接觸爆炸作用下鋼筋混凝土柱與鋼骨鋼筋混凝土柱之行為分析與實驗

Assessment of Reinforced Concrete and Composite Steel-Concrete Columns to Resist the Effects of Suitcase Bombs

吳克強(Ke-Chiang Wu)

指導教授 ： 蔡克銓

共同指導教授 ： 李兵(Bing Li)

國立臺灣大學/工學院/土木工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.03303

摘要

近年來恐怖攻擊事件在世界各地造成無數傷亡，其中以自殺炸彈客類型的恐怖攻擊事件最難預防，因為這類型的攻擊炸彈可以輕易的藉由背包運送且安置在任何角落，尤其對於柱子所造成的破壞有可能導致漸進式倒塌的風險。背包炸彈通常不會有太大量的炸藥，範圍大約是5公斤至25公斤，但安放的位置恰當卻對結構有莫大的威脅。
在本研究中，使用有限元素分析軟體LS-DYNA來得到柱子受炸彈攻擊時之動態反應以及其殘餘軸向強度，此外有三根柱子試體在野外做接觸爆炸試驗，分別為一根鋼骨鋼筋混凝土柱及兩根鋼筋混凝土柱，接觸爆炸試驗結果將與有限元素分析結果比較驗證模型的準確性。應變速率對於分析模型的準確性有重要影響，動態增量因子被用來描述此現象。建立三根試體之有限元素模型，其分析結果與接觸爆炸試驗結果有相似的破壞輪廓。
利用驗證過的有限元素分析模型做參數研究，分析柱子殘餘軸向強度與材料強度、斷面細節以及爆炸條件的關係，參數研究對象包含鋼骨鋼筋混凝土柱及鋼筋混凝土柱，爆炸條件為TNT炸藥作用在柱子底部或柱子高度1.5米處，炸藥用量為2.5公斤至25公斤。
藉由對不同參數的回歸分析提出四組分析公式可用來預測柱子軸向殘餘強度，根據所提出公式得到的柱子軸向殘餘強度可以與軸向工作載重相比較，若軸向工作載重大於軸向殘餘強度，則結構物有破壞甚至倒塌的風險。

關鍵字

LS-DYNA ； 接觸爆炸試驗 ； 鋼筋混凝土柱 ； 鋼骨鋼筋混凝土柱 ； 分析公式 ； 軸向殘餘強度

並列摘要

The risks represented by suitcase bombs are of particular concern in the modern context because they can be transported by hand and placed almost anywhere in close proximity with key structural components. Although suitcase bombs are relatively small in size, ranging from to , their effect on structural components may be severe. The most common failure mode of blast loads is progressive collapse. As such, one of the most useful information that can aid in assessing if a structure would collapse is the residual axial strength of its columns.
In this study, a high-fidelity physics based computer program, LS-DYNA is utilized to provide numerical simulations of the dynamic response and residual axial strength. There are three column specimens experimented with contact explosive tests out in the field, one being a composite steel-concrete column and the other two being reinforced concrete columns. The analytical results were compared with the test results for validation.
The strain rate effects are important to the accuracy of simulations. The dynamic increase factor is used to describe this phenomenon. The models based on these three column specimens produced similar damage profiles when subjected to blast loads as applied to the actual specimens during the blast tests conducted in the field.
An extensive parametric study utilized the validated finite element models to investigate the relationship with residual axial strength and other parameters, such as material strength, column details and blast conditions. Two types of columns were considered in the parametric study. One is the reinforced concrete column and the other is the composite steel-concrete column. TNT explosive, of weight between and , was used and located at either the bottom of columns or a height of from the footing of columns.
Four analytical formulae were derived through multivariable regression analysis in terms of various parameters to predict the residual capacity index based on the non-dimensional column dimension parameter. According to the proposed formulae, the residual capacity index can be determined and compared with service axial load index. In general, a larger value of residual capacity index indicates a greater column resistance to the blast loads. A column whose service axial load index is greater than its residual capacity index is said to have failed or collapsed. Otherwise, the column has sufficient strength for the threat considered.

並列關鍵字

LS-DYNA ； contact explosive test ； reinforced concrete column ； composite steel-concrete column ； analytical formulae ； residual capacity index

參考文獻

Bao, X., and Li, B., (2009) “Residual Strength of Blast Damaged Reinforced Concrete Columns,” International Journal of Impact Engineering. In Press.

Beshara, F. B. A., (1994a) “Modelling of Blast Loading on Aboveground Structures-I. General Phenomenology and External Blast,” Computers and Structures. Vol. 51, No. 5, pp.585-596.

Beshara, F. B. A., (1994b) “Modelling of Blast Loading on Aboveground Structures-II. Internal Blast and Ground Shock,” Computers and Structures. Vol. 51, No. 5, pp. 597-606.

Bischoff, P.H., and Perry, S.H., (1991) “Compressive Behavior of Concrete at High Strain Rates,” Materials and Structures. Vol. 24, pp. 425-450.

Gantes, C. J., and Pnevmatikos, N. G., (2004) “Elastic-Plastic Response Spectra for Exponential Blast Loading,” International Journal of Impact Engineering. Vol. 30, pp. 323-343.