火害後混凝土圍束補強之研究

Abstract

在火災頻繁的今日，建築物的火災後安全評估與結構補強變的相當重要。而國內大部分的建築物皆以鋼筋混凝土為主，因此該如何有效補強火害後的建築物為一急需解決的問題。 本研究主要目的第一為探討混凝土在遭受火害後，其殘餘強度、殘餘應變等力學性質的變化，由實驗數據迴歸一近似的關係式，並與前人所做的研究成果相比較，評估其合理與否。第二是將火害後的試體予以補強，使混凝土試體的殘餘強度能夠回復原先的強度。實驗所模擬的火害延燒時間為0.5小時、1.0小時、1.5小時、2.0小時、2.5小時、3.0小時等六段，已包括大部分的火害時間；補強方式是以一、碳纖維與玻璃纖維貼布纏繞方式，外層塗以環氧樹脂固定，等待養護時間到後，再做抗壓實驗，以瞭解複合材料的補強效果為何；二、以鋼板包覆及鋼管圍束的方式，來提高火害後混凝土的軸向應力。由抗壓的過程中，我們可以觀察複合材料補強試體與鋼管混凝土的破壞情形，並比較與純混凝土試體的破壞方式之不同。最後再找出圍束效應與試體殘餘強度的關係性，作為結構物補強的最佳參考。由實驗結果得知，(1)火害後的試體經適當補強後皆能恢復未受火害前之強度，(2)碳纖維補強對於強度回復方面優於玻璃纖維，(3)可利用試體試驗結果，應用於實尺寸構件火害分析，（4）本研究所推導之分析公式計算值與實驗結果相差無幾。

The objective of this research is to learn the concrete strengthened with the confinement after fire damage. First of all, to conclude an assumed formula from the experiments of mechanical changes of residual strength and strain after fire damage; then to prove this assumed formula by comparing it with the results from other similar researches. Secondly, to repair fired concrete cylinder to find out if the residual strength can be rejuvenated to the original strength level. There are six exposure fire durations, represented majority of fire time, and two repairing methods are used to make testing samples. One of the methods is to wrap concrete cylinders with carbon and glass fiber, then spreaded epoxy on its surface. Another method is to cover concrete cylinders with steel plate then confined it with steel tubes, that increase the axial stress of fired concrete cylinders. From an experiment of compressive strength, the researchers can monitor and compare the damage of testing samples, made as the two said methods, with regular concrete cylinders. Finally, to summarize a correlation between confined effects and concrete residual strength as a reference for repairing. There are four major discoveries from this research, first is that the strength of fired concrete cylinders can be rejuvenated to original level after proper repairing. Second is that carbon fiber is better than glass giber to restore strength of cylinders. Third is that the results of this study can be applied to full-scale fired analysis. Fourth is that the formula from this study can accurately predict the strength of full-scale column.