鋼管杭の簡便杭頭接合方法に対する構造実験

This paper proposes a method to calculate the maximum allowable bending moment on pipe flange connections for leak tightness design of piping systems in process plants. The method evaluates the gasket stress reduction due to the bending moment as well as internal pressure based on the load factor of the bolted-gasketed pipe flange connection and the equivalent axial force. It determines the critical load combination of pressure and bending moment causing leakage. The calculated maximum allowable bending moment has shown fairly good agreement with experimental results with reasonable conservativeness. The paper also shows the advantage of the proposed method against the conventional methods such as the equivalent pressure method, NC-3658.3 method, B31.8 method, and so on.

This paper describes the further improvement of the simplified method of progressive collapse analysis of a ship's hull under longitudinal bending proposed by the authors. Here, the method of analysis of flexural behaviour of stiffener elements was extended to deal with coupled flexural-torsional behaviour of angle bar stiffeners welded to continuous plating.A series of elastoplastic large deflection analysis was performed and the rationality of the proposed method was examined.With the improved computer code 'HULLST', two alternative analyses were performed on existing bulk carrier including and neglecting tripping of stiffener elements. It was found that the ultimate strength of stiffener elements decreases when stiffener tripping takes place, which results in reduction of ultimate bending moment of the cross-section. The load carrying capacity of stiffener elements in the post-ultimate strength range was more decreased and so that of the cross-section. The allowable bending moment according to the Lloyd's Register of Shipping was calculated and the reserve strength above it until the initial local collapse was 22.4% of the allowable bending moment. Interaction diagram for longitudinal hull strength under bi-axial bending is also presented.Progressive collapse analysis was performed also on a large scale frigate model tested by Dow, and the applicability of the present method was demonstrated.

There are many types of flange and clamp connectors in use and described by different standards. Most of them are based on the linear elastic methodology and allowable stress concept (ASME, API flanges). More modern designs (ISO 27509 and NORSOK L-005 Compact Flanges, NORSOK U-001 subsea flanges) are based on elastic plastic principles and plastic collapse capacities. For all of them defining the tensile structural and functional limits is relatively transparent and seamless process. Often the external allowable Bending Moment load at rated Pressure is one of the most critical characteristics for subsea use and High-Pressure connections. To predict capacity and allowable Bending Moment is more complicated especially for modern flange types. In this paper author will focus and explaining already existing design methods with relation to the FEA assessment and modern connections structural and functional capability. The topic will be discussed based on the Compact Flange (ISO 27509 and NORSOK L-005) connection example and in related structural FEA long term functionality check based on DNVGL-RP-F112 recommendations (Hydrogen Induced Stress Cracking for subsea Duplex and Super Duplex material). In the presented example the focus will be on the flange itself, but the attached pipe also be included in the evaluation. The topic discussed in the paper and the conclusions are included in the FEA recommendation in the newest national NORSOK L-005 flange design code release.

Pile foundations are a widely used and accepted approach to transferring superstructure load to a deeper and stronger stratum. This work has been focused on the assessment of the effects of different parameters associated with piles, such as pile diameter, pile length, grade of concrete, and pile head condition (i.e., free or fixed) on the lateral load capacity. To evaluate the lateral load capacity considering the aforementioned parameters, ‘IS Code’ and ‘Matlock and Reese’ methodologies have been utilized. Soil exploration data has been collected from ten different boreholes near the railway bridge at Bettiah site, Bihar. The results of lateral pile load at different boreholes show that the lateral load capacity of the pile significantly increases with the increase of pile diameters and grades of concrete. The lateral load capacity of the pile was increased approximately by 13%, from both the IS Code and the Matlock and Reese methods, when the grade of concrete was increased from M25 to M40. It was also found that the condition of the pile head also plays a major role in lateral load capacity. The lateral load capacity of the pile, obtained from the IS code method under fixed head conditions, was found to be higher as compared to the free head condition. It has also been observed that the lower values of safe bearing capacity for fixed heads and lower values for the free head condition were obtained by the IS Code as compared to the Matlock and Reese method.

In-situ horizontal cyclic loading tests on composite foundation composed of soilbags and piles

In the present work, the behaviour of a single pile submitted to axial loading is analyzed. Namely, we examine the static stiffness coefficient at the head of a flexible pile, vertically embedded in a homogeneous or multilayer soil of random geometry and mechanical properties. To solve the problem, an analytical closed form solution is developed, based on Winkler’s theory. The model is used in combination with suitable shape functions, which describe reliably the vertical movement of the pile with depth. By choosing the appropriate shape functions along with “t–z” and “q–z” curves and following an iterative process, a relatively accurate estimation of the vertical displacement at the head of the pile can be achieved. Unlike traditional numerical solutions, the proposed method does not require discretization of the pile into finite elements (and afterwards resolution of a system of linear equations of high order) but only discretization in sections aiming integration with depth.

The purpose of this paper is to investigate experimentally the local buckling strength and interaction strength between local and overall buckling of closed polygonal section steel columns. A total of 23 specimens was tested to failure under axial compression loading. Seventeen specimens were stub columns with regular rectangular, pentagonal, hexagonal, heptagonal, and octagonal sections. The others were medium‐length columns with regular rectangular, hexagonal, and octagonal sections. An empirical formula based on the compression tests is presented to predict local buckling strength and interaction strength between local and overall buckling strengths of closed polygonal steel columns. Edge strain at the maximum stress‐and‐strain energy is an important standard to estimate the load‐carrying capacity of a member same as the maximum stress. A comparison of edge strain and strain energy with equivalent width‐thickness ratio is included. They show a similar tendency and decrease with the increase of equivalent width‐thickness ratio. Also, they decrease with the increase with the equivalent slenderness ratio.

Local and post-local buckling of fabricated high-strength steel and composite columns

Winkler model for pile seismic analysis considering end constraints effects

Experimental investigation on bearing capacity of rock-socketed bored piles in silty clay stratum in beach areas

In the previous papers, the steel pile ultimate strength and plastic deformation capacity for local buckling is estimated with radius thickness ratio and shear span ratio. For real structures, concrete is filled into the pile top of steel piles to fix the connection between a steel pile and a reinforced concrete footing beam in. It is considered that the local buckling strength of steel piles with concrete at the pile top is larger than that of steel piles to prevent local buckling issued from filled concrete at the pile head. On the other hand, at the pile top filled with concrete, bending stress of steel pipes is not enough transmitted to a concrete member which slips on the steel pipe. Therefore, slip stoppers are attached to the steel pile top. The stress transfer mechanism between a steel pipe with slip stoppers and a concrete member has not been clarified In this paper, cyclic load tests of steel piles filled with concrete at the pile top with different axial force ratio are performed. The local buckling behavior of steel piles at pile top is elucidated and ultimate strength, deformation capacity and hysteretic energy absorption is evaluated.

The 3D finite element simulations are carried out to study the impact of different pile head connection conditions, i.e., rigid and hinged connection on the response of piled rafts in sand subjected to pseudo-static horizontal loading. The time-acceleration histories of Assam (2014), Bhuj (2001), Sikkim (2011) and Uttarkashi (1991) earthquakes are considered to calculate the horizontal pseudo-static loads. Analyses results confirm that pile head connection rigidity greatly influences the behavior of piled raft in many aspects. The horizontal stiffness of piled raft is found to decrease as the rigid pile head connection changes to hinged one. Piles in a piled raft foundation is found to carry about 52–75% of the pseudo-static horizontal load for rigid connection and 32–48% for hinged connection. The horizontal deflection of pile is found maximum at the pile head and becomes negligible along the depth of pile for both cases. For rigidly connected piles, the maximum bending moment occurs at the pile head, whereas piles with hinged connection show zero bending moment at top and maximum value at a certain depth from pile head.

The applieabfity of the Ras Tanajib pile capacity method to piles driven to penetrations greater than 30 m in the very dense sands of the Safaniya Field of the Arabian Gulf is investigated. Comparisons of observed and predicted blow counts, and measured and computed soil resistances to driving are presented. Blow counts are predicted using procedures recommended by Stevens, Wiltsie, and Turton (1982). The measured soil resistance to driving is the Case- Goble bearing capacity computed using a damping coefficient of 0.20. The computed soil resistance to driving is the lower and upper bound values computed for a plugged pile. CAPWAP analyses are performed at final penetration to confirm pile capacities computed using the Ras Tanajib method. Introduction We platforms were recently installed as part of the GOSP- 4 complex in the Safaniya Field of the Arabian Gulf. Design penetrations were selected from pile capacities computed using the Ras Tanajib method, and ranged from 48 to 69 m for the six-pile Accommodation Platform, 59 to 77 m for the eight-pile Tie-In Platform, and 35 to 84 m for the twelve-pile Production Platform. The Flare Bridge Support and Flare Platforms were lightly loaded structures. Previously, the maximum driven pile penetrations in the Safaniya Field were only 28 and 30 m for 36- and 42-in. (0.91- and 1.07-m) -diameter piles, respectively. Pile refusal has occurred at shallow penetrations due to rock layers and cemented zones. Since 1979, of the 41 piles that have refused, 19 were accepted based on the results of pile monitoring, 10 were accepted with a grout plug, 6 were redriven after drilling a pilot hole, one was redriven after removing the soil plug and 5 drilled and grouted insert piles were installed. The average penetration for the piles driven to refusal is 19 m The Ras Tmusjib Method Piles driven to shallow penetrations in the Safaniya Field had soil resistances to driving that were as much as 10 times greater than the computed static pile capacity. Because discrepancies of this magnitude were observed, a total of 26 pullout tests were performed in 1982 at eight offshore siteson 20- to 30-in. (0.51- to 0.76-m) -diameter open-ended pipe piles driven to penetrations of 11 to 22 m. Tensile capacities were 2.5 to 6 times greater than the static pile capacity computed using the API method. Wiltsie, Stevens, and Vines (1984) provide additional information. Load tests were performed in 1983 on two 18-m long, 24-ii. (0.61- m) -diameter open-ended pipe piles driven in the very dense sands at Ras Tanajib, A new procedure was developed to compute pile capacity in very dense sands. Helfrich, Wiltsie, COL and A1-Shafei (1985) and A1-Shafei, COL and Helfrich (1994) describe these load tests in more detail. The engineering design parameters adopted by Saudi Aramco for designing piles driven into medium-dense to very dense sand are presented on Table 1. The very dense, over consolidated sand and silty sand typically have cone sleeve resistances greater than 400 kpa.

PHC pile is the most widely used pile in mainland China and Taiwan, and the joint between pile head and pile cap is a problem that cannot be solved effectively in foundation engineering. Pullout resistance force on the pile-head core of improved PHC pile is tested in full scale, and the test result is compared with theoretical calculation and conventional estimation of PHC pile. The test pile of PHC 600 B 100–10 is a 600 mm diameter, 10 m long pile with pile head of 2 m in length. There are 6 layers in 2 by 2 horizontal D19 rebars placed within inner portion of the pile head. Test is followed with ASTM-D3689M. The result shows that the pullout loading goes up to 175 tons, and the theoretical value of the pullout resistance force calculated from the pile-head core is 371 tons, which is 7.5 times and 6.2 times higher of the pullout resistance force of the 2 m long pile-head core compared to the conventional PHC pile proposed by two literature studies respectively. The result also shows that the improved PHC pile can be more effectively connected with the pile cap.

A simple method for calculating the shakedown behavior of the hull girder of a ship or marine vehicle is presented herein. The requirements for shakedown demand allowable bending moments which are generally smaller than those necessary to " break the back of a ship."