Journal of Civil Engineering and Materials Application
Volume:3 Issue: 3, Summer 2019

After liquefaction occurrence, summits on the surface of the earth and inside the soil layers that damage the structures based on them or buried structures and vital arteries. In the last two decades, various quasi-experimental methods have been presented to determine the amount of strain (siting) and shear strain maximum based on field data and laboratory data. The main purpose of this study was to compare the results of evaluation of the potential of liquefaction occurrence from the viewpoint of the risk of occurrence and the amount of settling after the occurrence of liquefaction on in the soil layers based on the use of the results of the standard penetration resistance (SPT) and shear wave velocity (Vs) along the path 2nd line of Tabriz metro. In this study, 54 borehole loops were first collected along the line 2 of the metro mentioned. Then, the liquefaction potential in the studied area is based on the proposed methods and the liquefaction risk index (LPI) is estimated. Then, the amount of probable sum of the soil layers due to liquefaction occurred based on the results of the two proposed methods. The results of the research show that the two methods are not suitable for matching and the risk of liquefaction arising from the SPT method is less than the Vs method. Also, the prediction of the amount of settling after the occurrence of liquefaction in the soil layers has more amount based on the shear wave velocity method in comparison with the standard penetration resistance test method.

Concrete-filled steel tubular columns have been extensively used in structures, owing to that they utilize the most favorable properties of both constituent materials, ductility, large energy-absorption capacity, and good structural fire behavior. Concrete inside the steel tube enhances the stability of the steel tube, and the steel tube, in turn, provides effective lateral confinement to the concrete. Furthermore, the fire resistance of (CFT) columns is higher than that of hollow steel tubular columns, external protection being not needed in most cases. During a fire, the steel tube acts as a radiation shield to the concrete core and a steam layer in the steel- concrete boundary appears. This paper presents to investigate the effect of the parameters compressive on behavior of concrete-filled tubular (CFT) columns under fire by numerical simulations using ABAQUS software. Three different diameters to thickness ration of 54, 32 and 20 are considered in this study with two concrete's compressive strengths of 44 and 60 MPa. The measured compressive axial capacity is compared to their corresponding theoretical values predicted by four different international codes and standards. The results indicate that the effect of diameter to thickness ratio on the compressive behavior of the sections is greater than the effect of the other factors. Also, the axial capacity calculated by most of these codes reduces as the diameter to thickness ratio increases as verified by experimental results.

These Bridges are vital part of the transportation network Department of Civil Engineering. Their destruction caused by the occurrence of a strong earthquake can cause irreparable damages to the regional economy. One of the effective factors on seismic response of a bridge is abutment and it's modelling. In most cases, analysis of seismic behavior and modelling of bridges is done using simplifying assumptions. This simplification may cause major changes in prediction of seismic behavior of bridges. Using simplified, roller and full models for abutment is very important in design and evaluation of seismic behavior of bridges. Backfill is a vital factor in modelling abutments. In this study, abutments were analyzed in three scenarios under records related to three stations of Imperial Valley earthquake (1979) and responses compare in two states with and without backfill. The results showed that minimum response (for deck, pier column and abutment) were related to the first modelling scenario (roller abutment) and maximum response were related to the fifth modelling scenario (simplified abutment as suggested by Shamsabadi for cohesive soil). Modelling of backfill was effective on displacement and rotation of pier column and displacement of deck and moment of abutment. For all records of earthquake, wall pier abutment (sixth scenario) was considerably consistent with modelling based on Caltrans guideline for sandy soil (second scenario). In height ranging from 5 to 9 meters, the suggested modelling (wall pier abutment) can be used instead of Caltrans method. In this height range, the results (maximum abutment displacement and abutment pressure) vary from 11to 23%.

The present study mainly aims at the identification and laboratory production of geopolymer concrete with the increased resistance to acid attack. For this purpose, after evaluating the reactivity of the raw materials and their applicability in the production of geopolymer cement among the available aluminosilicate materials, the metakaolin pozzolan was selected as the appropriate raw material. After the selection of the binder and activator of sodium hydroxide, the alkali activation process was performed for the mixtures of raw materials. Then, for the initial estimate of the durability performance of geopolymer cement  in acidic media, the durability of concrete samples was investigated in 1M sulfuric acid for 7, 28 and 90 days. The results showed that the nano-silica and nano-clay are effective in improving the performance of geopolymer concrete, as the addition of 3% nano-silica resulted in the 0.44% increase in the strength of the geopolymer concrete. Also, the addition of 3% nano-clay led to the increase in the strength of geopolymer samples up to 0.54. In addition, the samples are more durable in acidic media, so the weight loss of nano-clay-containing geopolymer samples in 90 days is 1.2 times that of geopolymer concrete samples without this additive.

In cases where the soil underlying the foundation is loose and unable to carry the loads imposed by the structure, improving the soil by an appropriate approach is essential. The application of polymeric materials such as geogrids, in recent decades, has been of interest to engineers and researchers in order to increase the bearing capacity of soil foundations. Geogrid reinforcements allow for achieving an increased bearing capacity or a reduced layer thickness of soil improvements. The most significant factor used in the design of shallow foundations is the bearing capacity of the foundation along with its settlement. In geotechnical investigations, probabilistic analyses could be beneficial in the relevant problems. The Monte Carlo probabilistic simulation method is one of the most commonly used methods in solving geotechnical problems. Therefore, in the current research, a reasonable estimation of the bearing capacity of a strip foundation has been conducted by using a numerical model with the help of the discrete-element software FLAC3D in conjunction with the calculation of the probabilistic bearing capacity via the Monte Carlo simulation method and by considering the uncertainty of the soil internal friction angle and cohesion coefficients.