Browsing by Author "Jau, Wen-Chen"

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A study of reinforced concrete corner columns after fire
(2008-08-01)
Jau, Wen-Chen
;
Huang, Kuo-Li
;
土木工程學系
;
Department of Civil Engineering
This study investigated the behavior of corner columns under axial loading, biaxial bending and asymmetric fire loading. It is found that, under a longitudinal stress ratio of 0.1f'(c), the residual strength ratios of the columns after fire loading show: (a) the 2 and 4 h fire loadings result in residual strength ratios of 67% and 57%, respectively; a 10% reduction on residual strength results as the duration changes from 2 to 4 h; (b) reductions in reinforcing steel ratio cause lower residual strength ratios; and (c) increasing the thickness of concrete cover causes lower residual strength ratios. It was also found that the temperature distribution across the cross-section is not affected by concrete cover thickness and steel ratio. The residual strengths can be used for future evaluation, repair and strengthening. (C) 2007 Elsevier Ltd. All rights reserved.
Development of a modified concrete rheometer to measure the rheological behavior of conventional and self-consolidating concretes
(2010-07-01)
Jau, Wen-Chen
;
Yang, Ching-Ting
;
土木工程學系
;
Department of Civil Engineering
The modified concrete rheometer (MCR) apparatus developed in this study is based on existing concrete rheometers, the main differences being the gap size and measurement method, and thus the interpretation of the results. The gap between the inner cylinder wall and the tip of the vane was set to 6.4 times the diameter of the largest coarse aggregate in order to reduce interaction between the aggregate and the wall and the friction force from the wall. The MCR apparatus was used to measure yield torque directly at different low rotational speeds (above 0.003 rev/s). A study of the yield torque and viscosity of 37 fresh concrete mixtures was also made, with a particular focus on self-compacting concrete or self-consolidating concrete (SCC), and the results were compared with those obtained using other workability tests. The test results showed that the MCR can differentiate between conventional concrete (CC), powder-type SCC and SCC with viscosity-modifying agents (VMA). The rheological behavior of powder-type SCC was found to be influenced by the composition of Class F fly ash and ground granulated blast-furnace slag (GGBFS), and this type of concrete exhibited a wider range of viscosity and yield torque values. Despite the lower powder content and larger water to binder ratio (w/b), the viscosity of VMA-type SCC was shown to be slightly lower than that of powder-type SCC, and the values were clustered together within a certain range; thus, the workability of SCC containing VMA is more easily controlled. In addition, the MCR apparatus can also be applied to CC of differing viscosity and yield torque, thus making this apparatus suitable for determination of the workability of all kinds of fresh concrete. (C) 2010 Elsevier Ltd. All rights reserved.
鋼樑構造以不同性能基準判定耐火性能之研究
(2009)
趙文成
;
Jau, Wen-Chen
;
國立交通大學土木工程研究所
對於鋼構之耐火，以往均認為有防火被覆，可以有效保護鋼材，使其不致受到火害之影響，我國因使用鋼構高層建築逐漸增加，如101大樓，而且自東科大樓火災後我國開始對鋼構耐火開始注意，再加上美國911事件，紐約之世界貿易中心因受火害高溫而倒塌，引起國際之注。因而建研所與國際組織CIB W14合作，探討鋼結構受火害之影響，逐年編列經費，進行相關研究，提昇國內鋼構耐火性能之瞭解，並將落實於設計規範與國家標準。本研究案即屬於此一系列，主要探討在有或無載重情況下，鋼樑耐火性能之判定基準，以探討目前之國家標準是否可以正確提供相關資訊，以保障人民之生命財產安全。預期目標為： 1. 利用鋼梁承重產生較大變形影響，由實驗結果觀察比較梁承重構造採用施加載重試驗是否會降低其防火時效。 2. 建立不同被覆厚度鋼梁受彎矩作用，在高溫載重下變形行為（變形與變形速率）與鋼樑溫度之對應關係。 3. 利用分析方法模擬實驗行為，並與試驗結果比對，以修正分析方法之正確性、合理性，並可做被覆材不同厚度、不同被覆材之參數分析。 4. 本案可補充國內承重梁採試驗載重判定的試驗資料，供未來審核認可參考。採試驗載重判定方式若會影響耐火時效，將初步建議修訂CNS 12514對承重構造耐火性能判定標準應採試驗載重方式較符合實務之試驗資料（如被覆的附著性、體積穩定性、被覆裂縫與試體溫度分布之關係、試體達破壞變形規定時之溫度等資料），並持續規劃柱構件之載重試驗，補齊梁柱承重構件以不同性能基準判定耐火性能之研究成果。