Bridge cover plate weld crack

In a few cases failure was observed from the weld root. Potential for fracture to occur in iowa dot steel girder. Steel bridge research, inspection, training, and engineering s. Bridges a to e represent several cases of allwelded trial railway bridges.

Did you want to learn how to work around that and deliver a solid repair. Fatigue studies on beams with welded cover plates and long attachments. Reinforcing cover plates ending near existing rivets were welded to the webs of the. Manual scm to determine the limits of the cracked fillet weld. Fatigue strength of steel bridge members with intersecting. For the purposes of this study, the cover plate is assumed to be located on a threespan bridge girder as shown in fig. The investigation of the fractured girder on the i80 bridge over the cedar river.

This is true of both fillet and groove welded details. Critical crack sizes dictate the transition of the 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. 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. Acoustic emission assessment of fatigue crack growth from. Stress concentration and fatigue of welded details, ph. Subsequent inspection revealed the presence of numerous smaller cracks at the cover plate. This category includes six beams in span 2 at the i66 eb bridge, and one beam in span 2 at the i66 wb bridge. Prior to weld repair, a crack stop hole is drilled at the end of the crack to reduce stress. Fatigue cracks develop at the transverse weld toe of stiffeners, attachments, and cover plates in steel bridge members. I didnt find any paper or code statement allowances about that. It is readily apparent that substantial increases in life were. Identification and rehabilitation of fatigue details presented by.

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. 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. Category e or e ends of welded cover plate ends of wider cover plate wakota bridge termination of cover plates 36 and cleveland. The two major cracks appear to have initiated by constraintinduced fracture cif. Figure 5 flange plate passing though intersecting web with holes at flange tip. Weld cracking several types of discontinuities may occur in welds or heat affected zones. Butt weld in cover plate 4 g blast plate welded to bottom flange 2. Maintenance actions to address fatigue cracking in steel bridge. 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. This paper investigates the fatigue upgrading of typical cover plate joint connections in existing steel bridge girders through cover plate extension. The precracked details usually failed from continued crack growth from the original crack, but at a slower rate. 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.

A fatigue crack started at the toe of the boss weld and propagated across the gusset plate. Cover plates are used to reinforce bridge girders at the locations where maximum bending moments occur. 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. Manual for repair and retrofit of fatigue cracks in steel bridges. Air hammer peened cover plate end weld toe a fatigue crack progression b exposed fracture surface figure 6. 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. Adding cover plates weld under tension adding cover plates weld under tension crossframe. Download scientific diagram crack initiated from weld toe in steel bridge igirder with cover plate from publication. The plans for the other bridge specified fillet welds.

Such a high volume of weld metal creates significant shrinkage forces. A survey of localized cracking in steel bridges by. Repairing cracked steel structures with carbon fiber. Typical fatigue crack across a repaired flange butt weld in a welded igirder test. Figure 4 crack in box girder web at intersecting flange tip. We typically recommend a 5t flexure distance, where t is the thickness of the flexing gusset plate, to avoid this type of damage. Paint shall be removed at least 6 inches from areas of work prior to flame cutting, flame straightening, aircarbon arc gouging, andor welding operations. Crack repair a typical procedure for a welded crack repair includes crack removal, edge preparation, placement of. Crack initiated from weld toe in steel bridge igirder with cover plate. Full depth crack, 34 into width of flange but not failure. Fatigue cracking in welded steel bridges transportation. These cracks resulted from the high volume of truck traffic and the unanticipated low fatigue resistance of the large cover plated beams 5. Retrofitting procedures for fatigue damaged full scale.

Fatigue strength upgrading of cover plate ends by welded. Exercise care during removal to avoid damaging the top flange or the stiffener. Load induced fatigue design for steel bridges according to the aashto lrfd specifications agenda 1. Have you ever welded something so thin and worn out that all you do is blow holes in it. 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. After students understand the advantages and disadvantages of the traditional methods, present the first challenge question in this lesson. April 2018 fatigue life improvement of welded girders with ultrasonic impact treatment jonathan f. Of the three, cracks are by far the most detrimental. There are 7 common mistakes people make when they start mig welding. Reexamine the weld using mt or pt to ensure that the crack has been completely removed. The cracks start at an initial discontinuity in the weld or at the edge of the weld and grow perpendicular to the cyclic stresses. Acoustic emission ae has been increasingly used for assessment and prediction of fatigue cracks in steel bridge members. Remove crack andor defective material with air carbon arc process or equivalent while creating a weld joint consistent with aws bp2 for. Fatigue life improvement of welded girders with ultrasonic.

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. The same detail on another crane resulted in failure. Another lowfatiguestrength detail is the welded web gus set plate shown in figure 2. Classic and recent examples of fatigue cracking of welded connections. 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. Most fatigue cracking in welded structures initiates at or in the weld. The end of he longiludinal weld allaching he cover plate 0 the flange and. If a crack like indication is found, further grinding and. Through throat cracking at peened cover plate end weld in yellow mill pond bridge 4. Effects of increasing traffic loads on the fatigue. It had grown from the toe of the cover plate transverse fillet weld into the. Unfortunately, this book cant be printed from the openbook.

When these forces exceed the strength of the weld, cracking ensues. Cracks in rolled beams or plate girders are repaired using approved welding procedures developed for the particular case. Remove damaged welds between cover plate and bottom flange where applicable. 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. Detailing of splice plate retrofit for cracked coverplate details. Whereas there are acceptable limits for slag inclusions and porosity in welds, cracks are never acceptable. Department of transportation federal high way administration steel bridge design handbook design for fatigue archived publication no.

Crackweld concrete floor crack repair kit selfleveling, waterproofing repair for cracks in concrete floors. Welds may contain porosity, slag inclusions or cracks. 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. Icme analysis of fatigue crack growth through a weld in sa. 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. Retrofitting procedures for fatigue damaged full scale welded bridge beams, final report, january 1979. Using slides 710, briefly show the traditional repair methods crack stop holes, cover plates, welding and mention their drawbacks. To occur in iowa dot steel girder bridges due to triaxial constraint. Figure 1 fatigue crack at end of coverplate on yellow mill. 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. Recommended method for repairing fatigue cracking twi. Left parapet joint plate cover at abutment 2 is misaligned up to 1 towards the roadway see photo 28. Extending bridge service life through field welded repairs. Dctails which serve the intended function and provide the highest fatigue strength should be considered.