Shaking Table Testing of a Full-Scale Prefabricated Three-Story Timber-Frame Building

Shake table tests were carried out on a 7 m × 5 m three-story, timber light-frame building (7.5 m height) at the TreesLab laboratory (Eucentre) in Pavia. The aim of the research was to evaluate the seismic behavior of a typical Italian prefabricated timber building and to study the interaction between the individual structural components tested in quasi-static manner in a previous experimental study. The 1979 Montenegro Earthquake ground motion, recorded at the Ulcinj-Hotel Albatros station, was selected as the ground motion for seismic tests. The maximum peak ground acceleration was scaled to 0.07 g, 0.27 g, 0.5 g. 0.7 g, and 1 g in order to evaluate the building’s performance at different levels of seismic input. More than 100 instruments were used to monitor the behavior of the building during seismic tests measuring acceleration, displacement, and forces. The visual inspection shows that the building did not show any damage during all seismic tests. However the data analysis (dynamic identification, capacity spectrum, inter-story drift) confirm that during the 1.00 g test the structure went beyond its linear elastic limit. The results obtained from this experimental study suggest that the design hypotheses commonly adopted in practice for seismic analysis (e.g., in terms of force distributions between the walls, and also the behavior factor q) are not always consistent with the real behavior of timber frame multi-story buildings, and should be backed by more accurate knowledge of the contributions of the individual structural components.     

陈列银币变色原因初步分析

为了探讨博物馆内陈列银币经常出现的表面失去光泽甚至变暗变黑的原因,采用离子色谱、X荧光光谱等方法分析变色银币清洗液成分,并对博物馆周边环境空气和颗粒物进行检测。结果表明,Cl-、NO2-、NO3-、SO42-等无机离子主要来源于环境空气,甲酸和乙酸主要来源于陈列用装饰材料。采用电子能谱、扫描电镜等分析手段对银试片表面黑色物质进行分析,发现其主要元素为碳、氧、硫,其中硫分布较深,说明黑色物质除了硫化物外还存在氧化物;进一步采用红外光谱分析发现,发黑处有明显的碳氢吸收,说明发黑银试片表面除了无机物外还存在含碳有机物,可解释扫描电镜和电子能谱中检测到碳的原因。通过模拟实验比较了空气质量、相对湿度、光源和光照等因素对银变色所起作用表明,在空气质量较差的情况下,光照强度差异几乎与银变色程度无关。在标准空气中相对湿度100%下银依旧不变色,说明在空气质量、光照度与相对湿度中,空气质量是影响银变色的主要因素。实验结果和银化合物的化学性质的结合解释了银与各种污染离子作用最终转化为稳定硫化银的原因。实验结果为制定银质文物保护环境要求和改造方案提供了依据。     

The Effect of Stiffened Floor and Roof Diaphragms on the Experimental Seismic Response of a Full-Scale Unreinforced Stone Masonry Building

An extensive experimental program was carried out at EUCENTRE, within a research project on the evaluation and reduction of the seismic vulnerability of stone masonry structures. The main part of the experimental program has been devoted to the shaking table tests on three full-scale, two-story, single-room prototype buildings made of undressed double-leaf stone masonry. The first building tested was representative of existing unreinforced stone masonry structures with flexible wooden diaphragms, without any specific anti-seismic design nor detailing. In the second and third buildings, strengthening interventions were simulated on structures theoretically identical to the first one, improving wall-to-floor and wall-to-roof connections and increasing diaphragm stiffness. In particular, in the third specimen, steel and r.c. ring beams were used to improve the diaphragm connection to the walls and collaborating r.c. slab and multi-layer plywood panels were used to stiffen floor and roof diaphragms, respectively. This article describes the strengthening interventions applied to the third building prototype and presents the experimental results obtained during the shaking table tests. The results obtained permitted the calibration of a macroelement model representative of the nonlinear behavior of the structure.     

The Peerage and the Revolution of 1688

Four points support the thesis that the English nobility played a critical role in the revolution. First, the later 17th‐century aristocracy was energetic, wealthy, and connected in ways facilitating political action within, and subsequently outside, the parliamentary arena. Second, it was a class conscious of status and privilege which many policies of James II bumped up against inadvertently, but often with negative consequence. Third, most peers were observant protestants in an age when religious belief, or at least the externals of practice, still mattered greatly. Fourth, habits of deference and traditional spheres of influence at the local level remained surprisingly intact despite intensive royal effort to reshape the lieutenancies, commissions of the peace, and municipal and other corporate bodies. Resistance to repeal of the Test Acts was the issue around which a leadership group emerged in the aristocracy. Initially it focused on a parliamentary solution in which an absolute majority in the house of lords could be counted on to stand firm no matter how the Commons might vote. In the absence of that opportunity and in the face of other events regarded as inimical to class, nation and the protestant interest, many peers turned away from natural alliance with the crown and – in the case of a forward group – conspired with the prince of Orange. Ultimately, more than a third of the nobility aligned itself with those peers intent on constraining the king's freedom of political action, an important factor contributing to his decision to flee.     

Transverse Seismic Behavior Studies of a Medium Span Cable-Stayed Bridge Model with Two Concrete Towers

Due to lack of investigation on nonlinear seismic behavior of cable-stayed bridges under strong earthquake excitation, the concrete towers, as the main gravity-carrying component, are usually required to remain nearly elastic. However, in order to achieve this high seismic performance objective, the reinforcement ratio of the tower legs and the tower struts need to be greatly increased in addition to its static loading requirement. To study the potential plastic region and possible failure mode of the cable-stayed bridge, a 1/20-scale full bridge model from a typical medium span concrete cable-stayed bridge was designed, constructed and tested on 4 linear shake tables using a site specific artificial wave in the transverse direction. Test results showed that the damage characteristics of the bridge model were as follows: (1) the severe damage was observed at the upper strut, with several steel bars fractured at both ends; (2) the repairable damage was observed at tower legs at the bottom and the middle part, with concrete cover spalling and exposure of steel bars; (3) the minimal damage was observed at the lower strut and the both sides of the side bents, with only slightly concrete spalling; and (4) no damage was observed at the auxiliary bents, the superstructure and the cables. Numerical results and test results were further compared and showed good agreement in low amplitudes of excitations. The test also proved that the bridge system was stable in flexural failure of upper struts, and had the negligible residual displacement subjected to high amplitudes of excitations.     

Cyclic Response of Non-ductile RC Frame with Steel Fibers at Beam-Column Joints and Plastic Hinge Regions

An experimental study has been conducted on a reduced-scale gravity-load designed test frame to investigate its overall performance due to the addition of steel fiber-reinforced concrete (SFRC) at the critical regions. Two geometrically similar specimens, namely, reinforced concrete (RC) and SFRC, are tested under slow-cyclic lateral loading. End-hooked steel fibers (aspect ratio = 80) of 1.0% volume fraction were used in the SFRC mix for a distance of one-and-half times the member size near the joint regions. The addition of steel fibers improved the damage tolerance, lateral load resisting capacity, lateral stiffness, ductility, and energy dissipation of the frame.     

Full-Scale Experimental Testing of Retrofitting Techniques in Portuguese “Pombalino” Traditional Timber Frame Walls

Traditional timber frame walls are constructive elements representative of different timber frame buildings, well known as efficient seismic-resistant structures. They were adopted as a seismic-resistant solution in Lisbon’s reconstruction after the 1755 earthquake. To preserve these structures, a better knowledge of their seismic behavior is important and can give indications about possible retrofitting techniques. This article provides a study on possible retrofitting techniques adopting traditional solutions (bolts and steel plates). Static cyclic tests were performed on retrofitted traditional timber frame walls. The experimental results showed the overall good seismic performance of steel plates and the more ductile behavior of bolts retrofitting.     

Seismic Performance Assessment of Non-Compliant SMRF-Reinforced Concrete Frame: Shake-Table Test Study

Seismic performance assessment is carried out for reinforced concrete structure built in low-strength concrete lacking confining ties in beam-column joint. Shake-table tests were performed on 1/3rd scaled two-story frame using design-spectrum-compatible accelerogram, scaled to various target levels. The frame is observed with beam longitudinal bar slip and pullout. Joints with no confining ties experienced extensive damage, observed with cover/core concrete spalling. The frame could resist 70% of the design ground motion to remain within the code-specified drift limit. The code requirement for minimum column depth will not avoid joint damageability in case of low-strength concrete and joints lacking confining ties.     

Development and Performance Evaluation of Disk-Type Piezoelectric Transducer for Measurement of Shear and Compression Wave Velocities in Soil

A piezoelectric transducer capable of measuring both shear and compression wave velocities in soil simultaneously in triaxial testing conditions is presented. Performance evaluation of disk transducer system showed that the use of low-noise coaxial cables, proper grounding, and high resolution wave recorder can significantly enhance signal quality and eliminates crosstalk deterioration. Distortions due to near-field effects were found to diminish by increasing input frequency and by using sinusoidal input waveform, compared to square input. Disk-type piezoelectric transducers show significant future potential for laboratory determination of shear, and compression modulus of soil because of their robustness and noninvasive nature.     

Combined In-Situ and Laboratory Minor Destructive Testing of Historical Mortars

ABSTRACT

Mortar is of all masonry components the most difficult to be experimentally characterized in heritage buildings. This article investigates the possibility of combining different in-situ and laboratory minor destructive testing (MDT) techniques to assess the strength of mortar in historical brickwork. Lime mortar and clay brick walls were built in the laboratory and then tested in order to derive empirical correlation rules among three different MDT techniques: double punch test (DPT), helix pull-out test (HPT), and pin penetration test (PPT). The outcomes of this activity were used eventually to assess the mortar properties of an important historical heritage structure, Casa Puig i Cadafalch, located near Barcelona. The research is intended to promote the use of MDT in studies and conservation works on built cultural heritage by providing criteria for the evaluation of the strength of existing mortar with respectful sampling and testing techniques.