Sharif Digital Repository

Today, in our beloved country of Iran and other parts of the world, reinforced concrete structures are used in large industrial projects, in some cases we see their very early failure even before the time of operation. This issue in the southern coasts of the country due to special weather conditions (humidity and high temperature) and the existence of the offensive ions such as chlorine and sulfate in seawater are more important and we always face with severe corrosion of reinforcement and reduced service life of concrete structures in these areas. Despite this, little research has been done on the reliability of concrete facilities in the vicinity of the Caspian Sea in the north of the... 

There are many parameters which are utilized to obtain a more reasonable performance for structures under earthquake excitations in seismic provisions. It is well recognized that the main character to design of structures under seismic excitation is probabilistic rather than deterministic; therefore, it should be determined if the probability of structural damages is decreased when such parameters change in design of structures. In this thesis, fragility curves are developed in order to evaluate these parameters. Fragility curves are employed for various probability parameters. These diagrams are utilized to demonstrate when a coefficient or a number of parameters are used to improve... 

The continual deterioration and insufficient strength of reinforced concrete (RC) structures has been a vital problem in the field of civil engineering such an extent that traditional methods of strengthening found to be inconvenient. Nowadays by increasing demands for retrofitting of structures, it necessitates the application of efficient, inexpensive and unobtrusive methods of strengthening. Common way on retrofitting was to use of steel plates externally bonded to RC members. Although this technique has proven to be reasonably effective, it has several distinct disadvantages such as susceptibility of the steel plates to corrode and the excessive weight of steel plates when used in... 

A total of twenty-four reinforced concrete arches with dimensions of 110 × 30 × 10 cm were casted, fabricated and tested. There are three variables, including: height to span ratio, longitudinal reinforcement ratio and arrangement and number of FRP layers.Based on results, with increasing height to span ratio, the efficiency of FRP strengthening method decreases. It is due to the fact that FRP materials inherently behave better in tension. From another point of view, in lower arches (L group) extrados bonding technic has better effect on increasing peak load of the arches, while in higher ones (H group) intrados bonding is discerned as the best method of strengthening. This paradoxical... 

In developing countries, one of the structural systems used for many buildings is the masonry system, and there are also many existing buildings worldwide with different uses constructed with this system, some of these buildings may have a major historical value and because of that, study of behavior of these buildings to find effective ways to improve their behavior is very important. In this study, the use of Textile Reinforced Concrete (TRC) for retrofit masonry walls is examined. For this purpose, seven scaled brick walls is used, including a test model, a model coated with plane concrete on one side of the wall, a model coated with plane concrete on both sides of the wall, a model... 

A simply supported reinforced concrete beam has been built at the concrete laboratory of Sharif University of Technology. The cross section of the beam has been rectangular and all the reinforcing steel bars have been placed at the bottom of the beam. A progressive damage has been applied to the beam first by cutting the concrete cover and then by cutting the reinforcing bars one at a time. The beam has been tested using forced vibration test where an impact hammer has been used to apply the external load. The acceleration of the beam has been recorded based on which the FRFs and then the corresponding modal parameters have been determined. Finally natural frequencies, MAC, COMAC and mode... 

The actual value of structures should not be evaluated only based on initial cost, because failure cost and economical losses due to corrosion and natural hazards can be catastrophic. When a long life Performance of a structure is expected, life cycle cost analysis is the best way to assess and compare economic value of different design choices. The main purpose of this work is investigating the effect of shear walls in limit state cost and total cost . Results demonstrate that shear walls can reduce limit state cost up to 70 percent . Furthermore the influence of increasing thickness of shear walls and effect of reducing dead loads in total life cycle cost is discussed. It is shown that... 

In concrete which is a quasi-brittle material failure initially occurs between aggregate and mortars. Fibers of all orientations, randomly embedded in FRC, serve to restrict and delay the coalescence of micro-cracks, micro-voids and micro-slips into wide continuous cracks. While the fibers increase the uniaxial tensile and compressive strength only moderately, they are very effective for enhancing the ductility and energy absorption capability. This elevates structure resistance to impact, ground-shock and blast. One of the most successful efforts toward reaching a macroscopic model which can take micromechanical properties into account is the Microplane model. In this microscopic... 

Performance based design was first introduced in order to evaluate seismic vulnerability of structures in retrofitting topic and was rapidly implemented in new design codes. The main cause conducting widely developing of performance based design methods, has been accurate estimation of seismic demand parameters. Since seismic structural members displacement during earthquake has a direct effect on the amount of sustained damages, displacement index has always been a key concept in performance based design. The main goal followed by this research is comparing the results obtained from the standard pushover method (with two theorems of distributed plasticity and plastic hinges) and the... 

Explosion as a physical phenomenon have various effects on the environment, including living organisms, surrounding buildings, equipment and infrastructure there. Due to such extreme loading conditions, efforts have been made during the past three decades to develop methods of structural analysis and design to resist blast loads. The analysis and design of structures subjected to blast loads require a detailed understanding of blast phenomena and the dynamic response of various structural elements. The most appropriate method for evaluating the behavior of structures under blast loading is performance approach which specifies the response of structures against explosion. It seems that... 

Global collapse in earthquake engineering refers to the inability of a structural system to sustain gravity loads when subjected to seismic excitation. Dynamic instability phenomena in exist buildings have a key position and for this reason strict criteria in structural seismic assessing codes presented for avoiding this phenomena. At this study, dynamic instability of five designed concrete buildings with moment frame system, mixed up 3, 6, 9, 12 and 15 story building, are investigated. P-delta effects, deterioration in strength and stiffness and cyclic deterioration in structural components considered in this investigation. For modeling nonlinear behavior of elements, experimental results... 

According to key importance of bridges in transportation system vital routes, a need to study and survey of bridges against destructive factors exist. Among these, bridges with concrete deck are widely used. One of the most important factors in destruction of these bridges is steel reinforcements corrosion and destruction of bridge deck. So in order to reduce the aggregation of reinforcements in critical sections and performance improvement of deck beams, a reinforcing substance which is not only resistant against corrosion but benefits from high resistance and stiffness is implemented.In this research the case studied bridge is simulated by finite elements software in two cases; reinforced... 

With occurring severe earthquakes, damages of columns in RC buildings can lead to overall failure and collapse. So retrofitting of such columns that do not comply with the design requirements is necessary to prevent such phenomena. A variety of methods has been introduced so far for retrofitting. The key factors in determining the retrofitting methods are being economic and easily implemented in the design. Confining concrete columns with pre-stressed steel strips is a new technique that is simple and economic. Previous experimental experiments have shown that this method can enhance ductility and overall seismic behavior of such columns.
In the present study three and six story frames... 

In the last decades, noticeable experimental and analytical investigations have been carried out on cast-in-place Reinforced Concrete column to Steel beam (RCS) connections, however rarely have been conducted on the precast RCS. In this reaserch, test results of five half-scale interior precast RCS connections with variable joint configurations are presented. The steel beams were connected to the precast column, using face bearing plates, embedded in the connection zone. The flanges of beams were strengthened with respect to scaled section, in order to increase the load transfer to the joint. All samples were loaded under reversed displacement controlled condition. The failure mode, joint... 

This research proposes a damage assessment framework based on the visual features of a damaged reinforced concrete shear wall, such as crack pattern distribution, crushing areal density, aspect ratio, and the presence of the boundary condition. The study contains two parts: identifying the performance level of the damaged walls (i.e., Immediate Occupancy, Life Safety, and Collapse Prevention) and estimating the residual strength and drift ratio of the walls. The research database contains 236 images of 72 reinforced concrete shear walls tested in the laboratory under the quasi-static cyclic loadings at various drift ratios between 0.0 to 4.0. To identify the performance level of a damaged... 

The purpose of this paper is to quantify the extent of damage of rectangular reinforced concrete shear walls after an earthquake using surface crack patterns. One of the most important tasks after an earthquake is to assess the safety and classify the performance level of buildings. This assessment is usually performed by visual inspection that is prone to significant errors. In this research, an extensive database on the images of damaged rectangular reinforced concrete shear walls is collected from the literature. This database includes more than 200 images from experimental quasi-static cyclic tests. Using the concept of Fractal geometry, several probabilistic models are developed by... 

Nowadays one of the important issues in earthquake engineering is seismic vulnerability assessment of structures and selecting the best retrofit method for them. On the other hand due to probabilistic nature of earthquake occurrence and uncertainties exist in determination of structure capacity, probabilistic approaches in seismic assessment and retrofit of structure, are highly interested by many researchers. Therefore in this research four probabilistic based methods in seismic retrofit and assessment of structures are proposed and to illustrate the application of these methods, which are summarized below, some RC frames are investigated:
1- Seismic assessment of structures using new... 

In this thesis, experimental and numerical investigations are performed on dynamic behavior of fiber reinforced concrete (FRC) by split Hopkinson pressure bar (SHPB) and penetration tests. In the experimental part, effects of parameters such as quasi-static compressive strength of matrix (36 and 48 MPa), strain rate (3*10-5 up to 100 s-1), type of fibers (crimped steel, hooked-end steel, micro polypropylene and micro polypropylene) and volume fraction of the fibers (0%, 1% and 2%) are studied by employing SHPB apparatus on testing more than 150 specimens. Also, different types of FRC panels with 5 cm thickness were casted to perform 20 penetration tests with compressed gas gun apparatus. The... 

Vertical addition of existing buildings provides more living space without the need for more land use. Also adding a story on an existing building is one of the common needs in metropolitans. However, the structure may bear high risk due to vertical addition. This study aims to model conventional concrete structures built in Tehran and then assess and compare the seismic performance of base structure and extended structure. Seismic performance of a system is defined as their efficiency in providing enough safety and reducing the Life-Cycle Cost. For this purpose, seven archetypes as base structures and eight extended structures corresponding to base structures, that had residential... 

Concentric steel braces and brace-type dampers are often applied to the upgrading of reinforced concrete frames subjected to lateral loads. These braces may develop High axial tension forces, and transferring them appropriately to the existing beam– Column joints is a key challenge. This paper investigates a solution for connecting the end-plate of the steel brace with the frame, using shear-key plates fixed to the concrete with anchor bolts, and a low friction material inserted between the end-plates and the shear-key plates. The presence of the low friction material impedes the development of tension forces in the anchor bolts and ensures that they are basically subjected to shear forces....