Thesis HACIA LA REDUCCIÓN DE PÉRDIDAS EN LA CONSTRUCCIÓN: MEJORAS EN EL PROCESO CONSTRUCTIVO DE VENTANAS
Date
2016
Authors
SCHUCK PARRA, SASHA
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Abstract
Numerosos estudios acerca de la industria de la construcción destacan los altos riesgos de accidentes, problemas con la baja calidad y las altas pérdidas de tiempo y materiales (denominadas pérdidas productivas o muda del japonés). El objetivo principal de esta tesis es estudiar el efecto de aplicar el concepto de la eliminación preventiva de las pérdidas, o cero pérdidas, en un proceso constructivo en Chile.El proyecto comienza con revisar los principios, la historia y los resultados recientes de aplicar el concepto cero pérdidas en la construcción. A su vez, se presenta un modelo integrado de los procesos de la construcción, el cual tiene como característica principal la disponibilidad de datos e información del trabajo en curso y de los recursos. Algunos instrumentos que permiten generar dichos flujos de información son presentados. Adicionalmente, se presentan numerosos estudios que han demostrado que la prefabricación es una metodología constructiva eficiente que resulta en una reducción de las pérdidas.El trabajo se enfoca en evaluar el impacto del uso inapropiado del encofrado de términos de muro que originan vanos de ventanas, en la estandarización de las ventanas prefabricadas de edificios habitacionales en altura de hormigón. En esta tesis se postula que la calidad de los vanos de hormigón hechos in situ no permiten la implementación de la fabricación en serie de las ventanas. La consecuencia, es que éstas se deben hacer a la medida, resultando en un mayor costo unitario y en un mayor tiempo de fabricación.La metodología de investigación consta de cuatro etapas. La primera, es realizar un trabajo en terreno para identificar la causa fundamental del problema. Para ello, en base a exhaustivas observaciones, se genera un modelo integrado de los procesos relacionados a las ventanas, y un modelo causa-efecto. En base a los modelos, se determina la causa principal del problema: la falta de un soporte para el molde de las jambas en términos de muro. Esto debido a que el encofrado se utiliza de forma distinta para el cual fue diseñado cuando la longitud de los muros no coincide con la modulación de los paneles de moldaje, recurriendo a sistemas de soporte rudimentarios ideados en obra.La segunda etapa de la metodología, presenta cómo se cuantificarán las pérdidas que son consecuencia del problema estudiado. En la etapa tres, se presenta el estudio, diseño y desarrollo de un nuevo soporte para reemplazar al rudimentario empleado en la práctica, con el objetivo de eliminar la causa principal del problema para el caso de vanos originados en términos de muro.Las pruebas del prototipo final del soporte fabricado, en la cuarta etapa, demostraron que la resistencia es inferior a la requerida, la cual es calculada mediante el análisis de las fuerzas provenientes de la presión del hormigón durante el vertido. Esto implica que el soporte debe ser mejorado antes de ser implementado en terreno. Sin embargo, si se mejorara y aplicara en obra, permitiría que las ventanas ubicadas en términos de muro fueran prefabricadas en masa, junto con eliminar los daños al encofrado y la necesidad de reparar cada vano. Se calcula que esto resulta en una reducción de un 14,9% las pérdidas en términos del costo unitario de ventana instalada, lo cual representa aproximadamente un 0,6% del costo total del edificio.
Many governmental and investigative reports about the construction industry point to the high safety risks, problems with quality and the high physical and time wastes (from the Japanese concept, Muda). The objective of this thesis is to study the effect of applying the concept of preventive waste elimination, zero waste, to a construction process in Chile.The project starts with reviewing the principles, the history and the recent results obtained of applying the zero waste concept in construction. Also, an integrated model of the construction processes will be shown, highlighting its key element; the availability of data and information related to the quality of the work-in-progress and the resources. Consequently, some example tools to produce the data will be shown. Additionally, numerous studies have also demonstrated the benefits of prefabrication as an effective method to achieve waste reduction.The focus of the work is to assess the result of bad quality of concrete wall formwork around window openings on the standardization of prefabricated windows for high rise concrete buildings. The thesis asserts that the quality of the concrete openings built on-site prohibit the implementation of standardization in the factory. The consequence, is that custom size windows have to be built, costing considerably more money and more time to build.The research methodology consists of four stages. The first one, is the field work to identify the key cause-and-effect relationship related to poor quality openings. In order to achieve this, two models are designed though extensive observations; an integrated window-related processes model, and a fishbone diagram of the problem. Using both models, the key cause was determined: the lack of an adequate support for the stop-end wall form. The problem occurs when the length of a wall section does not match any form size combinations, forcing the use of a rudimentary on-site made support system to overcome this issue.The second stage of the methodology presents how the waste that is consequence of the problem is going to be quantified. The third stage contains the study, design and development of a new support, intended to replace the rudimentary on-site made one used traditionally, with the objective to eliminate the key cause.The tests conducted on the final prototype fabricated, shown in the fourth stage, demonstrated that the measured strength it is lower than the required design value, which was calculated through an analysis of loads caused by the lateral pressure of fresh concrete. This implies that the support must be improved before being implemented in the field. Nevertheless, if it is improved and used, it would allow the incorporation of mass prefabricated windows, along with preventing the formwork damage and the required repairs of each opening caused by the current system. Based on this analysis, a 14,9% waste reduction calculated in terms of the cost per m2 of installed window can be achieved, which represents around a 0,6% of the total cost of a building.
Many governmental and investigative reports about the construction industry point to the high safety risks, problems with quality and the high physical and time wastes (from the Japanese concept, Muda). The objective of this thesis is to study the effect of applying the concept of preventive waste elimination, zero waste, to a construction process in Chile.The project starts with reviewing the principles, the history and the recent results obtained of applying the zero waste concept in construction. Also, an integrated model of the construction processes will be shown, highlighting its key element; the availability of data and information related to the quality of the work-in-progress and the resources. Consequently, some example tools to produce the data will be shown. Additionally, numerous studies have also demonstrated the benefits of prefabrication as an effective method to achieve waste reduction.The focus of the work is to assess the result of bad quality of concrete wall formwork around window openings on the standardization of prefabricated windows for high rise concrete buildings. The thesis asserts that the quality of the concrete openings built on-site prohibit the implementation of standardization in the factory. The consequence, is that custom size windows have to be built, costing considerably more money and more time to build.The research methodology consists of four stages. The first one, is the field work to identify the key cause-and-effect relationship related to poor quality openings. In order to achieve this, two models are designed though extensive observations; an integrated window-related processes model, and a fishbone diagram of the problem. Using both models, the key cause was determined: the lack of an adequate support for the stop-end wall form. The problem occurs when the length of a wall section does not match any form size combinations, forcing the use of a rudimentary on-site made support system to overcome this issue.The second stage of the methodology presents how the waste that is consequence of the problem is going to be quantified. The third stage contains the study, design and development of a new support, intended to replace the rudimentary on-site made one used traditionally, with the objective to eliminate the key cause.The tests conducted on the final prototype fabricated, shown in the fourth stage, demonstrated that the measured strength it is lower than the required design value, which was calculated through an analysis of loads caused by the lateral pressure of fresh concrete. This implies that the support must be improved before being implemented in the field. Nevertheless, if it is improved and used, it would allow the incorporation of mass prefabricated windows, along with preventing the formwork damage and the required repairs of each opening caused by the current system. Based on this analysis, a 14,9% waste reduction calculated in terms of the cost per m2 of installed window can be achieved, which represents around a 0,6% of the total cost of a building.
Description
Catalogado desde la version PDF de la tesis.
Keywords
ACCESORIOS DE ENCOFRADOS , CERO PERDIDAS , MOLDAJE DE TERMINO DE MURO , PREFABRICACION