A Methodology for Platform Collapse Analysis Based on Linear Superposition

A numerical strategy for the simulation of structural modifications by virtual distortions is proposed. Two cases of structural modification are considered: the first concerns modifications of material distribution, and the second modifications of local constitutive relations (e.g. unilateral constraints for stresses or deformations). A formaulation of the fundamental equations of the simulation method is presented. These equations are applicable to the general structural modification problem of a truss‐like structure. Then numerical algorithms which refer to particular applications, such as progressive collapse analysis or the analysis of structures with gaps, are discussed.The versatility of the method is illustrated with a number of examples, and the computational advantages of structural modification by the virtual distortion method are discussed.

The seismic performance of braced steel frame was simulated by the finite element software ANSYS based on the passive energy-dissipation under the low-cycle repeated load and the time-history analysis under seismic load for the energy-dissipation braced steel frame structure, no-brace steel frame structure, and conventional braced frame structure. The energy dissipation and seismic performance of three kinds of frame were compared, the results show that the energy-dissipation braced structure can produce strong energy-dissipation control force to enhance energy dissipation capacity of the whole structure significantly, and weaken the seismic load of the main frame. It follows that the energy-dissipation braced steel frame can achieve the purpose of energy dissipation for structure, and has good seismic performance.

In order to study the mechanical characteristics of the linear switched reluctance motors (LSRMs), modal analysis and linear static structure analysis of a LSRM is investigated in this paper. Basic theories of modal analysis and linear static structure analysis are stated. The structure of the LSRM is illustrated. And the modal analysis and linear static structure analysis by finite element method are demonstrated based on ANSYS workbench. The first six natural frequencies with the corresponding mode shapes and the deformation of the LSRM are obtained. The results show that the first six natural frequencies of the LSRM range from 2244.7 Hz to 4033.1 Hz, the deformation of the LSRM is within 0.0020546 mm under the largest normal force, and the easiest deformation part of the LSRM is the mover platform. The results verify that the mechanical design of the LSRM is reasonable.

Matching relationship of low-cycle fatigue life and fatigue design method of concentrically braced frames with H-section steel

The properly constructed buckling restrained braces (BRBs) usually have good ductility and energy dissipation capacity and therefore can be used in braced steel frames. However, large residual plastic deformation of the BRBs deteriorates their resilience capacity and hence results in large residual deformation of the buckling restrained braced steel frames (BRBFs) under large drifts. To reduce the residual deformation of BRB while keeping good ductility and energy dissipation capacity, a new self-centering buckling restrained brace (SCBRB), letting both BRB part and self-centering part work in parallel, is proposed. The self-centering capacity of SCBRB is provided by a combination of pre-compressed disc springs, which provides restoring forces and facilitates reduction of the residual deformation of the BRB. The BRB is composed of a core steel plate brace, a restraining member formed by the circular steel tube filled with mortar, and debonding materials between them. By quasi-static tests, one self-centering buckling restrained brace specimen (SCBRB) and one pure BRB specimen were tested to mainly examine the constructional details and hysteretic behavior of SCBRB. The material and configuration details of core steel plate brace in both the SCBRB and the pure BRB are the same for comparison. The test results show that, compared with the pure BRB which still exhibits large residual deformation, the SCBRB presents a flag-shape hysteretic performance and its residual deformation decreases significantly. The hysteretic curves of both the SCBRB and the pure BRB are stable before tension fracture of plate brace due to low cyclic fatigue, and the other components remained intact.

Many historical events have shown that, after an earthquake, fire may be triggered by seismic‐induced rupture of gas piping, failure of electrical systems, etc. The current engineering design methods still ignores many aspects of multi‐hazard and in particular fire following earthquake (FFE) analysis. In this respect, the aim of this paper is to study the behaviour of a braced steel frame subjected to seismic‐induced fire. In particular, FFE numerical analyses were conducted on a four‐storey three‐bay braced steel frame with concentric bracings. The results of the numerical analyses served to design the FFE tests performed on unprotected and protected columns belonging to the bracing system. The fire tests after the seismic event were carried out by considering the effects of the surrounding seismically damaged structure. Results of the FFE tests on unprotected columns are reported along with the numerical model calibration.

Design of an eccentrically buckling-restrained braced steel frame with web-bolted replaceable links

Seismic fragility functions for RC As-built and eccentric steel brace frames

This paper deals with the cyclic elastoplastic analysis and stability evaluation of steel braces of hollow sections subjected to axial tension and compression. The inelastic cyclic performance of cold-formed steel braces of circular and box hollow sections is examined through finite element analysis using the commercial computer program ABAQUS. First some of the most important parameters considered in the practical design and ductility evaluation of steel braces of tubular hollow sections are presented. Then the details of finite element modeling and numerical analysis are described. Later the accuracy of the analytical model employed in the analysis is substantiated by comparing the analytical results with the available test data in the literature. Finally the effects of some important structural and material parameters on cyclic inelastic behavior of steel braces are discussed and evaluated. INTRODUCTION Steel braced frames are one of the most commonly used structural systems because of their structural efficiency in providing significant lateral strength and stiffness. The steel braces contribute to seismic energy dissipation by deforming inelastically during an earthquake. The use of this type of construction indeed avoids the brittle fracture found in beam-to-column connections in moment resisting steel frames that occurred in the Northridge earthquake in 1994 and the Kobe earthquake in 1995 (ASCE 2000, IGNTSDSS 1996). However, careful design of steel braced frames is necessary to avoid possible catastrophic failure by brace rupture in the event of a severe seismic loading. The current capacity design procedure adopted in most seismic design steel specifications (AISC 1997, CAN-CSAS16.1 1989), for concentrically braced frames requires yielding in the braces as primary members, whereas the secondary members of the frame should remain elastic and hence carry forces induced by the yielding members. The transition from current perspective seismic codes to performance-based design specifications requires accurate predictions of inelastic limit states up to structural collapse. The cyclic behavior of steel brace members is complex due to the influence of various parameters such as, material nonlinearity, structural nonlinearity, boundary condition, and loading history. The material nonlinearity includes structural steel characteristics such as, residual stresses, yield plateau, strain hardening and Bauschinger effect. The structural © 2008 ASCE 18th Analysis and Computation Specialty Conference Copyright ASCE 2008 18th Analysis and Computation Specialty Conference nonlinearity includes parameters such as, brace slenderness parameter, cross-section slenderness, width-to-thickness ratio of the cross-section’s component elements (or radius-to-thickness ratio of circular hollow sections), and initial out of straightness of the brace. The complex behavior results in various physical phenomena, such as, yielding in tension, buckling in compression, postbuckling deterioration of compressive load capacity, deterioration of axial stiffness with cycling, and low cycle fatigue fractures at plastic regions. Steel braces can be designed to resist only tensile forces, or to resist both tensile and compressive axial forces. Recent earthquakes and experiments have shown that the tensioncompression braces provide better performance under cyclic loading (during an earthquake) as compared with the tension-only braces having almost no compressive strength. Under severe earthquakes, the braces are subjected to cyclic axial forces and they are allowed to undergo compression buckling or tensile yield to dissipate the imposed energy while columns and collector beams respond elastically. Therefore, understanding the behavior of the bracing members under idealized cyclic loading is an important step in the careful design of steel braced frames. This paper deals with the cyclic elastoplastic analysis of steel braces. The most important parameters considered in the practical design and ductility evaluation of steel braces of tubular hollow sections are presented. The cyclic elastoplastic performance of steel braces is examined through finite element analysis using the computer program ABAQUS. The accuracy of the analytical model employed in the analysis is substantiated by comparing the analytical results with the available test data in the literature. The effects of some important structural and material parameters on inelastic cyclic behavior of steel braces are discussed and evaluated.

In this study, two geometrically identical multi-storey steel buildings with different lateral load resisting systems are structurally analyzed under same earthquake conditions and they are compared with respect to their construction costs of their structural systems. One of the systems is a steel structure with eccentrically steel braced frames. The other one is a RC wall-steel frame system, that is a steel framed structure in combination with a reinforced concrete core and shear walls of minimum thickness that the national code allows. As earthquake resisting systems, steel braced frames and reinforced concrete shear walls, for both cases are located on identical places in either building. Floors of both buildings will be of reinforced concrete slabs of same thickness resting on composite beams. The facades are assumed to be covered identically with light-weight aluminum cladding with insulation. Purpose of use for both buildings is an office building of eight stories. When two systems are structurally analyzed by FEM (finite element method) and dimensionally compared, the dual one comes up with almost 34% less cost of construction with respect to their structural systems. This in turn means that, by using a dual system in earthquake zones such as Turkey, for multi-storey steel buildings with RC floors, more economical solutions can be achieved. In addition, slender steel columns and beams will add to that and consequently more space in rooms is achieved.

OpenSees is an open-source, object-oriented software framework developed at UC Berekeley. The OpenSees framework has been recently extended to deal with structural behaviour under fire conditions. This paper summarizes the key work done for this extension and focuses on the application of the developed OpenSees to study the influence of fire scenarios and bracing system on the resistance of steel frames against fire-induced progressive collapse. Single- and multi-compartment fire scenarios are applied. Additional horizontal and vertical restraints are applied to the frame to simulate the braced steel frame. A parametric study is carried out to find the fire-induced progressive collapse mechanisms of steel frames under various fire scenarios and restraining conditions. The collapse mode of frames is in the form of lateral drift and downward collapse of frames. It is proved that these two collapse nodes can be resisted by applying lateral and vertical restraint on the frame, respectively. The combination of two restraints has a better resistance effect.

Many traditional and Artificial Intelligence techniques have been projected for reactive power dispatch to advance voltage stability of the system. This paper presents particle swarm optimization (PSO) approach for system parameters development and optimal reactive power dispatch. The transformers tap changers, Generator exciters, switchable VAR sources/Static VAR compensators (SVC) are used as control variables for advancement of system parameters and voltage stability. The suggested methodology is based on the minimization of sum of the squares of L-index value at all load buses. The advanced PSO Algorithm is tested on an IEEE Equivalent New England 39-bus system. The performance of PSO is compared with conventional Linear Programming (LP) method and outcomes are presented for illustration purpose. The correctness of voltage stability is measured in terms of system parameters.

A study has been carried out on a sample of 102 Iraqi local dell and their offspring for the period 2021-2022 to study the growth prediction of lambs through the production of milk and its main components, the results obtained from this study after adjusting for factors are as follows., there is a positive relationship between weight gain at weaning age and at 6 months and an increase in the percentage of protein in milk at a significant (P≤0.05)and (P≤0.01) respectively. The regression coefficient of weight gain for age at weaning and age at 6 months on maternal milk production was by 3.208 and 3.821 Kg, respectively, at a significant (P≤0.05).in this study applied some exponential equation according to the simple non- linear structure analysis with calculation and recording of the Determination coefficient R2 of growth in domestic goats the results showed that the relationship resulting from the regression of the weight at age of 6 months on the weight at weaning according to the formula WWTᶺ=a + bBWT² is the best according to the coefficient of determination which was 0.58. We conclude that daily milk production and the ratio of protein and fat of milk can be used to forecast development between the age of weaning and the age of six months, and that the use of nonlinear equations can produce useful findings for describing growth curves, particularly between those two ages

Structure/load-dependent vectors for linear structural dynamic analysis

A structure/load-dependent vectors method is developed for large-scale, linear structural dynamic analysis with complex loadings. The dynamic solution vectors are used as starting vectors so that both structure and load characteristics are included in the basis vectors. This method requires less vectors for the same accuracy, especially for structures that have external concentrated masses. Numerical results are obtained to demonstrate the advantages of the present method over other reduction methods.