The Social Psychology of Organizations.

Seismic Rehabilitation of Existing Buildings

Probability, Reliability and Statistical Methods in Engineering Design

This paper presents the results from an experimental program and an analytical assessment of the influence of addition of fibers on mechanical properties of concrete. Models derived based on the regression analysis of 60 test data for various mechanical properties of steel fiber-reinforced concrete have been presented. The various strength properties studied are cube and cylinder compres- sive strength, split tensile strength, modulus of rupture and postcracking performance, modulus of elasticity, Poisson's ratio, and strain corresponding to peak compressive stress. The variables considered are grade of concrete, namely, normal strength 35 MPa, moderately high strength 65 MPa, and high-strength concrete 85 MPa, and the volume fraction of the fiber Vf=0.0, 0.5, 1.0, and 1.5%. The strength of steel fiber-reinforced concrete predicted using the proposed models have been compared with the test data from the present study and with various other test data reported in the literature. The proposed model predicted the test data quite accurately. The study indicates that the fiber matrix interaction contributes significantly to enhancement of mechanical properties caused by the introduction of fibers, which is at variance with both existing models and formulations based on the law of mixtures. 85 MPa with various fiber dosages Vf=0, 0.5, 1.0, and 1.5%. An empirical relationship for various mechanical properties of SFRC has been proposed. The proposed model attempts to bring out the significance of fiber matrix interaction in all the strength properties. This study reports the experimental results of the strength properties of SFRC, namely, cube and cylinder compressive strength, split tensile strength, modulus of rupture, modulus of elasticity, Poisson's ratio, and strain corresponding to peak com- pressive stress. Empirical relationships were developed for vari- ous strength properties based on the regression analysis of the 60 test data. It is expected that these proposed models would be helpful in assessing the strength properties of fiber-reinforced concrete based on the matrix strength and fiber-RI.

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Mechanical Properties of Steel Fiber-Reinforced Concrete

iii ACKNOWLEDGMENTS iv TABLE OF CONTENTS vii LIST OF FIGURES xvii LIST OF TABLES xxv

Assessing seismic collapse safety of modern reinforced concrete moment frame buildings

This paper provides an approach to conduct a probabilistic assessment of structural damage due to seismic events with an application to typical building structures in mid-America. The developed methodology includes modified damage state classifications based on the Applied Technology Council (ATC)-13 and ATC-38 damage states and the ATC-38 database of building damage. Damage factors are assigned to each damage state to quantify structural damage as a percentage of structural replacement cost. To account for the inherent uncertainties, these factors are expressed as random variables with a Beta distribution. A set of fragility curves, quantifying the structural vulnerability of a building, is mapped onto the developed methodology to determine the expected structural damage. The total structural damage factor for a given seismic intensity is then calculated using a probabilistic approach. Prediction and confidence bands are also constructed to account for the prevailing uncertainties. The expected seismic s...

Probabilistic Assessment of Structural Damage due to Earthquakes for Buildings in Mid-America

A model for predicting punching shear failures at interior slab-column connections was developed based on experimental results obtained at various universities. This model has been incorporated into a new RC slab element for the nonlinear analysis program, DRAIN-2DM, along with the desired unloading behavior when a punch occurs. A four-story RC frame office building that experienced punching shear failures during the Northridge earthquake was evaluated using this new model and the occurrence of punching shear failures was successfully postcalculated for the ground motion recorded nearest the structure. The study building was evaluated for three ground motions scaled to the same peak ground acceleration. The building response varied for each record, but in general, it was found that the inclusion of punching shear failures can modify the overall building response in terms of drift, fundamental period, inelastic activity, and base shear distribution. In the case of the study building, the presence of the st...

Nonlinear Punching Shear Failure Model for Interior Slab-Column Connections

High-strength concrete (HSC) is widely used in prestressed concrete bridges (PCBs). Current design guidelines for PCB structures such as the AASHTO LRFD specifications, however, were developed based on mechanical properties of normal-strength concrete (NSC). As a first step toward evaluating applicability of current AASHTO design provisions for HSC prestressed bridge members, statistical parameters for the mechanical properties of plant-produced HSC were determined. In addition, prediction equations relating mechanical properties with the compressive strength were evaluated. HSC samples were collected in the field from precasters in Texas and tested in the lab at different ages for compressive strength, modulus of rupture, splitting tensile strength, and modulus of elasticity. Statistical analyses were conducted to determine the probability distribution, bias factors (actual mean-to-specified design ratios), and coefficients of variation for each mechanical property. It was found that for each mechanical property, the mean values are not significantly different among the considered factors (precaster, age, specified strength class) or combination of these factors, regardless of specified design compressive strength. Overall, 28-day bias factors (mean-to-nominal ratios) decrease with increases in specified design compressive strength due to relative uniformity of mixture proportions provided for the specified strength range. Still, the 28-day bias factors for compressive strength are higher than those used to calibrate AASHTO LRFD specifications. With few exceptions, the coefficients of variation were uniform for each mechanical property. In addition, the coefficients of variation for the compressive strength and splitting tensile strength of HSC in this study are lower than those for NSC used in the development of the AASHTO LRFD specifications.

Mechanical Properties of High-Strength Concrete for Prestressed Members

Seismic performance of a reinforced concrete frame building in China

This paper documents an experimental testing program on the lateral in-plane behavior of pre-1950s existing and rehabilitated wood floor and roof diaphragms in unreinforced masonry buildings found in the Central and Eastern regions of the United States. Three diaphragm specimens were constructed with elements and connection details typical of pre-1950s construction. The specimens were tested, retrofitted, and retested again using different rehabilitation methods, including enhanced shear connectors and perimeter strapping, a steel truss attached to the bottom of the joists and connected to the vertical lateral force resisting system, and unblocked and blocked plywood overlays connected to the sheathing and joists. Specimens were tested under quasi-static reversed cyclic loading to evaluate their in-plane lateral deformation performance at selected locations of the diaphragm. The measured in-plane lateral response was used to develop backbone curves defining the relationship between the applied lateral for...

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Mary Beth D. Hueste

Papers

Probabilistic Assessment of Structural Damage due to Earthquakes for Buildings in Mid-America

Nonlinear Punching Shear Failure Model for Interior Slab-Column Connections

Mechanical Properties of High-Strength Concrete for Prestressed Members

Seismic performance of a reinforced concrete frame building in China

Seismic Behavior of Wood Diaphragms in Pre-1950s Unreinforced Masonry Buildings