JOURNAL OF STRUCTURAL AND CONSTRUCTION ENGINEERING
Year:2019 | Volume:6 | Issue:2 (24) |Papers Count:14

I am glad to announce publication of Volume 6, No. 2 (2019) of Journal of “ Structural and Construction Engineering” . Journal of “ Structural and Construction Engineering” publishes by Iranian Society of Structural Engineering (ISSE) which is one of the leading institutes in the region. ISSE’ s mission is to create an appropriate platform for the purpose of scientific, technical, research, educational communication, and scientific exchanges and competitions between researchers and specialists in structural engineering and related fields, and integration of the activities in the field of structural engineering and construction, the expansion of the frontiers of science and professional and public awareness in MEA region. To do so, ISSE established a leading journal and will publish it four times a year. Journal of “ Structural and Construction Engineering” provides a forum for a broad blend of scientific and technical articles to reflect the evolving needs of the structural engineering and construction communities in the region. The scope of “ Structural and Construction Engineering” encompasses, but is not restricted to, the following areas: structural engineering; earthquake engineering; structure-soil interaction; structural fire engineering; blast engineering; structural reliability/stability; life assessment/integrity; structural health monitoring; structural dynamics; experimental modelling; performance-based design, construction management. “ Structural and Construction Engineering” also publishes review articles, technical notes, and a diary on national and international events related to any aspect of structural engineering. “ Structural and Construction Engineering” has a continuous open call for papers. Backed by the reputation of the members of its Editorial Board, we will continue to push for excellence in the contents and quality of this journal. From now on, all published articles in JSCE will get Digital Objective Identifier (DOI) which is very important for indexing and etc. In addition, JSCE is an Open Access (OA) journal that is available online to the reader without financial, legal, or technical barriers other than those inseparable from gaining access to the internet itself. We also are proud to announce that Ministry of Science, Research and Technology of Iran gave grade A to JSCE (similar grade to ISSE) in the last year evaluation. I wish you enjoy reading this issue of “ Structural and Construction Engineering” and I invite you to contribute to the success of this journal by submitting your articles.

The sensitivity of slump flow of self-compacting concrete containing metakaolin to its ingredient materials and mixture proportions, necessitate the use of high accuracy models to guarantee both estimation and generalization features. Therefore this paper investigates the potential of multivariate adaptive regression splines (MARS) and model tree (MT) approaches in prediction of slump flow of self-compacting concrete. Total of 117 data collected from the several published literature were used in present work. The data used in proposed models are arranged in a format of eight input parameters including cement, coarse aggregate, fine aggregate, water, metakaolin, super plasticizer, binder and maximum size of aggregates (Dmax) and one output as slump flow. To evaluate the precision of the models, a comparative study has been performed in terms of RMSE, R and MAE indices. The results of training and testing datasets of the techniques are compared with experimental results and their comparisons demonstrate that the MARS and MT models have potential to predict concrete properties with great precision. Performed sensitivity analysis to assign effective parameters on slump flow was indicating fine aggregate and metakaolin is most effective variable for modeling and prediction in this type of the self-compacting concrete using MT technique in this study.

Today, instructions for seismic rehabilitation of existing buildings are widely used for seismic performance evaluation of existing buildings. Moreover, nonlinear structural analysis methods are permitted for seismic design of new buildings in recent versions of seismic design codes in some countries, such as Iran. Therefore, match compliance of conventional design codes with instructions for seismic rehabilitation of existing buildings is of great importance. On the other hand, four different analysis methods are available in seismic rehabilitation instructions that compatibility of these analysis techniques can be evaluated. In this regard, seismic performance of three buildings with steel moment frames as lateral load resisting system with 4, 8 and 12 stories that were designed previously according to conventional seismic design codes with two levels of ductility (Intermediate and Special) were evaluated using seismic vulnerability assessment instruction in Iran (Code No. 360) by means of four analysis procedures. Analysis results indicate that conventional seismic design codes are more conservative than Code No. 360. In other words, design of steel moment frames with conventional design codes leads to stronger beams and columns. This phenomenon can be due to controlling lateral interstory drift and weak beam-strong column criterion in moment frames that control final design of these structures.

Usually during moderate and strong earthquakes, if the space between the adjacent structures is not enough, structural pounding will occur which is due to the out-of-phase vibration of the structures regarding the differences in dynamic properties of the structures. Different factors contribute in the state of structural pounding, and researchers have already studied several factors including the space between two structures, the type of pounding, force transmission means, reducing the pounding damage and etc. Record is one of the factors which can affect the structural pounding, and one of the most crucial parameters of record is strong ground motion duration which its analysis is very important in the quality of structural response. In this study, effect of strong ground motion duration on the adjacent structural pounding is investigated. To do so, steel moment resisting frames in 5, 8 and 12 floors are designed which are paired together in three forms of 5-8, 5-12, and 8-12 models for nonlinear time history analysis. In this analysis, 15 records that include three intervals for strong ground motion duration are being implemented (0 to 10 seconds, 10 to 30 seconds, 30 seconds and more). Besides, in order to obtain the pounding force between structures, linear elastic elements are used in floor levels. Results show that in structures in which the space equal to 1% of their heights are not considered, with increasing the strong ground motion duration, maximum structural pounding will also increase with a smooth gradient, and for the structures with space equal to 0. 5% of their heights, this increase rate is more compared to the structures with no space.

Soil-structure interaction expresses the difference of structural responses between the actual and theoretical rigid based conditions, and depends on the stiffness, mass and damping of soil and structure systems. Nowadays, moment-resisting frame is one the most applicated structural systems. Ductility of these frames is due to the flexural yielding of beams, columns and the shear yielding of panel zone of columns. The influence of modeling beam-column connections and soil-foundation-structure interaction on the seismic responses of 10-story intermediate steel moment-resisting frames that located on the soil type IV with various shear wave velocities (150 and 80 m/s) and soil type II (with shear wave velocities 56 m/s) is studied in this paper. Prequalified welded flange plate connections (WFP) are used in these buildings. For this purpose, several 2D finite element models are developed using OpenSees software by assuming three conditions such as models with considering soil and beam-column connections effects, models with considering soil and without connections, models with fixed based and without considering connections. The maximum responses of the studied frames are calculated and compared with nonlinear time-history dynamic analyses. The numerical results show that in the models located on soil type IV, considered connections, SFSI, or just soil, the maximum lateral displacement and maximum inter-story drift are more, compare to models without connections and with fixed based conditions. In the models rested on soil type II, some of these parameters are reduced. The maximum base shear of structures is reduced in the mentioned models.

Liquid storage tanks are widely used to store different types of liquids such as petroleum products. Any failure of these structures may cause serious consequences. Near-fault ground motions which may have severe velocity pulses have a destructive potential on these facilities and can be represented by analytical pulse-like functions. In this paper, a parametric study is carried out to investigate the seismic behavior of liquid storage tanks under pulse-like excitations. For this purpose, the liquid storage tanks are modeled using equivalent mechanical models and then dynamic analyses of the models are done using pulse-like excitations. The selected analytical pulse-like excitation is based on the modified Gabor Wavelet transform with four main characteristics: amplitude of the signal, period of the signal, shape (phase) of the signal, and the number of pulses. The effect of each pulse parameter as well as the effect of tank aspect ratio on the various response parameters is investigated. The obtained results indicate that the sloshing motion of the liquid near the free surface is affected more by equivalent pulses with long periods while the base shear and overturning moment are affected more by equivalent pulses with short periods. It is also seen that by increasing the number of pulses, the response parameters increase considerably when the pulse period is near the natural period of the convective mode. However, changing the phase of input signals in order to produce symmetric or anti-symmetric pulses has not any noticeable effect on the obtained results.

Concrete ground tanks are widely used in storing water, sewage, oil, toxic chemicals and other liquids. Depending on their type of use, they are usually in the category of very important structures of lifelines; Therefore, the dynamic analysis of liquid storage tanks is one of the most important issues in earthquake engineering. On the other hand, the seismic behavior of the storage tanks and its interaction with liquid is very important. In this study, the water medium is modeled using smoothed particle hydrodynamics method and tank’ s structure modeled by finite element method. The smooth particle hydrodynamics, which is a meshfree method, has many advantages over other traditional grid-based methods. For verification purposes, the modeling accuracy was compared with the available experimental and numerical results, the reasons and parameters that were effective on selecting the records were expressed, and then the time history analysis was performed on the modeled storage tank including records with different frequency content. The parameters of sloshing height, acceleration at the top of the tank’ s wall, base shear, force per unit width and wall displacement were obtained for comparison. Finally, the effect of frequency content was studied considering the effect of water-structure interaction on the tank. The results showed that a record with low frequency content results higher sloshing height, while a record with moderate frequency content will cause larger responses on the tank’ s structure despite of its lower sloshing height. The study also proved that the dominant frequencies of sloshing increases with decreasing frequency content of earthquake.

Durability of reinforced concrete (RC) structures has been increased using different additives under corrosive environments in the recent years. In the present study, 0, 0. 5, 1 and 1. 5 percentage of nano clay particles were substituted as cement. Therefore, 24 RC beams divided in three groups after 28 days of curing. The first group consists of 8 beams which were tested after 28 days of moist curing. The second and the third groups consist of 8 beams in each group, which were tested after 6 months exposure in chloride solution and wetting and drying cycles, where the third group beams were additionally under service loads. Also, compressive strength and water absorption of the mixtures were evaluated at different ages. Results showed that the addition of nano-clay particles considerably reduces the compressive strength of concretes which consequently decreases the flexural capacity of the beams. In addition, nano-clay particles reduce the half-hour water absorption and increase 24-hour water absorption. Also, results showed that the wetting and drying cycles of chloride solution for 6 months reduces the flexural capacity of the beams, but service loads reduces the negative effect of the exposure. Also, the beams containing nano-clay particles showed better performance under chloride attack.

In recent years, the framed tube system has been known as the most efficient structural system for the high-rise buildings. The entire lateral resistance in the framed tube structures is provided by closely spaced exterior columns and deep spandrel beams. A framed tube building suffers from the shear lag effects, which cause a nonlinear distribution of axial stresses along the face of the building so that the axial stress in the corner columns increases while it decreases in the interior columns. Shear lag depends on the perimeter columns size and spacing and flexibility of the spandrel beams. In this study, the influence of soil structure interaction (SSI) on shear lag phenomenon and deformation of reinforced concrete framed tube structures have been investigated and the results of linear and nonlinear analyses have been compared. In addition, P-Delta effects on some of the nonlinear static analyses have been considered and the sequence of plastic hinges formation has been investigated. The influence of SSI, the formation of plastic hinges and P-Delta effects have been determined by analyzing a 50-story reinforced concrete framed tube structure under seismic loading. The results show that SSI decreases shear lag and increases deformations of the structure. It also indicates that the formation of plastic hinges is so effective in deformation of the top stories and distribution of axial stresses in the top half of the building, and how P-Delta effects are important in deformation and strength of the framed tube structures.

Fibre or recycled material used in the concrete improves resistance, ductility, and durability of concrete. Concrete has fire-resistant properties but the most worrying thing about reinforced concrete structures during the fire is related to rebars. Therefore, there is a suggestion about use of alternative materials such as recycled metal spring in order to reduce above mentioned risks. In this paper, we conduct laboratory study to assess performance of concrete containing recycled metal spring while using volumetric amounts of 0. 2, 0. 4 and 0. 6% at temperatures of 25, 100, 250, 500, 700 and 900 degrees Celsius. Furthermore, compressive strength and tensile strength of the most optimal combination of spring in the concrete are compared with concrete containing steel fibre and polypropylene. The results show that spring used in the concrete improves compressive strength and tensile strength. But the more the spring is used in the concrete, the more the resistance is reduced. Therefore, if the spring with 0. 2 volume percent that is considered as the most optimal combination percentage is increased by 3 times, it increases compressive strength and tensile strength. Furthermore, the optimal compressive strength of spring in different temperatures is about 2 – 3 times of steel fibre and polypropylene and its tensile strength is close to strength of steel fibre. Fibre used in concrete reduces width of the cracks created after the test by 3 times.

Concrete rectangular columns reinforced with longitudinal spirals are new types of RC columns which their behavior has been investigated by researchers in recent years. These researches are limited to some experimental studies which investigate the effect of different configurations and layouts of the spirals within the cross-section of these columns on the bearing capacity and ductility. In this study, for the first time, the behavior of these columns has been simulated using numerical approaches. Finite Element (FE) models of these columns were developed using ABAQUS/CAE/Explicit v. 2016 and then verified against available valid experiments in literature. Subsequently, by performing several sensitivity analyses using verified EF model, the effective parameters on bearing capacity of this kind of columns were detected. By changing the value of these parameters in rational ranges, a comprehensive parametric analysis was done after that using FE models in order to produce necessary input data for training an Artificial Neural Network (ANN). This parametric study was performed because of the lake of sufficient available experimental data. The developed ANN was verified against some experimental data. Finally, in addition to ANN, a regression analysis was performed to obtain a polynomial function can predict the bearing capacity of these type of columns. Obtained results demonstrate that the combination of FE and ANN is an effective method to predict the load bearing capacity of RC columns with longitudinal spiral reinforcements and have a good agreement with the results of regression analysis.

The most important parameter for determining the level of performance and breakdown of buried pipes in the case of earthquake is the maximum value of strain. Vital arteries code, while studying the maximum value of strain, have addressed the seismic behavior of buried pipelines. Static methods don’ t have the ability to consider the transient strain effect in their results, so it is necessary to consider another method in determining maximum strain. From the suggested methods to determine the maximum strain in buried pipes during earthquake is nonlinear dynamic analysis of pipes and the soil around it. In this study, using Abaqus software, we have presented a method to calculate the maximum strain of buried steel pipes for gas transfer in soil according to the parameters including earthquake energy like Arias intensity and Housner spectral intensity and using accelerograms. Analyses performed according to dynamic method is nonlinear and modeling has been done for three different lengths of gas transfer buried steel pipes in soil, with the internal pressure using different accelerograms for types of soil in Iran 2800 code. Then, in order to present a united relation to show the relationship between maximum strain of steel pipes and parameters including earthquake energy, in order to apply the considered relation for buried pipes with different lengths and different soils, we have used T/L parameter and the values of a and b (coefficients of fitted diagrams) in each section is expressed according to this parameter.

Due to the 1994 Northridge earthquake, many of welded steel moment resisting frames (WSMRF) collapsed in the connection area of the beam to a column. The damage in WSMRF, which was contrary to the expectations of the engineers, changed the attitude of the WSMRF. Thus, engineers decided to introduce more ductile and detailed connections. Post-Tensioned Connection (PTC) is one of the new connections proposed by them. PTC includes high strength, pre-tensioned cables to create self-centering properties and energy dissipation to control plastic deformation. In this study, the numerical modeling of the PTC was performed using the ABAQUS finite element software. In addition to verify the model accuracy with the experimental results, 6 types of the connection were modeled and the effect of some parameters including the use of high strength steel (HSS) angle, the application of angle with unequal leg length, the use of stiffness for angle and the effect of the ratio of length to thickness on connection behavior under cyclic loading are investigated. In the range of models of this paper, the results show that the use of HSS for an angle causes a slight increase in flexural strength and capacity in lateral load bearing. Also, results demonstrated that the use of an angle with an unequal leg length does not affect the behavior of the connection. The use of stiffness for angle increases bending strength, capacity, energy dissipation, initial and inelastic stiffness and durability. Also, the reduction of the gage length to the thickness (g/t) from 4 to 3. 6 would increase the energy dissipation of the connection, so that the energy dissipation in the connection with a lower g/t ratio is 17% higher.

One of the drawbacks of the mentioned connections after Northridge and kobe earthquakes was the destruction of beam after earthquake, difficulty and non economical displacement of the beam. Several studies are being carried out on a variety of materials and systems that dissipate the seismic loading effects in order to improve the seismic performance of steel frames. By placing dampers in the beam column connections, damage to the beams and columns, which are very difficult to replace after an earthquake, was prevented during an earthquake. During the design process of dampers, in order to concentrate the earthquake loads on the damper, it was manufactured intentionally with a lower strength than the beams and columns. Through this, beams and columns are protected from damage by utilizing the energy absorption capacity of the damper. Slit damper is a plate or a standard section with a number of slits in the web. The damper is attached to the beam by bolting a plate on the damper under the flange of the beam. In this study first compared slit steel damper connection and connection with the reduced beam section (RBS) under cyclic loading. Some suggestions were provided for improvement of the performance of slit steel damper connection and for making its behavior similar to that of reduced beam section connection and transforming it to a connection which can be used in the special bending frame; and these suggestions include increase in the thickness and number of stripe and decrease in the height. the results and simulations showed that increasing in the number of strips, the increase in thickness and decrease in the height of the SSD damper affects significantly the performance of SSD connection.