Journal of Structural Engineering

The results of a series of tests on a full‐scale reinforced concrete structure subjected to simulated earthquake loading are used to study the behavior of beam hinging regions. The measured beam rotations from an open frame and a shear wall frame are compared to the results from an analytical study to estimate the rotational ductility demand of beams at different stages of building displacement. The results indicate that there is a pronounced difference between the ductility demand of beams in an open frame and those connected to a shear wall. A relationship between the beam hinge rotation of the actual structure and displacements of individual beam elements is presented to establish a guideline for choosing displacement histories for experimental programs of beam elements. The analysis shows that there is not a unique relationship between the displacement of individual beam specimens and the lateral displacement of the building, nor is this relationship linear. The specimens that simulate the behavior of beams at different locations in a building should undergo different displacements histories.

An attempt is made to study the fracture behavior of ferrocement beams using J‐integral and critical crack opening displacement approaches. Ferrocement beams with three different relative notch depths and different percentages of mesh reinforcement were tested in four‐point bending (third‐point loading). The experimental results were used to evaluate the apparent J‐integral and ${\mathrm{COD}}_c$ values. Results show that the apparent J‐integral does not seem to follow any particular trend in variation with notch depth, but is sensitive to the increase of mesh reinforcement. Hence, the apparent J‐integral appears to be a useful fracture criterion for ferrocement. The computed values of CODt are found to be dependent on the depth of notch and, thus, cannot possibly be considered as a suitable fracture criterion for ferrocement.

Design aids and design procedures are given for welded connections in hollow structural section, single‐chord, planar Warren and Pratt trusses subject to predominantly static loading. These graphical design aids, relying on six design charts and covering gapped and overlapped K‐ and N‐shaped joints, are based upon complex joint Load and Resistance Factor Design recommendations recently proposed by the International Institute of Welding and the Comité International pour le Développement et l'Etude de la Construction Tubulaire. The design method recommended considerably simplifies joint strength calculations and aids member selection. The scope is such that square or circular web members welded to square or rectangular hollow section chord members can be accommodated. Contemporary design methods for axially loaded X, Y and T connections, which could also arise in Warren and Pratt trusses, are briefly reviewed.

A new and practical technique of lateral bracing for single‐ and multistory steel frame construction is presented and discussed. Disposable Knee Bracing (DKB) technique, as it is called in this paper, is made up of two structural elements, the knee element and the diagonal brace element. The knee element is a fuse‐like element that dissipates energy by the formation of plastic flexural hinges at its ends and midspan when the building is subjected to severe lateral loads. The diagonal brace element, on the other hand, provides the required level of lateral stiffness and remains in the elastic range at all time. The knee element is a disposable beam element that can be replaced once its energy dissipation capacity is utilized. Standard limit analysis of low‐ and high‐rise steel frames are presented to demonstrate the advantages of the DKB against traditional bracing and eccentric bracing.

Hysteretic responses of single mass reinforced concrete columns subjected to seismic biaxial base motions with constant and varying axial load are studied using the triaxial spring model. Comparisons are made with the trilinear degrading and the biaxial bilinear models based on plasticity theory. Varying axial load on columns due to overturning effects of 10‐story space frames subjected to biaxial base motions are investigated. The results indicate the axial force and biaxial bending moment interaction on R/C column is important.

This study is intended to provide experimental verification of the validity of analytical methods for the prediction of the response to loads of flexibly connected steel frames. To this end, test data are provided for the behavior of one particular connection type. These data are formulated for incorporation in a displacement matrix analysis, which is then used to predict the response to load of flexibly connected, statically indeterminate steel frames. This predicted behavior is then compared to measured moments, joint rotations, and deflections of loaded frames. It is concluded on the basis of these limited test data that the method is well able to predict frame response to load cycles, that linearly elastic analysis is sufficient to predict frame behavior under service conditions, and that these frames tend to shake down to their elastic state under high load cycles.

A formula for limiting truck and combination vehicle weights is proposed. The proposed formula gives the maximum allowable gross vehicle weight as a function of extreme axle spacing, and is intended to replace the existing formula which depends on the number of axles in the string as well as the extreme axle spacing. The advantages of the proposed formula over the existing formula are several. The existing formula does not prevent certain critical vehicles from operating on H15 bridges except by means of a footnote addendum. The proposed formula does protect H15 bridges against such vehicles. The existing formula does not provide adequately for economic operation of proposed long combinations of multiple trailers. An existing 80,000 lb gross vehicle weight limit presently prevents extension of the existing formula to the proposed longer vehicles. Should the existing 80,000 lb limit be increased or removed, the existing formula would not adequately protect HS20 bridges. The proposed formula will protect the bridges in the absence of such a limit.

A series of analytical studies on the hysteretic behavior of R/C interior beam‐column joints are presented. Parameters varied include the ratio of top to bottom reinforcement, the yield strength of reinforcing bars and the bond strength along the bars anchored in the joint. The studies are based on a finite element model, which accounts for the cyclic bond deterioration along anchored bars as well as the hysteretic behavior of cracked R/C sections at beamcolumn interfaces, thus allowing consideration of the interaction between the two end sections of the joint.

A simple procedure is presented for computing the composite stiffness of a wood bending member with sheathing attached nonrigidly to one or both edges. To account for interlayer slip, it is only necessary to modify the axial stiffnesses of the flanges and then compute the stiffness of the resulting T‐beam or I‐beam by the “transformed area” procedure. Test data agreed very closely with theoretical predictions. The method also provides reasonable estimates of interlayer slip. The procedure can be carried out on a hand‐held calculator and is therefore in a form which can be accepted by code writers and easily implemented by designers.

A simple and computationally efficient model of the hysteretic response of reinforcing bar anchorages under severe cyclic excitations is presented. The model is based on a piecewise linear approximation of the bond stress distribution function along the bar anchorage length. Only three intermediate points located between the ends of the bar suffice to yield results which match the finite element solution of the problem. The bond stress value at these intermediate points is established by iteratively satisfying the equilibrium and compatibility equations of the bond problem.

TO determine effects of centrally located openings on earthquakeresistant structural walls, two 1/3‐scale structural wall specimens were tested. Specimen CI‐1 was an isolated wall with no openings, designed according to UBC and ACI recommendations. Specimen PW‐1 was nominally identical to specimen CI‐1 except for openings at every floor level. Reinforcement details around openings were selected to represent current design practice. Specimen PW‐1 had an opening‐to‐wall area ratio of 8.33%. Lintels in specimen PW‐1 had a shear span‐to‐depth ratio of 0.35. Similar load histories representing severe earthquakes were applied to both specimens, whose behavior was then compared. Effects of openings on strength and deformation were determined.

The increased emphasis on limit state design philosophy calls for a corresponding emphasis on the behavior of structural systems up to their ultimate load‐carrying capacities. Fifteen full‐size wood‐joist floors—each having 10 joists—were tested to their ultimate capacities under uniformly distributed loads. Behavior was noted at the design load and at the limit states of first joist rupture and ultimate strength. The general stiffening effect of the sheathing and the two‐way action in each system were compared with the assumed bare‐joist behavior at the design load level. Loads at first joist rupture ranged form 101–228 psf. The ultimate limit state was defined as the highest uniform load that could be applied over the entire floor surface, and magnitudes ranged from 135–383 psf. The mode of failure at the ultimate limit state appeared to depend on the rate of loading.

A vibration measurement was carried out on an existing prestressed concrete bridge during its failure test. The vertical and horizontal vibrations were measured based on the ambient vibration method. The change of vibrational characteristics due to deterioration of the bridge during the failure test was obtained. Moreover, a measured mechanism on the change of vibrational characteristics is discussed compared with a numerical analysis.

Available methods of strength analysis of glass plates provide conflicting estimates of the reliability of glass plates under known loading. The most realistic theory is unfortunately also the most complex and yields a paradoxical result: Some glass plates can support higher uniform pressure when they are made longer, wider, and thinner. An alternative theory, using concepts that are simple and familiar to the structural engineer, is therefore developed. The theory neglects Poisson's ratio and employs, for flexural stresses at the center, large displacement harmonic decomposition truncated after the first term. Membrane stresses at the center are calculated from second‐order theory and deep beam analysis. The loading component carried by this stress system is subtracted from the applied uniform loading to define a loading around the edges. The maximum stresses from this loading are calculated by elementary beam theory. This theory is calibrated to agree with recent tests. It provides a simple explanation for the paradoxical result of complex theory.

Four additional sets of aerodynamic data are presented for 4 bluff shapes. The data include aerodynamic lift, drag, and pitching moment in a range of the angle-of-attack from zero to 180 deg. The Reynolds number was 105,000. The shapes are each symmetrical about one axis. The basic dimension is a circular cylinder of five inches diameter. The data are considered representative of ice forms on cylindrical shapes, cables, and electric power transmission conductors. Structural designers may use this data for analysis and design.

A method for computing response spectra for bilinear hysteretic systems subjected to earthquake accelerograms is summarized. The technique provides the exact solution to the equation of motion for ground acceleration which varies linearly between successive digitized points. The complete solutions for the elastic and plastic components of the response are developed, and include underdamped, critically damped, and overdamped cases. A comparison of this analytical technique with five widely known alternative procedures is presented.

Reduction of the ultimate strength of pinned connections as a result of large clearance between the pin and the hole is discussed. Test data are used to develop curves quantifying this reduction for the two primary modes of failure for pin plates. General suggestions are made for the design of pinned connections in which the pin-to-hole clearance may vary.