中華民國內政部建築研究所中華民國內政部建築研究所

一、研究緣起
火災與地震多年來一直是建築物損壞與破壞的主要原因，近年來，內政部建築研究所已針對鋼筋混凝土造建築與鋼構造建築之構件與構架有系統地進行火害實驗與研究，並已獲致豐碩成果，然而，國內外研究尚缺少建築物火害後之殘餘耐震性能評估研究，亦未建立有系統之評估流程來解決此一重要課題。因此，為了正確評估火害後建築物之耐震能力，以為日後建築物火害後之耐震補強提供正確資訊，故應先進行火害後建築物之結構耐震性能評估的研究，以提供建築物耐火與耐震設計實務之參考。
貴所針對鋼筋混凝土造及鋼構造建築物，規劃以三年時間進行火害後建築物之結構耐震性能評估研究，以實際瞭解火害後建築物之耐震能力，其研究內容包括：柱構件火害後之反覆載重實驗、單層單跨構架屋火害後之振動台實驗、以及電腦數值模擬分析，透過本研究發展建築物火害後之振動台實驗技術方法與流程，並建立有系統的火害後建築物之結構耐震性能評估方法。
本研究為三年期研究之第三年，規劃於內政部建築研究所防火實驗中心進行高強度鋼筋混凝土柱構件與鋼構造構架屋試體之火害實驗，並結合國家地震中心台南實驗室進行火害後建築物構件之反覆載重實驗與火害後構架屋之振動台實驗，研究火災及地震之多重性災害對建築物之影響。
二、研究方法及過程
本研究將針對火害後之高強度鋼筋混凝土柱構件與鋼構造構架屋，以實驗測試方法研究其殘餘耐震能力。本研究團隊將使用本三年期研究之第一年度【135】製作完成之2座單層單跨鋼構造構架屋，分別進行火害與未火害鋼構造構架屋之振動台實驗，以評估火害後鋼構造構架屋的殘餘耐震能力。其中，未火害之鋼構造構架屋試體屬控制組試體，另一座鋼構造構架屋則先於內政部建築研究所防火實驗中心戶外場地進行火害實驗，模擬鋼構造構架屋在火場中可能受到的溫度變化，完成後再運至鄰近的國家地震中心台南實驗室，進行振動台實驗。本研究亦將製作4支高強度鋼筋混凝土柱試體，試體控制變因包含混凝土強度與有無火害，並於國家地震中心台南實驗室之反力牆進行反覆載重實驗，以評估高強度鋼筋混凝土柱火害後之殘餘耐震能力。另外，將針對本三年期研究之第二年度【134】研究火害與震害後之一般強度鋼筋混凝土柱構件，研究修復工法對於提升其耐震能力的有效性。基於前述實驗成果，本研究亦將比較分析建築物構造火害後之不同補強技術與相關工法，並研擬建築物火害後耐震能力評估流程。
三、重要發現
本研究進行混凝土抗壓強度350與700 kgf/cm2之鋼筋混凝土柱，受CNS 12514-1火害2小時後之反覆載重實驗，結果發現其側向強度分別下降7.6與13%；有效勁度分別下降48與55%。
本研究完成建立高強度鋼筋混凝土柱之OpenSees數值模型，並驗證其配合Eurocode 2之500°C等溫線法於標準火害2小時後之殘餘強度評估，其中，本研究建議鋼筋滑移之斷面剛度折減係數為0.55，並提供本研究試體標準火害2小時之斷面等溫線分布圖供評估者配合Eurocode 2查詢相關折減係數。
本研究實驗證實可利用無收縮水泥砂漿及8 mm鋼板包覆工法，恢復且超過原柱至少1.2倍強度、1.3倍側向勁度，展現良好修復性能。
本研究選用國震中心107-108年之七層樓RC振動台實驗案例，透過本計畫前2年之單柱與振動台實驗驗證，建議商用軟體之修正分析模式，可協助業界有效進行鋼筋混凝土建築結構火害及地震後之耐震評估工作，合理掌握未火害、火害後、修復後之結構受震行為。
本研究蒐集國內外火害後補強技術及相關工法，包括混凝土、鋼板、或纖維貼片包覆，及鋼托架等。如考慮使用空間、耐震性能及修復時間，建議以鋼板包覆為主。
根據鋼構實驗屋之振動台實驗結果顯示，火害後鋼構實驗屋於受震前系統識別之自然週期為0.381秒，較未火害鋼構實驗屋於受震前系統識別之自然週期0.354秒延長7.37%，說明鋼結構建築物受到火害高溫後，其鋼材變軟的現象，使得楊氏係數E和強度(F_y  & F_u)有所折減，導致其整體結構之側向勁度受到高溫影響而下降，因而造成鋼結構建築物之自然週期延長。
火害後鋼構實驗屋於各地震波作用後之樓板殘餘位移皆大於未火害鋼構實驗屋之樓板殘餘位移，說明鋼結構建築物受到火害後，其鋼材之降伏強度受到高溫作用影響而下降，相較未火害之鋼結構建築物於受震後產生較大塑性變形。
由於現行相關法令規定尚未有針對火害後鋼構造建築之耐震能力評估要求，本研究參酌英國Maraveas等人研究，提出鋼構造建築火害評估流程草案(含耐震能力)，並建議火害後鋼構造建築之相關火損指標納入未來研究方向。
四、主要建議事項
建議一
建議研擬建築結構火害後殘留耐震能力評估手冊：立即可行建議
主辦機關：內政部建築研究所
協辦機關：內政部營建署、國家地震工程研究中心
火災與地震為建築結構損壞及倒塌主要原因，造成構件之承載力及韌性折減，進而影響結構物之安全性及耐久性。國內外歷年來已累積豐碩之相關研究成果，包含內政部建築研究所近3年之建築物火害後耐震性能研究，藉由實驗驗證，定性與定量化構件與建築物於火害後殘留耐震能力、提供混凝土與鋼筋材料性質受火害之分析所需折減係數、發展火害後結構分析模型，可合理評估構件火害後之耐震性能、並完成構造物火害後耐震性能評估流程。然為健全國內災防體系，並擴大建築物安全檢測之實施，本研究團隊建議研擬建築結構火害後殘留耐震能力評估手冊，訂定火害後建築物火損指標、現場檢查評估表及詳細評估流程等，以供相關主管機關、建築師與技師有所依循。
建議二
火害後修復與耐震能力補強之技術研究：中長期建議
主辦機關：內政部建築研究所
協辦機關：內政部營建署、國家地震工程研究中心
透過本研究可以發現火害對於建築結構之耐震性能有所影響，然而真實火場情況多變，火災延時增加與房屋老舊等皆能造成建築物更嚴重之損毀，因此本研究團隊建議可透過國內外文獻之蒐集彙整或以實驗方式進行修復與補強之有效性評估，將有限資源投入在修復與補強材料及技術之研發。

1.Research Background
Fires and earthquakes have been the main causes of damage and destruction of buildings, the Architecture and Building Research Institute of the Ministry of the Interior has systematically carried out fire damage experiments and research on the members and frames of reinforced concrete buildings and steel buildings in recent years. However, there is still a lack of research on residual seismic performance evaluation of buildings after fire damage at home and abroad, and no systematic evaluation process has been established to solve this important issue. Therefore, in order to correctly evaluate the seismic performance of buildings after fire damage and provide correct information for the seismic reinforcement of buildings after fire damage in the future, it is necessary to conduct research on the structural seismic performance evaluation of buildings after fire damage, so as to provide a reference for building fire resistance and seismic design practice.
For reinforced concrete and steel structure buildings, the Architecture and Building Research Institute of the Ministry of the Interior planned to conduct a three-year study on the structural seismic performance evaluation of buildings after fire damage, so as to actually understand the seismic performance of buildings after fire damage. The three-year study contents include cyclic loading tests of column members after fire damage, shaking table tests of single-story and single-span steel frame after fire damage, and computer numerical simulation analysis. Through these research, the technical methods and procedures of the shaking table test for buildings after fire damage are developed, and a systematic evaluation method for the structural seismic performance of buildings after fire damage is established.
This study is the third year of the three-year study, which is planned to conduct fire test on high-strength reinforced concrete column members and steel frame specimens at the Fire Experiment Center of the Architecture and Building Research Institute of the Ministry of the Interior, and is combined with the Tainan Laboratory of the National Center for Research on Earthquake Engineering to do the cyclic loading tests of building members after fire damage and the shaking table tests of structural frame after fire damage in order to study the impact of multiple disasters of fire and earthquake on buildings.
2.Research Method
In this study, the residual seismic capacity of high-strength reinforced concrete column members and steel frame after fire damage will be studied by experimental test methods. The research team will use the two single-storey, single-span steel frame completed in the first year of this three-year study to conduct shaking table tests on fire-damaged and non-fired steel-frame to evaluate the residual seismic capacity of steel frame after fire damage. Among them, the non-fired steel frame specimen is the control group, and the other steel frame was subjected to fire test at the outdoor site of the Fire Experiment Center of the Architecture and Building Research Institute of the Ministry of the Interior in order to simulate the temperature changes that the steel frame may be subjected to in the fire field, and it was transported to the adjacent Tainan Laboratory of the National Center for Research on Earthquake Engineering for shaking table tests. 4 high-strength reinforced concrete column specimens will also be fabricated in this study, which has the controlled variables of concrete compressive strength and whether to carry out the fire test or not. And the column specimens was also transported to the adjacent Tainan Laboratory of the National Center for Research on Earthquake Engineering for cyclic loading tests in order to evaluate the residual seismic capacity of high-strength reinforced concrete columns after fire damage. In addition, for the general strength reinforced concrete column members after both fire and earthquake damages in the second year of this three-year study, the effectiveness of the retrofitting methods in improving their seismic capacity will be studied. Based on the above-mentioned experimental results, this study will also compare and analyze different retrofitting methods and related construction methods for buildings after fire damage, and develop a process for evaluating the seismic capacity of buildings after fire damage.
3.Main Finding
In this study, the reinforced concrete columns with concrete design compressive strength of 350 and 700 kgf/cm2 were subjected to cyclic loading tests after 2-hr fire exposure test according to CNS 12514-1. The results showed that the lateral strength are decreased by 7.6 and 13%, respectively, and the effective stiffness are decreased by 48 and 55%, respectively.
This study completed the establishment of the OpenSees numerical model of high-strength reinforced concrete columns, and verified the evaluation of its residual strength after 2-hr standard fire exposure with the 500°C isotherm method of Eurocode 2. The reduction coefficient of the section rigidity is suggested by 0.55 and the isotherm distribution of the section of the specimens after 2-hr fire exposure in this study are provided, which provides the evalutors to obtain the reduction factors from Eurocode 2.
This study verified that using non-shrinkage cement mortar with 8 mm steel plate wrapping method to retrofit can restore and exceed the original column at least 1.2 times the lateral strength and 1.3 times the lateral stiffness, showing good repair performance.
This study selects the case of shaking table test for the seven-story RC building conducted by National Center for Research on Earthquake Engineering in 2018 to 2019. Through the verification of the cyclic loading test for single-column and shaking table tests for frame in the first 2 years of this project, it is suggested that the modified analysis model of commercial software can be used to assist the industry to effectively evaluate the seicmic performance of reinforced concrete structure after fire. 
This study reviewed the post-fire retrofitting methods and related construction methods at home and abroad, including concrete, steel plate, or fiber patch wrapping, and steel brackets. Considering the use of space, seismic performance and retrofitting time, it is recommended to use steel plates wrapping to retrofit.
According to the shaking table test results of the steel frame specimens, the natural periods of the steel frame specimens before and after the fire were identified by the system as 0.381 and 0.354 seconds respectively, which increases 7.37%, meaning that after the steel frame was subjected to fire and high temperature, the steel became soft, which reduces the Young's modulus E and strength (F_y  & F_u), resulting in a decrease in the lateral stiffness of the overall structure, as a result, the natural periods of steel frame specimens were prolonged.
After the fire damage, the residual displacement of the floor slab of the steel frame after each seismic excitation is greater than that of the unfired steel frame, which indicates that the yield strength of the steel frame is affected by the high temperature during fire exposure. However, compared with the unfired steel frame, it would have larger plastic deformation after the earthquake.
Since the current regulations do not have the guideline for the evaluation of the residual seismic performance of steel structure buildings after fire damege, the research team refers to and modifies the research of Maraveas et al. in the UK, and proposes a draft of the evaluation of the residual seismic performance of steel structure buildings after fire damage, and suggests that the relevant fire damage indicators of steel structure buildings after fire damage can be included in the future research.
4.Suggestion
Suggestion 1
Proposal to develop the manual for the evaluation of residual seismic performance of building structures after fire damage.
Organizer: Architecture and Building Research Institute of the Ministry of the Interior.
Co-organizer: The National Architects Association of R.O.C.(Taiwan), National Center for Research on Earthquake Engineering. 
Fires and earthquakes are the main reasons for the damage and collapse of building structures, resulting in the reduction of the bearing capacity and ductility of structural members, which affects the safety and durability of structures. Over the years, there have been abundant relevant research results at home and abroad, including the research on the seismic performance of buildings after fire damage by the Architecture and Building Research Institute of the Ministry of the Interior in the past three years. Through experimental verification, the residual seismic performance of buildings and structural members after fire damage were qualified and quantified, which provides the reduction factors required for the numecical analysis of the properties of steel and concrete materials, and develops the post-fire numecical models, which reasonably evaluate the seismic performance of structural members after fire damage, and complete the evaluation process of seismic performance of structures after fire damage. However, in order to improve the domestic disaster prevention system and expand the implementation of building safety inspections, the research team proposes to develop a manual for the evaluation of residual seismic performance of building structures after fire damage, and to establish fire damage indicators for building structures after fire damage and to provide the details of the evaluation process for relevant authorities, architects and technicians to follow.
Suggestion 2
Study on restoration and retrofitting methods for buildings after fire damage: mid and long-term suggestion.
Organizer: Architecture and Building Research Institute of the Ministry of the Interior.
Co-organizer: The National Architects Association of R.O.C.(Taiwan), National Center for Research on Earthquake Engineering. 
Through this study, we can find out the degree of fire damage on the building structure. However, the real fire scene is variable, and problems such as increased fire duration and old houses can cause more serious damage to the building. Therefore, the research team suggests that the limited resources can be invested in the research and development of repair and retrofitting methods through the collection and compilation of domestic and foreign literature or the evaluation of the effectiveness of reinforcement through experiments.