Analysis of timber frames with localized nonlinearities

Distributed plasticity analysis of steel frame structures comprising non-compact sections

Application of “advanced analysis” methods suitable for non-linear analysis and design of steel frame structures permits direct and accurate determination of ultimate system strengths, without resort to simplified elastic methods of analysis and semi-empirical specification equations. However, the application of advanced analysis methods has previously been restricted to steel frames comprising only compact sections that are not influenced by the effects of local buckling. A concentrated plasticity formulation suitable for practical advanced analysis of steel frame structures comprising non-compact sections is presented in this paper. This formulation, referred to as the refined plastic hinge method, implicitly accounts for the effects of gradual cross-sectional yielding, longitudinal spread of plasticity, initial geometric imperfections, residual stresses, and local buckling.

This paper examined the use of the dynamic magnification factor in the analysis of framed structures. It is a method of practice in dynamic analysis of structures to magnify static response by a dynamic magnification factor in order to obtain the equivalent dynamic response. This method has been applied to the dynamic analysis of many structures including bridges and some country’s codes of practice made specifications in respect of the dynamic magnification factor for the analysis and design of various types of structures subjected to dynamic excitation. The suitability of this method to the dynamic analysis of frames was investigated in this paper by carrying out static and dynamic analysis of four frames using the flexible frame model and the stiffness formulation. Dynamic responses were first obtained by direct analysis as solutions to the set of equations governing the motions of the frames and secondly by the magnification of the static responses using the dynamic magnification factors. By comparing the results obtained in both methods it was inferred that the practice of magnifying static responses to obtain their dynamic equivalents in frame analysis gives correct results only in the case of deflections and not in stresses. Finally, this practice should de discouraged or limited only to the case of deflections in the dynamic analysis of framed structures.

An efficient stochastic finite element method is proposed for the reliability analysis of nonlinear frame structures using the first-order second-moment reliability method. The assumed stress-field approach is used in computing nonlinear structural responses and the corresponding response gradients. Both geometric and material nonlinearities of structures are considered. The flexibility of a connection is represented by its moment-relative rotation relationship. Emphasis is placed on the comparison of the reliability indexes of linear structures, nonlinear structures, and nonlinear structures with flexible connections. Both the strength (combined axial compression and bending) and serviceability (deflection) limit states are considered. For stability-related structures, nonlinearity has a considerable influence on the structural reliability, and the reliability will be very different when the flexible connections are taken into consideration. The method is verified using the Monte Carlo simulation technique. The applicability, accuracy, efficiency, and robustness of the method are verified with the help of an example.

Efficiency of dynamic relaxation methods in nonlinear analysis of truss and frame structures

A time-domain spectral element method with C1 continuity for static and dynamic analysis of frame structures

An energy balancing strategy for solution of combined geometrical and material nonlinearity problems

This paper investigates the influence of strain rate effect on the seismic performance of Reinforced concrete (RC) frame structures subjected to far-field and near-field ground motions. An approach for the nonlinear dynamic analysis of RC frame structures considering the strain-rate sensitivity of concrete and reinforcing steel materials is proposed and its effectiveness is validated by the experimental data of RC columns under dynamic loadings. A non-dimensional index is put forward to reveal the regularities of strain rate under different types of ground motions with various intensity levels. The influences of strain rate effect and input ground motion on the seismic performance of the exemplar RC frame are studied by comparing the seismic responses and fragilities of rate-dependent structural models with those of rate-independent ones. Numerical results indicate that the strain rates in structural members increase with the ground motion intensity and the strain rates induced by the near-field pulse-like earthquakes are higher than those by the far-field and near-field non-pulse-like earthquakes. The global response, critical member response, local damage and seismic fragility are all influenced by the strain rate effect, especially under the near-field pulse-like ground motions. Neglecting the influences of strain rate effect, variations in strain rates of different structural members and inputs of pulse-like ground motions may lead to erroneous seismic performance assessments of RC frame structures.

Analytical model for progressive collapse of RC frame structures subjected to blast loadings

Experimental and numerical analysis of GFRP frame structures. Part 2: Monotonic and cyclic sway behaviour of plane frames

Matrix method for stability and second-order analysis of Timoshenko beam-column structures with semi-rigid connections

Time domain intrusive probabilistic seismic risk analysis of nonlinear shear frame structure

Analysis of framed tube structures of arbitrary sections

An efficient material model was developed for reinforcing steel in reinforced concrete (RC) columns that implicitly incorporates the degrading effects of bar-buckling. Utilizing the beam-on-springs model developed by the writers to characterize a buckling bar in a RC column, a comprehensive parametric study was performed to identify the effects of several important column parameters on the buckling behavior of the longitudinal reinforcement in RC columns. Features of average stress-strain curves of compressively loaded reinforcing bars are summarized. Constitutive relations as functions of critical column parameters were developed for direct use in fiber-section model-based nonlinear analysis of RC structures. Comparison of the numerically simulated global response of experimentally tested RC columns confirm the validity and utility of the proposed material model as a simple and effective way to include bar-buckling effects in inelastic analysis of RC frame structures.

Applications of simplified 3D FE model in seismic analysis for friction-damped posttensioned steel frame structures