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Improvement of the bonding and interaction between concrete and steel is crucial to achieving an optimal reinforced concrete member. The proposed technique in this paper is using perforated steel plates (PSPs) to reinforce two‐way concrete slabs. In this method, ordinary steel bar reinforcements in the tension region of the concrete slabs were replaced by PSPs. Concrete slabs reinforced with PSPs enhance structural characteristics with respect to concrete slabs reinforced with ordinary reinforcement (OR) due to the higher lateral stiffness of PSPs, the better confinement of concrete within the holes of PSPs, the biaxial performance of the steel in the tension region, and the efficient load transmission mechanism between the steel and concrete. In this paper, a comprehensive experimental investigation was conducted on two‐way concrete slabs reinforced with PSPs and ordinary steel bars. The behavior of PSPs slabs was evaluated in comparison with OR slabs in terms of failure types, ductility, energy absorption, stiffness, ultimate load, cracking load, and force transmission mechanism. Findings revealed that the PSPs slabs have higher ductility, energy absorption, and ultimate strength compared to the OR slabs. [ABSTRACT FROM AUTHOR]

There is considerable interest in structural health monitoring (SHM) and damage detection of bridges and considerable progress has been made in this field in recent years. However, several challenges such as sensitivity to low levels of damage and identification without the knowledge of the moving load remain and need to be precisely investigated by researchers. The current work addresses such challenges and proposes an efficient response sensitivity-based model updating procedure in time-domain for damage identification of railway bridges subjected to unknown moving loads. The bridge is modelled as an Euler-Bernoulli beam and the train is modelled as a set of sprung masses passing over the beam. Structural damage is considered as a reduction in the modulus of elasticity of the elements. Sensitivity analysis and Tikhonov regularization methods are adopted and used to solve the inverse problem of the model updating. To verify the efficiency of the model, two numerical models with multiple damage scenarios subjected to unknown moving loads are analyzed. In addition, the efficiency of the proposed method in the presence of measurement noise is also verified. Numerical results reveal that the proposed model-updating procedure simultaneously identifies structural damages as well as the unknown moving loads with an acceptable accuracy. The effect of critical parameters such as mass and speed of the moving vehicle on the accuracy of identification results is investigated as well. Based on the findings of this research, the proposed method can be adopted and applied to online and long-term health monitoring of real bridge structures. [ABSTRACT FROM AUTHOR]

The present study is aimed at determining the effect of variability in soil type and structure height on soil-structure system responses. In order to explore this innovative idea, a wide range of soil types and structure heights are assumed, and the responses are analyzed with respect to changes in soil type and structure height. It is intended to address the three-fold problem of determining under what circumstances soil-structure interaction (SSI) exerts significant effects on the results, on what condition it could be ignored, and whether taking account of SSI leads to conservative results. To verify the numerical models, the results are compared with those derived from the NEHRP method. Five planar concrete frames are examined under the action of thirty earthquake records. Seven types of soil are considered. For modeling the soil-structure system, the direct method is employed. The plastic behavior of the soil is formulated based on the multi-surface (nested surfaces) concept; the yield surfaces of sand are of the Drucker-Prager type, and those of clay are of the Von Mises type. The exact Incremental Dynamic Analysis (IDA) is adopted for analyzing the soil-structure system. The results indicate that, for sandy soils, the SSI impact is greater for looser sub-soils. For clayey soils, the medium clay has the most powerful SSI effect. For low and medium rise buildings, the SSI effect is more profound as the structure becomes taller, but for high rise buildings, the SSI effect wears off with increasing height. [ABSTRACT FROM AUTHOR]

In this paper, the application of tuned mass damper in improving the response of structures is considered. At first, three frames of 3, 9 and 20 stories are evaluated in which time history analysis is done according to El - Straw earthquake. The maximum reduction of among the three mentioned frames belongs to a 20-stories structure in which the rate of story displacement reduction is between 25 to 45%, and this indicates that by increasing the height of the structure, the performance of tuned mass damper improved. In the second part, the effect of semi-active tuned mass damper is studied on a 10-stories frame. Studies showed that using a tuned mass damper system with viscous damper with controller force decreases the average of maximum displacement of roof story down to 39.9% and this amount of reduction is 22.8% for semi-active tuned mass damper. Finally, the performance of tuned Single and multiple mass Damper is evaluated on a 20-stories frame, and the results show that single and multiple dampers decrease structures 'responses and the performance of tuned multiple dampers depends on the mass and frequency ratio and also concluded that the performance of tuned multiple mass dampers is reduced by transition to middle of the structure stories. [ABSTRACT FROM AUTHOR]

Viscoelastic (VE) dampers can be efficiently used for improving the seismic behavior of structures and also retrofitting of existing structures. Efficient nonlinear dynamic analysis methods like the Incremental Dynamic Analysis (IDA), especially the one which is based on Modal Pushover Analysis (MPA), which has proved especially popular among researchers, are required for analyzing the structures with dampers. As the IDA method is too complicated and time consuming, the MPA-based IDA method was introduced, a method which is fast and cost effective and the results are accurate enough to be utilized. Adoption of a static analysis in the procedure of MPA-based IDA method encourages the speculation that this method cannot be used for structures with dampers. This misconception has led to the fact that no one has ever used this method for structures with additional damping. In the present article, it is intended to present an approach to promote the applicability of the MPA-based IDA method for structures with VE dampers. The proposed approach is verified by the exact IDA method and validated by a numerical example. The results indicate the sufficient accuracy of the proposed technique, in which the MPA-based IDA is employed for structures with VE dampers. [ABSTRACT FROM AUTHOR]

With the progresses made in the field of structural and earthquake engineering and with more exact knowledge gained on seismic behavior of structures, earthquake engineering and various structures have advanced a great deal and various types of analytical methods have been developed for the assessment of structures. Dynamic analysis methods are aimed at determining the accurate behavior of structures and static analysis approaches are employed to predict structural behavior for engineering purposes. Most of nonlinear dynamic techniques are time-consuming and require a large volume of computations; moreover, performing these analyses and interpreting the obtained results need special skill and expertise. Conversely, although numerous approximations and simplifications in the nonlinear static approaches have extended and promoted their applications, they have reduced the accuracy of the results obtained by these methods. For evaluation of the seismic performance of structures, the precision and speed of the process of different analytical methods are the most important factors. This has led to the development of many novel methods based on the modern nonlinear static and dynamic analyses concepts. In this research, the results of two new different methods (modal incremental dynamic and incremental modified pushover analysis) for two 3-story and 9-story steel moment-resisting frames, as typical low and mid-rise steel lateral load-carrying systems, have been evaluated and compared with the results of the exact nonlinear incremental dynamic analysis. Based on the findings of this research, for the studied frames, the application of both analytical methods for low-rise frames gives appropriate results for all seismic records at different intensity levels; while for the mid-rise frames, the accuracy of the static analysis method has decreased; although a proper safety margin exists for this approach and also the sensitivity of the static method is less than that of the dynamic method. [ABSTRACT FROM AUTHOR]