Pouring Sequence Research Articles

Research on Reasonable Construction Plan for Cast-in-Place UHPC Bridge Deck Plate of Cable-Stayed Bridge

This article takes a single-tower cable-stayed bridge with a steel-UHPC composite deck steel box girder as the research object and develops different casting plans for the UHPC layer on the bridge deck. It analyzes the influence of factors such as the block casting sequence of the UHPC layer on the bridge deck, whether or not to set up a post-casting section, whether or not to set up bridge deck counterweights and the range of it on the additional deformation and stress of the formed UHPC bridge deck during the construction stage, exploring the impact of various factors on the structural target bridge’s completion status (cable force, bridge completion linearity, bridge deck and steel box girder stress) under different pouring schemes. Research has shown that under the constant initial tension of stay cables, adjusting the pouring sequence of UHPC bridge decks and setting post-pouring sections is not significant in reducing the tensile stress of UHPC bridge decks. The more effective technical measure is to use bridge deck counterweight pouring during construction; the closer the counterweight is to the later stage constant load loading value, the more significant the decrease in UHPC tensile stress is. When factors such as on-site construction conditions, construction period, and labor costs are limited, local weight balancing on the bridge deck can be used.

The Amelia Earhart network tied arch bridge replacement project, MO, USA

A replacement for Amelia Earhart Bridge, carrying Highway 59 across the Missouri River (MO, USA), has been constructed. Interactions between the flow around this bridge and two existing bridges adjacent to the new bridge had the potential to create large scour holes. As the original bridge needed to remain open during the construction of its replacement, a scour study was performed to determine the placement of the piers. The new bridge uses prestressed concrete bulb T-girder spans for the approaches and one 160.6 m (527 ft) steel network tied arch for the main navigation span. The bridge was designed in 2008 and was one of the first modern tied arch bridges in the USA to use internal redundancy for fracture-critical members using bolted angles at the intersection of the tie girder webs and flanges. Due to vertical clearance constraints, the tied arch contains a framed-in-floor system to minimise the depth of the structure. This also required a specific slab pouring sequence to relieve the elongation effects of the tie girder during construction. This signature structure opened to traffic in 2012 and project completion occurred in summer of 2013. This paper focuses on the pier placement relating to scour concerns and the design of the tied arch span.

Seismic stability analysis of the large-span concrete-filled steel tube arch bridge considering the long-term effects

Creep and shrinkage of the confined concrete changes the dynamic performance of concrete-filled steel tubular (CFST) arch bridges over time. However, less attention is paid to the seismic behaviour of CFST arches considering such long-term effects. The effects of long-term behaviour on the dynamic strength of CFST arch bridges are analysed and discussed in detail in this paper. A novel dynamic stability analysis method for structures subjected to any arbitrary excitations is proposed and validated. The time-dependent properties of concrete have been numerically implemented and also the difference in concrete pouring time at different arch positions is considered. An existing large-span CFST arch bridge is analysed as a case study adopting the proposed method. Moreover, the long-term performance evolution of CFST sections are discussed. It is found that the creep-induced stress within CFST sections has a great influence on the dynamic stability of arch bridges. The critical peak ground acceleration (PGA) at the 1000th day of the service life is suggested as the reference value for the limit state under earthquake excitations. The influence of travelling wave effect and concrete pouring sequence are also investigated. Finally, the post-seismic performance of the whole bridge is evaluated.

Practical Evaluation Method for the Pouring Scheme of a Long‐Span Concrete‐Filled Steel Tube Arch Bridge

Concrete pouring steel tube arch is a critical part in the construction of a long‐span concrete‐filled steel tube arch bridge. With the adoption of the improved TOPSIS, this study summarized five indicators that controlled the concrete‐filled steel tube pouring sequence. The indicators include the vertical displacement of the arch rib, lateral offset of the arch rib, steel tube stress, concrete stress, and elastic safety factor of the arch rib. Furthermore, a comprehensive objective function‐rationalization index was proposed, based on which a practical evaluation and determination method for pouring scheme of the long‐span concrete‐filled steel tube arch bridge was developed. The results showed that a pouring sequence with relatively small stress in the arch rib, advanced alignment, and good stability could be determined using the proposed method.

Study on PC Continuous Girder mechanical properties Based on Tendon Tensioning Pattern

prestressed concrete continuous box girder in China. With the change of condition in the construction site, the construction sequence of the bridge will be changed inevitable, so to adjust the tendon tension mode accordingly, which will cause the alteration of structural mechanics performance. The finite element analysis model of a continuous girder will be built to compare the difference with two tendon tension cases according to relevant pouring sequence. The related conclusions are obtained, so can help to provide beneficial reference for the similar engineering.

Experimental Study on the Shear Performance of Shallow Hinge Joints for Prefabricated Hollow Slab Bridges

To investigate whether shallow hinge joint fracture was caused by shear stress or flexural stress, during the demolition and reconstruction of Xiaojiang River bridge, two original girders were collected and shipped to the lab, and the shallow hinge joint between the two girders was rebuilt. Tests were performed to investigate the cracking load, failure mode, and force transmission performance of the hollow slab girder and shallow hinge joint under vehicle load. The test result shows that under eccentric load, when the load increases to 365 kN, the midspan bottom slab of the testing girder starts to fracture; as the load increases to 560 kN, the roof slab of the testing girder starts to fracture; the hinge joint has a maximum horizontal opening of 0.153 mm and vertical relative displacement of 0.201 mm; during the entire test loading process, the shallow hinge joint structure does not develop fracture and shear failure; and the shallow hinge structure demonstrates excellent shear stress transmission performance. In addition, based on hinge slab theory, the hinge joint internal force under vehicle load was calculated. Based on ACI 318‐05 specification, CAN/CSA‐S6‐00, and JTG D61‐2005, the hinge joint shear bearing capacity was calculated. Hinge joint stress resistances calculated from the three specifications all exceed the internal force. Among them, the calculation results from ACI 318‐05 and CAN/CSA‐S6‐00 are similar, while the result from JTG D61‐2005 specification significantly exceeds the internal force, which is mainly because the designed concrete direct shear strength fvd in the Chinese specification does not consider factors such as bonding surface coarseness, concrete pouring sequence, and material properties. Theoretical calculations and tests show that the actual failure mode of the shallow hinge joint in prefabricated hollow slab girder bridges is not caused by shear stress.

A Comparative Evaluation of Accuracy of the Dies Affected by Tray Type, Material Viscosity, and Pouring Sequence of Dual and Single Arch Impressions- An In vitro Study.

The clinician's skill, impression techniques, and materials play a very important role in recording fine details in an impression for accuracy of fixed partial denture prosthesis. Impression of prepared teeth and of the opposing arch can be recorded simultaneously by dual-arch trays, while the full arch metal trays are used for impressions of prepared teeth in one arch. To measure and compare the accuracy of working dies made from impressions with metal and plastic dual arch trays and metal full arch trays, for two viscosities of impression material and by changing the sequence of pour of working and non-working sides. A balanced design with independent samples was used to study the three variables (tray type, impression material viscosity, and pouring sequence). An impression made by dual arch trays and single arch trays were divided in to three groups (Group A-plastic dual arch tray, Group B-metal dual arch tray, Group C-full arch metal stock tray). Out of these three groups, two groups (Group A and B) were subdivided in to four subgroups each and one group (Group C) was subdivided in to two subgroups. A sample size of 30 was used in each subgroup yielding a total 300 impressions in three groups or ten subgroups. Impressions were made of a machined circular stainless steel die. All three dimensions (Occlusogingival, Mesiodistal, and Buccolingual) of the working dies as well as stainless steel standard die were measured three times, and the mean was used for the three standard sample values to which all working dies means were compared. Statistical analysis used for this study was a 3-factor analysis of variance with hypothesis testing at α =0.05. With respect to the selection of impression material viscosity statistically significant differences were found in the dies for the buccolingual and mesiodistal dimensions. Metal dual arch trays were slightly more accurate in the mesiodistal dimension in comparison to the plastic trays in reference of tray selection and in view of pouring sequence no differences were observed in occlusogingival dimension but in buccolingual and mesiodistal dimensions nonworking side was more accurate. The gypsum dies produced from the dual arch impressions were generally smaller in all three dimensions than the stainless steel standard die. Plastic dual-arch trays were more accurate with rigid impression material and there was not statistically significant difference for sequence of pouring. Metal dual-arch trays were more accurate with monophase impression material and working side was more accurate. Stock metal full arch trays were more accurate for monophase impression material.

First come, first served. Does pouring sequence matter for consumption?

Various environmental factors associated with eating and drinking affect people’s food choice and food intake. Lately, the role of tableware has been studied in more detail. The aim of this study was to determine whether pouring sequence of food components affects portion size. Study 1 invited participants to pour a beverage containing both apple juice and sparkling water. Pouring apple juice first increased juice by almost 25% compared to pouring water first. Pouring water first increased water by almost 19% compared to pouring juice first confirming our hypothesis that pouring sequence affects the ratio poured. Study 2 asked participants to prepare themselves a snack containing cereals with milk. Within-subject comparisons revealed that pouring milk before cereals significantly increased both milk and cereal amounts resulting in larger overall portion size compared to pouring cereals before adding milk. Habitual tendencies for preparing foods causing a perception bias or a perception bias itself could be possible explanations for the divergent study findings. These findings show for the first time the influence of pouring and preparation sequence on portion size.

Research on Influence of Concrete Pouring Sequence on Stability of High-Formwork Support System

ANSYS finite element analysis software is used to simulate the changes of maximum lateral displacement of the high-formwork support system in different sequences of pouring concrete. In the condition of loading which was applied from one side to the other side, the maximum lateral displacement of the frame had a sudden increase in each loading process. In the condition of loading which was applied symmetrically, the maximum lateral displacement of the high-formwork steadily rising nearly straight with the load applied. So the symmetrical pouring concrete ways is better for the whole stability of the high-formwork.

Influence of Concrete Pouring Sequence on Stability of Different Height High-Formwork Support System

This article used ABAQUS finite element analysis software to established the high-formwork, analyzed effect on stability of the different height formwork by contrasting lateral displacement of various heights, discussed influence of concrete pouring sequence on stability of different height high-formwork support system in the construction process. From the simulated result, it can be seen that with the increase of height, the lateral displacement increased gradually when poured in dissymmetrical way, but the stability of high-formwork decreased, the result also provides evidence for code revision.

Whole-Process Analysis of the Mechanical Responses of High Formwork Support Systems during Concrete Pouring

An underground club in Xian is taken as the research object to explore the mechanical response of the internal poles of its high formwork support system during concrete pouring. The internal force static measurement of the high formwork support system is carried out. Each stage of the concrete pouring is simulated by the finite element analysis software ANSYS in the form of load step, whose results are contrasted with the measured results. The contrast reveals that the concrete pouring sequence has direct influence on the tendency of poles axial force and on the location of maximum axial force and that it is reasonable to adopt imaginary horizontal force which simulates the initial defects to carry out the overall stability analysis of the high formwork support system. It is pointed out that the program of setting up the formwork and the concrete pouring sequence should be determined with the finite element analysis.

Concrete mix pouring sequence for uniform setting and curing of bridge decks

Concrete bridge decks are cast in segments using multiple mix batches in a process that can extend up to an entire working day. Construction codes state that the initial concrete must stay plastic over the entire casting operation, however this requirement is practically impossible to achieve with regular casting and curing procedures. This paper reports the experimental evaluation of the performance of a suggested pouring sequence of class K concrete designed for bridge decks, where retarding and accelerating admixtures were used to achieve homogeneous thermo-mechanical concrete properties based on uniform setting and curing at early age. The proposed pouring sequence was investigated in both laboratory conditions as well as in outdoors environment. In order to optimize the resulting properties, the effects of different curing methods were investigated. Taking into consideration variation in environmental conditions at a regular construction season of late spring and summer in West Virginia, the suggested sequence was able to achieve uniform setting times as well as thermal properties while being placed along an entire working day.

Prediction of concrete initial setting time in field conditions through multivariate regression analysis

Construction of large concrete structures usually requires pouring multiple batches of concrete mixes along 1 day, which creates setting irregularities that increase the potential of crack development within pours. For the case of bridge decks, it is recommended that the initial concrete material should stay plastic over the entire casting operation of a poured bridge segment. Uniform setting of multiple batches is possible if setting times could be predicted and controlled in field conditions. In this study, more than 70 different Class K concrete mixes were manufactured and cast in field conditions, which provided material characteristics along with environmental data that were used to predict concrete initial setting times through multivariate regression analysis. Two prediction models were achieved, corresponding to the addition of set retarding and set accelerating admixtures, respectively. Validating field tests demonstrated that good predictions of concrete initial setting times can be accomplished with 2% error, when accurate field weather forecasts are available. This work also demonstrates the use of the prediction relations, with the objective of achieving uniform thermo-mechanical properties of a pouring sequence in the field.

A comparative study of inter-abutment distance of dies made from full arch dual-arch impression trays with those made from full arch stock trays: An in vitro study

The dual-arch impression technique is convenient in that it makes the required maxillary and mandibular impressions, as well as the inter-occlusal record in one procedure. The accuracy of inter-abutment distance in dies fabricated from dual-arch impression technique remains in question because there is little information available in the literature. This study was conducted to evaluate the accuracy of inter-abutment distance in dies obtained from full arch dual-arch trays with those obtained from full arch stock metal trays. The metal dual-arch trays showed better accuracy followed by the plastic dual-arch and stock dentulous trays, respectively, though statistically insignificant. The pouring sequence did not have any effect on the inter-abutment distance statistically, though pouring the non-working side of the dual-arch impression first showed better accuracy.

Behavior of curved steel trapezoidal box-girders during construction

In recent years, steel, trapezoidal box-girders for curved highway interchanges have been used extensively. For these structural systems, the majority of the steel girder cross-sectional stresses occur during the concrete pouring sequence. This paper describes a comprehensive study on the behavior of curved girders during construction. Data collected for the current research shows significant differences between the measured and predicted quantities, particularly for later pours. An overview of the steel–concrete interface behavior at early concrete ages and the development of an analytical tool to predict the response of systems with semi-cured concrete are given. Field monitoring of two bridges during construction is presented. The measured results were compared to analytical predictions obtained using software developed specifically under this research to address deficiencies with currently available analytical tools. Accounting for strength and stiffness gained throughout the construction process, the developed software is able to accurately capture girder stresses during construction.

Effect of Construction Loads and Vibrations on New Concrete Bridge Decks

This paper presents an investigation on the effects of construction loads and vibrations on typical newly poured reinforced concrete bridge decks. The main objective of this paper was to perform dynamic finite-element analyses of concrete bridge decks under construction loads and vibrations. Two types of bridges were modeled by effectively simulating the loads encountered during construction. Separate analyses were performed to simulate one truck as well as two side-by-side trucks. Additional analyses were performed to simulate the loads during construction and pouring sequence. The loads imposed by concrete mixer trucks, including the full concrete load and the load imposed by a trailer unit carrying the pump, were taken into consideration during the modeling of the bridges. The results obtained consisted of vibration modes and frequencies for each structure in addition to top and bottom stresses in each principal direction. A separate analysis was performed that took into account the sequence of pour to...

Analysis and diagnostic testing of a bridge

The paper deals with analytical and experimental study to determine the cause of transverse crack patterns on two parallel seven-span haunched steel-girder bridges. Major cracks are concentrated between the beginning and the middle of the third span. The crack patterns are symmetric with respect to the fourth span and can be found on both bridges. Diagnostic tests were performed with crawling-speed and high-speed trucks. The measured distribution factors are consistently more uniform than code-specified values and the impact factors are smaller than specified values. Tests on concrete cores indicated that the water/cement ratio is higher than code specified ratio and that the strength of concrete is greater than specified. Three-dimensional finite-element analysis indicated that stresses in the slab due to live load do not match with existing crack patterns. However, the analysis of the concrete pouring sequence showed that maximum concrete stresses are large and the locations correspond to those of the most severe slab cracking. Therefore, it is concluded that the bridge deck slab cracks resulted primarily from the deck pouring sequence, combined with concrete shrinkage. Since the primary causes of cracks are not active anymore, an epoxy injection method has been recommended to seal cracks.

Experimental Study of the Transition from Constrained to Unconstrained Growth during Directional Solidification.

Temperature measurements are carried out in 99.99 wt% aluminium and aluminium–silicon alloys. The experimental apparatus was initially built for the study of microporosity formation in aluminium alloys.1) The construction is designed to obtain upward directional solidification by limiting lateral heat flow during cooling and suppressing fluid flow induced by the pouring sequence. Cooling occurs from the top part of the ingot, leading to the formation of a surface dendrite layer. In the 99.99 wt% aluminium, very few equiaxed grains sink down from the surface dendrite layer into the liquid. The density of the equiaxed dendritic grains is too low to block the columnar cellular front. Cooling curves show that, once superheat disappears ( i.e., when no substantial thermal gradient remains in the liquid), the liquid is kept at an almost constant temperature during the growth of the columnar front and a small negative thermal gradient forms in the liquid ahead of the growing columnar front. It is concluded that the liquid is reheated by the growing columnar front. In the case of the aluminium–silicon alloys, a columnar-to-equiaxed transition (CET) is observed at almost two-thirds of the ingot length. The columnar length is found to increase slightly with decreasing the solute content. Recalescence is measured in a fully equiaxed region, while cooling rate, recorded by the thermocouple located just above the CET, remains negative.

Behaviour of Composite Bridges during Construction

The behaviour of steel-concrete composite bridges is influenced by time-dependent effects in the concrete deck slab that can affect the durability of such structures. A detailed study of the causes of transverse cracking in concrete slabs of composite bridges has been carried out to understand better the origin of tensile stresses in the slab. In situ measurements and laboratory tests have enabled the behaviour of concrete slabs to be observed from the moment they were placed. The results demonstrate the important influence of concrete hydration and the pouring sequence on the tensile stresses in the slab. It is shown that for typical bridges the most critical tensile stresses in the slab are induced during construction. Methods for limiting the effects of hydration have been tested and the results compared with those of numerical simulations. A criterion for evaluating the probability of crack formation in young concrete has been established based on these simulations.

Planning and Construction of An Ellipsoidal Dome

Description of 140 ft diam ellipsoidal dome containing 1,500 cu yd of concrete. Construction planning to meet schedule. Timber forms are supported on 44 trusses with two conditions of support. Temporary roof is without center support, and spanning across perimeter wall. Concrete form with center support, and sliding on wall. Adjustable pipe jacks maintain a construction tolerance of ± 1/2 in. from theoretical. Analysis of rotational stability of compression ring. Truss erection, and concrete pouring sequence. Form stripping, and truss dismantling sequences. Removal of forms and trusses, through opening in dome, for subsequent re-use. Steel plug is bolted into position. Two of the four committed domes are under construction.