نشریه مهندسی سازه و ساخت
سال هشتم شماره 4 (پیاپی 42، تیر 1400)

The construction of segmental precast concrete bridges is an increase due to its superior performance and economic advantages. This type of bridge is appropriate for spans within 50 to 250 m, known as mega-projects and the design optimization would lead to considerable economic benefits. In this study, a box-girder cross section of bridge superstructure with balanced cantilever construction method is assessed. The depth of cross section, thickness of top and bottom flange, thickness of webs and the count of strands of pre-stressed steel are considered as design variables. The optimum design is characterized by geometry, serviceability, ductility, and ultimate limit states specified by the American Association of State Highway and Transportation Officials (AASHTO) standard and AASHTO Load and Resistance Factor Design (LRFD) specifications. Genetic algorithm (GA) is applied for cost and weight optimization. To validate functionality of this algorithm, a real bridge constructed in the city of Isfahan, Iran (Esteghlal Bridge, completed in 2017) is optimized as a case study. The total of a 13% reduction in cost and weight of the bridge superstructure is observed. The cost optimization algorithm is run by considering different spans and relation between superstructure cost and span length is assessed. The efficiency of applying the GA in optimization of this kind of bridges is proved.

One of the most important manifestations of sustainable development in any country is the country's productivity of sustainable sources of income. In fact, sustainable income is the basis for sustainable urban development. In the current century municipal financing is one of the most important issues in urban management, and in our country there has always been a discussion and a place for the challenge. Accordingly, in this paper, the aim of presenting an optimal model for sustainable municipal income for construction projects is based on the use of decision-making methods and calculation of the parameters of effective parameters in the assessment of sustainable earnings in the municipality of Karaj city. In this regard, Delphi method was used to validate the validity of the questionnaire using SPSS software. Therefore, the criterion of Evaluation, judgment by a group of experts and based on completing the questionnaire and conducting interviews with accurate experts in providing financial resources and urban management. The ranking of effective measures in assessing income municipalities using the Hierarchical AHP technique was done in Super Decision software and language quantitative meter using the method the average FOWA weighted weight has been paid to prioritize earnings resources. Based on the findings of the research in the city of Karaj, among the sources of income studied by the FOWA method, it can be seen that the transitional tax option from the government to the municipality using the AHP method with a coefficient of 0/150 and in Riskiness with a coefficient of 0/166 and risk aversion with a coefficient of 0/144 with 9 indicators of the highest priority in the assessment of the supply of municipal resources for the sustainable growth of development projects.

Concentrically braced frames (CBFs) have become prevalent as a lateral load resisting system due to their rigidity, low lateral displacement and ease of implementation over the last three decades. These advantages encourage the increasing utilization of this system in the construction industry. Despite the advantages of CBFs, the lack of ductility and buckling of the bracing element before yielding is the main disadvantage this lateral system. In the last three decades, studies have become focused on the ductility and energy dissipation of the CBFs that were modified in terms of using dampers and fuse segments. The current study aims to presents an innovative Composite Buckling Restrained Fuse (CBRF) to be used as a bracing segment. CBRF with relatively small dimensions is an improvement on Reduced Length Buckling Restrained Brace (RL-BRBs) as a hysteretic damper with different performance in tension and compression. Extra tensile elements in a novel configuration were used to compensate for the limitation of tensile strength that exists in bracing elements containing ordinary fuse segments. Here, some key design parameters of CBRF such as length and cross-sectional area of the core are discussed theoretically. Two specimens were designed and tested under cyclic loads. Moreover, the hysteretic response of the specimens was evaluated to calculate their strength adjustment parameters. The results indicate that the proposed CBRF has a ductile behavior with an average strain of 5% and high energy absorption capacity along with sufficient tensile strength.

Recently, base isolation techniques are applied as a resisting system to protect the structures from seismic and dynamic loadings. Due to their importance, in this paper, an optimum arrangement of lead rubber bearing (LRB) and friction pendulum system (FPS) is investigated in irregular buildings and its performance is compared with a regular case. For this purpose, 3 types of irregularities have been adopted. Accordingly, 3, 7 and 10 story buildings have been performed and 12 possible combination have been applied for the isolators in each model. Afterwards, the numerical models have been analyzed using nonlinear time-history analysis and direct integration method and applying 7 earthquake records along the longitudinal and transverse directions of the building. The obtained results of the numerical study show that the application of FPS and LRB isolators in outer and inner columns respectively, led to a better performance compared to the other arrangements by reduction of the inter-story drifts as well as base shear and enhancement of the energy dissipation which is due to the characteristics of FPS isolators in balancing the applied forces with the building’s mass and prevention of torsion occurrence in irregular structures. Unlike the irregular buildings, application of FPS and LRB isolators in inner and outer columns, result in a better performance by reducing the story drifts in regular structures.

Economic tools are definitely an effective way to encourage or enforce contractors to enforce environmentally-friendly practices. Previous studies on this subject mainly focus on the management of waste of construction and demolish (C & D) from the static point of view, which does not take into account the nature of its dynamic by taking all necessary activities in the waste chain. Therefore, the purpose of this paper is to explain the dynamics and relationships between the components of C&D waste management and to analyze the costs and benefits and cost of transportation and fuel consumption using the system dynamics approach. The findings show that the implementation of C&D waste management has many benefits, but the higher cost of landfill at authorized sites will result in more net profits, which will be accompanied by disadvantages such as environmental damage. In addition, the public is suffering from landfill in unauthorized locations and imposing environmental costs due to illegal evacuation. Simulation results also show that increased landfill in unauthorized locations increases fuel and energy consumption and therefore increases fuel consumption costs. This study by investigating and evaluating the researches and measures taken on the waste and waste spillway aims to clarify the use of a systematic approach using the dynamics of systems in a direction in which it is possible to use contract cost-benefit analysis to encourage contractors to disposal of Construction waste in a way that is conducive to the development of the building industry and the preservation of the environment and the resulting savings.

Between various sectors of civil engineering, concrete is one of the most widely used materials in the building industry. The use of pozzolanic materials is one of the solutions for high strength concrete production. High-strength concretes have high compressive strength, high adhesion, very low w/c ratio and permeability and therefore high durability. In this study, zeolite and nanosilica were used as natural and synthetic pozzolans. At first, concrete samples with 20 mixing designs (included water, cement, fine and coarse aggregates, zeolite, nanosilica and super-plasticizer) were designed to achieve the optimal design, and then tests of compressive strength and permeability of high-strength concrete were carried out. In the final step, the values of the mixing plan with the compressive strength results are used as inputs of the neural network. Then, the proposed relationship is optimized using the optimization algorithm from an economic perspective (optimal component value). The addition of zeolite and nanosilica to concrete not only increases resistance, but also decreases the permeability of samples, especially in the long term respect to pilot samples. According to the optimization results, it is observed that cement and nanosilica content has been reduced due to the high cost of production, but increased on zeolite values.

In this paper, a modal pushover method is introduced for the assessment of the asymmetric-plan buildings in which, a load pattern is derived based on the story shears and story torque of building due to the simultaneous excitation in x and y directions. The proposed method is a single-run procedure and its significant advantage is its capability in consideration of the structural yielding in one direction on the total responses of the structure due to the simultaneous excitation in two orthogonal directions. In this method, in order to consider the instantaneous changes during the pushover analysis, two capacity curves of the structure are established based on the adaptive capacity spectrum method and the target displacement corresponding to each capacity curve is determined. Then, the structural responses at two pushover steps corresponding to the obtained target displacements are obtained. Eventually, the total responses of the structure are computed by combining the responses corresponding to the x and y directions. In order to evaluate the proposed method, this method has been applied to an irregular 20-story building subjected to the seven pairs of ground motion records and the obtained results are compared with the responses of nonlinear dynamic analysis as the exact responses. The results show the high accuracy of the proposed method in estimating the inter-story drifts of the studied building.

Housing is one of the major needs. The use of new and new technologies to increase the speed of construction, improve quality, increase earthquake resistance, increase the useful life of buildings is more than ever before. In this paper, four building methods Including LSF, LCF, 3D-PANEL and PRCS, 12 criteria for timely delivery of credit, ease of implementation, need for expert workforce, availability of consumable materials, control and supervision in the process of implementation, useful life, cost, quality Maintenance, energy saving, reducing dead load, increasing floors, compliance with regulations that, from the point of view of contractors, employers, And project consultants. These criteria have been selected using the Delphi method from among the selected criteria, and the fuzzy and gray vikor method has been used to rank building methods, to collect information from seven companies The contractor, two consulting companies and a number of professors have been used to obtain information. Regarding the ranking differences of the methods of construction in both fuzzy and gray vikor methods, for the final ranking of the ranking method, which includes the mean rating method, the Breda method and the Copland method, was used. For the results obtained The best way to build PRCS is through the LSF and 3D-PANEL methods, and finally the ICF method.