Factors Contributing to the Catastrophe in Mexico City During the Earthquake of September 19, 1985

The extensive damage to high‐rise buildings in Mexico City during the September 19, 1985 earthquake is primarily due to the intensity of the ground shaking exceeding what was previously considered credible for the city by Mexican engineers. There were two major factors contributing to the catastrophe, resonance in the sediments of an ancient lake that once existed in the Valley of Mexico, and the long duration of shaking compared with other coastal earthquakes in the last 50 years. Both of these factors would be operative again if the Guerrero seismic gap ruptured in a single earthquake

Performance of Viscous Damping in Inelastic Seismic Analysis of Moment-Frame Buildings

This report investigates the performance of several viscous damping formulations in the inelastic seismic response of moment-frame buildings. The evaluation employs a detailed model of a 20-story steel building. Damping schemes included in the study are Rayleigh, condensed Rayleigh, Wilson-Penzien, two versions of tangent Rayleigh and one implementation of capped damping. Caughey damping is found not to be computationally viable. Differences among the damping schemes, as quantified by amounts of plastic hinge rotations and story drifts, become noticeable once these quantities reach the 3% level. In order of least to greatest hinge rotations and drifts that occur under lateral response to horizontal ground motion, the damping schemes rank as Rayleigh (most damping action), condensed Rayleigh, Wilson-Penzien, the standard form of tangent Rayleigh and capped damping, which are about the same, and the elastic velocity version of tangent Rayleigh (least damping action). Performance of Rayleigh damping under vertical ground motion is discussed, including the effect of soil-structure interaction. The propensity of Rayleigh damping to generate excessive damping forces and moments during inelastic seismic analysis is explained, and a parameter is introduced that can predict the potential magnitude of the effect. A review of some literature on the role of viscous damping on the inelastic seismic response of moment frames is also presented

CONSTITUTIONAL LAW - IMPAIRING THE OBLIGATION OF CONTRACTS - REFUNDING BONDS

In 1938, Mississippi authorized the issuance of state highway bonds in the aggregate of $60,000,000. Interest was payable semiannually and the bonds were to mature serially semiannually, and to the extent necessary to make these payments the revenues from gasoline taxes were pledged. The act further provided that the state covenanted that so long as any of the bonds were outstanding and unpaid, it would not authorize any other obligations or securities payable from gasoline tax revenues unless such revenues should increase in such an amount that one-third of the proceeds would be sufficient to meet the principal and interest obligations on the bonds. In 1940, the act of 1938 was amended so as to allow the state bond commission to issue bonds for the sole purpose of refunding the bonds which matured in 1941. The refunding bonds were to have the same characteristics, be payable from the same revenues and secured by the same covenants as were the original bonds. Plaintiff, who was owner of a bond issued under the act of 1938 and maturing in 1949, filed a petition to enjoin the issuance of the refunding bonds, alleging that since one-third of the gasoline tax revenues would not be sufficient to meet principal and interest payments on the bonds, the obligation of the contract embodied in the act of 1938 will be impaired. Held, the amendatory act of 1940 providing for the issuance of refunding bonds is constitutional. Bank of Morton v. State Bond Commission, (Miss. 1941) 199 So. 507

Using Software to Demonstrate Kinematics of Gear Sets

The research was done in the area of developing software which could be used to demonstrate the motion of gears. To demonstrate this motion involved learning about programming using graphics. Engineering skills were used in the programming in various ways. One way was in developing and implementing the equations and theory. The more critical engineering aspect of this project is in determining what is effective in demonstrating the kinematic principles associated with gear sets. The programs will be a helpful aid in showing students what is happening with the motion of gear sets. Not only will instructors be allowed to display drawings of gears quickly, but the important data will be displayed also. The instructor will be able to demonstrate how a slight change in a gear size will change the output in an instant. Overall this program will allow students to cover much more material pertaining to gear sets in much less time

Comments on Philippe de la Hire’s Memoir on Arch Abutment Design (1712)

Philippe de la Hire (1640-1718), a multi-disciplinary French scientist, is generally credited as being the first person to apply the principles of statics to the analysis and design of arches. Prior efforts employed geometric design rules that were based on experience. Thus, de la Hire plays an important role in the transition to scientifically based methods for civil engineering structures. Therefore, it is of historical interest to understand de la Hire’s approach and perspective

A four-lidar view of Cirrus from the FIRE IFO: 27-28 October 1986

The four ground-based lidar systems that participated in the 1986 FIRE IFO were configured in a diamond-shaped array across central and southern Wisconsin. Data were generally collected in the zenith pointing mode, except for the Doppler lidar, which regularly operated in a scanning mode with intermittent zenith observations. As a component of the cirrus case study of 27 and 28 October 1986 selected for initial analysis, data collected by the remote sensor ensemble from 1600 (on the 27th) to 2400 UTC (on the 28th) is described and compared. In general, the cirrus studied on the 27th consisted of intermittent layers of thin and subvisual cirrus clouds. Particularly at Wausau, subvisual cirrus was detected from 11.0 to 11.5 km MSL, just below the tropopause. At lower levels, occasional cirrus clouds between approx. 8.0 to 9.5 km were detected from all ground sites. Preliminary analysis of the four-lidar dataset reveals the passage of surprisingly consistent cloud features across the experiment area. A variety of types and amounts of middle and high level clouds occurred, ranging from subvisual cirrus to deep cloud bands. It is expected that the ground-based lidar measurements from this case study, as well as the airborne observations, will provide an excellent data base for comparison to satellite observations

Direct Boundary Element Method for Dynamics in a Half-Space

An application of the direct boundary element method for solving the response of a linearly elastic half-space with a canyon cut into the surface is presented. This approach uses source solutions for an undamped half-space where the resulting singular integral equations are solved directly without adding any artificial damping. Solutions for the displacements on the canyon surface reveal an artificial resonance phenomenon when solving the exterior problem in the frequency domain. The use of an additional source loading in the boundary element method is shown to eliminate these resonances and yield accurate results. A method for solving the Rayleigh waves generated on the surface of the half-space caused by the canyon is shown