scholarly journals Long-Term Behaviour of Precast Concrete Deck Using Longitudinal Prestressed Tendons in Composite I-Girder Bridges

2018 ◽  
Vol 8 (12) ◽  
pp. 2598 ◽  
Author(s):  
Haiying Ma ◽  
Xuefei Shi ◽  
Yin Zhang
Keyword(s):  
Tensile Stress ◽  
Compressive Stress ◽  
Precast Concrete ◽  
Concrete Strength ◽  
Steel Girders ◽  
Concrete Creep ◽  
Compressive Stresses ◽  
Girder Bridge ◽  
Concrete Deck

Twin-I girder bridge systems composite with precast concrete deck have advantages including construction simplification and improved concrete strength compared with traditional multi-I girder bridge systems with cast-in-place concrete deck. But the cracking is still a big issue at interior support for continuous span bridges using twin-I girders. To reduce cracks occurrence in the hogging regions subject to negative moments and to guarantee the durability of bridges, the most essential way is to reduce the tensile stress of concrete deck within the hogging regions. In this paper, the prestressed tendons are arranged to prestress the precast concrete deck before it is connected with the steel girders. In this way, the initial compressive stress induced by the prestressed tendons in the concrete deck within the hogging region is much higher than that in regular concrete deck without prestressed tendons. A finite element analysis is developed to study the long-term behaviour of prestressed concrete deck for a twin-I girder bridge. The results show that the prestressed tendons induce large compressive stresses in the concrete deck but the compressive stresses are reduced due to concrete creep. The final compressive stresses in the concrete deck are about half of the initial compressive stresses. Additionally, parametric study is conducted to find the effect to the long-term behaviour of concrete deck including girder depth, deck size, prestressing stress and additional imposed load. The results show that the prestressing compressive stress in precast concrete deck is transferred to steel girders due to concrete creep. The prestressed forces transfer between the concrete deck and steel girder cause the loss of compressive stresses in precast concrete deck. The prestressed tendons can introduce some compressive stress in the concrete deck to overcome the tensile stress induced by the live load but the force transfer due to concrete creep needs be considered. The concrete creep makes the compressive stress loss and the force redistribution in the hogging regions, which should be considered in the design the twin-I girder bridge composite with prestressed precast concrete deck.

Design and Construction of a Full-Width, Full-Depth Precast Concrete Deck Slab on Steel Girder Bridge

2005 ◽  
Vol 1907 (1) ◽  
pp. 54-66
Author(s):  
Alex Harrison ◽  
N. David LeBlanc
Keyword(s):  
Bridge Deck ◽  
Steel Plate ◽  
Precast Concrete ◽  
Full Width ◽  
Steel Girders ◽  
Deck Panels ◽  
Girder Bridge ◽  
Term Creep ◽  
Concrete Deck

The West Sandusky Street Bridge over I-75 in Findlay, Ohio, consisted of a single 170-ft-span hybrid steel plate girder bridge with a concrete deck. To minimize closure times on West Sandusky Street and reduce traffic delays on I-75 during the bridge's replacement, full-width, full-depth precast concrete deck panels were proposed for the bridge deck construction. The precast deck panels are posttensioned both longitudinally and transversely to minimize cracking and improve durability and are constructed with shear stud pockets to allow for the installation of shear studs after erection and posttensioning. During detail design, a finite element analysis of the bridge deck was carried out to determine the required level of prestress in the deck. A time-dependent analysis was subsequently completed to determine the long-term creep effects and posttensioning losses, including the effects of restraint from the steel girders. A sensitivity analysis determined the optimum curing time required before stressing the longitudinal posttensioning tendons and grouting the shear pockets. The steel plate girders were designed for the long-term creep effects due to the posttensioning of the deck, which imposed additional axial loads and moments on the steel girders. The replacement deck panels were fabricated before bridge demolition and road closure. Bridge construction was completed in fall 2004.

scholarly journals Modified mortar pad behavior in the transfer of compressive stresses

2016 ◽  
Vol 9 (3) ◽  
pp. 414-434
Author(s):  
J. D. Ditz ◽  
M. K. EL Debs ◽  
G. H. Siqueira
Keyword(s):  
Precast Concrete ◽  
Concrete Strength ◽  
Compressive Load ◽  
Stress Transfer ◽  
Compressive Stresses ◽  
Bonded Phase ◽  
Concrete Blocks ◽  
Load Tests ◽  
Styrene Butadiene ◽  
Concrete Elements

ABSTRACT This research aims to analyze the compressive stress transfer between precast concrete elements using cement mortar pads modified with polypropylene fibers, styrene-butadiene latex and heat-expanded vermiculite. The stress transfer analyses are performed interleaving a cementbearing pad between two concrete blocks, subjecting the entire specimen to different compressive load tests. The parameters analyzed in the tests are: surface roughness (using bosses on the bonded phase of different thicknesses), compressive strength with monotonic and cyclic loadings. The main results obtained in this study are: a) the presence of pad increased the strength in 24% for thicknesses of imperfections of 0.5 mm and approximately 12% for smooth faces blocks; b) gain of effectiveness of the bearing pad when the concrete strength was reduced; c) for cyclic loading, the bearing pad increased in 48% the connections strength.

Relaxing the Stud Spacing Limit for Full-Depth Precast Concrete Deck Panels Supported on Steel Girders (Phase I)

2010 ◽  
Vol 15 (5) ◽  
pp. 482-492 ◽  
Author(s):  
Sameh S. Badie ◽  
Amgad F. Morgan Girgis ◽  
Maher K. Tadros ◽  
Nghi T. Nguyen
Keyword(s):  
Phase I ◽  
Precast Concrete ◽  
Steel Girders ◽  
Deck Panels ◽  
Concrete Deck

scholarly journals The chemical additives in the prefabricated reinforced concret technology

2015 ◽  
Vol 4 ◽  
pp. 7-14
Author(s):  
Usov B.A. ◽  
Okolnikova G.E.
Keyword(s):  
Portland Cement ◽  
Precast Concrete ◽  
Concrete Strength ◽  
Heating Regime ◽  
Chemical Additives ◽  
Warm Up ◽  
Chemical Admixtures ◽  
Complex Agent ◽  
Curing Regimes

The article presents research data of concrete with chemical admixtures for precast concrete. To the additives are hardening accelerators, systems-based accelerators, plasticizers and air-entraining additives. The authors studied the effect of the addition of electrolytes (NаСl, Nа2SО4 СаСl2, Са(NO3)2), complex additives (on the basis of the electrolytes and plasticizers, air-entraining additives SPD and mikrokremnezema) on properties of concrete, strength of concrete steamed and some of its properties. By accelerating the effect of electrolyte additives studied were located in the sequence: СаСl2 > NаСl > Nа2SO4 > Са(NO3)2. It is noted that the increase of concrete strength with electrolytes increases with decreasing the duration of heating and the content of aluminates in Portland cement, which allows for 40...50% reduction in the warm-up of concrete or 5...15% of cement consumption. Complex agent (on their basis), irrespective of the Mineralogy of the cement is more efficient and reduce the cement consumption by 10...15%, superplasticizers up to 20%, but long-term modes and regardless of the type of Portland cement. The article contains a material with strength in different curing regimes, the indicators of reduction of consumption of cement and frost resistance of concrete with the introduction of air-entraining additives. Empirical formula to calculate the reduction of the duration of isothermal heating regime during heat treatment of concrete.

Internal Stress Generation in Rattan Canes

IAWA Journal ◽  
1999 ◽  
Vol 20 (1) ◽  
pp. 45-58 ◽  
Author(s):  
Willie Abasolo ◽  
Masato Yoshida ◽  
Hiroyuki Yamamoto ◽  
Takashi Okuyama
Keyword(s):  
Tensile Stress ◽  
Internal Stress ◽  
Compressive Stress ◽  
Compression Wood ◽  
Lignin Content ◽  
Stress Generation ◽  
Tensile Stresses ◽  
Stress Development ◽  
The Core ◽  
Compressive Stresses

Internal stress development was investigated in rattan canes (Calamus merrillii Becc.) following the procedures used in trees. Measurements showed that longitudinal compressive stresses existed at the periphery while longitudinal tensile stresses existed at the core. Such stresses originated from the fibers. Fiber MFA was observed to be beyond 20" and the lignin content was above 30%. Considering its similarities to compression wood tracheids, it was assumed that the rattan fibers generated longitudinal compressive stress. The amount of stress varied from base to top and from periphery to core because of the variation in the proportion of fibers along these points. This is why the longitudinal compressive stress that was generated at the base was higher than at the top and high longitudinal compressive stress was developed at the periphery. As a response to this high peripheral stress, longitudinal tensile stress was induced at the core.

scholarly journals RELIABILITY OF REINFORCED CONCRETE STRUCTURES TAKING INTO ACCOUNT THE CONCRETE CREEP FACTOR

2021 ◽  
Vol 3 (6) ◽  
pp. 35-43
Author(s):  
V. Pshenichkina ◽  
B. Gricenko ◽  
A. Gluhov ◽  
Babovich Miodrag
Keyword(s):  
Reinforced Concrete ◽  
Service Life ◽  
Concrete Strength ◽  
Concrete Structures ◽  
Ambient Air ◽  
Statistical Characteristics ◽  
Reinforced Concrete Structures ◽  
Concrete Creep ◽  
Wide Range

In the process of inspection of reinforced concrete structures being in long-term service, deflections of beams and slabs beyond the standard values are often detected, which is attributable to concrete creep occurring in the case of the early dismantling of shuttering. At the same time, any visual signs of their reduced load-bearing capacity are absent. Taking into account the high degree of uncertainty of the factors influencing the long-term strains of the concrete, the safe service life of such structures can vary within a rather wide range, and its actual value can be assessed only through probabilistic methods of the reliability theory. The paper presents the results of the investigation of the influence of concrete creep caused by the early dismantling of the shuttering on the reliability of prefabricated reinforced concrete floor beams of a three-storey building. The data obtained through the instrumental verification of the mechanical characteristics of the beam materials and their deformed state were used for design modelling. The authors carried out the probabilistic creep analysis of the beam through the method of statistical modelling taking into account the variability of concrete strength for various values of the relative humidity of the ambient air and the age of concrete at the moment of the load application. The statistical characteristics of the stress-strain modulus and the beam deflection values with various levels of probability were obtained. Due to con-crete creep, the safety analysis showed a 2,4 times reduction in the beam reliability index at the service life of a structure of 70 years.

Wisconsin’s Use of Full-Depth Precast Concrete Deck Panels Keeps Interstate 90 Open to Traffic

PCI Journal ◽  
2007 ◽  
Vol 52 (1) ◽  
pp. 16-30
Author(s):  
James W. Carter ◽  
Tom Pilgrim ◽  
Finn K. Hubbard ◽  
Tim Poehnelt ◽  
Michael Oliva
Keyword(s):  
Precast Concrete ◽  
Deck Panels ◽  
Concrete Deck

"New Donors" in Czochralski Grown Silicon Annealed at T≥ 600°C under Compressive Stress

2005 ◽  
Vol 108-109 ◽  
pp. 181-186 ◽  
Author(s):  
Valentin V. Emtsev ◽  
Boris A. Andreev ◽  
Gagik A. Oganesyan ◽  
D.I. Kryzhkov ◽  
Andrzej Misiuk ◽  
...  
Keyword(s):  
Mechanical Stress ◽  
Compressive Stress ◽  
Reference Temperature ◽  
Enhancement Effect ◽  
Shallow Acceptor ◽  
Thermal Donor ◽  
Compressive Stresses ◽  
Heat Treated ◽  
Donor Formation ◽  
New Donors

Effects of compressive stress on oxygen agglomeration processes in Czochralski grown silicon heat treated at T= 450OC, used as a reference temperature, and T= 600OC to 800OC are investigated in some detail. Compressive stresses of about P= 1 GPa lead to enhanced formation of Thermal Double Donors in materials annealed over a temperature range of T= 450OC – 600OC. It has been shown that the formation of thermal donors at T= 450OC under normal conditions and compressive stress is accompanied with loss of substitutional boron. In contrast, the concentration of the shallow acceptor states of substitutional boron in silicon annealed under stress at T≥ 600OC remains constant. An enhancement effect of thermal donor formation is gradually weakened at T≥ 700OC. The oxygen diffusivity sensitive to mechanical stress is believed to be responsible for the observed effects in heat-treated silicon.

scholarly journals Influence of Rapid Heat Treatment on the Shrinkage and Strength of High-Performance Concrete

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4102
Author(s):  
Jan Stindt ◽  
Patrick Forman ◽  
Peter Mark
Keyword(s):  
Heat Treatment ◽  
High Performance ◽  
High Performance Concrete ◽  
Treatment Time ◽  
Precast Concrete ◽  
Concrete Strength ◽  
Shrinkage Strain ◽  
Temperature Treatment ◽  
Production Flow ◽  
Steel Fibres

Resource-efficient precast concrete elements can be produced using high-performance concrete (HPC). A heat treatment accelerates hardening and thus enables early stripping. To minimise damages to the concrete structure, treatment time and temperature are regulated. This leads to temperature treatment times of more than 24 h, what seems too long for quick serial production (flow production) of HPC. To overcome this shortcoming and to accelerate production speed, the heat treatment is started here immediately after concreting. This in turn influences the shrinkage behaviour and the concrete strength. Therefore, shrinkage is investigated on prisms made from HPC with and without steel fibres, as well as on short beams with reinforcement ratios of 1.8% and 3.1%. Furthermore, the flexural and compressive strengths of the prisms are measured directly after heating and later on after 28 d. The specimens are heat-treated between 1 and 24 h at 80 °C and a relative humidity of 60%. Specimens without heating serve for reference. The results show that the shrinkage strain is pronouncedly reduced with increasing temperature duration and rebar ratio. Moreover, the compressive and flexural strength decrease with decreasing temperature duration, whereby the loss of strength can be compensated by adding steel fibres.

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