Experimental Study on Low-Cycle Fatigue Performance of Weld-Free Buckling-Restrained Braces

A type of weld-free buckling-restrained brace is proposed to eliminate the influence of welding on the low-cycle fatigue performance. The core member is manufactured with no weld existing along the overall length of the member. Three welded and three weld-free specimens under different strain amplitudes were tested, and the hysteretic behavior and low-cycle fatigue performance of the specimens were analyzed. The test results indicate that the ductility and the cumulative plastic deformation of the weld-free specimens are much higher than that of the welded ones, which are much closer to the performance of the material capacity.     

Development and Seismic Behavior of Precast Concrete Beam-to-Column Connections

A new precast concrete beam-to-column connection for moment-resisting frames was developed in this study. Both longitudinal bar anchoring and lap splicing were used to achieve beam reinforcement continuity. Three full-scale beam-to-column connections, including a reference monolithic specimen, were investigated under reversal cyclic loading. The difference between the two precast specimens was the consideration of additional lap-splicing bars in the calculation of moment-resisting strength. Seismic performance was evaluated based on hysteretic behavior, strength, ductility, stiffness, and energy dissipation. The plastic hinge length of the specimens is also discussed. The results show that the proposed precast system performs satisfactorily under reversal cyclic loading compared with the monolithic specimen, and the additional lap-splicing bars can be included in the strength calculation using the plane cross-section assumption. Furthermore, the plastic hinge length of the proposed precast beam-to-column connection can be estimated using the models for monolithic specimens.     

Reliability-based Strength Amplification Factors for Structures with Asymmetric Yielding

A reliability-based methodology to estimate strength amplification factors for structures with asymmetric yielding is proposed. The approach is based on structural demand hazard analyses. Nonlinear time-history analyses of tridimensional simplified systems are carried out. The effects of two orthogonal components of the seismic ground motions and soil-structure interaction, are considered. Results show that the expected ductility demand of systems with asymmetric yielding may be much higher than those of symmetric systems. A simplified mathematical expression (which is function of the ratio between the fundamental vibration period of the system and that of the soil, ductility demand, and level of asymmetric yielding) is proposed to estimate the amplification factors. The expression is applied successfully to a 9-story reinforced concrete building exhibiting asymmetric yielding produced by tilting.     

Accuracy evaluation of the semi-automatic 3D modeling for historical building information models

It is stated that 3D recording and modeling of heritage buildings entail accurate building models (as-built). However, this paper presents an analysis of the 3D modeling accuracy for the creation of historical building information models (HBIM), considering the complexity and the deformations of historical buildings, using point cloud data and BIM tools. The 3D modeling processes analyzed are based on a three-stage semi-automatic approach leading to the generation of HBIM, including manual and automatic processes. The three stages consist of: (a) optical and terrestrial laser scanning; (b) meshing processes; and finally (c) 3D solid modeling to be assembled into HBIM. Next, this approach analyzed the mesh deformations generated automatically in comparison to the initial point cloud data. The deformations and the accuracy evaluation have been undertaken using different commercial software. Finally, our modeling approach shows that it can improve the accuracy of the 3D models achieved using existing BIM technologies.     

Continuity Amidst Change: Village Organization and Fishing Subsistence at the Dionisio Point Locality in Coastal Southern British Columbia

Shifts over time in faunal representation in Northwest Coast archaeological sites have been viewed as reflecting changes in economic organization and social complexity. We use fish faunal data from the Parry Lagoon Midden (site DgRv-006) in the Salish Sea region of coastal southwestern British Columbia, Canada, to evaluate the relationship between change in subsistence strategies and community organization. We describe and compare fish assemblages recovered from a shell midden generated by habitation at two sequentially occupied village sites. The lower midden layers include faunal remains derived from the Marpole Period plankhouse village occupation at site DgRv-003 (1500 to 1300 cal BP), while the upper layers were generated during the occupation of a Late Period plankhouse within site DgRv-006 (1000 to 600 cal BP). We compare the two faunal records to ascertain if subsistence re-organization accompanied the social change associated with abandonment and later re-establishment of a village in the Dionisio Point Locality. Results indicate continuity of a diverse fishing economy for the two occupations, and therefore across the Marpole to Late Period transition. This study adds to the recent trend in Northwest Coast archaeology to reconsider the long-standing view that social and subsistence change necessarily occurred in tandem.     

Experimental Study on the Seismic Performance of Superimposed RC Shear Walls with Enhanced Horizontal Joints

The seismic performance of superimposed reinforced concrete (RC) shear walls is decreased by rocking behavior and damage concentration at the horizontal joint. An enhanced horizontal joint method is proposed to improve the corresponding seismic performance. To validate the reliability of the proposed method, three full-scale superimposed walls and a cast-in-place shear wall (for comparison) are designed and tested under the quasi-static load. The test results indicate that the rocking phenomenon can be prevented using the proposed method, and the seismic performance of superimposed RC shear walls with enhanced horizontal joints is comparable to that of the cast-in-place RC shear walls.     

Strength Hierarchy at Reinforced Concrete Beam-Column Joints and Global Capacity

Strength hierarchy assessment is a method that can be utilized to identify the weakest structural element at a reinforced concrete (RC) beam-column joint. The method was extensively used in various research activities at the University of Canterbury, which mainly involved beam-column joint subassembly tests. However, this method required improvements and refinements in order to be adopted in multi-story building applications. In this paper, the improvements made to the method are reported. In the improved method, capacity of the weakest element at every beam-column joint in an RC frame building can be related to the corresponding global base shear demand. The method has been illustrated via two example applications: an RC frame lacking joint shear reinforcement and a modern RC frame with adequate joint shear reinforcement. The case study examples confirmed the accuracy and the effectiveness of the method.     

南方潮湿地区壁画表面加固与裂隙灌浆材料的评价研究

为弥补我国南方潮湿地区壁画保护材料研究的欠缺,模拟南方气候条件对壁画表面加固和裂隙灌浆材料进行保护效果的评价研究。通过前期预实验以及表面光泽度、防水性、耐老化性等测试评价得到:质量分数1.5%的RS1930纯丙乳液具有较好的表面加固效果;传统石灰中添加占石灰质量3.0%左右的ZB-SE-3A纯丙乳液和2.0%左右的纳米材料配制而成的灌浆材料具有较好的强度、防霉性、防水性与耐老化性,适合作为潮湿地区壁画灌浆加固材料。     

Invited response to K. Ryan’s comments on Coltrain et al. (2004) and Coltrain (2009): is Native Point “Burial 21” Dorset in age; were historic-era burials European in origin and how important were caribou in Sadlermiut diets?

This is an invited to response to K. Ryan’s comments on Coltrain et al. (2004) and Coltrain (2009). Both publications present stable isotope data and AMS radiocarbon dates on a suite of eastern Arctic burials from three sites in north-western Hudson Bay. In these articles, we examined the importance of bowhead whaling among Thule foragers at Silimiut and Kamarvik and contrasted their subsistence strategies with those of the proto-historic Sadlermiut, using the stable and radio-isotope chemistry of purified bone collagen to monitor variability in resource acquisition over time. Ryan dismisses a Dorset-era radiocarbon date on a burial collected by Collins from the T-1 site asserting that a single radiocarbon measurement is not a reliable indicator of age and thus the burial is Sadlermiut not Dorset. She also contests our assessment that two historic-era individuals in the Sadlermiut mortuary assemblage were either European or consumed diets relatively high in European foods. Ryan further argues that our reconstruction of protohistoric Sadlermiut diets is not in keeping with the archaeofaunal record. Her primary concern is a perceived lack of agreement between a subset of our findings and the archaeological record.     

I never shall be a white man again: race and junior officers in the Mexican War

Throughout the Mexican War, the impact of professionalization was felt on the battlefields of Mexico. This professionalism did not, and could not insulate these officers from social issues such as race. When American junior officers viewed the filthy conditions in Mexico, they argued that these conditions could only be explained by the racial inferiority of the Mexican people as a race. Volunteers and regulars reacted to these issues in exactly the same manner. This fact challenged the traditional fears that a professional standing army would become disconnected with the society they protected, and would thus become despotic. Similarly, the excesses of the volunteers demonstrated that they were not the paragon of virtue which many in the US hoped.