Journal of Structural Engineering

The stability of masonry arches with an elastic jointing material is studied by considering the change in the balance of energy associated with possible modes of distortion in the arch configuration. The geometrical constraint on these modes of distortions are studied and the critical state of the arch is formulated and the critical load is analyzed. A simply supported masonry arch composed of three voussoirs is analyzed. Uniformly distributed load and the case where an additional point load is applied to the arch are considered. The implication of the instability to the arch failure is discussed.

A study using finite element analysis was made to determine rational factors for the lateral distribution of live loads on typical composite curved I‐girder bridges. Within practical ranges, variations in girder stiffness and crossframe spacing had relatively small effects on the factors. The central angle per span and the girder spacing had the largest effects identified. Graphs showing the factors as a function of central angle for two representative girder spacings were developed for use with four‐girder bridges. It was also shown that reasonable factors can be obtained from a V‐load modification of the factors for straight bridges given by AASHTO. Such factors tend to agree with the finite element results for the exterior girders, but are conservative for the interior girders. Comparisons are also made with the factors given in AASHTO's Curved Girder Guide Specification.

A nonlinear design method for reinforced concrete framed structures is developed. Both the strength and ductility criteria for reinforced concrete design are simultaneously and explicitly satisfied at the specified service and ultimate load levels. The strain‐hardening effect of high strength reinforcing steel is also included in the design. An optimal design approach is adopted, and the design formulation becomes a nonlinear programming problem that can be solved by suitable mathematical solution algorithms and related computer codes. The design solution includes the set of member cross‐section dimensions and steel percentages for which the members have sufficient plastic moment and rotation capacities at the specified ultimate load level while ensuring adequate serviceability at the specified service load level, and for which the total cost of steel and concrete is minimum. A one‐story two‐bay frame example is presented to demonstrate a practical application of the method.

An approximate method for the analysis of stiffened flange plates, containing circular or square openings and loaded axially, is presented. The method allows for the loss in stiffness of plates by making use of the “effective width” concept. Systematic experiments that have been carried out on smallscale steel models of perforated stiffened plates are reported. The experimental results show that satisfactory prediction of ultimate loads can be obtained by the proposed method.

Thermal stresses are frequently used to camber steel beams or repair damage caused by plastic deformation. A local concentration of heat is applied to part of the structure. The heated steel expands, but expansion is restricted by the surrounding unheated metal or other restraint. Large compressive stress develops and the steel yields, causing permanent deformations. This process is widely used and is known as flame cambering or heat straightening, but the process is not well understood by structural engineers. This paper describes a study which attempts to improve the scientific understanding of the method. It includes a brief historical review and a summary of the effects of elevated temperature on the material properties. An experimental program is then described. The parameters which have the greatest influence on the process are noted, and guidelines for using the method are provided.

A state‐of‐the‐art, three‐dimensional, nonlinear finite element algorithm is developed and used to study piling stresses and pile‐soil interaction in integral abutment bridges. The finite element idealization consists of beamcolumn elements, with geometric and material nonlinearities for the pile, and nonlinear springs for the soil. An idealized soil model (a modified Ramberg‐Osgood cyclic model) was introduced in this investigation to obtain the tangent stiffness of the nonlinear spring elements. Several numerical examples, including results on an existing bridge, are presented. The finite element model and the computer software developed are found to give reliable results.

The results of compression tests of long, welded I‐section columns composed of slender plates of high tensile steel are described. Tests of concentrically loaded specimens are compared with a finite strip nonlinear analysis model for predicting the elastic interaction of local and overall buckling of thinwalled columns. Tests of concentrically and eccentrically loaded specimens are compared with the proposed AISC Load and Resistance Factor Design method for columns with slender cross sections. The column strengths are also compared with those of compact columns of equivalent weight to demonstrate the economies available for columns with slender cross sections.

The type of mild steel, strain hardening, strain aging, and the Bauschinger effect due to strain reversal are shown to have a significant effect on the load capacity of tubular struts. Material and strut tests have been performed on circular tubular sections of 60–65 mm outside diameter and wall thickness 2.5–3 mm. The strut tests have been effectively pin‐ended and have slenderness ratios ranging from 20–150. Struts made from material which has been prestrained in tension have significantly lower load capacities than those made from as‐received material; this reduction is caused by Bauschinger strain (the rounding of the reverse loading stress‐strain curve) and the resulting reduced tangent modulus. The reduction occurs despite increases in material strength owing to strain hardening under the applied tensile prestrain and strain aging with time or temperature since application of the tensile prestrain. Strain aging has a more significant effect than strain hardening in minimizing the strut “load” capacity reductions due to prior tensile prestrain.

The local web buckling capacity of coped beams with various coping details is investigated by using finite element programs. A parametric study was conducted to establish the effects of stress concentration, shear stress, cope length, and cope depth on local web buckling strength. A plate buckling model based on the analyzed results was developed to check for elastic local web buckling in compression flange coped beams. It is found that conventional calculations for bending and shear yielding of the coped region provide a conservative approach for checking inelastic local web buckling. A series of ten full‐scale tests, eight rolled sections and two plate girders, along with four more tests that were taken from another research project are used to study the behavior of coped beams and to check the reliability of the design recommendations. The test results indicate that the proposed design provisions give conservative but reasonable results.

The criterion set by the American Association of State Highway and Transportation Officials (AASHTO) for the design of highway sign support structures is examined. It is shown that this requirement, limiting the maximum dead load deflection of the structure in terms of the depth of the sign, is not a good indicator of the performance of the structure. A design procedure is suggested to replace the existing AASHTO criterion.

A probabilistic assessment of the effect of the importance factor in ANSI A58.1-1982 on the reliability of structures is performed. It is found that the change in reliability for structures within the same ANSI category may vary widely depending on which load combination controls the design. An alternate format for the importance factor, whereby the importance factor is applied to the entire load combination as opposed to just one single load, is also examined. This format, however, is unable to provide uniform changes in the reliability. Importance factors, including importance factors for live load, that would give uniform changes in reliability are proposed.

A method of analysis to determine axial and bending stress distributions in open‐section beams composed of fiber‐composite layers is presented. The method is based on the transformed‐section concept, and the effects of Poisson's ratios and in‐plane shear are taken into account. Numerical results are presented for an I‐shaped cross section with various fiber orientations, and are compared to those obtained from lamination theory (Tsai & Hahn 1980), and the conventional transformedsection method (Heger, Chambers & Dietz, 1982) which neglects the effects of Poisson's ratios and shear coupling.