Proporciona los pasos y procedimientos para acceder al recurso Journal of Construction Engineering & Management.

Equivalent Lateral Force Method (ELF) and Response Spectrum Analysis (RSA) are the two most popular methods of seismic design of structures. This study aims to present a comparative study of the two methods using hand-calculated approach as well as computer analysis according to ASCE 7-10 Standards. The two methods have been compared in terms of base shear and story forces by analyzing various models for different number of stories and different support conditions. It was found that ELF gives conservative results in comparison to RSA. This result was more obvious in case of four-story frames. Hence, for structures of increased elevation, the analysis from ELF may not be sufficient.

The American Society of Civil Engineers (ASCE) Standard 41-06 Supplement No.1 (2007) assists engineers in modeling and evaluating the non-linear behavior of structures till collapse. Different levels of conservatism were used throughout the standard to produce modeling parameters for different structural elements, which leads to inconsistencies at the system level. Task to update current ASCE 41-06 provisions pertaining to RC structures is now handled by ACI (American Concrete Institute) committee 369 entitled “Seismic Repair and Rehabilitation”. This study is a part of ACI 369 committee’s effort. Existing provisions for non-linear analysis are re-assessed in this study for both rectangular and circular reinforced concrete columns. A database of 490 column tests was compiled for this project. Median rather than conservative estimates of non-linear modeling parameters were produced to achieve “best” estimates of structural behavior. Proposed modeling parameters show improved fit with experimental data over existing parameters. Data necessary for selection of acceptance criteria are provided. / text

No description available.

No description available.

This paper provides an assessment of the seismic performance of a code-designed buckling restrained braced frame building using the performance-based analysis procedures prescribed in ASCE 41-06. The building was designed based on the standards of the ASCE 7-05 for a typical office building located in San Francisco, CA. Nonlinear modeling parameters and acceptance criteria for buckling restrained brace components were developed to match ASCE 41-06 design standards for structural steel components, since buckling restrained braces are not currently included in ASCE 41-06. The building was evaluated using linear static, linear dynamic, nonlinear static and nonlinear dynamic analysis procedures. This study showed that the linear procedures produced more conservative results, with the building performing within the intended Life Safety limit, while the nonlinear procedures predicted that the building performed closer to the Immediate Occupancy limit for the 2/3 maximum considered earthquake hazard. These results apply to the full maximum considered earthquake hazard as well, under which the building performed within the Collapse Prevention limit in the linear analysis results and within the Life Safety limit in the nonlinear analysis results. The results of this paper will provide data for the engineering profession on the behavior of buckling restrained braced frames as well as performance based engineering as it continues to evolve.

This work stems from two different studies related to this performance assessment of seismic resistant systems. The first study compares the performance of newly developed and traditional seismic resisting systems, and the second study investigates many of the assumptions made within provisions for nonlinear response history analyses. In the first study, two innovative systems, which are hybrid buckling restrained braces and collapse prevention systems, are compared to their traditional counterparts using a combination of the FEMA P-695 and FEMA P-58 methodologies. Additionally, an innovative modeling assumption is investigated, where moment frames are evaluated with and without the lateral influence of the gravity system. Each system has a unique purpose from the perspective of performance-based earthquake engineering, and analyses focus on the all intensity levels of interest. The comparisons are presented in terms consequences, including repair costs, repair duration, number of casualties, and probability of receiving an unsafe placard, which are more meaningful to owners and other decision makers than traditional structural response parameters. The results show that these systems can significantly reduce the consequences, particularly the average repair costs, at the important intensity levels. The second study focuses on the assumptions made during proposed updates to provisions for nonlinear response history analyses. The first assumption investigated is the modeling of the gravity system's lateral influence, which can have significant effect on the system behavior and should be modeled if a more accurate representation of the behavior is needed. The influence of residual drifts on the proximity to collapse is determined, and this work concludes that a residual drift check is unnecessary if the only limit state of interest is collapse prevention. This study also finds that spectrally matched ground motions should cautiously be used for near-field structures. The effects of nonlinear accidental torsion are also examined in detail and are determined to have a significant effect on the inelastic behavior of the analyzed structure. The final investigation in this study shows that even if a structure is designed per ASCE 7, it may not have the assumed probability of collapse under the maximum considered earthquake when analyzed using FEMA P-695. / Ph. D.

Seismic response of free standing un-anchored objects is required to be studied in Nuclear Power Plants (NPPs) for their own integrity and potential interaction with the surrounding seismically qualified safety systems. Rocking response of a rigid body subject to seismic excitation is not very well covered in the nuclear standards except for an approximate method given in ASCE 43-05 where the design basis earthquake (DBE) response spectrum for the NPPs given in the United States Nuclear Regulatory Commission (USNRC) regulatory guide 1.60 (known as NBK spectrum developed by Newmark, Blume and Kapur (1973)) is considered as seismic input. This study evaluates existing seismic design criteria for unanchored objects that are vulnerable to rocking and overturning inside nuclear power plants. The original work of Newmark et al (1973) is revisited in order to obtain the NBK spectra at unusual damping (8.4% for example), required in order to follow the ASCE 43-05 method. Eight earthquake records are selected from Newmark et al (1973) with varying Peak Ground Accelerations (PGAs) representing strong to moderate ground motions. Rocking response of rigid bodies to various earthquakes is determined by three methods: 1. The ASCE 43-05 method utilizing the NBK spectrum, 2. The ASCE 43-05 method utilizing the response spectrum of the earthquake records, and 3. solving the equations of motion of a rigid body for the earthquake records. Rocking spectra by these three methods created for eight earthquake records are compared with one another. It is concluded that the ASCE 43-05 method provides inaccurate predictions of the response. Considering the significant level of effort required to implement the ASCE 43-05 method, its inherent contradictions, and its inconsistent conservatism in estimating the seismic demands on rocking objects, it is concluded that the results obtained by nonlinear time history analysis are more accurate, reliable and less time consuming than those by the ASCE 43-05 method. The use of nonlinear dynamic analysis is recommended to obtain the pure planar rocking response of unanchored objects in nuclear facilities. / Thesis / Master of Applied Science (MASc)

Greenroof systems have been shown to be an environmentally friendly alternative based on various factors; such as, reduced lifecycle cost, improved air quality, ambient temperature reduction, stormwater management credit, sustainability and preservation of the environment. Recent research studies attempt to determine the construction methods of an ideal greenroof for environmental purposes, yet there is an absence of standards for the best design required to achieve acceptable structural performance and sustainability under wind loads. As a result, there is a need to document the effectiveness of greenroofs under high wind events by addressing the following questions: Do winds have an effect on greenroof material loss? Do greenroof materials modify local pressure conditions that would need a modification to current design codes? Does the level of vegetation establishment affect the material loss and pressure distribution? This thesis first focuses on vegetated greenroof construction techniques and issues along with some of the most recent studies conducted by UCF researchers. Then, the literature focuses on wind uplift of vegetated roofs constructed using different wind erosion control methods with respect to vegetation cover, geosynthetic liners, and wind breaks. As part of this research, two monitoring systems with a grid of very low differential pressure transducers and a high speed anemometer were designed and implemented on the East and West coasts of Florida to collect data for the pressure distribution across the greenroofs in relation to wind direction and speed. In addition to this, the design of this monitoring system with specific information about the sensing and data acquisition systems is presented. Subsequently, the analysis of the monitoring data compares the peak wind gusts for each time interval to their corresponding pressure measurement to obtain pressure coefficients identified at each pressure node on the roof. Based on this analysis, pressure changes for hurricane speed winds are predicted to have an overall average uplift pressure envelope within ASCE Code 7-05 design standards with vegetation cover enhancing sustainability under wind events. For future studies, controlled field investigations to reduce in situ limitations due to natural climatic conditions as well as long term monitoring are discussed as recommended studies for the evaluation of wind effects.

No description available.