During the Michoacan earthquake of September 19, 1985, the water supply and distribution systems of Metropolitan Mexico City were severely damaged. This paper investigates the type of damage, taking into consideration the characteristics of the earthquake and the peculiar soil and topographic conditions of the valley where the city is situated. It describes the water systems in the metropolitan area, the main features of the subsoil conditions and the engineering aspects of the earthquake, highlighting their relationship to lifeline earthquake engineering. The investigation concentrates on the damage statistics for the buried segmented pipelines in the water systems. It observes and explains the relatively low damage to lifelines in the epicentral region by analyzing and comparing ground motion characteristics there and in Mexico City. Finally, based on the analysis of this information, some recommendations are given to reduce the seismic vulnerability of the water systems in the metropolitan area.
An innovative displacement-based seismic design procedure for regular planar framed structures considering sidesway collapse prevention is presented. The method proposed, based on the characterization of a multiple degree of freedom system by means of a single degree of freedom system, allows the design of structures with a P-Delta induced negative stiffness to satisfy an interstorey drift threshold and/or prevent dynamic instability. The design procedure relies on the use of elastic analysis of simplified models and collapse or constant ductility spectra, hence, non-linear dynamic analyses are not required. To illustrate the potential of the method proposed, example applications and validation of the results obtained via incremental dynamic analysis are shown.
The influence of crumb-rubber on the mechanical properties of Portland cement concrete (PCC) is studied by experimental tests and numerical simulations. The main hypothesis of the study is that replacing part of the stone aggregate with crumb-rubber in the mix modifies the energy dissipation during the cracking process and affects the concrete behaviour under monotonically increasing loads. The experimental research program characterizes the mechanical properties of PCC for three different types of concrete with a variable content of crumb-rubber. The experimental results showed that fracture energy and other properties are directly related to the rubber fineness used in the mixture. The material properties derived for these laboratory tests are used to study, by numerical models, its response through its damage evolution. The numerical model used to simulate the damage evolution of the concrete is the Embedded Discontinuity Method (EDM). One characteristic of the EDM is that it does not need to modify the mesh topology to propagate the damage through the continuum solid. For this study, the Disk-Shaped Compact Tension specimen geometry, normed by the D7313-13 of the ASTM, is used. Results showed that the numerical methods provide good approximation of the experimental curve in the elastic and softening branches.
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