Scientia Iranica
Volume:24 Issue: 4, 2017

This paper describes the development of a numerical model with the ability to simulate and analyze the mechanical behavior of di erent types of Double Bolted Flush End-plate Beam (DBFEB) splice connections, which thus far has not been reported. Moreover, Bolted Flush End-plate Beam (BFEB) splice connections have been investigated for calibration of the results using Finite Element Modeling (FEM). The initial sti ness, rotation capacity, strength ratio, ductility, failure mode, and the performance of these two types of connections have been investigated and compared with each other with respect to FEMA 356. Also, classi cation of these two types of connections is performed by Eurocode 3 recommendation. The analyses have been calibrated and converted to experimental and analytical results, which are also briefly reviewed in this paper. Also, due to the multitudeof influencing parameters, an analytical description of the behavior of DBFEB connections has been delivered based on component method. Moreover, several parametric analyses on the Initial RotationalSti ffness (Sini) of DBFEB connection have been conducted using regression analysis of FEM results.

One of the most important problems facing structural engineers is the analysis of dynamic behavior of bridges subjected to moving vehicles. In addition, viscoelastic supports under bridges change their dynamic behavior under passing trac loads. This paper presents how to model a bridge with viscoelastic supports and how the maximum dynamic stress of bridges changes during the passing of moving vehicles. Furthermore, this paper presents an algorithm to solve the governing equation of the bridge with viscoelastic supports as well as the equation of motion of a real European truck with di erent speeds, simultaneously. Using viscoelastic supports with appropriate characteristics can make a signi cant di erence in the magnitude on the maximum dynamic stress of bridges. By nite di erence method, it will be shown that how much the sti ness and damping of viscoelastic supports should be to have less impact and dynamic stresses in the bridges. It will be demonstrated that using viscoelastic supports can decrease the local maximum DAFs in the case of short and medium spans up to 5%. This study becomes more important where vehicle speeds are considerably high; therefore, the consequences of a full-length analysis with viscoelastic supports must be used to design safe bridges.

Time headway is an important indicator for evaluating car-following safety. To study the in uence of edge rate on time headway in car-following, three patterns of line marking were designed and placed on a real-world expressway, with actual vehicle ow data collected. Statistical analyses showed that (1) Time headways raised after the installation of line markings compared with the original situation; and (2) When the value of edge rate fell in [5 Hz,14 Hz], the time headway rose along the increase in the edge rate.
Furthermore, the increases in time headways were interpreted in relation with the leveling up of the driver's risk perception due to its overestimation in speed and underestimation in distance caused by edge rate. The nding of this study suggests that the designed line markings may bene t engineers and decision makers in providing them with a new approach to cope with critical issues in trac safety.

The conventional energy release rate approach to the computation of the crack compliance in rotors is critically reviewed and its shortcoming is highlighted. The state functions and the generic compliance are introduced, de ned, and veri ed. The proposed functions are de ned based on the end state's conditions and are exact. The crack compliance of the shaft in torsion is explicitly de ned as the function of the crack depth ratio and recommended as a good alternative to the classical procedure of the energy release rate method. The accuracy and eciency of the work are veri ed by concise mathematical formulation and comparison of the results of the work with the others in four examples.

In this paper, modeling the scour downstream of a flip bucket of spillways was considered using empirical formulas, soft computing techniques such as multilayer perceptron (MLP) neural network, and Multivariate Adaptive Regression Splines (MARS). For this purpose, 95 data sets were collected with regard to the most a ective parameters on the scouring phenomena at downstream of spillways. During the MLP model development, it was found that the two transfer functions, such as log-sigmoid and radial basis, had very suitable performances for predicting the desired scouring phenomena. The results of MARS model showed that this model with coecient of determination 0.99 and 0.91 during the development and testing stages, respectively, had suitable performance for modeling the scouring depth at downstream of flip bucket structure. The results of gamma test and MARS model indicated that q=(gd3 w), R=dw, and H=dw were the most a ective parameters on the scouring phenomena

Monitoring coastal areas is an important parameter in the sustainable development and protection of the environment. The expansion of constructions in Iran's southern coasts has not only led to the destruction of geomorphological landforms, but has also changed the process of erosion and sedimentation in coastal areas. Nowadays, remote sensing data are considered as the most ecient source of information for the study and interpretation of coastal landforms, tidal levels, changes in coastline, depth of water, and so forth. The purpose of this study is to investigate the changes in the coastline of Chabahar Gulf, located on the coasts of the Oman Sea by using remote sensing techniques. This study examined and interpreted qualitative and quantitative changes of the coastlines in a forty-two-year period. Di erent supervised classi cation methods were used from which the most accurate one was ultimately chosen. The classi ed images were divided into two classes of land and water, and the changes of these two classes between 1972 and 2014 were extracted. The net change results indicate that in the forty-two-year period, 1,832,436 m2 of the land has been added to water class, and 7,004,844 m2 of water has been added to land.

In this study, multi-criteria shape optimization of an asymmetrical doublecurvature arch dam is presented. Simultaneous cost minimization of dam construction and maximum allowable tensile stress are investigated for an economical and safe design approach in the current study. Pareto front method was used to balance both the economy and safety of the design simultaneously, which can be dicult for both analysts and decision-makers. A non-dominated solution based on the important parameters of dam analysis and design is presented. To help decision-makers in their decision, two diff erent methods are proposed. These methods for the case of an arch dam are Lombardi coecient and equilibrium point methods. The obtained results indicate that these two methods can be helpful for designers without experience and information of previous designs.

The seismic risk of reinforced concrete building frame located in the Guwahati City of northeast India is evaluated. To do so, we fi rst conduct a site-speci c probabilistic seismic hazard analysis to obtain hazard curve and implement proper selection of ground motion records for nonlinear time history analyses (NLTHA). Subsequently, the NLTHA of the building frame is performed to obtain the drift demand for any particular ground motion level. As the recorded accelerograms in the region are limited, the synthetic and artifi cial ground motion data are also generated to supplement the data base. Thereafter, the probabilistic structural capacity parameters at various limit states are obtained from random pushover analyses. Based on the knowledge of seismic hazard, demand, and capacity parameters, fragility curves are obtained corresponding to di erent structural performance levels. The annual probability of failure of the representative example frame is also estimated. The results of the seismic risk analysis indicate that a medium-rise reinforced concrete building frame in the study area with moderate fundamental period is most likely to perform beyond its elastic range. However, such structures designed according to the Indian codes are expected to be sufficient enough to prevent life-threatening risk and complete collapse.

Health monitoring of masonry bridges is vital due to their long life in service and an increasing need for higher axle loads. Results of feasibility study of applying an increased axle load of 25 tons to an old masonry bridge are presented in this paper. Babak Bridge is located in north western zone of Iranian railway network and has been in service for more than 70 years. It consists of stone masonry blocks, has three long spans of 21.5 m, 7 spans of 10 m, and a total length of 270 m. Response of the bridge subjected to prede ned train loading by 15 sensors, including deflection meters, accelerometers, and strain gauges, is recorded. A total of 37 tests are carried out on Babak Bridge, and the results are used to calibrate the nite-element model of the bridge, which is developed by Abaqus software. The numerical model is then used to determine the weak spots of bridge due to subjection of higher axle loads for a possible strengthening procedure. Ultimate load-carrying capacity of the bridge is also assessed by Ring software, which suggests a minimum adequacy factor of 1.25 for an axle load of 25 tons.

In this paper, application of Endurance Time (ET) method in nonlinear seismic analysis of off shore pile supported systems has been studied. The ET method is a time-history analysis in which structures are subjected to intensifying arti cial acceleration functions. The ET method reduces complexity and computational demand of conventional nonlinear seismic analysis, and it provides response at di erent seismic levels in a single ET analysis. The aforementioned methodology has been applied to a typical model of single pile
and then to a functional jacket o shore platform in Persian Gulf region. Seismic response of aforesaid models by ET method has been compared with conventional time-history method. The results indicate that ET method is reliable in capturing seismic response of off shore platforms supported on piles with an acceptable accuracy.

This paper investigates the seismic behavior of RC shear walls strengthened by Fiber Reinforced Polymer (FRP) composites. In this research, the e ects of strengthening shear walls with di fferent strengthening schemes and also strengthening walls with openings in di fferent dimensions and locations are studied. The development of nonlinear nite element methods has improved the accuracy of seismic analysis of complex structures. In this study, the ABAQUS software is used to investigate the nal resisting parameters, ductility, and behavior factor in these walls using nonlinear static analysis. The ndings prove that the applied strengthening schemes increase the nal strength of the wall. Also, the increasing ductility, behavior factor, and increased overstrength factor in some of these walls compared with original walls are observed. The ndings also prove that special openings with limited dimensions to improve seismic behavior of the wall are e ective, and the only limitation of using these openings is decreasing the nal strength which can be made up by using a proper strengthening scheme of FRP.

The asphalt industry has been at the forefront of sustainable development. Warm Mix Asphalt (WMA) has been developed to cope with issues such as high energy prices and air pollution. These mixes require less energy and generate fewer pollutants during production in comparison with conventional Hot Mix Asphalt (HMA). Although a promising technology, the durability of WMA is not clear because long-term WMA field performance data is limited. This study investigated the susceptibility of Sasobit-modi ed WMA to moisture, since moisture damage is a major cause of premature pavement failure in asphalt concrete. To this end, WMA samples were made using di fferent concentrations of Sasobit and the results were compared with those from HMA mixtures. The e ffect of hydrated lime as an anti-stripping agent was also investigated. The tensile strength ratios indicate that the introduction of hydrated lime and Sasobit increased the resistance of asphalt mixtures to moisture. Fracture energy and toughness were used to evaluate the crack resistance of specimens under dry and wet conditions. In comparison with Sasobit, hydrated lime increased crack resistance of mixtures. The results indicate that hydrated lime can be used as a compatible and eff ective anti-stripping agent for WMAs containing Sasobit.

A physical modeling apparatus made at Amirkabir University of Technology (FCV-AUT), called Frustum Con ning Vessel, is employed to determine the eff ects of soil improvement on piles performance. The FCV-AUT is capable of linearly modeling the existing overburden stresses in the eld. Three types of Babolsar sand with relative densities between 20% and 70% were examined in these tests. Results of compression and tensile load tests on seven piles, with the embedment length to diameter ratio (D/B) of 9, were used to evaluate the e ects of soil improvement methods of soil densi cation as well as postgrouting on the piles performance. The results show that the increased bearing capacity by soil compaction from loose to medium state is greater than that of the medium to dense state. This increase has been observed to be a function of pile construction methods and pile tip conditions. Also, tip and/or side post-grouting enhanced the performance of bored and concrete precast piles by increasing soil-pile interaction and its bearing capacity. The results of pile load tests carried out on the FCV-AUT have been observed to be well-aligned with the static bearing capacity calculations based on the API method.

One of the de ciencies of diagonal (X) bracing is buckling under compressive load, hence not reaching the yielding threshold and being unstable. In this numerical study, the behavior of X-shape brace was investigated, which was modi ed by Carbon Fiber Reinforced Polymer (CFRP) plates that could absorb compressive force and make it stable. This innovative brace consisted of two separate steel plates connected by CFRP sheets to each other in the middle of the compressive element. Thus, these two parts were connected by epoxy resin and bolts. In this study, Finite Element Method (F.E.M.) was used to simulate the elements of steel and ber polymers by Abaqus software under cycle loading after designing of ber layers and connection type. Also, the numerical result was compared with the normal steel brace. The result showed that the innovative brace had more eciency under seismic response. According to this output, ductility and energy absorption increased in the innovative model (CFRP-BR), but sti ness decreased as compared with the normal steel brace.