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In light of the vast potential for the application of modern energy absorption systems in the structures, the effectiveness of each system should be tested, analyzed, and proved before convincing the structures design companies to use them. In this research, the effectiveness of applying base isolators, viscous and friction dampers and a hybrid system consisted of lead rubber bearing with friction dampers are studied. To quantify the impact of each system, a control structure without any energy absorption system is considered. Base isolators and damper systems are designed according to available international codes. American concrete institute’s codes were used to design the concrete structure frames. All of the considered systems therewith hybrid systems including lead rubber base isolation and viscous dampers have been modeled in ETABS 2018 software. The control structure has an intermediate moment resisting frame with high importance located in a high seismic hazard zone. These models were subjected to time history analysis by using Manjil, Loma prieta, and Imperial Valley Earthquakes records. It was observed that the structural design parameters such as base shears and story drifts were significantly reduced by 76–86% and 44–92%, respectively, compared to the structure without any energy absorption system. Also, the total energy dissipated in the structures equipped with modern energy absorption systems was decreased between 32 and 86% compared to the friction dampers. It should be noted that the studied devices may be used either for the design of a new structure or seismic rehabilitation of the existing structures.

In this study, experiments are conducted to investigate the effect of wall-to-frame connectors on in-plane/out-of-plane (IP/OOP) behavior of the steel frames infilled with autoclave-cured aerated c...

Application of massive data to structural health monitoring (SHM) may lead to serious problems such as difficulty, computational inefficiency, and low damage detectability. This paper proposes inno...

This paper studied the durability, microstructure, and fire behavior of lightweight mortars based on cement, metakaolin (MK), ultrafine ground granulated blast furnace slag (UGGBFS), ceramic waste powder (CWP), and clay brick waste powder (CBWP). Two sets of mixes were prepared with two types of lightweight aggregate including lightweight expanded clay aggregate (LECA) and pumice aggregate. Regarding the durability assessment, the electrical resistivity and water absorption of the mortars were measured. The UGGBFS-based alkali-activated mortar with pumice aggregate exhibited the highest electrical resistivity and lowest water absorption, while CBWP-based geopolymer mortar with LECA showed the lowest electrical resistivity, and the water absorption of this mortar was 62% higher than that of the equivalent cement mortar. In addition, scanning electron microscopy (SEM) images showed that UGGBFS-based mortar developed a dense matrix with few pores; whereas, incomplete geopolymerization and voids were detected in CWP- and CBWP-based mortars. Furthermore, the effect of elevated temperatures ranging from 23 to 800 °C on the compressive strength of specimens was investigated. According to the results, CWP- and CBWP-based mortars showed the best performance and retained about 54% and 49% of their original strength at 800 °C, respectively. Furthermore, a statistical study was carried out on the fire test results to quantify the contribution of different parameters using analysis of variance (ANOVA) method. It was shown that temperature was the most influential parameter.

In this article, in order to find some reliable connection types for avoiding the infill failure, an experimental study is conducted on six half-scale single-story single-bay specimens, including one bare frame and five steel frames with autoclave-cured aerated concrete walls, each having different frame-to-wall connection types. Polyurethane adhesive was used in bed joints of the autoclave-cured aerated concrete walls as a mortar. The specimens were tested under displacement-controlled loading to examine their effect on the in-plane behavior of steel frames. The results suggested that V- and T-shaped connectors can be used as prequalified connectors between the wall and the frame. In specimens with these connectors, the interaction between infill and frame was ignorable and the infill remained intact up to life safety performance level (2.5% drift ratio). Furthermore, the application of these connectors resulted in a two-level performance of the infill whereby the frame stiffness degradation and strength deterioration after the drift ratio of 2.5% was compensated.

This study investigated the effects of combined utilization of wollastonite particles and recycled waste ceramic aggregate (RWCA) on high strength concrete (HSC) properties. Two groups of mixtures were manufactured: 1) concrete mixtures in which cement was partially replaced with wollastonite at values ranging from 10% to 50%, and 2) mixtures in which wollastonite was used at the aforementioned dosages and 50% of natural coarse aggregate was replaced with RWCA. In addition, 10% of cement weight micro-silica was added to all mixtures. The concrete behavior in terms of strength, durability, resistance against acidic environment, and performance under elevated temperatures ranging from 20 °C to 800 °C was assessed. Furthermore, the effect of wollastonite and RWCA inclusions on the microstructure of samples was studies using scanning electron microscopy (SEM). It was shown that wollastonite has an adverse impact on concrete workability and compressive strength. For example, 34% and 6% reduction in slump and 28-day compressive strength at wollastonite dosage of 50% was observed, respectively. On the other hand, the 28-day splitting tensile strength and flexural strength were respectively increased by 4.25% and 10% at 50% wollastonite content with respect to the control concrete. Furthermore, inclusions of RWCA improved the performance of concrete. For example, the 28-day compressive strength was increased by 24% in mixture with 50% wollastonite content with reference to the control concrete. In addition, the strength retention at 800 °C for mixture with RWCA was 16% higher than that of mixture without RWCA. Thus, it was concluded replacing coarse aggregate with RWCA improves the strength and durability properties of concrete and replacing 30% of cement with wollastonite particles strikes a balance between workability and strength of concrete.

This paper presents an extensive experimental study to investigate the possibility of using sugarcane bagasse ash (SCBA) as a partial replacement of cement in ordinary, lightweight, and self-compacting concretes. For this purpose, specimens containing 5, 10, 15, 20, and 25% SCBA in addition to a control specimen were prepared. To evaluate the mechanical properties of concrete specimens, compressive strength, tensile strength, impact resistance, workability, water absorption, and ultrasonic pulse velocity (UPV) tests were performed. The results indicated that improvements in strength and impact resistance in lightweight concrete are observed as compared with the control sample when cement was replaced with bagasse ash at 5%. It was also found incorporation of BA improved durability and quality of SCC.

Regarding the high interfacial shear stresses at end-plate, and end-plate cover separation in externally bonded methods, bar end-interfacial debonding and bar-end cover separation in near-surface mounted technique, a hybrid strengthening method called combined externally bonded near-surface method was proposed. In this method, the externally bonded and near-surface mounted techniques complement each other and mutually overcome their limitations. The purpose of this study is to numerically investigate the flexural strengthening efficiency of reinforced concrete beams with combined externally bonded FRP sheets and near-surface mounted FRP rods. The numerical analyses were conducted with finite element software ABAQUS 6.11, which can accurately simulate the experimental investigations on the flexural behavior of reinforced concrete beams strengthened with FRP composites. Validation of finite element simulation was confirmed first by making a comparison with the experimental study presented in the literature for both un-strengthened and strengthened beams with FRP materials. The verified model of the un-strengthened beam, which serves as a control beam, was used to simulate reinforced concrete beam strengthened with externally bonded FRP sheets and combined externally bonded near-surface mounted technique. The numerical results of mid-span bending moment deflection, ultimate bending moment, failure deflection, and ductility index were reported. Based on the results of this study, it is concluded that the developed finite element models for the externally bonded, near-surface mounted, and combined externally bonded near-surface techniques can be used by structural engineers as an alternative solution in design-oriented parametric studies of strengthened reinforced concrete elements. The performance of the combined externally bonded near-surface mounted technique was confirmed by making the comparison between the results of the intended method with other strengthening techniques.

The preliminary and inevitable interest in the use of partial replacements or by – products as complementary pozzolanic materials was mostly induced by enforcement of air pollution control resulted from cement production industry. Rise husk is by- product taken from rice mill process, with approximately the ratio of 200 kg per one ton of rice, even in high temperature it reduces to 40 kg. This paper presents benefits resulted from various ratios of rice husk ash(RHA) on concrete indicators through 5 mixture plans with proportions of 5, 10, 15, 20 and 25% RHA by weight of cement in addition to 10% micro- silica (MS) to be compared with a reference mixture with 100% Portland cement. Tests results indicated the positive relationship between 15% replacement of RHA with increase in compressive strengths by about 20%. The optimum level of strength and durability properties generally gain with addition up to 20%, beyond that is associated with slight decrease in strength parameters by about 4.5%. The same results obtained for water absorption ratios likely to be unfavourable. Chloride ions penetration increased with increase in cement replacement by about 25% relative to the initial values (about less than one fifth).

Seismic vulnerability of power substations, one of the key components of a power network, has been observed in previous earthquakes. Generally, a power substation is comprised of several components such as the main power transformer (PTR), circuit breakers (CBs), disconnecting switches and post insulators. Each of these has its own functionality and the overall performance of the power substation depends on these components. Previous studies have mostly focused on the seismic vulnerability of power networks rather than on the interdependencies in a single substation. In this paper, the seismic vulnerability of power substations in previous earthquakes is discussed first, and then some practical techniques for preventing seismic vulnerability are presented. Finally, by considering experts' practical opinions about the functional role and importance of each of piece of equipment in a power substation, a deterministic approach using the analytic hierarchy process is introduced, which can estimate the proportional contributions of the related equipment to the seismic performance risk of a substation. The operational significance of all the equipment in a power substation is not the same; under emergency conditions, there is a fundamental need of such pieces of equipment as PTRs, CBs and also bus bars.

With increasing trends towards the broader usage of concrete and warning depletion of natural resources of aggregates, it seems reasonable to find mineral additives or binding materials of different types as ingredient of concrete. Accordingly, wide usage of light weight concrete lies on some main structural applications as reduction of total dead, seismic loads, environmental pollution, and labour cost. This paper tries to investigate the properties of light weight blended concrete containing lime stone powder (LP), micro-silica (MS), pumice, and leca in various proportioning rateing as a partial replacements of cement. Utilization of these additives on the compressive strength, tensile strength, water absorption coefficient, acid resistance, and impact resistance examined experimentally in various curing conditions at the ages of 7 and 28 days to evaluate the combined effect of micro-silica and lime stone incorporation on strength and durability properties of light weight concrete, along with introduction of optimum replacements. For this purpose, 10 lime-stone based concrete mixtures were prepared with proportions from 0 to 20%, and constant values of 10% micro-silica and w/c ratio. From the results, it was indicated that addition of lime stone powder in concrete reduces short-term properties as well as the compressive strength. Optimum levels of powder replacements can serve as sustainable and durable concrete, also environmental and economic benefits.

Recent earthquakes have shown that Electrical Power Substations apparatuses are seismically vulnerable. This causes to disrupt the power supply in many cases, and therefore their seismic evaluation with high reliability is significantly important. Using fragility curves is a common practice for assessing seismic vulnerability. In general, fragility curves are based on only one intensity measure (IM), such as peak ground acceleration (PGA). This study has attempted to propose multivariate fragility analysis. One of the major advantages of this developed multivariate fragility analysis is to more reliably determine the seismic vulnerability of a region. A 420 kV circuit breaker (CB) was modeled and analyzed by using finite element technique. The results show that by adding another IM as peak ground velocity (PGV) the dispersion of the created data decreases to a great extent and therefore, the developed fragility surfaces helps conducting the seismic risk evaluation of electric power system components with higher level of reliability. Based on the obtained numerical results it can be expressed that for moderate damage state the fragility values are not much dependent on the PGV variation, while for severe damage state the dependence of fragility values on PGV is noticeable, particularly for PGA values in range of 0.1–0.7 g.

Recent earthquakes have shown that Electrical Power Substations' equipment are seismically vulnerable, resulting in disruption of power supply in many cases, and therefore their seismic vulnerability evaluation is of great importance. Power transformers (PTR) are critical elements in a power substation, so their proper functioning during and after earthquakes is essential. In this study first, seismic vulnerability of PTRs in past earthquakes is reviewed and failure modes are discussed, then 3D finite element modeling and time-history analysis were performed using 99 three-component original accelerograms of ground motions. Seismic analytical fragility curves of a 400 kV PTR are obtained in two damage states using Multiple Stripes Analysis method which estimates the fragility values while minimizing the required number of structural analysis. The results show that using extra high strength C130 porcelain, the PTR's bushing wouldn't encounter with moderate damage and it might be also acceptable for ground motions with peak ground acceleration (PGA), lower than 0.4 g. It can also be expressed that utilizing specific seismic considerations such as base-isolation, providing dampers or using composite bushing is necessary for PTR's porcelain bushing in seismic regions (PGAs ≥ 0.5 g).

Ground granulated blast furnace slag (GGBFS) and copper slag (CS) are industrial waste by-products, which are mostly discarded in landfills. Alternatively, they can be used in concrete production to reduce the consumption of cement and natural aggregates. One of the applications that can benefit from heavy-weight aggregates such as CS, is concrete tailored for radiation shielding purposes. However, there was no prior study on effect of combined use of CS and GGBFS on radiation shielding capability of concrete. This study is aimed to address the effect of GGBFS and CS content on gamma-ray shielding and mechanical performance of high-density concrete. For this purpose, concrete mixes were prepared with different percentages of GGBFS (0–60%) and CS (0–100%) as a partial replacement of cement and natural fine aggregate, respectively. The workability, compressive strength, splitting tensile strength, and radiation shielding capability of concrete mixes subjected to 137Cs and 60Co point sources were evaluated. Based on the test results, the workability of fresh concrete was enhanced (up to 63%) with increasing replacement ratios of GGBFS and CS. The optimum compressive and splitting tensile strengths were obtained by incorporating 30% GGBFS and 50% CS, which were about 20% higher than that of the control mix. The linear attenuation coefficient increased slightly with GGBFS content. On the other hand, the use of heavyweight CS aggregates increased the linear attenuation coefficient by up to 31%. Results showed that concrete made with 60% GGBFS and 100% CS exhibit superior radiation shielding capability and satisfies the strength requirements for structural applications. Therefore, it is suitable for radiation shielding of structures such as healthcare centers. Finally, the ecological analysis revealed that the concrete made with recycled materials is Eco-friendlier and contributes to sustainable development of construction industry.

Copper slag (CS) is an industrial waste, which is generally disposed of in landfills, posing threats to the environment. Alternatively, it can be used as natural aggregate replacement in concrete/mortar, however, it results in a significant increase in material density, production and handling cost. The use of crumb rubber in combination with CS can overcome these problems, but there was no prior study on effect of such combination on the properties of alkali activated mortars (AAMs). The primary aim of this study is to address the problem stated above by replacing CS with 5, 10, 15% (by volume) crumb rubber in alkali-activated slag mortars. Furthermore, the effect of pre-treatment of crumb rubber aggregates with sodium hydroxide (NaOH) solution for 1 h and 24 h on workability, compressive strength, flexural strength, water absorption, thermal conductivity, and microstructural properties of mortar mixes was investigated. Based on the test results, the use of crumb rubber resulted in inferior workability and mechanical strength, but better thermal insulating capability as compared to the control mix. Alkali treatment promoted the rubber-binder bond and effectively enhanced the strength of mixes, especially at an early-age (up to 59%), however, alkali treatment for 24 h drastically reduced the workability of fresh mix. Thus, it is recommended to use 10% crumb rubber pre-soaked in NaOH solution for 1 h to achieve acceptable performance. Finally, the economic and ecological analysis results revealed that the produced mortar is beneficial to the environment.

This study investigated the optimum bacterial concentration and calcium lactate content in mortars containing recycled concrete aggregate (RCA) as full replacement of natural fine aggregate (NFA) for the first time. For this purpose, bacterial mortars with cells concentration of 103, 105 and 107 cells/ml were prepared. Calcium lactate was used as the organic precursor at dosages of 1%, 3%, and 5% of cement weight. The mechanical, durability, crack healing, and microstructural characteristics of the bacterial mixes were examined and compared to those of the control mix. The results indicated that incorporating bacterial cells with concentration of 105 cells/ml treated with 1% calcium lactate led to the optimal mix. The 28-day compressive strength of the optimal mix increased by 21% over that of the control mix. The lowest water absorption was also recorded for this mix, which was about 7% lower than that of the control mix. The scanning electron microscopy (SEM) images of the optimal mix showed a dense and compact microstructure as a result of calcite precipitation, which filled the air voids and reduced the pore size. Increasing the calcium lactate content lowered the quality of the pore system due to overproduction of calcium carbonate (CaCO3) crystals. This was confirmed by the results of porosimetry test using mercury injection method where the sample prepared with 5% calcium lactate and bacterial concentration of 103 cells/ml showed 450% higher total porosity as compared to the control sample. On the other hand, crack healing analysis revealed that the maximum healing in surface cracks occurred at the maximum bacterial concentration and calcium lactate content.

In this paper, the optimum alkali activator solution properties in alkali-activated pastes based on ground granulated blast furnace slag (GGBFS) and micro-silica (MS) were investigated. For this purpose, sodium hydroxide (NH) solutions with molarities of 8 M, 12 M, and 16 M were prepared and mixed with sodium silicate (NS) solutions at NS:NH ratios of 1.0, 2.5, and 4.0 to produce the final activator solution. Two sets of pastes were manufactured: (1) pastes based on GGBFS, and (2) pastes in which 10% by weight of GGBFS was replaced with MS. The fresh density increased with increasing NH molarity and NS:NH ratio; whereas, the final setting time reduced with an increase in the aforementioned properties. With regard to the hardened paste, the tests of compression strength, porosity, and electrical resistivity were performed. According to the results, pastes activated with a 12 M NH solution and NS:NH ratio of 2.5 showed the highest compressive strength and electrical resistivity and the lowest porosity. Furthermore, the use of MS increased the compressive strength and electrical resistivity of the optimum paste by 27% and 64%, respectively, over those of the same paste with 100% GGBFS. In the final part, linear regression models were developed to predict the properties of GGBFS and GGBFS/MS pastes. Based on the findings of this study, it is possible to produce a zero-cement paste based on GGBFS and MS, with final setting time of 25–35 min and 1-day compressive strength of 60–70 MPa by using the optimal alkali activator solution, which can be used for repair purposes due its proper setting and strength properties.

This study presents the results of an experimental evaluation of the performance of high strength concrete (HSC) with basic oxygen steel-making (BOS) slag and nano-silica respectively used as a partial replacement of sand and cement. The properties of fresh and hardened concrete specimens containing 25%, 50%, 75%, and 100% BOS as partial replacement of sand and 2% of cement replaced with nano-silica were evaluated. According to the results, concrete samples containing nano-silica with higher BOS percentages, demonstrated improvements in strength and durability properties, while workability was reduced. For example, at 50% BOS content, about 18% increase in compressive strength and 50% reduction in water absorption was observed, while slump was reduced by 40%.