Study on the Seismic Performance of Prefabricated Single-Segment Steel Jacket Bridge Piers

To study the seismic performance of prefabricated single-segment steel jacket piers connected by grouting sleeves, two scaled symmetrical pier models with different anchorage lengths of the longitudinal reinforcement in the grouting sleeves and a comparative symmetrical cast-in-place (CIP) model were designed. OpenSees finite element models were established and shaking table tests were carried out on the three scaled pier models. The seismic response of each pier was compared and analyzed. Results showed the stiffness of the two prefabricated piers was greater than that of the CIP pier, and other seismic responses were less than those of the CIP piers, The dynamic responses of the two prefabricated bridge models were similar and changing the anchorage length of the reinforcement in the grouting sleeve had little effect on the seismic performance of the prefabricated pier. The simulation results were in good agreement with the experimental results. In the parameter analysis, the counterweight of the pier top had the greatest influence on the seismic performance of the prefabricated pier. The anchorage length of the longitudinal reinforcement in the grouting sleeve could be 6–14 times the diameter of the longitudinal reinforcement. Moreover, the seismic performance was found to be optimal when the thickness of the steel jacket was 5–7 mm.

Diseño por desempeño del reforzamiento sísmico de la Biblioteca Agrícola Nacional mediante el uso de métodos no convencionales

En esta investigación se plantea el reforzamiento estructural de una edificación de concreto armado con más de 50 años de antigüedad. La estructura está conformada por pórticos y muros, teniendo un área de construcción de 1980 m2 y 4 niveles con altura total de 15.50 m. Además, se evalúa tres tipos de reforzamiento para la estructura antigua dando como propuesta final para el reforzamiento una de las alternativas presentadas. La primera alternativa de reforzamiento consiste en el uso de planchas de Steel Jacket con pernos de anclajes post instalados de Polímero Reforzado con Fibra de Carbono (CFRP) en columnas, la segunda alternativa consiste en el uso de planchas de CFRP con anclajes de CFRP en columnas mientras que la tercera alternativa consiste en el uso de planchas de CFRP en diagonal con anclajes de CFRP en sus extremos para asegurar que estas láminas resistan hasta sus alto niveles de tensión. Estos anclajes junto con las láminas en diagonal aportan a dar ductilidad al muro y a su vez resistan los efectos de deslizamiento en la base, falla que es muy común en estructuras rígidas como los muros. Cada metodología no convencional de reforzamiento usada en esta investigación se valida a través de resultados de ensayos de laboratorio de columnas y muros reforzados mediante las técnicas de cada una de las tres alternativas mencionadas. Se realizaron análisis estático no lineal – Pushover de cada alternativa de reforzamiento y se comparó con demanda del sismo de 1974 en Lima, escalando 3 registros sísmicos a un PGA de 0.45g que es la aceleración de diseño en Lima. Se demuestra que estas propuestas son efectivas para proporcionar incremento de capacidad de corte y desplazamiento en el diseño inelástico. Para el reforzamiento en columnas de 0.40mx0.80m los resultados muestras que ambos reforzamientos aumentan la ductilidad en más del 10%; por otro lado, la propuesta de reforzamiento en los muros de 40.00cm de espesor, produjo incluso mejores resultados aumentando la ductilidad en 100% y corte en la base en 100%.

Experimental Research on Reinforced Concrete Columns Strengthened with Steel Jacket and Concrete Infill

Experimental research on axially compressed columns made from reinforced concrete (RC) and RC columns strengthened with a steel jacket and additional fill concrete is presented in this paper. A premade squared cross-section RC column was placed inside a steel tube, and then the space between the column and the tube was filled with additional concrete. A total of fourteen stub axially compressed columns, including nine strengthened specimens and five plain reinforced concrete specimens, were experimentally tested. The main parameter that was varied in the experiment was the compressive strength of the filler concrete. Three different concrete compression strength classes were used. Test results showed that all three cross-section parts (the core column, the fill, and the steel jacket) worked together in the force-carrying process through all load levels, even if only the basic RC column was loaded. The strengthened columns exhibited pronounced ductile behavior compared to the plain RC columns. The influence of the test parameters on the axial compressive strength was investigated. In addition, the specimen failure modes, strain development, and load vs. deformation relations were registered. The applicability of three different design codes to predict the axial bearing capacity of the strengthened columns was also investigated.

Structural Response of Steel Jacket-UHPC Retrofitted Reinforced Concrete Columns under Blast Loading

The lateral capacity of exterior concrete columns subjected to a blast load is the key factor in the building collapse probability. Due to potentially severe consequences of the collapse, efforts have been made to improve the blast resistance of existing structures. One of the successful approaches is the use of ultra-high-performance-concrete (UHPC) jacketing for retrofitting a building’s columns. The columns on the first floor of a building normally have higher slenderness due to the higher first story. Since an explosion is more likely to take place at the ground level, retrofitting the columns of the lower floors is crucial to improve a building’s blast resistance. Casting a UHPC tube around a circular RC column can increase the moment of inertia of the column and improve the flexural strength. In this study, a retrofitting system consisting of a UHPC layer enclosed by a thin steel jacket is proposed to improve the blast resistance of buildings in service. Most of the previous research is focused on design aspects of blast-resistant columns and retrofitting systems are mostly based on fiber reinforced polymers or steel jackets. A validated FE model is used to investigate the effectiveness of this method. The results showed significant improvement both at the component and building system levels against combined gravity and blast loading.

Comparative Study of Seismic Response of Short Columns Retrofitted by Steel Jacket, brick wall and FRP Fiber

Using inter-frame walls sometimes leads to the structure fortification in time of earthquake, but sometimes leads to plastic joint in the column which leads to the structure destruction. Therefore, the purpose of this work is to study and retrofit columns of inter-frame walls of deficient two-story structure, where he was taken in this research four models (Simple, With brick, With FRP, With Steel Jacket). In this work we look for the best retrofitting state of columns of half inter-frame wall by different states of retrofitting including FRP fibers and steel jackets. The analytical method used in this research is nonlinear elastic analysis by ABAQUS Software program. The results were extracted for the shear force with respect to the displacement of the static loads, and the displacement with respect to time was also extracted into the live loads of the four models. It was found that the presence of retrofitting of short shafts using steel jacket and FRP leads to a 3-40% increase in concrete bending framework in the section of shear strength and earthquake resistance.