超高性能混凝土預鑄KT版之結構性能

Abstract

預鑄KT版作為傳統木製模板的替代工法，因其自重、運輸、吊裝等問題衍生的成本，在業界不如類似功能的鋼承鈑般常用。超高性能混凝土(Ultra-High Performance Concrete，簡稱UHPC)具有極高的力學強度，包含抗壓、抗拉強度等均是傳統混凝土的數倍之多。本研究使用UHPC作為KT版混凝土薄版的材料，欲改善KT版在工程實務上的弱勢，也就是自重問題。透過UHPC的高強度，來讓KT版在減少厚度的同時仍能保持相同的強度。 KT版在設計上分作兩部分，包含施工灌漿階段的KT版使用載重考量，以及完工後的KT合成樓版的極限強度考量。本研究針對兩階段的各檢核項目草擬強度估計公式，並各設計五組版試體進行四分點單向撓曲版加載試驗，以實驗方式驗證公式在UHPC製的KT版上的適用性。試體的操作變因包含UHPC摻入的兩種纖維種類，以及KT版混凝土薄版的厚度。 根據材料試驗，本研究證實UHPC材料在不同的纖維種類、規格以及不同的粉料配比下可能具備較大的受力行為差異，並依結果擬定KT版設計用的受拉應力應變設計曲線。根據KT版實驗結果，開裂強度、挫屈強度的估計均十分準確，但使用勁度方面，鋼纖維UHPC的試驗值較估計值低，表示公式並不保守。根據合成樓版實驗結果，極限強度的預測公式在27 mm的KT版厚試體中相當準確，但在極薄的18 mm KT版的試體則過於保守。

KT precast slabs,as an alternative method to traditional wooden formwork, have a major drawback: the cost associated with their self-weight. Ultra-High Performance Concrete (UHPC) possesses extremely high mechanical strength, including compressive and tensile strengths that are several times of traditional concrete. In this study ,UHPC is uesd as the material for KT-slab concrete board in order to improve the weakness of KT-slabs. Through the high strength of UHPC, KT-slabs can reduce their thickness while maintaining the same strength. The design of KT-slabs is divided into two parts: the service load during the grouting phase, and the ultimate strength of the composite KT floor after completion. This study drafts strength estimation formulas for various checkpoints in both phases and designs five sets of slab specimens for each phase to conduct four-point unidirectional flexural tests. These tests experimentally verify the applicability of the formulas on UHPC KT-slabs. The operational variables of the specimens include two types of fibers mixed into the UHPC and the thickness of the KT-slab concrete boards. According to material tests, this study confirms that UHPC materials may exhibit significant differences in mechanical behavior depending on the type of fibers or different powder mixtures. Based on the results, a tensile stress-strain design curve for KT-slab is formulated. According to the KT-slab experiment results, the estimations of cracking strength and buckling strength are quite accurate, but the experimental values of stiffness of the steel fiber UHPC specimen is lower than estimated values, indicating that the formulas are not conservative. According to the composite floor experiment results, the ultimate strength prediction formulas are quite accurate for the 27 mm thick KT-slab specimens, but overly conservative for the extremely thin 18 mm KT-slab specimens.