Numerical Simulation of Thermal Field in Mass Concrete With Pipe Water Cooling

Water pipe cooling is mainly used to control temperature in the construction of mass concrete structures. It is important to reveal how to accurately stimulate the temperature field of mass concrete under action of this water pipe cooling. This paper presents a new method for this purpose. In this method, the contact surface of the water pipe and the concrete is used as the heat dissipation surface into the control equation and the composite Multiquadrics radial basis function (MQ-RBF) and low-order linear polynomial combination are used to discrete the spatial domain. The heat dissipation surface of the water pipe is included in the boundary conditions so that there is no need to build the refined water pipe modeling. This new method not only reduces the calculation cost but also ensures calculation accuracy. Through four calculation examples, this paper show that the algorithm has advantages in the numerical simulation of the concrete temperature field with water pipe cooling.

Effect of Water Pipe Cooling on Thermal Stress of FuYang River Aqueduct Structure

In order to analyze the influence rule of water pipe cooling on the temperature field and thermal stress of large aqueduct structure, the finite element analysis model for FuYang River Aqueduct structure was established. The temperature field and thermal stress of the aqueduct structure were calculated. The following two cases were considered: structure with or without water pipe cooling, as well as the different beginning pouring months (May, June and July). The hydration-degree-based calculation methods of temperature and stress of concrete were adopted, and the high precision discrete simulation method of water pipe was used. The calculation results show that embedding the cooling pipe in concrete can effectively reduce the temperature difference between inside and outside of the early concrete and thermal stress, and is therefore effective to prevent concrete cracks. High accuracy of simulation and analysis can make people basically figure out the specific mechanism of concrete cracking and main factors even before construction, and determine accurately the structure crack location and the developing tendency.

Temperature Control and Anti-Cracking Measures for a High-Performance Concrete Aqueduct

To solve the problem of cracks developing on thin-walled concrete structures during construction, the authors expound on the causes of cracks and the crack mechanism. The difference between external and internal temperatures, basic temperature difference and constraints are the main reasons of crack development on thin-walled concrete structures. Measures such as optimizing concrete mixing ratio, improving construction technology, and reducing temperature difference can prevent thin-walled concrete structures from cracking. Moreover, water-pipe cooling technology commonly used in mass concrete can be applied to thin-walled concrete structures to reduce temperature difference. This method is undoubtedly a breakthrough in anti-cracking technology for thin-walled concrete structures, particularly for thin-walled high-performance concrete structures. In addition, a three-dimensional finite element method is adopted to simulate the calculation of temperature control and anti-cracking effects f. Results show the apparent temperature controlling effect of water-pipe cooling for thin-walled concrete structures.

Study on Concrete's Temperature Control Measures for Inverted-Siphons during Construction Period

In view of the problem of concrete cracks during construction, the good effect of cracks prevention can be achieved if the timely and reasonable scheme of temperature control is selected. Under the 3-D FEM including water-pipe cooling is adopted to simulate the stresses field of Inverted siphon during construction. Through analyzing the time-space variation law, it is fund that cracks easily appear. In the part of the middle line of the South-North Water Transfer Project£¬the quality of concrete surface of III section in Jiaozuo has been improved obviously through the method of external insulation board.

Influence of Water Pipe Cooling on Thermal Stresses in Mass Concrete

Temperature field and stress field of a concrete slab in a ship lock chamber are calculated, considering the influence of layered casting. And the influence of water pipe cooling at the early period of constructing, and at the period after constructing, sunshade, pre-cooled concrete etc are taken into account. The expression of finite difference method considering the effect of water pipe cooling is deducted for temperature analysis. Thermal stress calculation results show that the water pipe cooling at the mid-late period is a comparatively effective measure to reduce tensile stress of chamber mass concrete. And an effective temperature control measure is recommended in summer casting, which is that: sunshade + pre-cooled concrete + water pipe cooling (both at early period and at mid-late period). Mid-late period water pipe cooling must last for three months. Combined with other temperature control measures such as summer cover maintenance, winter cover preservation etc, the concrete cracks can be reduced, and the occurrence of large area run through cracks can be avoided.

Cracking Mechanism of RCC Dam Surface and Prevention Method

Using low placement temperature and proper water pipe cooling water, the cracks are rarely appears in the interior of the dam, but the surface of the dam is prone to cracking. During the construction, the surface of the dam may be wet due to several factors such as creep, maintenance and so on, so the effect of the heat preservation is always been over-estimated. For those concrete blocks constructed in cold season, without proper heat preservation, the cracks are easy to appear soon after construction. For those concrete blocks constructed in hot period, under the influence of air temperature, the temperature of those concrete within about 5.0m of the dam surface are hard to control. So the key point to prevent the dam surface constructed in cold period is to take heat preservation measure suiting the on-the-spot situation. And for those dam blocks constructed in hot period, water cure on the surface of the dam can greatly reduce the risk of dam surface cracking.

Automatic Control Model of Concrete Temperature

Most temperature control measurement methods are based on artificial work with anti-cracking during concrete construction. Automatic temperature control model proposed to implement computer control technology in concrete structural construction temperature control with anti-cracking to create an automatic concrete temperature control model. The model is based on temperature sensation technology, wireless transmission technology, water-pipe cooling technology, numerical simulation for the concrete structure of dynamic simulation and real-time monitoring. It can implement concrete inner temperature control to prevent temperature stress from producing cracks in concrete structure.