نشریه مهندسی سازه و ساخت
سال پنجم شماره 3 (پیاپی 19، پاییز 1397)

One of the most important steps in designing seismic rehabilitation programs for urban areas in metropolises is determining the region’s risk level. There is no doubt of cast that the implementation of a seamless seismic rehabilitation program can secure urban areas against seismic damages. However, these plans face some difficulties in most cases. For instance, their execution costs are very high, or, they are really time-consuming in some cases. It is obvious that a coherent rehabilitation strategy will be effective if it can distinguish executive priorities by identifying areas with high level of risk, and focusing primarily on improving the general condition of these areas. In this paper, the seismic vulnerability of the 7th region of Tehran is studied. For this purpose, the main parameters that affect the vulnerability of the region are identified first. Then, considering the uncertainties in these parameters, their impact on the vulnerability of the region is determined. ArcGIS software is used not only to model the impact of these parameters, but also for data training. The results of this study show the vulnerability level of different parts of Tehran's 7th region. In fact, this study provides a comprehensive and meaningful overview of the current status of the studied region, which can helps the engineers to design suitable seismic rehabilitation programs. The obtained results are presented as a map which reveals the vulnerability level of the region. Based on such a map, neighborhoods or areas with high seismic hazard are identified. Considering these classification, the seismic rehabilitation techniques can be offered purposefully.

Extensive use of new project delivery systems and engineering important role followed by contractual types developments inside or outside of country increased the importance of providing identical internal and international contracts. These contracts prepared a standard framework for project risk and responsibilities allocation for both consultants and clients. This research aims to study general condition of Iran and FIDIC consultant's agreement to determine challenging clauses and conflict orientation in these contracts.
Accordingly, after reviewing Iran and FIDIC client/ consultant agreements, comparison between contractual clauses has been carried on and important clauses with indemnity provision has been separated; which based on, claim source breakdown structure (CSBS) produced. Compensate receiver and indemnity type for those clauses has been set according to Iran and FIDIC consultant's general condition; followed by comparing between two contract clauses and analytical analysis. Consequently, a complete list of important clauses with indemnity provision related to consultants and clients determined and classified in terms of cost, time, scope and contractual claim's reasons. The results show higher contractual risks and most claims ensue of cost's conflicts for consultants in internal contracts. Recommended suggestion for Iran and FIDIC client/ consultant agreement are provided based on this study results and expert's ideas

Performance-Based Design Methods idea is based on decreasing the structural damages in earthquake, according to client requirements, it seems be an economical design method. There are two different Performance based design approaches, the former is direct approach and the latter is indirect approach. In direct approach the level of performance is assumed at the beginning of design procedure and design has been performed to achieve the assumed performance. Direct displacement-based design method (DDBD) is known as direct approach. In DDBD procedure performance of the structure is predefined by assuming the total structural drift against specified earthquake level. In DDBD method, structural base shear is calculated according to occurrence of mechanism in earthquake. Therefore DDBD seems to be more realistic in comparison to force based design (FBD) because of considering the structural nonlinearities directly in calculations. In this paper, the principles of DDBD are explained, then concrete special moment frames of 4, 8, 12, 16 stories were designed by both of DDBD and FBD methods. It is concluded that columns dimensions and reinforcement in DDBD will be obtained equal or greater than FBD. In addition, longitudinal reinforcements at the middle span of beams in the frames of DDBD are more than the two ends which are the possible locations of plastic hinges. Frames evaluation by push-over analysis shows that DDBD frames responses are more compatible with plastic mechanism which is supposed in design procedure. Also it is concluded that the maximum drift of DDBD frames before collapse are usually greater than FBD ones and in DDBD frames plastic hinge formation in upper stories is more than FBD frames.

The use of different methods of prestressing systems is very common in gravity frames at the present time. This technology can also be used in lateral load resisting frames. In addition to ordinary moment frames, this technology can be used in intermediate and special moment resisting frames. The use of post-tensioned prestressed slabs as primary members of the seismic load resisting load path in special moment resisting frames is not permitted based on available codes. The use of prestressed beams in special moment resisting frames includes some limitations. In this study, after the design of special prestressed moment frames with prestressed beams and slabs using conventional methods, considering special seismic design criteria, nonlinear pushover static analysis has been carried out in order to investigate performance levels and vulnerability of this type of frames. After performing nonlinear static analysis, target displacement of desired frames has been calculated and the plastic hinges formation sequence and related acceptance criteria for these hinges is investigated. Also, in order to study the effect of prestressing on seismic behavior of special prestressed moment resisting frames, response modification factor and related seismic parameters of this type of frames are obtained. Finally, all the above steps are repeated for the corresponding reinforced concrete special moment resisting frames, and the results were compared with prestressed frames. The obtained results show that in addition to applying restrictions on the use of prestressed beams in special moment resisting frames, target building performance levels and structural performance levels are acceptable, compared to reinforced concrete frames. Higher ductility factor and response modification factor has been achieved for prestressed frames compared to reinforced concrete frames and the base shear at yield strength for this type of frames are considerably lower than the similar value for reinforced concrete frames.

Liquid storage tanks are important industrial structures that must continue their performance under severe earthquakes. The induced damages caused in the past earthquakes shows their poorly behavior of these structures. One of the most effective methods to retrofit and reduce the induced forces is to use base isolation. Friction Pendulum System called FPS has better performance compared to other base isolation systems, due to its period does not depend on the weight of the structures above it.
The aim of this paper is to investigate the effect of FPS under three different hazard level earthquakes (SLE, DBE and MCE). It is also, the impact effect due to contacting the slider with the side restrainers is investigated. For the required analysis, two different liquid storage tanks are considered and their responses are compared in Fixed, Isolated without considering impact and isolated with considering impact conditions. The obtained results show, increasing the hazard level of ground motions leads to decreasing the performance of FPS. It is also observed, compared to SLE and DBE earthquake ground motions the MCE has the maximum probability of impact. The results also show that, the impulsive mass displacement, overturning moment and base shear increases when the impact occurs, while the impact has no special effect on convective displacement

Extending service life and preventing demolition of existing structures are the primary goals of structural strengthening and rehabilitation. Fiber-reinforced polymer (FRP) composites have been the most common type of composite in the realm of structural strengthening applications. In recent years, as a new type of composite, epoxy is replaced by an inorganic matrix, named fiber reinforced cementitious mortar (FRCM), and have attracted a great deal of interest among researchers. Focusing of these kind of novel composites, this paper tries to find a connection between FRCM composites behaviour, as their maximum fiber strain, in flexural and direct shear tests. To achieve this goal, a cross section analysis of previous research works on strengthened RC beams with one layer of composites was conducted and the maximum strain of the fibers was obtained. Calculated fiber strains in flexural strengthening specimens compared with corresponding measured maximum fiber strains in direct shear test specimens. Comparison of results show that the average of maximum fiber strain obtained from flexural specimens is in good agreement with corresponding one measured in direct shear test specimens. Consequently, maximum fiber strains could be designated as the lost link between flexural and direct shear tests as two separated part of a chain

The available analytical and finite element methods set the values of elastic modulus of nanocomposites more than the values obtained from the test. In this thesis, a new linear and continuous analysis method is used to determine the best and most similar value of elastic modulus for polymer nanocomposites to laboratory value is provided. For this purpose, the governing elasticity equations in polar coordinates have been solved for nanocomposite representative volume element (RVE) with shear-lag model by assuming perfect bond condition between CNT and matrix. Then, using the finite element modeling with Ansys software, elastic modulus of connectivity states of almost complete and half break between the two phases are calculated and finally the proposed new model that is modeling with spring in the states of almost complete connectivity and half break between the two phases are provided and elastic modulus is calculated. In this method, shear stress is also offering a new relationship between CNT and matrix areas that have been. To ensure the validity of the results of presented model to determine the elastic modulus, the obtained results are compared with laboratory method results of other researchers that in all cases the proposed elastic modulus is much closer to laboratory sample and finite element models and good agreement

In the seismically active countries such as Iran, there are many structures that have been designed and constructed in recent years that do not conform to the terms and provisions of the design codes. On 26 December 2003 at 1:57 GMT, the historical city of Bam, located in the south-eastern region of Kerman province in Iran, was shaken by a relatively strong and destructive earthquake. This earthquake clearly demonstrated that combination of relatively rigid load-bearing external brick walls and flexible internal steel columns, existing similarly in most other regions of the country, is quite hazardous. Also the use of steel beams and columns in buildings without observing proper seismic provisions showed no improvement over non-engineering designed buildings. In this research, two steel frame buildings which had been damaged in the bam earthquake were studied. The first building has bracing system in both directions and in the second building the bracing system only exist in one direction fallowed by infilled panel with saddlebag type connection(semi-rigid Khorjini connection) in opposite direction. In both buildings all the standard of criteria 2800 and Seismic provisions are considered. Nonlinear static analysis (Pushovers) and nonlinear time-history analysis are implemented on both structures. After determining the vulnerability of structures, using steel plates and viscous damper, the results show that retrofitted buildings with fluid viscous damper dissipate higher energy in comparison with the buildings retrofitted by the steel plate. Strengthening the existing buildings were investigated and compared with each others through three different 1. replacing relatively strong bracing system with the relatively weaker bracing 2. Strengthening the columns by adding cover steel plates to the columns of building and 3. Global Strengthening bracing and columns system of buildings.

Low levels of efficiency, low profit margins and problem in quality make construction companies discover methods to improve their information, interaction and communication management. Information and Communication Technology (ICT) provides these tools to improve project processes. Virtual design and construction (VDC) is a modern method introduced as a potential tool to overcome problems arises in the construction industry. VDC aims to provide effective solutions for integrating multidisciplinary data required for all phases of the project life cycle, including design, planning and construction. The researchers believe that investment should increase productivity, enhance the quality of products and services, reduce operating costs and increase profits, otherwise does not comply with the definition of technological progress and should not be expanded. In this regard, it is necessary that the benefits and challenges of the adoption and implementation of such an approach in a project, be investigated. In this study, through a literature review, the benefits and challenges of applying VDC in projects are identified and classified based on Project Management Knowledge Areas. Then through quantitative research methods, benefits and challenges identified, are evaluated and prioritized and the most significant positive and negative effects of the application of virtual design and construction in projects are detected with respect to project management knowledge areas. The results of this study illustrate that the most important benefits and challenges of using the VDC method are related to the field of integration and implementation of VDC pose the greatest impact on this area of project management knowledge. Thus, the aforementioned area, integration, should be considered as a top priority.

This paper presents the test results of an experimental study that investigates the behavior of RC deep beams strengthened in shear with externally bonded (EB) and near surface mounted (NSM) techniques using CFRP strip. A total of 6 RC deep beams were constructed and tested under four-point bending. Test specimen had a cross section of 150 × 500 mm and a total length of 1450 mm. This study included two parameters; techniques (NSM and EB) used for strengthening and amount of shear steel reinforcement ratio. All of the strengthened beams have the same CFRP configurations; and CFRP strips were bonded perpendicular to the diagonal connecting the loading and the support points. The specimens were divided into two groups based on the shear steel reinforcement ratio. There were three beams in each group. One of them was a control beam, the rest of the beams in each group were strengthened by EB or NSM techniques. The amount of CFRP strip in EB and NSM techniques is equal. All of the beams were loaded until failure and during the experiment, deflection and compressive strains of concrete, tensile strain of longitudinal steel bar at mid span and crack width of flexural and shear, were measured. The test results showed that shear strengthening of the deep RC beams with NSM technique causes to increase in ultimate load capacity and ultimate deflection capacity by 18% and 16% respectively, compared with the control beam. Also, the ultimate load capacity and ultimate deflection capacity of deep RC beams strengthened with NSM technique are 6% and 15% more than beams strengthened with NSM technique respectively. The concrete compressive strain at ultimate load of deep RC beams strengthened with NSM technique is 50% more than beams strengthened with NSM technique.

The Iranian seismic code (standard NO.2800) provide minimum provisions and regulations for the design and construction of buildings to resist the earthquake effects that by these provisions, it is expected the purpose of this code satisfying. Since the terms and provisions provided in the standard 2800, is based on resistance design, so consider this standard to meet performance targets, quantify performance levels and damage to buildings during earthquakes there may be confusion exhibit that the uncertainty principle would be more serious in buildings with higher importance. The seismic behaviour of very high importance buildings according to Iranian Standard NO.2800 (IS2800) is that; these building not affected the strength and stiffness of structural and non-structural components in design level earthquake, so that serviceability is possible. Therefore, in this research 3, 6 and 10 storey reinforced concrete buildings with very high importance (hospital use) that according to the provisions and regulations of IS2800 (4th Edition) and ACI code are analysis and designed in SAP2000 software, to be studied. In this paper by using nonlinear static and time history dynamic analysis of the building models under far and near fault records, the performance level of buildings is determined and then about to meet the purpose of Iranian Standard NO.2800 for the very high importance buildings is concluded. The obtained results show that in the nonlinear static analysis method for the 10 story building and in the nonlinear dynamic time-history analysis method for all buildings, the expected performance level of IS2800 (immediate occupancy) is not satisfy

Today one of the most common systems for resisting lateral forces (wind and earthquake) is special concentrically braced frames (SCBF). Out of plane buckling in compression causes large inelastic flexural deformations in gusset plate. In order to supply the capacity of inelastic deformations in gusset plate, current design practice recommends a “2t” linear geometric offset to be used. Recent research has been done to improve the seismic behavior of connections for braced frames shown that the use of a clearance by elliptical pattern has better results than linear pattern clearance.
In this paper using the finite element method, a one-story frame under cyclic loads and considering the nonlinear effects of material and geometric has been modeled and verified. The parameters that considered are effect of clearance (linear, elliptical and lack of clearance) at different angles and clearance in an elliptical pattern. The results of the samples, hysteresis curve, compressive and tensile resistance, as well as stress and strain showed that the clearance effect on tensile strength and compressive is between 2.86 to 13.5 percent for different angles of connected braces. Ductility in the case of lack of clearance between angles of 30 to 60 degrees reduced 30 to 60 percent relative to the elliptical clearance

In this study، a new roofing system made of precast composite sandwich panels is introduced. This sandwich panels floor system consists of three kinds of precast concrete sandwich panels including capital panels، beam or between columns panels، and slab or middle panels. This panels are built of three layers; A high strength reinforced concrete as top layer، a thick layer of light-weight concrete as a middle layer or core and the third layer or lowest layer is an ordinary reinforced concrete. These panels are connected together with special connectors at their edges. In this study، ABAQUS software has been used for modeling and analyzing the sandwich panels floor system. Moreover، to optimize the design of the sandwich floor panels with different spans، a MATLAB code has been was developed; By entering the properties of steel sections and mechanical properties of concrete used in construction of the sandwich panel in this program the optimum design variables for panels of different، spans، loading and boundary conditions and design constraints was determined which are shown by means of curves and tables; The objective of this optimization was to obtain the lightest and most economical options. Due to possibility of industrial production of precast panels under standard conditions and simplicity of construction, the introduced novel floor system can be a viable alternative for common floor systems. Besides ،the novel system can save amount of material، labor، time، and cost in building construction