Journal of Structural Engineering

Four large glulam beams with notches on the tension side were tested for strength and stiffness. Using either bending net section beam theory or shear formula to calculate crack propagation critical load is very unconservative. A linear elastic fracture mechanics approach, taking into account the high tension stresses perpendicular to grain and shear stresses at the notch reentrant corner, conservatively predicts the critical load. The data corroborate the substantial analytic effect of size predicted by fracture mechanics for notched beams. Results quantify the observed behavior of bending of beams with notches on the tension side. The strength reduction is so severe for large beams that substituting a beam having the net depth of the notched beam is preferable. Removing material would remove the stress concentrator and would increase the strength up to net section theory prediction at the notch location. Using an effective notch length (actual notch length + notch depth added to each end of the notch) and variable moment of inertia, beam theory accurately predicts the notch beam deflection under load.

In spite of poor record of safety of masonry buildings during past earthquakes, it continues to be the most common method of building construction. A building system, is considered here to investigate the ground motion isolation feasibility, in which a clear smoothened surface is created at plinth level and is free to slide except for the frictional resistance. The sliding arrangement introduces an isolation effect and reduces the energy input by dissipating part of the seismic energy through friction. The seismic response of the masonry buildings with sliding substructure subjected to Koyna and El Centro shocks is computed through a two mass‐spring‐dashpot mathematical model assuming the frictional resistance as rigid plastic. The parameters involved in the analysis are time period, mass ratio, and coefficient of friction. The spectral quantities of the sliding system are plotted against the natural period for various mass ratio and coefficient of friction. These spectra show the reduction in response of the buildings with sliding arrangement as compared with the conventional buildings.

Wind‐induced internal pressures in buildings can be analytically evaluated by using external pressure coefficients appropriate for each surface of the building envelope. The evaluation considers the overall building porosity and the specific (intentional or unintentional) wall (or roof) openings. Analytically‐evaluated internal pressure coefficients show reasonable agreement with experimentally‐determined values in either full‐scale or boundary layer wind tunnel experiments. Comparison of internal pressure coefficients with those suggested in the North‐American Standards indicate the need to consider further the influence of overall porosity and relative size of openings for better estimation of internal pressures. ANSI Standard in particular seems to underestimate wind‐induced internal pressures for specific leakage configurations.

A method based on the combination of the imposed deformation approach and the stable configuration approach of structural system reliability analysis is developed for evaluating the reliability of structures with elements that behave in a nonlinear fashion, as well as fracture, or fail in a brittle manner, at some deformation. The basis of the stable configuration approach is examining ways in which a structure may carry an applied load and the basis of the imposed deformation approach is examining the structure under specified deformations. The method is found to generally give conservative estimates of the probability of failure. The proposed method is applied to a practical problem that arises when considering progressive collapse in precast large panel concrete structures. In particular, the probability a precast concrete slab system will not remain suspended if a supporting wall fails is determined to be 0.36.

The formulation of a fiber model is presented for the second‐order analysis of slender concrete compression members of arbitrary cross section and longitudinal configuration subjected to static biaxial loading. The analytical model uses a tangent stiffness formulation. The stiffness method is used to calculate incremental displacements from applied loads, and incremental forces are then computed from the displacements. The model uses a linear formulation, which has been modified to include various nonlinear effects. The nonlinearities included in this fiber model are P‐delta effects, geometric nonlinearity, material nonlinearity, and sustained load effects. The use of this fiber model for analysis of concrete bridge piers meets design needs not satisfied by current design codes and specifications. An example using the fiber model for analysis of a hollow and tapered slender concrete bridge pier demonstrates its power and versatility.

An experimental program to study the effect of impact on reinforced concrete slabs was carried out. The experimental program attempted to simulate the striking of flying objects at the center of a reinforced concrete slab to study the response (dynamic deflection) of that slab due to this load. The program consisted of considering 5 cm‐thick reinforced concrete slabs as simply supported on a rigid horizontal steel frame. A rigid missile simulated by a 12‐cm diameter steel ball was allowed to fall freely from heights up to 120‐cm on the center of this slab. The measured slab dynamic deflections was then monitored versus time using reliable instrumentation. Aspects that affect the slab's response to impact were investigated. The aspects investigated in this study include the relationship between slab reinforcement and dynamic deflection, and the relationship between the velocity of the rigid missile at impact and the obtained deflection. Results of this experimental program are compared with the results obtained by using three different analytical approaches published previously. In general, the trend of the dynamic deflections measured at the center of the reinforced concrete slabs agree best with one of the analytical methods.

Test data are presented on the shear strength of a series of longitudinally reinforced fibrous concrete beams in which the shear span‐to‐effective depth ratio, volume fraction of fibers, percentage of reinforcement, and strength of the concrete were varied. Test results indicate that the fibers have significant influence on the mode of failure and ultimate shear strength of a longitudinally reinforced concrete beam. Conventional reinforced concrete analyses with some modification, as suggested in this paper, to account for the effect of fibers give good predictions of the ultimate strength and the mode of failure for rectangular beams with no shear reinforcement.

Current code provisions for drift snow loads on multilevel roofs are examined in light of recent research results from a statistical study of approximately 350 drift load case histories. New provisions are proposed in which the design drift load is a function of the length of the upper‐level roof and the 50‐yr mean recurrence interval ground snow load. It is felt that these new proposed provisions result in a design drift load with a mean recurrence interval of about 50 yrs.

A study of a hanger‐type, end‐grain, timber‐beam connection, in which a steel plate was fastened to a laminated timber beam with steel dowels, shows that the connection can be used successfully in timber construction. Beam on elastic foundation theory accurately predicts the lateral load‐deformation response of single‐ and multidowel connections up to loads corresponding to 1.11 to 1.34 kN/dowel, if full fixity of the dowel head in the connector plate is ensured. To evaluate the effect of withdrawal forces on the shear strength of the connection, shear/withdrawal interaction curves were developed for the dowel. The load‐deformation response, strength, and mode of failure for the connection under combined lateral and withdrawal loads were determined for Douglas fir, Southern pine, cedar, and white pine. The performance of Southern pine connections subjected to intermittent short‐term and constant long‐term loads is shown. Recommendations for design loads are presented.

A new design criterion for wood members under combined axial and bending loads is proposed. The new equation covers biaxial bending, axial load, and water ponding. It employs Ylinen's column formula for beam or column buckling, and replaces the linear interaction equation with more accurate equations based on recent test data and results of elastic stability analysis. Despite its simplicity, the proposed criterion is more general, more rational and more accurate than the existing design criterion.

A finite element bridge model of cross section reflecting interstate quality was analyzed for varying curvatures, lengths, and bracing intervals. Results from this parametric study were analyzed by linear and nonlinear regression techniques to predict the ratio of: (1) Maximum bending stress; (2) maximum warping stress; and (3) maximum deck deflection for a curved bridge to corresponding quantities of a straight bridge of equal length. In addition, an empirical equation was developed to provide a guideline for setting the maximum bracing spacing.

Design values for bolted timber joints are empirically based on research conducted over 50 years ago. The analytical and experimental results of this study confirm that the previous recommendations are still valid. The analytical method used in this study, the European yield theory, explains much of the observed behavior of bolted timber joints and can be used for material properties not included in the original research. It also incorporates the effect of bolt yield stress, which is not considered in current design.

This paper summarizes the research needs identified at the 1983 workshop on structural wood. Eight sessions dealing with structural material (lumber), connections, subassemblies, heavy timber structures and bridges, structural material (panels), reliability‐based design, trusses and manufactured structural components, and light‐frame buildings were held and research needs identified. Participants included researchers and engineers from various industrial, governmental and educational institutions.

Besides the pendulum action developed by the suspended deck, the restoring force exerted by a cable during lateral displacements is expressed by the horizontal component of the cable tension, times the curvature of the cable in the horizontal plane. Some authors consider an additional term linked to a pendulum effect of the cable itself, caused by the uplift movement which accompanies the lateral displacements. In the present note, the mathematical model is reviewed to show that, in the usual assumption of small amplitude vibrations, the presence of this second term is due to a sign error in the expression of the strain energy of the cable. Some evaluation of the first vibration modes period is reported.