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CHAIRS: A choice-based air transport simulator applied to airline competition and revenue management
(2022) Fukushi Estay, Mitsuyoshi Andres; Delgado Breinbauer, Felipe Alberto; Raveau Feliú, Sebastián; Santos, Bruno F.
In Revenue Management (RM) systems, information censoring and the interaction between the forecasting and optimization stages, increases the costs and complexity of performance analysis using historical data. An affordable and suitable alternative is using simulations, but appropriate behavioral models must be considered. In the following document, we discuss and test the implementation of a dynamic air transport market simulator, designed to analyze RM systems. The simulator replicates the behavior of passengers that book seats offered in multiple flights by different airlines. We use discrete choice models to replicate the demand behavior, accounting for preferences and decision rule heterogeneity, and including a temporal evolution of the preference throughout the selling horizon. To replicate the supply behavior, a number of airlines modify the price and quantity of different fare classes offered in each flight, using a variety of RM forecasting, un-constraining, and optimization techniques. The simulator allows analysts to study the economic benefit of RM systems under predefined assumptions in an artificial and controlled environment. This increases the benefits obtained by the correct selection of context-appropriate RM systems and the likelihood of successfully implementing new and complex systems. We test and showcase the simulator performance, studying the entrance of a new airline in a competitive context. We generate, implement and evaluate different RM strategies in response to the introduction of new competition, and discuss the results, highlighting the interpretability and accuracy of the proposed framework.
Fare evasion on public transport: Who, when, where and how?
(2022) Cantillo Torregrosa, Luis Ángel; Raveau Feliú, Sebastián; Muñoz Abogabir, Juan Carlos
Transantiago, the public transport system of Santiago, Chile, has one of the highest fare evasion rates registered worldwide. The official statistics for late 2019 indicated that the evasion rate in bus legs was 26.6% while in metro it was almost 0%. This is a relevant issue due to the impacts of fare evasion on finances and quality of service, as budget constraints put pressure on the transit system. Analysing and understanding fare evasion should be the starting point for proposing solutions that could reduce it. Therefore, in this research we seek to answer the question of who are the evaders, when and where evasion happens and how is the fare evaded on public transport. To answer these questions, extensive data was gathered onboard buses of Transantiago for five full days (19 h a day) of operation, including weekdays and weekend. A total of 10,559 individual records were collected. The information considers age and gender of travellers, and fare evasion was measured in zones of Santiago that are characterised by very different economic conditions. Records also differ in terms of bus occupancy, presence of turnstiles in the buses, and types of stops (with and without off-board payment). Based on the collected information, a Binomial Logit model was calibrated to understand and explain fare evasion, quantifying the effect of different types of explanatory variables. Results show that fare evasion is higher for young men, evening and night periods, low-income neighbourhoods, crowded buses without turnstiles, bus stops without off-board payment and weak accessibility to metro stations and fare vending machines. The model does not only allows the identification of these trends, but is also able to quantify them. Based on the results, potential proposed solutions to tackle evasion are discussed.
Inclusion of latent variables in Mixed Logit models: Modelling and forecasting
(2010) Yáñez Castillo, María Francisca; Raveau Feliú, Sebastián; Ortúzar Salas, Juan de Dios
Travel demand models typically use mainly objective modal attributes as explanatory variables. Nevertheless, it has been well known for many years that attitudes and perceptions also influence users' behaviour. The use of hybrid discrete choice models constitutes a good alternative to incorporate the effect of subjective factors. We estimated hybrid models in a short-survey panel context for data among many alternatives. The paper analyses the results of applying these models to a real urban case study, and also proposes an approach to forecasting using these models. Our results show that hybrid models are clearly superior to even highly flexible traditional models that ignore the effect of subjective attitudes and perceptions.
Incremental construction: a strategy to facilitate access to housing
(International Institute for Environment and Development (IIED), 2008) Greene, Margarita; Rojas, Eduardo
The "enabling" approach to housing markets promotes financing systems based on family savings, public subsidies and mortgage loans to unleash the potential of individuals and communities to produce and improve dwellings. However, the approach failed to benefit lower-income households, as they have less ability to generate savings or make mortgage payments. These households are forced to use informal mechanisms to access housing, such as purchasing land in illegal sub-divisions or squatting on public land and incrementally building their dwellings. The present work argues that supporting the incremental housing construction undertaken by poor households through an enabling approach can make a significant contribution to solving the housing problem in Latin America. The paper discusses the challenges and opportunities in executing this new type of programme, which requires coordinating the resources and capabilities of the beneficiaries with those of the different levels of government and the civil society. While this paper draws on experiences in Latin America and the Caribbean, the proposed approach is also relevant in other settings.
Preliminary Assessment on Seismic Vulnerability of Masonry Churches in Central Chile
(2019) Palazzi Chiara, Nuria; Llera Martin, Juan Carlos de la; Sandoval Mandujano, Cristian
The 2010 Maule Chile earthquake (Mw 8.8) caused extensive structural damage to the built heritage. In particular, the poor seismic performance of a set of unreinforced masonry (URM) churches highlighted the need to implement protective and safety strategies in order to preserve these buildings which exhibit unique constructive and typological features, as a result of a combination of Chilean and European construction cultures. The peculiarity of this heritage and the high seismic hazard of Chilean territory have motivated the present study which aims to apply systematic procedures to assess the seismic vulnerability of these buildings. This article is of archival nature and presents a complete database generated from the geometrical, constructive, and structural characteristics of a representative stock of 106 churches located in central Chile, with the goal of proposing fragility curves to be used in seismic risk assessment. Considering variables related with geometrical, architectonic, and stylistic features, as well as damage levels for the 2010 Maule earthquake, this church sample is classified into three homogenous groups: colonial, neo-classic, and neo-gothic. Moreover, a preliminary qualitative assessment of the seismic capacity of these structures is provided using a survey and analysis of geometric indices for each of the three selected groups.
Rupture parameter sensitivity of low frequency ground motion response spectra using synthetic scenarios in North Chile
(SPRINGER, 2021) Fortuño Jara, Catalina Pía; Llera Martin, Juan Carlos de la; Gonzalez, Gabriel; Gonzalez, Juan; Aguirre Aparicio, Paula
This research performs a sensitivity analysis of response spectrum values for various physical earthquake parameters, which are used to generate synthetic seismograms consistent with the expected seismicity in north Chile. Sensitivity analyses are based on the earthquake scenario and slip distribution model of the 2014, M-w 8.1 Pisagua earthquake, and seven other physically plausible interplate events for north Chile. A finite-fault rupture model, and slip distribution of the Pisagua earthquake, were obtained using inversion of InSAR and GPS data. Three other rupture models based on previous studies of interplate locking for north Chile and capable of generating M-w 8.3-8.6 earthquakes with an estimated maximum slip of 9.2 m, were incorporated in the analyses. Also, four additional scenarios with moment magnitudes in the range M-w 8.6-8.9 were generated by concatenating these physical scenarios into larger rupture areas within the north segment. Using these scenarios, synthetic ground motions were built at four observation sites: Pisagua, Iquique, Tocopilla, and Calama. Response sensitivity was studied for three key rupture parameters: mean rupture velocity, slip rise-time, and rupture directivity. Responses selected were peak ground displacement (PGD), spectral pseudo-velocities, S-v, and spectral displacements, S-d. First and second order variations of PGD, S-v, and S-d relative to the source parameters were computed and used together with a Taylor series expansion to propagate uncertainty into the responses as a function of v(r) and rise-time t(r). To study the effect of rupture directivity, three different foci locations were considered for each scenario: north, south, and at the centroid of the slip model. Response PGD values show no clear trends with rupture velocity, v(r); however, the variability increases as the system period increases. The effect of the slip rise-time is significant, and as t(r) increases, the spectral responses tend to decrease, suggesting that shorter slip rise-times lead to higher seismic demands in long period structures. The results obtained for the directivity analysis suggest that two factors control the expected waveforms and spectral responses: first, the direction of the rupture relative to the location of each site, and the hypocentral distance.
Tall building vibration control using a TM-MR damper assembly
(WILEY, 2011) Zemp, René; Llera Martin, Juan Carlos de la; Almazán Campillay, José Luis
This research investigates the seismic and harmonic response of a true free-plan tall building equipped with two tuned pendular inertial masses (TMs) and magnetorheological (MR) dampers. Construction of this proof-of-concept building was completed in 2007, and it is the first of its class in Chile. This article provides research results associated with this specific implementation; however, in order to make the results applicable to other building cases a parametric study was considered. A brief description of the structure and TM implementation together with the nonlinear equations of motion of the TM-MR damper assembly are presented. Building displacements and accelerations are computed and analyzed for a suite of subduction-type and near field ground motions. Besides, a new physical controller for the MR dampers is proposed and analyzed. The performance of this controller is compared with that of benchmark LQR controllers. In general, the TM-MR damper assembly improves the lateral performance of this structure for lateral harmonic excitations. However, the expected peak and RMS response modification factors and efficacy of the solution for earthquake excitations are strongly dependent on the frequency content of the excitation. Copyright (C) 2010 John Wiley & Sons, Ltd.

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