A Second-Order Inelastic Analysis of Plane Steel Frames Using a Work-Increment-Control Solution Technique

Nonlinear analysis of 3-D steel frames

A plane steel frame is simulated by a truss model. The bars obey uniaxial elastoplastic stress-strain laws. Yield stress and modulus of elasticity are assumed constant up to 300°C and then linearly decreasing up to zero for 900°C. Semi-rigid beam-column connection is represented by a hinge and a bar connecting column and beam; this bar has a small length and properly selected cross-section area and elasticity modulus. Three fire scenarios are considered. Numerical experiments show that heat conduction time in steel is very short and can be ignored; it is enough to assume simplified temperature distributions over the cross-sections. A short computer program, with only about 200 Fortran instructions, is documented, for the step-by-step nonlinear structural analysis of plane truss models of steel frames subjected to fire. Geometrical nonlinearities are taken into account by writing, within each time step of the algorithm, the equilibrium conditions with respect to the deformed truss. The program is applied on a typical steel portal frame. In the output of the application, it is observed that, for temperatures lower than 300°C, influence of fire appears by thermal expansion and additional stresses, as well as by thermal bowing of beams due to temperature gradient over the cross-sections. Whereas, for temperatures higher than 300°C, plastic hinges are gradually formed due to yield stress reduction with temperature, and columns may buckle due to elasticity modulus reduction with temperature. Each of the above two phenomena may lead to a collapse of the portal frame, which is shown, in the analysis, by very large displacements.

Macroscopic modelling of steel frames equipped with bolt-connected reinforced concrete panel wall

Finite element modeling and capacity analysis of post-tensioned steel frames against progressive collapse

Influence of Semi‐Rigid Connections and Local Joint Damage on Progressive Collapse of Steel Frameworks

The structural seismic performance of steel frame-precast steel reinforced concrete (SRC) infill wall with lateral force resisting is analyzed, and the structural strength of steel frame-precast SRC infill wall with lateral force resisting is improved. The structural seismic performance optimization model of SRC lateral force resisting wall based on buckling restrained brace is proposed. Through the finite element simulation software, the seismic performance and response results of ordinary steel frames, buckling restrained braced steel frames and a relatively new type of sacrificial-energy dissipation braced steel frames under earthquake are compared and analyzed to demonstrate the applicability and performance advantages of sacrificial-energy dissipation braced steel frames in the steel frame braced structure system. Under the action of horizontal earthquake, the supporting members experience reciprocating axial tension and compression cycles, which dissipate a large amount of seismic energy input into the structure. Therefore, the buckling restraint support method can be used in the structure to improve the support strength. Under horizontal reciprocating load action of earthquake, the ability to consume seismic energy through self-hysteresis of the brace is poor. Experimental research shows that, the unbalanced force formed in the beam of the frame beam under seismic action will form a plastic hinge at the beam end at both ends of the frame beam. Especially when the brace is buckling unstable and the stiffness of the frame beam is small, the plastic hinge effect at the beam end is significant. This phenomenon may cause damage to the frame beam or even local floor subsidence. The buckling restraint support has a full hysteresis area under axial tension and compression, and its mechanical performance is excellent. It is obviously superior to ordinary steel bracing in energy dissipation capacity and seismic performance. It can accurately predict the bearing capacity of reinforced concrete under strong earthquake, and the energy dissipation distribution is more in line with the requirements of “energy seismic design method”.

The effects of connection flexibility and material yielding on the behavior of plane steel frames subjected to static (monotonic) loads are presented in this paper. Two types of material nonlinearities are considered: flexible nodal connections and material yielding, as well as geometric nonlinearity of the structure. To account for material yielding, a plastic hinge concept is adopted. A flexible connection is idealized by nonlinear rotational spring. Plastic hinge is also idealized by nonlinear rotational spring attached in series with the rotational spring that accounts for connection flexibility. The stiffness matrix for the beam with flexible connections and plastic hinges at its ends is obtained. To illustrate the validity and accuracy of the proposed numerical model, several examples have been conducted.

The major sources of energy dissipation in steel frames with partially restrained (PR) connections are evaluated. Available experimental results are used to verify the mathematical model used in this study. The verified model is then used to quantify the energy dissipation in PR connections due to hysteretic behavior, due to viscous damping and at plastic hinges if they are formed. Observations are made for two load conditions: a sinusoidal load applied at the top of the frame, and a sinusoidal ground acceleration applied at the base of the frame representing a seismic loading condition. This analytical study confirms the general behavior, observed during experimental investigations, that PR connections reduce the overall stiffness of frames, but add a major source of energy dissipation. As the connections become stiffer, the contribution of PR connections in dissipating energy becomes less significant. A connection with a T ratio (representing its stiffness) of at least 0.9 should not be considered as fully restrained as is commonly assumed, since the energy dissipation characteristics are different. The flexibility of PR connections alters the fundamental frequency of the frame. Depending on the situation, it may bring the frame closer to or further from the resonance condition. If the frame approaches the resonance condition, the effect of damping is expected to be very important. However, if the frame moves away from the resonance condition, the energy dissipation at the PR connections is expected to be significant with an increase in the deformation of the frame, particularly for low damping values. For low damping values, the dissipation of energy at plastic hinges is comparable to that due to viscous damping, and increases as the frame approaches failure. For the range of parameters considered in this study, the energy dissipations at the PR connections and at the plastic hinges are of the same order of magnitude. The study quantitatively confirms the general observations made in experimental investigations for steel frames with PR connections; however, proper consideration of the stiffness of PR connections and other dynamic properties is essential in predicting the dynamic behavior.

Development of DDBD for steel MRFs using inelastic response-based seismic lateral force distribution

A hybrid structure constructed by replacing external steel beams and columns in the steel frame (SF) to precast concrete shear walls with insulation (PCSWs) and precast concrete cladding panels (PCCPs, SFPCSW) is proposed in this paper to avoid the problem of columns protruding from walls and PCCPs directly connected with SF. Numerical models of the SF and SFPCSW structures are established in ETABS software based on an 18‐story assembled steel residential building to investigate the seismic performance and collapse resistance capacity of SFPCSW. Time history analysis results show that the SFPCSW exhibits bending‐shearing lateral deformation and has more uniform interstory drift ratios than the SF. Under major earthquakes (i.e., probability of exceedance of 2% in 50 years), the damage of SF is concentrated in stories 1–6; for SFPCSW, the plastic hinges mainly appear in the concrete beams between PCSWs at each story, and the damage in PCSWs and the internal frame is small. Using pinned connections between the steel beam and PCSW reduces the structural lateral stiffness and increases the earthquake load carried by the internal frame. The incremental dynamic analysis results show that the SF and SFPCSW have similar collapse resistance capacities.

A Welded Flange Plate (WFP) connection consists of top and bottom flange plates that are fillet welded to the flanges of a beam and are complete joint penetration groove welded to a column flange. Four WFP design examples including various beam sizes, beam lengths, and/or assumed plastic hinge locations are presented in this paper. In these design examples, the relationships among the following three factors are in-vestigated: the assumed location of the plastic hinge, the probable peak flexural demand at the end of the beam, and the required length of the flange plates for the WFP connections. Nonlinear static finite element analyses considering both the material and geometric nonlinearities are also carried out for these examples to verify the actual location of the plastic hinge as well as the relationship between the actual location of the plastic hinge and the length of the flange plates used for the WFP connections.

This paper presents an implementation of Eurocode load cases for discrete global optimization algorithm for planar and space structures based on the principles of finite element methods and genetic algorithms.The final optimal design is obtained using IPE sections chosen as feasible by the algorithm, from the available steel sections from industry, used for ease of comparison with benchmarks.The algorithm is tested on several planar steel frames and a truss from the literature, with good results.

Optimized seismic design of planar and spatial steel frames using the hybrid learning based jaya algorithm

In the seismic design of steel frames, beam-to-column joints can be designed either as full strength joints, forcing the location of the plastic hinges at the beam ends, or as partial strength joints which have to dissipate the seismic input energy. Seismic codes provide specific design criteria for full strength joints, but there are no detailed recommendations dealing with partial strength connections. Therefore, in this paper, by means of a simplified model, such as a SDOF system, the requirements which partial strength joints have to possess, for designing steel frames characterised by seismic performances equivalent to those of steel frames with rigid full strength joints, are pointed out. Successively, starting from the above requirements, a new method for designing seismic resistant steel frames with extended end plate connections leading to the complete definition of the geometrical and mechanical parameters of the joints is proposed.

This paper presents the characteristics of the ultimate behavior of steel cable-stayed bridges through considering various geometric parameters. Steel cable-stayed bridges show complex ultimate behavior, because of their geometric characteristics and various nonlinearities. In this study, the patterns of the ultimate behavior of steel-cable stayed bridges under the critical live load case are classified. In addition, the effects of various geometric parameters on the ultimate behavior, such as cable-arrangement type, height of the girder and mast, and area of the stay cables, are studied. For rational analytical research, the analysis method suggested in the previous paper, Ultimate behavior of steel cable-stayed bridges-I. Rational ultimate analysis method (Kim et al., 2016), is mainly used. Using the analysis method, the main geometric and material nonlinearities, such as the cable sag effect, beam-column effect of the girder and mast, large-displacement effect, girder-mast-cable interaction, and gradual yield effect of steel members, are reflected and considered in the analytical research. After the analytical study, the characteristics of the change of ultimate mode and load carrying capacity are investigated, with respect to the change of various geometric parameters.