نشریه مهندسی سازه و ساخت
سال پنجم شماره 1 (پیاپی 15، بهار 1397)

self-compacted concrete(SCC) is a concrete that can flow in the space between reinforcement without separation and compact only by their own weight. In this study, the effect of using silica fume, metakaolin, rice husk ash and fly ash with different ratios of 10% and 20% by weight of cement in self-compacting concrete containing magnetic water is concered. The fresh properties of self compacted concrete were's tested by means of slump flow, T50, V-funnel, L-box and visual stability index(VSI). The hardened properties were assessed, using compressive strength at the ages of 7 and 28 days. Also splitting tensile strength and water absorption test were assessed at the age of 28 days. In addition, concrete specimens were made using tap water and magnetic water, was passed through a magnetic field of 0.8 Tesla. The results show that pozzolanic materials are suitable in properties of self-compacting concrete containing magnetic water in terms of flowability and viscosity. Moreover, magnetic water can reduce the amount of superplasticizer, required for SCC, up to 45%. Also the results of hardened SSC show an improvement in mechanical and durability properties of concrete. The usage of silica fume with ratio 20% by weight of cement in self-compacting concrete containing magnetic water, increases the compressive and splitting tensile strengths by 48% and 35% respectively and decreases amount of water absorption by 55% at the age of 28 days.

Reinforced concrete (RC) structural elements such as peripheral beams, beams supporting the canopy, ring beams of circular slabs are common members which could encounter torsional moments. One of the up-to-date and modern techniques for strengthening such beams is using FRP sheets. The increase of service loads, degradation of mechanical properties and updates in code regulations would cause to the need for retrofit. Using FRP sheets as a strengthening technique would increase the flexure, shear and torsion capacity. It would also change the failure mode and/or plane. In this article, torsional strength prediction of RC beams strengthened by FRP using artificial neural networks has been investigated. Input parameters of ANNs are RC beam width, height, FRP sheet thickness, modulus of elasticity of FRP sheet, yielding stress of longitudinal and transverse steels, the compressive strength of concrete, the effective width of shear strips along beam length, center-to-center space of FRP strips, the angle of wrapping and number of FRP layers. The target parameter is the capacity of the beam in bearing the torsional moment. The results indicate that the idealized neural network having definite number of neurons in hidden layer, can predict the torsional strength of RC beams externally bonded with FRP with a high degree of precision. Considering the mentioned precision, the method could be an efficient alternative for time-consuming and highly cost experimental programs.

Bridges are known as the most susceptible components of any and transportation system. That is why before the earthquake in vulnerability assessment, to take the necessary actions. The ýgeneration of vulnerability functions in the form of fragility curves is a common approach for assessing bridges ýseismic vulnerability. The purpose of this study, Using an analytical method for the production of ýfragility curves for a road bridge in Mazandaran Province. Since this curves used for planning before and after the ýearthquake, and in order to increase the reliability of them, in this study we tried to use the most accurate analytical ýmethods (non-linear time history analysis) and most prestigious modeling assumptions. Due to the specific ýcharacteristics of far fault earthquakes, effects of such earthquakes on bridges have been investigated using fragility ýcurves. Due to the geometry of the bridge for exact analysis, bridges was under 100 pairs of earthquake ýrecords in orthogonal directions and fragility curves was drawn and then were compared. Observed that changing the diameter of the bridge piers affect how much on the. One of ýthe common simplifications used in modeling are: elimination of abutment and foundation and pile by fixing the ýabutment and foundations in modeling. It can be seen that by eliminating this effect, increase the median values of ýfragility and in fact to reduce probability of vulnerability in Charts. After time history analysis it was found that by ýreducing the diameter of the piers, relative displacement (drift) in the longitudinal direction and in the transverse ýdirection increases.

Nowaday, with the proliferation of terrorist attacks on buildings in the world, a close examination of the behavior of structures under blast loads is a necessity. Pressure caused by the explosion of one of the most destructive loads that the structure may experience. Since the existing structures are usually designed to the common gravity and seismic loads, it is necessary to investigate their performances under blast loadings. In this study, analytical studies have been done for 2D structural models of concrete flexural frame and shear wall Partially Buried system with different number of stories 2 and 5. structures assessed based on the UFC 3-340-02 guidelines for 1000 kg TNT blast from 20 meters, the software SAP 2000 Design and nonlinear dynamic analysis have been. In order to loading, pressure values obtained from the explosion's blast wave, shock waves and pressure from the calculated reflection and As well as air blast wave parameters, including speed wavefront, period and wavelength explosion was determined and pressure graph - time of the explosion is offered. After analysis, The plastic hinge rotation, the formability and the highest axial force, shear force and bending moment occurred members, as well as maximum displacement, velocity and acceleration absolute floor level roof for all models will be investigated.

Iranian Seismic design code (standard No. 2800) increases the design spectrum ordinates by a modification factor (N factor), to consider the damaging effects of near fault ground motions in design procedure of structures. Accordingly, the spectrum modification factor depends on fundamental period of vibration and seismicity level of the region. In this paper, the preciseness of the expression given by Iranian seismic design code for calculation of spectrum modification factor is examined and estimations are suggested for N factor by evaluating the near fault effects on inelastic seismic response of steel moment-resisting frames. For this purpose, the response spectrum shape and nonlinear seismic response of sample structures are evaluated for one set of far fault and three different sets of near fault ground motions. Incremental dynamic analysis is utilized to obtain the seismic response of the sample frames (including five steel frames with 3 to 15 stories) in various intensity levels. The results of the study demonstrate that modification factors provided by standard No. 2800 does not precisely take account the effects of near fault excitations on inelastic seismic response of steel moment-resisting frame structures. Also, it was found that there is no meaningful relationship between spectrum modification factor and structural period.

In this paper, parametric studies were performed on some pipes buried in soil under blast loadings. The effects of various parameters, such as the physical properties of liquid, air, soil, pipe, and T.N.T were investigated. The Arbitrary Lagrangian-Eulerian (ALE) method was used in the LS-DYNA software. In the following, a compared between liquids. The results show that, the pipe has undergone increased pressure and stress by reducing the fluid density. Also,This indicates that the higher the fluid density is, the less pressure and stress will be impose d on the pipe and vice versa. In general, the result demonstrates that a higher density of soil causes higher pressure and stress transfers on the pipe and explosion in lower soil density result in less damage to the pipe and acts as a damper under waves of explosion. In other words, higher density in the soil causes more pressure and stress transfers on the pipe and lower soil density acts as a damper under the waves of explosion. Now, knowing the soil type performance on the stress and pressure transfers in the buried pipes under explosion, it can be realized that pipes with high resistance should be used in soils with high density due to the transmission of high stress and pressure through the pipes considering the fact that buried pipelines, while in soils with lower density, pipes with lower resistance can be applied due to better soil performance like a damper and transmission of less stress and pressure through them. Therefore, with the correct selection of pipes in terms of resistance according to the regional soil type, a substantial sum can be economically saved for the implementation of oil and gas pipeline projects.

Permeability is one of the most important factors affecting in the durability of concrete. So in this article, the effect of concrete strength, water absorption, density and strength of rock on the permeability of concrete studied. In the Studied concrete used separately from eight type’s rock with different characteristics namely silica stone, marble, andesite, limestone, travertine, tuff, dense tuff, granite. To determine the permeability of concrete used “cylindrical chamber” method. Also, to study the strength of concrete and rock used the “Twist-off” and uniaxial compressive strength methods. The results shown that the relationship between concrete strength and permeability of concrete with correlation between 0.67 to 0.77 is over than the correlation of other factors such as water absorption, density and strength of rock. Also, the concrete made with the travertine aggregates had highest and the concrete made with the granite aggregates concrete had lowest amount of water permeability. The Concrete made with dense tuff and marble aggregates had the relatively similar conditions in the amount of water permeability. Also, studies show that the permeability of concrete resulted from andesite and tuff aggregates is similar. Permeability of The concrete made with limestone aggregates was 11.8 times of permeability of concrete made with granite aggregates.

Due to the high complexity in the mechanism of earthquakes occurrence, it is not possible to predict it accurately at a given site. Experiences and scientific findings indicate that using the statistical and probabilistic techniques entitled seismic hazard analysis, the safety of the structures can be desirably assessed. This study evaluates the seismic hazard of Bushehr province using the probabilistic and in some cases the deterministic approaches. To assess the seismic hazard, an area of 150 km around Bushehr province has been considered. Seismic linear sources have been prepared using the available maps. Historical and instrumental earthquake catalogue has been provided using the published catalogues. Foreshocks and aftershocks have been removed from the catalogue by applying the Gardner and Knopoff algorithm. Then, by employing the Keijko and Gutenberg-Richter methods, suitable seismicity parameters have been calculated. Finally, according to the seismic power of each fault, the mentioned parameters have been assigned to the faults. Seismic hazard analysis has been performed using the desirable ground motion prediction equations. Results have been presented as the deterministic and probabilistic acceleration response spectra for important cities. The probabilistic seismic hazard zonation maps have been provided for the return periods of 75, 475 and 2475 years.

In This research, the subject of buckling of columns on elastic foundation with different boundary conditions by energy approach has been presented. Columns modeled by two-end rigid bars where interconnected to each other by rotational springs, and elastic foundation modeled by translational springs. By preparing computer programs for five column types with different boundary conditions, the critical loads of these columns have been obtained. This five types of columns include two hinge end column, one fix end-one hinge end column, two fix end column, one fix end-one free end column and one hinge end-one free end column which are located on elastic foundation. At first, the stiffness of translational springs is set equal zero, and by knowing the analytical solutions, the stiffness coefficients of rotational springs have been gathered. Then, by defining a dimensionless parameter which showing the relative stiffness of elastic foundation, the critical load for a wide range of foundation stiffness has been obtained and results are presented in form of some graphs. There is analytical solution for two hinge end column on elastic foundation, therefore, at this stage, verification has been done for this kind of column and a very good consistency is observed between analytical buckling load and finite element buckling load for different relative stiffness of foundation. In fact, there is a linear relation between buckling load of two hinge end column and relative stiffness coefficient of foundation. But, for other four type columns, this relation may not be linear. Therefore, by means of fitting curve method, for other four type columns, some mathematical relations are proposed, which by these mathematical relations, the buckling load of above mentioned columns are computed in according to relative stiffness of foundation by acceptable errors.

Hybrid modeling enables us to use strengths of various simulation approaches. System dynamics is a continuous simulation approach which uses feedback loops, stocks and flows to simulate the complicated behavior of complex systems over time. Agent based modeling is a simulation methodology which uses some specified rules to simulate the behavior of agents in their surrounding environment. Combining of system dynamics and agent-based modeling approaches enhance the capabilities and strengths of individual simulation paradigms. Also, it enables modelers to study more sophisticated problems. This paper presents a novel framework to integrate system dynamics and agent-based approaches to be implemented on construction projects. The proposed approach can provide a complete guideline for modelers by accounting for the most important issues which should be considered by modeler during integrating system dynamics and agent-based approaches. The framework proposes five steps to develop hybrid system dynamics and agent-based models. This step by step process helps to solve complex construction problems considering features of the problem. To evaluate the performance of the proposed approach it is implemented in a real project to investigate the unsafe behavior of different workgroups in a construction site taking account of the interactions with other working groups as well as the surrounding environment. Finally, the project duration is predicted taking account of unsafe behavior of different working groups.

In the design of high-rise buildings, three parameters such as resistance, hardness and stability are very important and when the height of building rises, effect of toughness and stability in optimum design will be dominate more than of the effects of these two factors against the lateral loads from wind and earthquake. The best ways to satisfy these two factors is the use of innovative forms and models of structures, so that, while maintaining stiffness, reducing deformation and drift caused by lateral loads, increase the stability of the structure. Outrigger and belt truss system are one of the innovative systems in high-rise structures that use it substantially reduces the consumption of structural steel and construction costs are high.
In this research, two 2D frame with 5 spans and 30 and 50 stories according to the Iranian codes were designed in two cases of: the moment frames and frames with outrigger and belt with. Then maximum displacements of nodes and maximum inter stories drifts calculated for every earthquake records with use of SAP2000 software and time history analysis and has defined three different threshold IO, LS, and CP and acceleration of each record based on the severity of the earthquake. Then curves were plotted for each case; the results indicate that the outrigger and belt truss system would reduce the maximum inter story drift about 12 to 28 percent.

In this paper, the dynamic behavior of concrete rectangular tanks under the effects of soil-structure interaction and motion caused by earthquakes is studied. The simultaneous effects of soil-structure-fluid interaction on the dynamic behavior of concrete rectangular tanks by the finite element method in three-dimensional space, based on linear analysis and in-time domain is discussed. Considering that, in some tanks such as large reinforced concrete pool structures used for long-term storage of nuclear spent fuel assemblies or prestressed concrete water tanks where the flexibility of the rectangular tank wall can cause a significant effect on the dynamic responses, the tank walls are considered as flexible plates. A simple model with a viscous boundary is used to include deformable foundation effects as a linear elastic medium. For dynamic evaluation of a rectangular container located on the foundation, six different types of soil approved by the current regulations and design standards are used. In the finite element model, the effects of different soil types on structural responses have been evaluated and comparisons between dynamic responses such as base shear, base moment, hydrodynamic pressure distribution and sloshing responses under different ground motions have been evaluated by changing soil properties. It is concluded that the soil under the tank, depending on its type, can cause significant changes in the dynamic responses.

Eccentrically braced frames are one of the most proper lateral resisting systems in seismic areas. The link beam in an eccentrically braced frame acts like a structural fuse, which is able to sustain large plastic shear or flexural deformations. Therefore, other structural members such as beams and columns are expected to remain elastic during a severe seismic ground motion. The reduced beam section has recently been proposed for moment resisting frames, which results in the concentration of the plastic deformations at the ends of the beams and in a place far from the connection. In this paper, reduced beam sections are implemented in an eccentrically braced frame (Dual system) at the ends of link beams as well as other beams placed inside the moment resisting frame. Finite element analyses in ABAQUS software are conducted in order to evaluate and compare the seismic response of the eccentrically braced frames with reduced beam sections and without them. For this purpose, 4, 8, and 12 story braced frames designed according to Iranian national building codes are considered. Pushover analysis and also nonlinear time history analysis are carried out. The results show that the braced frames including reduced beam sections at the ends of the link beam and other beams, possess higher ductility and response modification factor. In addition, the results show that during time history analyses, the systems with reduced beam sections experience higher inter-story drift demands in comparison to the system without reduced beam section.