Partial Joint Penetration Welds Research Articles

Weld Effective Lengths for Axially Loaded Transverse Plate-to-CHS Connections

Large-scale experimental tests were conducted to evaluate the strength of partial joint penetration (PJP) groove welds in axially loaded transverse plate-to-circular hollow section (CHS) X-connections. Six connections, comprising 12 joints, were designed to investigate the influence of branch-to-chord width ratio and chord slenderness on weld strength. Nonuniform strain distributions were observed in the branches adjacent to the joints, indicating that the welds were only partially effective. Results from the experimental tests were used to evaluate design guidance for PJP welds in the American steel design standard, AISC 360-16, and a weld effective length equation is proposed for axially loaded plate-to-CHS connections.

Assessment of partial joint penetration welds on bolted end-plate connections

End-plate moment connections are a very common connection type used in today’s metal building industry. Bolted end-plate connections are especially popular because they can be engineered to meet design requirements for moment resisting connections used in seismically active areas. The current industry standard for end-plate moment connections is to use complete joint penetration (CJP) welds when making end-plate to flange welds. An alternative to CJP welds is partial joint penetration (PJP) welds, which leaves some portion of the base metals’ thickness unfused. PJP welds may save time and money in the fabrication of the end-plate connections but the use of PJP welds in this application is currently not considered in the Seismic Provisions for Structural Steel Buildings AISC/ANSI 341-10[1]. The objective of this research was to evaluate the effectiveness of properly detailed PJP flange welds on end-plate connections when subjected to seismic loading by using a pseudo-static loading protocol. Two of the same multiple row extended end-plate moment connection tests were conducted at the University of Oklahoma’s Donald G. Fears Structural Engineering Laboratory. The tested specimens were 44 in. (111.76 cm) deep, cantilevered beams connected to a column via a bolted end-plate. A concentrated load was applied on the beam’s tip creating a moment at the beam to column connection. This created forces acting on the flange to end-plate welds. The specimens were tested in accordance to AISC 341-10’s[1] criteria on cyclic tests for qualification of beam to column connections. Both six-bolt multiple row extended end-plate connections made with PJP welds met AISC 341-10’s[1] requirements for beam to column connection in Intermediate Moment Frames. The specimens’ flanges and webs deformed plastically, while no weld failures were observed during testing. The PJP welds used on the tested beams’ flange to end-plate connections performed favorably. It is the authors’ beliefs that these results may serve as a good starting point for further examination of PJP weld capabilities when subject to seismic loading. Further testing of PJP welds would help to understand their ultimate capabilities. To date the 44 in. (111.76 cm) deep test sections are to our knowledge, the deepest sections that examined PJP flange to end-plate connections subject to seismic loading successfully achieving a 0.02 rad story drift angle.

Cyclic behavior of stiffened joints between concrete-filled steel tubular column and steel beam with narrow outer diaphragm and partial joint penetration welds

This paper presented an investigation on a stiffened joint in practical engineering which was between concrete-filled steel tubular column and steel beam with narrow outer diaphragm and partial joint penetration welds. Through the low-frequency cyclic loading test, the cyclic behavior and failure mode of the specimen were investigated. The results of the test indicated the failure mode and bearing capacity of the specimen which were influenced by the axial compression ratio of the concrete-filled tubular column. On the contrary, the inner diaphragm and inner stiffeners had limited impacts on the hysteretic behavior of the joint. There was no hysteresis damage fracture on the narrow outer diaphragm connected to the concrete-filled steel tubular column with partial joint penetration welds. Due to the excellent ductility and energy dissipating capacity, the proposed joint could be applied to the seismic design of high-rise buildings in highly intensive seismic region, but axial compression ratio should be controlled to avoid unfavorable failure modes.

Fracture Mechanics-Based Design of Column Splices with Partial Joint Penetration Welds

Design standards in the United States mandate the use of complete joint penetration (CJP) welds for welded column splices (WCS) in high-seismic regions. However, recent experiments suggest that economical partial joint penetration (PJP) welds (which have a cracklike flaw) provide acceptable performance if high-toughness materials are used with large weld penetration. To generalize these findings, a fracture mechanics-based method is proposed for the seismic design of WCS with PJP welds. In support of the design method, four scientific components are presented: (1) finite element fracture mechanics (FEFM) simulations that simulate 25 WCS connections; (2) design equations based on results of the FEFM simulations; (3) Monte Carlo simulation to characterize the uncertainty in the strength determined by the design equations; and (4) reliability analysis to calibrate resistance factors that provide acceptable levels of safety. Trends in the resulting resistance factors and component reliabilities are discussed, and the variability in WCS strength arising from modeling uncertainty (i.e., due to regression fitting of design equations) is determined to be dominant. Simplified guidelines for prescriptive design of WCS connections with PJP welds are presented. In addition to the proposed design equations and resistance factors, a major outcome is the demonstration of a flaw-tolerant design approach based on fracture mechanics. Limitations of the approach are discussed.

Reinforcing fillet welds preventing cracks in partial joint penetration welds

In this paper, effectiveness of reinforcing fillet welds in preventing cracking in roots of partial joint penetration welds is investigated. The method used for this investigation includes finite element modeling and a micromechanical model of crack initiation. Base plate connections of three wide flange sections with various fillet weld dimensions are modeled. A novel method is proposed for idealization of the partial penetration weld geometry. The accuracy of the finite element model and the cracking initiation prediction method are verified based on test results. It is observed that, for each column section, utilizing fillet welds larger than a certain size shifts the crack initiation location from the partial penetration weld root to the column flange, which delays cracking considerably. The aforementioned minimum size of the reinforcing fillet welds depends mainly on thickness of the column flange, and also on the depth of the cross section.

Investigations on the effect of weld penetration on fatigue strength of rib-to-deck welded joints in orthotropic steel decks

A common practice for the manufacture of orthotropic steel decks in Japan is to use 75% partial joint penetration welds between closed ribs and deck plates. To evaluate the effectiveness of the proposed 100% penetration on improving the fatigue strength of rib-to-deck welded joints in orthotropic steel bridge decks, four full-scale orthotropic deck specimens were subjected to laboratory testing. Specimens, consisting of a 12-mm-thick deck plate and 6-mm-thick rib, with one closed rib, were fabricated with 75% and 100% penetration. Fatigue test results showed that fatigue cracks initiated from the weld toe inside the rib in the 100% penetration specimens, but from weld root inside the rib in the 75% penetration specimens. To investigate this fatigue behavior, strain measurements were taken at 5 mm from the rib-to-deck weld line. Results of finite element analysis using the effective notch stress method indicate that a deeper partial penetration results in a slightly higher effective notch stress at the weld root of the partial penetration weld. The effective notch stress at the crack initiation location with 100% penetration is lower than that obtained with partial penetration. The open angle appears to have a significant effect on the effective notch stress at the upper weld toe when using 100% penetration. Therefore, the proposed 100% penetration appeared to have a positive effect on enhancing the fatigue resistance of rib-to-deck welded joints.

Fatigue performance of tubular X-joints with PJP+ welds: I — Experimental study

This study examines the fatigue performance of tubular joints fabricated using a new type of enhanced partial joint penetration weld details under constant-amplitude brace in-plane bending actions. The experimental program includes four cyclic tests on two large-scale X-joints, each with a different surface treatment near the weld toe. The experimental results confirm the satisfactory fatigue performance of the tubular X-joints welded using enhanced partial joint penetration welds in comparison with the S-N curves developed for tubular joints with complete joint penetration welds, and demonstrate the significant improvement on the fatigue life rendered by the weld surface grinding and toe grinding. Root fatigue cracking occurs only in specimens with post-weld toe-grinding treatment which enhances the fatigue life for toe cracking.

Welder-optimized CJP-equivalency welds for tubular connections

This paper will present the experimental and numerical investigation on the fatigue crack failure at the root of the enhanced partial joint penetration welds in the circular hollow section X-joint specimens subjected to constant-amplitude brace in-plane bending actions. The enhanced partial joint penetration welds, which include a portion of the brace wall as the inherent “back-plate” for the welds, reduce the workmanship requirement on the welding procedure and improve the quality control of the welded joint. This study compares the fatigue crack developments observed at both the weld toe and the weld root in three large-scale X-joint specimens with different post-weld surface treatments. Root cracking does not take place in as-welded tubular X-joint specimens, of which the fatigue life depends on the weld toe failure. In specimens with post-weld grinding treatments to enhance fatigue resistance of the material near the weld toe, however, the finite-length root face triggers the initiation and propagation of fatigue cracks with an applied number of cycles more than that required to initiate a toe crack in the same tubular X-joint. Ultimate strength testing of specimens with large fatigue cracks, and post-test sectioning, reveals that fatigue failure weld-toe fatigue cracks remain more critical than the root cracks.

Stress Analyses and Parametric Study on Full-Scale Fatigue Tests of Rib-to-Deck Welded Joints in Steel Orthotropic Decks

Fatigue tests of full-scale orthotropic steel decks were recently conducted to evaluate the fatigue performance of rib-to-deck partial-joint-penetration (PJP) groove welded joints. The test results indicated that rib-to-deck joints are more prone to fatigue cracks in the deck plate than in the rib wall. A shallower weld penetration (for example, an 80% PJP) also appeared to have a slightly higher fatigue resistance than a deeper one (for example, a 100% weld penetration). These PJP welds were also more vulnerable to cracking initiated from the weld toe than from the weld root. Finite-element analyses of the test specimens, using the effective notch stress method, were performed to supplement the laboratory testing and provide additional information on the behavior of these welded joints. The analysis results showed a good correlation with the observed crack patterns. A parametric study also showed that the fatigue resistance of the PJP joint can be significantly influenced by the transverse loading location, deck plate thickness, and the weld penetration ratio. Increasing the deck plate thickness was effective in reducing the stresses, while the rib wall thickness had a little effect. A shallower weld penetration at the PJP joint appeared to have a positive effect in enhancing the fatigue resistance.

Effects of Fabrication Procedures on Fatigue Resistance of Welded Joints in Steel Orthotropic Decks

A common practice for the fabrication of steel orthotropic bridge decks in the United States is to use 80% partial joint penetration (PJP) groove welds between the closed ribs and deck plate. However, it is difficult to eliminate weld melt-through with the thin rib plates. Heat straightening after welding, sometimes combined with precambering, is used to meet the deck plate flatness requirement. To study the effects of both weld melt-through and distortion control measures on the fatigue resistance of the rib-to-deck plate welded joint, six full-scale two-span orthotropic deck specimens were subjected to laboratory testing. Specimens, 10 m long and 3 m wide with four closed ribs, were fabricated with and without weld melt-through and were heat straightened; three specimens were also precambered. To simulate the effect of repetitive truck traffic, each specimen was tested up to 8 million cycles. Test results showed that six cracks initiated from the weld toe outside the rib. Only one crack developed at the weld root inside the rib; this crack initiated from a location transitioning from the 80% PJP to 100% penetration weld. None of the cracks propagated through the deck plate thickness. Precambering was beneficial in fatigue resistance as two effectively precambered specimens did not experience cracking in the PJP welds.

Effect of weld details on the ductility of steel column baseplate connections

Results from six two-thirds scale tests on moment-resisting steel column base plates are presented. The test specimens incorporate Complete Joint Penetration (CJP) and Partial Joint Penetration (PJP) weld details between the column and the base plate. The test data indicate that both details are resilient to fracture and sustain inelastic column hinging to story drift ratios of 6%–9%, which exceeds the typical acceptance criteria of 4% drift ratio for seismically detailed special moment frames. In five of the six tests, fractures initiated in the Heat Affected Zone (HAZ) at the fusion line between the weld and column flange. In the sixth test, fractures initiated at the inside face of the column flange at the upper edge of the weld access hole of the CJP weld detail. Contrary to the initial expectations, the specimens with the PJP welds exhibited higher displacement ductility than those with CJP welds. This is attributed to the fillet reinforcing that strengthens the PJP welds and enables them to sustain stresses and strains necessary to fully develop yielding in the column flanges. The test data further support the adequacy of the FEMA 350 provisions for determining the required strength of the welds based on the probable moment demand with the material overstrength factor of R y = 1.1 and strain hardening factor of C p r = 1.2 .

Multiaxial fatigue of welded shaft-flange connections of stirrers under random non-proportional torsion and bending: Sonsino, C.M. and Pfohl, R. Int. J. Fatigue Sept. 1990 12, (5), 425–431

This study examines the fatigue performance of tubular joints fabricated using a new type of enhanced partial joint penetration weld details under constant-amplitude brace in-plane bending actions. The experimental program includes four cyclic tests on two large-scale X-joints, each with a different surface treatment near the weld toe. The experimental results confirm the satisfactory fatigue performance of the tubular X-joints welded using enhanced partial joint penetration welds in comparison with the S-N curves developed for tubular joints with complete joint penetration welds, and demonstrate the significant improvement on the fatigue life rendered by the weld surface grinding and toe grinding. Root fatigue cracking occurs only in specimens with post-weld toe-grinding treatment which enhances the fatigue life for toe cracking.