Seismic Behavior of Medium and High Strength Concrete Buildings

J.M Bairán,J Peguero,R Moreno-González

doi:10.2174/1874149501509010308

Abstract

Current concrete technology has made higher concrete grades more affordable to mid and high-rise buildings; hence its use has been increasing in the late years as it allows for smaller cross-sections, reduction of the structure’s weight, improve durability, among other benefits. However, it is known that brittleness of plain concrete increases with the strength; therefore, some national codes have limited the concrete’s strength in high seismic zones. In this paper, the seismic behavior of a 10 storey dual frame-wall building, designed with concrete grades C30, C60 and C90 is studied in order to assess the advantages and disadvantages of this material and investigate the effects of high concrete strength on the seismic behavior of buildings. In total, three models were studied. Furthermore, a comparison between Force-Based-Design (FBD) and Displacement-Based-Design (DBD) methodologies is made. DBD showed advantages in determining the adequate design ductility and the distribution of forces between frame and wall. The structures are designed according to Eurocode 8 for seismic design high ductility structures. To assess the seismic performance of the building, pushover analyses were made according to the Eurocode 8 (N2 method) in order to determine the performance point. It is observed that adequate design could accommodate concrete’s reduction of ductility. Needed confinement levels can objectively be defined for different concrete strength. Some benefits of the overall increase of strength are highlighted in the paper. The C90 building showed adequate response, although changes on the failure mode were observed.

Highlights

In recent years the use of high strength concrete (HSC) has become very common in bridges, buildings and some marine structures due to its benefits in terms in increasing strength, durability and stiffness, allowing for larger spans and weight reduction
This paper aims at investigating the effects of concrete strength and design methods in the seismic behavior of concrete buildings
The seismic performance was evaluated by means of a pushover; performance points were obtained using the Eurocode 8 approach

Summary

Introduction

In recent years the use of high strength concrete (HSC) has become very common in bridges, buildings and some marine structures due to its benefits in terms in increasing strength, durability and stiffness, allowing for larger spans and weight reduction. In the case of buildings, the use of HSC is determinant in elements in compression, as columns, where concrete strength plays a major role in the element’s capacity and ductility. In high-rise buildings concrete strength larger than 100 MPa has been used. In the late 80’s decade and at the beginning of the 90’s decade several prominent HSC structures were constructed: in Seattle, a 220 m building was constructed using 115 MPa concrete.

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