Vibration is a serious concern for tall structures during a natural disaster such as earthquake, wind storms, sea waves and hurricanes. The risk of occurrence of structural damage can be decreased by using a controlled vibration system to... more
Vibration is a serious concern for tall structures during a natural disaster such as earthquake, wind storms, sea waves and hurricanes. The risk of occurrence of structural damage can be decreased by using a controlled vibration system to increase the damping characteristics of a structure. Damping is defined as the ability of the structure to dissipate a portion of the energy released during a dynamic loading event. The aims of this study are (1) to investigate a 4-storey 2D steel frame retrofit with viscous damper to reduce its vibration and (2) to demonstrate the performance of such a damper when fitted to a structure by analysis and tests the model. Therefore, a series of shaking table tests of the 4-storey 2D steel frame with and without viscous damper (VD) was carried out to evaluate the performance of the structure. The results of the experimental tests illustrate that viscous dampers decrease the structural responses of slender frame without changing their behavior on the shaking table. In other words, the displacement of the structure is reduced, however, there is no any transition of flexible to stiff structure related to its dynamic responses.
The current ASCE 41-13 standard does not provide recommendations or include references regarding computational modeling strategies for performance-based seismic assessment of in-plane walls in unreinforced masonry buildings. This paper is... more
The current ASCE 41-13 standard does not provide recommendations or include references regarding computational modeling strategies for performance-based seismic assessment of in-plane walls in unreinforced masonry buildings. This paper is attempting to fill this research gap through an evaluation of the reliability of three suitable simplified nonlinear modeling approaches for in-plane walls and providing a comprehensive list of references on more complex modeling strategies for masonry buildings. The models-namely nonlinear spring macro-models, equivalent frames and a layered shells-were validated under general monotonic, cyclic quasi-static and earthquake loading on two full-scale wall tests reported in the literature. To demonstrate their practical use, the models were developed in the commercial software SAP2000. The numerical simulations showed that the pushover capacity curve and hysteretic loops for base shear vs. roof displacements were generally in acceptable correlation with the experimental results.
This paper introduced the practical aspects of the shake table testing on the scaled model and taking its interference in the actual model. Readings are taking at the each floor by the FFT analyzer. The main objective of this project is... more
This paper introduced the practical aspects of the shake table testing on the scaled model and taking its interference in the actual model. Readings are taking at the each floor by the FFT analyzer. The main objective of this project is to study the behavior of various structural models on shake tables available in the department of Applied Mechanics, by making shake table systems operational. The study is reported in different scaled models of buildings of various plans and materials like aluminum and steel. The acceleration of different responses of the structural models is measured with sinusoidal base excitation of different amplitudes and frequencies. It is observed that the study also involves comparison of shake table (experimental) responses with the corresponding area time history analysis results obtained using the structural analysis package SAP2000.
This paper presents the shake table test of a one-forth scaled model, representing a typical Pakistani three stories confined brick masonry building. The model was constructed following complete model similitude and subjected to a series... more
This paper presents the shake table test of a one-forth scaled model, representing a typical Pakistani three stories confined brick masonry building. The model was constructed following complete model similitude and subjected to a series of sinusoidal base motions of increasing amplitude at a constant frequency equivalent to the predominant frequency of JMA Kobe-1995 earthquake record. The dynamic test data was processed and analyzed to generate the forcedeformation curve, ductility ratio and response modification factor of the system. A sheardominated failure mode was observed. As expected, the ground storey was found to suffer more damage than the other two stories. Out-of-plane failure of walls and crushing of concrete in confining elements were also noted in the final test runs. Based on the damage mechanism and force-deformation characteristics, various performance levels are suggested.
ABSTRACT Based on steel strains recorded during shake table tests of six wall specimens, the effect and contribution of steel reinforcement to peak shear strength and displacement capacity of low-rise concrete walls is assessed and... more
ABSTRACT Based on steel strains recorded during shake table tests of six wall specimens, the effect and contribution of steel reinforcement to peak shear strength and displacement capacity of low-rise concrete walls is assessed and discussed. The experimental program includ-ed four variables such as wall geometry, concrete type, web steel ratio and type of web reinforcement. Wall response was assessed through effective steel strains in vertical reinforcement, efficiency factors of wall reinforcement, contribution of web horizontal rein-forcement to wall shear strength, and the effect of type of web reinforcement to wall displacement.
Soil-abutment-structure interaction could affect the seismic response of bridges considerably. Skew angle might significantly influence the mobilized passive resistance of the backfill soil and the behavior of soil-abutment system due to... more
Soil-abutment-structure interaction could affect the seismic response of bridges considerably. Skew angle might significantly influence the mobilized passive resistance of the backfill soil and the behavior of soil-abutment system due to the large induced in-plane rotations and translation of the superstructure, coupled with variations in stiffness and strength of backfill soil in skewed abutments. The current Seismic Design Criteria of the California Department of Transportation (Caltrans) does not include any special consideration for the skew angle effect on the passive capacity of soil-abutment systems. Previous experiments on skewed abutments were undertaken on abutments that were restrained against rotation with prescribed uniform displacements tested by gradually increasing lateral loads under static conditions, with no dynamic effect simulated. The effects of abutment rotation, impact on the abutment wall and dynamic earthquake forces were not studied. The overall objective ...
At present, the study of structural dynamics is mainly theoretical with access to certain simulations through software, however, this project attempts that the student may understand and physically observe the dynamic responses of... more
At present, the study of structural dynamics is mainly theoretical with access to certain simulations through software, however, this project attempts that the student may understand and physically observe the dynamic responses of experimental models. These models correspond to 2D - frames with multiple degrees of freedom that are subjected to acceleration in the base; this acceleration is generated by a Shake Table II, and the results obtained will be compared with theoretical results. These theoretical results were obtained based on modal decomposition and Newmark’s method for calculating the dynamic response, considering the linear variation in the acceleration of each floor. The application developed, ATH Dynamic Responses, provided the theoretical responses through a graphical interface friendly for the user. The experimental models are constituted by two materials: stainless steel for frame legs and acrylic sheets for floors; these were tested on a Shake Table II”. The data was acquired using accelerometers that were placed in each floor and in the shake table, and they were corrected both by baseline and with the low pass filter. The results obtained show that the instrumentation with the Shake Table II and the data acquisition with accelerometers provide results similar to the theoretical ones regarding dynamic responses and modal properties.
