Fatigue Strength of Welded A514 Steel Beams

The fatigue strength of beams with tapered cover plates was investigated both experimentally and analytically. The test specimens were precracked and then repaired with one of the following three methods: a friction type bolted splice plate connection, air-hammer peening along the weld toe, and a hybrid of the previous two called the partial bolted splice connection. Test results demonstrated that the bolted splice connection was the most effective repair method. Cracked cover plate ends repaired with a bolted splice connection, partial bolted splice connection, and air-hammer peening demonstrated an increase in fatigue life equal to categories B, C, and D of the American Association of State Highway and Transportation Officials (AASHTO) specifications, respectively. Air-hammer peening was found to be particularly effective if applied to noncracked cover plate ends, with an increase in fatigue life equal to category B′. An analytical model was developed to predict the propagation life of cracked cover pla...

Fatigue Crack Repair of Steel Beams with Tapered Cover Plate Details

A DATA ACQUISITION SYSTEM ASSEMBLED FOR THE PURPOSE OF MONITORING AND DIGITIZING STRAINS PRODUCED BY ORDINARY TRUCK TRAFFIC IN HIGHWAY BRIDGES IS DESCRIBED. THE SYSTEM CONSISTS OF WHEATSTONE BRIDGE COMPLETION MODULES, AMPLIFIERS, AN ANALOG-TO-DIGITAL CONVERTER, A DIGITAL PROCESSING UNIT, AND A TELETYPE MACHINE. A COMPUTER PROGRAM TO BE USED WITH THE DATA ACQUISITION SYSTEM IS PRESENTED. THE SYSTEM WAS USED IN A PILOT STUDY ON AN INTERSTATE HIGHWAY BRIDGE NEAR DUMFRIES, VIRGINIA. STRAINS WERE MONITORED DURING SEVERAL SAMPLING PERIODS, AND TRUCKS WERE WEIGHED AND CLASSIFIED AT A NEARBY WEIGHING STATION. THE PERFORMANCE OF THE SYSTEM WAS SATISFACTORY. GENERALLY LOW STRAINS WERE MEASURED, BEING FOR THE MOST PART LESS THAN HALF OF THE CALCULATED LIVE-LOAD DESIGN VALUES. /AUTHOR/

Loading history of highway bridges

Fatigue Life Assessment of Bridge Details Using Finite Element Method

In a simply supported composite bridge girder the concrete is in compression over the full length of the bridge, whereas in a continuous multispan bridge some regions of the bridge are subjected to negative bending moment, in which case the concrete goes into tension. With respect to fatigue behavior of stud shear connectors, one key difference between placing studs in the positive and negative moment regions is the stress state of the base metal of the beam flange. The fact that the beam flange is in tension at the base of the studs in the negative moment region raises questions about whether this affects their fatigue endurance. This report summarizes the research behind the fatigue design provisions for shear connectors in the negative moment region in the American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Specifications.

https://conservancy.umn.edu/bitstream/handle/11299/656/1/CTS0003.pdf

Fatigue of stud shear connectors in the negative region of steel girder bridges: a synopsis of experimental results and design recommendations

RESULTS ARE SUMMARIZED OF TESTS MADE TO DEMONSTRATE THE EFFECT OF DETAILS ON THE FATIGUE BEHAVIOR OF WELDED FLEXURAL MEMBERS. TEST CONDITIONS ARE RELATED TO ACTUAL SERVICE CONDITIONS. DETAILS SUCH AS SPLICES, STIFFENERS, COVER PLATES AND ATTACHMENTS, ALL OF WHICH CAN BE EXPECTED TO PRODUCE REDUCTIONS IN THE FATIGUE STRENGTH OF THE BASIC MEMBER, WERE INCLUDED. TESTS WERE CONDUCTED ON SPECIMENS FABRICATED FROM ASTM A73 STEEL. MANUAL ARC WELDING WITH NUMBER 7016 ELECTRODES WAS USED IN THE FABRICATION OF MOST OF THE SPECIMENS FOR THE TESTS. THE WELDS WERE DEPOSITED WITH REVERSED POLARITY, IN THE FLAT POSITION, AND WITH 5/32- IN. ELECTRODES FOR THE ASSEMBLY OF THE BASIC SECTION AND 1/8-IN. ELECTRODES FOR THE ATTACHMENT OF STIFFENERS. ALL ELECTRODES WERE STORED IN A DRYING OVEN TO PREVENT ABSORPTION OF MOISTURE IN THE ELECTRODE COATING. THE BEAMS WERE TESTED IN A 200,000-LB FATIGUE TESTING MACHINE. AFTER FAILURE OF THE TEST MEMBERS, THE ACTUAL DIMENSIONS OF THE CROSS-SECTION AT THE FAILURES WERE MEASURED AND THE STRESSES AT THESE LOCATIONS CALCULATED. TESTS ON THE FATIGUE BEHAVIOR OF I-BEAMS SHOW THAT ONE FACTOR WHICH HAS AN EFFECT ON THE FATIGUE RESISTANCE OF THE WELDED BEAMS IS THE RATIO OF THE THICKNESS OF THE FLANGE TO THAT OF THE WEB. IN ADDITION TO THE VARIATION IN FATIGUE LIFE WITH THE FLANGE-TO-WEB THICKNESS RATIO, A DIFFERENCE IN THE MODE OF FAILURE WAS OBSERVED. THE POINT OF FAILURE INITIATION WAS GENERALLY THE SAME--IN A WELD CRATER OF THE FILLET WELDS AT THE WEB-FLANGE JUNCTION. A SUMMARY OF THE FATIGUE STRENGTHS OF THE VARIOUS TYPES OF SPLICED MEMBERS IS PRESENTED IN A TABLE. THE FATIGUE STRENGTH OF THE SPLICED BEAMS CAN BE MADE TO APPROACH OR EQUAL THAT OF A PLAIN PLATE WITH A TRANSVERSE BUTT WELD. HOWEVER, THE FATIGUE STRENGTH OF THE SPLICED MEMBERS AT 2,000,000 CYCLES IS ONLY ABOUT TWO-THIRDS AS GREAT AS THE FATIGUE STRENGTH OF THE PLAIN PLATE MATERIAL. RELATIONSHIPS WERE USED TO DETERMINE THE MAXIMUM PRINCIPAL TENSILE STRESS AT THE POINT WHERE FAILURE INITIATED IN STIFFENERS. IT APPEARS THAT WHEN STIFFENERS ARE NOT WELDED TO THE TENSION FLANGE OF A FLEXURAL MEMBER THAT IS SUBJECTED TO REPEATED LOADS, THE SHEAR IN THE WEB OF THE MEMBER SHOULD BE CONSIDERED. IT IS CONCLUDED THAT THE MOST EFFECTIVE MEANS OF INCREASING THE FATIGUE RESISTANCE OF THE BEAMS OF VARIABLE SECTION IS TO VARY THE FLANGE IN WIDTH OR THICKNESS. IT CAN BE SEEN THAT WHEN THE CURRENT SPECIFICATIONS ARE CORRECTLY APPLIED, WELDED BEAMS AND GIRDERS OF HIGHWAY BRIDGES, IF PROPERLY FABRICATED, SHOULD HAVE ADEQUATE FATIGUE CAPACITY. IN VIEW OF THE WEB FAILURES OBSERVED, FURTHER CONSIDERATION SHOULD BE GIVEN TO THE EFFECT OF SHEAR ON THE FATIGUE BEHAVIOR OF MEMBERS WITH THIN WEBS.

J E Stallmeyer

Papers

Fatigue in welded beams and girders