Richard M. Bennett

Three-parameter vs. two-parameter Weibull distribution for pultruded composite material properties

The three-parameter and two-parameter Weibull distributions are compared using 26 mechanical property data sets of fiber-reinforced polymeric (FRP) composite materials manufactured by the pultrusion process. Both strength and stiffness properties were examined. The probability distributions were compared on the basis of goodness of fit, nominal design values, and allowable load to achieve uniform reliability. It is recommended that the two-parameter Weibull distribution be used to characterize FRP composite material properties. The primary basis for this recommendation is small differences in nominal design values and small differences in allowable loads between the two-parameter and three-parameter Weibull distributions. Other supporting reasons for the recommendation are similar observed significance levels in distribution fitting, computational efficiency, and the fact that the location parameter of the three-parameter Weibull distribution is near the first order statistic.

Formulations for probability of progressive collapse

Abstract Practical and tractable formulations for determining the probability of progressive collapse in structures are developed. Both the case where abnormal loads are specified and the case where initiating damage levels are specified are considered. Methods for including event control measures in the formulations are also obtained. The formulations are applied to two examples: the vertical progressive collapse of a concrete panel building and the progressive collapse of a shorting system.

Geoacoustic properties of the seabed sediment critical to acoustic reverberation at 50 to 500 Hz: A preliminary data set

As much as 80% of acoustic reverberation is produced through bottom interactions. Deep‐sea sediment have high porosity (or low velocities), therefore, a waveguide is often formed from strong bottom interactions. In addition to the bottom roughness, the random variation in the geoacoustic properties (the compressional wave velocity in particular) of the sediment is responsible for generation of the incoherent propagation/acoustic reverberation. Our existing data [e.g., Bennett et al., Handbook of Geophysical Expro. (1983)] indicate that very strong spatial variations (vertical and horizontal) usually exist in the deep‐sea sediments. A preliminary analysis of these geological data by the Biot‐Yamamoto theory [Yamamoto and Turgut, J. Acoust. Soc. Am. 83, 1744–1751 (1988)] reveals that strong velocity variations, as much as 20% in velocity magnitude, usually exist in the deep‐sea muds at horizontal and vertical scales of 0.3 to 30 m, which is very critical to acoustic reverberation at 50 to 500 Hz. [Work supp...

LABORATORY AND IN SITU MEASUREMENTS OF SELECTED GEOACOUSTIC PROPERTIES OF CARBONATE SEDIMENTS

Selected geoacoustic properties of sediments such as shear modulus (G), frame loss coefficient (δ), porosity (β), and the permeability (ks) are needed as input to predictive geoacoustic models. In situ and laboratory measurements of these properties for carbonate sediments of the Great Bahama Bank are presented here. Shear modulus and frame loss coefficient are measured at very low shear strain amplitude by using a combined torsional, resonant column, and triaxial (CTRCT) apparatus in the laboratory. The in situ shear modulus is measured by a newly developed bottom shear modulus profiler (BSMP). The in situ and laboratory measurements of shear modulus, porosity, and permeability are compared. These comparisons indicate that the laboratory and in situ measurements of shear modulus and porosity are in good agreement; however, in our comparisons, the permeability measurements in the laboratory were always somewhat lower than the in situ values. Particle size analysis indicates that these sediments are mixtur...

Reliability analysis of frame structures with brittle components

Abstract A review is provided of the recent developments in the reliability analysis of ductile (elastic-plastic) systems and of the stable configuration approach of structural system reliability analysis. These are combined to obtain a methodology for evaluating the reliability of frames that have primarily ductile components but also a few brittle components. The methodology is applied to two frame structures.

Shear Behavior of Corrugated Tie Connections in Anchored Brick Veneer–Wood Frame Wall Systems

An experimental study was carried out to investigate the shear behavior of corrugated metal ties anchoring brick veneer walls to light wood frame backing. Connection subassemblies were tested under monotonic and cyclic shear, simulating in-plane loading of veneer wall systems, and statistical analyses were conducted to identify and quantify the parameters influencing their behavior. Force-displacement curves obtained under monotonic loading can be considered an upper bound for the hysteresis loop envelopes. Fastener slippage during cyclic loading enabled by the localized damage of the surrounding wood fibers diminished the energy dissipation capacity of the connection and caused pronounced pinching in the hystereses. When corrugated ties with minimum thickness permitted by the Masonry Standards Joint Committee (MSJC) Code were considered under in-plane loading, tie design and bend eccentricity were found to be the most important factors, while tie location in the bed joint, fastener type, and fastener qua...

Shake table testing of structural clay tile infilled frames

Two steel frames with structural clay tile infills were tested under simulated seismic loads in both the out-of-plane and in-plane direction. Out-of-plane testing showed that infill panels separate from their bounding frame, and respond at their own natural frequency during a seismic excitation. Due to arching, the panels remain stable. In-plane seismic testing showed similar behavior patterns to previous static testing. The natural frequency was adequately predicted using a piecewise linear equivalent strut analytical method. The structure was then subjected to over one thousand cycles of loading using a sine sweep before failure.

The engage program: results from renovating the first year experience at the University of Tennessee

An innovative new freshman engineering initiative called engage has been fully implemented at the University of Tennessee. This is a comprehensive approach to meeting the educational and developmental needs of our freshmen. Extensive data on student performance was collected during the two-year phase in of this new program. Results presented include retention rates (engineering college and university), progression through the program, performance on common final exams and performance in sophomore courses. Comparisons are also made between the engage program and nationally administered surveys, i.e. Pittsburgh survey on engineering student attitudes. In all these areas students in the new program did as well or better than those in the traditional curriculum.

Measurement of Earth Pressures on Concrete Box Culverts under Highway Embankments

To obtain a better understanding of the stresses acting on cast-in-place concrete box culverts, and to investigate the conditions which resulted in a culvert failure under about 12 meters of backfill, two sections of a new culvert were instrumented. The measured earth pressure distribution was found to depend upon the height of the embankment over the culvert. For low embankment heights (less than one-half the culvert width), the average measured vertical earth pressures, weighted by tributary length, were about 30% greater than the recommended AASHTO pressures. The measured lateral pressures were slightly greater than the AASHTO pressures. As the embankment height increased, the measured weighted average vertical stress exceeded the AASHTO pressures by about 20%. Lateral pressures which exceeded the vertical pressures were recorded at the bottom of the culvert walls, and small lateral pressures were recorded on the upper locations of the wall. The high lateral pressures at the base of the wall are consistent with the results from finite element analyses with high density (modulus) backfill material placed around the culvert.

Masonry infill performance during the Northridge earthquake

The response of masonry infills during the 1994 Northridge, California earthquake is described in terms of three categories: (1) lowrise and midrise structures experiencing large near field seismic excitations, (2) lowrise and midrise structures experiencing moderate far field excitation, and (3) highrise structures experiencing moderate far field excitation. In general, the infills provided a positive beneficial effect on the performance of the buildings, even those experiencing large peak accelerations near the epicenter. Varying types of masonry infills, structural frames, design conditions, and construction deficiencies were observed and their performance during the earthquake indicated. A summary of observations of the performance of infills in other recent earthquakes is given. Comparison with the Northridge earthquake is made and expected response of infill structures in lower seismic regions of the central and eastern United States is discussed.