高強度鋼筋混凝土柱耐震圍束效應之研究

Design of Seismic Confinement of RC Columns Using High Strength Materials

陳盈璋(Ying-Chang Chen)

指導教授 ： 黃世建

國立臺灣大學/工學院/土木工程學研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.03403

摘要

將高強度混凝土(High-Sthength Concrete, HSC)配合高強度鋼筋(High-Strength Steel, HSS)應用在高樓層RC建築的柱構件上有許多好處，包括增加軸向承載能力及側向勁度，有利縮減助構件的斷面尺寸，增進室內可使用空間；並可減少建築物重量，降低地震力。但HSC相較NSC更為脆性的材料性質，往往侷限了其應用在耐震結構上的可能性。
實際上，若對柱的核心提供足夠的圍束力，HSC的韌性行為將有明顯的改善，而此圍束力與柱的橫向箍筋量及其配置型式有很大的關係；此外，國內的混凝土工程設計規範同ACI 318-05規範般，其建議之圍束箍筋量對於承受高軸壓的柱構件明顯不足，因此尋求一套適用於HSC的圍束箍筋量公式，成了目前將高強度材料推廣於工程實務上迫切的議題。
本研究針對高強度材料設計了8座柱構件，於國家地震工程研究中心(NCREE)之MATS (Muti Axial Testing System)系統進行高軸壓下之反覆側推試驗，使用的高強度材料有降伏強度685 MPa之主筋、785 MPa之箍筋，及混凝土設計抗壓強度70、100 MPa，分為傳統橫箍與多螺箍兩種箍筋型式，參考了加拿大規範(CSA A23.3-04)及Elwood et al.建議的設計公式決定測試時施加的軸力大小。
測試的結果顯示：較高強度混凝土之柱構件其變形能力不如較低強度者；此外，90°彎鉤對於束制柱主筋的效果不及135°以上之耐震彎鉤；並且本試驗再次驗證了，軸向載重大小確實會影響柱圍束箍筋的需求。
最後，本研究針對試驗結果，分別對橫箍柱及螺箍柱提出了一套建議的設計公式，並以現有的資料進行檢核。驗證的結果顯示，此建議公式能合理的應用在高強度材料及高軸力作用下的柱構件上，並確保其有好的變形能力。

關鍵字

柱 ； 圍束 ； 高強度混凝土 ； 高強度鋼筋 ； 高軸力 ； 五螺箍 ； 設計公式

並列摘要

The use of high-strength concrete (HSC) and high-strength steel (HSS) in column elements of high-rise RC building has many benefits, such as increasing the axial load capacity and lateral stiffness, reducing the size of the component’s cross-section; enhancing interior space; and reducing the weight of the building as well as the seismic design force. However, HSC is essentially more brittle than the normal strength concrete (NSC), which limits its application in earthquake-resistant structures.
In fact, if the core of the column is provided with sufficient confinement, the ductility of HSC will be significantly improved, and this confining effect is greatly influenced by the amount of transverse stirrup and its configuration. Currently, the domestic building design code follows the American ACI Code. However, the amount of confinement stirrups required by these codes is clearly insufficient for the column elements subjected high axial load capacity under earthquake. Therefore, defining a suitable confinement design equation for HSC columns now becomes an urgent issues.
In this study, 8 column specimens with high-strength materials were designed and tested under axial load combining with cyclic loading on the MATS (Muti-Axial Testing System) in NCREE. The use of high-strength material includes the longitudinal reinforcement with yield strength of 685 MPa, the hoops with yield strength of 785MPa and concrete design compressive strength of 70 and 100 MPa. The specimens are divided into two groups based on the confinement type: the traditional tied columns and multiple spiral columns. The amount of axial force applied is refered to the Canadian Code (CSA A23.3-04) and Elwood et al’s design recommendation.

Test results showed that the columns with high-strength concrete have lower deformation capacity than the low-strength ones. In addition, 90 degree hooks have less confining effect than seismic hooks. It was also shown that the magnitude of the applied axial load indeed affects the demand of confinement.
Finally, this study proposes a new confinement design equation for both tied columns and spiral columns based on the test observations. Applicability of the proposed equations to the NSC columns is also checked with the available experimental data. Test results of these study show that the proposed equations can be reasonably applied to the columns with high-strength materials and columns under high axial load, and ensure them to have good deformability.

並列關鍵字

column ； confinement ； high-strength concrete ； high-strength reinforcement ； high axial load ； multiple spiral ； design equation

參考文獻

[7] 張豐展，「高強度鋼筋混凝土柱圍束效應研究」，碩士論文，國立台灣大學土木工程學系，台北，民國99年。

[6] ACI Committee 318, “Building Code Requirement for Structural Concrete (ACI 318-08) and Commentary (ACI 318R-08),” American Concrete Institute, Farmington Hills, Mich., 2008.

[13] Paultre, P.; and Légeron, F., “Confinement Reinforcement Design for Reinforced Concrete Columns,” Journal of Structural Engineering, ASCE, V. 134, No. 5, 2008, pp. 738-749.

[14] 郭美婷，「五螺箍矩形RC柱之軸壓試驗與優化研究」，碩士論文，國立交通大學土木工程學系，新竹，民國97年。

[16] Sheikh, S. A.; and Bayrak, O., “High-Strength Concrete Columns under Simulated Earthquake Loading,” ACI Structural Journal, V. 94, Nov.-Dec. 1997, pp. 708-722.