Seismic Design, Assessment and Retrofitting of Concrete Buildings

Abstract

This chapter is the only one in the book devoted exclusively to existing concrete buildings. It builds on:-Chapter 1, for the seismic performance requirements that may be apply to existing buildings and to their upgrading, -Chapter 2, for the demonstration of the inherent vulnerability of substandard existing buildings, -Chapter 3 for the quantification of the cyclic force and deformation capacity of concrete members, including the effect of poor detailing or retrofitting, and on -Chapter 4 for the estimation of the seismic response via (mainly nonlinear)analysis.The first part of the chapter is mainly devoted to seismic assessment of the as-is building. The rest to its upgrading through appropriate and cost-effective retrofitting. One section, namely Section 6.5, is specific to Part 3 of Eurocode 8. Retrofitting strategies and techniques commonly used today and in the foreseeable future for a concrete building as a whole and for its members, respectively, are described and their scope, pros and cons highlighted. Procedures, rules and expressions are given for practical member retrofit design. Finally, practical retrofitting is illustrated through two real applications.

Behavior of Concrete Panels Reinforced with Synthetic Fibers, Mild Steel, and GFRP Composites Subjected to Blasts

“…The results of the tests are described based on three performance categories: (a) immediate occupancy, (b) life safety, and (c) near collapse. These categories are accepted in performance based seismic design (Fardis 2009) and are proposed here for blast evaluation. Post-blast testing was performed on nine panels that confirmed the definition of the performance categories.…”

Stiffness Modeling of Rc Columns Reinforced With Plain Rebars

“…However, for the columns under high axial load ratio, the development of slip induced deflections was not permitted as much as the columns under low axial load and the slip contribution can be expected to be higher for lapspliced columns regarding the lower bond stress levels. The outcomes of the previous research [20][21][22] claimed the influence of poor bond performance of plain rebars on the yield deflection, yield strength and effective stiffness of RC columns to be insignificant considering a database including 20 columns reinforced with plain rebars.…”

“…Considering the inadequate bond strength along plain rebars that inhibited the full mobilization of yield strength, the yield moments were overestimated with an experimental to prediction ratio of 0.95 [20] and it can be anticipated that the development of yield strength can be inhibited further for lap-spliced columns as compared to the columns with continuous rebars. Thus, this phenomenon was found to be responsible for the reduced mean levels for yield moments (0.92 and 0.69 for continuous and lap-spliced, respectively) with a low scatter as shown in Fig.…”

“…3c -3d). However, the effective stiffness and yield properties of the columns should be evaluated while preventing shear force underestimations or displacement demand overestimations for low effective stiffnesses [7,20]. The chord rotations at yield ( ) were computed accordingly with the components of flexure, shear and bond slip (Table 1) in order to determine the effective stiffnesses that were overestimated beyond axial load ratios of approximately 0.2 ( Fig.…”

Seismic performances and behaviour factor of wide-beam and deep-beam RC frames

“…NCSE-02 does not consider any contribution; conversely, EC8 suggests considering it, but no clear modelling strategy is proposed. Fardis [39] suggests placing only rigid offsets in beams, leading to a decrease of elastic stiffness which is proportional to beam depths, so it is higher for DBF rather than WBF. Such behaviour is coherent with the experimental evidences [40], and it is adopted herein for EC8 structures.…”