由於混凝土具有抗壓強度高，但抗拉強度相對低的特性(約僅有抗壓強度的1/10)，故一般鋼筋混凝土結構物於受到外力或材料的熱脹冷縮時，因而產生許多大大小小的結構性或非結構性裂縫，當鋼筋混凝土受到外力而開始發生裂縫時，亦即代表混凝土已受到損傷，甚至材料將由線彈性狀態進入非線性狀態；因此若能進一步暸解鋼筋混凝土受到裂縫影響所造成的勁度軟化現像，能有助於後續鋼筋混凝土結構物非線性分析方法的進展。
本研究將利用SAP2000有限元素法套裝軟體內建的非線性連桿彈簧(Link)元素及平面應力(Plane stress)元素，來模擬鋼筋混凝土梁，並將鋼筋及混凝土的非線性關係、裂縫、握裹與滑移等各種會影響鋼筋混凝土梁非線性行為的因素考慮進分析模型中，最後由一定的分析程序計算出鋼筋混凝土含各種裂縫狀態下之切線勁度矩陣。
經由與線彈性狀態的平面剛架勁度矩陣驗證及鋼筋混凝土梁非線性行為、分析變形圖的探討，證明本分析模式可以系統化的方法，簡單求出各種含裂縫鋼筋混凝土梁的切線勁度矩陣以用於後續整體鋼筋混凝土結構物非線性分析使用。

Concrete has high compressive strength, but relatively low tensile strength (approximately only 1/10 of its compressive strength). When it expands with heat or contracts with cold, cracks will occur. When the cracks do occur, the concrete is imperfect and it will no longer be aligned. Therefore if we are able to understand further the effects of the cracks, it will help our research greatly.
This research project will use the SAP2000 finite element method, Link and Plane stress to simulate reinforced concrete members. We will also consider concrete, steel bars, cracks, and bond slips. Finally we will calculate the reinforced concrete members based on analysis program to obtain the tangent stiffness matrix under certain kind of crack condition.
By way of the linear elastic stage, we can prove the desired results can be calculated easily.

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