Juan M. Mayoral

Determination of Multidirectional p-y Curves for Soft Clays

The evaluation of performance of soil-pile-structure systems under seismic loading is one of the most complex problems in earthquake engineering. In the most common methodology, force-displacement curves are used to describe the nonlinear response of discrete soil springs connecting the piles to the “free-field” soil column using the concept of beam on nonlinear Winkler foundation. Although there is a great interest and on-going research to characterize the multi-directional “free-field” soil response, there is a lack of information and experimental data to formulate p-y curves in multi-directional loading conditions. A new testing device was designed and constructed to obtain high quality data to calibrate numerical tools used to evaluate the seismic performance of structures supported on deep foundations in soft clay. A suite of different ground displacement path scenarios observed during recent earthquakes was simulated to assess the effect of displacement history on measured p-y response.

Advanced 3-D Seismic Soil-Structure Interaction Analysis of a Cellular-Raft Foundation in Soft Clay

Seismic soil-structure interaction performance evaluations of projects located in deep soft clay deposits warrant special attention, particularly when designing strategic infrastructure that must remain operating after a major earthquake. The development of numerical analytical platforms in recent decades, along with faster computing tools, have made possible to include in the state of practice quite sophisticated solution techniques aimed at better representing the physics of the problem at hand. This paper presents the application of a 3-D finite difference model for evaluating the static and dynamic response of a 118 by 100 m cellular-raft foundation to be built in soft clay. The raft foundation is a 2.5 m high box-type foundation embedded 1 m and supported by a grid of peripheral and internal walls, 2.5 m long and 0.40 m thick, which integrates a cellular structure. The model is used to obtain first the static behavior exhibited by the foundation for the construction stages, including long term consolidation, and then the design earthquake is considered and the equation of motion is solved in time domain.

Modeling Urban Transfer Stations Efficiency

Abstract Efficiency estimation of transit transfer stations (TTS) in densely populated urban areas is a mandatory step to define proper sustainable public transportation networks. However, due to the lack of data and the complexity of the operation patters, efficiency assessment is a cumbersome task in practice. This paper presents a novel approach to establish relative efficiencies in order to optimize TTS operation and design. Using the Data Envelopment Analysis method (DEA) three key efficiency dimensions are studied, which corresponds to the pillars of sustainability: technical, social and environmental. Efficiencies were computed using a database generated including 39 TTS located in Mexico City Metropolitan Area. Results show that none of the stations analysed are completely efficient considering the three dimensions simultaneously. Technically efficient TTS are those attending the highest number of passengers in a smallest given area. Social efficient TTS are those that provide enough services, such as automatization, multiple transport modes, and low transfer time, leading to high levels of users satisfaction. Finally, environmental efficient TTS correspond to those registering low values of air polluting emissions per passenger mainly due to the presence of non-oil fuel transport modes. In developing countries in Latin American and Asia, the application of this kind of models represent an excellent tool for the computation and understanding of TTS operations.

Modeling soil-pile interaction under axial loading using a bilinear Mohr-Coulomb based model

It is common practice to rely on traditional relationships to compute the bearing capacity of deep foundations. In particular, when dealing with piles is essential to calibrate the load-displacement response, both for axial and lateral loading and to define the load transfer mechanism at the pile tip and along the shaft. These calibrations allow to reduce uncertainties and to design less expensive and safer foundations. The objective of this paper is to simulate the mechanical response obtained from a load test performed in a real scale cast in place concrete pile embedded in alluvial sand, using a 3D finite differences model. The pile was instrumented to monitor directly the reaction along its shaft and tip. The interface was modeled using a shear coupling-spring with frictional resistance. Both the soil and the pile were represented with four nodes axi-symmetric elements. The stress-strain behavior of the soil and soil-pile interface was described with a bilinear MohrCoulomb constitutive law. Although the simplicity of the bilinear model, good agreement was observed between the measured and computed responses when monotonic increasing loading was applied (i.e. static conditions). However, the bilinear constitutive model largely underestimates the measured permanent deformations prevailing in the pile-soil system after unloading. This should be accounted for when analyzing the dynamic response of the soil-pile system.

A novel approach for transit transfer stations design optimization in densely populated cities

Abstract Efficiency assessment of transit transfer stations (TTS) located in densely populated urban areas is one of the most challenging tasks for metropolitan mobility entities. Currently the lack of practice oriented tools and the complexity of operation patterns make this kind of evaluations a fuzzy process. This paper presents a novel, integral and sustainable approach to evaluate relative TTS efficiency using technical, social and environmental variables. The methodology proposed is based on an optimization model using Data Envelopment Analysis (DEA). A set of operation variables are defined and efficiency frontier curves are developed in order to stablish optimal operation values. 36 TTS located in Mexico City Metropolitan Area (MCMA) are presented as case study. Findings point that TTS medium size stations are more suitable to reach a better balance among technical, social and environmental objectives. This methodology represents a useful tool to assess the different operational elements of TTS to improve the whole station efficiency.

Integral Approach of Performance-Based Design for Tunnels

Over the past 50 years, tunnel design engineering—driven mainly by construction techniques and equipment specialization in mechanized tunneling, enhancement of computational tools, and development of sophisticated numerical analysis frameworks—has significantly advanced. Furthermore, performance observation throughout instrumentation of hundreds of tunnels around the world, including many well-documented famous failures, has provided a large amount of data regarding current design criteria shortcomings. Initially, this paper presents a revision of existing analysis design criteria based on the observation of actual tunnel behavior and points out the limitations. In a second part, an integral approach of performance-based design and the assessment of potential damage on surrounding structures is presented. The method is exemplified by a case study.