A Method for Predicting Six Degrees-of-Freedom Ultimate Limit State of Subsea Mudmats

2014 ◽  
Author(s):  
Xiaowei Feng ◽  
Susan Gourvenec
Keyword(s):  
Bearing Capacity ◽  
Degrees Of Freedom ◽  
Limit State ◽  
Accurate Determination ◽  
Ultimate Limit State ◽  
Foundation Soil ◽  
Simplified Approach ◽  
Six Degrees Of Freedom ◽  
Offshore Industry ◽  
Ultimate Limit

Rectangular mudmat foundations are extensively deployed in deep waters to support subsea infrastructure leading to renewed interest in optimizing the design of offshore shallow foundations. Offshore industry guidelines (e.g. API RP2GEO and ISO 19901-4) are based on classical bearing capacity theory of a plane strain strip foundation resting on the surface of a uniform Tresca material. More realistic conditions are accounted for through a range of superposed empirical modification factors and the effective width principle. In practice, subsea foundations experience complex loading in six degrees-of-freedom (vertical load, biaxial horizontal load, biaxial moment and torsion), due to expansion and contraction of connected pipelines and jumpers; they may be able to mobilize transient tensile capacity; and they are typically three-dimensional in plan, shallowly embedded and founded on soft, normally consolidated, soils with linearly increasing strength with depth. Accurate determination of the ultimate limit state of subsea mudmats is best achieved by considering the relevant foundation, soil and loading boundary conditions explicitly. In this paper, a simplified approach for predicting the ultimate limit state of mudmat foundations under six degrees-of-freedom, based on failure envelopes, obtained from extensive finite element analyses, is compared with the traditional bearing capacity methods as recommended in industry guidelines.

End-Plate Connections in Bi-Axial Bending - Measurements

2016 ◽  
Vol 710 ◽  
pp. 275-280
Author(s):  
Jari Mäkinen ◽  
Keijo Fränti ◽  
Matti Korhonen ◽  
Joshua Fillion ◽  
Markku Heinisuo
Keyword(s):  
Bearing Capacity ◽  
Cross Section ◽  
Limit State ◽  
Ultimate Limit State ◽  
Load Bearing Capacity ◽  
End Plate ◽  
Residual Capacity ◽  
Plate Connections ◽  
Ultimate Limit ◽  
Is Strain

In this paper we consider the measurements of bolted end-plate connections of tubular beams with cold-formed hollow rectangular aluminium sections. The motivation for these measurements originates from the fact that the aluminium standard (EN 1999-1-1) [1] does not cover the design of this very frequently used type of connection, where the bolts are located outside the edge-lines of the cross-section, i.e. corner bolts. Many tests and studies regarding this area have been conducted, but this paper brings value to the case where bi-axial bending is applied. The measurements have been carried out and the detailed results shall be shown. In this paper, we will focus on the six measurements where the tubular beams were bent uniaxially and biaxially to these limit points. The tests were stopped when the ultimate limit state was reached. In this case the connection never actually broke, but effectively the joint had lost its load bearing capacity. Some residual capacity still remained, but the displacements were too great resulting in a totally different behavior of the connection. The behavior of this connection is highly non-linear, since aluminium (AW 5754) as a material is strain hardening and the mechanism in the connection changes as the displacements increase.

Design Issues about the Bar Lay-Out at the Dapped Ends of Simply-Supported One-Way R/C Slabs

2016 ◽  
Vol 711 ◽  
pp. 706-713
Author(s):  
Pietro G. Gambarova ◽  
Francesco Lo Monte
Keyword(s):  
Bearing Capacity ◽  
Limit State ◽  
Ultimate Limit State ◽  
Main Body ◽  
Concentrated Load ◽  
Bending Tests ◽  
Simply Supported ◽  
Extra Effort ◽  
Dapped Ends ◽  
Ultimate Limit

Directly-or indirectly-supported R/C slabs are frequently used in the covers of small-to-medium underground facilities, where the service loads are often rather limited, but very severe loads cannot be ruled out in accidental situations.To have fresh information on the structural performance and cracking of R/C slabs simply supported along their short sides via corbels (dapped ends), four rectangular slabs subjected to transversely distributed or concentrated loads have been recently tested in Milan (b x L = 1.30 x 2.20 m; simply-supported span = 2.10 m; thickness = 15 cm). The load was applied either at mid-span (in the bending tests, not presented in this paper), or at 1/10 of the span (in the shear tests).Two bar arrangements were investigated with straight or bent-up bars in the main body, and straight bars or hooks in the corbels.In the D zones of the slabs tested in shear, the concentrated load induces a rather complex 3-D crack pattern, with a limited reduction in the bearing capacity, compared with the cross-wise distributed load.Rather simple strut-and-tie models applied to the slabs with bent-up bars and hooks, and the equations provided by European and North-American codes for the beams devoid of transverse reinforcement are shown to yield realistic predictions for the bearing capacity at the ultimate limit state. In the former case, however, modelling the bond along the tension reinforcement of the corbel requires some care, because of bond local and global effects. Last but not least, refining bar layout confirms – once more – that slab performance can be markedly improved with little extra effort.

Effect of the Extension of Basement Floor and the Importance of a Proper Design of Interaction between the Foundation and the Subsoil

2014 ◽  
Vol 969 ◽  
pp. 148-154 ◽  
Author(s):  
Ivana Olekšáková ◽  
Oľga Ivánková
Keyword(s):  
Limit State ◽  
Difficult Problem ◽  
Ultimate Limit State ◽  
Structural System ◽  
Foundation Soil ◽  
Static And Dynamic Analysis ◽  
Basement Floor ◽  
Structural Engineer ◽  
Proper Design ◽  
Ultimate Limit

Proper design of structural system is the most important task for a structural engineer. Correct assessment of interaction of the building with the subsoil and its significant impact not only on the foundation structure but also on the entire building is very often forgotten. For design of all parts and for the whole structure the ultimate limit state (ULS) and serviceability limit state (SLS) are crucial. Static and dynamic analysis of the building has presently became an inevitable part of the design of difficult structure. In this paper both the changes, which are visible by the variations of the structural system, and the way of the foundation and necessity of knowing the properties of the foundation soil have been presented. Proper design of the interaction between the building and the subsoil is very difficult problem and therefore it is very important for experts to cooperate, mainly for structural engineer and geologist.

OPTIMASI BIAYA PONDASI SETEMPAT DENGAN METODE METAHEURISTIK

2020 ◽  
Vol 7 (2) ◽  
pp. 47-52
Author(s):  
Vania Regina Husada ◽  
Ferdian Nathanael ◽  
Doddy Prayogo ◽  
Yudas Tadeus Teddy Susanto
Keyword(s):  
Particle Swarm Optimization ◽  
Bearing Capacity ◽  
Limit State ◽  
Ultimate Limit State ◽  
Swarm Optimization ◽  
Symbiotic Organisms Search ◽  
Serviceability Limit State ◽  
Capacity Theory ◽  
Symbiotic Organisms ◽  
Ultimate Limit

Pondasi adalah bagian dari struktur bangunan yang berfungsi meneruskan beban struktur atas ke lapisan tanah dengan aman. Sementara pondasi dangkal digunakan apabila lapisan tanah keras terletak dekat dengan permukaan tanah. Untuk mendapatkan hasil desain pondasi dangkal yang optimal, terdapat tiga kriteria penting yang harus diperhatikan yaitu Ultimate Limit State (ULS), Serviceability Limit State (SLS), dan ekonomis. Sehingga, penggunaan metode optimasi yang baik akan membantu menghasilkan dimensi pondasi yang optimal dan ekonomis namun tetap memenuhi syarat aman. Penelitian-penelitian sebelumnya mengindikasikan bahwa metode metaheuristik dapat digunakan sebagai alternatif yang mampu menyelesaikan permasalahan optimasi yang ada. Oleh karena itu, penelitian ini menggunakan metode metaheuristik Particle Swarm Optimization (PSO) dan Symbiotic Organisms Search (SOS) untuk menyelesaikan permasalahan optimasi pondasi dangkal. Pada penelitian ini, optimasi pondasi dangkal dilakukan terhadap pondasi setempat untuk studi kasus bangunan dua lantai. PSO dan SOS bekerja untuk menemukan solusi dimensi pondasi setempat yang diharapkan dapat memiliki biaya konstruksi terendah dan dibatasi oleh constraint dari SNI 8460:2017, SNI 2847:2013, dan bearing capacity theory. Hasil penelitian menunjukkan bahwa metode metaheuristik mampu menemukan dimensi pondasi dangkal yang optimal untuk masing-masing studi kasus. Selain itu, dapat dilihat apabila algoritma SOS memiliki performa yang lebih baik dari PSO.

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