@article{hassan_quayyum_2022, title={Influence of Weld Sequence on the Low-Cycle Fatigue Failure of WUF-B Connections}, volume={148}, ISSN={["1943-541X"]}, DOI={10.1061/(ASCE)ST.1943-541X.0003350}, abstractNote={Experiments on post-Northridge welded unreinforced flange bolted web (WUF-B) connections demonstrated a new low-cycle fatigue (LCF) crack initiation mechanism with final rupture occurring either near the weld access hole or the weld regions. Post-Northridge connection research reports and related commentary indicated that the weld and heat-affected zone (HAZ) conditions might be contributing factors in LCF-initiated failures of the modified WUF-B connections. The experimental study reported herein investigated the influence of weld sequence on the fatigue failure of the WUF-B connections. Two exterior WUF-B connections were fabricated using different weld sequences in laying the complete joint penetration welding between the beam and column flanges. These connections were tested under a constant-amplitude displacement-controlled loading protocol until crack initiation. Both specimens failed by cracking at the weld access hole, one in a brittle manner and the other in a ductile manner. Analysis of the recorded data demonstrated the influence of weld sequence on strain responses at the weld toe and weld access hole regions. Accumulation of strain with cycles, which is a phenomenon known as strain ratcheting, was observed near these locations in both tests. Recorded strain responses near the crack locations indicated the cause of earlier failure of one specimen compared with the other. Finally, future research needs in mitigating the influence of welding sequence on fatigue failure of welded steel moment connections are discussed.}, number={7}, journal={JOURNAL OF STRUCTURAL ENGINEERING}, author={Hassan, Tasnim and Quayyum, Shahriar}, year={2022}, month={Jul} }
 @article{morrison_schweizer_quayyum_hassan_2019, title={An Unstiffened Eight-Bolt Extended End-Plate Moment Connection for Special and Intermediate Moment Frames}, volume={145}, ISBN={1943-541X}, DOI={10.1061/(ASCE)ST.1943-541X.0002332}, abstractNote={Bolted extended end-plate (BEEP) moment-resisting connections are prequalified for use in special and intermediate moment frames. The current limits of this prequalification dictate that rolled wide-flange sections with a depth greater than 601 mm (24 in.) necessitate the use of the stiffened eight-bolt extended end-plate connection. The study reported herein experimentally evaluates an unstiffened eight-bolt extended end-plate connection for seismic applications. The connection features a modified bolt arrangement designed to promote uniform distribution of forces across the bolt group. Plastic hinging of the beam is relocated away from the connection joint by heat-treating selected regions of the beam flanges to reduce the strength of steel. Finally, the beam web is reinforced in the expected plastic hinge region to delay strength degradation due to local buckling. The pilot test specimen exceeded the qualifying 4% interstory drift angle. Failure occurred from buckling-induced fracture in the plastic hinge during loading cycles at 6% interstory drift. In this article, details of experimental development and test results are presented and the connection performance is further analyzed through posttest finite-element simulations.}, number={7}, journal={JOURNAL OF STRUCTURAL ENGINEERING}, author={Morrison, Machel L. and Schweizer, Doug Q. and Quayyum, Shahriar and Hassan, Tasnim}, year={2019} }
 @article{quayyum_hassan_2018, title={Seismic Performance of a Fire-Exposed Moment-Resisting Frame}, volume={144}, ISSN={["1943-541X"]}, DOI={10.1061/(ASCE)ST.1943-541X.0002201}, abstractNote={Major earthquakes in urban areas often lead to building fires. Such earthquakes frequently damage buildings’ water sprinkler systems and diminish or strain firefighting capabilities. In such scenarios, buildings get exposed to fire for a long period of time, resulting in damage of spray-on-fire resistive materials. Consequently, steel frame temperature may reach as high as the maximum fire temperature, which subsequently cools slowly to ambient temperature. If the building frame does not deform severely after such a fire event, it is usually rehabilitated for continued occupation. The performance of such a fire-exposed steel building during a future earthquake is not known. This study investigates the seismic performance of a fire-exposed steel frame by performing finite-element analyses incorporating fire-exposed steel material properties. The simulation responses demonstrate vulnerability of fire-exposed steel buildings. A novel but startling observation made is that under seismic loading, a fire-damaged steel frame may form a soft-story mechanism at the story of fire exposure because of plastic hinge formation in the column instead of in the beams.}, number={11}, journal={JOURNAL OF STRUCTURAL ENGINEERING}, author={Quayyum, Shahriar and Hassan, Tasnim}, year={2018}, month={Nov} }
 @article{morrison_quayyum_hassan_2017, title={Performance enhancement of eight bolt extended end-plate moment connections under simulated seismic loading}, volume={151}, ISSN={["1873-7323"]}, DOI={10.1016/j.engstruct.2017.08.040}, abstractNote={Extended end-plate (EEP) moment resisting connections provide the advantage of eliminating field welding and by virtue of this, facilitate fast field erection of building frames. The eight bolt stiffened (8ES) EEP connection is one of the prequalified moment connections in the AISC 358 standard for special moment frames (SMFs) in seismic regions. In this connection, a stiffener plate is welded between the end plate and the beam flanges to strengthen the extended portion of the end plate. This stiffener reduces prying action and more uniformly distributes flange forces among the bolt group. In experimental studies, the 8ES connection has shown ductile response to simulated seismic loading with test specimens typically failing due to beam buckling and gradual strength degradation. However, cracks initiating at the toe of the stiffener leading to brittle fracture of the beam flange has also been observed due to the high stress concentration in this region. The study reported herein proposes an eight-bolt EEP connection in which the end plate stiffener is removed and the bolt arrangement is modified to promote uniform distribution of flange forces among the bolt group. The proposed connection was developed through detailed finite element analysis in which various bolt arrangements for stiffened and unstiffened eight-bolt EEP connections were considered. The proposed connection displayed reduced beam flange stress and strain concentrations, delayed or reduced rate of strength degradation from local buckling and more uniform distribution of bolt forces when compared to the alternatives. Furthermore, when compared to the currently prequalified 8ES connection, despite requiring thicker end plates, the proposed connection is anticipated to result in cost savings from the removal of the end plate stiffener. Future analytical and experimental needs for further development of the proposed connection are discussed.}, journal={ENGINEERING STRUCTURES}, author={Morrison, Machel and Quayyum, Shahriar and Hassan, Tasnim}, year={2017}, month={Nov}, pages={444–458} }
 @inproceedings{quayyum_sengupta_choi_lissenden_hassan_2014, title={Fatigue and ratcheting experimental responses of alloy 617 under high temperature multiaxial loading}, DOI={10.1115/pvp2013-97252}, abstractNote={Nickel based Alloy 617 is one of the leading candidate materials for intermediate heat exchanger (IHX) of the next generation nuclear plant (NGNP). The IHX is anticipated to operate at temperatures between 800–950°C, which is in the creep regime. In addition, system start-ups and shut-downs will induce low cycle fatigue (LCF) damages in the IHX components. Hence, designing IHX using Alloy 617 for NGNP construction will require a detailed understanding of the creep-fatigue and ratcheting responses. In this study, a broad set of multiaxial creep-fatigue and ratcheting experiments are performed and the results are critically evaluated. Experiments are conducted by prescribing multiaxial loading histories in axial and shear directions at 850°C and 950°C with different strain rates and strain amplitudes. Experimental results revealed that the axial strain ratcheting and cyclic hardening/softening responses of Alloy 617 vary significantly with temperature levels, strain rates and strain amplitudes indicating the dependence of creep-fatigue and ratcheting responses on these parameters. This necessitates the incorporation of strain rate and strain amplitude dependence and effect of loading non-proportionality and temperature in the unified constitutive modeling (UCM) for a better prediction of the material behavior. Development of a UCM is underway based on the experimental results developed.}, booktitle={Proceedings of the ASME Pressure Vessels and Piping Conference - 2013, vol 3: Design and Analysis}, author={Quayyum, S. and Sengupta, M. and Choi, G. and Lissenden, C. J. and Hassan, T.}, year={2014} }
 @article{alam_billah_quayyum_ashraf_rafi_rteil_2013, title={Fire performance curves for unprotected HSS steel columns}, volume={15}, ISSN={["1598-6233"]}, DOI={10.12989/scs.2013.15.6.705}, abstractNote={The behaviour of steel column at elevated temperature is significantly different than that at ambient temperature due to its changes in the mechanical properties with temperature. Reported literature suggests that steel column may become vulnerable when exposed to fire condition, since its strength and capacity decrease rapidly with temperature. The present study aims at investigating the lateral load resistance of non-insulated steel columns under fire exposure through finite element analysis. The studied parameters include moment-rotation behaviour, lateral load-deflection behaviour, stiffness and ductility of columns at different axial load levels. It was observed that when the temperature of the column was increased, there was a significant reduction in the lateral load and moment capacity of the non-insulated steel columns. Moreover, it was noted that the stiffness and ductility of steel columns decreased sharply with the increase in temperature, especially for temperatures above 400°C. In addition, the lateral load capacity and the moment capacity of columns were plotted against fire exposure time, which revealed that in fire conditions, the non-insulated steel columns experience substantial reduction in lateral load resistance within 15 minutes of fire exposure.}, number={6}, journal={STEEL AND COMPOSITE STRUCTURES}, author={Alam, M. Shahria and Billah, A. H. M. Muntasir and Quayyum, Shahriar and Ashraf, Mahmud and Rafi, A. N. M. and Rteil, Ahmad}, year={2013}, month={Dec}, pages={705–724} }