【摘要】：隨著國民經(jīng)濟的迅速發(fā)展,城市建設(shè)規(guī)模的日益擴展,土地供應(yīng)量日趨緊張,致使地下車庫建設(shè)與日俱增。地下車庫設(shè)計的現(xiàn)狀是:車庫單體面積日益增大,尤其是車庫長度不斷擴大,地下室的平面尺寸越來越大,有些甚至達到或超過200～300米,設(shè)計超長車庫時勢必會面臨很多難題。目前,結(jié)構(gòu)師設(shè)計大型車庫時主要考慮的是正常使用工況,對施工工況缺少關(guān)注。設(shè)計人員常認為頂板上有覆土,季節(jié)溫差很小,如已按規(guī)范要求設(shè)置溫度后澆帶則無需計算溫度應(yīng)力。但實際情況是,施工方常將地下室頂板作為施工場地,或認為設(shè)計設(shè)置后澆帶已經(jīng)考慮了溫度應(yīng)力,即使在溫度后澆帶封閉之后也未及時覆土,而導(dǎo)致地下室頂板、外墻大面積開裂,甚者,突遇強降雨,導(dǎo)致地下室局部抗浮破壞。故設(shè)計文件應(yīng)對施工覆土的時間以及施工期間地下水位控制提出明確要求,以使現(xiàn)場情況與設(shè)計成果相符。雖然平板式筏板基礎(chǔ)在純地下室工程中的應(yīng)用已經(jīng)很廣泛,但是,在工程設(shè)計中存在著柱墩尺寸偏大,筏板厚度偏厚,選取的基床系數(shù)與地基條件、筏板的實際受力情況不相符,特別是柱墩的配筋偏大等設(shè)計不合理、不經(jīng)濟的現(xiàn)象�；谝陨锨闆r本文通過計算實例,對影響平板式筏板基礎(chǔ)內(nèi)力的主要因素進行了詳細的分析,以找出其中的變化規(guī)律。本文主要針對四個關(guān)鍵技術(shù)問題進行闡述:包括(1)大型地下室頂板的溫度應(yīng)力及裂縫分布;(2)地下室外墻的溫度應(yīng)力及裂縫分布;(3)純地下室筏板基礎(chǔ)的優(yōu)化設(shè)計;(4)地下室未覆土前,按空腹桁架模型及整體有限元分析地下室的局部抗浮問題。取得的主要成果如下:1.討論了超長混凝土結(jié)構(gòu)間接作用的構(gòu)成及相應(yīng)的計算方法,對混凝土結(jié)構(gòu)的間接作用和荷載作用進行了比較。在超長混凝土結(jié)構(gòu)工程設(shè)計中,將混凝土收縮等效為溫差,考慮徐變作用為結(jié)構(gòu)彈性解乘以近似0.3的折減系數(shù),是一種實用有效的方法。2.超長混凝土結(jié)構(gòu)間接作用下的內(nèi)力分析需要考慮混凝土開裂后的影響,討論了超長混凝土結(jié)構(gòu)在間接作用下的內(nèi)力分析方法,并對南通某安置房住宅項目的地下室頂板、外墻在間接作用下的內(nèi)力進行了分析。超長地下室頂板周邊有地下室外墻約束的部位,樓板的面外剛度對溫度應(yīng)力的影響不容忽視,需考慮降溫和升溫兩種工況,并對樓板分別采用考慮及不考慮面外剛度兩種假定進行分析。3.設(shè)計超長混凝土結(jié)構(gòu)時,不僅要考慮使用工況下的荷載,還應(yīng)適當(dāng)考慮在施工工況下可能出現(xiàn)的不利情況,如:因未及時覆土而引起的較大溫度應(yīng)力,甚至地下室抗浮事故。邊跨梁端的抗彎配筋和邊跨柱頂?shù)目箯�、抗剪配筋一般由施工工況控制,設(shè)計時需對相關(guān)部位進行加強。4.采用有限元軟件進行分析,以確定不同參數(shù)(基床系數(shù)、柱墩厚度、筏板厚度、柱墩平面尺寸等)對純地下室筏板基礎(chǔ)受力性能的影響。在滿足抗?jié)B、抗浮要求的前提下,合理地選取底板的厚度,并優(yōu)化底板配筋以減少底板裂縫。5.計算地下室局部抗浮時,整體分析比等代框架簡化計算內(nèi)力有著明顯的優(yōu)勢,整體分析結(jié)果與實測值吻合得較好;而在等代框架計算過程中,荷載傳遞和結(jié)構(gòu)剛度經(jīng)常要采用簡化措施,難以考慮垂直方向框架的剛度貢獻,并且,取一榀框架計算時,其計算跨度也需要通過取平均值簡化,分析結(jié)果的誤差較大。6.因局部抗浮破壞的柱的裂縫特征和破壞形態(tài)與在足夠大水平荷載作用下,多層框架結(jié)構(gòu)中框架梁產(chǎn)生的裂縫特征和破壞形態(tài)十分相似,其原因:如果把地下車庫底板、頂板看成"框架柱",把地下車庫柱看成"框架梁",因"框架柱"截面和剛度較大,"框架梁"截面和剛度較弱,在"水平荷載"作用下,必然"框架梁"即實際地下車庫柱首先開裂,而且在足夠大"水平荷載作用"下,其破壞較嚴重。
[Abstract]:With the rapid development of the national economy and the expansion of the scale of urban construction, the supply of land is becoming increasingly tense, resulting in the construction of underground garage increasing day by day. At present, the main consideration of structural engineers in designing large-scale garages is the normal working conditions, and the lack of attention to the construction conditions. In other words, the construction side often takes the basement roof as the construction site, or considers that the temperature stress has been taken into account in the design and setting of the post-pouring zone, even after the closure of the post-pouring zone, the soil is not covered in time, which leads to the basement roof, external wall cracking in a large area, or even sudden heavy rainfall, leading to the local anti-floating damage of the basement. The time of overlying soil and the control of groundwater level during construction are clearly required in order to make the field situation coincide with the design results. Although flat raft foundation has been widely used in pure basement engineering, there are some problems in engineering design, such as large pier size, thick raft thickness, selected foundation coefficient and foundation conditions. The actual force of raft is not consistent, especially the unreasonable and uneconomical design of column pier. Based on the above situation, this paper analyzes the main factors affecting the internal force of raft foundation in detail by calculating examples, and finds out the changing rules of the raft foundation. This paper expounds the following aspects: (1) temperature stress and crack distribution of the roof of large basement; (2) temperature stress and crack distribution of basement exterior wall; (3) optimization design of pure basement raft foundation; (4) local anti-floating problem of basement is analyzed by hollow truss model and integral finite element method before the basement is covered with soil. The composition of indirect action of super-long concrete structure and the corresponding calculation method are discussed. The indirect action and load action of concrete structure are compared. In the design of super-long concrete structure, the shrinkage of concrete is equivalent to the temperature difference, and the elastic solution of structure is taken into account the creep action and multiplied by the reduction coefficient of approximate 0.3. 2. The internal force analysis of super-long concrete structure under indirect action needs to consider the effect of concrete cracking. The internal force analysis method of super-long concrete structure under indirect action is discussed, and the internal force of basement roof and external wall under indirect action is analyzed. The influence of out-of-plane stiffness on temperature stress should not be neglected because there are basement outer wall restraints around the slab. The two assumptions of cooling and heating should be taken into account, and the two assumptions of out-of-plane stiffness should be considered respectively. 3. When designing super-long concrete structures, not only the load under service conditions should be considered, but also appropriate. When considering the disadvantage that may occur under the construction conditions, such as: large temperature stress caused by not covering the soil in time, even the basement anti-floating accident. In order to determine the influence of different parameters (bed coefficient, pier thickness, raft thickness, pier plane size, etc.) on the mechanical properties of pure basement raft foundation, the thickness of the bottom plate is reasonably selected and the reinforcement of the bottom plate is optimized to reduce the cracks in the floor. 5. Compared with the equivalent frame, the simplified calculation of internal forces has obvious advantages, and the overall analysis results are in good agreement with the measured values; while in the process of equivalent frame calculation, load transfer and structural stiffness often adopt simplified measures, it is difficult to consider the stiffness contribution of vertical frame, and the calculation span of one frame also needs to pass. 6. The crack characteristics and failure modes of columns with local anti-floating failure are very similar to those of frame beams in multi-storey frame structures under sufficiently large horizontal loads. The reason is that if the floor and roof of underground garage are regarded as "frame columns", the underground garage is regarded as "frame columns". Columns are considered as "frame beams". Because the section and stiffness of "frame columns" are larger, the section and stiffness of "frame beams" are weaker. Under the action of "horizontal load", the "frame beams" are bound to crack first in the actual underground garage columns, and the failure is more serious under the action of "horizontal load".
【學(xué)位授予單位】：東南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU926

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