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Soil response analyses require that the soil strata involved be characterized in terms of their dynamic material properties. Two important material properties are the shear modulus and a measure of energy dissipation characteristics, usually expressed as the damping ratio. Both can be obtained from standard laboratory tests, most commonly resonant columns or cyclic triaxial devices which provide strain-dependent values. Alternative experimental procedures are now available to estimate shear moduli at very small strains from piezoelectric transducer tests (bender elements); procedures have also been put forth to obtain the energy dissipation properties from this test. In this paper, we present a modified version of the spectral-ratio method using the wavelet transform to measure the damping ratio at small strains from waveforms acquired from bender element tests. Synthetic bender element signals were first used to test the procedure and validate the approach. Then, we analyzed signals obtained from a large-size oedometer equipped with bender elements on very soft Texcoco Clays (near Mexico City), and the waveforms were propagated along different paths. Our results show that the range of values of D min obtained from bender element tests agrees well with those obtained from resonant column tests performed on very soft clayey soil specimens retrieved from the same area at different depths. • This research is aimed to study the damping ratio on very soft soil Texcoco Clays (near Mexico City) using a large-size oedometer equipped with piezoelectric transducers. • We propose a modified version of the spectral ratio method for assessing the damping ratio at very small strains (elastic behavior). • It is calculated synthetic waveforms which input data are similar to the soil deposits present in the area where the specimens were retrieved. • We compare the data obtained with the modified version of the spectral ratio concerning to resonant column tests. [ABSTRACT FROM AUTHOR]

In this paper, the authors propose and validate a code-oriented, resilient design methodology for reinforced concrete buildings with intermediate moment frames (RC-IMFs) and hysteretic energy dissipation devices (HEDDs) mounted in chevron steel bracing design as structural fuses, considering soil-structure effects. The design methodology is based on global lateral stiffness balances among different structural components (frames, bracings and HEDDs). Global seismic design parameters were specifically assessed for such stiffness ratios through extensive parametric studies for the subject structural system under study. In order to achieve an immediate occupancy seismic performance, the design sequence using capacity-design principles is clearly established and emphasized for the design of main structural elements. Soil-structure interaction (SSI) effects are included in the formal design process following the recommendations available in the seismic code for Mexico City. In order to fully test the efficacy of the proposed design methodology under a demanding seismic scenario, three buildings of 8, 15 and 24 stories were designed in soft soil sites of Mexico City close to resonant responses. Different types or HEDDs were considered and evaluated. Pushover analyses were performed in order to verify that subject buildings may achieve the objective resilient deformation mechanism (immediate occupancy) at the maximum useful ductility capacity assumed for the HEDDs. Nonlinear dynamic analyses were performed for the complete 3D designs according to the code under the action of eight pairs of acceleration records, representative of the site where the buildings were located. This was done in order to assess maximum inelastic demands, residual drifts, and fully verify and validate the proposed resilient, structural fuse code-oriented design. From the obtained results, it is confirmed that a resilient structural performance is feasible for RC-IMFs with HEDDs under the proposed code-oriented design methodology. • A code-oriented, resilient seismic design procedure for RC-IMRFs with HEEDs is presented. • An immediate occupancy category is achieved for RC-IMRFs with HEEDs for the MCE scenario. • SSI effects were included in the design procedure and evaluated with real soft soil properties of Mexico City. • Peak displacements and base shears of buildings were amplified (up to 21%) when considering SSI effects. • Practical values for assessed global design parameters are proposed for their insertion in Mexican and international codes. [ABSTRACT FROM AUTHOR]