Evaluation of extreme load performance of pre-Northridge connections

Katastrofalne posljedice djelomičnog urušavanja apartmana Ronan Point 1968. i potresa u Northridgeu 1994. razotkrile su osjetljivost čeličnih okvira izloženih ekstremnim opterećenjima. Izvješća ovih dvaju katastrofalnih događaja pokazala su značajnu ulogu priključka nosač-stup gdje su se pretežno događala oštećenja. Numeričko i eksperimentalno istraživanje provedeno je u skladu sa 2010 AISC seizmičkim odredbama i UFC 4-023-03 smjernicama. Nisko ciklično ponašanje i rotacijski kapacitet proizlaze iz analize gdje je lom u blizini sučeonog zavara bio način otkazivanja uzoraka.Disastrous consequences of a partial collapse of the Ronan Point apartment in 1968, along with the 1994 Northridge earthquake, exposed the vulnerability of steel moment frames subjected to extreme loading. The reports of these two catastrophic events revealed the significant role of the beam-to-column connection where the damage was mainly formed. A numerical and experimental investigation was conducted in accordance with 2010 AISC Seismic Provisions and UFC 4-023-03 Guideline. An inadequate cyclic behaviour and rotational capacity resulted from the analysis where the fracture in the vicinity of groove welding was due to a poorly designed connection

Classification System for Semi-Rigid Beam-to-Column Connections

Abstract The current study attempts to recognise an adequate classification for a semi-rigid beam-to-column connection by investigating strength, stiffness and ductility. For this purpose, an experimental test was carried out to investigate the moment-rotation (M-θ) features of flush end-plate (FEP) connections including variable parameters like size and number of bolts, thickness of end-plate, and finally, size of beams and columns. The initial elastic stiffness and ultimate moment capacity of connections were determined by an extensive analytical procedure from the proposed method prescribed by ANSI/AISC 360-10, and Eurocode 3 Part 1-8 specifications. The behaviour of beams with partially restrained or semi-rigid connections were also studied by incorporating classical analysis methods. The results confirmed that thickness of the column flange and end-plate substantially govern over the initial rotational stiffness of of flush end-plate connections. The results also clearly showed that EC3 provided a more reliable classification index for flush end-plate (FEP) connections. The findings from this study make significant contributions to the current literature as the actual response characteristics of such connections are non-linear. Therefore, such semi-rigid behaviour should be used to for an analysis and design method

Cyclic behaviour of fully-rigid and semi-rigid steel beam-to-column connections

A test program was considered to clarify the cyclic characteristics of eight full-scale unstiffened extended end-plates with variable parameters and one SidePlate moment connection. All specimens were subjected to 2010 AISC seismic provision loading protocol where flexural strengths were identified at each interstorey drift angle. The results showed that all unstiffened extended end-plate failed to develop full inelastic capacity of connected beams and plastic hinges mainly appeared in the connection’s components. On the other hand, the SidePlate moment connection had the capacity to develop adequate interstorey drift angles up to 0.06 rad, indicating that this type of connection possesses sufficient stiffness and strength to be classified as a rigid and full-strength connection. The results also showed that SidePlate possesses considerably more energy dissipation capacity and an equivalent hysteretic damping ratio compared to unstiffened extended end-plate specimens, especially at higher interstorey drift angles

Effect of Web Holes and Bearing Stiffeners on Flexural-Shear Interaction Strength of Steel Cold-Formed C-Channel Sections

Abstract This paper presents an investigation on interaction equation between the required flexural strength, M, and the required shear strength, V, of cold-formed C-channels with web holes and bearing stiffeners. The primarily shear condition test was employed to study total 8 back to back lipped C channel sections of 95 and 100 mm depth when bearing stiffeners and circular holes were placed at center and both ends of specimens. The interaction equation were evaluated via Direct Strength Method, DSM, in accordance with the American Iron and Steel Institute for the design of cold-formed steel structural members, AISI 2007. A nonlinear finite element model was developed and verified against the test results in terms of failure buckling modes. It was concluded that the M-V interaction equation for specimens with web stiffeners was conservative where these specimens experienced plastic failure mode rather than local (Msl) or distortional (Msd) buckling mode. Moreover, the results indicated that proposed M-V interaction equation calculated by local buckling strength (Msl) adequately predicted the behavior of specimens with circular web holes

Severe Loading Assessment of Modern and New Proposed Beam to Column Connections

AbstractThe performance of two different steel beam to column connections known as SidePlateTM and a new proposed connection by seismic loading and progressive collapse were investigated in this research. Seismic performance evaluated included consideration of interstory drift angles and flexural strengths based on 2010 AISC Seismic Provisions while investigation of progressive collapse was conducted through satisfaction of acceptance criteria by rotational capacities of the connections provided in UFC 4-023-03 guideline. The results indicated that both SidePlate and the new proposed moment connection were capable of achieving adequate rotational capacity and developing full inelastic capacity of the connecting beam. Also, an excellent performance was exhibited by the connections in terms of keeping the plastic hinges away from the connection and exceeding interstory drift angle of 0.06 rad without fracture developments in beam flange groove-welded joints. Based on results, it was concluded that the SidePlate and the new proposed connection possess sufficient stiffness, strength and ductility to be classified as rigid, full-strength and ductile connections