Earthquake Resistant Buildings Research Articles

Investigation of progressive collapse resistance and inelastic response for an earthquake-resistant RC building subjected to column failure

Following the linear static analysis procedure recommended by the US General Service Administration (GSA), the potential of an earthquake-resistant RC building for progressive collapse is evaluated in this study. Nonlinear static and nonlinear dynamic analyses are conducted to estimate the progressive collapse resistance of the building subjected to column failure. Under an approximate deflection demand, different collapse resistances are obtained. It indicates that different criteria for estimating the collapse resistance may be adopted for these two nonlinear analysis methods. The nonlinear static approach leads to a conservative estimation for the collapse resistance if “2.0” is used as the dynamic amplification factor (DAF). As the column-removed building is loaded into a significantly yielding phase, different assessed results are obtained by the linear static method and the nonlinear acceptance criterion suggested by the GSA guidelines. A DAF considering the inelastic dynamic effect may be needed in the GSA linear procedure. The capacity curve constructed from the nonlinear static analysis is shown to be capable of predicting the progressive collapse resistance and the DAF of a column-removed RC building.

Earthquake-Resistant Building : Buckling-Restrained Braced Truss-Girder Moment Frames (proposed)

Abstract⎯This paper evaluates the inelastic behaviors of four Buckling-Restrained Braces (BRB) and two full scale Buckling-Restrained Braced Truss-girder Moment Frames (BRBTMF) by analytical and experimental means. The BRB section is strip plate core cased with rectangular hollow section, thus resulting in identical axial strengths of compression and tension. The BRBTMF proposed in this paper is the modification of The Special Truss Moment Frames (STMF) by replacing the X-bracing with the BRB. The conclusion of analitical studies is that frames proposed have better inelastic behavior than the other ductile frames. From the experimental analysis the BRBTMF have hysteretic curves in the 3% drift ratio to cyclic loading and result the cumulative ductility factor which has met the requirements of the histeretic system structure.

A METHOD TO IMPROVE THE DISTRIBUTION OF STORY DRIFT ANGLE RESPONSES IN MULTI-STORY BUILDING WITH HYSTERETIC DAMPERES UNDER EARTHQUAKE EXCITATIONS

As the performance-based design is coming to be widely used for earthquake-resistant buildings, it would be more necessary to evaluate the building performances through earthquake dynamic responses. Hysteretic dampers are popularly installed in high-rise buildings in ordert to control the earthquake responses. In this paper, we propose a simple method to optimize hysteretic-damper strengths so as that the story-drift responses are distributed with the targeted value equally for all storys of a building under earthquake excitations. The applicability of the method was demonstrated by a numerical calculation of various frame models through a nonlinear frame analysis.

Can Buildings Be Made Earthquake-Safe?

Earthquake resistant building design has improved greatly since the 1906 San Francisco temblor. However, low-tech solutions for structures in the developing world are sorely needed.

Commonly encountered seismic design faults due to the architectural design of residential buildings in Turkey

The 17 August 1999 and 12 November 1999 earthquakes in Western Anatolia provided undesirable field evidence that most of the low story residential reinforced concrete buildings have very poor earthquake resistance. Architectural design faults negatively affect the structural behavior of buildings. In Turkey, earthquake-resistant design is considered to be exclusively within the field of responsibility of structural engineers. As a result, architects and especially students of architecture are not well informed about the effect of their design decisions on the seismic performance of the buildings. Structural damages in collapsed buildings demonstrate that most of the design faults that lead to destruction of buildings are due to architectural decisions. This paper intends to present the concept of earthquake-resistant design in a comprehensible format for the architects and builders, therefore aims to contribute to the efforts of creating a better awareness of earthquake resistant building design.

A Critical Analysis of Earthquake-Resistant Architectural Provisions

Modern science has enabled experts in building process such as engineers and architects to prepare and organize earthquake provisions through building codes. However, having a modern earthquake code does not guarantee earthquake resistant buildings. The clarity of the codes, especially for architects, and code enforcement are other important factors that should be satisfied. Many scholars and practicing architects may think that ensuring the implementation of earthquake-resistant designs is primarily the responsibility of the structural engineer, but in reality it is not. Earthquake-resistant design is closely related to the architectural configuration of a building. In many instances, certain earthquake resistant design requirements are neglected both in architectural education and in practice with the thought that the structural engineer can integrate earthquake provisions in the design later, after the architectural design is completed. This paper presents a critical analysis of earthquake provisions related to architectural design, both in building codes and architectural education especially for reinforced concrete buildings in the case of Turkey.

Trends in Global Urban Earthquake Risk: A Call to the International Earth Science and Earthquake Engineering Communities

There is a new “seismic gap” that we—members of the international Earth science and earthquake engineering communities, including members of the Seismological Society of America (SSA) and the Earthquake Engineering Research Institute (EERI)—need to know about: the large and growing gap between the seismic risk of rich countries and that of poor countries. We need to know about it because it threatens rich and poor countries alike, because what is being done about it is not enough, and because we are in a unique position to narrow it. In the next 20 years,... the urban population of developing countries will increase... by 2 billion people... Urban earthquake risk in poor countries is large and rapidly growing. Fifty years ago, the population of the world's largest earthquake-threatened cities was equally divided between rich and poor countries. Today, there are five times as many people in poor as in rich earthquake-threatened cities. Fifty years ago, the earthquake resistance of buildings in rich countries was better than that of buildings in poor countries, and since then it has steadily improved, while that in poor countries has steadily worsened. Data of the U.S. Office of Foreign Disaster Assistance indicate that the average number of deaths resulting from fatal earthquakes in rich countries decreased by about a factor of 10 between the first half of the 20th century and the last half. This improvement in seismic safety is presumably the result of, among other things, better building and land-use codes and better enforcement of those codes. By contrast, there are indications that earthquakes in developing countries will increase their lethality in the future. At last year's SSA conference, Roger Bilham described how we should expect in this century an earthquake that will kill as many as one million people in a developing country. We can …

Urban Earthquake Fatalities: A Safer World, or Worse to Come?

The global fatality count from earthquakes continues to rise. This has occurred despite the adoption of earthquake-resistant building codes in most countries where damaging earthquakes have historically caused loss of life. In the past five centuries the global death toll from earthquakes has averaged 100,000/year, a rate that is dominated by large infrequent disasters, mostly in developing nations. Though an increased fatality rate might be expected from the steady increase in global population (Bilham, 1988), recent urban growth has been accompanied by a decline in the fatality rate as expressed as a percentage of instantaneous population. It is tempting to attribute this observation to the application of earthquake-resistant construction code in new city construction. A more sinister interpretation, however, is that the apparent decline in risk is caused by the short exposure time (50 years) of the world's recently increased population to earthquakes with recurrence intervals of the order of centuries. Future extreme earthquake disasters in some of the world's megacities may arrest, or reverse, the current trend. Figure 1. (Left) City populations between 1960 and 2000 grew on average by a factor of 2.55. The mean urban growth rate in developing nations (filled bars) is twice this, largely in cities with present populations of less than 1 million. (Right) Global urban population grows mostly in cities in developing nations. Global populations doubled between 1900 and 1960 and doubled again between 1960 and 2000 (United Nations, 2002). Most of this population growth has occurred in the cities of the developing nations in cities with populations 1 million or less. Although less than 4% (≈400 million) of the world's population live in megacities with 10 million or more inhabitants, half of these are located in earthquake-vulnerable locations. Since 1960, one hundred cities with populations exceeding 1 million have increased their populations by an …

鉄筋コンクリート造建物の耐震性能評価指針 (案) の概要

日本建築学会は2004年1月に「鉄筋コンクリート造建物の耐震性能評価指針 (案) ・同解説」を公表した。この指針では, すでに設計が完了した建物が保有する耐震性能を評価するための指標とともに, 具体的な評価手法が示されている。保有性能指標は構造物が限界状態に達する地震動の強さ (レベル) で表示するが, 基準地震動に対する強さの比で確定的に表現する方法を基本にして, 特定の地域において発生する地震動の超過確率として評価する方法も示されている。限界状態は使用性, 修復性, 安全性に関して定義されるが, 部材の残留損傷状態に基づいて限界状態に対応する構造物の最大塑性変形 (限界変形) および地震動による応答変形を実用的に評価する手法が示されている。本稿ではこの指針 (案) の考え方や背景を紹介する。

Building collapse and human deaths resulting from the Chi-Chi Earthquake in Taiwan, September 1999.

In this study, the authors attempted to determine factors associated with earthquake deaths in the great Chi-Chi Earthquake that occurred on September 21, 1999, in Taiwan. An isoseismal map was used to identify life-threatening hazards. The vertical peak ground acceleration of ground motion intensity was deemed the most appropriate index for the evaluation of building collapse and mortality. Mortality increased with the increase in earthquake intensity, and building collapse, approaching the epicenter. The greatest number of collapsed buildings and human deaths occurred between the Chelungpu Fault and the Shuantun Fault. Individuals 65 yr of age and older were the most vulnerable to the impact. The authors' findings suggest that improvements in earthquake-resistant building design and construction, as well as improved medical rescue for the elderly, could reduce the level of exposure to earthquake hazards.

STUDY OF SOCIAL-TECHNOLOGY FOR IMPROVING EARTHQUAKE-RESISTANCY OF EXISTING PRE CODE-REVISION STRUCTURES

We have conducted a research on new institutional measures to promote the examination and improvement of earthquake-resistancy of existing nonconforming houses. The measures include accountability system for earthquake -resistancy of used houses at the time of sale/rental transactions; life/nonlife insurance premium discount program for highly earthquake-resistant buildings; price assessment program for used house earthquake-resistancy; and mitigation,and restriction of use of earthquake-vulnerable buildings. The research methods include construction of cause hypothesis system, cause investigation and effectiveness investigation through consumer awareness survey via the internet, conception of new institutional measures based on current measures, and evaluation from legal viewpoint. Language: ja

T. Paulay's Discussion of “Seismic Behavior of Dual Systems with Column Hinging”

We thank Professor Paulay for the attention he paid to our work. Our motivation to perform the work that gave rise to the paper was to show the advantages of dual systems as earthquake-resistant building structures. Among other advantages, we tried to show that in ductile frames the hinges can develop in the beams, in the columns, or both, due to the fact that the walls prevent the development of the soft story mechanism. We believe this conclusion helps the compatibility of architectural requirements with the ductile design of reinforced concrete frames, rendering dual systems more attractive for earthquake resistant design. Since Professor Paulay shares our views on the advantages of dual systems, we are left essentially with the possibility of commenting on his findings kindly added to the discussion. In our view, those comments include simple and revolutionary ideas that offer excellent opportunities to design safer structures at reduced costs. The best example is expressed in Point 3: ‘‘yield deformations of components are largely independent of their nominal strength,’’ leading to much greater choice in the assignment of strength between walls and frames. We read the relevant reference (Paulay 2002) and we fully agree with this view. We also agree with the concepts expressed in Points 1, 2, and 5. We can only add a few comments: • Point 3—It may be reasonable to establish certain limits to the distribution of strength between walls and frames. These should be related to the need to avoid brittle behavior of elements of the structure, particularly the walls. This could eventually be induced by assigning to the frames a fraction of the inertia forces too small. If the frames would possess some excess strength in what regards the design for other load combinations, the shear ratio (l = M/VL) at the base of the wall could be overestimated. This would derive from the fact that the frames would tend to lower down the resultant of the inertia forces applied on the wall during the response to an earthquake. This would lead to the underestimation of the design forces at the base of the wall associated with the development of the flexural capacity. This point is implicitly addressed in the conclusions of the above-mentioned reference where the redistribution of a ‘‘fraction of the required seismic strength’’ is referred to. • Point 5—Lower periods, as would result from stiffness estimates based on elastic gross or cracked concrete sections, would generally lead to the overestimation of spectral accelerations and inertia forces. Even though less realistic, these would

Proportioning of Earthquake-Resistant RC Building Structures

A simple and efficient method is presented for proportioning of regular, moderate-rise reinforced concrete building structures. The method differs from conventional procedures in that member sizes are selected based on the demand defined by the displacement spectrum and criteria specified in relation to drift response. The maximum mean drift, or average distortion over the total height, is limited to reduce the expected damage to the structure. A series of analytical reinforced concrete frames are proportioned and tested using a suite of ground motions. Results of the analyses indicated that maximum displacement responses of the proportional frames were within the specified drift limit when a maximum-allowable period criterion was satisfied.

Seismic performance of RC frames designed for three different ductility levels

The concept of “making structures ductile” has prevailed in modern earthquake-resistant building design. In this context, questions remain regarding the selection of adequate ductility levels and the corresponding seismic force reduction factor q for a specific class of structures, whereas the detailing requirements to ensure the desired ductility continue to be refined. In the current investigation, three simple frames were designed for different ductility levels according to EC8 [Eurocode 8: Design provisions for earthquake resistance of structures. CEN (European Commission for Standardisation)/TC250/SC8, 1994] and their actual performance when subjected to earthquake simulation tests are observed and compared. Results indicate that under the “ductility for seismic force reduction” trade-off scheme, the frame designed for high ductility (thus large q factor) tends to attract more extensive damage due to large yield excursion, resulting in certain performance reduction. Insufficient confinement could lead to degrade hysteretic behaviour in a rather sensitive manner. Satisfactory performance was observed in the frame designed for medium ductility where both the seismic force reduction factor and the overall ductility were in the order of 3–4. In general, the overall and local ductility demands and the q-factors were observed to correlate in a rather predictable manner.

Seismic Performance of Direct Hung Suspended Ceiling Systems

Current seismic design philosophies require an earthquake-resistant building capable of resisting strong motion for structures and nonstructural elements. In response to the need to understand the seismic behavior of nonstructural elements, this paper presents the study on the vibration behavior and seismic capacity of direct hung suspended (DHS) ceiling systems. Modal analysis to investigate the eigen properties of the DHS ceilings was performed. Natural frequencies and mode shapes were identified using analytical models and verified by modal experiments. Different ceiling configurations were tested to understand their ultimate strength under incremental shock spectrum excitation. It was discovered that the 45° sway wires method prescribed by ceiling and Interior System Contractors, does not increase the seismic capacity of the entire system. Based on recent field observations of DHS ceiling earthquake damage in Taiwan, it was found that pop rivets at the molding would increase the seismic capacity of the DHS systems. It was also discovered that a constraint transverse to the excitation direction would greatly influence the behavior of a DHS system.

Earthquake resistant building design codes and safety standards: The California experience

Seismologists and earthquake engineers have sought to understand and predict earthquakes and to develop better building designs to withstand them for well over a century. In the United States, the 1906 San Francisco earthquake provided the first real impetus for establishing building design codes and safety standards. Subsequent major California earthquakes in Santa Barbara (1925), Long Beach (1933), San Fernando (1971), Loma Prieta (1989), and Northridge (1994) each led to additional seismological understanding and engineering response in the form of enhanced building design codes. Nonetheless, the process to incorporate good seismic design and mitigation efforts has been slow, and by no means failsafe, especially in the Eastern U.S. where much of the building stock predates more recent design codes, and hence where a major earthquake could collapse large numbers of buildings. Even in the absence of catastrophe, it is still important to guard against a false sense of security.

Zonation of metropolitan France for the application of earthquake-resistant building regulations to critical facilities Part 2: Seismic zonation

The seismotectonic zonation of Metropolitan France(part 1) and the derived seismic zonation (part 2)were carried out in order to facilitate andstandardise the application of earthquake-resistantbuilding regulations to critical facilities forreasons of environmental protection (Decree No.91-461, Ministerial Order dated 10 May 1993).According to current French legislation, adeterministic approach was adopted for the executionof these two successive zonations.The seismic zonation is based on a 2.5 km square gridcovering the whole of Metropolitan France, in whicheach cell is defined by the maximal macroseismicintensities that could be induced by a `MaximumHistorically Credible Earthquake' (MHCE) and a‘Seismic Safety Evaluation Earthquake’ (SSEE) innearby seismotectonic units. The values of theseintensities were calculated by displacing thereference earthquakes of the seismotectonic zonationto the most penalising position relative to the celland using attenuation laws deduced from the isoseismalcurves specific to each earthquake taken as reference.The zonations obtained for the MHCE and SSEEintensities should thus be considered as the physicalzonations of France for the application ofearthquake-resistant building regulations to criticalfacilities. They are applicable to all criticalfacilities and provide a consistent approach forassessing the levels of seismic aggression to be used(in MSK intensity) at any site in Metropolitan France,as well as the elementary parameters for calculatingthe response spectra usable in the design orverification of structures.

Seismic Response Modification Factors

The response modification factor plays a key role in the seismic design of new buildings in the United States. To date, the values assigned to this factor are based on engineering judgment and have little sound technical basis. Any improvement in the reliability of modern earthquake-resistant buildings in the United States will require the systematic evaluation of the building response characteristics that most affect the values assigned to the factor. To this end, a draft formulation that represents the response modification factor as the product of factors related to reserve strength, ductility, and redundancy is presented in the paper. Pertinent data from various analytical and experimental studies on reserve strength and ductility are also presented.

The Japanese Building Standard Law and a series of steels for earthquake-resistant building structures

This contribution refers to the Building Standard Law in Japan and by focusing especially on the part which is related to seismic forces, shows how to protect humans and property (in Japan) from earthquake disasters. In 1981, the Law was amended to introduce plastic design into architecture. In order to enhance the ability of the new seismic proof structural design method, a new series of steels was developed and manufactured in 1994. Material damage induced by repeated earthquakes is investigated in this paper. The newly produced pre-damaged SN490B steel (one of the new steels) is tested and evaluated under dynamic tension. The pre-damage is introduced by pre-fatiguing or pre-straining. Compared with SM490A steel (a conventional steel), the remaining mechanical properties of the SN490B steel resemble those of SM490A even under dynamic tension. However, once plastic deformation has developed in the SN490B steel, it loses the capability of accepting large deformation when used in structural members. Tests suggested that, once the structural building has suffered plastic deformation, the building components will not comply with the new seismic proof design method. In case of such a condition, the components fabricated from these new steels should be either reinforced, replaced or rebuilt.

Vibration-Isolation Retrofit for the National Museum of Western Art, Tokyo

The National Museum of Western Art in Tokyo, designed by Le Corbusier, is highly valued, not least because it is the only building by the renowned architect in East Asia. The museum, opened in 1959, is currently being completely renovated and expanded, and the main building has also been reinforced against earthquakes as part of a program of disaster-reduction measures. Comprehensive studies of earthquake-resistant reinforcement, building preservation and effective building utilization were carried out for this project.