Journal of Structural Engineering

Cylindrical cold‐formed steel structures are widely used for grain storage on the farm, as well as for stock facilities, storages, and utility structures. The information related to their analysis and design is scattered and incomplete; therefore a task committee was established by the ASCE Committee on Cold‐Formed Steel Members, with the following objectives: (3) To define the problems encounted in the analysis and design of these types of structures; and (2) to gather and develop information that could lead to rational methods of design. The state of the art for the upright cylindrical grain bins made of cold‐formed steel is discussed. Barrel shells will be discussed in a companion paper, Part II. Both papers critically examine the existing methods of analysis and, wherever possible, additional information and charts are provided to simplify the design process.

An experimental study is made of confinement effectiveness of crossties in reinforced concrete columns subjected to monotonically increasing axial compression. Ten columns were constructed, of which eight were reinforced. The main variable was the type of transverse reinforcement. Comparison is made between strength and ductility obtained by the different types of transverse steel, and analytical moment‐curvature studies are used to estimate the influence of different confined concrete behaviors on flexural behavior of columns and structural walls. It is observed that crossties having 180° hooks are as effective in confining concrete as intermediate hoops. Crossties having 135° and 90° hooks are nearly as effective. It is concluded that both types of crossties are acceptable details for confinement of concrete where large inelastic strains will be applied monotonically.

A procedure is described for automated sizing of the members and selection of pretension values for guyed antenna towers. The towers consist of a triangular cross section, tubular member mast supported by a number of sets of pretensioned guys. The sizing procedure employs a nonlinear finite element analysis coupled to a nonlinear mathematical programming based optimizer. Numerical studies were performed on a typical VLF antenna configuration to obtain minimum weight tower designs. Various loading conditions, tower heights, and tower materials were considered.

Steel bracing members are widely used in steel structures to reduce lateral displacements and dissipate energy during strong ground motions. This concept is extended to concrete frames Inelastic seismic response of reinforced concrete frames with K and X steel bracing patterns is presented. A two bay six story frame designed by limit state design procedure was subjected to 1.25 times the North‐South component of the 1940 El Centro earthquake and the artificially generated B1 earthquake. Takeda's bilinear hysteresis model was assumed for girders, an elastoplastic model was assumed for columns with axial force effects included, and a multilinear buckling model was assumed for steel bracing members. It is concluded that the inelastic response of both the K and X braced frames are satisfactory under the modified El Centro earthquake The response of X braced frame is much better compared to that of the K braced frame under the modified B1 earthquake. It is also noticed that there is a considerable increase in the column axial forces due to the presence of bracing members, which is typical of braced frames.

Lateral‐load response of a flat‐plate frame under simulated earthquake base motions is examined. The test structure is a three‐tenths scale model of a two‐story, three‐bay flat plate frame, which was designed and detailed according to current procedures for beamless slabs in regions of moderate seismic risk. Overall resistance to low, moderate, and high intensity base motions is examined, and design‐oriented methods to evaluate lateral‐load stiffness and strength are examined. It is concluded that the design resulted in a flexible but reasonably tough structural system. Relatively simple procedures to evaluate stiffness and strength are presented and found to be acceptably accurate for the test structure.

An investigation is made of the possible application of both the active tendon and active mass damper control systems to buildings excited by strong earthquakes. The effectiveness of both active control systems as measured by the reduction of coupled lateral‐torsional motions of buildings is studied. The earthquake ground acceleration is modeled as a uniformly modulated non‐stationary random process. The problem is formulated using the transfer matrices approach and a closed‐loop control law. The random vibration analysis is carried out to determine the statistics of the building response and the required active control forces. The method of Monte Carlo simulation is also employed to demonstrate the building response behavior with or without an active control system. A numerical example of an eight‐story building under strong earthquake excitations is given to illustrate the significant reduction of the building response by use of an actives tendon or an active mass damper control system.

Attention is given to the interaction between local and lateral buckling of I‐sections and their influence on plastic flexural ductility in regions of moment gradient. It is shown by means of simple theoretical formulations and the results of a series of tests to failure that rotation capacity in the plastic range is influenced significantly not only by conventional codified parameters, but also by the ratio of span to flange thickness and coincident axial force. In addition, the interaction between local and lateral buckling in the plastic region is demonstrated, and a model is formulated for quantifying this strain‐weakening effect. The results are relevant to the plastic design of structures as well as more general research into methods of improving flexural ductility of I‐sections.

Fluctuating wind forces on tall buildings can cause excessive building motion that may be disturbing to the occupants. A method to relate dynamic alongwind, acrosswind, and torsional forces acting on square isolated buildings to building accelerations is developed using random vibration theory. Wind tunnel test data are analyzed to determine the spectra of force components and correlations among the different components of force. The effects on building vibration of statistical correlations among components of force and mechanical coupling of components of motion introduced by eccentricities of the centers of mass and rigidity from the building centroid are examined. Comparison are made with more common building analyses, where the forces are assumed to be statistically uncorrelated and the components of motion are assumed to be uncoupled.

The behavior of plates exhibiting different longitudinal and transverse stress‐strain relations beyond the elastic limit is investigated. The equivalent load concept is used to assess the influence of plastic orthotropy on the behavior of plates undergoing large deflections. For plates considered, the lateral deflection is increased only slightly by the orthotropic behavior; the maximum extreme fiber stresses are, however, influenced more significantly as the aspect ratio of the plate approaches unity. The effect of orthotropy on stresses is reduced with increasing the aspect ratio of the plate.

Standard methods of testing the racking capacity of light‐frame walls are inefficient and may give erroneous estimates of shear wall performance. This study is concerned with improving the data base for racking resistance of light frame walls with plywood and gypsum sheathings. The shear resistance of small walls sheathed with gypsum was compared to that of full‐size walls. Results of both tests indicated that racking strength was linearly proportional to wall length. Contributions of sheathing layers and panel sections appear be additive, and length of wall sections containing door and window openings may be neglected in determining racking resistance of conventional walls. One notable difference in the performance of these racking tests involved the effect of panel length on racking stiffness. Stiffness of small walls increased linearly with length while the stiffness of full‐size walls increased nonlinearly. Knowledge that gypsum wallboard can contribute to shear wall performaoee and that it is additive to the resistance of plywood sheathing should be helpful to building designers and code officials.

Three alternative experimental methods for subjecting structural models of steel offshore towers to severe inelastic lateral loadings simulating siesmic effects are described. These pertain to either pseudo‐static or pseudodynamic methods of loading, or to experiments performed using a shaking table. These methods are evaluated with respect to their advantages and disadvantages. Test results are highlighted to provide insight into the inelastic cyclic behavior of this type of structure. Since the seismic problem is by its very nature nondeterministic, seismic experiments primarily provide a data base for verifying the capabilities of available computer programs. Methods for predicting the inelastic seismic response of braced tubular steel platforms are briefly reviewed. Comparisons of experimental with analytical results are then presented to indicate the confidence that can be placed in such analytical predictions.

The number of degrees of freedom for the stability analysis of plane frames may be considerably reduced by introducing axial constraints. Determination of the rank and basis of the constraint matrix by Gauss-Jordan elimination with pivoting leads to automatic selection of the best set of dependent and independent joint translations. Then a transformation of the buckling equations produces a reduced set of equations, that may be solved for the buckling loads of frames. This technique can be applied in conjunction with the elimination of joint rotations, thereby accomplishing a double reduction without significant loss of accuracy. The procedure described has been programmed on a digital computer.