Experimental investigation of reinforced-concrete Category I structures at high load levels

A US Nuclear Regulatory Commission-funded experimental program designed to obtain information on the structural behavior of reinforced-concrete buildings has been underway at the Los Alamos National Laboratory since 1980. This information will aid the NRC in evaluating the seismic capacities of existing Seismic Category I buildings. Scale models of reinforced-concrete shear walls and buildings were subjected to static and dynamic tests. Simulated seismic tests were conducted on model structures constructed to two scales (1/30 and 1/10), permitting an evaluation of the effect of scale in experimental investigations of reinforced-concrete structures. Monotonic and cyclic quasistatic tests provide information on strength, stiffness, strength and stiffness degradation, ductility, and general load-deflection behavior up to the ultimate load. The dynamic tests yielded information on natural frequencies, equivalent viscous damping values, initial stiffness and stiffness degradation, and general response behavior. These experimental investigations have indicated that sine-sweep tests are not suitable for reinforced-concrete structures and that the initial stiffness of shear wall structures is less than predicted when assuming an uncracked concrete section

Chirality and Symmetry Breaking in a discrete internal Space

In previous papers the permutation group S_4 has been suggested as an ordering scheme for elementary particles, and the appearance of this finite symmetry group was taken as indication for the existence of a discrete inner symmetry space underlying elementary particle interactions. Here it is pointed out that a more suitable choice than the tetrahedral group S_4 is the pyritohedral group A_4 x Z_2 because its vibrational spectrum exhibits exactly the mass multiplet structure of the 3 fermion generations. Furthermore it is noted that the same structure can also be obtained from a primordial symmetry breaking S_4 --> A_4. Since A_4 is a chiral group, while S_4 is achiral, an argument can be given why the chirality of the inner pyritohedral symmetry leads to parity violation of the weak interactions.Comment: 42 pages, 3 table

Experimental methods and structural models for seismic research

This paper, prepared for the ''Plenary Session'' of the ''Middle East and Mediterranean Regional Conference on Earthen and Low-Strength Masonry Buildings in Seismic Regions,'' presents the author's views on the importance of an experimentally oriented research effort in any program to improve the design and construction of structures. The importance of (1) theoretical support, (2) static tests, (3) dynamic tests, (4) use of scale models, and (5) the need for appropriate instrumentation are considered. Examples, taken from an experimental program involving reinforced concrete structures, are given to illustrate the points listed above

Nonlinear seismic response of small reinforced-concrete shear wall structures

The paper describes dynamic tests on small shear wall structures. The purpose of the tests was to obtain information on the behavior of reinforced concrete structures loaded into their nonlinear range. The small shear wall structures were subjected to classical sine-sweep vibration tests and to generated earthquake records. The results indicate that sine-sweep tests on degrading structures do not yield useful results because of fatigue effects and because steady-state motions cannot be achieved; however, the earthquake tests did yield useful information. From the earthquake tests results, responses were obtained that were plotted on computed linear and nonlinear non-dimensionalized response spectra. For loading within the linear range, the data indicate that the equivalent viscous damping for the test structures is about 12.5%. The test results also indicate that, in general, manipulation of the viscous damping coefficient cannot be used to predict nonlinear behavior. The more significant observation was that the effective stiffness of the shear wall structures, as determined from the dynamic tests, was only about 1/5 to 1/7 of the stiffness calculated using standard calculation methods

Buckling of steel cylinders containing circular cutouts reinforced according to the area-replacement method

The effect of the use of the area replacement method (ARM) for reinforcing circular penetrations in cylindrical steel shells has been studied both experimentally and analyticaly. How this type of reinforcement affects the buckling strength of a shell subjected to uniform axial compression is the specific area of investigation. In shells that are of such a quality that the penetration reduces the buckling strength, the use of the ARM will increase the bucking strength of the shell. In any case, the conservative knockdown factors suggested for buckling design by the American Society of Mechanical Engineer's (ASME) Boiler and Pressure Vessel Code should ensure an adequate margin to failure under this loading condition