Showing 25–36 of 649 results
CYCLIC BEHAVIOUR OF STEEL BRACED FRAMES HAVING SHEAR PANEL SYSTEM
Seismic resisting stرایگان!
Seismic resisting structures are expected to maintain adequate stiffness during frequent but moderate excitations on one hand, and to dissipate a large amount of energy under damaging earthquakes on the other hand. In this paper, a relatively new seismic resisting structural system, which satisfies stiffness and energy dissipation requirements simultaneously, is numerically investigated using nonlinear finite element analysis procedure. In this system, earthquake energy is dissipated through large inelastic deformation occurred within a shear panel. The shear panel acts as a ductile link beam connecting braces to the floor beam. This paper aims to find out key issues influencing cyclic behaviour of frames braced by Shear Panel System (SPS), like Cross-sectional properties of SPS and link length. The results indicate that shear panel length significantly affects cyclic performance of this system. Use of shorter links results in more stiffness and at the same time more stable hysteretic behaviour and energy dissipation capacity. Finally, the paper presents a mathematical model to evaluate lateral stiffness of braced frames braced having SPS.
Deploying Wireless Sensor Networks with Fault-Tolerance for Structural Health Monitoring
Structural health moرایگان!
Structural health monitoring (SHM) systems are implemented for structures(e.g., bridges, buildings) to monitor their operations and health status. Wireless sensor networks (WSNs) are becoming an enabling technology for SHM applications that are more prevalent and more easily deployable than traditional wired networks. However, SHM brings new challenges to WSNs: engineering-driven optimal deployment, a large volume of data, sophisticated computing, and so forth. In this paper, we address two important challenges: sensor deployment and decentralized computing. We propose a solution, to deploy wireless sensors at strategic locations to achieve the best estimates of structural health (e.g., damage) by following the widely used wired sensor system deployment approach from civil/structural engineering. We found that faults (caused by communication errors, unstable connectivity, sensor faults, etc.) in such a deployed WSN greatly affect the performance of SHM. To make the WSN resilient to the faults, we present an approach, called FTSHM (fault-tolerance in SHM), to repair the WSN and guarantee a specified degree of fault tolerance. FTSHM searches the repairing points in clusters in a distributed manner, and places a set of backup sensors at those points in such a way that still satisfies the engineering requirements. FTSHM also includes an SHM algorithm suitable for decentralized computing in the energy-constrained WSN, with the objective of guaranteeing that the WSN for SHM remains connected in the event of a fault, thus prolonging the WSN lifetime under connectivity and data delivery constraints. We demonstrate the advantages of FTSHM through extensive simulations and real experimental settings on a physical structure.
Determining the Low-Temperature Fracture Toughness of Asphalt Mixtures
There has been a susرایگان!
There has been a sustained effort in applying fracture mechanics concepts to crack formation and propagation in bituminous pavement materials. Adequate fracture resistance is an essential requirement for asphalt pavements built in the northern part of the US and Canada for which the prevailing failure mode is cracking due to low-temperature shrinkage stresses. The current Superpave specifications address this issue mainly through the use of strength tests on unnotched (smooth boundary) specimens. However, recent studies have shown the limitations of this approach and have suggested that fracture mechanics concepts, based on tests performed on notched samples, should be employed instead. Research in progress at University of Minnesota investigates the use of fracture mechanics principles to determine the low- temperature fracture properties of asphalt mixtures. This paper presents a testing protocol that allows obtaining multiple measurements of fracture toughness as a function of crack propagation based on the compliance method to measure crack length. An increase in fracture toughness with crack length is observed, which is consistent with the behavior displayed by other brittle materials. The plateau of the curves may be representative of the asphalt concrete resistance to fracture because the initial values can be significantly influenced by the presence of the inelastic zone at the crack tip
Ductility Demand Distribution of Asymmetric Multi-Story R/C Buildings
To evaluate the infl...رایگان!
To evaluate the influences of the number of stories on the torsional response and ductility demand distribution in the plan and the height of plan asymmetric RC dual lateral load resistant multi-story buildings, three categories of structural models that contain 8-, 14- nd 20-stories buildings (with the wide range of eccentricity values) are subjected to an assemblage of ordinary and near-fault ground motions. The approach of modeling has been used, is more accurate for multi-storey R/C structures, because it redefines the stiffness from the strength in each time step. According to the findings, the torsional effects, decreases for high-rise structures where the lateral natural period increases
Economic Sustainability of Concrete Pavements
Economic evaluation of transport infrastructure is as important as its technical and structural design: often only initial construction costs are calculated to evaluate economic project sustainability. Instead forgetting maintenance costs exposes society to unacceptable risks of expensive decisions. Road pavements design and construction solutions affect maintenance works during service life, which not only entail economical and financial expenditures but also damage service regularity for users. Distress pavement analysis can contribute to find the financially most advantageous solution. This paper shows a computer program defined to analyze structural, functional and financial characteristics of concrete pavements.
Effect of Number of Contributed Modes on Accuracy of MultiModal Pushover Seismic Analysis of Irregular Frames
One of well-establisرایگان!
One of well-established static procedures for seismic evaluation and design of building structures in the equivalent nonlinear static procedures is Modal Pushover Analysis developed by Chopra and Goel (2002). For evaluation of effect of number of contributed modes on the accuracy of MPA procedure, 22 vertically irregular 5-story steel moment resisting frames are considered that each irregular frame is designed to represent low and high values of response reduction factor (R). Many nonlinear time histories and static pushover analyses are performed and the results of nonlinear static analyses are compared with the results for nonlinear dynamic analyses to evaluate the accuracy and conservatism of MPA for predicting target displacement, base shear, and story drifts.
Effect of Steel Plate Jacketing of Columns in Seismic Behavior of Concrete Beam-Column Connections
Design philosophy ofرایگان!
Design philosophy of having weak beam – strong column is recommended almost in all design codes. But in some ases, in prior buildings, this philosophy is ignored. In these structures, during major earthquakes, failure mechanism would begin from columns leading to sever damages. To avoid this event, column in the connection zone must be strengthened to conduct the plastic zone to the beams. There is several ways for strengthening concrete columns and one of the efficient ways is using steel plates surrounding column in the critical zone. In this paper, using steel plates for seismic upgrading of Concrete Beam-Column connections has been investigated numerically. Effect of plate thickness, length and beam-column dimensions is taken into account. Some empirical results are used to verify the finite element approach. Analyses are conducted with the use of some modeling methods including various geometrical models and material behaviors. The results from various methods are compared and the suitable model is proposed
Effects of Circular Opening Dimensions on the Behavior of Steel Plate Shear Walls (SPSWs)
In recent years ther...رایگان!
In recent years there is a developing attention to steel plate shear walls (SPSWs) thanks to their proper function exposing to lateral wind and earthquake loads. Furthermore, their application in steel and concrete structures in order to strengthening them has raised a lot of focus upon. In some cases existence of opening is unavoidable due to architectural reasons or installed heating and cooling systems on the walls. That leads to a decrease in capacity and improper functioning of these systems that also results in an intense variation in inplane stress distribution. In this paper impact of circular opening dimensions on behavior of steel plate shear walls has been closely studied. On this purpose using ABAQUS finite element method a nonlinear analysis has been conducted considering geometrical and material nonlinearity in the models. Analyzed models indicate that the reduction factor (1-D/H)S and (1-D/H) respectively for resistance value and stiffness value predict lower error versus the increases in opening diameter
Environmental, Economic, and Social Implications of Highway Concrete Rehabilitation Alternatives
Currently, there isرایگان!
Currently, there is no comprehensive benchmark of life-cycle assessment for the rigid pavement alternatives for highway rehabilitation. To fill this gap, the major objective of this study is to investigate the environmental, economic, and social impacts of the three most widely adopted rigid pavement choices through a life-cycle assessment approach with custom-built economic input-output life-cycle assessment (EIO-LCA) models. Quantity takeoffs were performed for each alternative assuming a 1-lane-km highway rehabilitation. Subsequently, the construction costs of each alternative were computed in order to determine the present values for a life span of 50 years, while at the same time accounting for a different life expectancy for each pavement rehabilitation strategy. The present values were then incorporated into a corresponding EIO-LCA model. The results clearly indicate that continuously reinforced concrete pavement (CRCP) is the most sustainable choice and much preferable to the other alternatives for minimizing negative environmental, economic and social impacts from the life-cycle perspective. This finding champions a wider adoption of CRCP for future sustainable transportation infrastructure development projects, as CRCP’s relatively high initial construction cost can be recouped by long-term sustained benefits. The results and findings of this study can serve as a solid foundation for industry practitioners and decision-makers to make better-informed project decisions when choosing the most sustainable pavement alternatives from a life-cycle perspective. DOI: 10.1061/(ASCE)CO.1943-7862.0001063. © 2015 American Society of Civil Engineers.
Evaluation of Base Shear Absorption of Combined System; RC Frame & Precast 3d Panels with Irregularities in Vertical
The current study inرایگان!
The current study investigates the base shear absorption of combined systems, RC frame pre-cast 3D wall sandwich panels in both linear and non-linear material properties. The seismic behavior of building constructed by 3D panels is studied using numerical approach finite element method. The obtained results are compared with regular bending RC frames, complete box type sandwich wall panels system, and present the differences of behavior and absorbance in each system and also the variation of vertical stiffness on structural response is examined. The material nonlinearities simulated with drucker-prager and von-misses failure criteria. The validation of FEM analysis is test with those obtained through experimental
Evaluation of Horizontal Seismic Hazard of ABADE, Iran
This paper presentsرایگان!
This paper presents probabilistic horizontal seismic hazard assessment of Abade, Iran. It displays the probabilistic estimate of Peak Ground Horizontal Acceleration (PGHA) for the return period of 475 and 2475 years. The output of the probabilistic seismic hazard analysis is based on peak ground acceleration (PGA), which is the most common criterion in designing of buildings. A catalogue of seismic events that includes both historical and instrumental events was developed and covering the period from 840 to 2007 is used. he seismic sources that affect the hazard in Abade were identified within the radius of 150 km and the recurrence relationships of these sources were generated by Kijko and Sellevoll . Finally four maps have been prepared to indicate the earthquake hazard of Abade in the form of iso-acceleration contour lines for different hazard levels by using SEISRISK III
Experimental Investigation of Time-Dependent Effect on Shear Strength Parameters of Sand–Geotextile Interface
The time-dependent bرایگان!
The time-dependent behavior of soils has been investigated extensively using one-dimensional and triaxial tests. The phenomena associated with time effects in soils are creep, relaxation, strain rate and rearrangement effects. The engineering properties of soil are often improved significantly with the time elapse. The objective of this paper is to investigate the time-dependent effect on the shear strength parameters of sand–geosynthetic interface using large direct shear test apparatus. For this purpose, the geotextile layer has been adhered gently on a piece of wood with a thickness such that a half of the shear test box has been occupied. The other half of the box has been filled with the sand and the test has been performed. Three normal stresses of 30, 45, and 60 kPa have been applied in all tests. The shear stress has subsequently been applied in different times to the failure stage. In all tests, the shearing velocity has been kept the same. The results of these experiments show that the stiffness and friction angle of the dry sand– geotextile interface increases up to 12.6% and 3.9% at 720 minutes after the sample is poured in the mold