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CONTENTS
Volume 8, Number 1, January 2015
 

Abstract
A simple method of assessing the risk of overturning of precast reinforced concrete columns is presented in this paper. The displacement-based methodology introduced herein is distinguished from conventional force-based codified methods of aseismic design of structures. As evidenced by results from field tests precast reinforced concrete columns can be displaced to a generous limit without sustaining damage and then fully recover from most of the displacement afterwards. Realistic predictions of the displacement demand of such (rocking) system in conjunction with the displacement capacity estimates enable fragility curves for overturning to be constructed. The interesting observation from the developed fragility curves is that the probability of failure of the precast soft-storey column decreases with increasing size of the column importantly illustrating the \"size effect\" phenomenon.

Key Words
rocking; risk of overturning; shake table; fragility curves; risk of failure

Address
Bidur Kafle, Nelson T.K. Lam, Elisa Lumantarna: Department of Infrastructure Engineering, University of Melbourne, Parkville 3010, Australia

Emad F. Gad and John L. Wilson: Faculty of Engineering and Industrial Sciences, Swinburne University of Technology,
Hawthorne 3122, Australia

Abstract
This study compares the seismic performances of two reinforced concrete frame specimens tested by the pseudo-dynamic procedure. The pair of 3-storey, 3-bay frames specimens are constructed with typical characteristics of older construction which is lacking seismic design. One of the specimens is a bare frame while the other is infilled with low-strength autoclave aerated concrete (AAC) block masonry. The focus of this study is to investigate the influence of low strength masonry infill walls on the seismic response of older RC frames designed for gravity loads. It is found that the presence of weak infill walls considerably reduce deformations and damage in the upper stories while their influence at the critical ground story is not all that positive. Infill walls tend to localize damage at the critical story due to a peculiar frame-infill interaction, and impose larger internal force and deformation demands on the columns and beams bounding the infills. Therefore the general belief in earthquake engineering that infills develop a second line of defence against lateral forces in seismically deficient frames is nullified in case of low-strength infill walls in the presented experimental research.

Key Words
gravity-load design; infilled frames; low-strength infills; AAC; pseudo-dynamic testing; performance evaluation

Address
Umair A. Siddiqui, Haluk Sucuoğluand Ahmet Yakut: Department of Civil Engineering, Middle East Technical University, Ankara - Turkey

Abstract
The Emilia, May-July 2012, earthquake has dramatically highlighted the only the hazards facing the people in insufficiently secured workplaces, but also the socio-economic consequences of interruption of production activities. After the event, in order to guarantee suitable safety levels, the Italian government asked for a generalized seismic retrofit of buildingsaffected by the earthquake under consideration. Considering that Emilia is one of the most industrialized Italian region, the number of the industrial buildings to be verified could however lead to not acceptable resumption of production time. So, with the aim to speed up the recovery, were leaved out from this request the buildings which had undergone a strong enoughshaking without any damage. In practice, the earthquakes were being used as a \"test\" to evaluate the seismic structural strength. Besides, the Italian government provision specifies also the zones, within which buildings that escaped evident damage are exempt from obligatory checks, and termed exclusion zones\", shall be individuated using the data provided by the Italian National Institute of Geophysics and Volcanology in the form of so-called \"shakemaps\". Obviously, the precision of such data greatly influences the determination of the exclusions zones and so all the economic issues related to them. Starting from these considerations, the present paper describes an evaluation of the reliability of the procedure of shakemap generation with specific regard to the seismic events that struck the Emilia region on May 20 and 29, 2012.

Key Words
emilia earthquake; shakemap; exclusion zone; post-seismic assessment; regression law

Address
Franco Braga, Rosario Gigliotti and Giorgio Monti: Department of Structural Engineering and Geotechnics, University of Rome

Abstract
The Performance-based Earthquake Engineering (PBEE) concept implies the definition of multiple target performance levels of damage which are expected to be achieved (or not exceeded), when the structure is subjected to earthquake ground motion of specified intensity. These levels are associates to different return period (RP) of earthquakes and structural behaviors quantified with adopted factors or indexes of control. In this work an 8-level PBEE study is carried out, finding different curves for control index or Engineering Demand Parameters (EDP) of levels that assess the structural behavior. The results and the curves for each index of control allow to deduce the structural behavior at an a priori unspecified RP. A general methodology is proposed that takes into account a possible optimization process in the PBEE field. Finally, an application to 8-level seismic performance assessment to structure in a Spanish seismic zone permits deducing that its behavior is deficient for high seismic levels (RP > 475 years). The application of the methodology to a low-to-moderate seismic zone case proves to be a good tool of structural seismic design, applying a more sophisticated although simple PBEE formulation.

Key Words
PBEE, seismic assessment, damage index, reinforced concrete structures, non-linear analysis, low-to-moderate seismic zone

Address
Ariel Catalán: Department of Construction, University of Oviedo, Campus of Gijon, c/ Pedro Puig Adam, 33203 Gijon, Spain

Dora Foti: Department of Civil Engineering and Architecture, Polytechnic of Bari, Via Orabona 4, 70125 Bari, Italy

Abstract
Multiple tuned mass dampers (MTMDs) tuned to various frequencies have been shown to efficiently control the seismic response of structures where multiple modes are dominant. One example is irregular structures that are found more vulnerable than their symmetric counterparts. With the technology of MTMDs available, design and optimal design methodologies are required for application. Such a methodology, in the form of an analysis/redesign (A/R) scheme, has been previously presented by the authors while limiting responses of interest to allowable values, i.e., performance-based design (PBD). In this paper, the A/R procedure is modified based on formal optimality criteria, making it more cost efficient, as well as more computationally efficient. It is shown that by using the methodology presented herein, a desired performance level is successfully targeted by adding near-optimal amounts of mass at various locations and tuning the TMDs to dampen several of the structure\'s frequencies. This is done using analysis tools only.

Key Words
irregular structures; multiple tuned mass dampers; multi modal control; seismic design of tall buildings; acceleration control

Address
Yael Daniel: Department of Civil Engineering, University of Toronto, Toronto, Canada

Oren Lavan: Faculty of Civil and Environmental Engineering, Technion- Israel Institute of Technology, Haifa, Israel

Abstract
This research formulates a closed-form equation to predict a glass panel cracking failure drift for several curtain wall and storefront systems. An evaluation of the ASCE 7-10 equation for Dclear, which is the drift corresponding to glass-to-frame contact, shows that the kinematic modeling assumed for formulation of the equation is sound. The equation proposed in this paper builds on the ASCE equation and offers a revision of that equation to predict drift corresponding to cracking failure by considering glazing characteristics such as glass type, glass panel configuration, and system type. The formulation of the proposed equation and corresponding analyses with the ASCE equation is based on compiled experimental data of twenty-two different glass systems configurations tested over the past decade. A final comparative analysis between the ASCE equation and the proposed equation shows that the latter can predict the drift corresponding to glass cracking failure more accurately.

Key Words
curtain wall; drift; glass-to-frame clearance; glass failure; glass panel cracking; prediction; seismic capacity, storefront

Address
William C. O\'Brien Jr.: Architectural Engineer, Wiss, Janney, Elstner Associates, Inc.,
10 South LaSalle Street, Suite 2600, Chicago, IL 60603, USA

Ali M. Memari and M.EERI: Hankin Chair in Residential Building Construction, Department of Architectural Engineering, Department of Civil and Environmental Engineering, Penn State University, 219 Sackett Building, University Park, PA 16802, USA

Abstract
This paper investigates the soil effect on seismic behaviour of reinforced concrete (RC) buildings by using the spread plastic hinge model which includes material and geometric nonlinearity of the structural members. Therefore, typical reinforced concrete frame buildings are selected and nonlinear dynamic time history analyses and pushover analyses are performed. Three earthquake acceleration records are selected for nonlinear dynamic time history analyses. These records are adjusted to be compatible with the design spectrum defined in Turkish Seismic Code. Interstory drifts and damages of selected buildings are compared according to local soil classes. Also, capacity curves of these buildings are compared with maximum responses obtained from nonlinear dynamic time history analyses. The results show that, soil class influences the seismic behaviour of reinforced concrete buildings, significantly.

Key Words
local soil class; spread plastic hinge; interstory drift; pushover analysis; time history analysis

Address
Burak Yön and Yusuf Calay: Firat University Civil Engineering Department, Elaz

Abstract
Most damaging earthquakes come as complex sequences characterized by strong aftershocks, sometimes by foreshocks and often by multiple mainshocks. Complex earthquake sequences have enormous seismic hazard, engineering and societal implications as their impact on buildings and infrastructures may be much more severe at the end of the sequence than just after the mainshock. In this paper we examine whether historical sources can help characterizing the rare earthquake sequences of pre-instrumental times in full, including fore-, main- and aftershocks. Thanks to the its huge documentary heritage, Italy relies on one of the richest parametric earthquake catalogues worldwide. Unfortunately most current methods for assessing seismic hazard require that earthquake catalogues be declustered by removing all shocks that bear some dependency with those identified as mainshocks. We maintain that this requirement has led most modern historical seismologists to focus mainly on mainshocks rather than also on the fore- and aftershocks. To shed light onto major earthquake sequences of the past, rather than onto individual mainshocks, we investigated 10 damaging earthquake sequences (Mw 4.7-7.0) that hit the L\'quila area and central Abruzzo from the 14th to the 20th century. We find that most of the results of historical research are important for modern seismology, yet their rendering by the current parametric catalogues causes most information to be lost or not easily transferred to the potential users. For this reason we advocate a change in current strategies and the creation of a more flexible standard for storing and using all the information made available by historical seismology.

Key Words
earthquake sequences, historical earthquake catalogues, L\'Aquila seismicity, Abruzzo seismicity, historical foreshocks, historical aftershocks

Address
Emanuela Guidoboni: Academia Europaea

Gianluca Valensise: Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy

Abstract
This study investigates the impact of the earthquake incident angle on the structural demand and the influence of ground motion selection and scaling methods on seismic directionality effects. The structural demand produced by Non-Linear Time-History Analyses (NLTHA) varies with the seismic input incidence angle. The seismic directionality effects are evaluated by subjecting four three-dimensional reinforced concrete structures to different scaled and un-scaled records oriented along nine incidence angles, whose values range between 0 and 180 degrees, with an increment of 22.5 degrees. The results show that NLTHAs performed applying the ground motion records along the principal axes underestimate the structural demand prediction, especially when plan-irregular structures are analyzed. The ground motion records generate the highest demand when applied along the lowest strength structural direction and a high energy content of the records increases the structural demand corresponding to this direction. The seismic directionality impact on structural demand is particularly important for irregular buildings subjected to un-scaled accelerograms. However, the orientation effects are much lower if spectrum-compatible combinations of scaled records are used. In both cases, irregular structures should be analyzed first with pushover analyses in order to identify the weaker structural directions and then with NLTHAs for different incidence angles.

Key Words
directionality; ground motion; nonlinear time history analysis; angle of incidence; reinforced concrete structures; ground motion scaling

Address
Cristina Cantagallo, Guido Camataa and Enrico Spaconeb: Engineering and Geology Department, University

Abstract
A new method for designing moment resisting concrete frames failing in a global mode is presented in this paper. Starting from the analysis of the typical collapse mechanisms of frames subjected to horizontal forces, the method is based on the application of the kinematic theorem of plastic collapse. The beam section properties are assumed to be known quantities, because they are designed to resist vertical loads. As a consequence, the unknowns of the design problem are the column sections. They are determined by means of design conditions expressing that the kinematically admissible multiplier of the horizontal forces corresponding to the global mechanism has to be the smallest among all kinematically admissible multipliers. In addition, the proposed design method includes the influence of second-order effects. In particular, second-order effects can play an important role in the seismic design and can be accounted for by means of the mechanism equilibrium curves of the analysed collapse mechanism. The practical application of the proposed methodology is herein presented with reference to the design of a multi-storey frame whose pattern of yielding is validated by means of push-over analysis.

Key Words
global mechanism; concrete moment resisting frames; plastic collapse theory

Address
Rosario Montuoriand Roberta Muscati: Department of Civil Engineering, University of Salerno – Italy

Abstract
This paper presents a state-of-the-art review of the nonlinear modelling techniques available today for describing the structural behaviour of masonry infills and their interaction with frame structures subjected to in-plane loads. Following brief overviews on the behaviour of masonry-infilled frames and on the results of salient experimental tests, three modelling approaches are discussed in more detail: the micro, the meso and the macro approaches. The first model considers each of the infilled frame elements as separate: brick units, mortar, concrete and steel reinforcement; while the second approach treats the masonry infill as a continuum. The paper focuses on the third approach, which combines frame elements for the beams and columns with one or more equivalent struts for the infill panel. Due to its relative simplicity and computational speed, the macro model technique is more widely used today, though not all proposed models capture the main effects of the frame-infill interaction.

Key Words
frame structures; masonry infill; equivalent strut model; finite element; nonlinear analyses

Address
Tarque Nicola: Division of Civil Engineering, Pontificia Universidad Católica del Perú, Av. Universitaria 1801, Lima 32, Peru

Candido Leandro: Department of Engineering for Innovation, University of Salento, Piazza Trancedi 7, 73100 Lecce, Italy

Camata Guido and Spacone Enrico: Department of Engineering and Geology, University

Abstract
The current investigation has been conducted to examine the effect of gravity loads on the seismic responses of the doubly asymmetric, three-dimensional structures comprising walls and frames. The proposed model includes the P- effects induced by the building weight. Based on the variational approach, a 3D finite element with two nodes and six DOF per node including P- effects is formulated. Dynamic and static governing equations are derived for dynamic and buckling analyzes of buildings braced by wall-frame systems. The influences of P- effects and height of the building on tip displacements under Hachinohe earthquake record are investigated through many structural examples.

Key Words
seismic analysis; asymmetric multi-storey buildings; finite element method; P-

Address
Abdesselem Hichem Belhadj and Sid Ahmed Meftah: Laboratoire des Structures et Matériaux Avancés dans le Génie Civil et Travaux Publics, Université de Djellali Liabes, BP 89 cité Ben M

Abstract
The objective of this paper is to investigate the validity of transmitting boundaries in dynamic analysis of soil-structure interaction problems. As a case study, the proposed Baghdad metro line is considered. The information about the dimensions and the material properties of the concrete tunnel and surrounding soil were obtained from a previous study. A parametric study is carried out to investigate the effect of several parameters including the peak value of the horizontal component of earthquake displacement records and the frequency of the dynamic load. The computer program (Mod-MIXDYN) is used for the analysis. The numerical results are analyzed for three conditions; finite boundaries (traditional boundaries), infinite boundaries modelled by infinite elements (5-node mapped infinite element) presented by Selvadurai and Karpurapu ,1988), and infinite boundaries modelled by dashpot elements (viscous boundaries). It was found that the transmitting boundary absorbs most of the incident energy. The distinct reflections observed for the \"fixed boundaries\" disappear by using \"transmitted boundaries\". This is true for both cases of using viscous boundaries or mapped infinite elements. The type and location of the dynamic load represent two controlling factors in deciding the importance of using infinite boundaries. It was found that the results present significant differences when earthquake is applied as a base motion or a pressure load is applied at the surface ground. The peak value of the vertical displacement at nodes A, B, E and F (located at the tunnel

Key Words
dynamic; soil-structure interaction; infinite element; tunnel; earthquake

Address
D K Jainand M S Hora: Department of Civil Engineering, Maulana Azad National Institute of Technology, Bhopal, India


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