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Isolation systems are currently being widely applied for earthquake resistance. During the design stage for such systems, the displacement response and input energy of the isolation layer are two of the main concerns. The prediction of these values is also of vital importance during the early stages of the structural design. In this study, the simple prediction method of double concave friction pendulum (DCFP) bearings is proposed, which can relate the response displacement of the isolation layer to the ground velocity through energy transfer with sufficient accuracy. Two friction models (the precise and simplified model) and a constant friction coefficient of double concave friction pendulum (DCFP) bearings are comprehensively validated by full-scale sinusoidal dynamic tests under various conditions. In addition, a response analysis, based on previous studies, was conducted using the friction models under selected unidirectional earthquake excitations, and the accuracy of using the simplified model in the response analysis was verified. Based on the response analysis data, this article verifies and optimizes the proposed prediction method by parameterizing the characteristics of earthquakes and combining the energy balance in order to gain a deeper understanding of the design of the isolation systems. [ABSTRACT FROM AUTHOR]

A reliable performance of anti-seismic devices when the upper-structure is subjected to strong biaxial seismic excitation is of vital importance to ensure the latter doesn't reach critical behavior. U-shaped steel dampers are hysteretic devices used to dissipate the earthquake-induced energy of base-isolated structures. In the framework of performance-based design, which is gaining more and more recognition, it is of particular importance to assess the performance of base-isolated structures with such dampers under different intensity levels of bidirectional ground motion. To achieve this goal, an analytical model able to simulate the bidirectional displacement response of an isolation system is adopted. Incremental dynamic analysis (IDA) is used to obtain the relation between the earthquake-induced bidirectional damage of U-shaped steel dampers and different intensity levels of the considered records. The performance of the dampers is categorized into 5 levels delimited by 4 limit states for which fragility curves are derived. The results obtained using the bidirectional approach are quantitatively compared to those given by employing an in-plane model (widely used in current design practices in Japan) with the purpose of assessing whether the latter provides unconservative estimates of the performance of the dampers. The main conclusion is that, for large seismic intensities, the safety margin against fracture of the dampers is significantly overestimated when an in-plane model is adopted. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

SUMMARY An application of a pin-supported wall-frame system in retrofitting an eleven-story steel reinforced concrete frame is introduced. The retrofit aims at enhancing integrity and avoiding weak story failure in an existing moment-resisting frame. Seismic performance of the building before and after the retrofit is assessed through nonlinear dynamic analysis. The results show that the pin-supported walls are effective in controlling the deformation pattern of the ductile frame and hence in avoiding weak story failure. With the well-controlled deformation pattern, carefully arranged energy dissipating devices are able to concentrate energy dissipations so that damage to the rest of the structure can be significantly reduced. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The energy dissipation capacity of a structure is a very important index that indicates the structural performance in energy-based seismic design. This index depends greatly on the structural components that form the whole system. Owing to the wide use of the strong-column weak-beam strength hierarchy where steel beams dissipate the majority of earthquake input energy to the structures, it is necessary to evaluate the energy dissipation capacity of the beams. Under cyclic loadings such as seismic effects, the damage of the beams accumulates. Therefore, loading history is known to be the most pivotal factor influencing the deformation capacity and energy dissipation capacity of the beams. Seismic loadings with significantly different characteristics are applied to structural beams during different types of earthquakes and there is no unique appropriate loading protocol that can represent all types of seismic loadings. This paper focuses on the effects of various loading histories on the deformation capacity and energy dissipation capacity of the beams. Cyclic loading tests of steel beams were performed. In addition, some experimental results from published tests were also collected to form a database. This database was used to evaluate the energy dissipation capacity of steel beams suffering from ductile fracture under various loading histories. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: Braced frames are commonly used as lateral-load resisting systems in seismic design. The braces are connected to the beams and columns by gusset plate connections. Fillet welds are commonly used to connect the gusset plates to the beams and columns. And the fracture of the interface welds were observed in the past research and earthquakes. This paper focused on the ultimate strength of interface weld connection between gusset plate and frame elements when the brace is in tension. Pilot experimental study was conducted with four specimens and proved that the evaluation recommended by AIJ works well. A verified finite element analysis model was developed to conduct a parametric study. The studied parameters are the brace angle, gusset plate size, and eccentricity of brace. From the parameter study, it is confirmed that the tensile brace axial force is primarily transferred to the interface weld within an extension Whitmore region, which is named as the effective region in the AIJ evaluation. And the extension Whitmore region is affected by the gusset plate geometrical constraint. A revised extension Whitmore region is suggested by considering the aforementioned parameters. The AIJ evaluation using the revised extension Whitmore region is also compared with the UFM, and showed better evaluation for the rectangular shape gusset plate. [Copyright &y& Elsevier]

• Dynamic substitution of floor slabs and slab-frame integrations. • Analytical model and approach for vertical floor acceleration (VFA) of RC frames. • VFA can be estimated via the response spectral method. • Validation via response history analyses conducted on finite element models. Vertical floor acceleration (VFA) analysis arises as an important issue for seismic design of floor-attached nonstructural components (e.g., ceilings). However, to date, estimating the VFA is hardly accessible in the literature. In this paper, an analytical method is proposed for the VFA of regular RC frames. Here "regular" means the frame has uniform spans along each principal direction, so the structure can be represented by a single-span analogy. Firstly, the fundamental frequency, modal mass, and modal participation factor of a clamped floor slab are analyzed based on the classic thin-plate theory. Then, the dynamic properties of the clamped floor slab are adjusted to account for the effect of the flexible beam restraints (non-clamped). According to the adjusted dynamic parameters, the beam-restrained slab is substituted by a single-degree-of-freedom system, and is assembled with the column-beam system to form the global dynamic model for the structure. Based on the assembled model, the analytical process for the VFA is presented. The feasibility of the model is validated using the finite element modelling (FEM) method. The vertical dynamic properties and the peak VFA of a single-, 3-, 6-, and 9-story frame are computed using the FEM and the proposed analytical approach. Results show that the VFA obtained from the analytical approach is close to the FEM outcomes. Furthermore, important features of VFA are revealed by the computation. It is shown that the VFA could be 10 times as large as the peak vertical ground acceleration. A larger VFA appears at the higher stories, yet the relationship between the VFA and the height is nonlinear because of the effects of the higher-order modes. [ABSTRACT FROM AUTHOR]

The Romanian territory has an important seismic potential in Europe, with the Vrancea source. The most destructive seismic events that occurred in Romania in the 20th century (November 10, 1940 and March 4, 1977) have revealed a high level of seismic vulnerability of the built environment. An important part of this built environment is represented by historical buildings, including the traditional ones (timber frame and infills from various materials as brick, stone, adobe, etc.). The investigations after seismic events from November 10, 1940 and March 4, 1977, revealed that the traditional buildings did not suffer any or important damages, thus showed their particular seismic behavior. Both the experience after similar seismic events from other countries as Turkey, Haiti, China, Myanmar, etc. and research studies from countries like Portugal, France and Japan, revealed an unexpected good behavior of such of buildings. Therefore, in this paper the results of the static cyclic tests on walls are presented. The test specimens were built according to the findings of the field investigations done on traditional buildings from Romania which are briefly presented hereby. The typology on which this paper focuses is the one found as predominant in the investigated areas (around the Vrancea seismic source). [ABSTRACT FROM AUTHOR]