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In this paper, finite element analysis software “DIANA” is implemented to simulate quasi-static cyclic loading test results of three full-scale beam-column joints cast with high-strength self-compacting concrete (HSSCC). The specimens were designed according to the New Zealand concrete standard (NZS3101 2006). Material models for concrete and steel were calibrated based on the physical characteristics of the materials derived either from laboratory tests or using expressions available in literature. Two-dimensional curved-shell elements were used in modelling the specimens. As the specimens were designed following the code requirements for seismic actions, bond between the reinforcement and concrete was assumed as perfect. In order to obtain a more representative prediction, both the longitudinal and transverse reinforcement were modelled in their actual locations. Pushover analyses were first conducted to check the mesh sensitivity; after which the modelled specimens were subjected to reversed cyclic loading histories applied in the experimental tests. Seismically important response parameters such as damping, stiffness, concrete and steel contributions in the joint shear resistance, joint shear deformation, strain development in the joint stirrups, elongation of the plastic hinge zone, development of compressive stress, and cracking pattern were extracted from the analytical predictions and compared to the experimental results. It was found that the adopted modelling and analysis approach was capable of predicting cyclic performance of HSSCC beam-column subassemblies with reasonable accuracy.
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Rocking action at the foundation-structure interface has long been proposed to isolate structures from strong ground motion. In this paper, the fundamental concept of rocking isolation is examined in depth to guide further design efforts. This is achieved by first deriving an analytical model of a flexible structure freely rocking on rigid ground. Decomposing the coupled equations of motion of the model into their modal components provides new information on the mechanics of rocking isolation. After identifying the salient parameters needed to quantify rocking isolation, equations to predict the lateral accelerations, base shear and overturning moments arising during rocking are provided. The analytical model and the simplified equations are then validated using some of the earliest experiments on rocking structures, which were completed in New Zealand. These validations clarify poorly understood phenomena concerning rocking isolation, such as how rocking and vibrations of the structure couple, how this influences the excitation mechanisms of the structure, resulting in seismic shear forces and overturning moments larger than those required for uplift. The findings provide an analytical basis for designing efficient rocking systems that successfully limit force demands.
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Pull-tests and shake-table tests of office-type furniture on carpet and vinyl flooring were performed to obtain friction coefficients, and validate the mechanics of content sliding and current modelling approaches. The static friction coefficient, μs, for furniture with and without wheels was between 0.13-0.30 and 0.36-0.45 on carpet flooring, respectively, and 0.07-0.13 and 0.39-0.45 on vinyl flooring, respectively. The kinetic friction coefficient, μk, was similar to μs for carpet flooring, but was up to 38% lower for vinyl flooring. Shake-table tests using sinusoidal floor excitations showed that: (i) the sliding force hysteresis loop was elasto-plastic on average, and (ii) peak total floor velocity significantly affected the extent of sliding. While it was found that the maximum sliding displacement obtained by numerical integration methods differed by a factor between 0.3 and 3.0 on a case-by-case basis, the average error was just 5%. Preliminary sliding analyses of furniture resting on single-degree-of-freedom structures of varying stiffness using a suite of ground motion records were performed. It was found that (i) the extent of sliding was not necessarily more severe in stiffer buildings despite the greater peak total floor acceleration demands, and (ii) considering only μk in content sliding analyses still produced reasonably accurate predictions.
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Viscous fluid damping has been used worldwide to provide energy dissipation to structures during earthquakes. Semi-active dissipation devices have also shown significant potential to re-shape structural hysteresis behaviour and thus provide significant response and damage reduction. However, semi-active devices are far more complex and costly than passive devices, and thus potentially less robust over time. Ideally, a passive device design would provide the unique response behaviour of a semi-active device, but in a far more robust and low-cost device. This study presents the design, development and characterization of a passive Direction and Displacement Dependent viscous damping (D3) device. It can provide viscous damping in any single quadrant of the force-displacement hysteresis loop and any two in combination. Previously, this behaviour could only be obtained with a semi-active device. The D3 device is developed from a typical viscous damper, which is tested to evaluate the baseline of orifice sizing, force levels and velocity dependence. This prototype viscous damper is then modified in clear steps to produce a device with the desired single quadrant hysteresis loop. The overall results provide the design approach, device characterization and validation for this novel device design.
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Many moderate and strong earthquakes have occurred in Indonesia. However, since ground motion records are unavailable, a concise earthquake peak ground acceleration (PGA) map has never before been constructed. Several efforts have been made to construct PGA maps after the Mw6.4 2006 Yogyakarta earthquake, i.e. earthquake PGA maps by researchers [1–4]. However, due to their use of completely different earthquake sources, methods of analysis and by using exclusion criteria of ground motion prediction equations (GMPE), the maps differed greatly and did not match the actual structural damage found in the field. Estimation of a 2006 Yogyakarta earthquake PGA map became possible after field surveying of the Imm conducted by Wijaya [5]. The estimated PGA map was constructed based on the isoseimic lines, intensity prediction equation (IPE) by Wijaya [5] and peak ground acceleration at YOGI and BJI station control points, as published by Elnashai et al [6]. A set of most recent GMPEs were chosen, as they closely predicted the PGA at two control points. An Extrapolation Method was developed in which the PGA between YOGI and BJI stations would be extrapolated to all data points in the field to yield the 2006 Yogyakarta seismic PGA map. Result of the investigation indicated that the pattern of the new PGA map does not form a circle with radius R, but occurs longitudinally following the direction of the Opak River fault trace and closely follows the pattern of Imm map and damage to buildings in the field. It was found that the maximum upperbound PGA reached ±0.50-0.51g and it did not occur at the epicenter area but instead took place in relatively deep soil deposit approximately ±2 km west of the Opak River fault.
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Masonry infilled reinforced concrete frame buildings built prior to the introduction of modern seismic provisions have been observed to undergo damage in and around the masonry infill walls during most recent moderate to severe earthquakes. Fibre reinforced cementitious matrix (FRCM) is one of several retrofitting options available to limit such earthquake induced damage to infill walls. An experimental program was undertaken herein to experimentally investigate the effectiveness of FRCM as a strengthening solution for vintage (i.e. built between 1880 and 1930) un-reinforced brick masonry (URM) and insulated concrete masonry (IMU) infill walls. A total of 16 masonry assemblages were tested under in-plane diagonal load, of these 8 were constructed replicating vintage URM whereas the remainder were constructed using modern IMU. IMU is a preferred masonry type in hot and humid regions owing to its superior insulting capability. Different polymer fabrics (i.e., carbon, glass and basalt) were applied over both faces of test walls, with two replicate test walls receiving the same FRCM strengthening details. One test wall of each masonry type was tested as-built to serve as a control specimen for comparison. One wall of each masonry type received two layers of basalt FRCM. The investigated aspects included stress-strain behaviour, stiffness, and ductility. Shear strength increment observed due to single layer of FRCM application was 422-778% for vintage URM and 307-415% for modern IMU. FRCM also substantially increased the ductility capacity of the masonry assemblages.
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In this paper, the relation between the steel cylindrical tank geometry and the governing critical damage mode of the tank shell is numerically determined for all practical ranges of liquid storage tanks (aspect ratio H/D = 0.2 to 2). In addition, the interaction between the seismic intensity, soil type, acceptable seismic risk and tank geometry along with the extra material demanded by the seismic loads is examined based on the provisions of major codes. The importance of seismic factors on the economics of the design of a liquid tank in zones with high seismic activity is comprehensively discussed. In this regard, an empirical relation to estimate the steel volume required for specific seismic conditions and tank geometries is proposed based on the results of analysis.
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Since 2010, twelve post-tensioned timber (Pres-Lam) buildings have been constructed throughout the world. In high seismic areas, Pres-Lam technology typically combines unbonded post-tensioning tendons and supplemental damping devices to provide moment capacity to beam-column, wall-foundation or column-foundation connections. Over time creep within the timber elements leads to losses in post-tensioning forces reducing the connection moment capacity. This paper analyses how different post-tensioning loss scenarios, depending on the beam-column joint detailing, impact the building’s seismic response. Two case study buildings were designed and investigated using the Acceleration Displacement Response Spectrum (ADRS) method and Non-Linear Time History Analysis (NLTHA) to predict seismic performance. These buildings were considered to be located in areas of high and low seismic risk, leading to designs with and without the use of damping devices, respectively. The results show that the building with additional damping responded with similar peak displacements, even under extreme loss scenarios. In comparison, when supplemental damping was not used, peak displacements increased significantly with post tensioning losses.
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The behaviour of regular multi-span simply-supported bridges is strongly dependent on the behaviour of its piers. The response of a pier is governed, in general, by different mechanisms: flexure, shear, second order effects, lap-splice of longitudinal bars or their buckling. The flexural behaviour is an important part of the problem, and it can be characterised through the equivalent plastic hinge length and the Moment-Curvature law of the fixed end. In this paper, a procedure to calculate the Moment-Curvature relationship of circular RC sections is proposed which is based on defining the position of few characteristic points. The analytical formulation is based on adjusted polynomial functions fitted on a database of fibre-based analyses. The proposed solution is based on three parameters: dimensionless axial force, mechanical ratio of longitudinal reinforcement, geometrical ratio of transverse reinforcement. A benchmark case is presented to compare the solution to a FEM non-linear analysis. Even if it is based on few input data, this solution allows to have good indicators on the material performances (e.g. yielding, spalling, etc). For these reasons, the proposed approach is deemed to be particularly effective in performing quick yet accurate mechanics-based regional-scale assessment of bridges.
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One barrier to adopting seismic loss estimation frameworks in New Zealand engineering practice is the lack of relevant fragility functions which provide probabilities of exceeding certain levels of damage (e.g. cracking of gypsum wallboards) for a given demand (e.g. interstorey drifts). This study seeks to address this need for four different building components; interior full-height steel-framed plasterboard partition walls, unbraced suspended ceilings, precast concrete cladding, and steel beam-column joints with extended bolted end-plate connections. Fragility functions were sourced from literature, and their potential for use in New Zealand is evaluated considering similarities in component detailing with local practices. Modifications to a number of fragility functions, including generalizations for easier adoption in practice, are proposed. A loss estimation case study of a 4-storey steel moment-resisting frame is performed to investigate the significance of fragility function selection. It is shown that the definition of damage states can have a noticeable influence on the assessment of incurred repair cost of individual building components. This indicates that fragility functions should be carefully selected, particularly if the performance evaluation of each individual component is of utmost importance. However, the observed difference in expected annual repair cost of the entire building was small, indicating that in cases where fragility functions are not readily applicable for use in New Zealand, other fragility functions may be used as placeholders without drastically altering the outcome of loss analysis for the entire building.
