【摘要】：混凝土由于其強(qiáng)度高、耐久性好,被廣泛用于各類建筑物、構(gòu)筑物。隨著工程技術(shù)的不斷發(fā)展,各種新型、異型結(jié)構(gòu)的不斷涌現(xiàn),大體積混凝土結(jié)構(gòu)的運(yùn)用越來越廣泛。但大體積混凝土塊體大,自身的導(dǎo)熱性能較差,混凝土內(nèi)部產(chǎn)生的水化熱聚集難以發(fā)散,表面散熱快,中心溫度和表面溫度的溫差會造成混凝土裂縫；另外,彈性模量、松弛系數(shù)等也會隨溫度、時間的變化而變化,所以混凝土常常會開裂。如何控制大體積混凝土開裂,一直是結(jié)構(gòu)和施工中的關(guān)鍵、難點(diǎn)。 本文在大量的實(shí)踐基礎(chǔ)上,總結(jié)了大體積混凝土的特點(diǎn)、混凝土開裂原因,并從設(shè)計(jì)和施工兩個角度,分析了控制大體積混凝土開裂的有限措施。為真實(shí)反映工程的溫度場和溫度應(yīng)力,本文采用大型有限元軟件ANSYS,模擬分析了某縣人民醫(yī)院探傷室1#墻體溫度場和溫度應(yīng)力,并得出以下結(jié)論：①一般情況下(無寒潮、氣溫驟降等情況),外界氣溫的變化對大體積混凝土溫差影響不大,但對中心溫度的影響較為顯著；②澆筑溫度越高,中心溫度達(dá)到高峰的時間越短。 避免大體積混凝土開裂的措施很多,大部分研究學(xué)者都采用埋設(shè)冷水管的溫控措施,但冷水降溫不但會使混凝土內(nèi)部受熱不均勻,而且對本工程1~#墻體的防輻射不利,結(jié)合工程特點(diǎn),1~#墻體將采用蓄水保溫法的溫控措施。 利用ANSYS仿真模擬大體積混凝土的案例很多,該類工程大部分都采用冷水管降溫法,甚少采用蓄水保溫法,將模擬分析與蓄水保溫發(fā)結(jié)合的案例則更少。本文考慮大體積混凝土的中心溫度、表面溫度、水泥水化熱、傳熱影響系數(shù)、齡期等因素,計(jì)算分析得出1~#墻體的蓄水保溫厚度為：276mm,采取蓄水保溫措施后,再用有ANSYS限元軟件來模擬大體積混凝土的溫度應(yīng)力。經(jīng)過模擬分析后,可以證實(shí)：混凝土各個點(diǎn)的應(yīng)力值基本都在容許張拉應(yīng)力之內(nèi),不會再出現(xiàn)裂縫。 除進(jìn)行溫控措施外,為能有效避免裂縫產(chǎn)生,本文將結(jié)合1~#墻體施工特點(diǎn)和工程的實(shí)際情況,從施工角度總結(jié)了大體積混凝土施工時的注意要點(diǎn),例如：坍落度、雨季施上等問題。
[Abstract]:Because of its high strength and durability, concrete is widely used in buildings and structures. With the development of engineering technology, various kinds of new types and special-shaped structures are emerging, and the application of mass concrete structures is becoming more and more extensive. However, the mass concrete block is large, its thermal conductivity is poor, the hydration heat accumulation inside the concrete is difficult to disperse, the surface heat dissipates quickly, and the temperature difference between the center temperature and the surface temperature will cause the concrete crack. In addition, the modulus of elasticity and relaxation coefficient vary with temperature and time, so concrete often crack. How to control the cracking of mass concrete is always the key and difficulty in structure and construction. Based on a large number of practices, this paper summarizes the characteristics of mass concrete and the causes of concrete cracking, and analyzes the limited measures to control the cracking of mass concrete from the two aspects of design and construction. In order to truly reflect the temperature field and the temperature stress of the project, the temperature field and the temperature stress of the wall in the flaw detection room of a county people's hospital are simulated and analyzed by using the large-scale finite element software ANSYS, and the following conclusions are drawn: 1. The change of outside temperature has little effect on the temperature difference of mass concrete, but it has a significant effect on the center temperature. 2 the higher the pouring temperature, the shorter the time for the center temperature to reach the peak. There are many measures to avoid cracking of mass concrete. Most researchers have adopted temperature control measures for laying cold water pipes. However, cooling cold water will not only make the internal heat of concrete uneven, but also be unfavorable to the radiation prevention of the 1 # wall of this project. According to the characteristics of the project, the temperature control measures of water storage and heat preservation method will be adopted in the 1 # wall. There are many cases using ANSYS simulation to simulate mass concrete. Most of these projects adopt cooling method of cold water pipe, few of them adopt water storage and heat preservation method, and there are fewer cases of combining simulation analysis with water storage and heat preservation. In this paper, the central temperature, surface temperature, cement hydration heat, heat transfer coefficient, age and other factors of mass concrete are considered. The calculation and analysis show that the thickness of water storage and heat preservation of 1 # wall is 276mm. Then the thermal stress of mass concrete is simulated by ANSYS finite element software. After simulation and analysis, it can be proved that the stress values of each point of concrete are basically within the allowable tensile stress, and there will be no further cracks. In addition to temperature control measures, in order to avoid cracks effectively, this paper will summarize the main points of attention in mass concrete construction from the point of view of construction, such as slump, combined with the construction characteristics of 1 # wall and the actual situation of the project. Rainy season, etc.
【學(xué)位授予單位】：河北工程大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2013
【分類號】：TU755.7

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