Flexible Pipes and Limit-States Design

The application of concrete filled steel tubes (CFSTs) as composite members has widely been used around the world and is becoming popular day by day for structural application especially in earthquake regions. This paper indicates that an experimental study was conducted to comprehend the behaviour of T-stub end plates connected to concrete filled thin-walled steel tube (CFTST) with different types of bolts and are subjected to pullout load. The bolts used are normal type bolt M20 grade 8.8 and Lindapter Hollo-bolt HB16 and HB20. A series of 10 mm thick T-stub end plates were fastened to 2 mm CFTST of 200 mm x 200 mm in cross-section. All of the specimens were subjected to monotonic pull-out load until failure. Based on test results, the Lidapter Hollo-bolts showed better performance compare to normal bolts. The highest ultimate limit load for T-stub end plate fasten with Lindapter Hollo-bolt is four times higher than with normal bolt although all end plates show similar behaviour and failure mode patterns. It can be concluded that T-stub end plate with Lindapter Hollo-bolt shows a better performance in the service limit and ultimate limit states according to the regulations in the design codes.

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Modular Bridge Expansion Joints for Lacey V. Murrow Floating Bridge

Transportation Research Record Journal of the Transportation Research Board ◽

10.3141/1594-18 ◽

1997 ◽

Vol 1594 (1) ◽

pp. 163-171 ◽

Cited By ~ 1

Author(s):

John A. Van Lund ◽

Mark R. Kaczinski ◽

Robert J. Dexter

Keyword(s):

Fatigue Strength ◽

Fatigue Cracking ◽

Field Measurements ◽

The United States ◽

Limit States ◽

Expansion Joints ◽

Lake Washington ◽

Floating Bridge ◽

Modular Bridge Expansion Joints ◽

Washington State Department

The Lacey V. Murrow Bridge (LVM Bridge) is a 2013-m-long floating bridge on Interstate 90 across Lake Washington in Seattle, Washington. Single-support-bar, swivel-joist modular bridge expansion joint systems are located at each end of the bridge between the shore approach spans and the floating pontoons. These joints were designed for 960 mm of longitudinal movement as well as horizontal and vertical rotations caused by wind, wave, temperature, and changes in lake level elevation. A similar joint in an adjacent floating bridge had experienced premature fatigue cracking at welded attachment details because of low fatigue strength. For the LVM Bridge the joint components were fatigue tested and designed by using fatigue limit-states loads, resulting in welded attachment details with improved fatigue strength. In addition, a stiffer center beam and reduced center-beam span lengths produced lower fatigue stress ranges. Joint movements and rotations, fatigue design methodology, results of dynamic analyses, field measurements of the dynamic response, and construction details are described. The total cost of the LVM joints was 1 percent of the final bridge cost. The Washington State Department of Transportation required a 5-year guarantee for the LVM joints. These are the largest modular bridge expansion joints in the United States to be tested and designed for fatigue.

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STRUCTURAL RELIABILITY ANALYSIS BASED ON P-BOXES

Building and reconstruction ◽

10.33979/2073-7416-2020-92-6-51-58 ◽

2020 ◽

Vol 92 (6) ◽

pp. 51-58

Author(s):

S.A. SOLOVYEV ◽

Keyword(s):

Probability Distribution ◽

Reliability Analysis ◽

Structural Reliability ◽

Epistemic Uncertainty ◽

Random Variable ◽

Strength Criterion ◽

Structural Elements ◽

Structural Element ◽

Limit States ◽

Distribution Shape

The article describes a method for reliability (probability of non-failure) analysis of structural elements based on p-boxes. An algorithm for constructing two p-blocks is shown. First p-box is used in the absence of information about the probability distribution shape of a random variable. Second p-box is used for a certain probability distribution function but with inaccurate (interval) function parameters. The algorithm for reliability analysis is presented on a numerical example of the reliability analysis for a flexural wooden beam by wood strength criterion. The result of the reliability analysis is an interval of the non-failure probability boundaries. Recommendations are given for narrowing the reliability boundaries which can reduce epistemic uncertainty. On the basis of the proposed approach, particular methods for reliability analysis for any structural elements can be developed. Design equations are given for a comprehensive assessment of the structural element reliability as a system taking into account all the criteria of limit states.

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Artificial mixing to reduce growth of the blue-green alga Microcystis in Lake Nieuwe Meer, Amsterdam: an evaluation of 7 years of experience

Water Science & Technology Water Supply ◽

10.2166/ws.2001.0003 ◽

2001 ◽

Vol 1 (1) ◽

pp. 17-23 ◽

Cited By ~ 14

Author(s):

E. Jungo ◽

Petra M. Visser ◽

Jasper Stroom ◽

Luuc R. Mur

Keyword(s):

Water Body ◽

Bubble Plume ◽

Annual Fluctuation ◽

Algae Biomass ◽

Mechanical Parts ◽

Living Space ◽

Artificial Mixing ◽

Flexible Pipes ◽

Nitrogen Concentrations ◽

Extensive Growth

The problem of Lake Nieuwe Meer (area = 1.3 km2, max. depth 30 m, Ptot = 500 mg/m3) was extensive growth of Microcystis with disturbing scum forming. Since 1993 the lake has been artificially mixed in summer by a bubble plume installation. The result is quite successful since the mass of Microcystis is up to 20 times lower than in the years before mixing and no scum is present any more. The study in Lake Nieuwe Meer showed a shift from cyanobacterial dominance (mainly Microcystis) to flagellates, green-algae and diatoms when artificial mixing was applied. Total phosphorus and nitrogen concentrations did not change as a result of mixing and had apparently no effect on the shift in the phytoplankton composition. The chlorophyll-a concentration was much lower in the mixed lake as a result of dilution. The total algae biomass decreased. The transparency did not improve. The total heat energy of the lake is slightly higher than before mixing but still remains in the range of annual fluctuation. The temperature on the surface is approximately 2°C lower. In the whole water-body oxygen was always higher than 5 mg/l. Living space for fish is therefore wider. The installation in Lake Nieuwe Meer consists of flexible pipes near the sediment, built in a way to prevent sediment erosion and transport into the water. There are no constructions in the water-body. All mechanical parts are on land. The layout of the installation is shown in Fig. 1. Installed compressor energy is 85 kW. This is equivalent to an upper middle-class motor-car. The design was made specifically for this problem. It is based on the physical data of the algae and the plant. It would be beneficial to use this 7 year's experience for further applications e.g. elimination of toxic algae in drinking-water reservoirs.

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Floating-bending tensile-integrity structures

Curved and Layered Structures ◽

10.1515/cls-2021-0008 ◽

2021 ◽

Vol 8 (1) ◽

pp. 89-95

Author(s):

Micol Palmieri ◽

Ilaria Giannetti ◽

Andrea Micheletti

Keyword(s):

Structural Design ◽

Membrane Systems ◽

Limit States ◽

Form Finding ◽

Supported Membrane ◽

Tensegrity Systems ◽

Matlab Implementation ◽

Diamond Type ◽

Conceptual Work

Abstract This is a conceptual work about the form-finding of a hybrid tensegrity structure. The structure was obtained from the combination of arch-supported membrane systems and diamond-type tensegrity systems. By combining these two types of structures, the resulting system features the “tensile-integrity” property of cables and membrane together with what we call “floating-bending” of the arches, a term which is intended to recall the words “floating-compression” introduced by Kenneth Snelson, the father of tensegrities. Two approaches in the form-finding calculations were followed, the Matlab implementation of a simple model comprising standard constant-stress membrane/cable elements together with the so-called stick-and-spring elements for the arches, and the analysis with the commercial software WinTess, used in conjunction with Rhino and Grasshopper. The case study of a T3 floating-bending tensile-integrity structure was explored, a structure that features a much larger enclosed volume in comparison to conventional tensegrity prisms. The structural design of an outdoor pavilion of 6 m in height was carried out considering ultimate and service limit states. This study shows that floating-bending structures are feasible, opening the way to the introduction of suitable analysis and optimization procedures for this type of structures.

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Mechanical behavior of metallic strip flexible pipes during reeling operation

Marine Structures ◽

10.1016/j.marstruc.2021.102942 ◽

2021 ◽

Vol 77 ◽

pp. 102942

Author(s):

Yuxin Xu ◽

Pan Fang ◽

Yong Bai

Keyword(s):

Mechanical Behavior ◽

Flexible Pipes ◽

Metallic Strip

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Displacement-Based Seismic Assessment of the Likelihood of Failure of Reinforced Concrete Wall Buildings

Buildings ◽

10.3390/buildings11070295 ◽

2021 ◽

Vol 11 (7) ◽

pp. 295

Author(s):

Amirhossein Orumiyehei ◽

Timothy J. Sullivan

Keyword(s):

Reinforced Concrete ◽

Seismic Risk ◽

Concrete Wall ◽

Limit States ◽

Simplified Approach ◽

Performance Based Assessment ◽

Assessment Approach ◽

Reinforced Concrete Wall ◽

Displacement Based ◽

Assessment Procedures

To strengthen the resilience of our built environment, a good understanding of seismic risk is required. Probabilistic performance-based assessment is able to rigorously compute seismic risk and the advent of numerical computer-based analyses has helped with this. However, it is still a challenging process and as such, this study presents a simplified probabilistic displacement-based assessment approach for reinforced concrete wall buildings. The proposed approach is trialed by applying the methodology to 4-, 8-, and 12-story case study buildings, and results are compared with those obtained via multi-stripe analyses, with allowance for uncertainty in demand and capacity, including some allowance for modeling uncertainty. The results indicate that the proposed approach enables practitioners to practically estimate the median intensity associated with exceeding a given mechanism and the annual probability of exceeding assessment limit states. Further research to extend the simplified approach to other structural systems is recommended. Moreover, the research highlights the need for more information on the uncertainty in our strength and deformation estimates, to improve the accuracy of risk assessment procedures.

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