scholarly journals Comparison of Concrete Creep in Compression, Tension, and Bending under Drying Condition

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3357
Author(s):  
Seung-Gyu Kim ◽  
Yeong-Seong Park ◽  
Yong-Hak Lee
Keyword(s):  
Creep Strain ◽  
Concrete Beams ◽  
Shrinkage Strain ◽  
Tensile Creep ◽  
Bottom Surface ◽  
Atmospheric Conditions ◽  
Creep Experiment ◽  
Beam Depth ◽  
Creep And Shrinkage ◽  
Creep Strains

Three types of creep experiments of compression, tension, and bending were implemented to identify quantitative relations among the three types of creep under drying atmospheric conditions. In case of the bending creep experiment, two types of unreinforced concrete beams with similar dimensions were cast for use in the beam creep and shrinkage tests. The variations in the shrinkage strain within the beam depth were measured to evaluate the effect of the shrinkage variations on the bending creep strain. The beam creep strain measured within the beam depth was composed of uniform and skewed parts. The skewed parts of the creep strain were found to be dominant whereas the uniform parts were small enough to be neglected in the bending creep evaluation. This indicated that the compressive bending creep at the top surface was close to the tensile bending creep at the bottom surface. The ratios of tensile and bending creep strains to compressive creep strain were approximately 2.9 and 2.3, respectively, and the ratio of bending creep strain to tensile creep strain was approximately 0.8. Particular attention is laid on the close agreement between tensile and compressive bending creep strains even if the creep in tension is 2.9 times larger than the creep strain in compression.

Influence of changing environment conditions on the development of shrinkage strain and the expansion coefficient of large concrete specimens

2019 ◽  
Author(s):  
Dominik Suza ◽  
Johann Kollegger ◽  
Harald S. Müller
Keyword(s):  
Shrinkage Strain ◽  
Theoretical Models ◽  
Test Results ◽  
Current Standard ◽  
Operating Life ◽  
Changing Environment ◽  
Temperature And Humidity ◽  
Bridge Structures ◽  
Standard Models ◽  
Creep And Shrinkage

<p>The standard creep and shrinkage strain measurements of concrete are usually conducted in a laboratory with constant temperature and humidity with a low variation. The creep and shrinkage measurements are conducted over a few months with the expectation that small concrete specimens can sufficiently describe the evolution of the rheology effects on a large multi-span bridge in the course of its operating life.</p><p>The monitoring of real bridge structures shows the actual progression of the deflections and concrete strains. Unfortunately the evaluation and interpretation of the measured values is complicated. The idea of the scientific Creep &amp; Shrinkage project was to combine the two described situations (laboratory experiments and monitoring of real bridge structures) creating an experimental setup which would benefit from the advantages of both approaches.</p><p>In order to achieve conformity of the measured test results with those of theoretical models (MC 2010, EC) it was necessary to upgrade the current models to include the effects of changing temperature and humidity. Within this paper the upgrade of the current standard models to include changing environment conditions will be elaborated, in addition to an explanation of the method used to separate shrinkage strains from the temperature strains from the measured data. The measured concrete expansion coefficients will also be discussed.</p>

Analysis of Crack Patterns of 500MPa Reinforced Concrete Beams

2013 ◽  
Vol 790 ◽  
pp. 120-124
Author(s):  
Zhi Hua Li ◽  
Xiao Zu Su
Keyword(s):  
Static Loading ◽  
Crack Width ◽  
Concrete Beams ◽  
Concrete Cover ◽  
Reinforced Concrete Beams ◽  
Crack Control ◽  
Crack Patterns ◽  
Beam Depth ◽  
Steel Bars ◽  
Constant Moment

Fourting concrete beams reinforced with 500MPa longitudinal steel bars, of which 6 with skin reinforcement and 8 without skin reinforcement, were tested under two-point symmetrical concentrated static loading to investigate their crack patterns. Crack distributions in constant moment region of beams are compared. The propagation of side cracks along the beam depth is obtained. The results of this study indicate that the concrete cover of longitudinal tensile steel bars and the spacing of skin reinforcement has significant effect on crack distributions; substantial crack control in beams can be achieved if the spacing of skin reinforcement is limited to certain critical values. The curve of d-w(d is the distance between observation points of side cracks and tension face of beams, w refers to crack width at observation points) is approximately characterized by a zig-zag shape and concave-left near longitudinal tensile steel bars.

Connections between Simply Supported Concrete Beams Made Continuous

2005 ◽  
Vol 1928 (1) ◽  
pp. 126-133
Author(s):  
Amy Dimmerling ◽  
Richard A. Miller ◽  
Reid Castrodale ◽  
Amir Mirmiran ◽  
Makarand Hastak ◽  
...  
Keyword(s):  
Concrete Beams ◽  
Heat Of Hydration ◽  
Moment Connections ◽  
Moment Capacity ◽  
Moment Connection ◽  
Differential Shrinkage ◽  
Negative Moment ◽  
Live Loads ◽  
Creep And Shrinkage ◽  
Sufficient Strength

Precast bridge girders can be made continuous for live loads with the provision of a moment connection over the supports. NCHRP Project 12–53 examined methods for making this type of moment connection. This is usually done by placing negative moment reinforcement in a cast-in-place deck over the support and by placing a diaphragm between the girder ends. To counteract positive moments caused by creep and shrinkage, positive moment connections are often provided at the girder ends. An experimental study of the strength of six different positive moment details, involving either extended strand or extended bar, was conducted. The results showed that all details had sufficient strength. Details using additional stirrups in the diaphragm were found to have increased ductility, and the use of horizontal web bars increased capacity. Two full-size specimens were tested to determine the level of continuity after cracking occurs at the joints. One of these specimens was also monitored for several months to determine the effects of creep, shrinkage, and temperature on the connections. It was found that expansion and contraction of the deck caused by heat of hydration and changes in ambient temperature greatly affected the system. However, an anticipated formation of negative moment caused by differential shrinkage did not occur. Even when the positive moment connection was near failure, the system maintained 70% continuity even when cracked. The system was also found to have adequate negative moment capacity.

Failure analysis of coated galvanized steel panels

2017 ◽  
Vol 64 (4) ◽  
pp. 424-431
Author(s):  
Anwar Ul-Hamid ◽  
Huseyin Saricimen ◽  
Abdul Quddus ◽  
Luai M. Al-Hems
Keyword(s):  
Light Microscopy ◽  
Failure Analysis ◽  
Metal Sheet ◽  
Galvanized Steel ◽  
Bottom Surface ◽  
Atmospheric Conditions ◽  
Content Type ◽  
X Ray ◽  
Cause Of Failure ◽  
Steel Panels

Purpose The purpose of this paper was to determine the mode and cause of failure of polyester-coated galvanized corrugated steel sheets that exhibited degradation of the coating after seven months into service. Design/methodology/approach Visual inspection and light microscopy revealed the extent of damage exhibited by the panels. Standard metallographic techniques were used to prepare samples obtained from both unused and failed sections. Light microscopy, scanning electron microscopy combined with energy dispersive x-ray spectroscopy and x-ray diffraction techniques were used to study the surface morphology, microstructural features, elemental composition and structure of the samples. Findings The failure occurred in the form of delamination and blistering of coated layer. Presence of solar radiation, humidity and water retention resulted in loss of adhesion, leading to coating delamination and flaking especially at the top surface. The coating at the bottom surface of the panels showed evidence of blistering caused by water vapor differential that existed between the environment and the coating because of prolonged (four months) wet conditions that existed at the manufacturer’s site during storage. Practical implications It is recommended that the coated panels are stored in covered area where direct exposure to atmospheric conditions can be prevented. If open storage is unavoidable, then the use of tarpaulin or plastic sheet as covering and vapor-phase inhibitors was recommended. Originality/value This paper provides an account of failure analysis of metal sheet panels. It identifies the mode and cause of failure and also provides recommendations to avoid such occurrences in the future. The information contained in this paper is useful for plant engineers and project managers working in the metal sheet industry.

Shrinkage tests of two full-scale composite trusses

1992 ◽  
Vol 19 (2) ◽  
pp. 296-309 ◽  
Author(s):  
D. J. Laurie Kennedy ◽  
Anita Brattland
Keyword(s):  
Concrete Beams ◽  
Concrete Slab ◽  
Shrinkage Strain ◽  
Steel Beam ◽  
Restrained Shrinkage ◽  
Test Results ◽  
Linear Strain ◽  
Shrinkage Behaviour ◽  
Composite Section ◽  
Composite Steel

The shrinkage behaviour of two composite trusses with a span of 11.5 m was studied. Shrinkage measurements to determine the effects of slab shrinkage on truss deflections and member strains were recorded over periods of 65 and 85 days. A method is developed to compute shrinkage deflections, based on equilibrium of the shrinkage-induced forces at midspan, which gives excellent agreement with the test results. This method assumes a linear strain distribution through the depth and is based on the free shrinkage strain of the concrete and the average stress–strain characteristics of the concrete in tension under restrained shrinkage conditions as it drys, creeps, and eventually may crack as it is gradually loaded from the green state. The method is extended to composite steel-beam concrete-slab members. It is equivalent to Branson's "composite section method" provided that the correct values for the shrinkage strain and the effective modulus of elasticity of the concrete in tension are used in the latter. Key words: behaviour, composite steel–concrete beams, trusses, shrinkage deflections.

Estimating on Creep Strain for Ready-Mixed Concrete during Shrinkage

2013 ◽  
Vol 357-360 ◽  
pp. 684-688
Author(s):  
Liang Li Xiao ◽  
Ming Yang Pan ◽  
Meng Chen
Keyword(s):  
Experimental Data ◽  
Reinforced Concrete ◽  
Creep Strain ◽  
Equilibrium Condition ◽  
Concrete Structures ◽  
Plain Concrete ◽  
Shrinkage Strain ◽  
Important Data ◽  
Experimental Part ◽  
Ready Mixed Concrete

This paper presents the development of formulas to estimate the creep strain of the reinforced concrete specimens. The experimental part of the work focused on the dispersion of shrinkage strain between reinforced concrete and plain concrete specimens, as well as the equilibrium condition between concrete tension and reinforcement compression. Based upon the experimental data and development formula, the creep strain and concrete age curves of the reinforced concrete specimens are drawn. Moreover, the characteristics of the creep strain are analyzed in detail. The creep strain formula can provide the important data and theoretic basis to “the code for design of concrete structures”（GB50010－2010）.

scholarly journals Use of Fiber Brag Gating Sensors in civil engineering applications

2021 ◽  
Author(s):  
Zahra Yazdizadeh
Keyword(s):  
High Performance ◽  
Civil Engineering ◽  
Prediction Models ◽  
High Performance Concrete ◽  
Shrinkage Strain ◽  
Second Phase ◽  
Engineering Applications ◽  
Fbg Sensors ◽  
Important Time ◽  
Creep And Shrinkage

This research presents an overview of development and application of Fiber Bragg Grating sensors (FBG) technology in civil engineering applications. The primary focus of this research is the use of FBGs to investigate two most important time-dependent properties of concrete namely: creep strain and shrinkage strain. The first phase of this investigation is focused on using FBG sensors to measure the concrete strains in unreinforced concrete beams and cylinders to determine modulus of elasticity, the modulus of rapture and fracture energy of concrete. The second phase of this research is designed to investigate the creep and shrinkage using FBG sensors. Normal strength concrete (NC), High performance concrete (HPC) and ultra-high performance (UHPC) specimens’ are used to measure creep and shrinkage strains and to compare the values with typical prediction models. The measured creep and shrinkage strains are compared to four different models to determine which model is the most accurate.

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