steel bridge igirder with cover plate from publication. Crackweld easily fills the full depth of stress cracks, hairline cracks, fissures and imperfections in concrete floors and mortar joints without the need to chisel or route the crack crackweld cures fast as a rigid compound, welding the concrete together providing flooring. This is true of both fillet and groove welded details. Prior to weld repair, a crack stop hole is drilled at the end of the crack to reduce stress. In a few cases failure was observed from the weld root. Paint shall be removed at least 6 inches from areas of work prior to flame cutting, flame straightening, aircarbon arc gouging, andor welding operations. The precracked details usually failed from continued crack growth from the original crack, but at a slower rate. The cracks start at an initial discontinuity in the weld or at the edge of the weld and grow perpendicular to the cyclic stresses. Cracks in rolled beams or plate girders are repaired using approved welding procedures developed for the particular case. Welds may contain porosity, slag inclusions or cracks.

Identification and rehabilitation of fatigue details presented by. Whereas there are acceptable limits for slag inclusions and porosity in welds, cracks are never acceptable. A survey of localized cracking in steel bridges by. Acoustic emission ae has been increasingly used for assessment and prediction of fatigue cracks in steel bridge members. Crack initiated from weld toe in steel bridge igirder with cover plate. Retrofitting procedures for fatigue damaged full scale welded bridge beams, final report, january 1979. April 2018 fatigue life improvement of welded girders with ultrasonic impact treatment jonathan f. I didnt find any paper or code statement allowances about that. If you need to print pages from this book, we recommend downloading it as a pdf. The use of cover plates in regions of high moment allows the use of a section of lesser weight and lesser flexural capacity to be used as the primary beam.

Steel bridge research, inspection, training, and engineering s. Manual for repair and retrofit of fatigue cracks in steel bridges. The same detail on another crane resulted in failure. Unfortunately, this book cant be printed from the openbook.

Figure 5 flange plate passing though intersecting web with holes at flange tip. Fatigue strength upgrading of cover plate ends by welded. We are adding cover plates to an existing continuous steel girder bridge as part of a strengthening rehabilitation, and are trying to give the contractor as much flexibility as possible by allowing both field welded with bolted end connections and. The former may be achieved by addition of material, welded or mechanically fastened to provide additional load paths, or local redesign to reduce stress concentrations. Load induced fatigue design for steel bridges according to the aashto lrfd specifications agenda 1. Potential for fracture to occur in iowa dot steel girder. Department of transportation federal high way administration steel bridge design handbook design for fatigue archived publication no. Retrofitting procedures for fatigue damaged full scale. Effects of increasing traffic loads on the fatigue. The crack generally is directed down into the base metal, right at the weld toe. Dctails which serve the intended function and provide the highest fatigue strength should be considered.

Reexamine the weld using mt or pt to ensure that the crack has been completely removed. Table 1 lists some of the first welded bridges per some selected countries, with the indication of their location, year of construction, maximum span length in case of multiple spans, main traffic type, structural type, current condition and if some sort of cracks have been reported. Attachments to girders such as cover plates, stifeners or other components welded to a flange or web. Exercise care during removal to avoid damaging the top flange or the stiffener. Maintenance actions to address fatigue cracking in steel bridge.