Journal of Structural Engineering

This paper summarizes the results of four test series on reinforced concrete beam‐column‐slab connections. The method of force distribution in these connections is discussed. A comparison of the results, explanations for differences in behavior, and design recommendations are given.

A large proportion of structural failures are due to human error in the design stage of a structural engineering project, and many of these failures could have been averted if there had been adequate design checking. Results are reported herein from surveys investigating the effectiveness of three typical design‐checking processes: self‐checking, independent detailed design checking, and overview checking. Following a review of current work in this area, appropriate mathematical models, which examine the effects of error magnitude, time, and experience, are proposed for each design checking process. These are compared to the limited data obtained from the surveys. Although preliminary, the results have interesting implications for practitioners.

The Roebling Delaware Aqueduct Bridge was designed and erected by John A. Roebling, designer of the Brooklyn Bridge, in 1850 to carry the Delaware and Hudson Canal over the Delaware River between Minisink Ford, New York, and Lackawaxen, Pennsylvania. The canal was abandoned in 1898, and the aqueduct was converted into a toll bridge about 1900. Due to deterioration and other damage, it was closed to vehicles in 1977 and reopened in 1987 after restoration to accommodate vehicles up to 10 tons. Future plans call for the addition of trunk walls and pedestrian “tow paths” walkways. Because the original water load was a constant uniform load across all the spans and the lighter traffic load consists of moving nonuniform loads, sliding of the cables on top of the saddles and excess deflection of the deck under moving concentrated loads were two of the major concerns. These were overcome by the addition of two stiffening trusses in each span with 3‐in. overall thicknesses and hidden within the future trunk walls and by the use of a heavy concrete deck.

This study presents the characteristics of elastic and plastic designs, focusing on their dependence on buckling constraints and structural configurations. The paper evaluates the cross‐sectional properties of beams and columns which are optimized for maximum load, for elastic and plastic designs respectively. Using those optimal properties, two typical examples of steel building and bridge structures, of which structural configurations are in clear contrast, are optimized by elastic and plastic designs. Some practical implications are given based on the results.

The objective of this paper is to introduce the detailed static analysis of continuous steel girders prestressed by high‐strength steel cables. The prestressed‐steel girders having either simple or continuous spans are indeterminate structures. The application of loadings to the girder after the prestressing process is performed (live loads, superimposed dead loads, etc.) induces an increased prestressing force to the girder. The degree of indeterminancy of the girder is increased. The compression effect of prestressing reduces the negative bending moments at the internal supports of continuous‐span girders. The detailed analysis is demonstrated. The flexibility method is the basis for the analysis of the incremental prestressing force and the bending moments at the middle supports which constitute the unknowns of the indeterminate structure. The flexibility coefficients are computed by the virtual work method. The given equations may be computerized for the analysis of girders having uniform cross section along the girder.

The linear responses of idealized intake‐outlet towers to harmonic ground motion are presented for a range of parameters characterizing the tower geometry, surrounding and inside water, and foundation‐soil system. Based on these frequency response functions, the effects of tower‐water interaction and tower‐foundation‐soil interaction on the response of towers are identified and shown to be significant in many cases.

The dynamic response of Briones Dam Intake Tower to Taft ground motion is presented for various cases: rigid and flexible foundation rock, with and without water. Study of these response results demonstrates that the earthquake response of this tower is increased because of hydrodynamic effects and decreased as a result of tower‐foundation‐soil interaction. It is also demonstrated that the earthquake response of this tower can be computed to a satisfactory degree of accuracy by considering the contributions of only the first two natural vibration modes. This observation provides a basis for developing a simplified analysis procedure suitable for practical application.

This paper describes a knowledge‐based model of the structural component design process. The primary knowledge source is a design standard, which is a collection of requirements limiting the behavior of structural components. Several additional knowledge sources are applied to design a structural component: structural and material behavior relationships, optimization methods, and design expertise. Because the model treats the design standard as a separate knowledge source, it can produce structural component designs that conform to any design standard. Standard‐independence provides robustness (i.e., changes in the design standard do not affect the way in which the knowledge is used) and flexibility (i.e., any design standard may be used as a knowledge source).

A statistical study of yield spectra with high damping is presented. A set of 10 earthquake records is used as input ground motions for elastoplastic single degree of freedom systems with damping ratios from 10% to 50%. Ductility ratios considered range from 1 to 6. From the statistics of the response spectra, parameters for constructing design spectra are derived and procedures described. Average effect of increasing damping on spectral response is presented.

An experimental program was conducted to study the behavior of brick masonry under cyclic compressive loading. The envelope stress‐strain curve, the common point curve, and the stability point curve were established for brick masonry loaded both perpendicular and parallel to the bed joint. A general analytical expression is proposed for these curves which is found to provide reasonable fit with the experimental data. The variation of lateral strain with axial strain is also discussed.

An ultimate limit‐state criterion is developed for the seismic reliability assessment of single‐story structures. This criterion is: When the structural precollapse energy absorption capacity is greater than the earthquake energy input, the structure can survive. Thus, the load effect is the maximum earthquake energy input which the building is expected to encounter during its lifetime. For the determination of this load effect, the seismic hazard potential as well as the dynamic characteristics of the structure and the ground motion are considered in this study. The seismic hazard term is determined from seismic source and attenuation models, and the dynamic characteristic term is determined from the energy input spectrum of inelastic single‐degree‐of‐freedom (SDOF) systems. The uncertainty involved in these terms is also investigated in order to calculate the failure probability.

The paper addresses the problem of efficiently sizing steel frameworks to account for nonlinear load‐displacement (P‐Δ) effects. The design objective is to produce a minimum weight structure while simultaneously ensuring acceptable levels of combined first‐order and second‐order displacements and stresses in accordance with the governing steel design code. Conventional fabrication conditions are imposed and members are sized using commercially available standard sections. The design method involves coordinated use of second‐order elastic analysis, sensitivity analysis and optimization techniques within an iterative synthesis process. For a given trial design of the structure, second‐order elastic analysis and first‐order sensitivity analysis are together employed to approximate the performance constraints on displacements and stresses as explicit linear functions of the member‐sizing variables. Optimization techniques are then applied to find an improved (lower weight) design for the structure, which satisfies all performance constraints. The formulation of the design problem is updated for the new design and the synthesis process is repeated until convergence to the least‐weight structure occurs. The synthesis process is implemented in a comprehensive computer system developed for the least‐weight design of steel frameworks. The designs of two building frames are considered from a variety of viewpoints to illustrate both the features of the design method and some underlying issues related to second‐order design.

Spectators and participants performing various maneuvers produce transient and harmonic dynamic occupant loads. Individuals and groups performed prescribed impulsive and continuous actions on a large force platform. Periodic loads are modeled with Fourier Series and exponentially decaying functions are used to describe impulsive loads. The descriptive load parameters obtained from the modeling procedures, which are functions of several independent random variables, are envisioned as random variables. Multivariate regression analysis is used to model individual loads and group loads are modeled by shifting individual loadtime histories by random‐time phase lags and superimposing the results. The time phase lag values are exponentially distributed. Periodic and transient loads for groups of four people are generated using random simulation. The simulated results correlate with the measured data; measured and simulated frequency spectra compare well for periodic loads. We suggest simplified periodic design values using a load intensity per person considering the number of active people in the crowd.

The paper concerns the elastic out‐of‐plane buckling of monosymmetric beam‐columns/tie‐beams under uniform moment or eccentric axial loads. A new set of parameters is introduced to describe the buckling behavior of such members. These easily calculated parameters can represent any general monosymmetric I‐section and enable the designers to visualize the form of the cross section. The exact buckling solution, normally presented in a complicated transcendental form, can now be expressed explicitly and compactly using these parameters. Moreover, the buckling behavior for the entire range of monosymmetric member dimensions can be studied readily. The results show some interesting features not previously highlighted in the shape of the stability criteria.

A finite element nonlinear formulation for the stability analysis of a conical concrete shell roof for a cathedral in India is presented. The degenerated shell elements are used to idealize the shell and the buckling load is calculated based on eigenvalue approach as well as load deformation response using the nonlinear incremental structural analysis program and the conclusions are drawn.

A corrosion damage model is developed for steel girder bridges. The bridge load‐carrying capacity is determined with regard to bending, shear, and bearing. The capacity loss depends on the location and rate of corrosion. The evaluation is demonstrated on two typical steel bridges in an aggressive environment. Results indicate that the governing criteria may change over time. This change is dependent on the relative thicknesses of the girder web and flange. The web in shear and bearing is shown to be typically the critical element, particularly for shorter span bridges with no bearing stiffeners.

The process of determining the live‐load capacity of existing bridges is distinct from the design procedure, which is necessarily generalized for applicability to a large variety of structures. Such a generalization may lead to overconservative estimates of capacity, which in turn leads to such actions as closing or replacing the bridge. Thus there is a great need for a flexible evaluation strategy which rationally accounts for all the uncertainties present while at the same time allows incorporation of engineering judgement and also maintains an adequate level of safety. Stuctural reliability principles with recently developed load models and extensive statistical data for all aspects of the problem is used to attain this goal. A load and resistance factor type checking equation is developed with options for different levels of traffic severity, lateral load distribution methods, degree of deterioration of structural elements, level of inspection, and type of maintenance efforts.