Abstract: This paper presents the results of an experimental study on the compressive stress-strain relationship of wood confined with fiber composite sheets. Wood cylinders confined with carbon fiber composite sheets along full length were tested by compression load. The tests considered up to three layers of fiber sheets. The results will be used to verify a numerical analysis model, which will be further used to conduct a parametric study of the influential factors. The generated knowledge can be used as reference for strengthening designs of historical timber structures using fiber reinforcing products.
Abstract: Surveying and mapping the appearance of architecture plane is a supporting technology of historic buildings. To meet the need of plan survey in-house, a new close-range photogrammetry method was developed by laser reticule system. With the help of the system, two parallel level lines and eight vertical laser lines can be marked on the surface of inner walls. When the relationship between the distance from a vertical line and the length of the same line on an image picture is studied, the spatial location of room corners and some characteristic points on the images can be determined. Based on the photogrammetry and plane table operation method, architectural plane mapping can be done easily following a set of laser reticule images which were shot in situ closed by a non-metric digital camera. More details of historic buildings can be recorded on drawing sheets and images monogamy at the same time by using the proposed method, which are the basic information for the structural analysis of historic buildings.
Abstract: A group of buildings in West China Campus-Sichuan University (The Atherton Building for Biology and preventive Medicine, The Lamont Library and Harvard-Yenching Museum, and The Whiting Memorial Administration Building) featured both in Chinese and Western styles were built by five western churches together in 1910, under the name of “Private West China United University”. To protect the buildings, the authors tested the strength of materials taken from the buildings and inspected the buildings in site to evaluate the structure of the historical constructions. The authors suggested protective measures which were adopted in the rehabilitation to the buildings and evaluated the repair effect by the method of Field Vibration Test. Through the test, inspection, analysis and evaluation of the buildings, lots of information data of historical constructions have been accumulated.
Abstract: Important historic buildings may be subjected to accidental loads during their service life. It is therefore necessary not only to evaluate their safety under traditional loads and seismic action (only in earthquake area), but also to evaluate the structural performance of resisting progressive collapse. For historic buildings, two aspects make them different from the modern buildings: the material properties are usually deteriorated to some extent, and the structural system/constructions may not meet the requirements of current design and construction codes. Considering such aspects, a method consisting of four steps to evaluate the performance of the historic buildings to resist progressive collapse is presented in this paper. Firstly, the building layout should be evaluated whether it can protect the occupants from the possible explosion. Secondly, geometrical information, structural constructions and the material properties are to be investigated in details. Thirdly, by means of tie force method and the alternate path method the performance of the structure is analyzed to resist progressive collapse. The load combinations used in the analysis are derived based on the expected service life of the structure. The failure criteria for the structural elements as well as the damage limits for the structure follow the provisions addressed in American Unified Facilities Criteria “Design of Structure to Resist Progressive Collapse” (UFC 4-023-03). Finally, based on the above information an overall evaluation is made for the probably structural retrofitting and strengthening. This method is illustrated with a case study of a steel frame historic building, namely the Bund 18 building, in Shanghai, China. Some suggestions for retrofitting and strengthening this building are also presented.
Abstract: Four steel beam-column connections were tested under cyclic loads to investigate effects of the concrete cover and the cast-in-situ slabs on the failure modes, stiffness, load-carrying capacity, ductility and energy-dissipation capacity. The test results show that the stiffness and bending strength of the non-rigid steel connections are significantly increased due to the presence of concrete cover and the cast-in-situ slabs can further enhance the connections. Moreover, the connection with slab is prone to debonding failure along beam-slab interface resulting in a remarkable decrease of the stiffness and strength. Practical methods are also presented for analyzing and assessing the steel frames with non-rigid connections considering effects of concrete cover.
Abstract: The surface of cultural heritage and façade of historic buildings represent most values. The conservation of such surfaces need special cares, because most of them are non-structural exposed to extreme weather conditions. The refitting and consolidation delaminated surface were carried out using organic resins, like epoxy resins or cement suspension. However the evaluation in the recent years show such kinds of materials are not chemically compatible with historical materials. Based on inspection on cracks of Huashan’s Pictographs and other historic buildings in Shanghai and Hangzhou, a new system composed of adhesives and injection grouts based on natural hydraulic lime (NHL) has been developed for refitting and rehabilitation of delaminated surfaces made of natural stones, plaster and bricks. The laboratory researches and trial areas on site have shown the adhesives based on modified NHL have sufficient bonding strength to hold delaminated stone slices and blocks. Furthermore, they show slow setting and carbonation process, almost same heat expansion coefficient as the lime stone and inorganic historical materials. After exposure of 135days on site, the trial areas show neither cracking nor efflorescence. The application of developed adhesives and injection grouts in the restoration work of historic Shanghai plaster gates of Jiuxinli in Hangzhou, Zhejinag Province, has been observed positively. Because of high performance and competitive price against organic resins, they are expected to be an optimal material system in the future for façade restoration of architectural heritage and monuments.
Abstract: In order to increase the strengthening efficiency of steel bar mat-mortar (BM) jacket and wire mesh-mortar (WM) jacket around existed circular concrete columns, an attempt to strengthen the columns with hybrid bar mat-wire mesh-mortar (HBWM) jacket was proposed. A comparatively experimental study on axial compression behaviors of concrete columns wrapped with three different strengthening systems, namely BM, HWBM and carbon fiber reinforced polymer (CFRP) was performed. The experiment results showed that much more cracks appeared in HWBM columns compared with those in BM columns. As a result, on the premise that the concrete compressive strength of the HWBM columns increased 90% compared with that of the BM columns, the ductility of the HWBM columns reached about twice as that of the BM columns. The increase of the concrete compressive strength of CFRP strengthened columns was higher than those of HWBM and BM strengthened columns. The ductility of CFRP strengthened columns, however, was obviously lower than that of HWBW columns.
Abstract: Laboratory experiments were conducted to protect and consolidate historic architectural heritages by bacterially induced carbonate mineralization on the surface of samples of marble and concrete. Some properties of samples and mineral, such as the composition and growth of the mineral deposited on samples, porosity or pore size distribution of samples, the efficiency of protection, the bond behavior between the deposited mineral and substratum, were analyzed by X-ray diffraction, scanning electron microscopy, mercury intrusion porosimetry and ultrasonic test. The results show that the phases of mineral crystal are calcite and vaterite, and the calcium source has an effect on the phase of calcium carbonate mineralization and precipitation. Bacteria act as nucleation sites in the course of precipitation of the mineral crystallization, and the crystal is deposited uniformly on the surface and subsurface of the matrix. The precipitation has no significant effect on the pore size distribution of the matrix, but results in a decrease of porosity, and mineral crystals are strongly attached to the substratum. Bacterial mineralization for remediation of historic buildings can be an ecological and novel alternative to traditional techniques.
Abstract: In this paper, limit state criteria for safety evaluation of historical buildings according to different target period of usage were introduced briefly. The effect of beam-column connection and the contribution of bricks surrounded columns and infill masonry walls on the seismic behavior of the historical buildings were identified based on calculation results. Main features of performance-based seismic evaluation method, including classification of importance of historical buildings, determination of target period of usage and performance index, were discussed. An engineering project was discussed to illustrate the evaluation procedures, and verify the effectiveness of the evaluation method.
Abstract: In system based seismic strengthening design, the redistribution of inner forces brought by the change of structural members can be considered, which is very important to guarantee the safety of a strengthened structure. Using SAP2000, the seismic behavior of a historic building was analyzed. After that, a system based seismic strengthening plan and a member based seismic strengthening plan were proposed. And the seismic behaviors of the building before and after strengthening were compared. The results show that the seismic behavior of the building can be improved with the system based seismic strengthening and the style and the feature of the building can be protected well.