Gravity Anchor Research Articles

A Novel Restraining System for a Powerless Advancing Ship: A Combined Theoretical and Experimental Investigation

A novel flexible restraining system is proposed to protect a waterway crossing road, a railway, or a combined bridge when a powerless advancing ship approaches such a structure. Direct collision with principal bridge supports is not addressed under the assumption that the restraining system is located some distance upstream of the non-navigational bridge, assuming the ship cannot engage propulsive system in reverse to reduce the speed of ship advance. Ship-independent seabed-located gravity anchors are to be ultimately dragged to dissipate ship kinetic energy. A mathematical model of the proposed method of restraint is developed and the resulting movements of ship and anchors are predicted for two distinct ship forms. These ships' responses are investigated for initial ship velocity, angle of approach, and point of contact with restraining cable of different investigated spans in the presence and absence of a current. The theoretical simulations agree reasonably well with the related model measurements given the existence of ship sway and yaw motions are not addressed. The results are sufficient to demonstrate the applicability of the proposed system. Predictions and observations suggest that the smaller the restraining cable span and the closer the ship is located to the anchors (initially vertically below the ends of the restraining cable), the more effective is the retraining process.

Crossing Lake Washington

The world's longest floating bridge, SR 520 Evergreen Point Floating Bridge, was opened by the Washington State Department of Transportation in April 2016. The new crossing carries State Route 520 across Lake Washington, near Seattle, as did the structure it replaces. The bridge's transition spans are pinned to the fixed, land-based structures by a built-up steel weldment, and in order to accommodate the bridge's motions, spherical bearings with identical radii form a sphere that acts like a trailer hitch. Immense gravity anchors are used in places where soil conditions permit on the underwater slopes, and due to their size, required special logistical considerations.

Dynamics of anchor last deployment of submersible buoy system

Submersible buoy systems are widely used for oceanographic research, ocean engineering and coastal defense. Severe sea environment has obvious effects on the dynamics of submersible buoy systems. Huge tension can occur and may cause the snap of cables, especially during the deployment period. This paper studies the deployment dynamics of submersible buoy systems with numerical and experimental methods. By applying the lumped mass approach, a three-dimensional multi-body model of submersible buoy system is developed considering the hydrodynamic force, tension force and impact force between components of submersible buoy system and seabed. Numerical integration method is used to solve the differential equations. The simulation output includes tension force, trajectory, profile and dropping location and impact force of submersible buoys. In addition, the deployment experiment of a simplified submersible buoy model was carried out. The profile and different nodes’ velocities of the submersible buoy are obtained. By comparing the results of the two methods, it is found that the numerical model well simulates the actual process and conditions of the experiment. The simulation results agree well with the results of the experiment such as gravity anchor’s location and velocities of different nodes of the submersible buoy. The study results will help to understand the conditions of submersible buoy’s deployment, operation and recovery, and can be used to guide the design and optimization of the system.

Design and Application of Rock Bolt Foundation in Mountain Cable Crane

Restricted by the construction environment, the cable crane is an effective means to resolve the transportation of materials and component in the mountainous area. Compared with traditional gravity anchor base, cable crane fixed on the rock bolt foundation can take advantage of the bearing capacity of bedrock, and the construction method is simple and of good economic benefit. With the effect of the construction methods, design theory of geological conditions, and other factors, however, force calculation is much complicated. By analyzing the failure modes of rock bolt foundation, anchor foundation bearing capacity factors and multi anchorage effect on anchoring force, we studied the design process of rock bolt foundation, geotechnical strength parameters and the safety coefficient of reference value. Further, a construction way is proposed to improve the basic bearing capacity of rock bolt. Combing with engineering examples, we also demonstrated the security and reliability of the design method .

Numerical Simulation for the Motion of the Flexible Floating Collision-Prevention System

The flexible floating collision-prevention system (FFSCS) is a valuable floating engineering structure that can be used to prevent the uncontrolled ships to collide with the non-navigational bridge of a large sea-crossing bridge. The system is composed of buoys, block chains, mooring chains and gravity anchors. The deformation of the system under the acting of an uncontrolled ship as well as the movement distance of the gravity anchors are important factors that should be considered by the system designers. Based on the analysis of the relationship between the forces and the deformation of each part of the system, the approximately static equations are solved by a new numerical iterative calculation method. The position changes of the buoys, the movements of the anchors and the history of the inner forces of the block chains when a ship collides with the FFSCS are obtained by iterative calculation. The good agreement between the numerical value and the results of the model test indicate that the small balance method is a validation on the motion response simulation of the FFSCS under the acting of the uncontrolled ship. The results validate that FFSCS can stop the uncontrolled ship before it arrives at the place of the bridge.

Temperature Field Calculation of Mass Concrete Anchor

Gravity anchor is one of essential forced components of steady suspension bridge. The paper takes the example of the finite element numerical simulation of steady suspension bridge gravity anchor, main contents include: First, performance parameters of concrete and hydration heat of cement is collected, the one-fourth block of anchor model is established by large-scale general finite element software ANSYS. The process of establishing finite element analysis model includes the input of the model parameters, the boundary conditions set of finite element model, and the mesh of finite element analysis model. Then, the numerical simulation computation to temperature field of gravity anchor is carried by finite element software ANSYS. Finally, from the temperature field distribution curves, studying the temperature distribution rule of concrete pouring and drawing some conclusions.

부유식 파력발전장치용 계류시스템의 초기설계

Preliminary design of a mooring system for a floating wave energy converter(WEC) is performed. A mooring line is designed to consist of two parts; the one is a chain in heavy weight laid on the seabed and linked to an anchor on the seabed and the other is a light weight chain suspended at a floater. A high weight chain laid on the seabed can contribute to mitigate dynamic energy propagated from top oscillation and decrease anchor weight and volume. Through a low weight chain suspended between a floater and seabed the WEC`s function to produce energy from wave can be affected in minimum by the motion of a chain. The static and dynamic analyses for the designed mooring system were carried out to evaluate WEC system`s safety. The present study shows that the designed gravity anchor moves horizontally due to the tension exerted on the anchor in the severe ocean environmental condition. The present mooring system should be redesigned to satisfy the safety requirements. The present study will be useful to predict the safety of the mooring system under ocean environment.

The Adventure Of Covering A Swimming-pool WithAn X-frame Structure

Deploy able grids have generated a lot of literature and theoretical proposals but till the moment only a few realizations. This is the reason why it is important the process that has concluded by erecting a building deployed from two parcels of 33 c.m. including structure, fabric cover and complementary elements till a total volume enclosed of 11.000 c.m. in the time that takes to hang these two parcels from a crane, deploy them by gravity load and anchor the lower points to the foundations and supports. We describe the basis of the design as well as details of construction, process of building and final appearance of the whole.

Earthquake Response of Tension Leg Platform with Gravity Anchor

The Tension Leg Platform (TLP) is a new type of oceanic structure developed for exploiting deep water petroleum. Generally the TLP is moored to the sea-bed foundation by vertical taut tethers. When the TLP is compared with a conventional jacket-type or jack-up-type platform, it has an advantage of low cost when constructing in a deep waters.Since the TLP has been said to be an aseismatic structure, an earthquake load has not been considered as an external force to tethers in design. It is true that the horizontal component of earthquake can be ignored, because the bending rigidity of the tether is nearly zero. However, the vertical seismic force is an important factor to be considered in design, because it is added to pretention of the tether directly. The authors have made theoretical and experimental investigations on the earthquake response of the TLP for years.The purpose of this report is to set up an analysis model for determining the response of TLP at it's connection with the gravity anchor when the TLP is subjected to vertical seismic excitation.As a result of a calculation, the weight of the gravity anchor in water must be more than about two and half times as much as the pretension of tethers.

Compressional wave velocity structure of the upper 350 km under the Eastern Snake River Plain near Rexburg, Idaho

Relative travel time residuals for teleseismic P and PKIKP are used to determine the compressional velocity structure under the eastern Snake River Plain at Rexburg, Idaho. Damped least squares inversion of travel time residuals (modified from the method of Aki) indicates a large body of 3.5±2.5% low relative velocity material centered under the northwest edge of the Snake River Plain. Less well resolved are high relative velocity bodies, one deep under the Idaho‐Wyoming border, the other 300 km below the Idaho batholith. Comparison with similar velocity mappings of the Yellowstone region indicates that the Snake River Plain low‐velocity anomaly is an aged extension of the low‐velocity body under the Yellowstone caldera. The upper half of the body has vanished in the eastern Snake River Plain, and the lower half is less anomalous than at Yellowstone. The strong dependence of mantle velocity structure on position under the Yellowstone‐Snake River Plain volcanic system indicates loss of heat to the surface primarily by advective (heat movement by mass movement) mechanisms, not by conduction. No discrimination between propagating rift and upper mantle heat anomaly models of this northeast progressing volcanic system is possible because velocity structures associated with these hot spot models have not been predicted quantitatively. Upper mantle heat anomaly models (thermal plumes, chemical plumes, gravity anchors) explain the observed structure with fewer ad hoc assumptions, but propagating rift models cannot be eliminated.

Soil exploration in a 500 m deep fjord, Western Norway

Abstract A number of engineering organizations and individuals have contributed toward a comprehensive feasibility study made in 1973–1974 in connection with a submerged floating tunnel project in Norway. The tunnel is planned to cross the 500 m deep Eidfjord in Hardanger over a length of about 1.3 km. The main findings from geophysical explorations, subsoil sampling operations, and an extensive laboratory testing program on extracted soil samples are described here. A main part of this paper is devoted to the study of a full‐scale field test with a gravity anchor block weighing 180 tonne. This study reports on the behavior of the block during launching from its sloping construction ground, the sinking operation, and the behavior of the block after it reached the bottom at 450 m depth. Observations of settlement and tilt are available, and a comparison is made between the observed and computed behavior. Broadly speaking, a fairly good agreement was found.