Showing papers in "Civil engineering infrastructures journal in 2020"

Effect of Objective Function on the Optimization of Highway Vertical Alignment by Means of Metaheuristic Algorithms

Abstract: The main purpose of this work is the comparison of several objective functions for optimization of the vertical alignment To this end, after formulation of optimum vertical alignment problem based on different constraints, the objective function was considered as four forms including: 1) the sum of the absolute value of variance between the vertical alignment and the existing ground; 2) the sum of the absolute value of variance between the vertical alignment and the existing ground based on the diverse weights for cuts and fills; 3) the sum of cut and fill volumes; and 4) the earthwork cost and then the value of objective function was compared for the first three cases with the last one, which was the most accurate ones In order to optimize the raised problem, Genetic Algorithm (GA) and Group Search Optimization (GSO) were implemented and performance of these two optimization algorithms were also compared This research proves that the minimization of sum of the absolute value of variance between the vertical alignment and the existing ground, which is commonly used for design of vertical alignment, can’t at all grantee the optimum vertical alignment in terms of earthwork cost

Application of SCB Test and Surface Free Energy Method in Evaluating Crack Resistance of SBS Modified Asphalt Mixes

Abstract: Cohesion properties of the binder matrix within asphalt mixes and adhesion characteristics of the asphalt binder and aggregate particles are the two major mechanisms resisting against cracking in asphalt mixes This study is focused on estimating crack resistance of asphalt mixes at intermediate temperatures through evaluation of cohesion and adhesion properties of binder-aggregate systems using Surface Free Energy (SFE) method Semi-Circular Bending test (SCB) was used to support the SFE analysis SFE measurements were performed applying Sessile Drop test method A Granite aggregate type and two asphalt binders (PG64-16, PG58-22) containing various amounts of SBS polymer were used to produce six groups of asphalt mixes Cohesion and adhesion energies obtained from SFE analysis and Flexibility Indexes and Fracture Energies determined in SCB test showed the positive effect of SBS on performance of asphalt mixes at intermediate temperatures, although the effectiveness of SBS modification was more pronounced with SCB parameters A linear regression was performed and a strong correlation was observed between SFE results and SCB parameters

Numerical Analysis of Steel-Concrete Composite Beam with Blind Bolt under Simultaneous Flexural and Torsional Loading

Abstract: This paper investigates the composite beam with bolt shear connectors. Composite beams are usually used as secondary beam in buildings. It is clear that studying the torsion in side beams in buildings such as balconies is of great importance. The composite beam was loaded under three different loading conditions including a pure flexural loading, and simultaneous flexural loading with two alternative torsional loading modes. The obtained results from the analysis were compared with each other by three-dimensional non-linear finite element model using ABAQUS. The obtained results, including the mid span deflection, the rotation and slip of composite beams under different loading conditions were investigated. The effect of the type and number of shear connectors on slip of composite beam was studied, too. The results indicated that the slip between the steel beam and the concrete slab along the composite beam increased due to flexure loading, but the torsional loading had a slight effect on the slip.

Validation of the Driver Behavior Questionnaire in a Representative Sample of Iranian Drivers

Abstract: The Driver Behaviour Questionnaire (DBQ) is widely used around the world to investigate driving behaviours However, it has several different versions extracted from the 50-items Manchester driver behaviour questionnaire for variety of societies This study aims to calibrate the DBQ for the Iranian driver population and explore their aberrant driver behaviour In total, 524 participants (325 men and 199 women) between the ages of 18 and 79 years from different cities of Iran with more than one million populations were engaged in this study (Tehran, Mashhad, Esfahan, Qom, Tabriz, Karaj, Ahvaz, Shiraz) Principal Component Analysis (PCA) with varimax rotation extracts four-factor that describes the aberrant driver behaviours: violations, dangerous errors, lapses, and aggressive behaviours A short version of DBQ with 20 items is also developed on the same four factors using high factor loading of each of the axis categories This DBQ can serve as an instrument of driver self-assessment and can use with other self-reporting measures For reliability assessment, the Cronbach’s alpha test (α) is conducted for both long and short version of the questionnaire Finally, regression analysis predicts the factor scores using demographic and some general questions

Analyzing the Effects of Soil-Structure Interactions on the Static Response of Onshore Wind Turbine Foundations Using Finite Element Method

Abstract: The use of wind turbines to generate electricity has increased in recent years One of the most important parts of a wind turbine is the foundation, which should be designed accurately because it is influenced by difference forces Soil cannot carry tension stress; thus, when a wind turbine foundation is applied eccentricity forces, a gap appears between the soil and foundation The gap will have no positive effect on the ultimate bearing capacity of the foundation This must be considered when designing the dimensions of an onshore wind turbine on a spread foundation using finite element software in order to avoid error during analysis In the current study, a spread foundation of an onshore wind turbine was simulated using ABAQUS and PLAXIS-3D software Based on the results, the effects of Soil-Structure Interaction (SSI), eccentricity of forces, soil strength parameters and the foundation buried depth on static response of the foundation are discussed The results indicate that the influence of soil-structure interaction is depend on magnitude of eccentricity of forces and depth of foundation, so that soil-structure interaction has little impact on settlement of foundation when eccentricity of forces is less than 1/6 of the diameter of the foundation and this has important effect when the eccentricity forces at an amount exceeding 1/6 of the diameter of the foundation In addition, this effect decreases with increasing the foundation buried depth and independent of the soil strength parameters (φ´ and C)

Investigating the Performance of Cracked Asphalt Pavement Using Finite Elements Analysis

Abstract: Occurrence of top down and bottom up fatigue cracking in asphaltic pavements is common Conventional pavement analysis methods ignore the existence of cracks in asphaltic layers However, it seems that the responses of cracked pavement would not be the same as a pavement without crack This paper describes effects of crack type, position and length, and vehicles tire inflation pressure and axle load on the performance of cracked asphalt pavement Tensile strain at the bottom of asphaltic layer, the vertical strain on subgrade, maximum deflection on the surface, rut depth and the stress intensity factors of cracked pavement, with top down and bottom up crack have been computed using 3D Finite Elements method in ABAQUS Moving load of standard single axle with different loads and tire pressures have been used in the analysis Standard 82 ton single axle load at different tire pressures of 552(80), 690(100), 828(120) and 1035(150) kPa(psi) and single axle at different loads of 5, 82 and 15 ton, all at the same tire pressure of 690 kPa, have been used Results show that the pavement responses increase with increasing tire pressure and axle load with higher values and rate of increase with increasing tire pressure and axle load for the cracked pavement compared with the pavement without crack For the pavement structure investigated in this study, it was found that, in general, top down crack results in higher responses than bottom up crack

Discrete Element Modeling of Dynamic Compaction with Different Tamping Condition

Abstract: Dynamic Compaction (DC) is a common deep compaction method that is usually used for densification of coarse-grained soils Although traditional continuum-based models such as the Finite Element Method can be successfully applied for assessment of stress distributions or deformations induced by DC, they are typically not adequate for capturing the grain scale mechanisms of soil behavior under impact In contrast, numerical models such as Discrete Element Method (DEM) in which the interaction of constituting distinct elements is explicitly simulated are promising for simulation of DC process In this study, dynamic compaction in a dry rockfill was simulated through a two-dimensional DEM model Based on the developed model, a series of analyses with various tamper weights and drop heights were conducted to investigate the effects of important factors such as energy and momentum per drop on DC results Comparison of the obtained results with experimental observations reveal the capability of DEM for simulation of DC The numerical simulations also confirm the positive effect of using conical-based tampers in DC process

Investigating the Reliability of Negative Skin Friction on Composite Piles

Abstract: In this study, the impact of Negative Skin Friction (NSF) on composite piles concerning different variables such as different pile sections, the amount of concrete and steel consumption, and various interaction coefficients of the pile-soil system in both solid and hollow conditions are evaluated using numerical methods. Besides, the effect of the variables considered on the negative skin friction and pile’s settlement is investigated. Numerical analyses were performed using ABAQUS and MATLAB. The results showed that the amount of frictional stress on the pile decreases if the hollow sections are used. However, the hallow pile experiences more settlements than other piles’ models. On the other hand, if the amount of consumed steel in a pile is reduced, the amount of negative skin friction induced in a pile decreases, while the pile settlement increases. After examining the Finite Element of concrete piles in fine-grained soils, the safety surface of the suggested numerical relationship was considered in the phenomenon of negative friction on the pile. For this purpose, considering the uncertainty parameters such as mean, variance and probability function for overcharge, soil parameters, dimensions and different types of the single pile, the amount of settlement, the stress created on the pile, the position of neutral plane on the pile and drag load were calculated using the proposed relationship. Finally, the safety surface of the proposed relationships or comparisons of a Finite Element results in a close approximation to the real models was computed.

Cosine Integral Transform Method for Solving the Westergaard Problem in Elasticity of the Half-Space

Abstract: The cosine integral transform method is applied to find the expressions for spatial variations of displacements and stresses in the Westergaard continuum under vertical concentrated loading, and distributed loadings acting over lines and geometric areas on the surface. The half-space is considered to be horizontally inextensible and the displacement field reduces to the vertical displacement component. The paper derives a displacement formulation of the equation of equilibrium in the vertical direction. Cosine integral transformation is applied to the formulated equation and the Boundary Value Problem (BVP) is found to simplify to Ordinary Differential Equation (ODE). The general solution of the ODE is obtained in the cosine integral transform space. The requirement of bounded solutions is used to obtain one integration constant. Inversion of the bounded solution gave the solution in the real problem domain space. The stress fields are obtained using the stress-displacement equations. The requirement of equilibrium of the vertical stress fields and the vertical point loading at the origin is used to determine the remaining integration constant, and thus the vertical deflections and the stresses. The solutions obtained are kernel functions employed to derive the expressions for solutions for line, and uniformly distributed loads applied over given geometric areas such as rectangular and circular areas. The vertical stresses are expressed in terms of dimensionless vertical stress influence factors and tabulated. The vertical displacements and stresses obtained are identical with Westergaard solutions obtained by stress function method. The solutions agree with results obtained by Ike using Hankel transform method.

Investigation of the Effects of Link Beam Length on the RC Frame Retrofitted with the Linked Column Frame System

Abstract: This study investigates the effect of different link beam lengths in the Reinforced Concrete (RC) frame retrofitted with the Linked Column Frame (LCF) system It also investigates the ratio of the link beam length (e) to the span length of the RC frame (L) from 0 to 15 for the 9 models of the RC frame retrofitted by the LCF system has been investigated In addition, it studies the formation of plastic hinges in the RC and Linked Column (LC) frame, distribution of stiffness between the RC and LC frame and the ratio of the structural displacement with the formation of the first plastic hinge in the member of the RC frame at the collapse prevention level (Dp LCF) to the structural displacement with the formation of the first plastic hinge in the link beam (Dy LCF) has been studied Based on the nonlinear static analysis results, the model with the ratio of e/L= 045 has a better performance than other different lengths of the link beam In this model, the stiffness of the LC frame has increased about 78% in comparison with the model with the ratio of e/L that is more than 06 Also, the ratio of Dp LCF to Dy LCF for the model of e/L = 045 in comparison with two models of e/L = 03 and 06 is more about 14% and 22%, respectively It means that, the model of e/L = 045 has more potential to reach the performance level of Rapid Repair (RR) to occupancy

Estimation of Damping for a Double-Layer Grid Using Input-Output and Output-Only Modal Identification Techniques

Abstract: In large civil engineering structures, the output-only modal identification is the most applicable technique for estimating the modal parameters such as damping. However, due to no measurement and control of excitation force, the identified parameters obtained by output-only technique have more uncertainty than those derived from the input-output technique. Given the different nature and uncertainties of the two modal identification techniques, in the present study, the damping related to the first 12 modes of a double-layer grid developed from the ball joint system were identified via the two techniques and compared with each other. For this purpose, a double-layer grid was constructed by pipes and balls with free-free boundary conditions provided for both input-output and output-only experiments. Exciting the grid, its acceleration response was measured at appropriate degrees of freedom. Then, by using these data and performing modal analysis, involving four different methods of input-output and five different methods of output-only, the natural frequencies and damping ratios of the desired modes were extracted. The results indicated that despite the good agreement between the modal damping of the grid, as identified by different methods of input-output together and by different methods of output-only together, the results of input-output and output-only methods were different with each other. The damping values through the input-output modal identification methods were on average 65% higher than the corresponding values of the output-only modal identification methods.

Axisymmetric Scaled Boundary Finite Element Formulation for Wave Propagation in Unbounded Layered Media

Abstract: Wave propagation in unbounded layered media with a new formulation of Axisymmetric Scaled Boundary Finite Element Method (AXI-SBFEM) is derived. Dividing the general three-dimensional unbounded domain into a number of independent two-dimensional ones, the problem could be solved by a significant reduction in required storage and computational time. The equations of the corresponding Axisymmetric Scaled Boundary Finite Element (AXI-SBFE) are derived in detail. For an arbitrary excitation frequency, the dynamic stiffness could be solved by a numerical integration method. The dynamic response of layered unbounded media has been verified with the literature. Numerical examples indicate the applicability and high accuracy of the new method.

Effects of Aluminum Incorporation in Tobermorite Structure on Chloride Diffusion: A Molecular Dynamics Simulation Study

Abstract: In this paper, the effects of different aluminum to silicon ratios in silicate chains of calcium silicate hydrates (C-S-H) are evaluated on the diffusion coefficient of chloride ions by molecular dynamics method. Tobermorite is a crystalline phase that is used for studying C-S-H properties in nano scale, because of its analogous chemical composition to C-S-H. Aluminum incorporation in C-S-H and the formation of calcium aluminosilicate hydrates (C-A-S-H) is due to both of hydration of tricalcium aluminate (C3A) in portland cement and aluminum oxides in pozzolans. There exist different Al/Si ratios in the tetrahedral chains of C-A-S-H depending on available aluminum oxides in cementitious raw materials. In order to compare the simulation results with previously-published experimental researches on cement pastes, a novel method is introduced here to calculate Al/Si ratio in tetrahedral chains of C-A-S-H using pozzolan replacement ratio in cementitious paste. MK (metakaolin) and FC3R (Fluid Catalytic Cracking Catalyst Residue) are the pozzolans that are used to validate the obtained results in this paper. Results showed that diffusion coefficients of chloride ions in C-A-S-H decrease by Al/Si ratio increasing in the tetrahedral chains as it was observed experimentally in previous researches.

Shear Behavior of Panel Zone Considering Axial Force for Flanged Cruciform Columns

Abstract: Panel zone is a part of a column web where surrounded by the continuity plates and the column flanges. Panel zone plays a vital role in the connection behavior. Despite the upward tendency of using cruciform section in many seismic regions, few studies have focused on the behavior of these columns, and especially on the behavior of their panel zone. As well, some recent studies have shown that axial load has a remarkable effect on the yielding process of the panel zone. In this research, a mathematical model is presented to consider the effect of axial force on the behavior of the panel zone in the cruciform columns. The model included the shear stiffness of the panel zone in the elastic and non-elastic region, the yield shear and the ultimate shear capacity of the panel zone. Consequently, 432 Finite Element Models (FEM) in a wide range of dimensions are performed and a parametric study has been done. The comparisons of the results of proposed mathematical model with the results of all Finite Element models demonstrate that the average and maximum deviation for yield and ultimate shear strength of the panel zone are respectively 5.32%, 8.12%, 6.2%, and 8.44%. This matter exhibits the accuracy and efficiency of the proposed mathematical relations.

Experimental Investigation of the Effective Parameters on the Strength of Soil - Cement

Abstract: Soil-cement is a mixture of Portland cement, soil and water, which are bonded together due to the cement hydration and compaction. It have durability, low permeability and resistance against wear. Water to cement ratio, cement content and type have been commonly investigated as the most effective factors on the compressive strength of soil-cement. This study aims at the investigation of the effects of some other factors, such as Sand Equivalent (SE), Plasticity Index (PI), and gradation of the soil on the compressive and flexural strength of soil-cement. Results show that the compressive and flexural strength of soil-cement increases with increasing the sand equivalent and decreasing the plasticity index of the soil.

Determination of Creep-Induced Displacement of Soil Slopes Based on LEM

Abstract: The creep of earth slopes is an important challenge of the long-term stability of slopes. This paper develops a limit equilibrium method (LEM)-based analytical approach for calculating the shear displacement of creep-induced failure surface in 2D state for all slices where both force and moment equilibrium equations are simultaneously satisfied as a new research. The relation between shear displacement and creep time is obtained with regard to visco-elastoplastic creep model. The overall safety factor is first calculated for the slip surface using Spencer method. Then, the shear displacements of all slices are obtained based on vertical displacement of crown and using displacement compatibility relation exists between slices. By combining force and moment equilibrium equations and assuming a zero resultant for inter-slice forces, the vertical displacement at crown is determined using visco-elastopastic creep model. A numerical model was developed to calculate slope displacement by the proposed method. Force and moment equilibrium equations are simultaneously satisfied by iteration technique. The proposed method is verified through two numerical examples comparing the new approach and conventional finite element method.

Improving Cyclic Behavior of Steel Plate Shear Walls with Elliptical Perforations

Abstract: In this paper, the effect of elliptical shape openings was numerically compared to the case when circular openings were used in the steel panel shear walls. At first, the finite element model in ABAQUS was calibrated by experimental results, obtained from previous studies. Then, three steel shear panels with different sizes of elliptical openings were analyzed under cyclic loads, and the results were compared to those circular perforations. Moreover, comparisons of cyclic response parameters such as elastic stiffness, ductility ratio, and energy absorption were made. According to the results, the shape of the openings has a significant effect on the seismic behavior of the perforated shear wall. The elliptical opening with the smaller to larger diameter ratio, equal to 0.5, increased the ultimate capacity by 15%. Furthermore, the elastic stiffness, ductility ratio of the frame, and the absorbed energy were promoted by 28%, 3%, and 8%, respectively. Finally, the distance between the openings was improved. Using a ratio of about 0.17 for the center to center distance of elliptical openings to the total width of steel panel led to the best performance.

Assessment of Environmental Parameters in Pre- and Post-Monsoons at Chabahar Bay, Gulf of Oman

Abstract: This study is the first investigation to assess the variations of physical and chemical characteristics and biodiversity of planktons in offshore water column and chlorophyll-a and b, during the two monsoons at Chabahar Bay, to evaluate the water quality. To this end, 27 surface water samples in pre-monsoon (May, 2012) and totally 60 surface and deep water samples in post-monsoon (December, 2012) were collected from 9 and 10 stations at depths between 3.8 to 13.6 m in Chabahar Bay, respectively. The results showed that water salinity and pH with low variations were relatively higher in post-monsoon. The averages of water alkalinity levels in pre- (2.42±0.02 mmol H+/kg) and post- (2.44±0.01 mmol kg-1) monsoons were comparable to that of oceanic surface water (2-2.5 mmol H+/kg). In this study, 66 phytoplankton genus and species belonging to 13 groups were identified in pre-monsoon. Results demonstrated that nutrients were at higher levels inside the Chabahar Bay. Moreover, the physicochemical parameters of water samples were investigated and compared with international standards and data from other marine ecosystems. The results indicated that the water quality falls within the stipulated range of acceptability and sampling area can be classified as a good, stable, and healthy aquatic ecosystem.

Investigating the Marshall and Volumetric Properties of Asphalt Concrete Containing Reclaimed Asphalt Pavement and Waste Oils Using Response Surface Methodology

Abstract: This research aimed to use response surface methodology (RSM) for investigating the Marshall Stability (MS), flow and Voids in Mineral Aggregates (VMA) of asphalt concrete containing different percentages of Reclaimed Asphalt Pavement (RAP) and rejuvenated by different percentages of waste cooking and engine oil. Variables of RAP content in 3 different levels of 25, 50 and 75% (by the weight of total aggregates) and waste oils content in 3 different levels of 5, 10 and 15% (by the weight of total binder) were selected. Quadratic and linear two factor interaction models were well fitted to the experimental results. Analysis of variance showed that the models were capable to well predict the MS, flow and VMA of the mixtures, and the terms of oil and RAP content and type of oil are significant. MS, flow and VMA increased with increasing RAP content and decreased with increasing oil content. Results also reveal that higher MS, flow and VMA values are resulted by using WEO than using WCO. Some interaction effects were found between RAP content, oil content and type of oil on the responses. Optimization analysis showed that using 10.6% of WCO and 15% of WEO, allows a maximum RAP incorporation of 75 and 51.77%, respectively, by which the properties are similar to control mix. Use of the rejuvenators allows using high RAP content without sacrificing the properties of the mixtures.

A Modification on Applied Element Method for Linear Analysis of Structures in the Range of Small and Large Deformations Based on Energy Concept

Abstract: In this paper, the formulation of a modified applied element method for linear analysis of structures in the range of small and large deformations is expressed To calculate deformations in the structure, the minimum total potential energy principle is used This method estimates the linear behavior of the structure in the range of small and large deformations, with a very good accuracy and low analytical time The results show that analysis of a console beam by proposed method, even with minimum numbers of elements, in range of small deformations, has a computation error of less than 2% Meanwhile, solving the same problem by Applied Element Method (AEM), has more than 31% error Also, the buckling and post-buckling behavior of the structure, within the range of large deformations, is well-suited So, with minimum number of elements, and very high accuracy, the buckling behavior of the fixed-base column was simulated Also, the computational time of the proposed method is less than 40 percent of the computational time in the application of the applied elements method with 10 series of connection springs

Study of the Effect of Source Application on Sonic Echo Tests in Timber Piles

Abstract: The long-term effects of scour have been identified as one of the primary reasons for bridge failure. To evaluate the performance of the bridges against scour, it is essential to assess the conditions of the bridge foundation including the depth of the piles. Sonic Echo (SE) has been a favorable nondestructive method to evaluate the condition of unknown bridge foundations in the recent decades. Previous studies have shown that the results obtained from SE tests can be affected by a variety of factors such as the pile-to-soil stiffness ratio, length-to-diameter ratio of the pile, presence of defects and anomalies near the pile head, striking method, and hammer type. Although previous studies have discussed such affecting factors, there is a lack of comprehensive investigation regarding the effect of striking method and hammer tip type specific to wood piles supporting bridge decks. In the current study, the effect of striking method and hammer type on the success of SE tests conducted on wood piles has been scrutinized by investigating various options of striking methods and hammer tip types. After comparing different options, superior ones were identified and recommendations for better conducting the SE tests on unknown wood bridge foundations were presented. Numerical simulations were also performed to support some of the conclusions.

Fault-Tolerant Damage Control of Nonlinear Structures Using Artificial Intelligence

Abstract: In this paper, the artificial intelligence is employed to design a Fault-Tolerant Controller (FTC) for structural vibrations. The FTC is designed to reduce the probability of damage considering sensor fault. For this purpose, Neural Networks (NNs) are used as fault detection and accommodation and fuzzy logic is used as a controller. This control strategy requires two groups of neural networks. The first group of neural networks finds the faulty sensor by estimating the structural responses and comparing them with the responses obtained from the sensors. The second group has the task of estimating the response of the faulty sensor using data obtained from healthy sensors. To evaluate this method, the time history analysis of a 3-story benchmark building equipped with accelerometers and active actuators has been used. This evaluation is based on determining the probability of structural damage and the generation of fragility curves under forty ground motions. To develop fragility curves, the criteria specified in the FIMA 356 (IO, LS and CP) for the moment frame based on the inter-story drift are used. This study show that in the absence of the neural networks, sensor fault reduces the performance of the fuzzy controller and it is even possible to increase the structural responses compared to the structure without the controller. In addition, results demonstrate that the proposed control strategy can rectify the deterioration of sensor faults and decrease the probability of failure.

Comparison of Steel and Reinforced Concrete Frames’ Durability under Fire and Post-Earthquake Fire Scenario

Abstract: Two fire accidents took place in the Plasco Tower in Iran and Grenfell Tower of London in 2017. Although both of them have led to human tragedies, post-earthquake fire can cause more irreparable damages and catastrophes in larger extents. Engineering structures are subjected to different loads during their lifetime, which may cause damage or secondary loading effects. Evaluation of durability and stability of fired structures and the effects of seismic loading are considered to be significant parameters in fire engineering. The aim of this study is to evaluate and compare durability of reinforced concrete and steel frames during fire loading and post-earthquake fires. In this study, two 7-story steel and reinforced concrete frames are exposed to the fire load. At first, steel and concrete sections are put under various thermal loads in order to compare the method of their heat transfer. Then, the effects of crack on heat transfer of concrete sections are studied. Afterwards, the selected frames are exposed to the fire and post-earthquake fires. The results indicated that cracking and strength reduction due to seismic loading can decrease the durability of reinforced concrete frame in post-earthquake fire scenarios. However, the durability of steel frames has no significant relationship with the seismic loading and their durability are almost the same in the fire and post-earthquake fire scenarios.

Assessment of Near-Fault Ground Motion Effects on the Fragility Curves of Tall Steel Moment Resisting Frames

Abstract: Nowadays it is common to use the fragility curves in probabilistic methods to determine the collapse probability resulting from an earthquake The uncertainties exist in intensity and frequency content of the earthquake records are considered as the most effective parameters in developing the fragility curves The pulse-type records reported in the near-fault regions might lead to the major damages in the structures having moderate and long periods since response spectra of near-fault ground motions within the long period range are different from those of the far-fault ground motions In the present study, the influence of this type of earthquake records on the fragility curves of the steel special moment resisting frames, SMRFs, was examined The results indicated that the median value of the collapse capacity (ieŜCt Parameter, which defines the earthquake intensity leading to the collapse of the structure in half-set of the chosen records) due to near-fault ground motions was 76% that of the far-fault records for the ten-story example SMRF

Experimental Strengthening of Damaged and Un-Damaged RC Frames with Ultra-FRC Composite Layers

Abstract: FRC concretes with high strength are practical material for strengthening existing particularly damaged concrete structures and able to dissipate seismic energy. The main purpose of this paper was to using high strength-FRC concrete for strengthening the damaged and undamaged frames. The five experimental specimens were loaded laterally and vertical gravity loads, simultaneously. The first specimen was a reference without strengthening, but the second same specimen was strengthened. The other three specimens were initially were loaded up to 55, 75, and 100% of the maximum capacity of the reference specimen and prepared as damaged specimens. The damaged specimens were laterally and vertically loaded. The test results showed that ductility of the undamaged strengthened frame was 2.2 times that of the reference specimen, while these amounts for three strengthened specimens (55, 75, and 100%) were up to 110, 60, 15 increase compared to the reference. The maximum lateral capacity of second undamaged, third fourth, and fifth damaged specimens were 38 and 35, 16, 9% more than that of reference; while the significant increase of energy absorption from 1.28 to 2.37 times reference was observed.

Implementation of a New Macroscopic Shear Wall Element

Abstract: A new macroscopic four node reinforced concrete shear wall element is presented. The element is capable of considering the effect of wall opening without any divisions in the element. Accordingly, the opening may be located arbitrary inside the element. Furthermore, three degrees of freedom are suggested here at each node, totally compatible with the surrounding frame elements. The element is considered only for in-plane stiffness of the wall. Therefore, the surrounding frame elements are assumed to be assembled separately which provides a suitable modeling condition. The element consists of vertical springs, horizontal springs and a shear membrane shell. No rigid element is used in the assembly for imposing the bending action; however, the compatibility is achieved using the definition of shape functions. The element is developed and evaluated in linear applications. The results indicate that some major defects of other macroscopic shear wall elements are removed by the proposed element.