153 publications from this institution
Behavior of column specimens reinforced with a new reinforcement, termed Prefabricated Cage System (PCS) is investigated. A total of 16 small-scale PCS and rebar reinforced column specimens with normal strength concrete were constructed and tested. The experimental data indicate that the PCS reinforced specimens have better overall performance and are more ductile than the equivalent rebar specimens. The effect of different parameters, such as the tube thickness, number of longitudinal reinforcements, transverse steel spacing, and crossties on the specimens' strength and deformation capacity are also investigated.
There are a large number of reinforced concrete buildings in seismically active areas of the world that are not built in accordance with modern seismic design provisions such as those published by American Concrete Institution ([ACI] Committee 318, 2008). In the United States and other parts of the developed world, these buildings were constructed between 1930s to mid 1970s according to the building code requirements of that time. Even today, in low to moderate seismic regions and in some developing countries that are in process of developing and implementing their seismic codes, reinforced concrete structures are being designed and built without essential seismic details deemed vital to withstand large lateral loads. These buildings often have low lateral displacement capacities and undergo rapid degradation of shear strength and axial load carrying capacity during strong ground motions and hence are extremely vulnerable to excessive structural damage or collapse during future earthquakes. In the past, the earthquakes have caused wide spread damage to the reinforced concrete structures with inadequate seismic design and construction practices. For example, during Kashmir (Pakistan) earthquake of 2005 and Haiti earthquake of 2010, extensive structural damage to residential, commercial and government buildings was observed (Earthquake Engineering Research Institute [EERI], 2005; Mid-America Earthquake [MAE] Center, 2005; U.S. Geological Survey [USGS]/EERI, 2010). The damage was attributed largely to lack of earthquake-resistant design, poor standard of construction and inferior quality of building materials. In majority of the collapsed or damaged structures, structural types, member dimensions and detailing practices (insufficient lap length, improper lap location and lack of confinement in columns etc) were found inadequate to resist forces imposed by these earthquakes.
This paper summarises improvements to the ASCE/SEI 41 concrete provisions considered for implementation in the new ACI 369 Guide for Seismic Rehabilitation of Existing Concrete Buildings. The paper is intended to inform the structural engineering community on the approach being taken by ACI 369 to provide engineers with the latest modeling approaches and acceptance criteria for the assessment and rehabilitation of existing concrete buildings. Through the removal of unnecessary conservatism, it is expected that these modifications will make the seismic rehabilitation of concrete buildings more cost effective.
Approximately 40% of the heavy industry in Turkey was located in the region affected by the 1999 Mw 7.4 Kocaeli earthquake. Twenty-four facilities representing different industries in the epicentral region were surveyed after the earthquake. Structural and nonstructural damage to these facilities is summarized and performance is reported using a damage classification scheme. Information on typical industrial-facility construction practice in Turkey is presented. Earthquake damage to the most common structural framing systems is highlighted. The structural performance of a small number of the facilities visited by the reconnaissance team is investigated.
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Current seismic design requirements specify lateral displacement or story drift limits to be compared with calculated results from structural analysis. The lateral displacements for different types of buildings are usually predicted through commercial structural software, which takes much computational time at the beginning of the structural design. In this research, a simplified equation is proposed to calculate lateral displacements of buildings under lateral loads with different distributions. The equation is developed to quickly predict the elastic and inelastic building displacements during preliminary design of new buildings or seismic assessment of existing buildings without performing expensive dynamic time history analyses using software. The proposed method is based on elastic beam theory and is compared with similar ASCE (American Society of Civil Engineers) 7–10 procedures. The accuracy of the proposed method is validated by the elastic and inelastic analysis using 2-D (two dimensional) and 3-D (three dimensional) frame buildings. Additionally, the equation is used to determine inelastic story displacements of ordinary, intermediate and special moment frames, and coefficient used to compute the inelastic story displacement according to the proposed equation are recommended in this study.
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Postearthquake reconnaissance and recent research on seismic risk analysis have shown that nonductile concrete frame structures are much more susceptible to collapse than modern code-conforming frames. The performance-based assessment paradigm has been a persistent research theme over the last decade within the earthquake engineering community in order to estimate seismic fragilities and earthquake loss for these nonductile concrete frames. This paper proposes a nonlinear performance-based methodology to evaluate different retrofit methods considering hazard level, target performance levels, and life-cycle cost estimates. The structural performance is the main parameter considered for the optimization, although a life-cycle cost analysis is also presented. As a case study, the longitudinal frame of an existing building was modeled considering the effect of flexural-shear-axial load interaction in order to capture column shear and axial failures. The presented performance-based procedure identifies the most economic retrofit solution that satisfies structural response requirements for a given performance level.
In this paper, progressive collapse performance of an existing multi-story building has been investigated through field experiments and computational simulations. The masonry load-bearing wall structure, Nosker House was located on the Ohio State University campus in Columbus, Ohio. During the experiments, four exterior first-story load-bearing walls were consecutively removed from the building, which was demolished immediately after the experiment. Due to lack of full-scale building test data, the data produced in this research has been a valuable addition to the state of knowledge on progressive collapse assessment of masonry buildings. The main goal of field experiments was to simulate the structural dynamic and static response of buildings that may experience collapse after sudden loss of walls. Another objective was to investigate how the internal forces are redistributed within the building after each wall is removed. In this study, three-dimensional model of the building was developed and analyzed to simulate the building performance and collapse potential. Computational models and simulations were examined and compared to the experimental data from the field tests. This study showed robustness of existing buildings and contribution of different structural components to collapse resistance.
. In this paper, two different convolutional neural networks (CNNs) are applied on images for automated structural damage detection (SDD) in earthquake damaged structures and cracking localization (e.g., detection of cracks, their widths and distributions) at various scales, such as pixel level, object level, and structural level. The proposed method has two main steps: 1) diagnosis, and 2) localization of cracking or other damage. At first a residual CNN with transfer learning is employed to classify the damage in the structures and structural components. This step performs damage detection using two public datasets. The second step uses another CNN with U-Net structure to locate the cracking on low resolution images. The implementations using public and self-collected datasets show promising performance for a problem that had remained a challenge in the structure engineering field for a long time and indicate that the proposed approach can perform detection and localization of structural damage with an acceptable accuracy.
