Studies on the quantification of energy benefits of a green roof have so far treated its parameter values only deterministically. In reality, however, these values may scatter over different ranges ...due to the inherent variation of vegetation and soil properties and also because of the unavoidable deviation from designated values during construction and/or actual operation of a green roof. Under such parameter uncertainty, green roof performance can no longer be predicted deterministically but rather probabilistically. The present study attempts to integrate the whole building energy simulation with a parametric uncertainty analysis. An example office building is used to systematically examine how the cooling and heating energy demands can be reduced by a green roof that replaces a conventional roof, when values of the most significant green roof parameters determined by sensitivity analysis are treated as random variables with prescribed probability distributions. An ensemble of green roof configurations is generated using Monte Carlo simulation with a Latin hypercube sampling technique. The coefficient of variation of the calculated energy savings is found almost linearly related to (with a slope of about 0.4) that of green roof parameters. Finally, implications of probabilistic energy analysis for more reliable green roof design are emphasized.
•Green roof energy calculation is integrated with parameter uncertainty analysis.•Leaf area index and soil thickness of a green roof are treated as random variables.•Monte Carlo simulation with a Latin hypercube sampling technique is employed.•Dispersion of energy savings is linearly related to that of green roof parameters.•Implication of probabilistic energy analysis on green roof design is emphasized.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
•Finite element modeling of PT steel connection and frame subject to column removal.•Capacity mainly contributed by beam arching action and strand catenary action.•Understanding of load ...redistribution and failure mechanisms of PT steel frames.•Implications for structural design of PT steel frames against progressive collapse.•Key differences between seismic and progressive collapse behavior of PT steel frame.
Post-tensioned (PT) steel frames, in which beams are connected to columns through high-strength PT strands, have been successfully developed in the past decade as a novel earthquake-resistant structural system. Compared to conventional steel moment frames, a PT steel frame demonstrates superior seismic performance, notably the minimum damages in main structural components and the self-centering capability under a design basis earthquake. Despite the abundant research on the seismic behavior of PT steel frames, there is an apparent lack of study on their load-redistribution behavior upon the notional removal of critical load-bearing columns, a commonly used threat-independent local structural damage scenario that potentially triggers the progressive collapse of the column-removed frame. This paper presents a first-of-its-kind numerical investigation on the unique structural behavior of PT steel connections and frames in redistributing the unbalanced gravity loads due to column removal. High-fidelity finite element structural models are constructed and validated using the available experimental data in the literature. The capacity of PT steel frames subjected to a gradually increasing vertical displacement along the removed column line is systematically studied. It is found that, besides the resistance of energy-dissipating elements, beam arching action and strand catenary action are the major sources of structural capacity of a PT steel frame against progressive collapse. The corresponding failure modes are identified and the design implications are suggested.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
AbstractA facile and effective method for retrofitting simple shear tab connections in a steel gravity frame is presented to improve its overall lateral force-resisting capacity. At a target shear ...tab connection, the existing gap between the beam flange and column face is snugly filled with a tapered steel plate, which is then field-attached to the column face. When a steel gravity frame is subjected to lateral loads (due to, for example, earthquake and strong wind), the retrofitted shear tab connection deforms and promptly engages the beam to bind the column via the filler plate, thereby exerting a horizontal thrust to the column at the retrofitted beam flange level. Hence, the moment arm between horizontal reactions increases and so does the flexural capacity of the connection. Numerical results from detailed finite-element analysis confirm the role of beam binding action enabled by the present method in satisfactorily enhancing both the strength and stiffness of shear tab connections as a gravity frame deforms laterally.
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•New method for life cycle cost (LCC) analysis of energy-efficient building presented.•Levels of seismic damage in energy-efficiency features probabilistically predicted.•Repair and ...replacement costs of damaged energy-efficiency features included in LCC.•Numerical examples of building with different energy-efficient windows provided.•Cost-effectiveness of energy-efficient building with/without seismic costs compared.
A new life cycle cost (LCC) analysis method is presented to evaluate the long-term cost-effectiveness of energy-efficiency features in buildings by accounting for the future costs associated with earthquake-induced damages in such features. Buildings situated in a seismic zone are possibly attacked by earthquakes over lifetime and their nonstructural elements such as energy-efficiency features may suffer from various levels of damage, requiring repair or replacement to restore a satisfactory level of building energy efficiency. However, existing LCC analysis methods have overlooked such earthquake-related cost, potentially leading to unreliable cost-effectiveness assessment of energy-efficient buildings. To address this problem, we propose a method to rigorously quantify the expected cumulative future cost due to the repair/replacement of earthquake-damaged energy-efficiency features and then integrate this cost into the LCC analysis. The new method is illustrated using a medium-sized office building located in a high seismic region with a Mediterranean climate. Costs associated with the initial installation as well as future energy consumption, environmental impacts, and seismic damages of two alternative types of window assembly with different levels of energy efficiency are calculated and compared. It is found that, with seismic damage cost considered, the cost-effectiveness of energy-efficiency features can be noticeably reduced and, equivalently, the payback time for building energy efficiency investment is prolonged.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•A new nonlinear static analysis for fast, reliable progressive collapse assessment.•Prediction of peak responses by balancing the external work and internal energy.•Incremental application of a ...single downward force at the column removal location.•Immediate advantages of significantly reduced computational complexity and cost.•Responses predicted with at least the same accuracy as those by pushdown analysis.
This paper presents a new nonlinear static analysis procedure for predicting the peak structural responses of a building frame upon the sudden removal of a column. Based on the pulldown analysis technique that was originally developed using the empirical dynamic increase factors, the present procedure is derived by checking the condition of energy balance between the external work done by the unbalanced gravity loads and the internal energy stored in or dissipated by the deformed frame following the column removal. In contrast to the existing energy-based pushdown analysis that needs to incrementally apply the distributed gravity loads over all directly affected bays at every floor level above the removed column, the new energy-based pulldown analysis only requires the incremental application of a single downward force at the column removal location. As a result, only a single force–displacement response curve is needed in the energy-based pulldown analysis, compared to a large number of force–displacement curves for multiple nodes along all directly affected beams above the removed column, as required in the energy-based pushdown analysis. Hence, the computational complexity and expense is significantly reduced. Taken a steel frame structure as an example, the accuracies of energy-based pulldown analysis and energy-based pushdown analysis in assessing the building potential for progressive collapse after the notional column removal are systematically compared, using the nonlinear time history analysis results as a baseline. Numerical study shows that values of key structural responses (e.g., peak vertical displacement, maximum plastic hinge rotation, peak axial forces and moments) predicted by the energy-based pulldown analysis agree generally well with those by the time history analysis and are at least as accurate as those by the energy-based pushdown analysis. Therefore, the energy-based pulldown analysis holds great promise for fast, reliable assessment of building progressive collapse potential.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Semi-rigid steel frames are often considered a cost-effective alternative to conventional fully rigid steel frames, because they use the economical partially restrained (PR) connections instead of ...the costly moment connections while performing satisfactorily under seismic loads. So far, semi-rigid steel frames have typically been designed using the traditional force-based method that is meant for the design of fully rigid steel frames. With this method, the sizing of various structural components is firstly carried out per code strength requirements and then revised iteratively to satisfy the stiffness requirements on both individual structural components and the overall frame. As a result, a designer often encounters considerable difficulty in achieving a structural solution that meets the target displacement and attains a desired yield mechanism. To address this issue, we propose a facile displacement-based method for the seismic design of semi-rigid steel frame structures by directly and explicitly relating the target displacement and deformation to the appropriate sizing of various structural components in terms of their strength, stiffness, and ductility. The new method is based on a simplified analytical semi-rigid frame model assuming that the structural plastic deformation is mainly concentrated within the PR connections while beams and columns largely remain elastic. A step-by-step procedure for implementing the new method is described and illustrated with example semi-rigid steel frame designs. The usefulness of the new method is demonstrated by comparing the target displacement and deformation values specified as a design objective with the actual values predicted by a nonlinear static pushover analysis.
•Seismic design of semi-rigid steel frame is directly based on target displacement.•Simplified analytical model assumes plastic deformation is within PR connections.•Target displacement is converted to member strength and stiffness requirements.•Step-by-step procedure is described to implement the displacement-based method.•Numerical examples are provided and results are compared with pushover analysis.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Dental cone beam computed tomography (CBCT) provides high-resolution tomographic images and has been gradually used in clinical practice. Thus, it is important to examine the amount of radiation dose ...resulting from dental CBCT examinations. In this study, we developed an in-house anthropomorphic adult head phantom to evaluate the level of effective dose. The anthropomorphic phantom was made of acrylic and filled with plaster to replace the bony tissue. The contour of the head was extracted from a set of adult computed tomography (CT) images. Different combinations of the scanning parameters of CBCT were applied. Thermoluminescent dosimeters (TLDs) were used to measure the absorbed doses at 19 locations in the head and neck regions. The effective doses measured using the proposed phantom at 65, 75, and 85kVp in the D-mode were 72.23, 100.31, and 134.29µSv, respectively. In the I-mode, the effective doses were 108.24, 190.99, and 246.48µSv, respectively. The maximum percent error between the doses measured by the proposed phantom and the Rando phantom was l4.90%. Therefore, the proposed anthropomorphic adult head phantom is applicable for assessing the radiation dose resulting from clinical dental CBCT.
•A home-made anthropomorphic adult head phantom was proposed.•The proposed phantom can be easily built with lower price than the standard Rando phantom.•The proposed phantom can be used for evaluating the effective dose during dental CBCT scanning.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
AbstractA conceptually intuitive, computationally efficient iterative procedure is formulated to optimize the member sizes of regular steel moment frames under both lateral forces and gravity loads. ...This procedure aims to maximize the interstory drifts of a steel frame while satisfying code requirements on both individual member strength and story lateral stiffness. A key premise of the present optimization method is that the process of pushing the interstory drift profile of a steel frame toward the code-specified interstory drift limit (i.e., attaining a fully drifted state) is inherently accompanied by a reduction in the total steel weight of the frame. To attain the desired fully drifted state, an iterative scheme for the story-by-story updating of the column and beam sizes is provided. At each iteration, a steel member is resized according to the worst of its strength demand-to-capacity ratio and the interstory drift demand-to-limit ratio. The iterative process continues until the total steel weight of the frame has been reduced to a satisfactory level, and both member strength and interstory drift have met the code requirements. Member sizing optimization of three example steel moment frames with varied complexities is carried out using the present iterative procedure. Numerical results show that an improved frame design can be generated within a few iterations, and that this design compares favorably with the baseline frame design that results from weight minimization by either an exhaustive enumeration or a genetic algorithm. Therefore, the present iterative procedure is an appealing tool for practical design optimization of steel frames.
Browser with Rich Internet Application (RIA) Web pages could be a powerful user interface for handling sophisticated data and applications. Then the RIA solutions would be a potential method for ...viewing and manipulating the most data generated in clinical processes, which can accomplish the main functionalities as general picture archiving and communication system (PACS) viewing systems. The aim of this study is to apply the RIA technology to present medical images. Both Digital Imaging and Communications in Medicine (DICOM) and non-DICOM data can be handled by our RIA solutions. Some clinical data that are especially difficult to present using PACS viewing systems, such as ECG waveform, pathology virtual slide microscopic image, and radiotherapy plan, are as well demonstrated. Consequently, clinicians can use browser as a unique interface for acquiring all the clinical data located in different departments and information systems. And the data could be presented appropriately and processed freely by adopting the RIA technologies.
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NUK, SBMB, SBNM, UL, UM, UPUK, VSZLJ
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