Thermal stresses and temperature control of mass concrete

[...]... with age τ and (2) the impact of the creep effect of the concrete 1.3 1.3.1 The Variation of Temperature and Thermal Stress of Mass Concrete with Time The Variation of Temperature of Mass Concrete with Time Because of the large size, the variation of temperature in a mass concrete structure is shown in Figure 1.3; the placing temperature Tp is the concrete temperature just after pouring If the concrete. .. cracking of mass concrete The variation of the air temperature during a cold wave may be expressed as follows (Figure 2.5):   πðτ 2 τ 1 Þ Ta 5 T0 2 Ac sin ð2:30Þ 2Q Figure 2.5 Variation of air temperature in a cold wave Ta Ac Q τ1 τ 20 Thermal Stresses and Temperature Control of Mass Concrete where T0—the initial air temperature Ac—the maxima drop of air temperature Q—the duration of drop of air temperature. .. winter construction d Optimize the concrete mix To guarantee of the strength and fluidity of concrete, efforts should be made to save cement to reduce the adiabatic temperature rise of concrete 3 Rigorous control of the temperature of concrete Rigorous control of the concrete temperature is the most important measure to prevent crack a Reduce the placing temperature of concrete Cooling the mixing water,... concrete above foundation in cold weather d Strengthen curing and prevent shrinkage 10 1.8 Thermal Stresses and Temperature Control of Mass Concrete The Experience of the Temperature Control and Crack Prevention of Mass Concrete in the Last 30 Years 1 Enhancement of pipe cooling in the local area makes the control of the maximum tensile stress in concrete dams no longer a challenge In the past, since the... the end of heat release of cement and ends when the concrete is cooled down to a final steady temperature The thermal stress in this stage is 6 Thermal Stresses and Temperature Control of Mass Concrete caused by the cooling of the concrete and the changes of external temperature In the mid stage, the elastic modulus will change slightly with time 3 Late stage: The operation stage after the concrete. .. Thermal Stresses and Temperature Control of Mass Concrete DOI: http://dx.doi.org/10.1016/B978-0-12-407723-2.00002-6 © 2014 Tsinghua University Press Published by Elsevier Inc All rights reserved ð2:5Þ 12 Thermal Stresses and Temperature Control of Mass Concrete Figure 2.1 An elementary parallelepiped y dy dz dx qx o qx + dx x z where a 5 λ/cρ—the diffusivity of concrete λ—the conductivity of concrete. .. surface of the concrete to reduce the inside and outside temperature difference and reduce the surface temperature gradient of concrete 4 Emphasis on the preparation work before construction In the early stage of the construction, preparation work of temperature control of concrete must be emphasized, such as the installation and testing of the cooling plant and ice machine, cooling water pipe, and preparation... The thermal capacity of the insulation layers is small and may be neglected and the equivalent surface conduction of concrete surface is given by βs 5 1 1 P 5 Rs ð1=βÞ 1 ðhi =λi b1 b2 Þ ð2:23Þ Thermal Stresses and Temperature Control of Mass Concrete Ta Boundary of concrete Virtual boundary Ta Virtual boundary λ2 From λ1 Insulation layer True boundary 18 λ β λ β (a) (b) Figure 2.4 Superficial thermal. .. the concrete is cooling as shown in Figure 1.4(b) In the statically determinate structure, only self-stress will appear, but in the statically indeterminate structure, both self-stress and restraint stress will appear 1.5 Analysis of Thermal Stress of a Massive Concrete Structure 1 Analysis of temperature field of mass concrete The temperature field of mass concrete depends on the weather conditions and. .. more complex to analyze the thermal stress than the stresses caused by water, self-weight, and other external loads Introduction 3 In conclusion, the analysis of the thermal stress, the temperature control, and the measures to prevent cracking are the crucial topics in the design and construction of massive concrete structures [104À110] 1.2 The Features of Thermal Stresses in Concrete Structures Here . alt="" Thermal Stresses and Temperature Control of Mass Concrete Thermal Stresses and Temperature Control of Mass Concrete Zhu Bofang China Institute of Water Resources and Hydropower Research and. system of the theory of thermal stress and temperature control of mass concrete, including two basic theorems of creep of nonhomogeneous concrete structures, the law of variation, and the methods of. Applications of the Finite Element Method (1st ed. in 1979, 2nd ed. in 1998, 3rd ed. in 2009), Thermal Stresses and Temperature Control of Mass Concrete (1999), Thermal Stresses and Temperature Control of