Effects of Seawater Corrosion and Freeze-Thaw Cycles on Mechanical Properties of Fatigue Damaged Reinforced Concrete Beams

The effects of seawater corrosion and freeze-thaw cycles on the structural behavior of fatigue damaged reinforced concrete (FDRC) beams were experimentally studied. Results show that the residual strength of FDRC beams reduces as the fatigue load level (the ratio of maximum fatigue load to the ultimate static load) increases. The reduction in the loading capacity of FDRC beams in atmosphere environment was about 6.5% and 17.8% for given fatigue load levels of 0.2 and 0.3, respectively. However, if FDRC beams are exposed to the environment of seawater wet-dry cycles or to the environment of alternating actions of freeze-thaw and seawater immersion, as expected during the service life of RC bridge structures in coastal regions or in cold coastal regions, a more rapid reduction in the strength and stiffness of the beams is observed. The significance of an accurate simulation of working load and service condition RC bridge structures in coastal regions and cold coastal regions is highlighted

3,4-Dihydr­oxy-N′-(2-hydroxy­benzyl­idene)benzohydrazide–methanol–water (2/1/3)

The asymmetric unit of the title compound, C14H12N2O4·0.5CH4O·1.5H2O, consists of two Schiff base mol­ecules, three water mol­ecules and one methanol mol­ecule. The dihedral angle between the two benzene rings is 7.8 (2)° in one of the mol­ecules and 4.0 (2)° in the other. Intra­molecular O—H⋯O and O—H⋯N hydrogen bonds are observed. Mol­ecules are linked into a three-dimensional network by O—H⋯O and N—H⋯O inter­molecular hydrogen bonds

On the microstructure and mechanical property of as-extruded Mg-Gd-Y-Zn alloy with Sr addition

In this study, microstructure evolutions of Mg-6Gd-3Y-0.1Zn-xSr (x=0, 0.2, 0.6) alloys (named as sample 0Sr, 0.2Sr, 0.6Sr) during heat-treatment and extrusion were investigated. As-cast sample 0Sr contains typical long period stacking ordered (LPSO) phases and MgRE. With Sr addition, amounts of LPSO phases decrease and are gradually replaced by the MgSr phases. After homogenization and annealing treatment, profuse strip LPSO phases readily precipitate in grain interiors of sample 0Sr, while only MgSr and MgRE phases are detected in samples 0.2Sr and 0.6Sr. It suggests that the Sr addition would inhibit LPSO phases. After extrusion, the bimodal grain structures, the bulk and strip LPSO phases are detected in sample 0Sr, which can contribute to providing strengthening and extra strain hardening. In as-extruded sample 0.2Sr, finer recrystallized grain size, bulk MgSr and LPSO phases (micron-scale) and MgRE phase (nano-scale) are found due to the pre-annealing treatment. However, lower amounts of both nano-sized and macro-sized LPSO phases lead to the low ultimate strength (300 MPa). In sample 0.6Sr, the strip LPSO phases are readily formed even though the length and total amounts of LPSO phases decrease. More bulk MgSr phases and LPSO phases are also precipitated, which lead to the more superior yield and ultimate strengths of 0.6Sr sample under higher temperature, as compared with the 0Sr sample

Chloride Diffusivity and Life Prediction of Cracked RC Beams Exposed to Different Wet-Dry Ratios and Exposure Duration

Effects of crack width, wet-dry ratio, and exposure duration of wet-dry cycles on chloride ingress of RC beams were experimentally studied. Crack widths of 40, 70, 90, and 120 microns were, respectively, induced by three-point flexural loading and four wet-dry ratios (seawater spraying 1 d in one wet-dry cycle) of 1 : 3, 1 : 7, 1 : 11, and 1 : 15 were selected. Chloride contents of RC beams were tested every 32 d (or 16 d) of wet-dry cycles. Results show that chloride content increased significantly when crack width was larger than 90 microns and wet-dry ratio was 1 : 3, and it increased slightly when crack width was 120 microns and wet-dry ratio was 1 : 7, 1 : 11, and 1 : 15. The chloride content on steel bar surface became the largest when crack width was less than 90 microns and wet-dry ratio was 1 : 7, and while crack width was equal to or greater than 90 microns and wet-dry ratio was 1 : 3, it was the largest. Based on the testing results, chloride diffusion model and prediction model of residual service life of RC beams were suggested considering combined effects of crack width and exposure duration. The predicted residual service lives were corresponding well with experimental results and they decreased as crack width increased

Urban space simulation based on wave function collapse and convolutional neural network

In this paper, we propose a pipeline of urban space synthesis which leverages Wave Function Collapse (WFC) and Convolutional Neural Networks (CNNs) to train the computer how to design urban space. Firstly, we establish an urban design database. Then, the urban road networks, urban block spatial forms and urban building function layouts are generated by WFC and CNNs and evaluated by designer afterwards. Finally, the 3D models are generated. We demonstrate the feasibility of our pipeline through the case study of the North Extension of Central Green Axis in Wenzhou. This pipeline improves the efficiency of urban design and provides new ways of thinking for architecture and urban design

Bond Effects between Concrete and Steel Bar Using Different Diameter Bars and Different Initial Crack Width

The importance of an accurate simulation of service conditions in the bond performance of reinforced concrete structures in coastal regions is highlighted. Four widths of initial crack of 0, 80, 150, and 210 microns were artificially made by inserting slice into bond specimens during concrete casting. Three bar diameters of 10 mm, 14 mm, and 18 mm were selected. At 28 days, the bond specimens were exposed to the environment of wet-dry cycles of seawater and atmosphere for another 90 days. The pull-out test was then conducted and chloride contents were tested at crack area along 40 mm depth. Results show that, for the specimen with 10 mm bar diameter, cracks width of less than 80 microns vanished rapidly during wet-dry cycles; for other specimens, cracks width of 100–150 microns decreased slightly. However the cracks of width more than 200 microns increased gradually; the chloride content decreased along the depth of concrete, and the chloride content increased as the widths of initial cracks increased or as the bar diameters increased. The ductility of bond specimens decreased as the diameter increased

Bis{2-[2-(isopropyl­ammonio)ethyl­imino­meth­yl]-6-methoxy­phenolato}nickel(II) dithio­cyanate

The title complex, [Ni(C13H20N2O2)2](NCS)2, consists of a centrosymmetric mononuclear four-coordinate nickel(II) complex cation and two thio­cyanate anions. The Ni atom is located on an inversion center and is coordinated by two phenol O atoms and two imine N atoms from two equivalent Schiff base ligands, in a square-planar geometry. In the crystal structure, the amino H atoms are involved in N—H⋯O hydrogen bonds with the phenol and meth­oxy O atoms of the ligand, and in N—H⋯N hydrogen bonds with the N atoms of the thio­cyanate anions, which sit above and below the Ni atom

2-Chloro-N′-(2-hy­droxy-3,5-diiodo­benzyl­idene)benzohydrazide

In the title compound, C14H9ClI2N2O2, the dihedral angle between the benzene rings is 65.9 (2)° and an intra­molecular O—H⋯N hydrogen bond generates an S(6) ring. The mol­ecule has an E conformation about the C=N bond. In the crystal, mol­ecules are linked into C(4) chains propagating in [001] by N—H⋯O hydrogen bonds