Segmental Construction Research Articles

The Ransom and Sarah Williams Farmstead: Post-Emancipation Transitions of an African American Family in Central Texas Vol. 2

In conjunction with the proposed construction of the southwest segment of State Highway 45 in southern Travis County, the Texas Department of Transportation sponsored archeological testing and data recovery efforts at the Ransom Williams farmstead. Prewitt and Associates, Inc., conducted an interdisciplinary community-based historic archeological study of the farmstead from 2005 through 2011. Extensive archival research reveals that the 45-acre farm was owned and occupied by Ransom Williams and his wife Sarah, both former slaves, from about 1871 to ca. 1905. The Williams family lived in the predominantly white rural community of Bear Creek, but they had connections to the nearby freedmen communities of Antioch Colony in northern Hays County and Manchaca in southern Travis County. The stories of the Ransom Williams family and their connections to these communities are enhanced by extensive oral history research, with over 46 hours of taped and transcribed interviews with 27 descendant community members. Data recovery investigations focused on a landscape archeological study to define the layout and design of the entire farmstead, including a stock pond and a network of dry-laid rock walls that facilitated water drainage, demarcated property boundaries, and formed livestock pens. Intensive hand excavations were used to examine features associated with the Williams house, outbuildings and activity areas, and a large trash midden. This work recovered more than 26,000 artifacts. They constitute an impressive material culture assemblage that is associated, with few exceptions, with the Williams family tenure on the land. The combined archival data, oral history interviews, and archeological evidence tell the fascinating story of how one African American farm family lived and thrived in central Texas during Reconstruction and into the Jim Crow era.

Experience Curve Effects in Bridge Construction

Learning is an essential part of life through which we accumulate experience, which then can help us to improve our ability to solve problems. In economics experience can improve productivity. The concept of the experience curve as a form of organizational learning was developed during the second half of the 20th century. It was especially promoted by the Boston Consulting Group and found its way into most textbooks on management and strategic planning; empirical data have been published for a number of industries. In the construction industry, however, very few data areavailable to support the concept. The largest obstacle for all researchers is to obtain the cost information as these are typically not shared by companies. Consequentially we have gathered cost data from four very large expressway bridges to study experience effects in construction projects. These were built in Bangkok, Thailand, by the same joint venture for the same owner during the periodfrom 1990 to 2000 using segmental bridge construction technology. The square meters of bridge deck serve as basic units and the four projects comprise some threemillion of these, so that impacts of increasing experience could be observed. The data for all four projects have been evaluated and adjusted for inflation. They support the idea that a costreduction of 20% can be achieved. The cost reductions must be actively pursued, there exists no automatic process.

An Experimental Study on the Behavior of Shear Keys According to the Curing Time of UHPC

Precast segmental construction has been recently developed to reduce the construction cost and shorten the construction term as compared to the cast-in-place method in a will to establish the design and erection system of structures using Ultra High Performance Concrete (UHPC). However, this method requires the presence of segmental joints to transfer the loads between neighboring segments, which stresses the importance of securing structural safety and serviceability. Therefore, need is for research on the behavior of the segmental joint for the structures erected by the precast segmental construction method. To that goal, this paper presents an experimental study on the behavior of shear keys with respect to the curing time of UHPC in the segmental joint. Analysis is done on the load-displacement relation according to the curing time of the shear keys and on the failure modes of the shear keys according to the cracking pattern at failure.

Discussion of “Equivalent Unbonded Length for Modeling of Multistrand Tendons in Precast Segmental Construction” by Marc J. Veletzos and José I. Restrepo

Discussion of “Equivalent Unbonded Length for Modeling of Multistrand Tendons in Precast Segmental Construction” by Marc J. Veletzos and José I. Restrepo

Tensor-product kernel-based representation encoding joint MRI view similarity.

To support 3D magnetic resonance image (MRI) analysis, a marginal image similarity (MIS) matrix holding MR inter-slice relationship along every axis view (Axial, Coronal, and Sagittal) can be estimated. However, mutual inference from MIS view information poses a difficult task since relationships between axes are nonlinear. To overcome this issue, we introduce a Tensor-Product Kernel-based Representation (TKR) that allows encoding brain structure patterns due to patient differences, gathering all MIS matrices into a single joint image similarity framework. The TKR training strategy is carried out into a low dimensional projected space to get less influence of voxel-derived noise. Obtained results for classifying the considered patient categories (gender and age) on real MRI database shows that the proposed TKR training approach outperforms the conventional voxel-wise sum of squared differences. The proposed approach may be useful to support MRI clustering and similarity inference tasks, which are required on template-based image segmentation and atlas construction.

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.

MIDAS-Based Finite Element Analysis of the Short Line Method of the Precast Segmental Bridge Construction

This paper studies the precast and cantilever erection process of pre-stressed concrete continuous beam bridge alignment control in short line method, basis on the construction of a light rail. Various stages of bridge construction performed on simulation analysis and calculated by the finite element software MIDAS, concluded the ultimate internal force and deformation values, and the maximum deformation are within the scope of design elevation deviation 20 mm allowed, as to achieve the target of bridge assembly.

Discussion on the Measurements in Cantilever Construction with Guyed Hanging Basket

Guyed hanging basket is qualified with reasonable structure , great carrying ability and clear construction process, and also can provide a good operating space for beam segment construction. Applying cantilever pouring construction with guyed hanging basket should be the development direction of the construction of large-span reinforced concrete cable-stayed bridge. By taking the girder construction of the grand bridge over Beijing-Hangzhou Canal as an example, this paper introduces the measurements in cantilever construction with guyed hanging basket, aiming at providing reference for other similar projects.

Engineering a Multicomponent Spinal Motion Segment-Like Construct from Mesenchymal Stem Cells

Introduction The task of engineering the intervertebral disc is challenging as the complex tissue needs to integrate with the host tissue and perform its function after the implantation. The vertebrae connected to the endplates are essential to integrate with the host vertebrae tissue which had been shown by Luk et al in whole disc transplantation.1 Hence, engineering the complex tissue needs to integrate the different components of the vertebrae (VB), cartilaginous endplate (CEP), nucleus pulposus (NP), and annulus fibrosus (AF); both biologically and mechanically. In this study, the multiple component spinal motion segments were fabricated by integrating these components. The construct was then loaded in a bioreactor and supplied with mechanical and biological stimulation. The functional aspect of the fabricated endplate-like construct was evaluated by a permeability test. Materials and Methods Rabbit mesenchymal stem cells (rMSCs) were encapsulated in collagen and induced to differentiate toward osteogenic and chondrogenic lineages before fabricating trilayered osteochondral (OC) constructs as previously mentioned. To test the nutritional function of the OC construct which acts as the endplate, rabbit nucleus pulposus cells (rNPCs)-encapsulated collagen microspheres were trapped in a sealed chamber formed with the OC construct such that the nutrients have to diffuse through the OC construct to reach the inside of the chamber. Cell viability of the rNPCs was then evaluated. To fabricate the multiple component construct, a rMSCs encapsulated collagen-GAG precipitate was added in between two OC construct and placed in between the shaft of the bioreactor. Then a layer of rMSC encapsulated collagen was formed around the construct to form the AF-like lamella. Torsional loading was applied onto the construct to study its effect on cell alignment in the AF-like lamella. Finally, one to three layers of AF-like lamellae were added to the spinal motion segment construct and cultured in the bioreactor with complex loading for 14 days. Histological, ultrastructural, and mechanical evaluation was done on the construct. Results In the custom developed functionality test for nutrient transport, the rNPCs in the chamber were viable at the end of the culture showed that nutrients were able to diffuse through the OC construct. For the effect of torsional loading on cell alignment in the AF-like lamella, alignment analysis showed that the cells were aligned along a preferred axis under torsional loading compared with control group without loading. However, no collagen fibers alignment was found in this study. The multiple component construct was fabricated with each component similar to the spinal motion segment. The different components of the construct were well integrated throughout the culture and were shown by histology. Mean torsional stiffness of the constructs significantly increased as the number of rMSC encapsulated AF-like layer increased. Conclusion This study demonstrated the feasibility to engineer a spinal motion segment-like tissue with collagen and MSC. The OC constructs demonstrated its nutritional function and can be used as a vertebra-endplate construct in this model. rMSC encapsulated in collagen gel can be induced to re-orientate and align in a certain direction by applying cyclic torsional force on the tubular structure. This can be a tissue engineered model to study the effects of various strategies in functional remodeling and maturation of the intervertebral disc. Disclosure of Interest None declared Reference Luk KD, Ruan DK. Intervertebral disc transplantation: a biological approach to motion preservation. Eur Spine J 2008;17(Suppl 4):504–510

Effects of model segmentation approach on the performance and parameters of the Hydrological Simulation Program – Fortran (HSPF) models

Although models are one of the most powerful tools for watershed management, their effectiveness is limited by prediction uncertainties resulting from not only model input data but also spatial discretization. In this paper, Hydrological Simulation Program – Fortran (HSPF) models were constructed for the Linyi watershed according to three segmentation approaches including model segments based on differences in: (1) sub-watershed, (2) meteorological station, and (3) physical characteristics. Then the static sensitivity method and dynamic sensitivity method were employed to evaluate the effect of the segmentation approach on model performance and parameters of HSPF. The main conclusions were: (1) modeling with 12 segments had the best simulation efficiency and the corresponding estimated parameters had a certain representation within the Linyi watershed; (2) HSPF model performance was significantly affected by the segmentation approach, especially by the model segmentation construction process which considering a meteorological station or not; (3) parameters INTFW (interflow inflow parameter), lower zone nominal storage, and upper zone nominal storage (UZSN) were most affected by the model segmentation approach, while parameter AGWRC (groundwater recession coefficient) changed indistinctly; (4) parameters UZSN and INTFW had the same variation tendency whenever the segmentation approach changed.

The Complex Fungal Microboring Trace Saccomorpha stereodiktyon isp. nov. Reveals Growth Strategy of its Maker

A complex microboring trace of fungal affinity is described in shells as a new ichnotaxon Saccomorpha stereodiktyon isp. nov. and compared with the earlier established ichnotaxon Saccomorpha terminalis Radtke, 1991. The new trace is characterized by a three-dimensional network of tunnels composed of a bifurcate horizontal (parallel to substrate surface) network with an upright (perpendicular to surface) system of tunnels and by the formation of cylindrical to multilobate terminal sporangial swellings. The new trace shares with Saccomorpha terminalis Radtke, 1991 the terminal position of sporangial swellings but differs from this ichnotaxon by its complexity in spatial arrangement, segmented construction, and ramification of tunnels. The horizontal parts of the network in the new taxon adhere to the substrate surface and regularly produce thinner tunnels that explore the interior of the substrate, allowing the producer to participate in digestion of organic lamellae incorporated in the shell. Microborings similar to the new trace fossil have been observed in modern bivalve shells of the Atlantic Ocean, North Sea, Adriatic Sea and Red Sea at depths ranging from the intertidal down to 1,550 m. The fossil record of the trace reaches back to the Jurassic and the type material stems from a Lower Oligocene oyster shell. The study shows that complex microboring traces reflect both behaviour and developmental strategy of their makers.

Design procedure of segmented rotor switched reluctance motor for direct drive applications

Switched reluctance motors (SRM) are becoming increasingly popular because of the rising cost of permanent magnets. It was reported that segmented rotor construction improves the torque output and efficiency. This study discusses an SRM with segmented rotor construction designed for direct drive application. Such a motor has an outer rotor. It is found that in such machines, the torque output increases when there are higher number of rotor segments than stator poles. A segmented rotor SRM with 12 stator poles and 26 rotor segments is discussed here. It has unique pole tip shape, which improves torque output. Design procedure of the motor is presented. Moreover, limitations of segmented rotor SRMs having a higher number of rotor segments than stator poles are also identified, and possible solutions are suggested. Experimental results on the prototype of a three-phase 12/26 motor are presented.

Lessons Learned from Construction of Shanghai Metro Stations: Importance of Quick Excavation, Prompt Propping, Timely Casting, and Segmented Construction

AbstractFour metro stations with similar supporting systems and pit geometries in Shanghai soft clay were excavated using different soil removal procedures, which led to distinctly different pit behaviors. Through analyzing and comparing the well-documented field data from these four bottom-up excavations, the significances of quick excavation, promptly propping, timely casting of floor slabs, and segmented construction in control of pit deformations were identified and their influences were comprehensively quantified. As to these four pits, the measured time-dependent wall deflections and wall heaves in 20–35 days at relatively deep excavation levels were up to 47–94% the magnitudes at completion of excavation to the final depths. The measured postexcavation wall deflections in about 20–30 days were up to 36–45% the maximum wall deflections at completion of excavation and the corresponding postexcavation deflection rates were up to twice those during excavation. The poorly excavated pits, which featured ...

ANP Model for Evaluation of False-work Systems for Cast-in-place Cantilever Bridges

The terrain of Taiwan is characterized by large areas of mountains, while lands in urban areas have become increasingly difficult to acquire for developing infrastructures. To reduce environmental impacts and to improve traffic conditions, highway projects have adopted more and more bridges over the years and many advanced bridge construction methods have been introduced. In terms of construction of bridge superstructures, the cast-in-place cantilever method has seen wider use with many successful examples. This study investigated the false-work systems that may be selected for use in implementing the cast-in-place cantilever method in Taiwan, with the objective of developing a model for evaluating possible options. Based on a review of related researches, an evaluation framework for the false-work systems has been proposed first, which consists of six factors: system controllability, structural stability, initial cost, operating cost, segment cycle time, and closing segment construction time that are categorized into three aspects: reliability, cost, and speed. Because of the interdependencies among the factors, the model uses the analytic network process (ANP) to produce the weights of the factors and the ratings of the options in given project conditions. An illustrative example is provided, in which three false-work systems considered for a hypothetical box-girder bridge project are evaluated. The rankings of the options obtained for the example from best to worst were triangular truss, diamond truss, and suspension truss. Practitioners may use the model as a decision aid in evaluating and selecting false-work systems for the cast-in-place cantilever method for construction of bridge superstructures.

A new access density definition and its correlation with crash rates by microscopic traffic simulation method

Better access management can improve highway safety by reducing potential crashes and conflicts. To make adequate access management decisions, it is essential to understand the impact of different access types on roadway safety, usually represented by the crash rate of a roadway segment. The objective of this paper is to propose a new access density definition reflecting the impact of traffic speed variation of different access types. The traffic speed variation was obtained from a microscopic traffic simulation software package TSIS-CORSIM. A sample roadway Temple Terrace Highway was selected to perform traffic simulation. Access Weight was obtained from traffic speed variation, and access density was obtained from access weight. The proposed access density was then compared with the existing definition by analyzing their correlations with crash rates on one suburban street in Temple Terrace, Florida. The comparison demonstrates that crash rates are more highly correlated with the proposed access density than that in the previous study, which is helpful for Federal Highway Administration (FHWA), United States Department of Transportation (USDOT), and transportation consulting companies to regulate the construction, management and design of roadway segments.

Application of Displacement Back Analysis in Geometry Monitoring of Segmental Construction of Prestressed Concrete Continuous Girder Bridge

This paper apply displacement back analysis theory for geometry form monitoring and calculating work of segmental construction of prestressed concrete continuous girder bridge, making use of displacement back analysis method to optimize bridge structure parameters, ensuring accuracy of geometry form control with calculated results of every girder segment in entire construction. This method is used in the construction monitoring and supervision for Yuanyichang circular curved rigid frame bridge on Pingan-Adai highway, to make the closure accuracy and the bridge geometry form reaches the effect of aspiration. Through the result of the finished bridge, what we can obtain is that the displacement back analysis theory could fulfill the requirement of factual project and be widely used for geometry monitoring of segmental construction of prestressed concrete continuous girder bridge.

Computer-guided mandibular fracture treatment

Purpose: This study aimed at evaluating the accuracy of computer guided mandibular fracture reduction. Patients and method: Ten patients were included in this study. A preoperative radiographic assessment cone beam computed tomography (CBCT) scan was performed to all patients. The digital imaging and communications in medicine (DICOM) files of the CBCT were imported by the MIMICS software then a 3D construction and virtual reduction of the fracture segments was performed. A virtual bone borne surgical guide was designed exported by the software as a standard tessellation language STL file. The STL file was imported by a 3D printing machine and a physical guide was constructed. ORIF was done for all patients and the fracture segments were anatomically reduced by the aid of the computer surgical guide. A post operative CBCT was obtained 7 days post operatively. Results: There was no statistically significant difference between the virtual reduction and the actual reduction. Conclusion: The usage of the computer based surgical guide was found to be beneficial for the edentulous patients, and partially edentulous patients with insufficient teeth to act as an occlusal guide.

A local-global scheme for tracking crack path in three-dimensional solids

This paper aims to contribute to the three-dimensional generalization of numerical prediction of crack propagation through the formulation of finite elements with embedded discontinuities. The analysis of crack propagation in two-dimensional problems yields lines of discontinuity that can be tracked in a relatively simple way through the sequential construction of straight line segments oriented according to the direction of failure within each finite element in the solid. In three-dimensional analysis, the construction of the discontinuity path is more complex because it requires the creation of plane surfaces within each element, which must be continuous between the elements. In the method proposed by Chaves (2003) the crack is determined by solving a problem analogous to the heat conduction problem, established from local failure orientations, based on the stress state of the mechanical problem. To minimize the computational effort, in this paper a new strategy is proposed whereby the analysis for tracking the discontinuity path is restricted to the domain formed by some elements near the crack surface that develops along the loading process. The proposed methodology is validated by performing three-dimensional analyses of basic problems of experimental fractures and comparing their results with those reported in the literature.

Development of Back-to-Back Flexible HVDC Prototype Based on MMC

With the development of flexible HVDC technology in the world, back-to-back HVDC system based on MMC topology have more attention. A high power back-to-back flexible HVDC prototype has been developed to assess performance and reliability of construction of converter valve segment. Valve normal working condition (rated conditions rated voltage, current, temperature), valve transient working condition (temporary overvoltage, overcurrent), valve fault protection and anti-interference ability are accessed. Performance and reliability of control and protection equipment are assessed. The design of control and protection strategy is optimized. The correctness of main circuit design is tested.

Segmental Self-Growing Rod Constructs in the Management of Early Onset Neuromuscular Scoliosis

Surgical treatment options for Early Onset Neuromuscular Scoliosis (EONMS) include spinal fusion versus growth sparing techniques, early treatment of progressive curves without fusion is important to improve respiratory and visceral development and to normalize spinal growth as much as possible.