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The fracture of transverse hoop reinforcement can lead to the collapse of a reinforced concrete column, as has been observed in concrete bridges and buildings attacked by severe earthquakes as well as in laboratory tests. To predict the longitudinal concrete strain at the stage of first hoop fracture a theoretical method based on considerations of strain energy referred to as "Energy Balance Theory" has been proposed by Mander et al. This paper reviews the "Energy Balance Theory" and then proposes several modifications for this theory based on a failure model of a reinforced concrete column subject to axial compression. These modifications take into account significant energy factors neglected in the theory by Mander et al and correct some unrealistic assumptions made in that theory. The predictions of the modified theory are then compared with the results obtained from concentric loading tests on 18 reinforced concrete columns conducted at the University of Canterbury and the validity of the modified theory is assessed.
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An analytical study of a large panel system to be used in high seismicity areas is presented in the paper. The analytical investigations are supported by experimental results. Special attention is given to inelastic response history analysis. New mathematical models of the hysteretic behaviour of joints, taking into account shear slip and gap opening, were developed and incorporated into the DRAIN-2D-2 program. Due to the system’s suitable structural concept, a nearly monolithic response of SCT large panel buildings to strong earthquakes has been observed, which makes possible the construction of such buildings up to 10 stories high in zones with intensity IX.
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China is one of the most earthquake-prone countries in the world and has suffered many disasters. During the last twenty years, especially since the Tangshan earthquake of July 1976 which killed 242,000 people and disabled almost 200,000 people, the Chinese government and the whole society have paid more attention to and made a huge effort to deal with earthquakes. Earthquake engineering became an essential project in the whole country and much more progress has been made since then. In this paper, some brief information about Chinese earthquakes and earthquake engineering is given. It is a simple introduction only, to give a general understanding of China's earthquake problems.
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An analytical study is made of the response to strong base motion of reinforced concrete silo structures having energy dissipation redundant members. The structural model consists of an axisymmetric silo body supported by reinforced concrete columns. Analytical methods used include inelastic dynamic response history analysis, inelastic static analysis, and elastic modal spectral analysis (Building Code of China). The sensitivity of the structural parameters, such as the location of redundant members, relative linear stiffness, and reinforcement ratios, are examined for lateral force and ground motions. Based on the data presented, it is concluded that the advantages of energy dissipation redundant members are of ensuring yielding hinges occur in selected elements, improving the distribution of internal forces, and providing increased ductility. Numerical examples are discussed to show the application potential.
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In this paper, the static substructure method based on the Ritz vector direct superposition method is suggested for analysing the dynamic response of structures. The advantage of this algorithm is that the computer cost can be reduced and the static analysis and the dynamic analysis of large structures can be simplified by using the identical static substructure method.
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On October 1, 1987 Southern California experienced the first earthquake for more than sixteen years that had sufficient strength to cause casualties and significant structural damage. The more important results of the event, and of the major aftershock which followed three days later, are summarised with particular reference to the successes in the mitigation of seismic effect which have been achieved both by the application of more stringent code requirements, in the case of new buildings, and by strengthening procedures in the case of existing ones.
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Several alternative seismic retrofit and strengthening solutions have been studied in the past and adopted in practical applications ranging from conventional techniques, utilizing braces, jacketing or infills, to more recent approaches such as supplemental damping devices or advanced materials (e.g. Fibre Reinforced Polymers, FRP, or Shape Memory Alloys, SMA). A series of controversial issues are implicit in the complex decision-making process of seismic retrofit, where both rational and counter-intuitive solutions can satisfy some of the most critical aspects of multi-level performance-based seismic retrofit criteria. Interesting and fascinating suggestions and lessons can be obtained by reviewing the current trends in new design (i.e. innovative solutions for the future generation of buildings systems) as well as the architectural solutions used by the ancients. While walking this “bridge of knowledge” of our cultural heritage with the critical eyes of a curious and passionate observer, we can observe surprising commonality in engineering problems and their successful (and recently attempted) solutions. Understanding and implementing this heritage could lead to a uniquely stable platform for major breakthroughs in the development of “new solutions” in seismic design and retrofit.
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A seismic financial risk analysis of typical New Zealand reinforced concrete buildings constructed with topped precast concrete hollow-core units is performed on the basis of experimental research undertaken at the University of Canterbury over the last five years. An extensive study that examines seismic demands on a variety of multi-storey RC buildings is described and supplemented by the experimental results to determine the inter-storey drift capacities of the buildings. Results of a full-scale precast concrete super-assemblage constructed and tested in the laboratory in two stages are used. The first stage investigates existing construction and demonstrates major shortcomings in construction practice that would lead to very poor seismic performance. The second stage examines the performance of the details provided by Amendment No. 3 to the New Zealand Concrete Design Code NZS 3101:1995. This paper uses a probabilistic financial risk assessment framework to estimate the expected annual loss (EAL) from previously developed fragility curves of RC buildings with precast hollow core floors connected to the frames according to the pre-2004 standard and the two connection details recommended in the 2004 amendment. Risks posed by different levels of damage and by earthquakes of different frequencies are examined. The structural performance and financial implications of the three different connection details are compared. The study shows that the improved connection details recommended in the 2004 amendment give a significant economic payback in terms of drastically reduced financial risk, which is also representative of smaller maintenance cost and cheaper insurance premiums.
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Engineered facilities are deemed safe if they have little or no probability of incurring damage when subjected to regular actions or natural hazards. Any probability of the performance of any designed system (i.e. capacity) not being able to meet the performance required of it (i.e. demand) results in risk, which might be expressed either as a likelihood of damage or potential financial loss. Engineers are used to dealing with the former (i.e. damage), which gives a fair indication of repair/strengthening work needed to bring the system back to full functionality. Nevertheless, other non-technical stakeholders (such as owners, insurers, decision-makers) of the designed facilities cannot read too much from damage. Hence, risk, if interpreted in terms of damage only, will not be comprehended by all stakeholders. On the other hand, financial risk expressed in terms of probable dollar loss in easily understood by all. Therefore, there is an impetus on developing methodologies which correlate the system capacity and demand to financial risk. This paper builds on the existing probabilistic risk assessment methodology and extends it to estimate expected annual financial loss. The general methodology formulated in this paper is applicable to any engineered facilities and any natural hazard. To clarify the process, the proposed methodology is applied to assess overall financial risk of a highway bridge pier due to seismic hazard.
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The results of earthquake risk assessments should be presented in ways that will help facilitate risk management decisions. So the measures of risk that are chosen need to be those that will assist decision-makers. Annualised Loss may not be the best basis on which risk management decisions can be made. The Conditional Expected Value of the loss, defined for a suitable set of probability ranges, is a promising measure of the risk because it is similar to a scenario loss and can be readily comprehended by decision-makers. Utility Theory provides a further measure by taking account of individuals’ perceptions of the severity of losses. It can be combined with the concept of Net Present Value to give an overall measure of the risk in terms of the value judgements of the individual decision-maker. The reduction in risk that would result from proposed mitigation works can be readily assessed, so that the decision-maker who is faced with the costs of mitigation is in a position to assess the benefits.
