Dynamic evaluation of jack-up platform structure under wave, wind, earthquake and tsunami loads

Nowadays, the demand for using jack-up platforms to carry out a large percentage of deep-water oil and gas exploration is steadily increasing. The response of jack-up platforms to the severe dynamic loads that may be encountered during the structure life is not examined enough. Therefore, this study attempts to investigate the response of jack-up platforms performance under the effect of dynamic loads due to wave, wind, earthquake and tsunami forces using the finite element method for two models with the lowest and highest hull elevations. The jack-up platform is located in the Gulf of Mexico. Earthquake accelerations are applied to the model in high and moderate seismic levels. In addition, tsunami waves are applied to the platform in three different directions at 0°, 45° and 90°. This study utilised Airy's linear wave approach to assess the surface elevations and wave kinematics. The reference wind velocity is 10 knots at 10 m over the mean water level. Results indicate that the dynamic response of the structure is affected by the height of the platform and by the increase of the platform hull elevation. The combination of the El-Centro earthquake, dead and live loads provides the major impact on the platform at the lowest (70 m) and highest (85 m) hull elevations. The comparison of all result proves that the jack-up platform hull under high earthquake intensity and tsunami waves with 45° has experienced maximum deformation. Moreover, raising the deck will increase the response of the dynamic load and displacements but will negatively affect the platform

Seismic response analysis of linked twin tall buildings with structural coupling

Effect of structural links on seismic responses for a linked building system has been investigated in this paper by using finite element modeling technique. The linked building system in this study is represented by twin 40-story reinforced concrete frame-wall structures horizontally coupled by structural links. It is assumed that the two adjacent buildings were similar in this linked building system, so the two adjacent stories could be linked at the same height by an inter-building link. The linked building system is modeled as a rigid floor diaphragm for towers and as a beam for each link fixedly linked to the perimeter structural framework of the buildings. By employing earthquake time history excitation, the seismic responses of the twin towers were computed at different locations for the link. The responses of structures were evaluated and compared. The analysis outcomes indicated that the link could effectively change the structural responses of the linked building system. The structural responses have been decreased in some cases compared to the single tower, referring to the extra link stiffness as gathering the single tower to withstand seismic excitation. While the responses have been increased in other cases, attributing to the additional mass of link. Thus, in the design of seismic-resistant linked building systems, care must be taken. Particularly regarding properties of the link, specifically mass, stiffness, and location, as well as the link resistance with respect to the strength of the link and/or the structural elements composing the link to obviate undesired structural responses

Strut-and-tie model and its applications in reinforced concrete deep beams: A comprehensive review

Strut-and-tie model (STM), with its truss analogy, is yet a powerful tool for analyzing and designing complex prestressed and reinforced concrete structures. Which represents a simplistic method that predominantly provides conservative strength predictions. This article aims to provide a comprehensive review on the STM and its applications in reinforced concrete (RC) deep beams that are available in the open literature. Accordingly, a review of the STM technique is presented with a particular focus on the basic concept of STM, associated B- and D-regions, fundamentals of STM, historical development of STM, and its applications in RC deep beams. The review also covers a wide range of STM aspects including: strut strength and its effectiveness factor, node strength and its effectiveness factor, tie strength and minimum reinforcement, the effect of tie anchorage, and strain energy minimization. Hence, essential formulas and parameters of STM proposed by various design codes and researchers are reviewed and then summarized in comprehensive tables. Consequently, from the reviewed literature, several challenges are highlighted. Findings and recommendations that are necessary to be considered in future works are addressed. With the provided information, this review article serves as a useful reference for structural engineers and researchers who are familiar with STM, as well as who wish to enter this research field

SURFACE AREA EVALUATION OF MOSUL DAM LAKE USING SATELLITE IMAGERY TECHNIQUE

Due to water resources such as Tigris and Euphrates rivers, tributaries branches, marshlands and lakes, Iraq is considered, generally in the world and especially in Middle East, as one of the richest countries. These resources are already affected by the consequences of climate change increasingly. One of the most vital projects in Iraq is Mosul Dam (in the northern of Iraq), thus, Mosul Dam lake (MDL), in term of surface area, was observed and studied during the prior 35 years (1984-2019) to detect the effects of historical climate changes on surface area. Satellite data of Landsat has been used in this study based on route 170 and line 35. Best and cloud-free satellite images were downloaded from US Geological Survey. Eventually, ArcGIS technique was used to process and analyze the satellite images. The result displayed that average surface area and parameter of study area was about 242 km2 and 432 km consecutively. Relationship between surface area (A) and parameter (P) of study area has been generated and formulated. Furthermore, the correlation coefficient between surface area and parameter was about 71%. Coefficient of variance (COV) was found also to be about 0.271. Minimum surface area and parameter of study area were recorded in Sep. 2018 of about 171 km2 and 350 km respectively regardless the dates before the operating Mosul Dam, whereas, maximum A and P lake was found to be 337 km2 and 664 km in April,1994 respectively. The analysis showed that the exponential curve representing the best relationship between P and A

Late Age Dynamic Strength of High-Volume Fly Ash Concrete with Nano-Silica and Polypropylene Fibres

The dynamic behaviour of high-volume fly ash concrete with nano-silica (HVFANS) and polypropylene fibres at curing ages of 7 to 90 days was determined by using a split Hopkinson pressure bar (SHPB) machine. At each curing age, the concrete samples were laboratory tested at different temperatures conditions under strain rates reached up to 101.42 s−1. At room temperature, the results indicated that the dynamic compressive strength of plain concrete (PC) was slightly higher than HVFANS concrete at early curing ages of 7 and 28 days, however, a considerable improvement in the strength of HVFANS concrete was noted at a curing age of 90 days and recorded greater values than PC owing to the increase of fly ash reactivity. At elevated temperatures, the HVFANS concrete revealed a superior behaviour than PC even at early ages in terms of dynamic compressive strength, critical strain, damage and toughness due to increase of nano-silica (NS) activity during the heating process. Furthermore, equations were suggested to estimate the dynamic increase factor (DIF) of both concretes under the investigated factors