ABSTRACTSeismic base isolators and dampers are commonly used as control tools in building frames to mitigate earthquake damage. This study proposes and investigates a structural system consisting of a central fixed core and an isolated section, the two parts of which are connected to each other by a damper. In new structures, called partially isolated (PI) structures, the interaction between conventional frames with fixed bases and frames equipped with control tools including isolators and dampers is measured using a three-mass model by three simplified differential equations of motion. Validating the proposed model provided good results. The model with various modes of partial isolation and certain mass ratios was subjected to seven near-fault and seven far-fault earthquakes to be evaluated. The mean displacement, acceleration, and shear responses of the structural-isolating-damping model were compared with those of fully isolated (FI) and fully fixed (FF) structures. The results showed that by connecting the two parts, responses of the fixed part to FF structure and those of the isolated part to FI structure significantly improved. Under near-fault earthquakes, the displacement response reduction of the fixed part to FF model was estimated to be about 20% and the response of the isolated part to FI model was about 50%. Due to the functional weaknesses observed in FI structures including large displacement of the structure base, poor performance of the isolator in near-fault earthquakes, and high costs of preparing and installing the isolation system, these points were significantly resolved in PI structures.

In structural analysis and design, there are always uncertainties in determining loads and capacities. Structural reliability quantitatively considered uncertainties in analysis and design procedure. One of the well-known criteria to assess structural reliability is the Total Reliability Index (TRI) of structures. Yielding Displacement (YD) is an important component for calculations of TRI. Due to the changes in the analysis method, input type, normalization procedure, and the definition of target displacement, there are uncertainties in YD calculation. In structural reliability studies, both loads and resistance parameters are modeled as random variables. Therefore, the YD can be considered as a random variable. This study utilizes incremental dynamic analysis (IDA) to calculate TRI in mid-rise reinforced concrete moment resistant frames with intermediate ductility. The effect of uncertainty caused by YD is calculated based on pushover dynamic analysis. The reliability indices for the six structures of 3, 5, and 8 stories and three and five-span reinforced concrete moment frames show that the uncertainty caused by the YD reduces the TRI, but does not affect the seismic performance of the structure, significantly.

The compacting and mixing processes involving hot mix asphalt during asphalt production can lead to air pollution as a result of a high volatile organic compound. An alternative solution that can reduce greenhouse gas emissions is by using warm-mix asphalt (WMA). A proper application of additives to the WMA can improve the asphalt mixture's strength, durability, and workability. In this study, a 60/70 grade asphalt binder was added with 5% of crumb rubber (CR) and three different WMA additives at the recommended dosages, namely Sasobit, Cecabase, and Rediset. The wet method was used to blend the additives with virgin asphalt binders. The mixing and compacting temperatures were set at 135°C and 125°C, respectively, to mix the asphalt mixture. Mechanical performance tests were performed to evaluate the impact of WAM additives with CR on asphalt mixture. Based on the results, all the modified asphalt mixtures showed a better mechanical performance than the virgin asphalt mixture in terms of indirect tensile strength, moisture resistance, permanent deformation, and stiffness. Among all the WMA additives, Sasobit with CR showed the most significant impact on the asphalt mixture's performance.

In this study, the replacement of corroded reinforcement with new reinforcement as a rehabilitation method is considered to reduce the impact of corrosion on the performance of reinforced concrete structural elements.Also, the effect of using high-performance concrete with the method of reducing the water-to-cement ratio, as a method for maintenance of reinforced concrete structures, has been analyzed.So, the influence of the above rehabilitation methods for maintenance of reinforced concrete structures on the corrosion initiation time of reinforcement, crack initiation time and crack width of the concrete cover thickness, the service life of a reinforced concrete structure due to corrosion, and corrosion percentage of reinforcement have been investigated.For this purpose, all equations and connection between them for the corrosion phenomenon modeling (including corrosion initiation phase, corrosion propagation phase and cracking) is integrated, and the corrosion parameters are calculated and compared for the marine environmental conditions.The results indicated that, the end time of service life of a reinforced concrete structure due to corrosion (tf) increases 60.54% by applying the new reinforcement as a rehabilitation method.So, in concrete with a water-to-cement ratio of 0.35, the corrosion percentage of reinforcement in the new-reinforcement scenario has decreased by 15.60% compared to the no-repair scenario over 30 years.

Terrorist blast attacks have increased in recent years. Hand bombs are one of the means for terrorist operations because of their dangerous progressive damages. In this paper, a full coupled numerical method is adopted to study the dynamic response of a metro tunnel in the sandy loam. The numerical model is developed using LS-DYNA and will be able to present a realistic behavior for the physics of this phenomenon. In the current study, the ALE method has been used. The air, explosive charge, and soil are considered as ALE’s parts; while, the structure of the tunnel has Lagrangian mesh. Two paths have been studied in the longitudinal and the circular directions for assessing tunnel lining safety. In the free-field state, the accuracy of the model is verified by comparing the peak pressure and acceleration in the soil with the empirical predictions available in the literature. The safety assessment has been done according to blast vibration criteria. The tunnel would not be safe, as per the PPV standard, under the condition of w=500kg and R=4m. Tunnel crowns are the most vulnerable areas while the peak particle velocity is 19cm/s with maximum permanent vertical deformation.

The use of concrete as parent material is now an old technique, but it is widely used today due to its unique characteristics. India has witnessed development in the construction field from Harappa civilization to the British era for many years. Even after independence, in 1947, India has advanced in construction techniques in concerning time. However, improper management, design, and ignorance of repairs and rehabilitation of structure cause the collapse of buildings which causes many deaths to occur every year in Mumbai and throughout the country. But the people living in dilapidated buildings risk their lives. Many people are constrained to live in them due to various reasons like skyrocketing rise in real estate prices, fear of losing their houses after vacating for redevelopment projects. Repair and rehabilitation are significant for preserving the structure’s capacity and increasing its performance capacity, which deteriorates due to aging factors, environmental factors. This paper aims to determine the various risks involved in dilapidated buildings by studying various health and safety factors that affect the age of the building. This research also focuses on scrutinizing various problems faced by the residing people in dilapidated buildings. The methodology adopted in this research is by doing unstructured interviews with a questionnaire survey of tenants, performing field surveys of various structures in the study area, and segregating the buildings based on the building’s various safety and hygienic conditions. The result shows the DI (Dilapidation index) score, which is done based on the comfort level of tenants.

In the current experimental work, the simultaneous effect of fineness modulus, water-to-cementitious materials [W/(C+M)], and also micro silica content were investigated on workability, mechanical and physical properties of high strength concrete. For this purpose, 45 mix-designs were made by selecting five different ratios of micro-silica, three W/(C+M) ratios, and three distributions of particle size and then the slump, compressive strength, elastic modulus, and split tensile strength of each designed concrete mixture were determined. Findings showed that increasing the micro-silica content up to 10 wt% improves the mechanical properties of concrete and then leads to a reduction in strength parameters, so that the effect of changes in the micro-silica content on mechanical parameters of concrete becomes more prominent with increasing and decreasing the fineness modulus of aggregate and W/(C+M) ratio, respectively. It was also observed that increasing the micro-silica content leads to reducing the slump and unit weight of concrete so that this reduction is more noticeable in the low fineness modulus of aggregate and water-cement ratio.

In order to design seismic-resistant buildings, it is necessary to get comprehensive information about their behavior against the forces induced by earthquakes. Seismic design codes have been developed to meet the requirements of a safe and economical structure. According to the structural codes, the designed structures should not be damaged against light or moderate earthquakes so that the members should be had sufficient strength and safety while they should be a ductile complex with a proper structural configuration against severe earthquakes to dissipate the forces caused by ground motions. In the design of steel buildings, the use of moment-resisting frames in combination with braces is a seismic-resistant system. One of these systems is the dual steel moment-resisting frames with zipper braces. In this research, the seismic performance of the moment-resisting frame with the zipper brace system has been studied and its performance has been compared to the performance when the chevron bracing system is used. Three 4-story, 8-story, and 12-story buildings have been selected then they have been modeled by SAP2000 software, and finally, their seismic performances have been evaluated using time history analysis. The structural responses have been compared as comparing the relative displacement of the stories (story drift), the maximum displacement of the roof, and the formation of plastic hinges in the members. The results of the current study have been shown that using a zipper member has been decreased both overall displacement of the structure by about 10 to 30 percent, and also has been reduced the damage index of 4, 8, and 12-story structures by 27, 11, and 12 percent, respectively. The formation of plastic hinges has been directed from horizontal and vertical members toward diagonal members.

The object of this research is to compare the behavior of floating and end bearing stone columns made of recycled aggregates of building debris with natural aggregate. To do so, both types of stone columns were constructed by crushed concrete and crushed brick as recycled aggregates and compared with the same models made of gravel as natural aggregates. All the columns were constructed with the same size, density, and grading in a clay bed. To evaluate the initial quality of materials of the stone columns, the index tests were performed. The results of such tests illustrated the less resistance of recycled materials in comparison to the natural materials; On the contrary, according to the results of the index tests, crushed bricks are not recommended to construct stone columns. Despite the index tests, results of loading on a floating column filed with natural and recycled aggregate were approximately the same, but the bearing capacity of the end bearing column made of natural aggregates was higher than the same model made of recycled aggregates.

Nowadays, Reinforced Concrete (RC) wall-slab systems are being used more extensively due to their effective performance seen in past earthquakes. Progressive collapse is a phenomenon in which all or part of a structure is damaged due to damage or collapse of a small relevant part. The majority of research done in the field of progressive collapse has been on frame-shaped structures. Further, the performance of RC wall-slab structural systems, especially against progressive collapse, has been less studied. In this study, at first, nine concrete buildings of five, ten and fifteen stories with wall-slab structural systems, with the ratio of spans length to the story height (L/H) of 1, 1.5 and 2 and a structural height of 2.75 meters in each story, were designed by the ETABS V16 software. Then, using the SAP2000 software and nonlinear shell-layered elements, nonlinear static analysis was performed by the Alternative Load Path (ALP) method on the models and the results were evaluated. The results demonstrated the relatively high strength of buildings with wall-slab structural systems in withstanding progressive collapse. The rate of vertical displacement of the removal location, the maximum von Mises stress in rebar, the maximum compressive stress and strain in concrete in the interior wall removal scenarios were less extensively compared to the corner wall removal scenarios. In contrast, progressive collapse potential increased significantly with increasing number of stories and the L/H ratio. Also, it was found that, buildings with the wall-slab structural system may exhibit brittle failure behavior influenced by progressive collapse.