Modern Earthquake Engineering Research Articles

Seismic assessment of free‐standing artifacts: Full‐scale tests on large shake table

AbstractRecent severe earthquakes highlighted the high vulnerability of artistic assets. Thus, the seismic assessment and formulation of preservation strategies of artifacts are key challenges of modern earthquake engineering, which require theoretical and experimental investigations. The present paper discusses the outcomes from large scale shake table tests carried out on full‐scale free‐standing artifacts. The study is also aimed at evaluating the reliability of existing simplified formulations to predict the rocking motion activation. Emphasis is on prototypes of marble busts with solid and hollow pedestals with different geometries. Comprehensive tests were performed within “Seismic Resilience of Museum Contents” (SEREME) project, which was recently funded by H2020 Framework Programme – Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe (SERA). Uniaxial and biaxial earthquake natural records with different amplitudes and frequency contents were considered to assess the rocking motion of the sample specimens. Response parameters such as uplift, horizontal and vertical accelerations, angular velocity were measured to assess the rocking response of the sample freestanding busts and pedestals. Coefficients of amplification (CAF) of acceleration were also computed. The value of CAF showed that for solid pedestals they were not significantly influenced by peak ground acceleration (PGA) and earthquake type. Conversely, hollow pedestals, which were characterized by larger values of CAF than solid counterparts, ranging between 1 and 7, were affected by PGA and earthquake characteristics. Finally, the outcomes of the presented shake table tests showed that uplifts and angular velocity are effective measures for assessing rocking occurrence of tested artifacts.

Seismic behavior of exterior RC beam-column joints without code-specified ties in the joint core

Beam-column joint design for reinforced concrete (RC) buildings is a critical issue for modern earthquake engineering, because for these structural elements, the current codes provide several geometrical constraints and reinforcement provisions, which may be very complex to implement during the construction phase. To investigate how a construction error might influence the joint behavior, two identical full-scale exterior beam-column joints specimens are built, according to Italian Building Code specifications for the high ductility class, but without the required horizontal ties inside the joint panel. This construction error could be plausible because, according to the design drawings, the panel was very crowded with reinforcement bars and the concrete casting and compaction was objectively difficult. The performance of the joints is tested under cyclic loads simulating seismic actions. Although the joints are designed for high ductility class, a 50% reduction of the horizontal reinforcement in the joint core, and 25% in the critical regions, led the specimens to shear failure, with crushing of the concrete in the joint core. A discussion of the failure mechanism is presented, in which shear strength obtained from the tests is compared to shear strengths calculated using the expressions provided for exterior joints by Eurocode 8, the ACI Code and the formula proposed by Pauletta et al.

Resilient seismic design of steel frames with hysteretic fuses in a code-oriented format

Modern earthquake engineering has to evolve toward resilience-based design, where structures are expected to survive major earthquakes with reduced or null damage that could be easily reparable in a reasonable time. With such a design strategy, three important goals are warranted: a) life safety of people, b) preserve of building property within a reasonable investment to repair light damage, and c) minimize economic losses because of building's usage interruption. One way to achieve such goal is by using hysteretic energy dissipation devices as structural fuses. Although any global strategy could be used for the successful resilient design of buildings with structural fuses, the authors have work extensively to define global design parameters in order to introduce resilient-based design in the current force-oriented format of most seismic building codes worldwide. Then, global design parameters obtained from very comprehensive parametric studies for special moment-resisting steel frames with hysteretic fuses are presented and discussed. Also, it is shown that the proposed code-oriented methodology is successful to achieve resilient seismic design when subjected to strong earthquake records that may even surpass those considered in their design spectra.

Discrete-analytical nonlinear analysis with improved computation accuracy for steel frame lateral response evaluation

The structural performance evaluation under the monotonic increase of a lateral load due the whole loading process in modern earthquake engineering practice can be performed with the help of different methods and software and can be dramatically represented by «Base reaction – Roof displacement» relationship, which is also known as capacity curve. This kind of relationship is used by nonlinear static Pushover-analysis for seismic performance evaluation of buildings considering any possible damage, which is acceptable by serviceability requirements of a building. However, there are many problems arising due to physically nonlinear analysis of structure, primarily associated with features of the employing finite elements analysis software. Main problems are rather long analysis time among the necessity of high performance computing, or shortcomings of nonlinear analysis methods inherent to the program used. One of the most important shortcomings of structural analysis software is the necessity of single-handed assignment of a failure mechanism for the structure by nonlinear hinges formation zones emplacement to elements of analytical model. This circumstance may lead to results substantially different from reality. These problems can be resolved with the aid of discrete-analytical methods.

Identification of the structural model and analysis of the global seismic behaviour of a RC damaged building

The study of the structural behaviour of damaged RC buildings during ground motion is a fundamental topic in the modern earthquake engineering. Many studies have been carried out in order to better understand the real evolution of the damage in RC buildings during a seismic event. In this work, a damaged RC building has been intensively investigated in terms of materials property and stiffness evolution in order to interpreting the structural and nonstructural surveyed damage. The peculiarity of this building is its damage sequence during the 2002 Molise earthquake. In fact, the town of Bonefro suffered moderate damage (MCS intensity VII), with the exception of the investigated reinforced concrete building. The October 31, 2002 event (M=5.4) caused some structural damage to this building. The second event (M=5.3), on November 1, 2002, increased substantially the damage level (grade 4 according to the 1998 European Macroseismic Scale). It occurred just while, due to fortuitous circumstances, a 5min. seismic velocimetric recording was being taken. The working group has performed some frequency analyses based on the recording. Several non linear models have been defined to understand the damage evolution of the building and the local and global damage patterns through for static analyses. Finally, linear and non linear models have been developed with the main goal of identifying the characteristics of a reliable undamaged structural model.

Far-Source Long-Period Displacement Response Spectra in the Po and Venetian Plains (Italy) from 3D Wavefield Simulations

Abstract Design-elastic displacement spectra for seismic codes and zoning studies of seismic hazard for long-period structures are becoming of utmost importance in modern earthquake engineering. The increase of displacement-based design approaches, together with the availability of good-quality digital strong-motion data, allow the creation of reliable spectral shapes for seismic design of up to 10 s. Nevertheless, to characterize the site amplification effects during large levels of shaking, additional studies are needed, especially in deep sedimentary basins and plains that can be strongly excited by large amplitude long-period waves. Data within deep basins is rare because accelerometric seismic networks are normally deployed on rock or stiff soil, and modeling of waveforms is hence necessary for bridging this gap. Focusing on the numerical modeling of the 3D wavefield in 1D flat layered and 3D structures in the Po and Venetian plains (northern Italy) and on earthquakes with magnitudes M 6.6 and hypocentral distances greater than 50 km, in this study we (1) estimate the displacement response spectra (DRS) from 1 to 10 s in the Po and Venetian plains, (2) compare the DRS from numerical simulations using flat layered and heterogeneous 3D models against the currently available uniform-hazard DRS for Italy, and (3) evaluate the influence of deep sediments on DRS shape and thus on seismic codes. Finally, 1D- and 3D-simulated DRS are compared with DRS obtained from recordings in the Kanto basin where similar long-period displacement is observed.

Discussion and Method on Performance Based Seismic Design for Concrete-Filled Steel Tubular Structures

The theory of performance-based seismic design (PBSD) is the key issue for the modern earthquake engineering research. With comparison of the traditional prescriptive seismic design code based on the bearing capacity design, the PBSD method presents the specific performance object for the buildings. On the base of the background and development of the PBSD about reinforced concrete (RC) structures, some researches and design approaches of PBSD were proposed for the concrete-filled steel tubular (CFST) structures based on the research results on PBSD of RC structures and the mechanical behavior of CFST structures. Some theory analysis was performed to investigate the PBSD performance of CFST structures. This is referred to further study on PBSD for CFST structures.

Earthquakes that have initiated the development of earthquake engineering

The recent 75th anniversary of the 1931 Hawke’s Bay Earthquake reminds us that a particular earthquake can have a great effect on the development of engineering methods to contend with this natural hazard. Factors other than the occurrence of a single earthquake are also present before and after such a historically important event, and there are examples of countries that began on the path toward modern earthquake engineering in the absence of any particular earthquake playing an important causal role. An earthquake that was large in seismological (e.g. magnitude) or engineering (e.g. destructiveness) measures may have had little effect on engineering tools developed to contend with the earthquake problem. The history of earthquake engineering is not merely a set of events rigidly tied to a chronology of major earthquakes. Nonetheless, some significant earthquakes have been step function events on the graph of long-term progress in earthquake engineering. Only earthquakes that bring together several prerequisites have had such historic effects, creating in a country a beachhead for earthquake engineering that persisted in the following decades. In this brief historical review, the following seminal earthquakes are discussed: 1906 Northern California, United States; 1908 Reggio-Messina, Italy; 1923 Kanto, Japan; 1931 Mach and 1935 Quetta, India-Pakistan; 1931 Hawke’s Bay, New Zealand.

A very brief history of earthquake engineering with emphasis on developments in and from the British Isles

One of the founders of modern earthquake engineering, George Housner, often states that it is too early to write a historical review of the development of this interesting and inter-disciplinary topic. This is indeed true, but without minor contributions along the line, the prospects of writing such a review diminish with time. The endeavour is certainly premature. Notwithstanding, the paper serves some useful purpose. It serves to remind engineers from Europe generally, and the British Isles specifically, that they are descendants of pioneers in earthquake engineering, a fact not widely known nor sufficiently publicised. The names of Robert Mallet and John Milne, alongside the early Japanese pioneers Sekiya, Suyehiro and Omori, feature very strongly around the late 1800s early 1900s. The Italian engineers Palmieri, Panetti and Danusso also made essential contributions at a critical time. For reasons that still prevail today, once an idea is implanted in the United States of America, it takes root so vigorously that its flourishing is attributed solely to the fertility of the medium. This is not necessarily disputable, but due recognition of the originator would perhaps encourage further cross-fertilisation. The fact still remains that Nathan Newmark, Bill Hall, Bruce Bolt and George Housner all made their mark from a US platform. But, since earthquakes know neither national nor technical-discipline boundaries, seismic risk mitigation efforts should also abandon these boundaries and deploy all means and efforts to protect communities threatened by earthquake risk.

Damage and intensities in the magnitude 7.8 1929 Murchison, New Zealand, earthquake

This paper is the result of a study of the Ms= 7.8 Murchison earthquake which occurred in the South Island of New Zealand, on 16(UT) June 1929, a few years prior to the introduction of the first earthquake loadings code in New Zealand. It gives the first description of the damage to buildings in this event in modern earthquake engineering terms, and presents the first Modified Mercalli (MM) intensity map for the event determined from the original felt information. Some definitions of "well-built" pre-code buildings are proposed: these should help in dealing with safety and conservation issues raised when considering the future of such "earthquake risk" buildings. No evidence was found for MM10 intensities, although ground shaking of this strength probably occurred in the unpopulated mountainous countryside close to the fault rupture. Recommendations for improving the criteria for determining MM intensity are made in respect of (1) pre-code buildings and (2) seismically-induced landslides.

Brief review of modern earthquake engineering

This review is a brief survey of the present status of Earthquake Engineering. It contains information on earthquake hazards, main Earthquake Engineering problems, safety of structures under the action of earthquakes, Earthquake Engineering research and education, and international collaboration. The review is prepared in accordance with a decision by the International Association for Bridge and Structural Engineering to set up a working group for dealing with “Information on Earthquake Engineering”. The decision to create this working group was supported by the "Comite de Liaison", which co-ordinates the activity of several international associations dealing with Structural Engineering, such as the International Association for Bridge and Structural Engineering, the European Committee for Concrete, the International Federation for Prestressing, the International Council for Building Research Studies and Documentation, the European Convention of the Associations for Steel Construction, and the International Association for Shell Structures.