BULLETIN OF EARTHQUAKE SCIENCE AND ENGINEERING
Year:2018 | Volume:14 | Issue:4|Papers Count:7

In this study, we assessed the performance of a concrete bridge under the dynamic strain of an earthquake in the near and far domain of earth’s faults. With respect to available data and showing the effects of key factors and variables, we have examined the bridge’s performance. The modelling of a double span bridge has been done in CSI Bridge software and has been compared and examined to assess the capability of a bridge under the strain of a close-to-fault-line earthquake and a far-from-fault-line earthquake. Timeline interpretation was done on the resulting models and from 7 records from the past earthquakes and it was observed that the close to fault line earthquakes caused much bigger displacements when compared to far from fault line earthquakes. Bridges which are separated by a quake separator, have an acceptable response to far from fault line earthquakes. This means that by disassembling these bridges, the acceleration rate on the deck, the cut of the base, as well as the relative displacement of the deck relative to the undivided bridge, is reduced. This issue is not reflected in the response of the bridges to faults near earthquakes. By investigating the record of near-earthquakes, it was observed that these earthquakes produced large displacements to earthquakes that are far from faults, which could make the isolation system more critical, so, to avoid this event, it FDGM should be used to reform the response these bridges have to the earthquake.Based on these results, it can be stated that the displacements near the fault and with the effect of progressive movement will be greater than the distances from the fault, so that for the ratio of different distances from the fault, the lower this ratio is, the maximum displacement of the bridge and the maximum cutting force will also be greater.

With the increasing expansion of the technology for the production of high- tech military equipment, the need to build structures with acceptable resistance against explosion in vital centers increasingly felt. These structures as the facilities in times of peace and in times of war and natural disasters are contributing to saving lives. Due to the lack and limitation of experimental data for explosion problems, numerical modeling based on finite element method can help in designing and estimating the loads exerted on structures. In this research, the effects of sacrificial RC slab on the performance of underground arched shape RC structures with practical details under explosion load were studied. Ls-Dyna finite element software was used to solve the problem and optimized concrete arches under different levels of explosives were investigated. Results show that, if a sacrificial RC slab is placed on the crown of the study structure, no damage will occur in structure and structural damages will be concentrated in RC slab. However these damages will be increased with increasing of the explosives. On the other hand, sacrificial slab distributes the blast waves at a higher level of soil which in turn shield the structure against explosion. Consequently, the safety of the structure in terms of performance against blast loading will be increased significantly.

Corrosion of steel in concrete is one of the most important factors in the destruction and destruction of concrete structures around the world. Even in advanced countries, this is a year- long issue that will cost a lot of maintenance and maintenance of concrete structures that are sensitive and insensitive to national and national resources. These damage are more severe in the Gulf countries, and many concrete structures have been corroded and damaged. Studies show that the main corrosion agent of reinforced concrete structures is corrosion of steel joints. Therefore, all corners of buildings and structures in corrosive areas should be adequately protected against corrosion. Separating the rebar from the environment and insulating it in terms of contact with corrosive agents is one of the solutions to prevent corrosion and durability of reinforced concrete. Different methods have been proposed for this purpose. In this study, it has been shown that the use of Galvanized reinforcement prevents the corrosion of reinforced concrete meshes effectively and, as a result, reinforced concrete will have a much higher resistance to corrosive environmental factors, such as chloride and sulfate attack. Also, economically, the results show that the cost of using galvanized rebars in sensitive industrial structures, such as oil tanks, is about 6 percent of the total cost, and in conventional buildings, between 1 and 2 percent of the total cost, which is also cost-effective in this regard. Therefore, the use of galvanized bars as a main and effective tool for protecting steel corrosion can be considered by the construction industry.

Fiber reinforced concrete (FRC) has been used widely due to its advantages over plain concrete such as high energy absorption, post cracking behavior, flexural and impact strengths, arresting shrinkage crack. Toughness is the amount of energy that a concrete can withstand by impact forces before rupturing. Toughness is obtained from the area under the force- deflection curve in flexural and compressive test and is characterized by a coefficient called the toughness ratio. In this study, the effect of 3 percentage of glass fiber (1, 2 and 3%) with two different size of 3 and 6 millimeter on flexural and compressive toughness of FRC were investigated. The flexural and compressive toughness were carried out in accordance with the JSCE-SF4. The results indicate that by increasing the length of glass fiber, there is no significant change in the amount of flexural toughness. Mixtures with 3% glass fibers has the highest flexural toughness and mixtures with 2% glass fibers has the lowest flexural toughness. Among mixtures with the same length, the mixture with the higher percentage of glass fiber had the highest compressive toughness.

The spread of an initial local failure from element to element, eventually resulting in the collapse of an entire structure or a disproportionately large part of it is defined as progressive collapse. Occurrence of events such as blast, firing, vehicle collision and error in design calculations or construction could cause local damages to structures. Although prospect of progressive collapse is not considered in ordinary buildings, such incident could result in significant human casualties, economic losses, and security threats in buildings which fall into very high importance categories. In this paper progressive collapse analysis is briefly presented and then nonlinear behavior of a seven-story reinforced concrete building with special resisting moment frame designed against seismic loads is evaluated under progressive collapse in accordance with Unified Facilities Criteria, UFC4-023-03 code, based on alternate path method using SAP software. It is observed that the structure is unable to meet the requirements presented in the UFC. Thus, weak beams were strengthened in flexure by carbon reinforced polymer (CFRP) fabrics. Results of the analysis indicate that the adopted method greatly enhances continuity and strength in beams adjacent to the lost column and hence in plastic hinge development, remaining the damage to be local.

One of the most important issues in the management of railways maintenance is the stabilization of the bed and railroad tracks under the influence of environmental loads. This issue is of particular importance, especially in tall embankments, based on loose platforms with little or no bearing capacity. Among the existing methods to improve the embankment and the bedding in the railway lines, installation of micro piles for fixing the embankment and the bed, which does not block the line and stop the traffic, is preferable. In the present paper, a parametric study was carried out; using ABAQUS, for high rise embankment improved by micro piles with different patterns, operational loads, railroad traffic and severe earthquakes, using the LM71 loading standard. The results indicate that the factors affecting the pattern of the micro plots generally include the distribution of loads, shear parameters and bearing capacity, depth of the micro piles and geometric characteristics of the embankment. It should be noted that the optimum arrangement of micro piles for improvement, is the length between the toe and 0.25 to 0.5 percent of the slope length, which reduces the maintenance and handling cost.

One of the common problems in the implementation of concrete structures is seam or cold joint. The discontinuity in concrete body can cause structural weakness, increased permeability, reduced durability, corrosion of the rebar, and bad appearance of concrete. In this study, in order to evaluate the effect of cold joint on compressive strength of concrete, 192 cubic samples by national method of mix design in 4 modes, in which48 samples without cold joint, 48 samples with horizontal cold joint, 48 samples with vertical cold joint, and 48 samples with diagonal cold joints were concreted in a 24-hour time interval. After 28 days of treatment with standard conditions by pressure cylinder device, the compressive strength of the samples was evaluated. After evaluating the results of the experiments, the values of the effect of cold joint on the compressive strength of the samples, the uncertainty and the probability of failure of the samples have been investigated. The results of analyzes indicate that, generally, the creation of a cold joint in concrete reduces the compressive strength of concrete. However, the reduction in compressive strength depends on the degree of cold joint to its angle. Also, the size of surface angle of the cold joint is also affected by the probability of failure.