Segmental Cantilever Research Articles

Mechanical characteristics of hoisting construction of segmental cantilever assembled box girder bridge

Abstract In order to study the safety of the segmental box girder in the hoisting process, this paper designed the construction method of the gantry crane hoisting segmental box girder in combination with the actual project. By establishing a mathematical model, the mechanical properties of the segmental box girder under two different hoisting schemes were analyzed. Under different load conditions, the lifting analyses, translation analyses and descending analyses of the box girder were carried out respectively, and the deflection and stress corresponding to the box girder were obtained. Considering the displacement and stress results of the box girder under the two hoisting schemes, it was concluded that the hoisting construction of the segmental box girder should give priority to the second hoisting scheme. That is, the hoisting holes were opened at the flange position of the roof. Provide feasible technical support for future construction.

Segmented Cantilever and Array Configurations for Wider Frequency Band and Higher Power Generation in Piezoelectric Vibration Energy Harvester

This letter reports a piezoelectric vibration energy harvester which energy conversion efficiency is significantly improved by arraying piezoelectric sheets on cantilever beams, and the operation frequency band is widened by applying two‐segment cantilever beams. A prototype is developed and tested. In this case, two group piezoelectric arrays are combined on the cantilever beams with the optimum load resistance. The total output power remains above 6.54 mW within the operation frequency band ranges from 27.5 Hz to 37.5 Hz when the generator is under an acceleration of 0.7 g and reaches two power peaks: 20.5 mW at 29.2 Hz and 12.95 mW at 35.4 Hz.

Moment Redistribution in Segmental Cantilever Bridges: Simplified Approach

Moment redistribution due to creep of concrete in cast-in-place segmental cantilever bridges can be accounted for with sophisticated software. Although this approach to design frequently is preferred, experienced engineers often do a final check based on hand calculations that have stood the test of time. This paper deals with the latter approach. Principles governing moment redistribution due to creep were revised, and results from this investigation were used to develop a novel graphical aid suitable for hand calculations in an attempt to estimate the magnitude of tensile stresses due to moment redistribution because of creep. It was found that tension stresses due to creep are not likely to exceed 2 MPa (290 psi) because the post-tensioning provided by top cables balance approximately 70%–85% of the bending moments due to concrete weight. An example for routine designs was provided.

Novel integrated ground anchor technology for the seismic protection of isolated segmented cantilever bridges

An external restraining system which is anchoring the bridge superstructure to the embankment backfill is proposed in this study for the seismic protection of isolated bridges. The restraining system is employed to reduce the seismic demands of the bridge deck by utilising the otherwise inactive ground behind the abutment back-walls. The system can be described as fastening the bridge end-diaphragms to the rocky strata that lie beneath the abutment backfill. The anchoring is achieved through a series of steel strands grouted to the rock to achieve a strong anchoring capacity. Indeed, the proposed anchor is flexible enough to allow the thermal, creep and shrinkage serviceability movements of the deck. A parametric study conducted in this paper shows that the ground anchor external restraining system is truly effective in reducing the seismic demands of the bridge deck.

Prestress Loss Test and Analysis of Long Span Continuous Rigid Frame Bridge

Prestress loss has a great influence on working performance of bridge structure, which is concerned highly by the engineers. In this paper, based on a large span continuous rigid frame bridge, the prestress change during the construction and prestress loss after closure is tested and analyzed by laying the magnetic flux sensor. The test and calculation results show that during segmental cantilever construction process, the measured values is very close to the theoretical value, indicating that the magnetic sensor is reliable. After the whole bridge is closed, the prestress value of T10, D6 and D2’ decreases with time, and the change trend is basically the same for 150 consecutive days for which have no any construction work on the bridge deck. This result has a high reference value for the design and construction of long-span prestressed continuous beam (rigid) bridge.

Simulation Analysis on Construction of Liangjiang Great Bridge

Liangjiang Great Bridge is the prestressed concrete continuous rigid frame bridge with high pier and long-span. It adopts the segmented cantilever construction method. The process of its construction is the key to the construction control simulation analysis. In this paper, based on the characteristics of the bridge construction, finite element method is used to establish the simulation model. Cantilever construction stages and closure stages of bridge are simulated and analyzed. The structure deflection diagrams in the each section construction and the later construction considering the creep and shrinkage of concrete are obtained. The initial camber of each segment is given in the construction. The stress characteristics of key section are analyzed in the construction process. It provides a basis for monitoring and on-site construction of bridge and the reference for similar bridge construction.

The Application of BP Neural Networks in Cable-Stayed Construction Control

Through the related technical information of the monitoring of bridge construction, this is to determine BP neural network's input and output parameters, to establish the neural network fore-casted model, and to carry through the prediction to the main beam of deflection. In the application, the data of deflection deviation has generated through the cast-in-place segmental cantilever to train the BP neural network. The deviations which are produced in the pre-run neural networks predict the follow-up segment in construction, and then simulation control in the cable-stayed bridge is realized in construction process.

Quasi-Static Cyclic Testing of a Large-Scale Hybrid Sliding-Rocking Segmental Column with Slip-Dominant Joints

This paper presents the findings of an experimental study that investigated the response properties of segmental cantilever columns incorporating internal unbonded posttensioning (PT) and slip-dominant (SD) joints. The SD joints exhibited controlled sliding that provided energy dissipation with low damage. All joints of these columns, except for the bottom one, were designed to be SD. The bottom joint was designed to be rocking dominant (RD) and exhibited rocking that offered self-centering to the system. Design objectives and equations are presented. These equations were used for the design of a large-scale cantilever column that was subjected to reverse lateral cyclic loading at its top end, reaching a maximum drift ratio of 14.9%. At small drift ratios (≤3%), the response was dominated by sliding of the SD joints that provided energy dissipation (damping). For medium drift ratios (between 3 and 10%), rocking at the bottom joint increased and provided self-centering properties to the system. For large drift ratios (>10%), the self-centering properties decreased, but the damping properties remained practically constant. Rocking at the SD joints remained small at all times. Minor spalling was observed in the SD joints, while concrete crushing was observed at the bottom joint.

Simplifying cantilever sensors: Segmental analysis, a way to multiply your output

Abstract Bending experiments on micromechanical cantilevers (MMC) are a powerful tool to measure small amounts of chemical or biological analytes. By applying segmental cantilever readout technique we demonstrate that the investigation of MMC segments is sufficient to obtain reliable curvature values. This allows one to perform multiple bending experiments on a single MMC and by that to multiply the possible output per MMC. Furthermore we demonstrate how segmental MMC readout can be used to locate differently coated areas.

Launching Gantries for Building Pre-cast Segmental Balanced Cantilever Bridges

Which bridge spans and types are suitable for construction by the precast segmental balanced cantilever bridge method? The reasons for the selected range of bridge will be described and the cost, quality and programme advantages will be described in this paper. The generic forms of such machines will be explained. This will include the effect that they have on the permanent structure, and thus the way in which the availability of existing machinery may affect the design of the bridge. The principal components of the machines will be highlighted, with consideration of the effect of the variety of equipment on cost and productivity. The overriding concerns on safety of the operation of the machine will be discussed. Aspects of design of the machine and its interaction with the permanent bridge structure will be discussed. The importance of the input of the main contractor will be discussed. The advantages of separating machine design from supply compared with the design / supply route will also be considered in this paper.

Alignment Control during Construction of Continuous Bridge Suspended by Triangle Frame

The features of a new type of continuous bridge suspended by triangle frame are introduced in this paper. In view of the segmental cantilever construction method engaged in main girder construction, we put forward to the method of pre-camber setting and the calculation of formwork elevation and field measurement of displacement.

The A13 viaduct: construction of a large monolithic concrete bridge deck

The A13 viaduct is a new structure carrying the A13 road around Ford's Dagenham plant. The structure was designed with the dual aim of fast mechanised construction by the use of glued segmental cantilever construction and of providing a low-maintenance structure with minimum joints and bearings. The use of continuity is actively encouraged in UK standards as it has obvious design and durability advantages; this paper describes the design and construction of this large fully continuous, precast pre-stressed segmental concrete structure. Emphasis is placed on the design and construction methods used to form the innovative 54 000 m2 monolithic deck from 1030 precast segmental units giving a 1750 m long continuous structure.

The A13 viaduct: construction of a large monolithic concrete bridge deck

The A13 viaduct is a new structure carrying the A13 road around Ford's Dagenham plant. The structure was designed with the dual aim of fast mechanised construction by the use of glued segmental cantilever construction and of providing a low-maintenance structure with minimum joints and bearings. The use of continuity is actively encouraged in UK standards as it has obvious design and durability advantages; this paper describes the design and construction of this large fully continuous, precast pre-stressed segmental concrete structure. Emphasis is placed on the design and construction methods used to form the innovative 54 000 m2 monolithic deck from 1030 precast segmental units giving a 1750 m long continuous structure.

Experimental Verification of a Method of Detection of Crack in Taper and Segmented Beams Based on Modelling of Transverse Vibration

In this note a method for prediction of location and size of a crack based on measurements of natural frequencies has been verified experimentally considering taper and segmented cantilever beam geometries. The analysis is based on the concept of a rotational spring to represent the crack section and the Frobenius method to solve differential equation with variable coefficients. The crack size is computed using a relation between stiffness and crack size. The maximum error in predicting the crack locations is 8%. The maximum error in predicting the crack size is 20%.

Simulation of the construction of cable-stayed bridges

Cable-stayed bridges are ideal for spanning natural barriers of wide rivers, deep valleys, or ravines, and for pedestrian bridges crossing wide interstate highways. Modern construction of cable-stayed bridges makes use of the segmental balanced cantilever techniques and involves many repetitive cycles of placing the concrete segments (both cast-in-place and precast) and supporting cables. It provides a fertile area for the application of computer simulation techniques for the planning and analysis of the process, particularly for studying the interaction of resources used in the construction phase and also for assessing the productivity of the construction processes. This paper employs MicroCYCLONE, a microcomputer-based simulation program, for the modeling and simulation of the construction of two cable-stayed bridges: the Dame Point Bridge in the state of Florida, U.S.A., and the Tsukuhara Bridge in Hyuougo, Japan. The paper will also provide a brief explanation of the suspended long traveler method used on the Tsukuhara Bridge, the simulation models developed to analyze the construction processes, and the results of sensitivity analyses.Key words: simulation, modeling, construction, cable-stayed bridges, resources, productivity, balanced cantilever construction.

Bridge over the Jhelum River, Pakistan

The Jhelum River in Pakistan runs through a mountainous area in a high risk seismic zone, and its flow volumes vary dramatically with the seasons. At the town of Karote, a new bridge has been built after record floods in September 1992 rose 8 m above the deck, subjecting the previous bridge to extreme loading from thousands of tons of logs, debris and boulders, leading to stability failure. In July 1993, the National Highway Authority, with a credit from World Bank, invited international bids for reconstruction on a turn-key (design-and-construct) basis. After examining comparative costs and time schedules, a bid was submitted for construction of a post-tensioned concrete segmental cantilever bridge.

Segmental Cantilever Bridge Construction Case Study

The cast-in-place segmental cantilever construction method, further to its well-known advantages for long span bridge construction in general, does provide appropriate means to satisfy local needs for relatively long spans in an urban environment, practically without infringing on traffic or property below. Detailed are the structural considerations and construction challenges in the use of segmental cantilever bridges in two such urban environment cases for the Los Angeles County Metropolitan Transit Authority Metro Rail System. The Kramer Bridge is a continuous four-span box girder bridge 189 m (620 ft) long spanning over what previously was a hazardous-waste site. The Rosecrans Bridge is a continuous three-span box girder bridge 204 m (670 ft) long spanning diagonally over a busy city intersection. Despite difficulties experienced in the piling, cantilever, alignment, and closure operations, the cast-in-place segmental cantilever construction method allowed fast and economically competitive construction of two aesthetically pleasing structures.

Minimum cost design of RC beams with segmentation using continuum-type optimality criteria

Economic designs of reinforced concrete beams with segmentation involving costs of concrete, reinforcing steel and formwork are considered. For practical reasons, the design variables are prescribed by means of an unknown constant and given shape function, whereas the constraints in addition to lower and upper bounds on design variables include maximum deflection in the span, flexural and shear strengths. Conditions of minimality are rigorously derived using calculus of variation on an augmented Lagrangian. An iterative procedure describing the computational aspects of the design is presented using a segmented propped cantilever beam as an example. Numerical examples are presented when the design variables involved are the depth alone or both the depth and steel ratio. A practical application of a simply supported beam is also considered and results compared with those obtained using nonlinear programming techniques (Karihaloo 1993; Kanagasundaram and Karihaloo 1990). An examination of the rate of convergence shows that the present technique is very promising.

Design-Construction of Precast Segmental Elevated Metro Line for Monterrey, Nuevo Le6n, Mexico

Paul E. Mondorf obtained his M.Sc. engineering degree from the Technical University of Denmark, Copenhagen, where he was also assistant professor for 4 years. Over the major part of his career, Mr. Mondorf has been active in the design and construction of concrete structures around the world , such as concrete platforms for the North Sea, containment vessels for nuclear plants in France and Spain, and a large variety of bridges, including cast-in-place and precast segmental cantilever bridges. Recently, he was field construction engineer for the third Lake Washington Bridge, Washington, resident engineer for the CSX Escambia Bay Crossing, Florida and advisor to the general contractor who built the Metro in Monterrey, Mexico. Currently, he is resident engineer for the construction of the Los Angeles Metro Green Line segmental bridges.

OPTIMIZATION OF CABLE-STRETCHING PLANNING IN THE CONSTRUCTION OF CABLE-STAYED BRIDGES

A general model for the optimal planning of a cable-stretching process has been formulated and used to obtain solutions for the optimal planning of the cable-stretching process associated with various design and construction considerations. A structural analysis approach considering the variation of the structural system during cable-stretching has been presented by using the concept of an influence pattern. In the case of segmental cantilever construction, calculation of the initial stress and displacement prior to stretching the stay cables has been investigated. Computational efficiency in solving the optimal planning problem has also been studied.