Methodology for the Study of Residual Temperature Stresses in the Butt Contour of a Welded Joint Made of Carbon and High-Alloy Structural Steels during Multi-Pass Welding

The method of investigation of residual temperature stresses in the butt contour of the welded joint "shell – plate" made of carbon and high-alloy structural steels during multi-pass welding is described. The temperature problem was solved on the basis of the obtained experimental data of temperature measurement at the reference points of the structure during the application of the rollers. A solution is proposed that takes into account several stages, each of which corresponds to a specific intermediate temperature field due to the peculiarities of welding technology. The evaluation of residual stresses was carried out on the basis of the energy theory of plasticity, taking into account the dependences of the yield strength and elastic modulus of welded metals on temperature.

Numerical Analysis of Fire Water Storage Tank under Seismic Loading

Maintenance and continuously monitoring the condition of above ground storage tanks are significant when the tanks are placed in service. The American Petroleum Institution (API) 653 and other international codes provides the minimum requirements for inspection & maintaining the integrity of tanks during its service. The tank settlement is one of the major threats for tank’s integrity. In this paper, a storage tank is assessed for uniform settlement under various loading condition such as seismic, dead load, static load, corrosion loss of shell plate etc. In the present study, a finite element model is designed with uniform settlement condition and study of its governing hoop stress at shell plate has been carried out under different loading conditions. A fire water storage tank (constructed with IS 2060 GR. B material) and different seismic zones in India are taken for this study. The finite element analysis simulation shows that increase of hoop stress in the bottom shell course due to uniform settlement, the decrease in plate thickness and with different seismic active regions. Moreover, the maximum stresses have been observed at shell bottom course (close to bottom plate).

An investigation of strength degradation due to thickness plate reduction on Ferry Ro-Ro Ship’s Hull

Old ships will experience a degradation of the structural strength after receiving repeated loads. Decreased strength performance is also caused by structure shape and structural dimensions changes. In steel ships, Dimensional changes will be discovered when the ship is docked, because the material undergo corrosion causing in thinning the shell plate. In this study, a thickness reduction of the shell plate has been simulated to determine the longitudinal response of the ship’s structure. A Finite element analysis of ferry Ro-Ro ship’s hull was carried out using ANSYS package program. The simulation was carried out to exceed the allowable limit for reducing the thickness plate by the Indonesian Classification Bureau (BKI), which is 20% of the initial plate thickness. Based on simulation result, it was found that an increase of stress at each variation of the reduction in hull plate thickness in hogging and sagging conditions.

Natural Frequency Measurements of the Fluid-elastic-coupled Shell Plate Vibration in a Large-sized Cylindrical Steel Tank by Microtremor Observations

Microtremor observations measured the natural frequencies of the fluid-elastic-coupled shell plate vibration (bulging) in a large flat-bottomed cylindrical steel tank with a 125,000-m3 capacity. Five peaks appear in the observed microtremor spectral ratios of the top or mid-height of the shell plate to the bottom on the tank foundation. Comparing the spectral ratios to the solutions obtained by FEM eigenvalue analysis assuming a fixed base suggests that the five peaks are the bulging modes of (m, n)=(1, 1 to 5), where m and n denote the vertical order and the circumferential wavenumber, respectively. The measured non-soil-coupled natural frequencies from the spectral ratio agree fairly well with those obtained from FEM analysis. The measured natural frequencies of the fundamental mode (m=n=1) also agree well with those projected by a simplified equation developed under the assumption of a fixed base, which is adopted in the seismic codes of the Japanese Fire Service Act. This equation should provide a reliable soil-coupled natural frequency of the fundamental mode for a tank situated on firm ground in which the storage-soil-coupled effects are presumed weak. Additionally, a simple method is presented to determine the non-soil-coupled natural frequency of the fundamental mode from the observed microtremor spectral ratios without referencing the FEM eigenvalue solutions. This simple method works very well for the tank examined.

Complex of Settlement Gorodishche-3 Belonging to Fominsky Stage of Kulaiskaya Culture

The article introduces materials of the Fominsky stage of the Kulaiskaya culture from the site in the Itkul microdistrict located in the forest-steppe Altai. It gives a detailed description of the site and its excavation. The site covered an area of 320 m². The excavation revealed a semi-dugout with a pit area of 25 m² and a corridor-type exit, a household building, and other structures. The author focuses on the moat and earthwork line and made a cultural and chronological interpretation of the complex based on ceramic and shell plate. The monument dates back to the late III – first half of the IV century and belongs to the Fominsky stage of the Kulaiskaya culture. The article contains previously unpublished photos of all the artifacts, except plain pottery. The introduction of the presented complex into scientific circulation improves the source base of ancient history studies of the forest-steppe Altai in the first half of the 1st millennium. The complex contains artifacts unpolluted with any culturally similar and chronologically close artifacts, which means that it can help identify the Fominsky stage and their cultural-markers. The matter is important not only for the archaeology of the forest-steppe Altai, but also for the neighboring territories with culturally and chronologically similar complexes in Novosibirsk and Kemerovo Regions.

Damage to Oil Tanks Caused by Severe Strong Ground Motion due to the 2018 Hokkaido, Japan Iburi-Tobu Earthquake (Mw6.6)

Damage and influences to oil tanks caused by severe strong ground motion due to a large earthquake (Mw6.6) that occurred in the district of Iburi-tobu, Hokkaido, Japan on September 6, 2018 are reported in this paper. In the vicinity of the seismic source region, two large-scale crude-oil storage bases are located. The neighboring two bases had in total 86 large oil storage tanks with a capacity of 115,000 m3. The oil storage bases were hit by strong ground motion with peak ground accelerations of 590 to 1,570 cm/s2 and with peak ground velocities of 50 to 80 cm/s. Shell plates of a small bunker A tank with a capacity of 306 m3 suffered diamond buckling and elephant-foot buckling. No large oil storage tanks lost their function of oil storage despite of the severe strong ground motion. However, most of them splashed oil from the gap between the floating roof and the shell plate, and many of them had damage to their pontoons, gauge poles, guide poles, rolling ladders, liquid-level meters, and shoulders of foundation. One of the 115,000-m3-in-capacity tanks was equipped with a displacement gauge system to measure uplift of the bottom of the shell plate from the shoulder of tank foundation. The system recorded a maximum uplift of 4.4 cm. This is the world’s first record of uplift of a large tank caused by a natural earthquake.