Showing 37–48 of 649 results
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FFECTS OF SOIL-STRUCTURE INTERACTION AND BASE ISOLATION ON SEISMIC PERFORMANCE OF FOUNDATION SOILS
This study primarily
رایگان!This study primarily focuses on structural induced liquefaction potential. Moreover, the effect of base isolation systems on both structural performance and liquefaction potential was studied including the soil-structure interaction effects. Four different types of structures and three different types of local sites were analyzed under two different input ground motions. It was mainly found that, depending on the structural type and for a certain depth, the liquefaction potential could be higher under the structure than the one in the free field. Besides decreasing the story drifts and shear forces in the structure, base isolation systems were very effective for decreasing liquefaction potential in the soil. It was also observed that soil-structure interaction leads to very significant changes in the response spectra.
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Flexibility based method for the extent of damage in degrading bridge structures after in-service loading
This paper presents ...
رایگان!This paper presents a method to identify damage in bridge structures based on the flexibility matrices in the modal strain space. In the tudy by the Ritz vectors extracted from flexibility matrix, the damage is identified. The localization approach is applied to low levels of damage on the prestressed concrete girder of simply supported bridge, with a focus on using a small number of sensors and only the fundamental mode of vibration. The validity of the method is also demonstrated using experimental modal data of a plate girder from I-40 Bridge over the Rio Grande. The predictions were found to closely match the actual response of the bridges. The proposed method can detect the damage in bridge structures using a limited number of sensors and vibration modes
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Foundation size effect on modulus of sub grade reaction on Sandy soils
Winkler model is one...
رایگان!Winkler model is one of the most popular models in determining the modulus of sub grade reaction. In this model, the sub grade soil is assumed to behave like infinite number of linear elastic springs. The stiffness of these springs is named as the modulus of sub grade reaction. This modulus is dependant to some parameters like soil type, size, shape, depth and type of foundation. The direct method for estimating the modulus of sub grade reaction is plate load test that is done with 30-100 cm diameter circular plate or equivalent rectangular plate. Afterward, we have to extrapolate the test value for exact foundation. In the practical design procedure, Terzaghi’s equation is usually used to determine the modulus of sub grade reaction for exact foundation, but there are some uncertainties in utilizing such equation. In this paper the size effect of foundation on sandy sub grade with use of finite element software (Plaxis 8.2) is proposed to investigate the validation of Terzaghi’s formula on determination of sub grade reaction modulus. Also the comparison between Vesic’s equation, Terzaghi’s one and obtained results are presented
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Geomorphologic hazards for Vanyar Dam with emphasis on the reactivation of Tabriz fault, northwest Iran
Shahid Madani or Van
رایگان!Shahid Madani or Vanyar Dam is being construction on Aji Cahy River, to the north of Tabriz. It has been built on the upper red formation of Miocene. This lithology generally consists of sandstones, conglomerates, clays, and gypsum. Salt domes are also located underneath the reservoir area behind the dam. The slopes beside the reservoir are not stable. Unexpected events, such as subsidence, could occur after the reservoir is filled causing destruction to infrastructure. However, the most serious event could be the infiltration of water into the Tabriz fault. This fault has not been reactivated for over 220 years and it is thought that the infiltration of water from the reservoir could cause the two sides of the fault plane to move. It is thought that the displacement of the fault could cause an earthquake of more than 6.5 on the Richter scale. To try and prevent this fault reactivating, filling of reservoir is proposed to be undertaken gradually.
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Impact of Green Building Design and Construction on Worker Safety and Health
Sustainable, or “gre
رایگان!Sustainable, or “green,” rating systems, such as the United States Green Building Council’s Leadership in Energy and Environmental Design LEED, are leading to changes in the way owners, designers, and contractors approach the design, construction, and operation of buildings. The processes and features included in green design and construction may have positive and/or negative impacts on construction worker safety and health. This paper presents the findings of a research study of the impact of green building design and construction practices on construction worker safety and health. Occupational Safety and Health Administration OSHA recordable and lost time injury and illness data from green projects as identified by LEED and from nongreen projects was collected through a structured questionnaire survey. The data collected was analyzed to test for the presence of a difference in OSHA recordable incident rates RIRs and lost time case rates LTCRs between green and nongreen projects. It was found that there was suggestive, but inconclusive evidence of a statistically significant difference in the RIRs of the green and nongreen building projects included in the study. No statistically significant difference was found between the LTCRs for the green and nongreen projects included in the study. The study findings provide valuable information to the construction industry for the purposes of project safety planning and the assessment of safety and health on projects.
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Inelastic large deflection analysis of structural steel members under cyclic loading
The present paper is
رایگان!The present paper is concerned with the cyclic inelastic large deflection analysis of structural steel members, such as pin-ended columns and fixed-ended tubular beam-columns of strut type. An elastoplastic finite element formulation for beam-columns, accounting for both the material and geometrical nonlinearities, was developed and implemented in the computer program FEAP used in the analysis. The geometrical nonlinearity is considered using the modified approximate updated Lagrangian description of motion. The two-surface plasticity model, recently developed by the authors, is employed for material nonlinearity. The model accounts for the important cyclic characteristics of structural steel, even within the yield plateau, such as, the decrease and disappearance of the yield plateau, reduction of the elastic range and cyclic strain hardening. The cyclic elastoplastic performance of the formulation was found to be good when compared with the experimental results as well as the results obtained from other material models.
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INFLUENCE OF FIBER REINFORCEMENT ON TRIAXIAL SHEAR BEHAVIOR OF CEMENTED SANDY SOILS
A number of triaxial
رایگان!A number of triaxial tests were conducted for evaluation of randomly distributed fiber reinforcement effects on the behavior of cemented sand. Cemented samples were prepared by addition of Portland cement up to 3% by weight and were cured for about seven days after mixture. Polypropylene fibers with a length of 12 mm were added and mixed in three different weight percentages of 0%, 0.5%, 1%. Specimens were compacted in relative densities of 50% and 70%. Consolidated drained compression triaxial tests were performed under confinements of 100, 300 and 00 kPa. Tests results indicated that addition of polypropylene fiber to cemented sandy soils increases peak and residual strength. However, ultimate dilation decreases with enhancement of fiber content in cemented soil
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Influence of the Type of Bracing System on Dynamic Response of Steel Frames
This paper presents
رایگان!This paper presents an overview of comparing the dynamic response of steel braced frames subjected to seismic loadings. To perform this study, four types of bracing systems including X-bracing, Diagonal bracing, chevron-inverted V and chevron-inverted V type EBF, with 3, 6, 9 and 12- story frames are modeled and designed in accordance with AISC-ASD 89 code. To compare the dynamic characteristics of considered structural systems, nonlinear static analysis was conducted. The parameters which are evaluated and compared in these models are consisted of economical viewpoint with evaluating the weight of the structures based on steel used, the maximum roof displacement, behavior factor, ductility and the energy absorption. Results indicate that response modification factors (R) have different values depending on the brace configuration type and the building height. However, EBFs possess the highest amount of R factors, it seems in order to obtain the light weight structure, as well as the high energy absorption capacity, the best solution among compared bracing systems, is to apply the Inverted-chevron V bracing systems in steel frames. Obtained results are presented in relative diagrams and tables.
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Innovative Crisis Management in Construction: Approaches and the Process
Crisis management is
رایگان!Crisis management is a process that includes catching and evaluating crisis signals and needs to take and implement necessary precautions in order to overcome a crisis with a minimal damage. Detecting the early warning signals of a crisis contributes firms to hinder the occurrence of the crisis and to survive without huge financial losses. Other factors that contribute construction firms to survive with zero defect can be listed as follows: (i) catching indirect signals before a crisis, (ii) developing proactive methods to defend themselves against the crisis by means of these signals, (iii) taking the crisis under control, (iv) taking required measures after the crisis for the recovery of the firm, and lastly (v) recording the lessons learned from the crisis. Construction firms that can successfully manage a crisis can quit it with a minimum loss and can expand their market shares after the crisis. In other words, firms that can escape from a crisis with zero or minimum damage may strategically have competitive advantages over existing rivals. Considering all these issues, this study describes the concept of crisis management in terms of the construction industry and introduces related objectives and characteristics. In addition, both innovative crisis management approaches and the corresponding process were discussed in detail from the perspective of construction companies. In fact, this is a virgin area in the construction management literature and thus can contribute to the creative and innovative management of companies under potential crises in micro and macro levels. Consequently, this study attempts to reveal how construction firms can manage crises better and turn to their former positions in the short term through innovation-based means.
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Innovative Crisis Management in Construction: Approaches and the Process
Crisis management is
رایگان!Crisis management is a process that includes catching and evaluating crisis signals and needs to take and implement necessary precautions in order to overcome a crisis with a minimal damage. Detecting the early warning signals of a crisis contributes firms to hinder the occurrence of the crisis and to survive without huge financial losses. Other factors that contribute construction firms to survive with zero defect can be listed as follows: (i) catching indirect signals before a crisis, (ii) developing proactive methods to defend themselves against the crisis by means of these signals, (iii) taking the crisis under control, (iv) taking required measures after the crisis for the recovery of the firm, and lastly (v) recording the lessons learned from the crisis. Construction firms that can successfully manage a crisis can quit it with a minimum loss and can expand their market shares after the crisis. In other words, firms that can escape from a crisis with zero or minimum damage may strategically have competitive advantages over existing rivals. Considering all these issues, this study describes the concept of crisis management in terms of the construction industry and introduces related objectives and characteristics. In addition, both innovative crisis management approaches and the corresponding process were discussed in detail from the perspective of construction companies. In fact, this is a virgin area in the construction management literature and thus can contribute to the creative and innovative management of companies under potential crises in micro and macro levels. Consequently, this study attempts to reveal how construction firms can manage crises better and turn to their former positions in the short term through innovation-based means.
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Investigation of the cracking of CFRD face plates
The primary goal of
رایگان!The primary goal of this study was to examine the cracking behavior of the face plate of a CFRD over its life cycle. Analyses of the construction stage, impounding, long-term deformation and earthquake loading were conducted in sequential phases using a 2-D plane-strain model with the appropriate nonlinear constitutive relationships for the dam constituents. The state of stress and the cracking behavior of the plate were found to be substantially different in the short and long term. Earthquake loading appears to be a critical load condition for the face plate; cracking increased significantly after ground shaking.
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Investigation of the cracking of CFRD face plates
The primary goal of
رایگان!The primary goal of this study was to examine the cracking behavior of the face plate of a CFRD over its life cycle. Analyses of the construction stage, impounding, long-term deformation and earthquake loading were conducted in sequential phases using a 2-D plane-strain model with the appropriate nonlinear constitutive relationships for the dam constituents. The state of stress and the cracking behavior of the plate were found to be substantially different in the short and long term. Earthquake loading appears to be a critical load condition for the face plate; cracking increased significantly after ground shaking.