Numerical Methods for the Seismic Performance Assessment of Reinforced Concrete Buildings

Considering the fact that similar structural and construction deficiencies which are exposed during the recent destructive earthquake events are existing in many southern European, Middle Eastern and west Asian countries settling on highly seismic zones, designating the seismic adequacy of the existing building stock for providing structural safety is a significant necessitation in the mitigation of losses during the future seismic events. In most of these regions, a clear majority of the building stock has not been adequately designed or constructed in terms of the seismic regulations of the design codes, while some have even not benefitted from engineering services. Post-earthquake site observations demonstrate the insufficient capacities in these buildings depending on different structural and construction deficiencies. Within the scope of this research, it is aimed to investigate and compare the analytically calculated structural performances of a building ensemble consists of 3~5 story structures with known damage level by utilizing different procedures.

A Comparative Investigation of Structural Performance of Typical and Non-Ducitle Public RC Buildings Strengthened Using Friction Dampers and RC Walls

Strengthening of non-ductile public buildings is a never-ending issue. Selection of the suitable strengthening method and appropriate analysis type for the assessment of pre- and the post-intervention performances are still open to question. The displacement or drift limitations are crucial as well as demand capacity ratios for determination of such buildings performance under severe ground motion. In this chapter, an investigation of seismic performance focused on displacement criterion of strengthened non-ductile public RC buildings in Turkey is presented. Both the nonlinear static and response history analysis were conducted. Friction dampers which are fairly modern technique and conventional RC wall implementation method were introduced to as-is building. For the simplicity and the easy of the process, 2D frame selected for investigation. Comparison of the aforementioned techniques for non-ductile public RC buildings and performances particularly by means of displacement obtained using different methods for those investigated schemes are carried out and presented in the chapter.

Seismic Assessment and Retrofitting of an Under-Designed RC Frame Through a Displacement-Based Approach

Many existing reinforced concrete buildings were designed in Southern European countries before the introduction of modern seismic codes and thus they are potentially vulnerable to earthquakes. Consequently, simplified methodologies for the seismic assessment and retrofitting of existing structures are required. In this study, a displacement based procedure using non-linear static analyses is applied to a four-storey RC frame in order to obtain an initial estimation of the overall inadequacy of the original structure as well as the extent of different retrofitting interventions. Accurate numerical models are developed to reproduce the seismic response of the RC frame in the original configuration. The effectiveness of three different retrofitting solutions countering structural deficiencies of the RC frame is examined through the displacement based approach. Non-linear dynamic analyses are performed to assess and compare the seismic response of the frame in the original and retrofitted configurations.

Selection and Scaling Time History Records for Performance-Based Design

Recent developments in performance-based analyses and the high performance of computational facilities have led to an increased trend for utilizing nonlinear time-history analysis in seismic evaluation of the performance of structures. One of the crucial issues of such analysis is the selection of appropriate acceleration time histories set that satisfy design code requirements at a specific site. In literature, there are three sources of acceleration time histories: 1) recorded accelerograms in real earthquakes scaled to match design code spectrum/uniform hazard spectra/conditional mean spectrum, 2) artificial records generated from white noise spectra to satisfy design code spectrum, and 3) synthetic records obtained from seismological models. Due to the increase of available strong ground motion database, using and scaling real recorded accelerograms is becoming one of the most contemporary research issues in this field. In this study, basic methodologies and criteria for selecting strong ground motion time histories are discussed. Design code requirements for scaling are summarized for ASCE/SEI-7-10, EC8 and Turkish Seismic Codes. Examples for scaling earthquake records to uniform hazard spectra are provided.

A Review of the Accuracy of Force- and Deformation-Based Methods in Determining the Seismic Capacity of Rehabilitated RC School Buildings

This chapter focuses on the comparison of the conventional linear force-based method with the advanced nonlinear deformation-based method that are commonly preferred to investigate the seismic performances of the existing RC school buildings. School buildings which have different structural characteristics and RC infill wall index are generated from an existing school's layout plan. During the nonlinear dynamic analysis, seven recorded earthquake motions which are scaled in accordance with the Turkish Earthquake Code are employed. Seismic performances of the school buildings against the two different earthquake hazard level are evaluated considering not only various RC infill wall indexes but also different material strengths and number of stories in terms of limit states specified in the code. In order to determine the most appropriate method related to material strength, floor level and RC infill wall index for the seismic strengthening of the existing RC school buildings, the obtained linear forced and nonlinear deformation based analyses results are compared to each other.

A Framework and Case Study for the Resilience of Infrastructures

This chapter defines resilience in different contexts comprehensively, and organizes the mathematical theory of network resilience by providing a generalization in order to create a quantitative framework for resilience characterization of an infrastructure network. At this point, a new performance index measuring delivery importance was employed for an applied purpose and an industrial example using realistic data was solved to evaluate the resilience of the entire network. It can be utilized for any type of hazard which might lead to the disruption of the system. The principles and theory in this study can also be applied to other infrastructures that are interconnected and operate as a network, such as transporting systems, electrical power, water supply and distribution systems.

Dynamic Stability and Post-Critical Processes of Slender Auto-Parametric Systems

High-rise structures exposed to a strong vertical component of an earthquake excitation are endangered by auto-parametric resonance effect. While in a sub-critical state, the vertical and horizontal response components are independent. Exceeding a certain limit causes the vertical response to lose stability and induces dominant horizontal response. This effect is presented using two mathematical models: (1) the non-linear lumped mass model; and (2) the one dimensional model with continuously distributed parameters. Analytical and numerical treatment of both leads to three different types of the response: (1) semi-trivial sub-critical state with zero horizontal response component; (2) post-critical state (auto-parametric resonance) with a periodic or attractor type chaotic character; and (3) breaking through a certain limit, the horizontal response exponentially rises and leads to a collapse. Special attention is paid to transition from a semi-trivial to post-critical state in case of time limited excitation period as it concerns the seismic processes.

Influence of the Shear-Bending Interaction on the Global Capacity of Reinforced Concrete Frames

In many seismic countries in the world (e.g. Europe, Northern USA, Japan, Turkey, etc.), the assessment of existing structures is a priority, since the majority of the building heritage was designed according to out-of-date or even non-seismic codes. The uncertainties about the nonlinear behaviour of the structures are, therefore, important and the nonlinear response should be treated directly, with a correspondingly strong increase in complexity of the assessment procedure. The assessment of regular reinforced concrete frame buildings has been performed, according to the Italian Seismic Code, Eurocode 8 and the CNR DT-212 guideline. A lumped plasticity model has been used with the aim of quantifying the differences between a fixed and a continuously updated shear span and between the use of inelastic springs located at the member ends or continuously along the beam elements, and with the purpose of considering the influence of axial-bending-shear interaction on the global capacity of the buildings.

Single-Run Adaptive Pushover Procedure for Shear Wall Structures

This chapter proposes a new single-run adaptive pushover method for the seismic assessment of shear wall structures. This method offers two main advantages: it does not require decomposing the structure in nonlinear domain and it avoids the pitfall of previous single-run adaptive pushover analyses in utilizing the modal combination in the determination of the applied loads instead of combining the response quantities induced by those loads in individual modes. After a brief review of the main adaptive pushover procedures, the proposed method is presented as well as its numerical implementation. The predictions of this method are compared to those of other recent adaptive pushover methods and as well as to the rigorous non-linear time history analysis. Analyses show the efficiency of the proposed method.

Fuzzy Logic Applications for Performance-Based Design

In this chapter, it is expressed how performance based design criteria are modeled with fuzzy logic and why it needs to be modeled with fuzzy logic. Firstly, a brief information is given about current theories and techniques such as Fuzzy Logic, Chaos, Fractal Geometry, Artificial Neural Networks; and it is mentioned about advantages of applying these techniques to the problems. Then graphical inference deduction technique is expressed by giving a summary info about Fuzzy Set Theory, membership functions, clustering, rule-based systems and defuzzification. Then the divergence of performance based design criteria is set forth by making curvature evaluations for various regulations on a column section as a structure element. Finally, it is shown in detail how to use the fuzzy set theory for solution of this disharmony by using the clustering technique on a univariate sample first and then on a multivariate sample.