高強度鋼筋混凝土圓柱與鋼梁接頭耐震行為

Abstract

本研究旨在擴大高強度鋼筋混凝土柱與鋼梁複合結構 (New RCS) 之適用範圍，期望其梁柱接頭採用圓形柱時仍具有良好之耐震性能，因此本研究將「高強度鋼筋混凝土圓柱與鋼梁接頭」作為研究對象，並採用實驗研究法，透過執行梁柱接頭試體反復載重試驗，以探討其耐震行為與發展其設計方法。其中，本研究欲驗證所研擬之梁貫穿型與圓鋼管型兩種圓柱接頭型式之設計方法，以及斜直承壓面板及柱端加勁鋼環對於梁貫穿型圓柱接頭之補強效果，同時比較梁貫穿型圓柱接頭之直通梁與銲接梁直角或斜角交會形式、長托梁不作切削或短托梁搭配續接梁翼板韌性切削之梁段設計對於New RCS圓柱接頭耐震性能之影響。 本研究依據研究目的共設計四組大尺寸New RCS圓柱內部接頭試體，其中包含：三組梁貫穿型圓柱接頭試體，接頭區使用螺箍筋，且皆配置斜直承壓面板與柱端加勁鋼環，以圍束混凝土；另一組則為圓鋼管型圓柱接頭試體，接頭區僅藉由圓形鋼管圍束混凝土，並將其延伸至上下柱端。試驗變數包含：梁貫穿型圓柱接頭之直通梁與銲接梁交會形式、托梁長度以及續接梁翼板有韌性切削與否。本研究採用固定柱軸力、推梁不推柱、梁反曲點位移控制之加載方式進行梁柱接頭試體反復載重試驗，透過分析試驗過程中測得之數據資料，以探討New RCS圓柱接頭之耐震行為。 試驗結果顯示：依本研究研擬之方法所設計之梁貫穿型圓柱接頭可有效使梁端產生塑鉸破壞，亦可驗證斜直承壓面板與柱端加勁鋼環之良好補強效果；梁貫穿型圓柱接頭之直通梁與銲接梁斜角交會可提供靠接頭柱面之梁端額外的加勁效果使塑鉸發生位置外移，並可提升其接頭區之剪力勁度；三組梁貫穿型圓柱接頭試體之反復載重行為皆符合美國鋼結構耐震設計規範AISC 341-16 (2016) 與國內鋼構造建築物鋼結構設計技術規範 (2010) 之韌性要求，圓鋼管型圓柱接頭試體之反復載重行為則無法滿足此二規範之韌性要求；由於其中三組圓柱接頭試體最終於梁構件發生非預期之脆性破壞，並未於期望位置產生塑鉸破壞，故本研究根據其破壞模式針對梁翼板韌性切削及梁續接之梁段設計提出改善建議。

This study aims to expand the scope of application of composite high-strength reinforced concrete column and steel beam structure (New RCS), and it is expected that the beam-column joints of this type of structural systems have good seismic performance when the circular columns are used. Therefore, this study took “joints between high-strength reinforced concrete circular columns and steel beams” as a research subject and adopted the experimental research to evaluate its seismic behavior and develop its design method by performing cyclic tests of beam-column joint specimens. In addition, this study was intended to verify the proposed design methods of “through-beam” and “round-steel-tube” type of New RCS joints with circular columns and strengthening effects of inclined face bearing plates and steel band rings on through-beam type joints, to compare effects of orthogonal and oblique beams welded to the through-beam on seismic behavior of through-beam type joints, and to discuss effects of long stub beam without RBS or short stub beam and link beam with RBS on seismic performance of New RCS joints with circular columns. On the basis of the research purpose, four large-scale specimens of New RCS interior joint with circular columns were designed, including: three through-beam type joints which were configured with spiral reinforcement, inclined face bearing plates, and steel band rings to confine the concrete in the joint and column-end regions; and one round-steel-tube type joint whose concrete in the joint and column-end regions was confined by a round steel tube only. The experimental variables included: angle of intersection of through-beam and welded beams, length of stub beams, and link beams with or without RBS. In order to simulate the seismic behavior of the beam-column joints, this study adopted the method of fixing the inflection points of the upper and lower columns under fixed axial force and applying cyclic loadings on the inflection points of left and right beams whose displacement control the loading process. Afterwards, this study analyzed the test data to evaluate seismic performance of New RCS joints with circular columns. The test results showed that: the through-beam type joints designed according to the proposed method could effectively cause the plastic-hinge failure at the beam ends, and the good strengthening effects of inclined face bearing plates and steel band rings on through-beam type joints were verified; the oblique intersection of through-beam and welded beams could provide additional stiffening effects for the beam ends of the through-beam type joints so that the location of plastic-hinge region would move outward from the column face, and the shear stiffness of the through-beam type joints could be improved; the cyclic behavior of the three through-beam type joint specimens satisfied the requirements of the American code “Seismic Provisions for Structural Steel Buildings” AISC 341-16 (2016) and the Taiwanese code “Design and Technique Specifications of Steel Structures for Buildings” (2010), and that of the round-steel-tube type joint specimen did not meet the requirements of the above two codes; since three of the joint specimens had unexpected brittle failure on their beam members eventually and no plastic-hinge failure occur at the desired location of their beams , this study proposed suggestions for improvement on the design of RBS and beam-splice according to their failure modes.