نشریه مهندسی سازه و ساخت
سال نهم شماره 1 (پیاپی 54، فروردین 1401)

In this article, lateral-torsional stability of axially functionally graded (AFG) non-prismatic beam with doubly symmetric thin-walled cross-section under transverse loading is investigated. Material properties of FG beam with variable cross-section are supposed to vary through longitudinal direction of the constituents according to simple power-law distribution (P-FGM). Based on Vlasov’s model and using small displacements theory, the governing equilibrium equations are derived through the energy principle for AFG web and/or flanges tapered I-beams. The differential quadrature method is then selected to numerically solve the resulting system of governing fourth-order differential equations with variable coefficients. In this approach, a non-uniform mesh point distribution (Chebyshev-Gauss-Lobatto) is used for provide accuracy of solutions and convergence rate. Finally, the lateral-torsional buckling loads are calculated by solving an eigenvalue problem of the obtained algebraic system. In the case of homogenous members with variable cross-section, the outcomes of this work are compared with the available benchmarks and there is an excellent agreement. Finally, the impacts of involved parameters such as boundary conditions, load height parameter, power law index and web and flanges tapering ratios on the non-dimensional lateral buckling load are discussed. The results of this research reveal that the impacts of non-uniformity in the cross-section and gradient index play significant roles on lateral-torsional stability behavior of tapered I-beams. Furthermore, the highest buckling capacity is acquired when the transverse load is applied to the bottom flange.

In designing a structure, due to the uncertainty in some parameters, it is necessary to ensure that the design is responsive to the design requirements. For this purpose, the theory of reliability is used. In this study, the reliability of the low-rise steel moment-resisting frame was evaluated based on performance levels. For this purpose, based on the Monte Carlo simulation method, a step-by-step process was presented to use it to calculate the steel moment-resisting frame reliability index for probabilistic constraints of plastic hinges limitation and inter-story drift ratio limitation at each performance level. Also, cross-sectional area, moment of inertia and plastic section modulus of members, modulus of elasticity and yield stress of steel, and gravity loading are considered as random parameters in this study. Finally, using the presented process method, the reliability of a three-story steel moment-resisting frame, which is optimized based on the performance-based design method, was evaluated. The results show that in some plastic hinges at the performance level of immediate occupancy, the probability of plastic rotation less than the acceptance criteria of this level is not desirable, while in other plastic hinges and performance levels, a suitable reliability index was obtained for the probabilistic constraint of plastic rotation constraint. Also, based on the results, it is very unlikely that the inter-story drift ratio of stories will exceed the limits considered at each level of performance.

The main need of sufferes in natural disasters, is to provide housing, especially to determine the place of temporary residence in critical situations. After the incident, it is not possible to provide suitable places for the injured immediately. Before such crises occur, proper planning must be done to determine the temporary residence so that the necessary infrastructure can be provided and in case of an accident in a crisis situation, it is possible to quickly set up camps for the injured. In this study, to determine the optimal location of temporary residence in Tabriz, various standards effect have been considered such as medical centers, fire brigade, faults, fuel stations, infrastructure facilities, worn-out tissue, watercourse complications. The desired standards were completed at first by experts and once again by experts in this field based on form of a questionnaire, then using the fuzzy hierarchical analysis method, the final weights of each standard were determined. Experts attributed the closeness to the worn-out texture and the second group of experts to the standard of avoiding faults the highest weight. That was important the avoiding standards to hazardous site and the river, for the both experts group. Finally, the last weights obtained the opinions of experts groups from fuzzy hierarchical analysis have been entered in Arc GIS software and the relevant maps that have been prepared using weight overlap in this research. The results show that before the incident, the western part of the city has suitable for temporary accommodation, and after the incident, the central part of the city is appropriate for settlement site. In addition, by comparing the vulnerability maps of Tabriz, the necessary locations for the construction of a temporary housing site were prioritized.

Progressive failure is developed by expanding a local initial failure from one element to another, which ultimately leads to the collapse of the whole structure or a large part of it. This phenomenon causes local damage in structural elements which can result in massive losses and significant damage. Ductility, continuity, and degree of structural expansion are among the parameters that play an important role in reducing such consequences. In this study, the behaviour of a scaled four-span steel frame, with concrete filled steel tubular columns (CFST), was evaluated under progressive failure by removing the middle column. This work was done using the finite element method in ABAQUS. This work was carried out by examining the effect of reinforced triangular plate, haunch and angle steel reinforcements, reduced section in flange and web as well as post-tensioned FRP cables along with sensitivity analysis. The findings indicated that among the proposed anti-collapse methods, the maximum yield strength, the maximum ultimate strength and ductility ratio belong to angle steel reinforcement with 140.24 KN, reinforced triangular plate with 259.6 KN and RBS with 21.16 method. However, in a comprehensive comparison, the method of adding reinforced triangular plate was the best anti-collapse method since it avoids damage to the columns. Additionally, the change in compressive and tensile strength of the concrete did not have much effect on the frame behaviour in the progressive failure. Moreover, the frame with non-concrete columns has a ductility ratio 3 times higher than SRCT case, although the frame with SRCT columns has a 14 percent higher yield strength.

The effect of liquid tanks shape on their seismic behavior considering fluid – structure and soil – structure interactions has been investigated in the current study. Basically, the tank is a structure used to store different types of fluid, and it is also widely used in refineries, sewage treatment plants and factories in the form of on ground and elevated tanks made from concrete and steel. Regarding the application of the huge dynamic and hydrodynamic loads on a tank at the time of earthquake and the great importance of the structure’s complete function continuity in the critical situations, it is highly important to study its seismic behavior. Among the different analyses, the seismic analysis of the tank is highly important because by investigating the results obtained from this analysis, a useful recognition of the quality of the tank’s behavior at the time of a real earthquake can be obtained. The equivalent rectangular and diamond and ellipticalburiedliquid tanks have been dinamicallyanalyzedunder Elcentro andManjil and Cape earthquakes simoultaneously in the longitudinal and transverse directions and the variousseismicparametersof the system such as thewave maximum height,wallmaximumdrift,concrete maximum tensile stresses and soil maximum compressive stress have been compared with eachother in above mentioned cases in the current research. By study of the computed results of current research, it was revealed that the liquid tanks shape has a considerable effecton their seismic behavior in the same conditions. It also was revealed that the effecttype of variousshapes is not same on the various seismic parameters.

Before the occurrence of Northridge earthquake,it was believed that the conventional connections used in steel moment frame structures were capable of tolerating the great plastic rotation of 0.02 radians and above without a significant reduction in strength.Observation of the applied damages by the 1991 Northridge earthquake showed that the main damage was in the area of welded connections.For this reason and the weakness in welded connections,the idea of using the link area in steel connections has been proposed, which can be easily replaced after an earthquake.Therefore, in this study,the box-shaped linking element has been developed,which acts practically independent of the applied load and has a steady hysteresis behavior under tension and compression.In this research, laboratory numerical study has been conducted RBS connection using the box-shaped replaceable link at the joint formation site.For this purpose,first a validation based on a laboratory model has been performed in Abaqus software.In the following, models based on the validation paper have been developed and the idea of using a box-shaped link has been proposed.Two models have been developed and analyzed in Abaqus and two laboratory models have been examined experimentally.Two links with different details were placed in the area of reduced joint to reduce the beam section.The results show that very high stress concentration occurs in the box-shaped link area and other parts of the beam and column elements of the stress surface are less than the yield point and energy absorption is done in the box-shaped link area.It was also found that according to the maximum rotation recorded in the specimens and according to the AISC regulations, specimen A is one of the allowable connections in the middle frame and, model B has the necessary conditions to be placed in the permitted connections in a special moment frame (tolerating rotation of above 0.04 radians).

Due to the importance role of the behavioural characteristics of the project manager in construction projects and the need for effective and useful communication with other stakeholders of the project, studies have not comprehensively examined the behavioural competencies of the project manager and the lack of a practical model in the Iranian construction industry to select a capable project manager feels tangible. This research is on a more systematic approach to address the behavioural capabilities of the project manager by considering the factors related to his behavioural variables to evaluate the behavioural capabilities of the project manager. Using a multi-stage research process, including extensive literature review, analysis and a combination of important factors in the behavioural competencies of project managers, the development of an analytical network model (AHP, TOPSIS) was considered. This model would be a decision support tool for the employer organization to compare project managers according to their behavioural competencies by creating a database. This protects construction companies from the effective challenges posed by the performance of project managers and helps them to evaluate the performance of their project managers. It also enables project managers to focus on their efforts to address behavioural practices to improve their project performance.

The present study investigates the influence of the number, material and configuration of bolts on rigid bolted connections under fire. In this study, 6 steel rigid bolted connection specimens with end-plate were modeled as A490 and A300 in ABAQUS software and they are assessed under fire by nonlinear dynamic analysis. By examining the results, the highest stress in the bolt is occurred with material A300. This is due to the lower yield stress of the A300 bolts than to the A490 because the A300 bolts yield at lower stresses and, as they enter the plastic deformations, cause the steel plates to become more involved and the values Increase the stress, especially around the bolt holes. Sample stresses CON.M22 8B A490 and CON.M18 12B A490 T2 are different about 4%. This displacement value for specimens with A300 bolt materials increses to 240 MPa which is equivalent to the yield stress of material A300. The strain with material A490 for CON.M22 8B A490 and CON.M18 12B A490 T2 samples is about 59% and for CON.M18 12B A490 and CON.M22 8B A490 T2 samples is about 67%. The strain with materials A490 for CON.M22 8B A490 and CON.M18 12B A490 T2 samples is about 38% and for CON.M22 8B A490 and CON.M18 12B A490 samples is about 20%. Specimen displacement for bolts with materials A490 whereas this value for specimens with A300 bolts for CON.M22 8B A300 and CON.M18 12B A300 T2 specimens had the highest and lowest vertical displacements, respectively, which is about 25% difference. In the CON.M22 8B, CON.M18 12B and CON.M18 12B T2 samples with different bolt materials, the percentages are 15, 24 and 44%, respectively. The use of materials with lower yield and rupture stresses caused yielding in the lower temperature and reducing the resilance of structure under fire.

During the progressive collapse of structures, reinforced concrete (RC) beams must sustain large displacements which are not considered in usual design procedures. Regarding the extensive studies during the recent years, compressive arching and catenary actions are introduced as the main resistance mechanisms against progressive collapse. Despite the extensive studies, there is still a running debate on reliable estimation of the capacities and ultimate resistance of RC members against progressive collapse. Thus, in the present study, a simple and practical analytical method is developed to estimate the ultimate compressive arching capacity of RC beams under large displacements due to progressive collapse. The proposed method is developed based on the membrane action in RC slabs and analytical calculation of lateral stiffness of the structural system. Despite the available methods in the literature, the ultimate arching capacity of RC beams is obtained based on a single-stage procedure. The capability of the introduced method is evaluated utilizing a comprehensive laboratory database, including 99 experimental studies in the technical literature. According to the performed evaluations, the proposed method provides a reliable framework to estimate the arching capacity of reinforced concrete beams in large displacements. Any change in failure mode from flexural action to shear mechanism and increasing the rigidity of the connections leading to an improvement in lateral stiffness could reduce the accuracy of the proposed method.

The present study was an attempt to investigate the effect of direct and uniform magnetic field on concrete-steel rebar bond strength in fresh and hardened concrete specimens containing quartz aggregates using pull-out test. Moreover, compressive strength test was performed on all magnetic and non-magnetic specimens at 28 days of concrete age in order to investigate the effect of compressive strength of concrete on bond strength. In the present study, a concrete mixture containing smart quartz aggregate was designed for a compressive strength of 30 MPa, . The water to cement ratio was selected to be 0.4 for concrete mixes. The method of fabrication and processing of samples was performed according to ASTM C192 . Accordingly, first one-third of the fine-grained and one-third of the mixing water were added to the mixer with one-third. The remaining cement and water were gradually added to the concrete mix. At the end, superplasticizer was gradually added to the concrete mix for 1 to 2 minutes and then the concrete mixing process was continued for 3 minutes. In order to prevent the magnetic field from being absorbed by the concrete mold, concrete samples were sampled in plastic molds. Concrete samples were covered with a wet sack at a temperature of 20–22 ° C for 24 hours and then removed from the formwork and stored under moist conditions until the experimental age. The device used in this study is able to convert electricity into a uniform magnetic field with an intensity of 0.5 Tesla. According to the results, the failures in all specimens are of slip type with no fissure cracks. The results also showed that applying a magnetic field to the concrete can lead to enhancement of bond strength by about 55% and 73%, in 14 and 20 mm rebar respectively.

One of the most important basic needs of the affected people after natural disasters such as floods and earthquakes is to live in a safe and suitable place. The costly and time-consuming process of establishing permanent housing will provide temporary residence. Using of the disadvantages of common materials, such as steel and concrete, due unconventional extractions, exorbitant construction and production costs, and irreparable environmental damages, the need to build temporary shelters, fast construction, recyclable, environmentally friendly, low-cost and biodegradable natural resources, like bamboo, is very much felt in our beloved country. Bamboo is used as a structural material in more than 60 countries in the world, which fortunately, its species can also be found in our country. The purpose of this study is to investigate the mechanical properties and structural efficiency of the native Iranian bamboo species with the local name Kara and also design and propose a temporary green structure resistant against lateral loads. The Chevron brace was used as a lateral bearing element and hose-clamp connections were also employed. The results of compression, tensile, shear, shear with hose-clamp, and bending test parallel to the fibers were calculated to be 66.5, 103.42, 2.63, 2.73, and 137.96 MPa, respectively. The results of the analysis and design of the constructed model also indicated that the calculated demand under all load combinations in the elements of columns, beams, and braces for bending and axial stresses was more than 97%, and for shear stresses was more than 57% lower than the allowable capacity of the regulations

This study aims to investigate the effectiveness of engineered cementitious composite (ECC) as a ‎means to enhance the seismic performance of short columns. Eleven ECC short columns and one reinforced concrete (RC) short column were ‎designed and tested under lateral cyclic loading with different fiber volume fractions(0 -1.5%) and shear ‎aspect ratios(3-7). The influence of fiber volume ‎fraction, and shear aspect ratio on crack pattern, hysteresis behavior, energy dissipation, failure ‎modes, and length of yielding region is presented and discussed. The test results show replacing ‎conventional concrete with ECC can effectively improve the seismic behavior of short columns. ‎Further more , ECC short columns show excellent ductility and damage tolerance. Results shows ‎larger plastic hinge lengths were obtained with an increase of aspect ratio and fiber fraction‎.The influence of fiber volume ‎fraction, and shear aspect ratio on crack pattern, hysteresis behavior, energy dissipation, failure ‎modes, and length of yielding region is presented and discussed. The test results show replacing ‎conventional concrete with ECC can effectively improve the seismic behavior of short columns. ‎Further more , ECC short columns show excellent ductility and damage tolerance. Results shows ‎larger plastic hinge lengths were obtained with an increase of aspect ratio and fiber fraction‎