نشریه مهندسی عمران فردوسی
سال سی‌ام شماره 2 (زمستان 1396)

This paper experimentally discusses events being relevant to the arching effect in granular materials by the developed trapdoor apparatus. A focus on the features of stable arch at two moments when an arch is on the verge of collapse in addition to the time after the collapse. The critical arch for a granular medium is the last stable arch belonging to a trapdoor with maximum possible width at a particular base angle. The maximum trapdoor width is observed 4.7 to 8.67 times the average particles diameter depending on the internal friction angle and base angle values. The critical arch has the maximum width in proportion to previous run, whereas its height not only increases but will get smaller. After arch collapses, particles remained in the test box, are approximately located on the horizontal rails symmetrical. Besides, their arrangement remains almost constant compared to early one.

In recent years, Steel Plate Shear Wall system is used in tall buildings because of its advantages such as high initial stiffness and resistance, energy-dissipation capability and economic feasibility. Due to architectural requirements, using of big bays is usual and so if the usage of steel plate shear wall is needs in these bays; its couple type is used. The Steel Plate Shear Wall with Coupling (SPSW-WC) consist of a pair of planar spsws linked together with coupling beams at the floor levels. In this research, various frames (SPSW-WC) in 3, 10, 15 stories with rigid joint with three different length link beam 1.25, 2.5 and 3.75 meter which were proportioned to have a plastic section modulus 100% of the HBE (CB/HBE ratio) at each floor level and were put by using three acceleration mapping with nonlinear dynamic analysis and ABAQUS software and the performance of the walls and link beam in base shear, drift and DC (degree of coupling) were investigated. The results show that with reduction of link beam length in Steel Plate Shear Walls with Coupling system, base shear increase and drift and period of structure decrease, also the link beam length changing has different effects on coupling degree.

Piano Key Weir (PKW) is a flow control structure and it is a developed version of non-linear weirs that has a high discharge capacity, so that, for a specified discharge rate, the flow head above the weir is small, which may increase the likelihood of woody debris collection. In this study, the discharge capacity were investigated through 5 different geometry of the weir with the ratio exit to entrance lengh overhang with the values Bo/Bi=0, 0.5, 1, 1.25 and 1.5 and also the probability of woody debris collection using five models wood ad the location of the critical zone for obstructing the debris in the said weir was studied. The results indicate that increasing the length of the spillway crest increased discharge capacity, so that PKW1.5 than to PKW0 has increase discharge capacity to 26 percent. Also at a constant discharge PKW1.25 than other models in this study is less sensitive to ocllecion. And likelihood of trunk woody debris collection at this model relative to the models with ratios of Bo/Bi=0, 0.5, 1 and 1.5 has 7/18, 2/39, 9/38 and 8/7 percent less respectively. Also in all models most obstruction was occurred in the entrance region of exit keys.

Results of a comprehensive experimental study on the impact of the outfall source shape on flow characteristics in surface discharge of negatively buoyant effluent in stagnant water were done on two sections of rectangular and trapezoidal (The optimal hydraulic cross section). These experiments were recorded in dark room and processed using digital analysis. Dense flow behavior was reported for Densimetric Froude number less than twenty so, the self-similarity property of flow is not established in these experiments. The parameters examined in this research include flow pattern, concentration profiles, change width and flow trajectory. The result of flow behavior in these sections indicates that despite similar behavioral pattern, geometric and mixing characteristics of trapezoid are better than rectangular.

In this study, the properties of binary mixtures containing phosphorus slag (80 wt.%) and Portland based-chemical activator (20 wt.%) at three Blaine fineness of 2050, 3030, and 4500 cm2/g were studied. Also, Blaine fineness of 3030 cm2/g was selected to investigate the effect of curing temperature of 45, 85, and 200 ºC on compressive strength improvement. The experimental results showed that with enhancement of Blaine fineness, the bulk density and setting time decrease and water-to-cement ratio and compressive strength increase and at temperatures higher than 45 ºC, compressive strength decreases at later curing times.

Standard test method for bulk electrical conductivity (ASTM C1760) provides a rapid indication of the concrete’s resistance to the penetration of chloride ions by diffusion. In this paper a new approach for assessing the bulk electrical conductivity of saturated specimens of hardened concrete is presented. The test involves saturating concrete specimens with a 5 M NaCl solution before measuring the conductivity of the samples. By saturating specimens with a highly conductive solution, they showed virtually the same pore solution conductivity. Different concrete samples yield different conductivity primarily due to differences in their pore structure. The feasibility of the method has been demonstrated by testing different concrete mixtures consisting ordinary and blended cement of silica fume (SF) and calcined perlite powder (CPP). Two standard test methods of RCPT (ASTM C1202) and Bulk Conductivity (ASTM C1760) were also applied to all of the samples. The results show that for concretes containing SF and CPP, the proposed method is less sensitive towards the variations in the pore solution conductivity in comparison with RCPT and Bulk Conductivity tests. It seems that this method is suitable for the assessment of the performance and durability of different concretes containing supplementary cementitious materials.

A Boundary Element Code has been developed and verified by numerous study .The results of the analysis of topographic forms triangular, trapezoidal, semi-circular and semi-elliptical under seismic SH waves show that one of the important factors that influence on the dynamic behavior canyons are geometric parameters (shape and depth). These factors with different frequency have various effect. The results indicated that several parameters such as wave parameters (frequency and direction) are factors that affecting the pattern of displacement on the canyon. It was demonstrated that the effects of this parameters are highly dependent with incoming frequency. That is demonstrated with increasing frequency, Effects of depth is increases. It is clear that, the graph of materials effects (damping and Poisson) on the dynamic behavior and displacement pattern are undeniable and increase the accuracy of result that need to be considered.

Biological method is an unusual way for soil stabilization in civil engineering, particularly in the sectors of road. Microbial limestone deposits occur due to urea hydrolysis by an enzyme called urease. Through this reaction, PH of the soil increases and Crystals of limestone deposit between soil particles and reduce the permeability of soil. In this study, by using experimental results at the National Institute for Genetic Engineering and Biotechnology, a road improved sandy bed is modeled by biological methods. ABAQUS 6.11 in this study is used. The soil layer is modeled in elasto-plastic condition and Settlement is calculated by using elasto plastic model in various thicknesses. The results show a significant effect in reducing plastic deformation and increasing soil strength by using biological methods in soil improvement.