Civil Engineering Infrastructures Journal
Year:2010 | Volume:44 | Issue:4|Papers Count:13

The object of this paper is to investigate the effects of vertical component of the ground motion on the behavior of isolated steel Buildings. For this purpose, a four-story building with different eccentricities is modeled. Three elastomeric isolators with different vibration periods and damping ratios as well as three different records are used to compare the behavior of the structure under the action of three and two components of the ground motion. In comparison with other works the forces of elements and influential parameters such as local uplift of isolator units has been investigated. The results show the considerable effect of the vertical component on axial forces (about 2 times) and local uplift of the columns. Also, the ratio of the vertical peak ground acceleration to the horizontal peak ground acceleration is found to be another influential parameter. Besides, the results show the deficiency of the international codes such as IBC or NEHRP in not considering the importance of the vertical component of the ground motion on the isolated structures as it has been already considered for the non-isolated ones. Because, it causes a fault in calculating the axial force of columns up to 2 times in motions with strong vertical component and about 5 percent in moderate ones.

This research aims to ductility demand survey on concrete column strengthened with CFRP laminates. Therefore, firstly the main definitions and the review of the previous researches have been described. The behavior of concrete, FRP and reinforcements have been implemented in software computer program. Then, the analytical results has verified after considering and comparing with experimental outcomes. After calibration the software results with presented results by OZCAN et al, the effect of length and thickness wrapping on displacement ductility and rotational capacity of column has been considered. In this way, these columns without FRP, one and two layers FRP wrapping with different lengths have been modeled by ABAQUS as finite elements software. For each column the amount of strain in different location in CFRP material, have been created. The base shear-displacement curve at the end of column and the displacement ductility of columns has been examined. Moreover, the amount of curvature in different location across the length of column and also moment at the end of column has obtained. The obtained results have been compared with some analytical equations. Then the length of plastic hinge and the created rotation at the end of column have been calculated and the effect of length and thickness of CFRP wrapping have also been examined on rotational capacity of the column. Furthermore, in order to consider the effect of length and thickness of wrapping on seismic performance of columns, based on ATC40 method for estimate of the performance point, spectrum capacity of columns and spectrum seismic demand have been calculated. The performance point of columns have obtained by changing of the spectrum seismic demand curve and capacity to spectrum ADRS coordinates, using collision of these two curves. In this study also the acceptance criteria for nonlinear procedures-reinforced concrete columns wrapping with CFRP for different length and thickness of wrapping, based on analytical results of the amount of dissipated energy in each column has been evaluated, In addition, the maximum plastic rotation angle of the columns has been calculated.

In this study in order to understand the flow pattern in river lateral intakes, numerical simulation of the flow in a rectangular open channel using FLUENT software has been carried out. The velocity field at different sections near the surface of water was obtained using different turbulent models such as Standard k-e, k-w and RSM which then were compared with experimental datum. It was found that abandoning the isotropic eddy-viscosity hypothesis, the RSM accounts for the effects of streamline curvature and swirl in a more rigorous manner than other models. In a parametric study for an intake with different width ratios in a 900 junction and also for an intake with different angles of deflection, the effects of important variables such as Froude number and discharge ratio on the dimensions of separation zone using RSM model were investigated. This paper introduces different relations between dimensions of separated zone in the intake and mentioned variables. It was found that the size and location of the separation zone is very much dependent on the discharge ratio. In all cases, the results showed that an increase in the discharge ratio causes shortening and narrowing of the separation zone. For a constant discharge ratio, by increasing the channel width ratio or angle of deflection, separation zone occurs closer to the entrance.

Self-consolidating concrete (SCC) is a relatively new approach to making concrete, and it is characterized by its high flowability and resistance to aggregate segregation in the plastic state. A total of 3 beams were tested in this experimental investigation on the flexural ductility of reinforced concrete beams made with self-consolidating concrete. The beams were made from concrete having average compressive strength of 30 MPa and reinforcement ratio in the range of 0.15-1.38. Three self-consolidating reinforced concrete beams with different percentage of and constant amount of were cast and incrementally loaded under bending. During the test, the strains on the concrete middle face and on the tension and compression bars as well as the deflection at different points of the span length were measured up to failure. This paper compares the ductility of reinforced beams cast with SCC concrete to the theoretical calculations based on two codes (ACI, CSA) recommended for the reinforced concrete members that vibrated into place to ensure proper filling and consolidation. Based on the results obtained, effect of increasing tension reinforcement on the curvature and displacement ductility of the self-consolidating concrete reinforced members is more deeply reviewed. Comparisons between theoretical and experimental results are also reported here. Generally, it was concluded that, self-consolidating reinforced concrete beams yielded greater ductility as opposed to the theoretical calculations based on two codes (ACI, CSA) recommended on conventional reinforced concrete beams.

In construction of concrete floors, parts of the formwork are sometimes left in place as permanent structural elements. This is to achieve a more straightforward installation procedure and to minimize the future under deck form removal. The present research work deals with, an innovative floor system consisting of hollow-tiles and steel joists. In a hollow-tile floor system, gravity loads are transferred by the slab sitting on top of the blocks to the one way joist and then to the main beams. With the proposed new system the width of the hollow block is doubled so, it is relatively lighter than an ordinary hollow-tile floor system. The joists height is slightly bigger than that in an ordinary hollow-tile floor system, however, the hollow block height remains the same. Thin plastofoams sheets are placed on top of the blocks to fill the gap. During the construction, the fresh concrete weight is carried by temporary vertical posts. After removal of temporary posts, the service loads are transferred to the T beams. This paper provides details for the application of the proposed new floor system in a steel frame building under gravity and quasi static earthquake loading. Various spans and floor thicknesses have been examined and the details are presented.

In Iran, for Column Design, Double I shape Section is used due to lack of IPB profile. Double I shape column performance is ambiguous in existing steel structures, especially when subjected to seismic loading. In this paper, double I shape column behavior is evaluated with 3D nonlinear analyses. Monotonic behavior of 6 specimens and hysteretic behavior of other six specimens have been simulated. Half of specimens have been welded ordinarily simulating constructional habit of Iranian site welding and six other specimens have been welded ideally with complete manner. Finally behavior of two groups of specimens has been compared in the view of the following parameters such as bending and axial strength, stress concentration and collapse mechanism.

This paper aims to study the possible use of micro tremor measurements for determination of shear wave velocity (Vs) profile of sedimentary deposits. For this purpose a series of micro tremor measurements have been conducted in Bam city (southeast of Iran). Micro tremor measurements included both one-point and array observations. The F-K spectrum analysis of micro tremors was used for determination of dispersion characteristics of micro tremors. Shear wave velocity profiles were then determined by using an inversion process. Ultimately, inverted Vs profiles were compared with other available Vs data in Bam city. The inverted profiles were reasonably in agreement with results of seismic refraction and down-hole methods. This shows that micro tremor array measurements are useful as a simple and economical method for Vs profiling. In addition, it was revealed that micro tremor method is capable of detecting the probable soft layer that underlies a stiff layer which seismic refraction cannot resolve.

Worldwide use of portable falling weight deflectometer (PFWD) for construction quality control of earthworks and unbound pavement layers and their stiffness determination is increasing rapidly. However there are still many unknown factors related to application of PFWD, precision of the test results that may affect the PFWD data quality and it is necessary to identify them. In this research, field testing was carried out on different unbound base and sub-base layers on several highway construction sites in Tehran. In addition, a laboratory testing box was built in which several layers of unbound materials were compacted using a portable vibrating compactor. The stiffness moduli of the compacted layers were determined using PFWD (TML model Japan). Then, factors affecting PFWD measurements such as drop weight, drop height, plate diameter, plate-surface contact, and distances of extra geophones were investigated. The results showed that the PFWD moduli increased with increasing drop weight for the considered values and a model was presented for prediction of PFWD stiffness modulus through increasing of the drop weight. But the effect of drop height on PFWD moduli was not significant. It was found that the E0 moduli from the 100 mm loading plate were about 1.85 times higher than those from the 300 mm loading plate. Also, it was shown that the plate-surface contact was important in PFWD results. Finally, distances of extra geophones were discussed and it was found that they don't have any important effect on upper layer moduli.

Structures design in order to make them resistant against earthquake is one of the important structural subjects. According to this point that enhancing seismic science structural behavior and access to different technology the attention of designers has been more than before. Different seismic regulations try to control the damages to structures and become more assure about the structural seismic function. For this reason 20, 25 story moment frames with 3, 7 bays were analyzed time history non-linear dynamic and by changing the kind of brace in height suitable height for changing the kind of brace was suggested. In bracing changes, X braces and chevron braces has been investigated so that quake recommendation was used about down level stories stiffness against up level stories stiffness. At last this result was achieved that changing the kind of brace system in certain height can be effective on improving seismic behavior of structure. This specified level is related to number of stories or number of spasm or kind of earthquakes records, for instances in a 2 stories structure by alternating the third V bracing maximum story drift angle demand exhibits 75 percent of reduction and in a 25 stories structure by alternating the third V bracing, we see the lowest amount in the maximum local rotation demand.

Punching shear strength frequently governs the failure of slab-column connections. In general, the ultimate punching shear capacity of flat slabs can be increased by using thick slabs, drop panels, capitals, or shear reinforcement. In recent decades, steel fiber concrete has been also used to enhance the punching shear strength of flat plates and slabs. Concrete structures must be retrofitted and rehabilitated when the concrete has deteriorated or the reinforcing steel has been severely corroded. The use of fiber-reinforced polymer (FRP) is an innovative technology to strengthen concrete structures. In this paper, punching shear strengthening of flat slabs using Carbon Fiber Reinforced Polymer (CFRP) sheets is studied. Ten specimens of reinforced concrete slabs with the dimensions of 1000*1000*100 mm with different compressive strengths were manufactured and tested. Eight of them were strengthened by CFRP sheets and the others were kept as control specimens. The width of CFRP sheets varied in different specimens. The CFRP sheets were located at the tension side of the slabs in two perpendicular directions. Loading of slabs was applied downward using a hydraulic Jack. In the tests, the applied load and the displacement of specimens were measured using a computer aided data acquisition system. Based on the result of this experimental investigation, it can be concluded that the use of CFRP sheet increases the flexural stiffness and significantly improves the punching shear strength of slabs. The test results were compared with the equations proposed by ACI 318 and BS 8110 Codes. The ACI Code underestimates the punching shear strength of slabs and this underestimation becomes more pronounced with the increase in the flexural reinforcement. The BS 8110 Code appropriately accounts for the effect of flexural reinforcement on punching shear strength of slabs. However, for the strengthened slabs, an equivalent reinforcement ratio should be used to include the effect of both steel and CFRP flexural reinforcement. Based on the test results and code equations, new equations were proposed. It is shown that the proposed equations predict the punching shear strength of reinforced slabs with good accuracy.

Various equivalent nonlinear static analysis procedures have recently been introduced for seismic assessment of tall buildings. Here, iterative linear equivalent method is proposed for seismic analysis of concrete dams. Regarding important differences between the behavior of concrete dams and high-rise buildings, basic concepts and main steps of this analysis technique are developed to make it applicable for this kind of structures. In comparison with well-known push-over analysis, independency of the results from the lateral load pattern is one of the main advantages of this method. Other important achievements contain: estimating structure's damping and considering the interaction between water, structure and foundation. The proposed method is implemented and verified for Pine Flat dam which shows acceptable results.

The location of a power plant affects both the expenses and the efficiency of the energy generation and transmission. A GIS can be used to integrate the data related to the predefined criteria in order to select the optimum locations. The goal of this study is to use the spatial analysis capabilities of GIS along with fuzzy logic theory to the site selection of gas power plants. First, the effecting spatial factors are identified and their relative importance in the site selection of the power plants is defined. Regarding both fuzzy and Boolean models, proper factor maps were generated for the study area, which is located in Fars province, Iran. These two models were used in two different stages of the study. First, the locations with strict limitations for the establishment of the plants were identified and removed using Boolean logic and binary factor maps. Then, for all the remaining permitted areas, the general suitability was calculated using fuzzy logic operators. In the fuzzy model, taking into account the type of interactions between different factors and the types of available data, two different membership functions were considered. These are the multiple linear and the step-wise constant functions. Various inference networks were designed, on the basis of different view-points regarding the combination of factors. Considering these view-points and using fuzzy operators, the data were integrated and the suitable locations were selected and ranked accordingly. Finally, the locations extracted from two inference networks were compared. These two location sets covered 0.18 and 0.35 percent of the study area. Most of the selected areas in both cases were in the highly populated township of Fasa. This can be mainly attributed to high energy demand and consumption of this township and the high weight given to this factor in the modeling. Although, the selected areas in the second case were twice of the first one, yet, some of the areas selected in the first case are not included in the second. Study of the factors in these locations shows that the water discharges in the rocks are very low. In view of the high weight given to the river, and the usage of OR operator between the three water resource factors in the first inference network, the effect of the rivers strongly surpassed the effects of the other water resources. Consequently, these areas were accepted similarly to the areas where both the river accessibility and the water discharge are simultaneously high. These areas were simply not selected according to the second inference network. In this research, it was shown that for any considered arrangement of factors, proper inference networks can be designed that realistically represent the considered combination. Here, two different networks were proposed, studied and compared. Considering different assumptions, the factor maps related to water resources were integrated using fuzzy operators of SUM, OR and GAMMA. The results completely coincided with the concepts and viewpoints used in the design of the inference networks. This proves the high flexibility of fuzzy logic in representing and modeling complex inter-relations between spatial factors in site selection studies.

In this paper a monitoring GPS network has been designed for Bam fault in order to estimate the fault-model parameters, slip-rate and locking-depth, as accurately as possible. We integrated geological constraints to the optimization problem which limits the site locating. The optimization algorithm determines suitable places which are stable enough for setting GPS stations. The optimization tool is the genetic algorithm based on the principle of genetics as an intelligent method which gives the capacity of defining combined objective functions to optimize the geometry of the network for various applications. The numerical example shows that the fault-model must be considered in the fault monitoring network design.