JOURNAL OF STRUCTURAL AND CONSTRUCTION ENGINEERING
Year:2019 | Volume:6 | Issue:1 (22) |Papers Count:13

Regarding the importance of seismic performance and also the problems of moment connections, representing an accurate and efficient scheme to reinforcing could be useful to eliminate these problems. Assuming that (CJP) welds between top flange plate and column face have poor quality or strengthened like fillet welds, the need of reinforcing becomes obvious. For that reason, by using triangular stiffener plate for joining to column face and top flange plate, the seismic behavior could be improved and possible to opt as a reinforcing scheme. To prove that, the experimental specimen was created and investigated. Then, validation was employed with the numerical model of one. By applying the basic concepts of the mechanic of materials, the design of triangular plate was expressed. Along with that, sensitivity analysis with studying on several numerical models carried out to show the accuracy of the proposal procedure design. Moreover, some factors effect on the seismic behavior of this scheme including numbers of stiffener plate, the thickness of stiffener plate, and the width to thickness ratio of box column. While using the box column in literature is rare, it replaces with H-shape column mostly in some countries like Iran. So, this paper tries to consider these cases to cover all aspects of this reinforcing scheme. The results showed this procedure could enhance the seismic behavior of defective moment connections.

Designing structures against progressive collapse is an important part of the building design. However, some guidelines such as GSA and UFC holds implications for reducing the risk of progressive collapse of structures, but because the nature of the loads or events that cause damage are not well defined and the performance of building components during progressive collapse is not well understood, It is difficult to predict the trend of increasing damage. In this study, using the membrane action of the slabs, the effect of concrete strength and slab thickness on preventing the progressive failure of RC concrete slabs is investigated after the sudden removal of an internal column. Progressive collapse in the designed slabs was simulated by the sudden removal of an internal column and the slab capacity was calculated in the presence of compressive membrane force for different concrete strengths and slab thicknesses. Load carrying capacity for an enlarged span of the slab due to the sudden removal of the middle column has been investigated for various models. The results of this study showed that the membrane action of the slab, which is often not considered in design, can greatly prevent progressive failure of the slab and structure. By increasing the strength of the concrete and the thickness of the slab as well as the minimum recommendation of the regulation, the capacity of the slab can be considerably increased after the sudden removal of the middle column.

Researchers in the construction industry have shown great interest in rheological and mechanical properties as well as durability of fiber reinforced self-compacting concrete (FRSCC), however, its behavior under torsional cyclic loading, has rarely been studied. In the present experimental research, behavior of fiber reinforced self-compacting concrete under cyclic torsional loading was studied. T-shaped samples consisting of a horizontal beam made of FRSCC and a vertical shaft were made. Horizontal beam was fixed at both ends to a rigid base and cyclic loading was applied to the end of the vertical shaft causing a cyclic torque around the horizontal axis of the beam. The vertical shaft was reinforced by longitudinal and transverse bars so that it could not collapse at the time of loading. By plotting the hysteresis diagrams, the torsional strength and energy dissipation of each sample specimen were investigated. Self-compacting concrete C50 class and Hooked End Steel Fibers with length to diameter ratio of 62. 5 and different amount of 0, 0. 25, 0. 5 and 0. 75 percent by volume were used. Results showed that the mixture containing 0. 5% fibers had the highest energy dissipation of 3. 87 times that of control mix with no fibers, and maximum torsional strength of 2. 46 times that of control mix.

Due to the growing population growth in cities, the use of injection technology in the ground improvements, construction industry, geotechnical and geological engineering is increasing day by day. In this regard, the grout and its additive play a very important role in terms of injection conditions. In this research, viscosity and rheological measurements of grout using the viscosimeter of the model (DV-II + Pro) as well as the physical criteria of the grout, including shrinkage, specific gravity (Gs), acidity (pH) on the cement base grout with the chemical additive like sodium silicate, kaolinite as mineral additive, cement and water were investigated. In this research, various grout compounds containing various percentages of sodium silicate, kaolinite and water were prepared. The results show that cement, kaolinite and sodium silicate have a reverse effect on the viscosity of the grout. If the amount of soil specific soil is acceptable and the soil acidity is more than 11, which is very suitable for injection operations. Also, the effect of various sodium silicate percentages on the binding properties, specific mass and gravity of acidity were investigated, and the results are recommended for geological and geotechnical engineers especially people who are working ans studying in this field.

Structural damages and subsequently considerable economic losses that ever made in catastrophic seismic events caused reaserchers and codes gradually move from prescriptive design to performance-based design. Seismic fragility analyses are one of the most important tools in performance-based seismic design of structures that lead to production of fragility curves and functions. Fragility function is a capable tool for probabilistic assessment of the seismic vulnerability of the structures. In this study, in order to assess seismic vulnerability of corrugated steel shear walls and compare their seismic vulnerability with simple steel shear walls, fragility functions have been developed and fragility curves have been constructed. In this regard, the effect of the corrugation angle has been studied in corrugated models. Construction of these curves has became feasible through conducting incremental dynamic analyses. For this purpose, inter-story drift and peak ground acceleration have been used as damage measure and ground motion intensity measure, respectively. Assessment of resulted curves show that in low seismic intensity, probability of damage in corrugated models is reduced by increasing the corrugation angle; while, in high seismic intensity, probability of damage in corrugated models has been increased by increasing the corrugation angle. On the other hand, results indicate that corrugated models have more appropriate seismic performance than simple model in low seismic intensity.

Structural health monitoring is an economical and reliable strategy for infrastructure condition assessment. In recent years, researchers have tried to propose algorithms based on statistical pattern recognition techniques. Studies show these algorithms can be successfully used to detect structural damage. Variability of operational and ambient conditions during data acquisition should be considered as an important factor in applying statistical pattern recognition methods in practical applications. This paper studies the efficiency of statistical pattern recognition methods on the damage detection of structures under various operational and ambient conditions. The data is obtained from an experimental study on an eight degrees of freedom mass spring system. Ambient vibration is applied to the mass spring system using random excitation. In order to simulate various ambient conditions, the amplitude level of the input force has been varied. By applying the statistical pattern recognition methods, the ability of these methods to damage detection under various ambient conditions is discussed. Two common approaches of statistical pattern recognition are considered. These approaches are autoregressive model accompanied with using control chart and Mahalanobis distance for outlier analysis. Results show the importance of considering the statistical pattern recognition methods for structural damage detection under various operational and ambient conditions.

Connections pipe pile to cap beam in steel bridges have important roles on structure strength affecting lateral loads such as earthquake. One of the most important strategies are to translate plastic hinge from connections to the other places in structure. In this study four types of composite steel connections and a direct welded connection modeled and analyzed in finite element ABAQUS software. After verification of the real model using available experimental data, the other models are made. The models under cyclic loading protocol SAC was analyzed and the results were compared. The results of this study indicated that the using composite connections, increased shear capacity and improved its performance. In addition, the obtain results show that infill concrete strenght doesn’ t have effects on shear capacity and ductility of steel bridge. The results indicated that using composite connection between pipe pile and cap beam translate plastic hinge from connection to pile area. Also, the results show that increasing composite length improved the ductility of total steel bridges. Also, regarding to results of this study, it seen that buckling in model with welded connection occur on surface between pipe pile and cap beam. However, in the models with composite connections the buckling translated from connection to pile area.

Shear failure plays a significant role in the seismic behavior of reinforced concrete (RC) structures. Generally, nonlinear analysis of the beams and columns in concrete structures is based on the flexural behavior of the members, and shear effects are generally ignored. Although in such an analysis, only the flexural behavior of members is considered, experimental results reveal the likelihood of the failure of RC members before reaching the ultimate flexural capacity. In this paper, a numerical model including rotational springs was developed to simulate the effects of the shear capacity of beams and columns based on material failure mechanisms. In order to evaluate the accuracy of the proposed model for beams and columns, the results gained by the nonlinear analysis were compared with the experimental results, which revealed a good agreement of the results predicted by the proposed model with those of experiments. Furthermore, the proposed model was assessed at the structural level in terms of performance, and to do so, an RC frame was investigated in two different modes: a) analysis using the proposed model considering shear effects and b) analysis based on the proposed model ignoring shear effects in the members. The obtained results suggest the importance of taking the effect of shear into account in predicting the nonlinear behavior of frames by the proposed model which may present an alternative to common methods.

Believing in the fact that an activity can be performed through several methods or states, or that there may be several executive states for activities with different numbers of resources in real conditions, the scheduling obtained from different methods with different combinations of time, resources, and quality need to be evaluated and optimized. These are referred to as project scheduling problems with multistate resources. On the other hand, application of the theory of constraints to project management has led to the development of a novel approach in project planning and control known as the critical chain. The present paper seeks to use the critical chain technique and simultaneous time-cost-quality trade off. In this study, the multi-objective problem of time-cost-quality trade off has been solved using the high capability of the multi-objective particle swarm algorithm in optimization and the critical chain technique, so that the most appropriate sequence and executive state of activities is found such that time, cost, and quality are optimized and close to reality. The optimization algorithm programming was coded in the MATLAB software, and the target results were extracted. For evaluation of the proposed model, two case studies with 7 and 18 activities have been solved. Furthermore, a project with 60 activities where the time-cost-quality trade off had been established were used for validation of the proposed algorithm, and new results were extracted. The results demonstrated that the developed algorithm has had correct, proper performance, in such a way that it is capable of generating several Pareto solutions with different time, cost, and quality values. Furthermore, the results have been reported separately based on the best time, cost, and quality, which makes it possible for the project managers to select the better solutions given their priorities in the project.

Civil engineering structures as well as office or apartment building are affected by earthquakes. In some buildings, few or no walls are provided at the first story (pilot). In the structures with difference in story level, major problems is due to discontinuity of floor diaphragm that causes significant changes in period, stiffness and distribution of earthquake force. In this paper, using linear and nonlinear static analysis, time history and location of plastic hinge in short columns and beams, period, displacement, shear force, performance point and capacity spectrum and… , in 2, 4, 6, 8, and 10 story structures with story level difference are studied. The results show that the effect of level difference in short structures is obvious and by increasing the height difference, the effect of short column phenomenon is decreased and the performance point is increased.

Since it is very important to know the material's behavior to evaluate the nonlinear behavior of structures, it is necessary to know the tension stiffening phenomenon and its effect on the behavior of the reinforced concrete members to examine their behavior in tension. For a reinforced concrete member, the reinforcement confined concrete affects the member's behavior after being cracked in the spacing between two cracks, and the reinforcement rebar in the concrete member shows less strain than the bare rebar. This affects the width of cracks and the stiffness of the member under tension. In this research the experimental method is used to tensile behavior of concrete members reinforced by GFRP rebar therefore the effect of rebar type, reinforcement ratio and c/d ratio on the cracking behavior of ultra high performance concrete (UHPC) is evaluated. The results show that increasing the rebar cover to diameter ratio of all specimens, their initial stiffening increases before the cracking stage in concrete. Also, the tension stiffening effect does not change as the type of the rebar changes. Finally, the spacing of cracks, the way they are distributed and their behavior are discussed.

Uplift force has significant role on dynamic response of concrete gravity dams and also seismic response of dams in near field motion can be considerably different from those observed in the far field and the near – fault ground motions can cause considerable damage during an earthquake. This paper presents results of study aimed at evaluating the uplift force effects in the near-fault and far-fault ground motions on nonlinear dynamic response and seismic damage of concrete gravity dams including dam-reservoir-foundation interaction. For this purpose, 3 as-recorded earthquake records which display ground motions with an apparent velocity pulse are selected to represent the near-fault ground motion characteristics. The Shafaroud gravity dam, which is selected as a numerical application, is subjected to a set of as-recorded near-fault and far-fault strong ground motion records and three different distribution of uplift force are assumed. The results obtained from the analysis of the dam subjected to each fault effect are compared with each other. It is seen from the analysis results that the uplift force, which has influence on the dynamic response of concrete gravity dam-reservoir-foundation systems subjected to near-fault ground motion, as has the potential to increase damage in the dam body but at far-fault motion uplift force can be neglected.

Iran is located on Alpine-himalayan earthquake belt. Every few years destructive earthquakes happen in Various region of Iran which causes significant amount of material and human losses. Therefore seismic strengthening of buildings especially historical and old religious building, because of their cultural, historical, heritage and touristic values are of great national importance. The objective of this paper is to study the seismic behavior of a special method of retrofit of Urchin domes. This type of semi-conical masonry dome which are found in southern regions of Iran has not been structurally investigated before. As a model for this study the damaged Urchin dome of Imamzade Jafar shrine in Borujird under 2006 A. D (1385 A. H) Silakhor-Lorestan earthquake was investigated. The strengthening method used is by applying a layer of reinforced concrete (Shot-Crete) to the interior surface of the Urchin dome which was evaluated in this study. After sufficient field studies and measurement, the composite structure of the: Urchin dome, lower double layer spherical dome and the masonry supporting walls and pears were modeled using ABAQUS FEM software. The models were analysed and their frequency and dynamic behavior using time-history analysis (THA) were obtained and compared before and after the application of strengthening Shot-Crete layer. Finally by evaluating the results obtained from these studies, the causes of the failure of the tip of this dome was found to be the excessive acceleration at the tip of the dome and weakness and brittleness of the masonry material due to shearing forces. After strengthening the interior of the dome by a Shot-Crete layer the weakness and vulnerability of the dome under the applied earthquake will be significantly reduced.