Journal of Structural Engineering

The paper examines the elastic lateral buckling of simply supported monosymmetric I‐beams under transverse loads. Solutions are obtained in terms of the easily evaluated degree of beam monosymmetry parameter, ρ, and the beam parameter, $\overline{K}\text{.}$ It was found that the moment modification factors of double symmetric I‐beams presently used in design formulas to predict the buckling capacities of monosymmetric I‐beams could be unsafe. Consequently, alternative simple approximate formulas are derived from the energy method, based on the study of the buckled mode shapes of monosymmetric I‐beams. The proposed formulas retain the familiar form of the well‐known solution of beams under uniform moment. Moreover, the paper gives guidelines for achieving the optimum degrees of beam monosymmetry.

Concrete blocks are very often used as breakwater armor units. In order to improve the knowledge of their behavior, some laboratory tests have been performed for three types of blocks. After stating three damage levels, the stability is analyzed and the results shown in figures. Some results from other authors are presented as well, showing similar trends. Some main conclusions are outlined: cubic armor units offer a better performance than parallelopipedic blocks, and smaller slope angles give better stability results, under the tested conditions.

Various creep rupture damage accumulation models are reviewed, and two recent models proposed by Barrett and Foschi are investigated in detail. Two different stochastic load models are then developed. One is for roof snow load, incorporating daily snowfall and melting, and the other is for floor live load. This latter model includes sustained and extraordinary load processes, each with their own occurrences, magnitudes and durations. Simulations are conducted for snow load models calibrated for Boston, Massachusetts, and Buffalo, New York, and for live loads for residential occupancies and office occupancies. In all cases, damage is accumulated for two different damage accumulation models, with parameters evaluated for Douglas fir. Results indicate some sensitivity to damage model, but a consistent pattern for the mean and standard deviation of damage accumulation for both damage models and all load models.

A simple single degree of freedom model of an offshore structure is used to study the effects of the nonlinear drag force on the structural response in random waves. Both random waves with a zero mean velocity and with a steady velocity component are considered. The fluid force is assumed to be given by the relative velocity formulation of the Morison equation which couples the fluid force to the structural response. A new perturbation method is formulated to obtain the mean square response and the response spectral density. This method is shown to be closely related to the method of equivalent linearization and represents a consistent improvement to the linearized solution. Also, numerical simulations are performed to assess the accuracy of the perturbation method.

The design of multifunctional material systems is presented as a multivariable, multicriteria optimization problem, and a formalized methodology which makes no implicit preference, independence, and convexity assumptions is proposed for its solution. The methodology utilizes dynamic programming with Pareto optimization, cluster analysis, and inverse goal programming to identify a subset of acceptable design solutions. It takes into consideration the properties of materials and relates these to various functional requirements of building enclosure. Functional performances under consideration are thermal, resource conservation, structural, economic, and space utilization. An illustrative material system design example is included in detail to show how various conflicting functional requirements can be taken into account simultaneously and generate qualitative and quantitative information to aid the designer in making decisions.

A computer‐aided analytical technique, previously verified by comparison with laboratory test results, is used in a study of local buckling behavior of beam‐columns consisting of W‐shapes. The technique accounts for the effects of flange and web interaction, inelastic behavior, and the presence of residual stresses. The results of an extensive parametric study are presented in graphical form and summarized by simple design curves and corresponding design equations. Included are the effects of varying the web plate slenderness ratios for a wide range of values for plastic design, compact, and noncompact sections. The effects of varying the strain‐hardening modulus and residual stresses are also evaluated. The findings of this study are compared with plate slenderness requirements presently specified for beam‐columns by both U.S. and Canadian codes.

The tensile strength of concrete is receiving an increasing amount of attention since the loading capacity and durability of structures are being studied more thoroughly, and since nonlinear fracture mechanics and numerical methods require a complete stress deformation relation. The theoretical background of the application of the tensile strength of concrete in fracture analysis is given. Test results are presented that were obtained from deformation‐controlled uniaxial tensile tests under static and cyclic loading of lightweight and normalweight concrete. The results have been used to establish material models for finite element calculations. Numerical examples show the usefulness of these models for static and cyclic loading conditions.

The hybrid stress method of finite elements as advocated by Pian and others is reviewed. Whereas variational methods are the most frequently used vehicle for formulating hybrid finite elements, the present communication approaches these techniques via the principle of virtual work. The desire to lend physical interpretation to the various matrices resulting from the hybrid techniques provides the motivation to view these techniques from the standpoint of virtual work. In addition, a hybrid strain technique is proposed. It has the apparent advantage over the hybrid stress technique in that discontinuous stress fields are admitted. Finally, simple examples are presented to demonstrate, in detail, some of the more common hybrid techniques.

A flexural‐torsional buckling theory for circular arches of doubly symmetric cross section is developed. Nonlinear expressions for the axial and shear strains are derived, and these are substituted into the second variation of the total potential to obtain the buckling equation. Closed form solutions are obtained for arches subjected to equal and opposite end moments (uniform bending), and to uniformly distributed radial loads (uniform compression), and for circular rings subjected to uniformly distributed radial loads. The results are compared with previous solutions.

The need for providing long spans over large stretches of water has prompted a new bridge system being proposed. Called the “multispan balanced suspension bridge,” it consists of a number of main spans similar to those of a classical suspension bridge but with its cables anchored at the top of a braced tower, which in turn, is supported on a novel pier of cylindrical shape. The key features of its design and construction are discussed. An example demonstrates the effectiveness of the new bridge system.

Cyclic load behavior of X‐bracing with welded connections is investigated. Six full‐scale specimens made from single and double angles of A36 steel were tested under quasi‐static cyclic loading. The specimens were designed according to current design procedures and code requirements. The main parameters of the study are: (a) mode of buckling; (b) interaction between the two diagonals; (c) slenderness ratio; and (d) width‐thickness ratio of the angle legs. The general cyclic behavior and modes of failure of the specimens are presented. Based on observations of the behavior of test specimens, recommendations are given for the seismic design of angle X‐bracing with welded connections.

Post‐tensioning can be utilized to increase the flexural strength of beams in single‐span, composite steel beam and concrete deck bridges, even when only deficient exterior beams are post‐tensioned. Distribution of the axial forces and moments caused by eccentric post‐tensioning of the deficient beams must be considered in the design of the strengthening system, however. Finite element models, verified with laboratory and field testing, are used with multiple linear regression to develop design equations for force and moment distribution fractions for four‐beam bridges. The design equations can be used easily by practicing engineers and provide the basis for a strengthening design methodology.

A procedure for estimating damage to window glass under fluctuating wind load conditions is illustrated. Applications of the procedure to damage estimation for panels of integer aspect ratio in the range 1 < ar < 4 are presented. The damage function values overlapped for all panels tested; the critical points appeared to be in the corners as long as the flow distribution over the panels is assumed to be uniform over the surface of the panels.