Civil Engineering Infrastructures Journal
Volume:54 Issue: 1, Jun 2021

The inherent scour process around the bridge piers needs to be considered and crucial to ensure a sustainable and economical bridge design. The performance of any scour protection/controlling devices around bridge piers is determined on how each device counters or minimize the scouring process. Besides the usually adopted bed armouring, abundant studies have been conducted to evaluate the efficiency of flow-altering countermeasures in reducing local scour depth. The flow changes due to the rigid pier are modified in a way to reduce the impinging effect on the bed. This paper discusses the performance and feasibility of self-protected piers, defined as a pier without any additional structure built either next to or at a distance away from the pier. We paid attention to the efficiency of the proposed countermeasures in terms of possible maximum scour reduction and provide the best configuration of each self-protection pier. This review consists of analysis on the openings on pier including internal tubing, slot and pier groups, and modified pier shapes as the flow-altering, self-protected countermeasure alternatives

In this study, the impact of Negative Skin Friction (NSF) on composite piles concerning different variables such as different pile sections, the amount of concrete and steel consumption, and various interaction coefficients of the pile-soil system in both solid and hollow conditions are evaluated using numerical methods. Besides, the effect of the variables considered on the negative skin friction and pile’s settlement is investigated. Numerical analyses were performed using ABAQUS and MATLAB. The results showed that the amount of frictional stress on the pile decreases if the hollow sections are used. However, the hallow pile experiences more settlements than other piles’ models. On the other hand, if the amount of consumed steel in a pile is reduced, the amount of negative skin friction induced in a pile decreases, while the pile settlement increases. After examining the Finite Element of concrete piles in fine-grained soils, the safety surface of the suggested numerical relationship was considered in the phenomenon of negative friction on the pile. For this purpose, considering the uncertainty parameters such as mean, variance and probability function for overcharge, soil parameters, dimensions and different types of the single pile, the amount of settlement, the stress created on the pile, the position of neutral plane on the pile and drag load were calculated using the proposed relationship. Finally, the safety surface of the proposed relationships or comparisons of a Finite Element results in a close approximation to the real models was computed.

The use of Edge Notched Disc Beam (ENDB) sample has been proposed as a suitable geometry in performing fracture tests in different loading modes. The most important features of the ENDB samples include easy making, quick and easy sampling, simple testing, and the ability to examine a wide range of pure and combined loading modes. Using a wide range of fracture tests, a statistical model is proposed to predict the stress intensity factors of asphalt mixtures in terms of the pure torsion mode (mode III) loading in this study. To this end, the experiments were carried out at different temperature conditions (-5, -15 and -25 °C), different loading conditions (0.5, 1 and 5 mm/min), and on control and modified asphalt mixtures with different percentages of polyolefin-aramid fibers. The results showed that, with increasing the fiber content and loading rate, the fracture strength increased with average 25%, while an increase in fracture toughness due to lower temperature had an effect of less than 5%.  Using the Response Surface Method (RSM), the prediction model of stress intensity coefficients of asphalt mixtures was presented in the pure torsion mode. The results of the proposed models had a good correlation with the results of the conducted fracture tests.

In the present study, Radial Basis Function (RBF) neural networks are applied to forecast the compressive strength and elastic modulus of Self-Compacting Concrete (SCC). To construct the models, different experimental specimens of diverse kinds of SCC are gathered from the literature. The data used in the networks are classified into two different sets of input parameters. The results revealed that the proposed RBF models can accurately forecast the properties of SCCs with low test error. Furthermore, a comparison between models with two different sets of inputs proves that the selected parameters as input variables, straightly impress the precision of the networks, in the prediction of the intended outputs.

Unexpected loading, induced by severe earthquake or blast, could cause local damage to a structure. In this case, the structure has the potential of progressive collapse phenomenon. Hence, further consideration is required to mitigate the consequences of such loading. This study is aimed to evaluate the progressive collapse capacity of steel moment frames with different heights under column removal conditions. Seven and twelve story buildings modeled in different conditions in order to view effects of various parameters like the out of plane frames, column removal location, and the height of buildings in the results. One of the middle column and/or the corner columns is removed in order to evaluate the effect of column removal location in response of structures. The General Services Administration and the Department of Defense guidelines are considered for defining load combination for the analysis of the collapse. Nonlinear dynamic analysis is conducted in order to obtain the ductility demand of structures when the out of plane effect is considered. The structures have welded cover plate connections, designed for high-seismic zone area. For evaluating the response of the structures, for each connection at the point of column removal, maximum vertical displacement is measured. For Finite Element analysis, a sub-assemblage of structures is modeled using ABAQUS software and the ability of beams deformation and it’s out of plane effect is measured.

Soil cement is a mixture of Portland cement, soil and water, in which hydration of cement and compaction causes the materials’ constituents to bond together makes a dense and durable composition with low permeability and abrasion resistant. Since most of the recent researches are focused on the addition of nano-SiO2 on concrete, in this paper it has been attempted to use nano-SiO2 particles in soil-cement and observe the effects. Due to the fact that in concrete there are no particles passing sieve 200 and this restriction does not apply to soil-cements, some tests were carried out on the nano-SiO2 + soil-cement matrix because of the meaningful difference between concrete and soil-cement. The test procedure consists of moisture-dry density, unconfined compressive test and hydraulic conductivity. In these tests, silica fume (with specific surface area of 21 m2/g), nano-SiO2 (with specific surface area of 200 and 380 m2/g) were added to soil-cement. The results show that adding certain amounts of nano-SiO2 particles to the soil-cement matrix can improve the compressive strength and reduce permeability and speed hydration reactions in the matrix in presence of nano-SiO2 particles.

This study is the first investigation to assess the variations of physical and chemical characteristics and biodiversity of planktons in offshore water column and chlorophyll-a and b, during the two monsoons at Chabahar Bay, to evaluate the water quality. To this end, 27 surface water samples in pre-monsoon (May, 2012) and totally 60 surface and deep water samples in post-monsoon (December, 2012) were collected from 9 and 10 stations at depths between 3.8 to 13.6 m in Chabahar Bay, respectively. The results showed that water salinity and pH with low variations were relatively higher in post-monsoon. The average of water alkalinity levels in pre- (2.42±0.02 mmol H+/kg) and post- (2.44±0.01 mmol/kg) monsoons were comparable to that of oceanic surface water (2-2.5 mmol H+/kg). In this study, 66 phytoplankton genus and species belonging to 13 groups were identified in pre-monsoon. Results demonstrated that nutrients were at higher levels inside the Chabahar Bay. Moreover, the physicochemical parameters of water samples were investigated and compared with international standards and data from other marine ecosystems. The results indicated that the water quality falls within the stipulated range of acceptability and sampling area can be classified as a good, stable, and healthy aquatic ecosystem.

The fundamental concepts of biogeography-based optimization (BBO), a meta-heuristic algorithm, have been inspired by the geographical distribution of animals. This algorithm does not need a starting point, and performs a random search instead of a gradient-based search. In this article, for the first time, the weights of 2D and 3D trusses with specific geometries and different stress and displacement constraints have been optimized by using the BBO approach. Also, in this work, the numerical results achieved by other researchers through various optimization techniques have been compared with the results obtained from the Particle Swarm Optimization (PSO), Differential Evolution (DE) and BBO algorithms. It has been demonstrated that the search and exploration capability of the BBO algorithm is superior to that of the DE and PSO algorithms, and that it achieves better results than the other optimization techniques considered in this paper. This superiority is due to the excellent exploration capability of the BBO algorithm and the fact that it achieves a favorable optimal solution in the initial iteration.

Two fire accidents took place in the Plasco Tower in Iran and Grenfell Tower of London in 2017. Although both of them have led to human tragedies, post-earthquake fire can cause more irreparable damages and catastrophes in larger extents. Engineering structures are subjected to different loads during their lifetime, which may cause damage or secondary loading effects. Evaluation of durability and stability of fired structures and the effects of seismic loading are considered to be significant parameters in fire engineering. The aim of this study is to evaluate and compare durability of reinforced concrete and steel frames during fire loading and post-earthquake fires. In this study, two 7-story steel and reinforced concrete frames are exposed to the fire load. At first, steel and concrete sections are put under various thermal loads in order to compare the method of their heat transfer. Then, the effects of crack on heat transfer of concrete sections are studied. Afterwards, the selected frames are exposed to the fire and post-earthquake fires. The results indicated that cracking and strength reduction due to seismic loading can decrease the durability of reinforced concrete frame in post-earthquake fire scenarios. However, the durability of steel frames has no significant relationship with the seismic loading and their durability are almost the same in the fire and post-earthquake fire scenarios.

In this paper, an analytical method is developed for the axisymmetric dynamic response of a finite thickness liquid layer overlying a transversely isotropic porous solid half-space due to body waves. Potential functions and integral transforms are used together to handle the equations of wave motion in two media. The time-harmonic excitation with axisymmetric shape is assumed to be distributed in the interface of liquid and porous media. Green’s functions of stress and displacement are derived as closed-form integral expressions. Demonstration of the effect of the liquid thickness, degree of material anisotropy, and frequency of excitation on the dynamic response is considered here. Numerical results for a uniform distributed disk load are comprised with the existing elastic and poroelastic solutions to illustrate the quality of the method. The results of the current paper can be used in analysis and modelling the rigid or flexible foundations in marine structures.

The reinforced concrete flat slab structures are highly susceptible to punching shear failure. This occurs due to the transferring of shear force and due to the bending moment between the slab and the column. The initial local failure and the following redistribution of load can lead to punching failure of the slab in the adjacent column locations. This issue can collapse an entire building or a huge portion of a structure. Hence, an alternate load path method is necessary for preventing the catastrophic failure of the buildings. Compared to the moment frame buildings, flat slab buildings are more prone to the progressive collapse. Thus, the designing of flat plate structures demands more attention and study. Due to higher construction costs and limitations in the test set up, the researchers have adopted scale down structures for the experimental studies. The progressive collapse behavior of the prototype structures is usually analyzed using both analytical and numerical simulations. This paper discusses the existing researchers on the analytical study, experimental study, and numerical simulations of flat slab structures along with various load resisting mechanisms to mitigate progressive collapse. Further, various strengthening techniques available in the literature for the flat slab structures have been discussed. A parametric study and comparison of different strengthening techniques are also performed in this work.

Nondestructive Testing (NDT) methods have extensively been used to assess the conditions of civil infrastructure in the recent decades. Among various NDT techniques, Impulse Response (IR) has a vast application due to its simplicity and low cost. However, factors such as reflections from changes in impedance along the investigated members can adversely influence the success of the method. Numerous numerical and experimental studies have already been performed to evaluate the effect of change in mechanical impedances such as bulging, necking and similar anomalies. In this study, the effect of the presence of joints connecting the investigated members to other members, as another source of impedance change, is demonstrated.  A three-story steel-concrete composite column of a building was selected for testing and IR tests were conducted. The obtained mobility graphs were clear, and the height of the column was easily measured with an acceptable error. The results of this study show that although the joints located between the top and bottom of the tested member are sources of change in mechanical impedance, they do not result in concealing the resonant frequencies from the wave reflected from the bottom of the member. Thus, IR method seems to be applicable in determining the length of prismatic members with intermediate joints such as piles of unknown bridge foundations with bracing and columns of buried buildings.