Thesis USO DE RIOSTRAS RESTRINGIDAS AL PANDEO COMO FUSIBLES ESTRUCTURALES EN PUENTES DE HORMIGÓN ARMADO
Date
2018
Authors
COMICHEO BAHAMONDE, JOCELYN GABRIELA
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Abstract
Despues de un terremoto es vital mantener la continuidad operacional de los puentes, tanto para atender las zonas críticas como por razones economicas. En este contexto, la presente memoria de ttulo propone un refuerzo sísmico de puentes usando Riostras Restringidas al Pandeo (BRB), las cuales consisten en un nucleo de acero con un encamisado de hormigon, que permite una disipacionde energa estable tanto en traccion como en compresion y es capaz de reducir desplazamientos relativos entre subestructura y superestructura. Las BRB se dise~nan como fusibles estructurales, elementos sacri cables, de facil reemplazo y bajo costo, los cuales disipan energa localizadamente en un terremoto mientras la estructura principal se mantiene elastica o con pequeñas incursiones no lineales.La efectividad del metodo propuesto se evalua numericamente en dos puentes chilenos: uno que colapso en el terremoto del Maule del 2010 y otro construido el a~no 2012. Ambos puentes se comparan en diversas condiciones (previo al 2010, actual y con reforzamiento propuesto), considerando los resultados obtenidos de analisis estaticos no lineales como medidas del desempeño de los elementos estructurales mas importantes. Adicionalmente se realiza un analisis de sensibilidad para evaluar la influencia del area de las BRB en las medidas de desempeño del puente.Los analisis realizados indican que el refuerzo con BRB permite modi car convenientemente el comportamiento de los puentes acorde a distintos objetivos, ya sea manteniendo a la estructura principal en el rango elastico o bien permitiendo pequeñas incursiones no lineales. Tambien se observo reduccion del daño en los elementos principales, tales como apoyos elastomericos, mesa de apoyo y cepa. Ademas, se disminuyeron considerablemente los desplazamientos relativos entre tablero y la subestructura que permitira, eventualmente, reemplazar los topes ssmicos en los puentes por BRB. Como resultado principal de este trabajo, se muestra que utilizar riostras restringidas al pandeo como refuerzo de estructuras similares a las estudiadas mejora considerablemente el desempeño de sus elementos principales, ayudando as a proteger la continuidad operativa de puentes carreteros.
It is vital to keep the operational continuity of bridges after an earthquake, for both sending help to critical zones and recovering the economy of the affected communities. Regarding that objective, this thesis proposes a seismic retro t of bridges using Buckling Restrained Braces (BRB). The main characteristic of these elements is the steel core surrounded by a concrete casing, allowing stable energy dissipation (in tension and compression) and reducing the drifts between substructure and superstructure. The BRB are designed as structural fuses; in other words, they are expected to be cheap, self sacri cable and easy-to-replace elements. Structural fuses dissipate energy in a concentrated manner during an earthquake, whereas the main structure remain elastic or with minor non-linear incursions.The effectiveness of the proposed method is numerically assessed in two Chilean bridges: one that collapsed during the Maule Earthquake of 2010, and one built in 2012. Both bridges are compared in several conditions (as-built, with the actual retro t, and with the proposed retro t), considering results obtained from non-linear static analyses as measures for the performance of the most important structural elements. Besides, a sensitivity analysis is conducted to evaluate the influence of the area of the BRBs in the bridge performance.The conducted analyses show that retro tting with BRB allows to conveniently modify the behavior of bridges regarding different objectives, either maintaining the main structure in the elastic range, or allowing small non-linear incursions. Also, reduction of damage in the principal elements of bridges (elastomeric bearing, seat and bent) was observed. Besides, a considerable reduction of drifts between substructure and deck was achieved, which would permit to directly replace shear keys by BRBs. As a main result of this work, it was concluded that using buckling restrained braces as retro t of structures similar to those studied greatly improves the performance of the main elements, thus helping to protect the operational continuity of road bridges.
It is vital to keep the operational continuity of bridges after an earthquake, for both sending help to critical zones and recovering the economy of the affected communities. Regarding that objective, this thesis proposes a seismic retro t of bridges using Buckling Restrained Braces (BRB). The main characteristic of these elements is the steel core surrounded by a concrete casing, allowing stable energy dissipation (in tension and compression) and reducing the drifts between substructure and superstructure. The BRB are designed as structural fuses; in other words, they are expected to be cheap, self sacri cable and easy-to-replace elements. Structural fuses dissipate energy in a concentrated manner during an earthquake, whereas the main structure remain elastic or with minor non-linear incursions.The effectiveness of the proposed method is numerically assessed in two Chilean bridges: one that collapsed during the Maule Earthquake of 2010, and one built in 2012. Both bridges are compared in several conditions (as-built, with the actual retro t, and with the proposed retro t), considering results obtained from non-linear static analyses as measures for the performance of the most important structural elements. Besides, a sensitivity analysis is conducted to evaluate the influence of the area of the BRBs in the bridge performance.The conducted analyses show that retro tting with BRB allows to conveniently modify the behavior of bridges regarding different objectives, either maintaining the main structure in the elastic range, or allowing small non-linear incursions. Also, reduction of damage in the principal elements of bridges (elastomeric bearing, seat and bent) was observed. Besides, a considerable reduction of drifts between substructure and deck was achieved, which would permit to directly replace shear keys by BRBs. As a main result of this work, it was concluded that using buckling restrained braces as retro t of structures similar to those studied greatly improves the performance of the main elements, thus helping to protect the operational continuity of road bridges.
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Keywords
ANALISIS ESTATICO NO LINEAL , EVALUACION POR DESEMPENO , EVALUACION SISMICA DE PUENTES , FUSIBLE ESTRUCTURAL , REFORZAMIENTO SISMICO , RIOSTRA RESTRINGIDA AL PANDEO