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Structure bodies and surrounding soils in certain types of bridges and tunnels may be prone to collisions during earthquake. A dynamic system composed of discrete and finite elements is developed using explicit formulation for equations of motion, and nonlinearities in soils and at interfaces of disjoined regions are implemented. Time history solutions are carried out to examine the plastic deformation in soils as well as the integrity of structures. Two case studies are presented in which collisions among disjoined regions are anticipated in the event of extremely large earthquakes. Case one is based on a replica from a quake-stricken bridge, to illustrate that a backfill with moderate soil strength may be used as an energy-dissipating buffer to contain the shaken loose decks. The other case involves an underground subway station box with slurry walls alongside, to exemplify the seismic resistance of the dual-wall system.

Research and development of seismic response control devices has gained prime importance recently, due to an increased number of devastating earthquakes. Passive control systems are now accepted all over the world and hence research in this area is continuing to develop reliable, efficient and cost effective devices along with constitutive modeling. This paper begins with qualitative description and comparison of passive, active and semiactive control systems. Further, it mentions advantages of passive control systems over the others. A detailed literature review of passive devices is then provided which includes the historical development of the devices, their dynamic behavior, testing of these devices incorporated in the structural models and their analytical formulations. The pros and cons of these devices in retrofitting of structures and their first and recent applications in a wide variety of structures are also discussed. The passive response control systems that are discussed include viscoelastic dampers, yielding dampers, viscous dampers, friction dampers, tuned mass dampers, tuned liquid dampers, tuned liquid column dampers, superelastic dampers, like shape memory alloy dampers and base isolators.

This paper presents a simplified modeling strategy for simulating the nonlinear behavior of reinforced concrete (RC) structures under seismic loadings. A new type of Euler–Bernoulli multifiber beam element with axial force and bending moment interaction is introduced. To analyze the behavior of RC structures in the axial direction, the interpolation of the axial strain is enriched using the incompatible modes method. The model uses the constitutive laws based on plasticity for steel and damage mechanics for concrete. The proposed multifiber element is implemented in the finite element Code_Aster to simulate the nonlinear behavior of two different RC structures. One structure is a building tested on a shaking table; the other is a column subjected to cyclic loadings. The comparison between the simulation and experimental results shows that the performance of this approach is quite good. The proposed model can be used to investigate the behavior of a wider variety of configurations which are impossible to study experimentally.

The compressive deformation is mainly contributed by axial compressive deformation and high-order in-plane and out-of-plane global buckling deformation for conventional buckling-restrained braces (BRBs). A novel type of all-steel BRBs with perforated core plates, termed as perforated BRBs (PBRBs), are proposed in this study, where shear deformation can occur in addition to the aforementioned deformations in a conventional BRB under compression. Experimental study was carried out using five specimens with different configurations of holes under cyclic loading. Stable hysteretic properties, high ductility, and energy dissipation capacity were obtained for the PBRBs. The effects of two parameters, i.e. the slenderness ratio of the chord and hole spacing factor defined as the ratio of the hole length to the hole spacing, on seismic performance of the specimens were investigated. The compressive deformation mechanisms of the PBRBs were further investigated through a numerical study. The compressive deformation was found to be composed of axial compressive deformation, flexural deformation owing to in-plane and out-of-plane global buckling, and in-plane shear deformation of the latticed core plate.

The distribution of seismic loading to each storey of a building depends on a number of factors, mainly on the periods, mode shapes and modal participation. The estimation of these dynamic characteristics is essential in analyzing the seismic response of multi-storey buildings. Based on a rigorous dynamic analytical model of the building, this research provides a novel database of vibration modes of multi-storey buildings with reinforced concrete (RC) shear walls. The Stodola–Vianello iterative method was used to determine these. The first modes of vibration, cumulating a modal mass participation ratio (MMPR) greater than 90%, are summarized and presented in a table form. The results are equally valid for uniform buildings with masonry infill walls. The research has highlighted that the eigenvectors are independent of the values of the mass and the mechanical characteristics of the structure (the modulus of elasticity, the moment of inertia and height) but also on the variation of these characteristics over the height of the building. Consequently, for shear wall buildings with identical storeys, the eigenvectors, the MMPRs and the modal participation factors are accurately determined for this type of structure. The significance of the research consists of providing a table that engineers and researchers can easily use to determine the dynamic characteristics of the building, thus avoiding repetition of the calculations relating to this type of buildings. The study has also highlighted the importance of selecting the appropriate dynamic behavior of the structure for seismic design.

We present a preliminary investigation of compression of segmented 3D seismic volumes for the rendering purposes. Promising results are obtained on the base of 3D discrete cosine transforms followed by the SPIHT coding scheme. An accelerated version of the algorithm combines 1D discrete cosine transform in vertical direction with the 2D wavelet transform of horizontal slices. In this case the SPIHT scheme is used for coding the mixed sets of cosine-wavelet coefficients.

We present an algorithm that compresses two-dimensional data, which are piece-wise smooth in one direction and have oscillatory events in the other direction. Fine texture, seismic, hyper-spectral and fingerprints have this mixed structure. The transform part of the compression process is an algorithm that combines the application of the wavelet transform in one direction with the local cosine transform (LCT) in the other direction. This is why it is called hybrid compression. The quantization and the entropy coding parts in the compression process were taken from SPIHT codec but it can also be taken from any multiresolution based codec such as EZW. To efficiently apply the SPIHT codec to a mixed coefficients array, reordering of the LCT coefficients takes place. When oscillating events are present in different directions as in fingerprints or when the image comprises of a fine texture, a 2D LCT with coefficients reordering is applied. These algorithms outperform algorithms that are solely based on the the application of 2D wavelet transforms to each direction with either SPIHT or EZW coding including JPEG2000 compression standard. The proposed algorithms retain fine oscillating events including texture even at a low bitrate. Its compression capabilities are also demonstrated on multimedia images that have a fine texture. The wavelet part in the mixed transform of the hybrid algorithm utilizes the Butterworth wavelet transforms library that outperforms the 9/7 biorthogonal wavelet transform.

Parametric analysis of hollow precast prestressed piles indicated that under certain conditions of loading and geometry, plastic hinge formation could be expected in the pile shaft below ground level. Four half-scale model precast prestressed piles were tested in flexure to characterize plastic hinge development. The test rig simulated the subgrade moment pattern found in an in situ pile, and simulated external confinement from the soil around the pile shaft. Parameters varied were transverse reinforcement ratio, presence of external confinement, and presence of nonprestressed longitudinal steel in the plastic hinge region. The model piles were found to be insensitive to parameter variation. Failure occurred at similar levels of structural displacement in all cases, and in all cases took the form of compression failure of the pile wall. The piles had limited ductility, less than μ_Δ = 4 in all cases.

Large seismic isolation bearings and/or dampers are currently used to seismically retrofit several long-span bridges. These large devices must be thoroughly tested at full-scale with real-time seismic demands, necessitating new, larger seismic testing facilities. Accurate performance characterisation of these devices depends on thorough characterisation of the seismic testing facility itself. One component of this essential systems' characterisation is a mathematical simulation model. Although linear modelling techniques have traditionally been used to characterise seismic facilities, many of the large system's unique behaviours, parameters and non-linearities significantly reduce the accuracy of linear modelling techniques. These significant characteristics are discussed in detail. A more comprehensive non-linear modelling approach is required for these large facilities, and a simulation model using a non-linear time-history dynamic analysis approach is outlined.

Shape memory alloys (SMAs) are a class of materials that have unique properties, including Young's modulus-temperature relations, shape memory effects, superelastic effects, and high damping characteristics. These unique properties, which have led to numerous applications in the biomedical and aerospace industries, are currently being evaluated for applications in the area of seismic resistant design and retrofit. This paper provides a critical review of the state-of-the-art in the use of shape memory alloys for applications in seismic resistant design. The paper reviews the general characteristics of shape memory alloys and highlights the factors affecting their properties. A review of current studies show that the superelastic and high-damping characteristics of SMAs result in applications in bridges and buildings that show significant promise. The barriers to the expanded use of SMAs include the high cost, lack of clear understanding of thermo-mechanical processing, dependency of properties on temperature, and difficulty in machining.

Non-ductile response of structural elements, particularly columns, has been the cause of numerous documented failures during earthquakes. The objective of this experimental study was to evaluate the non-linear behaviour of non-ductile reinforced concrete short columns under lateral cyclic deformations and to evaluate rehabilitation schemes. Three reinforced concrete short columns were tested under cyclic lateral loads and constant axial load. The behaviour and effectiveness of different rehabilitation systems using carbon fibre reinforced polymers (CFRP) were investigated. Two different techniques to improve concrete confinement were used in the two rehabilitated specimens. It was found that it is possible to eliminate the non-ductile modes of failure of short column using anchored CFRP wraps. In addition, an analytical model to predict the confining effect and the total shear resistance of rectangular reinforced concrete columns with anchored fibre wraps was introduced. The confinement model is an extension to an available model for concrete confined by steel reinforcement. The model was used to predict the shear capacity of the tested specimens and has shown good results.

The research work presented in this paper deals with the seismic assessment of hollow bridge piers strengthened with fibre-reinforced polymer (FRP). The scope of the strengthening is to overcome some common deficiencies derived from the use of non-seismic design rules, which can often lead to inadequate response when operating in cyclic loading. The strengthening design was studied by means of a parametric analysis considering different fibres and geometrical parameters applied to typical case studies. Quasi-static cyclic tests were performed on five 1:4 scaled piers designed according to old non-seismic Italian codes and strengthened according to the previous analytical study. Efficiency of FRP strengthening was evaluated by comparing the experimental results with those obtained in a previous experimental research performed on similar non-strengthened specimens. Base shear versus lateral deflection curves, dissipated energy and collapse mechanisms comparison shows the achievable effectiveness once the debonding risk has been overcome.

Feasibility of a proposed seismic retrofitting technique for typical bridges in the Central US has been studied. The retrofitting technique is based on modifying the fixity conditions of the bearings for response modification purposes to eliminate the need for costly retrofitting of substructures. For this purpose, a seismically vulnerable bridge, typical of those in the Central US was selected. Detailed seismic analyses of the bridge were then conducted. It was found that its bearings, wing-walls and pier foundations needed to be retrofitted. A conventional retrofitting strategy was developed and the cost of retrofit was estimated. Next, the abutment bearings were fixed longitudinally to modify the response of the bridge so as to alleviate the effect of seismic forces transferred to vulnerable pier foundations. It was observed that the proposed retrofitting technique effectively mitigated the seismic forces transferred to the pier foundations and eliminated the need for their costly retrofitting. Thus, the proposed retrofitting method may be used for economical seismic retrofitting of such bridges in the Central US or in similar regions of low to moderate risk of seismic activity.

The displacement-based modelling methodology which has been applied extensively to buildings and bridges is extended herein to model the over-turning behaviour of rigid free-standing objects. The acceleration-displacement relationship associated with the overturning motion is linearised in order that the maximum displacement experienced by the object can be estimated using the elastic displacement response spectrum of the building floor. Whilst overturning motion is characterised by highly nonlinear acceleration-displacement properties, it was observed that modelling errors arising from nonlinear behaviour can be effectively controlled through limiting the maximum displacement of the object to some 50% of the ultimate displacement for overturning. The 50% safety margin is one of the key features in the proposed model.

Three rigid rectangular objects with depths of 100 mm, 300 mm and 500 mm were used initially to illustrate the use of the model. The height of these objects was 0.5 m, 1.5 m and 2.5 m respectively in order that every object has a common aspect ratio of 1:5. Despite that the aspect ratios of the objects were the same, they have very different levels of vulnerability to overturning. The proposed model was evaluated by nonlinear time-history analyses involving pulse-type excitations, recorded earthquake excitations and computer simulated earthquake excitations. Linear elastic models of buildings have also been used to simulate floor motions at the upper levels in the building. Predictions using the proposed linearised model based on the use of elastic response spectrum of the building floor was found to be very consistent with results obtained from nonlinear time-history analyses. Sufficient verification analyses have been carried out to provide the initial indications that the proposed linearised model seems to work well despite its simplicity.

For investigating the seismic behaviour of monolithic beam-column joints, a new technique of assessment of joint performance, termed the Shear Deformation Energy Index, is presented in this paper. Previous research efforts in this field were evaluated and the relative merits and drawbacks of each approach were highlighted. Primary variables influencing the seismic behaviour of joints were studied in the experimental phase of the current study. This included pseudo-static testing of nine interior beam-column subassemblages with different joint configurations. The parametric investigation of primary variables was complemented by studying the behaviour of specimens of eight different experimental programmes. For easy application of the technique in design practice, the Index is graphically represented versus its main variables in a design chart, referred to as the Performance Chart.

This paper presents a new concept on collapse prevention of existing RC buildings during a seismic event. The idea is to install steel panels in specified locations in the structure to reduce inter-story drifts. The panels are expected to work as a fuse in an electric circuit when a major earthquake occurs; the panels will attract the seismic forces and they may totally damaged but they will prevent severe damage in the main structural system. The proposed panels are light-weight, easy to handle, and can be constructed very quickly. Moreover, they are cheap and do not need formwork or skilled workers. To test the concept, a half-scale, single-story 3D reinforced concrete frame specimen was constructed at the shake-table laboratories of the Kandilli Observatory and Earthquake Research Institute of Bogazici University, and subjected to recorded real earthquake base accelerations. The amplitudes of base accelerations were increased until a moderate damage level is reached. Then, the damaged RC frames was retrofitted by means of steel panels and tested under the same earthquake. The seismic performance of the specimen before and after the retrofit was evaluated using FEMA356 standards, and the results were compared in terms of stiffness, strength, and deformability. The results have confirmed effectiveness of the proposed retrofit scheme.

To strengthen reinforced concrete (RC) structures against possible future earthquakes, several techniques are used in practice such as adding new RC shear walls, column jacketing using steel or RC or carbon fibers, adding steel bracing, and using seismic isolation and dampers. To apply these techniques, the whole building or part of it should be evacuated for several months and if this building is a school or a factory it means that the building will lose its function for several months during the strengthening construction. In this paper, parallel braced steel frame strengthening technique is proposed to strengthen the low or middle raise RC structures in which all the construction works are applied from outside of the building and do not affect the building function. The main features of this technique are ensuring the view, ventilation, and sunlight from windows after the retrofitting work is done. Furthermore, using the construction steel members lead to shortening the construction term, improve in quality, and reduce costs. The idea of this technique is to reduce the earthquake displacement demand on the nonductile existing RC structures by attaching steel frames to the building floors. These frames are parallel to the structural system of the building and their foundations are connected to the existing building's foundation. In doing so, it is expected that during an earthquake the building's interstory drifts will reduce in half and prevent building collapse. The parallel steel frames can be designed to the desired limit states using performance-based design method in FEMA or Turkish earthquake code. A study case of a factory building in Turkey is presented. The seismic performance of the building before and after the strengthening was evaluated according to the Turkish earthquake code TERDC-2007. Analysis results indicate the effectiveness of the proposed technique.

This paper presents an experimental program to investigate the effects of cross-sectional shape on the seismic performance of irregularly shaped reinforced concrete (RC) columns. Five groups of specimens that were one-quarter of typical columns of a prototype medium-rise building were tested to failure using shaking table. The loading procedure was successively increasing peak ground acceleration until the test structure collapsed. The specimens were designed with the same cross-section area but different flange width and flange thickness. The seismic response characteristics of all specimens such as drift capacity, energy absorption capacity and failure mechanisms of each specimen group are evaluated, compared and discussed in detail. Based on the current test data, design recommendation is provided to assist engineers in designing such irregularly shaped columns.

Historic buildings and monuments are an important part of our cultural heritage that must be protected and their sustainability ensured, especially when earthquakes occur. In this paper, a technique that uses structural steel frames is proposed as one way of strengthening unreinforced masonry (URM) in historical buildings. The idea underpinning this technique is to reduce the earthquake displacement demand on non-ductile URM walls by attaching steel frames to the building floors from inside. These frames run parallel to the structural system of the building and are fixed at their base to the existing foundation of the building. Furthermore, they are constructed rapidly, do not occupy architectural space, save the building’s historic fabric, and can be easily replaced after an earthquake if some minor damage ensues. The proposed technique was applied to a five-story historical masonry building in Istanbul. The results of seismic performance analysis indicate that even though the building has plan irregularities, the proposed steel frames are able to effectively enhance the building’s seismic performance by reducing inter-story drifts and increasing lateral stiffness and strength.

There is practical interest to apply active control at the global structural level and further decentralize control for more effective distributed robust control of local systems. In this paper, the effectiveness of a layered active vibration control strategy for seismically excited unbraced frames with piezoelectric sensors and stacked actuators is proposed and demonstrated. To form input-output decoupled subsystems, robust decoupling state feedback control on the reduced-order model forms the first layer. To limit transient response to the linearly elastic range and reduce detrimental effects of foreseeable uncertainties, the second layer is an uncertainty model under robust control. The third and final layer is a model-independent controller network using market-based control to mitigate unforeseeable uncertainties. The first two layers are based on state space control formulations that effectively control the design models and reduce the computational requirement of the third layer. The control effects and evaluation criteria would be based on seismic control benchmark problem.