Limit State Analysis Research Articles

Structural reliability analysis method for viscoelastic members

The structural performance of viscoelastic materials may be strongly dependent on the temporal characteristics of the applied loadings. This time dependence cannot be properly considered in structural reliability studies using the conventional analysis techniques such as first-order, second-moment methods. However, Monte Carlo simulation can be adapted for this purpose provided time-dependent stochastic load models and stress-strain models are available. In this paper, a structural reliability analysis method is presented which includes both time-dependent structural loads and material response. The application of the method to a reliability analysis of a deflection serviceability limit state is presented for illustration.

Interfacing systems LOCA (ISLOCA) component pressure capacity methodology and typical plant results

A proposed methodology and sample results from several plant investigations are presented for evaluating the expected pressure capacity of nuclear power plant components which could potentially be subjected to Interfacing Systems LOCA (ISLOCA) conditions. Included in this evaluation are tanks, heat exchangers, filters, pumps, valves and flanged connections for systems designed for relatively low-pressure, low temperature conditions, but which could possibly be exposed to reactor coolant conditions, either through human error or isolation valve failures. The probabilities of failure, as a function of internal pressure, are evaluated as well as the variabilities associated with them. Leak rates or leak areas are estimated for the controlling modes of failure. Pressure capacities for the pipes and vessels are evaluated using limit-state analyses for the various failure modes considered. The capacities are dependent on several factors, including the material properties, modeling assumptions, and the postulated failure criteria. The failure modes for gasketed-flange connections, valves and pumps do not lend themselves to evaluation by conventional structural mechanics techniques and evaluation must rely primarily on the results from ongoing gasket research test programs and available vendor information and test data.

Ultimate Limit States of Space Reticular Structures with Random Behaviour Elements

In this paper we will carry out an analysis of the ultimate limit state of space reticular structures built of bars with random imperfections of a geometrical kind. Reference is first made to structures that are optimized through an analytic procedure based on the minimization of the volumes of those bars, which, in collapsing, transform the structure into a mechanism. An analysis of simulated structures is hence carried out. Such an analysis allows to define the distribution of collapse multipliers, from which it is possible to determine the collapse multiplier of the structure.

Computer aided analysis of reinforced concrete columns subjected to axial compression and bending—I L-shaped sections

Numerical investigations on the strength of L-shaped short reinforced concrete columns subjected to combined axial load and bending were undertaken for the purpose of providing design aids for structural engineers. The use of a computer lends itself naturally to the solution of the problem which generally requires an iterative process. Therefore, an attempt has been made in this paper to computerize the analysis procedure for L-shaped sections and in the accompanying paper (part II) ‡ for T-shaped column sections. The ACI-318, CP-110 and IS-456 codes presented design aids only for square/rectangular and circular columns. Apparently this study constitutes the first to present the interaction curves for L-shaped and T-shaped column sections with the limit state analysis.

Towards a Capacity-Design Assessment Procedure for Reinforced Concrete Frames

A two-level seismic assessment procedure for reinforced concrete frame buildings is presented. The intent of the procedure is to determine the risk, in terms of annual probability of exceedance, associated with two limit states, namely a serviceability limit state and a survival, or ultimate, limit state. The serviceability limit state is determined by elastic response calculation, but the survival limit state analysis attempts to identify the strength and ductility of the critical collapse mechanism, and hence its probability of exceedance by comparison with reference spectra. The basis for identifying the critical collapse mechanism is a modified form of capacity design principles which allows local element failure provided overall structural integrity is not jeopardized.

Upper bound to bearing capacity of layered soils

An approach to the problem of flat punch indentation into the Mohr-Coulomb layered half-space has been developed, based on the kinematical approach of limit analysis. A kinematically admissible plane-strain failure mechanism for a typical two-layer system is presented. The ultimate bearing capacity for strip footings obtained from the proposed approach compares well with the experimental data available in the literature. Key words: bearing capacity, limit state analysis, layered soil, strip footings.

Limit State Analysis of Masonry Domes

Renaissance ogival domes of unreinforced stone masonry can be analyzed as structures of rigid material with no tensile strength. Solutions can be obtained for the static equilibrium of the structure; the results represent an extension or variant to membrane shell theory. A limiting shell thickness is found at which a kinematic collapse mechanism develops. The limit state analysis also identifies the role of hoop stress in permitting the construction of such a shell without centering. The analysis has its counterpart in a study published in 1742, that being the first modern structural analysis. The analysis procedure shows the clear relation between geometry (shell shape) and internal forces.

Serviceability Limit State Analysis of Circular and Annular Cracked Concrete Sections

A method is presented for a serviceability limit state analysis of circular and annular cracked, partially prestressd, or nonprestressed concrete sections. The cross section can be reinforced with combination of prestressed and nonprestressed reinforcement. (The corresponding ultimate limit state problem was discussed in a previous paper.) The method is suitable for computers.

Reliability analysis of deflection — drift limited structures

Deflections, structural deteriorations, floor vibrations and other serviceability criteria are naturally random with respect to their magnitudes. A realistic analysis of serviceability limit states therefore requires the consideration of risk of unserviceability. Isosafety functions are proposed here for analyzing the influence of different parameters on the reliability levels with respect to limit states associated with deflection and drift conditions.

Strength of Steel Frames Using Partial Composite Girders

This study investigates the behavior of composite concretesteel girders and evaluates their role in wind bents of unbraced Type 2 steel building frames. A nonlinear inelastic computer program is developed to perform a limit state analysis of partial composite girders and provide the nonlinear bending characteristics needed for collapse analysis of frames. The results indicate that composite girders do not increase frame strength compared to equivalent designs using noncomposite girders. It is concluded that the current design method used for Type 2 design with composite girders in a wind bent will result in frames with an adequate, though not excessive, level of safety for typical frames less than 10 stories in height.

Limit State Analysis of Submerged Concrete Cylinders

Limit State Analysis of Submerged Concrete Cylinders

Optimum Design of Horizontally Curved R/C Slabs

A method for selecting the optimum design variables in the design of horizontally curved two-way reinforced concrete floor slabs is presented. The slab panels are assumed to be uniformly loaded by characteristic dead and live loads and supported on all sides by rigid boundary supports. The optimum values are selected from within the feasible region in the design space defined by the limit state requirements of CP 110 (British Standard Code). Cost of material is treated as the objective function and is optimized subject to the bending behavior and side constraints imposed by the limit-state requirements. For the ultimate limit-state analysis, the bending moments in the curved slab panels are determined from the linear-elastic theory of sector plates. Nonlinear programming problems of high degree are generated by setting the effective depth and the transformed steel ratios as the design variables in both the objective function and the constraints. The sequential linear programming is introduced as an analytical method of nonlinear optimization. The optimum design variables are then determined.

Concrete Sections Unoeb Biaxial Bending

The general cases of cracked reinforced or prestressed concrete sections under axial load and biaxial or uniaxial bending in the serviceability and ultimate limit states have been treated in four previous papers. This paper is limited to serviceability limit state analyses of cross sections without prestressing or axial load and with trapezoidal or triangular compression zones. The effect of shrinkage is not covered. The approach suggested in this paper is simpler and about 50 times faster than the general method. The analysis may be carried out without the aid of a programmable computer. However, such a computer facilitates the calculation considerably. The concrete on the tension side of the neutral axis is assumed to be unable to transfer stresses, so the shape of this part of the cross section has no influence on the analysis. The reinforcement can be distributed arbitrarily over the cross section.

Serviceability Limit State Analysis of Concrete Sections with Circular Holes Under Biaxial Bending

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The Analysis of Failure of a Normally Consolidated Clay Foundation Under Embankment Loading

In this research an attempt is made to derive the following two approaches of arithmetic methods of evaluating ultimate bearing capacity of normally consolidated clay foundation subject to partial loading such as embankment with finite width. The two approaches are as follows: (1) Finite element deformation analysis of elasto-plastic clay foundation including consolidation behavior, and (2) Limit state analysis by rigid plastic finite element method. In the former analysis, the stiffness factor of clay foundation in terms of effective stresses is newly introduced, from which the definition of total failure of clay foundation is freshly made. In the latter analysis, stress induced anisotropy of undrained shear strength of clay is newly introduced so that the consistency be held between the limit analysis and load deformation analysis. Main conclusions obtained in the present study are as follows:(1)The solution of rigid plastic finite element analysis is shown to be very close to the solution obtained in a deformation analysis as far as undrained condition is concerned.(2)The effect of partial drainage expected during gradual load application is found to be less than 30% of undrained bearing capacity when the loading rate is within the range commonly used in engineering practice. The solution of rigid plastic finite element analysis is shown to be very close to the solution obtained in a deformation analysis as far as undrained condition is concerned. The effect of partial drainage expected during gradual load application is found to be less than 30% of undrained bearing capacity when the loading rate is within the range commonly used in engineering practice.

Experimental Analysis of Limit States in a Six-Panel Waffle Flat-Plate Structure

Experimental Analysis of Limit States in a Six-Panel Waffle Flat-Plate Structure

Serviceability Limit State Analysis of Cracked, Polygonal Concrete Sections under Biaxial or Symmetric Bending

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Serviceability Limit State Analysis of Cracked, Partially Prestressed, or Reinforced Concrete Sections under Symmetric Bending

Serviceability Limit State Analysis of Cracked, Partially Prestressed, or Reinforced Concrete Sections under Symmetric Bending

Columns with End Restraint and Bending in Load and Resistance Factor Design

In this paper, the state-of-the-art design philosophies with particular emphasis on the Load and Resistance Factor Design (LRFD) format are discussed. The background and relevant development of the design methods relating to columns and beam-columns are presented. LRFD is a limit-state design method. A valid limit-state analysis and design of structures or structural members requires more understanding of structural behavior and more demand on structural analysis techniques. For example, in the AISC/LRFD Specification, a direct second-order analysis of the structure to determine the maximum design forces in the member is recommended. Furthermore, an extensive use of stability theory is employed in the development of the specification equations.

Limit State Analysis of Arch Segments

A simple, yet useful limit state analysis is performed on a statically determinate arch segment. A failure mode is assumed and relationships governing the kinematic failure mechanism are discovered using statics. The fracture is observed to occur at the midpoint and a minimum thickness to length ratio is found to be 0.150 to insure against brittle failure. The least desirable position of the arch segment is at 52° with respect to the horizontal.