可調鋼管支柱承載力及破壞模式之試驗研究

Experimental Study on Load Capacities and Failure Models of Tubular Steel Adjustable Shores

可調鋼管支柱模板支撐常用於結構內部挑空高度不大且樓版載重較小之鋼筋混凝土建築物。由於可調鋼管支柱具有組搭容易、運送方便等特性，雖然其承載力不大，仍廣被營造商普遍使用於建築工地。不過，由於可調鋼管支柱的結構設計資料未臻完整，致使營造工地常有倒塌意外發生。本研究主要針對可調鋼管支柱之承載力及破壞模式進行試驗探討。研究結果顯示，單根可調鋼管支柱有兩種破壞模式：支柱小於4m時，為制式插銷彎曲破壞；支柱大於4m時，失敗模式為典型之挫屈破壞，可調鋼管支柱抗壓強度隨長度遞減。三號鋼筋強度不足，不適合用以替代制式插銷。3.4m長之可調鋼管支柱配置成4、9、16、25根之結構系統，在有、無裝設水平繫條補強的試驗結果顯示，二系統總抗壓強度值，與以單根可調鋼管支柱抗壓強度乘上總根數之總抗壓強度相近。但超過3.4m長之25根無水平繫條補強之結構系統試驗抗壓強度，則比單根支柱抗壓強度乘上總根數之總抗壓強度為小。工程師於支撐結構設計時需注意。依照工地水平繫條實際組搭情況，在可調鋼管支柱3.4m長的結構系統中，對於整體抗壓強度之提升效果並不明顯；但支柱高度超過3.4m之結構系統中，整體抗壓強度可提升約20%～50%。不過，此種高度下建築物，可調鋼管支柱可考慮使用強度較高之框式鋼管鷹架或系統鷹架取代。水平繫條可抵抗施工期間施加在可調鋼管支柱的水平力，防止可調鋼管支柱的傾倒。

The falsework of tubular steel adjustable shore (TSAS) is typically adopted in reinforced concrete buildings which have a low headroom and insignificant slab loads. The TSAS is easily setup and conveniently conveyed, so contractors commonly use it in construction sites in spite of the low bearing capacity of TSAS. However, the structural design information of TSAS is insufficient. Thus, the TSAS usually collapses on construction sites. This study mainly focuses on the bearing capacities and failure models of TSAS based on experimental tests. The research result shows that the failure of TSAS has two types. The connecting tube-lock of TSAS fails when the shore length is less than four meters. The TSAS is typically buckling when the shore length is greater than four meters and the the compressive strength of TSAS reduces with the increase of the shore length. It is found that the reinforcing steel of number 3 is not appropriate for using as a connecting tube lock due to its low strength. The compressive strengths of TSAS systems of 3.4-meter height based on four, nine, sixteen, twentyfive shores with and without horizontal braces in tests were close to the compressive strength of an isolated shore times the total shore numbers. However, the compressive strength of TSAS systems of 3.4- meter height based on twenty-five shores without horizontal braces in test was less than that of an isolated shore times the total shore numbers. The engineers need to pay attention to this specific issue in shoring structural design. Based on horizontal braces setup on shoring systems on actual construction sites, the compressive strength of the TSAS system with the shore length of 3.4 meters increases insignificantly. However, the compressive strength of the TSAS system with the shore length of greater than 3.4 meters tied by horizontal braces increases about 20% ~ 50%. However, frametype scaffolds or system scaffolds are apporpriate for substituting the TSAS in the same headroom of buildings. The horizontal braces can provide the TSAS from the failure induced by the lateral forces during construction.